THE JOURNAL FOR SURFACE WATER QUALITY PROFESSIONALS · 2020. 1. 20. · aged. After all, the SWPPP...

Trends in Monitoring

THE JOURNAL FOR SURFACE WATER QUALITY PROFESSIONALS

November/December 2013 | www.stormh2o.com

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TABLE OF CONTENTS

November/December 2013www.stormh2o.com

EDITORJanice Kaspersen - [email protected]

PRODUCTION EDITORSBrianna BenishekWilliam Warner

IT / ONLINE SUPPORTChris Pratt

WEBSITE EDITORNadia English - [email protected]

DIRECTOR OF ONLINE MEDIA & ITJeffrey Pascone

GROUP EDITORJohn Trotti - [email protected]

SENIOR ACCOUNT EXECUTIVESMark GerstenGeoff Solo Michelle Maple

ACCOUNT EXECUTIVESEileen DuarteDon WeimerShane StevensGlenys Archer

SALES & MARKETING COORDINATORCarmody Cutter

ADVERTISING SALES MANAGERRon Guilbault - [email protected]

SENIOR DESIGNERDeja Hsu

PRODUCTION TECHNICIANDavid Naj

PRODUCTION MANAGERDoug Mlyn

ART DIRECTORJudith Geiger

DIRECTOR OF CIRCULATIONSteven Wayner - [email protected]

MARKETING COORDINATOR, EDUCATION & TRAININGAmber McEldowney - [email protected]

PROGRAM MANAGER, EDUCATION & TRAININGJane Schuster - [email protected]

DIRECTOR OF EDUCATION & TRAININGBeth Tompkins - [email protected]

CONFERENCE SALES & MARKETINGBrigette Burich - [email protected]

CONFERENCE DIRECTORScott Nania - [email protected]

ACCOUNTANT /CHAIR, LOVE & HAPPINESS COMMITTEECourtney Keele

AR / APKeith Rodgers

FINANCE & HR MANAGERJohn Pasini - [email protected]

OFFICE ADMINISTRATORKathy Martin

PUBLISHERDaniel Waldman - [email protected]

Departments6 Editor’s Comments

8 Guest Editorial

44 Project Profi le: Achieving Silver at Brown Hall 48 ShowCase

53 Spotlight

54 Project Profi le: Comparing Paver Performance at the University of Minnesota

57 Marketplace

57 Advertiser’s Index

58 Reader Profi le

FEATURES

Cover photo: Matthew SullivanCOVER STORY 10 Trends in Stormwater MonitoringBy Carol Brzozowski

22 Atlanta’s Green InvestmentLeveraging grant money to manage stormwater, curb flooding, and reduce CSOsBy Margaret Buranen

30 Resilience: Communities Connect the Dots to Dodge DisasterBy David C. Richardson

36 The Principles of Gravity SeparationPart 2. Laminar settling, swirl concentration, and flotationBy Gary R. Minton

Stormwater November/December 2013 | Volume 14, Number 8

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STORMWATER (ISSN 1531-0574) is published eight times annually (bimonthly with an extra issue in May and October) by Forester Media Inc., 2946 De La Vina Street, Santa Barbara, CA 93105, 805-682-1300, fax: 805-682-0200, e-mail: [email protected], website: www.forester.net. Periodical postage paid at Santa Barbara, CA, and additional mailing offices. All rights reserved. No part of this publication may be reproduced in any form without written permission from the publisher. Entire contents ©2013 by Forester Media Inc. POSTMASTER: Please send address changes to Stormwater, 440 Quadrangle Drive Ste E, Bolingbrook, IL 60440. Changes of address can be completed online at www.stormh20.com/subscribe or mailed to 440 Quadrangle Drive Ste E, Bolingbrook, IL 60440; please provide your mailing label or old address in addition to new address; include zip code or postal code. Allow two months for change.

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6

Roger BannermanEnvironmental SpecialistWisconsin Department of Natural ResourcesMadison, WI

Laureen M. BolesOffice of Watersheds

Philadelphia, PA

Dave Briglio, P.E.Senior Water Resources Engineer

EA Engineering, Science & Technology Inc.

Hunt Valley, MD

Dirk S.G. Brown, J.D. Regulatory Compliance Advisor

Department of Public Utilities

City of Columbus, OH

Patrick S. Collins, P.E.Engineering Department Director/

City Engineer

Valdosta, GA

Thomas R. Decker, P.E., M.S.C.E.Director of Water Resources

Jacobs Engineering Group Inc.

Morristown, NJ

Gordon England, P.E.Applied Sciences Consulting Inc.

Cocoa Beach, FL

Bruce K. Ferguson, FASLAProfessor & Director, School of

Environmental Design University of Georgia

Athens, GA

Jerry Hancock, CFMStormwater and Floodplain Programs

Coordinator

City of Ann Arbor, MI

Masoud Kayhanian, Ph.D.Dept. of Civil and Environmental Engineering

University of California

Davis, CA

Brant D. Keller, Ph.D.Director of Public Works and Utilities

Griffin, GA

G. Fred Lee, Ph.D., P.E., B.C.E.E., F.ASCEPresident, G. Fred Lee & Associates

El Macero, CA

Gary R. Minton, Ph.D., P.E.Stormwater Consultant

Seattle, WA

Betty Rushton, Ph.D.Environmental Scientist

Gainesville, FL

Elizabeth TreadwaySenior Consultant

AMEC Earth & Environmental

Greensboro, NC

EDITORIAL ADVISORY BOARD

By Janice Kaspersen

EDITOR’S COMMENTS


It’s no secret that plastic litter in lakes and oceans is a growing problem. Ocean currents cause it to accumu-late in certain areas; the Great Pacifi c Garbage Patch is now about the size

of Texas, and we’re adding an estimated 20 million tons of plastic to our waters every year. Last year, researchers at the University of Delaware showed that the oceans contain more plastic—up to two and a half times more—than we previously thought, because it not only fl oats on the surface but also is abundant at depths of 20 meters or more, where we hadn’t previously measured.

Plastic doesn’t biodegrade, but instead breaks down into smaller and smaller pieces, which are more easily ingested by birds, fi sh, and other marine life—entering the human food chain as well. Studies from the Scripps Institu-tion of Oceanography and from NOAA have shown that between 9% and 12% of ocean fi sh have ingested plastic, and that percentage can be much higher for some species.

Part of the problem is trash: items made from plastic and Styrofoam are discarded and end up in the waterways. From a storm-water management perspective, we can do something about these, intercepting the debris in catch basin inserts or larger trash-capturing devices. But the plastics come from other sources as well; for example, the small plastic pellets, or “nurdles,” used in the manufacture of plastic goods are sometimes mishandled or improperly disposed of, escaping from factories, trucks, and railroad cars. Even more insidiously, it now appears tiny plastic beads used in personal care prod-ucts like exfl oliants are not being captured by sewage treatment plants and are making their way to surface waters.

Two recent publications highlight the problems plastic litter causes, and more importantly they offer specifi c suggestions

for how to deal with it. One is a report titled “Stemming the Tide of Plastic Marine Litter: A Global Action Agenda” from the UCLA School of Law’s Emmett Center on Climate Change and the Environment and UCLA’s Institute of the Environment and Sustain-ability. It contains several ambitious recom-mendations, such as an international treaty for monitoring plastic debris, local bans on the most common and dangerous types of plastic litter, placing more long-term respon-sibility on the producers of plastic products, and an “ocean friendly” certifi cation program for those products.

The other report has a bit narrower focus, but also offers a solution

in which ordinary consum-ers can take part. The 5 Gyres Institute, a nonprofi t group dedicated studying and solving the plastics-in-the-ocean problem, has published research

on “micro-plastics,” or tiny grains of polyethylene and

polypropylene, that are found in high concentrations in the

Great Lakes and elsewhere; personal care and beauty products are apparently a major source. Several companies—Procter & Gamble, Johnson & Johnson, The Body Shop, Colgate-Palmolive, and Unilever—have agreed to phase out the use of these micro-beads in their products. 5 Gyres, in partnership with similar organizations, has also developed an international mobile app that allows consumers to scan barcodes of personal care and beauty products to see whether they contain micro-beads, as well as whether the manufacturer has agreed to phase them out.

An increasing number of cities have enacted bans on plastic bags, and trash TMDLs are becoming more common, but source-reduction efforts like this one still seem to be rare. Is plastic a focus of your stormwater program, or are you aware of other types of efforts to control it?

One Word: Plastics

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8 November/December 2013www.stormh2o.com

Where is your SWPPP? Is it acces-sible to anyone who wants to view it? Does it

contain the current permit or proper certifications? Is your SWPPP being properly amended and updated when you perform required ongoing inspections?

These are questions that construction professionals and MS4s are presently considering as a growing emphasis is placed on water quality and enforce-ment in our communities nationwide. A SWPPP, or stormwater pollution pre-vention plan, is required by the federal Clean Water Act on most construction sites, including industrial facili-ties, that have exposures to rain or snowmelt. Federal, state, and local regulations are very specifi c when it comes to how these plans must be properly man-aged. After all, the SWPPP document itself is the “court document,” derived from self-monitoring documentation that is required by their complicated regulations. As these regulations grow more complex, companies and MS4s are trying to solve how to best meet them to stay compliant and to avoid negative publicity and costly fi nes and penalties that are on the rise.

What is the best way to legally manage SWPPPs on projects and facilities?

While many environmental regu-lations can seem burdensome, the regulations also allow some common-sense methods for achieving compli-ance. One such method is allowing electronic management of all storm-

water documents, inspections, map updating, and communication. And it appears that the federal government is ready to require states and local municipalities to manage their SWPPP oversight programs electronically. This would encourage anyone wanting to comply to utilize technology. Storm-water personnel have been trying to fi gure out the best way to manage

SWPPP documents onsite for updat-ing and accessibility for quite some time. Mailboxes, lockboxes, and other methods have been used to try and meet the regulations. However, as you can imagine, the documents are often lost, vandalized, stolen, misman-aged, weathered, and ultimately not compliant. Company management personnel and MS4s struggle when emphasizing the need for continual upkeep and management of SWPPPs. This is especially true if the only way to manage them is to actually drive to the sites and fi nd them.

Electronic management provides a better way to manage a SWPPP

program and make it compliant. As long as the electronic accessibility of the SWPPP and documents are posted with the permit, the SWPPP is always accessible. This includes current, up-to-date certifi cations, inspections, action logs, amendments, and active site maps. The benefi ts of electronic management are obvious. Electronic management will change

your operational process. Hard copies of the SWPPP, inspections, signatures, and action logs, along with map updating onsite, are a thing of the past. Elec-tronic inspections, signa-tures, action logs, and map updating are an improved management method allowing professionals to use better tools for compli-ance, increasing profi tability, providing more fl exibility, and driving improved compliance. Company and MS4 interests are better protected with electronic management as well. It is one thing to say, “These things are important”; but where SWPPP manage-

ment is tied to a consistent electronic process with tools and resources, compliance documents will fi nally be compliant, and everyone wins if that is the case.

Ryan Dickson is a partner with complianceGO, a cloud-based system to assist with stormwater compliance monitoring and tracking.

Online SWPPP ManagementBY RYAN DICKSON

For related articles: www.stormh2o.com/regulatory-issues

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BY CAROL BRZOZOWSKI

Today’s trends in storm-water monitoring and sampling are focusing on research as well as how to better manage stormwater

onsite, industry observers say. Meeting National Pollutant Discharge Elimina-tion System (NPDES) permit require-ments continues to be a focus of many stormwater monitoring efforts. Instru-ment manufacturers are rolling out

integrated systems designed to help end users achieve their many goals.

Monitoring in PortlandIn Portland, OR, the Bureau of Envi-ronmental Services engages in many stormwater monitoring programs, including those for industrial customers that discharge to the treatment plant, as well as surface water monitoring for compliance with NPDES permits.

“We used to do quite a bit of performance evaluations of stormwa-ter BMPs, but we moved away from that recently and are now doing more investigations,” says Matt Sullivan, environmental specialist.

One such investigation centers on a Superfund site created 10 years ago, where the Bureau of Environmental Services is doing source tracing.

“We also do biological monitor-

Trends in Stormwater Monitoring

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11November/December 2013 www.stormh2o.com

ing of the streams and water bodies throughout the city of Portland,” adds Sullivan.

The overall focus of the stormwater monitoring is getting inputs for a con-tamination loading evaluation model for the Columbia Slough, which is one of the more contaminated water bod-ies in the city of Portland, he says. The Columbia Slough is 12 miles long and a very slow-moving water body.

“Water takes up to a week to exit from the system,” says Sullivan. “Even though we’re pretty far inland, it’s still highly affected. Because it’s a slow-moving water body, a lot of sediment stays within the system.”

Portland has used In-Situ’s Troll 9500 equipment to collect data at a few different points within the Columbia Slough. “Over the course of time, we collected enough data to be able to get a good model of the water quality in the slough,” says Sullivan. “We have a good grasp of the whole system, and now we’re focusing our attention on individual stormwater

outfalls that the city owns.”Bureau staff has seen contamina-

tion in the sediment.“We’re trying to see if the current

stormwater is clean enough that the associated sediment will cover over and provide natural attenuation of the contaminated sediment and provide a layer of cleaner sediment on top of it, or if it’s still actively contributing con-taminants of concern,” says Sullivan.

Portland does continuous monitor-ing. “We try to capture over the course of an entire storm or as much of a storm as we can,” he says. The staff visits the site to retrieve the data.

Additionally, the bureau has a sedi-ment trap installed inside a stormwater line to continuously capture sediment over an entire wet season. It is hooked up to fl ow meters; positive fl ows trig-ger the trap to start collecting samples.

The city also has an in-house lab. “At the conclusion of a storm event, we’ll go out there, retrieve the data off the fl ow meter, pull the samples, and then submit them to our laboratory,”

says Sullivan.PCBs are one of the main con-

stituents for which the Bureau staff is looking; metals are another.

“We’ve been having trouble achiev-ing detection limits,” says Sullivan of the PCBs. “The detection limits are so low that we’ve had to be innovative in our sample collection to be able to achieve those detection limits. We’ve done modifi ed approaches to look at really low levels to achieve that.”

Sullivan says he fi nds the low detec-tion limits the most interesting part of the stormwater monitoring project.

“We did a lot of high-volume sam-pling as well, where we would pump a large amount of water and fi lter it to retain the solid components in order to achieve the low detection limits, and then with that calculate the actual concentration in the water,” he says. “PCB levels are too low to be seen in a water sample, but if we can extract the sediment from the stormwater with the lab analytical methods, we can detect in the sediment that’s left


behind and then calculate the concen-tration in the stormwater.”

The program has been in effect for two years.

“We did a lot of sediment coring to look at the sedimentation rate of the receiving water of the Columbia Slough and went through several approaches until we ended up with some equipment that would work,” says Sullivan. “The sediment is really fi ne material, and some of the coring approaches we had tried to use didn’t work initially, so we had to refi ne those techniques.”

The Troll 9500 is one of many stormwater sampling and monitoring tools offered by In-Situ. The portable water quality instrument is a “set and forget” system used for groundwater and surface water monitoring and houses up to nine water quality sen-sors, internal power, and optional data logging capabilities.

Jon Firooz, vice president with In-Situ, says the top issues his com-pany hears about from its customers is a lack of time and cost and budget restrictions.

“Additionally, they also have to deal with human resources, so there’s a lot of turnover that takes place,” he says. “Every time you have a new person on staff, you have to deal with training and getting them up to speed, making sure they’re doing things properly.”

He says users also are concerned about regulatory requirements. “They also require fl exibility because they never know exactly what monitoring is going to be needed at any given site, so they want fl exibility in terms of the types of equipment they use,” points out Firooz.

In-Situ approaches those problems from a perspective of both technology and service. The company recently released its smarTroll Multiparameter (MP) Handheld, combining water-quality sensors with smartphone mobility. The intuitive In-Situ applica-tion runs on an iPhone, iPod Touch, or iPad device.

The smarTroll MP Handheld is connected to a battery pack, the In-Situ applica-tion is launched, and

immediate results are produced. The In-Situ application guides its user through spot checks, calibrations, and data management. The device mea-sures up to 14 parameters. Chemical parameters include dissolved oxygen (DO), pH, oxygen-reduction potential (ORP), conductivity (actual or specifi c), salinity, total dissolved solids, resistiv-ity, and density. Physical parameters include air and water temperature, barometric pressure, water level, and water pressure.

“It can be used for spot-checking or profi ling,” says Firooz, adding it requires no training. “We’ve also designed it to take advantage of a lot of features that are native to smart-phone platforms. For instance, you can

tag GPS locations for a site to make it easy to come back and confi rm that you are in the right location. One of the best features is the ability to e-mail this instantly back to colleagues or others on your team.”

All work can be done from the fi eld. Links are provided to an online store for those who need to order a new calibration solution.

End users also fi nd the company’s Rugged Dissolved Oxygen Pro Probe helpful, Firooz says, adding that it is approved by EPA for Clean Water Act monitoring requirements.

When the probe initiates a read-ing, an LED emits blue light, exciting lumiphore molecules in the sensing element. Excited lumiphore molecules

PCBs and metals are among the

pollutants of concern.


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emit red light, which is detected by a photodiode. Oxygen molecules quench the excited lumiphore molecules and prevent the emission of red light through the “dynamic luminescence quenching” process. Determination of DO concentration by luminescence quenching has a linear response over a range of concentrations.

The technology was designed to be more durable and maintenance free than some of the legacy electro-chemical technologies, helping “signifi cantly” in handling some of the abrasion and the harshness of the environments with which those who monitor stormwater deal on a regular basis. EPA approval allows use without the need for special regulatory approval or alternative test procedure clearance, Firooz says.

The desire for fl exibility is

addressed in many of the company’s products, including the relatively new multiparameter Aqua Troll 400, which offers support for standard open protocols so that end users can connect the instrument with differ-ent loggers or automated sampling

systems on the market. “We have a number of customers

who will connect our instruments to a Campbell Scientifi c data logger or a Teledyne Isco automated sampling system,” says Firooz, adding that users appreciate the fl exibility.

The need for real-time data access is another trend noted by In-Situ.

In response, the company has pro-vided telemetry solutions that enable customers to use a cellular network or a satellite telemetry system in extremely remote areas. The solutions are designed for customers who want to get data any time, eliminating the

need for labor costs associated with grab samples and other manual data retrieval techniques.

“Budgets are being squeezed; the biggest costs tend to be labor,” says Firooz. “If we can reduce the number

of trips they have to take, that can give end users a lot more time at staying within their budget constraints.”

Comparing Farming TechniquesAt The Ohio State University, researchers are engaged in a multidis-ciplinary project that combines physi-cal science data collection to study

“If we can reduce the number of trips they have to take, that can help end users stay within their budget constraints.”


water quality and social science survey work. The study focuses on the dif-ferences in farming practices between Amish and non-Amish farmers.

“We’re doing a comparison of the water quality to support the work that the social scientists are doing at the sites,” says Deana Hudgins, a research associate. “We’re looking at farming practices and how decisions are made, as well as water quality, because these areas are heavily farmed.”

The comparisons are within the East Branch–South Fork Sugar Creek watershed in north central Ohio, one of the most polluted watersheds in the state from nonpoint-source pollution.

East Branch Sugar Creek is the non-Amish site; the South Fork Sugar Creek is the Amish site. Both are part of the Sugar Creek watershed, which is part of the Muskingum River watershed.

“In the Amish watershed, their prac-tices are different. They’re not using mechanized systems. They often are farming smaller areas. They do a lot of

seeding by hand,” says Hudgins. “The comparison was driven much more by the social science aspect rather than the water sampling aspect.”

Amish farmers are doing what many mainstream, non-Amish farms are doing, she adds.

“They are using similar crops. You

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see GMO [genetically modifi ed crops] on occasion; it depends on whether it’s approved in their church district. You see fertilizers, pesticides. There is manure application in both water-sheds. There is a large dairy in the non-Amish watershed that is down-stream of where the sample site is located. Some farmers in both water-sheds are doing organic farming. It’s a mixture in the area,” says Hudgins.

Most watersheds in the area tend to look very similar, she says.

“They are very fl at areas with very eroded stream banks, a lot of straight-ening of streams,” says Hudgins.

The instrumentation was installed in late spring 2013. Researchers are using two SonTek-IQ Plus fl ow meters with standard mounts and Teledyne Isco 24-bottle samplers.

The SonTek-IQ is designed with a custom fl ow algorithm. Four velocity beams profi le water velocity in 3D vertically and horizontally. A built-in pressure sensor and vertical acoustic beam operate in tandem to measure water level.

The Isco bottle samplers col-lect 1-liter samples every 24 hours. Researchers take those samples back to a lab for analyses for phosphorous, nitrate, ammonia, total nitrogen, and total phosphorous.

The research team is doing con-

tinuous fl ow monitoring as well. “The Isco is gathering approximately 250 millili-ters every eight hours. We collect the samples every two and a half to three weeks and do the analyses on those. They are acid-fi xed samples; the unit is not refrigerated. We have ongoing remote access to our fl ow data.”

The research team also has alarms set up for the rare fl ooding situation.

“There are very deep channels from drawdown in erosion, but we are able to set up alarm systems

because it’s roughly an hour away from where any of us lives. If we did have a fl ooding situation, we’d need a lot of notice to be able to pull equipment in a timely manner,” says Hudgins. “We have it set up so we can get the data anywhere we have an Internet connection.”

Data are collected every 15 min-utes. A rising water level triggers the fl ow monitor to collect data every min-ute, with a set threshold of 3 feet.

The next step in the project will be for researchers to submit the fi ndings to a hydrologist affi liated with the National Research Institute in Agricul-ture in France—a counterpart to the United States Department of Agricul-ture—who will analyze the data and collaborate with social scientists.

Xylem and its many brands—which includes SonTek/YSI—offers a range of instrumentation that focuses on water quality and quantity, notes the com-pany’s Chris Heyer. He says Xylem is noticing more concerns within the industry about what is contained in stormwater.

“They want to know when there is a storm event how is it increasing turbidity levels, total suspended solids, and nutrient loading into whatever the subsequent waterways are beyond the stream, the river, the pond—whatever they might be monitoring,” he says.

Monitoring for sediment and contaminants in Portland

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“We are seeing a large growing trend around increased loadings to waterways and what the impacts of those load-ings are in terms of low-dissolved oxygen and potential fi sh kill—any number of things.”

That ties into both urban and agricultural environments, although the components those monitoring stormwater are monitoring are vastly different, Heyer says.

The company offers sensors that focus on basic ambient water-quality parameters such as temperature, conductivity, turbidity, pH levels, and DO. Instruments for water quan-tity measure both standard water level as well as velocity.

Integrated Systems and Solutions is a full custom solu-tions division offering options for stormwater monitoring.

One multi-parameter water-quality instrument is typi-cally used alongside a rain gauge and has an autosampler for water samples, says Heyer.

“The autosampler will draw a water sample from the stream, river, or stormwater drain and store it in different compartments of the sampler,” he says. “Some of the sam-ples might be 24 samples over a 24-hour period. Those are often event-triggered either by fl ow or by rainfall and can be picked up later by a technician.”

Telemetry also is incorporated into the system, allowing technicians to see in real time that an event occurred as well as the ambient water-quality parameters, rainfall, water level, or water fl ow for that event.

End users receive notifi cation that their sampler is actively triggering it so they can retrieve the water samples for further analysis in a laboratory for such factors as total suspended solids.

Xylem’s brand companies build solutions such as a turnkey system with solar power, which might include an EXO water-quality multiparameter sonde, a rain gauge sensor, an autosampler, telemetry, a water level sensor, and a water veloc-ity sensor, Heyer says. The YSI EXO system is designed to offer calibration and redeploy in the time span of a typical sample interval; it features wireless commu-nications, onboard diagnostics, cop-per alloy parts, and anti-fouling wipers.

YSI also pro-vides fl ood alert monitoring to the industry through standard system and custom-built systems. These systems include components that

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monitor water levels, log precipitation, calculate water discharge, and transmit information.

Studying TemperatureRepresentatives from St. Anthony Falls Laboratory at the University of Minnesota have conducted fi eld studies for the Minnesota Pollution Control Agency to collect the data necessary to support the formulation and validation of a temperature simulation model for urban stormwater deten-tion ponds.

Researchers indicate that although the hydrology of stormwater detention ponds “is fairly well understood, many water-quality effects are presently unquantifi able, under investigation, or unknown.”

In May 2011, the University of Minnesota prepared a report for the Minnesota Pollution Control Agency (MPCA), authored by Michael P. Weiss, William R. Herb, and Heinz G. Stefan of the St. Anthony Falls Laboratory, regarding the stormwater detention pond water temperature data collection and interpretation. The researchers indicated the purpose of the data collection effort was to determine the impact wet detention ponds have on runoff water tempera-ture, especially if the outfl ow drains into a cold, class A trout stream.

The data were used to develop and to validate a model for predicting outfl ow temperature and to offer recom-mendations for the reduction of stormwater pond outfl ow temperatures.

Detailed fi eld data were collected on 17 ponds in the metropolitan area. The study was considered important because there are several cold-water trout streams in the periphery of the Minneapolis/St. Paul metropolitan area and in the city of Duluth.

Researchers also collected additional data to document salinity profi les in stormwater detention ponds in connection with the use of road salt in the Twin Cities area.

Land use was important in the fi eld study. Researchers sought a stormwater detention pond in an industrial or commercial devel-opment or resi-dential area with high percentage of impervious area.

Other desirable pond attributes included ponds used in previous studies, unshaded

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pond surfaces, one inlet as opposed to multiple inlets, a single outlet, a pond sur-face area of 1 to 5 acres, a continually fl ooded wet pond with an open water area 3 to 10 feet deep, no deterioration or silt, and a drainage area easy to determine.

The urban stormwater detention pond simulation model is included in the MINUHET (MINnesota Urban Heat Expert Tool) model that computes runoff temperatures for typical resi-dential and commercial watersheds, simulating single rainfall events or continuous periods of several months.

The simulated runoff temperatures and volumes are used to estimate the heat loading from urban surface runoff to cold-water streams. To support the simulations, weather data and urban runoff temperature data were col-lected to serve as model inputs and to validate model outputs.

In 2005 and 2006, researchers studied a pond for detailed instru-mentation and data collection on the former site of the State Farm Insur-ance Company Headquarters, near I-94 and Radio Drive in Woodbury, MN. The manmade wet pond featured an outfl ow structure and one major storm sewer infl ow from two parking lots and the roof. Its surface area is 1.32 acres. Its drainage collection area

of 43.5 acres is 52% impervi-ous. It is nearly completely unshaded. The permanent pool depth is 2.4 meters.

The installed instrumenta-tion measured and recorded weather data, temperature stratifi cation data in the pond, surface infl ow and outfl ow data, pavement temperature, and pavement runoff tem-perature data during and after rainfall events. The instru-

mentation in the pond was operated from June 3 to August 25, 2005.

The pond has a clay liner to prevent water loss by infi ltration. An outlet structure stops the outfl ow from the pond when the maximum pond water depth has dropped to about 2.43 meters. When it is not overfl ow-ing, the pond’s surface area is about 1.2 acres.

Surface water infl ow is from the

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former State Farm Insurance Company offi ce complex, including an upper and lower asphalt parking lot.

A weather station comprising an anemometer, a wind direction vane, and a tipping bucket rain gauge was placed in the middle of the pond. A thermistor chain consisting of six temperature sensors attached to the pole and a pressure sensor was placed below the water surface to record pond water level. All instruments were connected to a Campbell Scientifi c data logger CR-10 that was attached to the pole above the water.

The weather parameters and the water temperatures in the pond were measured every minute, with averages recorded on the Campbell data logger every 10 minutes. Water temperatures were measured with YSI Model 55032 thermistors with a time constant of about 10 seconds.

Wind speed was measured by an R.M. Young model 03001 anemom-eter and wind direction instrument. Water level was measured with an

Instrumentation Northwest model 9805 pressure sensor.

Onset Hobo temperature loggers were used to record water tempera-tures in Celsius at one-minute intervals at the pond inlet and outlet structures and at one minute initially, then two-minute intervals at two storm-water catchments in the parking lots. Onset Hobo miniloggers were used to replace loggers of another manufac-turer that had an upper recording limit less than what Onset could provide.

Two additional temperature log-gers were buried in the surface of the asphalt parking lot to record pave-ment temperature in Celsius at two-minute intervals initially, and then fi ve-minute intervals.

Water transparency in the pond was measured manually using a Secchi disk.

The report indicates that a numeri-cal simulation model was developed to simulate the hydraulic and heat trans-fer properties of a stormwater deten-tion pond. The model is dynamic and

based on basic principles of hydraulics and heat transfer, driven by hourly climate and weather data.

At the former State Farm site, the pond model fi eld data were calibrated and validated. The relationship between pond infl ow and outfl ow rates to precipitation was effec-tively calibrated using continuously recorded pond level.

Algorithms developed for surface heat transfer in lakes were found to be applicable to the pond with some modifi cation, according to the report. A signifi cant diurnal thermal stratifi -cation was simulated and measured in the pond. Temperature differences from top to bottom were as high as 13°C (55°F) during daytime hours.

The outfl owing water temperature was essentially equal to the pond sur-face temperature because the outlet was located near the pond surface, researchers pointed out. Outfl ow water temperatures were calculated with a RMSE of 1.40°C (55.40°F). Water clarity had little effect on the

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pond outfl ow temperatures; however, the pond bottom temperature was found to be highly sensitive to water clarity.

Researchers concluded that for pond designs with outlet structures that take subsurface water, water clarity will intro-duce uncertainty to simulations of the pond temperature profi le and the pond outlet temperature.

Onset’s data loggers are primarily used in research for those trying to develop new ways of managing storm-water, notes the company’s Paul Gan-nett. “I’m hearing of a lot of efforts going on relative to handling the stormwater at the site better rather than just having it run off and dealing with it somewhere else,” he says.

Green roofs are a prime example. “You have a green roof that absorbs the water, allows it to dissipate through evapotranspiration or maybe collects it for use somewhere, so

the result is less runoff,” says Gan-nett. Permeable pavement is another example.

Data loggers are used to measure the amount of rainfall.

“The areas being studied are the amount of rain falling onto the roof and into the parking lots,” Gannett says. “The data loggers monitor

that rainfall—not just the amount of rainfall, but when it fell and how it behaves is sometimes part of the study. You want that time record of the rainfall. On the other side, you

want to mea-sure how much water runs off from that.”

There are three ways to measure it, Gannett says.

One is through runoff gauges, which can be rainfall gauges in them-

selves. “A lot of times, they’ll take the runoff, run it through a rain gauge or some sort of runoff gauge using rain gauges and event loggers,” he says. One of the most used tools for that purpose is the HOBO Data Logging Rain Gauge-RG3. The rain gauge records up to 160 inches of rainfall at rates up to 5 inches per hour. The battery-powered system includes a HOBO Pendant Event data logger with a tipping-bucket rain gauge to collect rainfall, time, and duration data as well as temperature when used with an optional solar radiation shield. A base station or shuttle is required.

Another technique uses water-level loggers that are deployed in collection tanks that collect the rainwater for another use or until it can dissipate into the ground. The water loggers deal with quantity information—the amount of rainfall coming in and the fl ow out of the system or collected within the system. The 13-foot HOBO Water Level Data Logger is used to monitor water levels and tem-peratures in wells, streams, lakes, and wetlands. For saltwater use such as brackish wetlands and tidal areas, the HOBO U20 Water Level Titanium is used. The system features lightning protection. HOBOware Pro software provides conversion to accurate water level reading, fully compensated for barometric pressure, temperature, and water density. Multiple-rate sampling allows faster sampling at critical times such as when pumping starts or stops.

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“You have a green roof that absorbs the water, allows it to dissipate through evapotranspiration, or

maybe collects it for use somewhere, so the result is less runoff.”


A third common technique is examining stormwater inundation from storm surges along coastal areas. Case in point: Hurricane Sandy. Examining the inundation helps in mapping out rebuilding strategies.

“There are areas where you shouldn’t rebuild at all, areas where you can rebuild but you should plan on inundation for this amount of time, or build on stilts—those kind of strategies,” points out Gannett. “There are a lot of deployments of water-level loggers in those coastal areas by organizations like the US Geological Survey.”

For green roofs, the U30 remote monitoring systems are especially important because they can monitor incoming rainfall and accept a range of sensors, says Gannett.

“They’ll accept soil moisture, which is important for a lot of these stud-ies. You want to monitor how much water is being absorbed into the soil and available for plants, because it’s important for the plant’s health to

have the right amount of soil mois-ture,” he adds.

In some cases, it’s used to manage irrigation systems on the green roofs, says Gannett. “Sometimes you get too much rain, and there are other times when you’re not getting enough rain. You need to do some sort of irrigation to keep a healthy, well-functioning green roof to keep those plants alive up there,” he points out. “Sometimes there’s a lot of experimentation with collecting the rainwater on the rooftop and using that to irrigate the rooftop during periods of low rainfall. Or in some cases, they’ll just have an irriga-tion system that’s tied into the water supply that can be used to irrigate the roof in times of low rainfall.”

In the past year, Onset has started to bundle its existing products that had been available for the U30 remote monitoring system to make it more convenient to put together a system for an application such as a green roof, Gannett says.

The U30 remote monitoring sys-

tem is a web-enabled system that can tie into a building’s WiFi; users can post the data from the green roof on the Internet.

“That’s very popular because a lot of the green roofs have a double bene-fi t,” says Gannett. “You’re reducing the amount of runoff. Also, a lot of compa-nies want to show how they’re taking steps to be more green. When you can publish that information, show that on a website and provide some real tangible data, it sets a positive corpo-rate message for what they’re doing to be green, reduce runoff, and create a better environment.”

Carol Brzozowski specializes in topics related to stormwater and technology.

For related articles: www.stormh2o.com/water-quality-monitoring


BY MARGARET BURANEN

Leveraging grant money to manage stormwater, curb fl ooding, and reduce CSOs

Two developments guarantee that Atlanta, GA, will see more examples of green infrastruc-ture. The first push comes from Atlanta’s share of a $950 million grant from EPA to encourage green infrastructure in 17 cities.

Priority was given to areas of heavy fl ooding, in neigh-borhoods with combined sewer systems. Six pilot green infrastructure projects have been completed in Peoplestown (site of frequent combined sewer overfl ows, or CSOs),

Mechanicsville, and Summerhill.These short-term green measures were fi nished by the

summer of 2012 to give residents some immediate relief from fl ooded, contaminated basements and backyards. More longer-term green projects are in the pipeline.

The second stimulus for green infrastructure happened in February 2013, when the Atlanta City Council approved changes to the city’s stormwater ordinance. These changes affect stormwater management on both residential and

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commercial properties.In most cases, property owners or developers are

required to explain their plans for stormwater manage-ment in meetings with the Site Development Staff in the Department of Watershed Management (DWM). The focus is on infi ltrating the fi rst inch of runoff onsite via green infrastructure.

New commercial projects that add impervious surface or disturb more than 1 acre of land are now governed by this law. So are commercial redevelopment projects that add or replace more than 500 square feet of impervious surface or disturb the same amount of land.

Builders of new homes on individual lots must manage the fi rst inch of runoff onsite through green infrastructure. However, they are not required to meet with DWM staff members before their permits are approved.

The new stormwater ordinance is “a great opportunity for Atlanta. It’s a great move forward,” says Robert Bryant, a registered landscape architect with HDR, Inc.

“The ordinance will set up projects for success in the future,” says Joy Hinkle, sustainable communities associate and water specialist with Southface Energy Institute’s Eco Offi ce. “Builders of single family homes on individual lots will have a little more work to do, but commercial devel-opers have already been doing stormwater analysis on their properties.”

In recent years, the city of Atlanta and its suburbs have

had to cope with both extremes of stormwater: drought and fl ooding. As in many other cities, the fl ooding has caused CSOs, and Atlanta had to meet EPA consent decree requirements.

Stormwater offi cials in Atlanta are realizing more and more often that they can install dual-purpose projects that will help with both problems. Getting stormwater to infi ltrate onsite lessens or prevents fl ooding and CSOs. Capturing the runoff onsite also means that it will be available for irrigation.

Fourth Ward ParkCSOs and fl ooding were persistent problems in the Fourth Ward and Poncey-Highland, one of Atlanta’s oldest neigh-borhoods. The blighted, heavily urbanized area atop low-lying land provided the ideal conditions for runoff to make things miserable for residents.

Stormwater offi cials at the DWM fi rst planned to install more grey, or traditional, infrastructure: sewer tunnels. Feedback from neighborhood residents made them rethink their plans.

The result is an award-winning park with multiple ame-nities that also manages stormwater through green infra-structure and alleviates the CSOs. Completed in 2010, the project cost just about $25 million with land, or just under $20 million for construction costs alone.

The green infrastructure project cost about $15 million

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less than a tunnel would have and delivers much more to the neighborhood. It also eases the load on aging grey infrastructure and mini-mizes downstream fl ooding.

The use of native grasses and plants means lower maintenance costs for Atlanta’s Depart-ment of Parks, Recreation, and Cultural Affairs. These plants soak up runoff and need much less irrigation, an important consideration in light of recent regional droughts.

Historic Fourth Ward Park is also the fi rst component of a 22-mile BeltLine Greenway. This overall greenway project, which will take years to fi nish, is the most comprehensive eco-nomic development program ever in Atlanta.

Bryant notes that the park and the Beltline have spurred $400 million of private development adjacent to the park, once an eyesore. “This is one of the nodes on the trail,” he says.

Fourth Ward Park is an impressive fi rst step. Stormwater from four directions fl ows into a 2-acre lake at the center of the park, which acts as a stormwater detention pond. It was designed to be large enough to prevent the fl ooding that caused the CSOs.

Each side of the park is different, but they all empha-size the fl owing quality of water. Visitors see a tunnel to convey water into the pond, a water wall with sculptural

elements, a step-down channel (a reminder of Clear Creek, once part of the site), and subsurface water that goes into a dry streambed.

“The whole thing was a challenge,” says Bryant. “We had to create 22 acre-feet of storage on a fi ve-acre site, to provide for relief for combined sewers, basically enough to handle a 100-year storm—and do it in an aesthetic setting.”

Bryant calls Historic Fourth Ward Park “the most fun project I’ve ever worked on in my career.” He recalls “how well everybody worked together. The Department of Water-shed Management, the Atlanta BeltLine, the citizens—all had

Fourth Ward Park includes sculptural elements and recreational features.

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a common goal from day one of a three-year period.”

Collaborating with a local artist enriched the work of the engineers and landscape architects. That intertwining of art and science pervaded the project Bryant says.

“From the beginning, we made it a goal that every func-tional engineering feature—a cul-vert, drain fl ume, porous pave-ment—we wanted it to be an aesthetic feature, too. We said, ‘It doesn’t have to be just a pipe.

It can be a spillover waterfall or a recirculating feature,’” explains Bryant. “We never settled on just an engineering solution. We wanted an engineering aesthetic solution.”

Various natural and recreational features make up the 15 acres that surround the lake/detention pond. They include walking paths, an athletic fi eld, playgrounds, a splash pad, a skate park, an amphitheater, and a wildfl ower meadow.

The American Society of Landscape Architects (ASLA) chose Historic Fourth Ward Park as a useful Case Study for Green Infrastructure and Stormwater Management. The project has won several awards, including state and national awards from the American Council of Engineering.

The Atlanta Regional Commission gave its 2012 Devel-opment of Excellence Award as well, because the park “encompasses a large, complex civil engineering and infra-structure project on par with many high-quality develop-ments in metro Atlanta and around the United States.”

Funding for the project came from the Atlanta BeltLine Partnership Capital Campaign, the Department of Envi-ronmental Protection, park improvement bonds, and the Atlanta BeltLine Tax Allocation District. Land was donated by several fi nancial institutions. As with many successful large projects, Historic Fourth Ward Park was a joint public and private endeavor.

The Trust for Public Land began building parcels needed for unbroken green space, as other municipal and private groups have been doing in Los Angeles, Milwaukee, and other cities.

Residents and local business owners formed an inter-est group that became the Historic Fourth Ward Park Conservancy.

Rock Mill ParkLocated in the Atlanta suburb of Alpharetta, Rock Mill Park is another fi ne example of a multiuse park that also func-tions as municipal stormwater management. It is part of a 40-acre site owned by the city of Alpharetta.

Completed in 2007, Rock Mill Park lies within the 100-year fl oodplain of Big Creek. Stormwater quality treatment facilities within the park include green roofs, two enhanced swales, constructed wetlands, three bioretention cells, two sand fi lters, and two dropout forebays.

The most challenging part of the $2 million project was

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“working in and around the fl ood plain,” says J. Scott Talbot, registered landscape architect and principal with Breedlove Land Planning. “The park’s right next to Big Creek, which is known for fl ooding.”

He notes that the project’s few buildings all had to be located above the fl oodplain. Some of the land was built up a bit, but the earthwork had to be balanced with the fl oodplain.

The combination of green infra-structure features and their successful integration has proven to be highly effective in achieving the project’s goal of better water quality. Projects often aim for 80% removal of total suspended solids. Rock Mill Park has a 97% removal rate.

“Stormwater from the highest point wraps around one side, comes below through bioretention cells, goes under the parking lot, and terminates down in the wetlands,” explains Talbot. “It’s like a creek system that leads every-where to the wetlands.”

The Breedlove Land Planning staff

considered making detention areas larger, but after measuring down-stream conditions they realized that doing so would actually increase the peak fl ows at the property line. A large upstream basin and staggering of peak times caused this effect. If Rock Mill Park’s peak fl ows were detained, they would reach the discharge point just when the remainder of the basin was near its peak fl ow. That much runoff at once would be far from the goal of predevelopment hydrology.

Even if they have heard of green roofs, many people don’t know exactly what they are, much less how they work. But after visitors at Rock Mill Park enjoy a picnic lunch in the pavil-ion beneath a green roof, they can step

a few feet away to learn about them.Ground-level tabletop working

models demonstrate how green roofs function in stormwater manage-ment and benefi t the environment. These models are set up to monitor various types of data, such as plant types, system types, growing media, and stormwater quality and quantity performance.

A 6-foot by 3-foot model contains a section with the plants from differ-ent parts of the green roof atop the pavilion. Its second section is a non-green control to test runoff rates and pollutants compared to the green roof. The third panel shows the American Hydrotech system used above.

Two other 6-foot by 3-foot models

Even if they have heard of green roofs, many people don’t know exactly what

they are, much less how they work.

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are of conventional green roofs, one with native plants and one with non-native. The fourth tabletop (8 feet, 5 inches by 4 feet, 5 inches) contains four different modular green roof sec-tions for comparison.

As visitors encounter other storm-water features in the park, they also see detailed educational signage. They learn about natural history and wildlife of the area, the history of their city, the Big Creek watershed, water quality, and how various stormwater features work.

The signs parallel the way the park’s design emphasizes how storm-water quality treatment features are integrated for maximum effectiveness. Members of the public can read-ily see why sustainable stormwater management can not only work, but also enhance the environment for everyone.

An access point to the Greenway Trail, Rock Mill Park has an open pavilion, an amphitheater, a friendship path with seating, walkways, a wet-lands observation deck, and a mainte-nance building for Alpharetta’s Parks Department. Parking is available for both trail and park users.

This astute use of green infrastruc-ture also merited an ASLA Case Study designation. The ASLA described Rock Mill Park as “a model of cost effective, sustainable design.” The project “provides a sensible alternative to traditional (and unsightly) detention ponds and shows how multiple best management practices can be used in succession to form a comprehensive stormwater solution.”

The Rock Mill Park project also received a Merit Award from the Geor-gia Chapter of ASLA. Other awards include Water Resources Project of Excellence from the American Water Resources Association and Outstand-ing Achievement from the Georgia Chapter of the American Society of Civil Engineers.

Reclaiming Brownfi elds, Catching RainBuilt on a brownfi eld site, the East Atlanta (Public) Library is an 8,000-square-foot building that serves as a neighborhood branch

library and meeting place. All storm-water that falls on the site is managed within its borders.

Runoff fl ows through light-colored pervious concrete paving in the park-ing lot and drains into an underground retention chamber. From there the runoff is slowly released, allowing it to infi ltrate into the soil.

The Eco Offi ce is a three-story commercial building in downtown Atlanta. It serves as an offi ce, training, and demonstration facility for green building and sustainable design for the Southface Energy Institute. The 10,100-square-foot building is a work-ing example of effi cient use of energy, water, and resource management. It is one of the most sustainable offi ce buildings anywhere, using 84% less water and 53.3% less energy than a comparable, code-built facility would.

The Eco Offi ce is constructed entirely from off-the-shelf materials and ordinary technologies—nothing that couldn’t be duplicated elsewhere. Its energy cost averages less than $25 per day.

Atlanta lacks proximity to a major body of water. Over 98% of the city’s water supply comes from surface water sources, so effective stormwater management for water quality is criti-cal for all the city’s residents.

The Southface Institute’s Eco Offi ce sets a good example. All of its onsite stormwater either infi ltrates into the ground or is collected and put to good use within a fl exible system.

“We love our rain catching and stormwater management system,” says Hinkle.

The property has two cisterns for collecting rainwater. The rooftop cistern collects runoff from the solar photovoltaic array through a gutter system. The runoff drains through a fi lter to remove particulates before it fl ows into the 1,750-gallon wood-clad plastic cistern.

This rainwater has several uses besides toilet fl ushing. It is used in the condenser unit evaporative cooling system spray, the solar PV array spray system, the compost tank spray, and the dedicated outdoor air system.

“The most interesting thing about our system is how small our collection

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area is, but how well it meets our needs. It’s only a small area of a solar panel on the roof, but it supplies our inside water,” says Hinkle.

Runoff fl ows from the Eco Offi ce campus and the green roof downhill through a veg-etated swale, which removes pollutants. It is maintained with erosion prevention tubes fi lled with compost and gabions fi lled with reused concrete riprap.

At the property’s lowest point, the runoff fl ows into a 14,500-gallon underground cistern via the cistern’s vegetated, permeable top. This cistern is made of plastic box forms surrounded by an impermeable membrane.

Rainwater collected in the underground cistern is used to irrigate the landscaping on the Eco Offi ce campus. During extended times without rain, this water is also used to replenish the rooftop cistern.

“The two systems can be intercon-nected,” explains Hinkle. “We can switch on a pump. This interconnected arrangement has served our needs well. We have had to do that a few times during hot, dry weather.”

Not having to rely on municipal water reduces costs and increases peace of mind during Atlanta’s hot, dry

summers. Having a system that would make stormwater an asset instead of a problem was an integral part of Eco Offi ce from the fi rst design stage.

“We defi nitely see an uptick in interest in harvesting stormwater, particularly on irrigation use,” says Hinkle. “Our water rates are high and our sewer rates are high, so there’s an interest in reducing potable water for fi nancial as well as environmental reasons.”

What surprised Hinkle about the

Eco Offi ce’s rainwater collection system is “how easy it is, how you don’t notice it. There’s certainly some maintenance to this truly sustainable system, but it does not change the way we’re operating our plumbing or operating our building.”

She notes that the most challenging part of installing the rainwater harvest-ing systems was “a little bit of a learn-ing curve and a little bit of admin-istrative hurdles with the building inspector, because we use harvested water inside as well as for irrigation.”

The health department was also cautious at fi rst because the Eco Offi ce is a building open to the public, with many people coming and going. For-tunately, Atlanta plumbing codes were being changed at about the same time to be more fl exible.

Real-time and historical data on a number of energy and water con-sumption metrics at the Eco Offi ce are online through a Lucid Design Group Building Dashboard. The information is useful not only for building profes-sionals, but also for homeowners wanting to make their houses more sustainable. Knowing the daily gallons of rainwater captured, consumed, and saved, current rainwater levels in the cisterns, and local weather conditions is useful comparative information for The 40-acre park has enhanced swales, constructed wetlands, and other water-quality features.

Rock Mill Park features a pavilion with a green roof.

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anyone interested in capturing storm-water for onsite use elsewhere.

The Southface Eco Offi ce has a LEED Platinum certifi cation from the US Green Building Council. It also meets the 2030 Challenge launched by the nonprofi t group Architecture 2030 and has earned EarthCraft Light Commercial and Energy Star certifi cations.

Through its weekly Wednesday tours, which are open to anyone, the Eco Offi ce staff is educating the public and construction employees about stormwater issues and green infra-structure. About 40,000 people take classes and workshops there annually.

Rainwater catchment systems are getting more attention in Atlanta because of the droughts of recent years. The Regional Business Coalition of Metropolitan Atlanta and South-east Rainwater Harvesting Systems Association (SERHSA) have created a campaign to increase their use in metropolitan Atlanta.

The associations’ joint goal is to

reduce water use by 27 million gal-lons per day over the next fi ve years. Rainwater harvesting fi rms show past projects installed at both residential and commercial locations, in diverse applications.

“There are some good conversations going on between builders and the rainwater harvesting companies based in our state,” says Hinkle. “The compa-nies manufacture their systems in the state, so that’s a good economic driver.”

Rainwater is harvested for irriga-tion at Turner Field, the home of the Atlanta Braves Major League Baseball team. The system at Oliver House, a Senior Living Center with 88 apart-ments, supplies all the water for toilet fl ushing and irrigation.

In the Atlanta suburb of Sandy Springs, stormwater runoff from the 17,000-square-foot recreation center at Hammond Park was eroding a hill beside the sports fi eld. The solution was to collect the runoff in a 9,200-gal-lon tank that irrigates the groundcover on the hill. The aboveground tank

teaches the public about stormwater.Atlanta’s most infl uential corporate

entity is Coca-Cola. One of its many sustainability projects is donating used 60-gallon syrup containers to the Chattahoochee Riverkeeper. The environmental group turns the containers into rain barrels for homeowners.

It is obvious from these innovative stormwater projects and others that Atlanta recognizes the value, both fi nancial and aesthetic, of investing in green infrastructure. Seeing rain harvesting as an asset—especially with droughts to come—increases the value of that investment.

Margaret Buranen writes on the environment and business.

For related articles: www.stormh2o.com/program-management


Rebecca Joyce told the story during a telephone interview of a neighbor in the Central Shenandoah Valley who had become

so accustomed to flood waters over-taking her home that her emergency preparation plan was to keep the fam-ily photo album on a table near the front door in case she’d need to make a quick escape.

But acting alone, it’s hard to dodge such an all-encompassing disaster. “People who go through repetitive fl ooding have had to rebuild their lives so many times they’re worn down,” says Joyce. But being prepared to lose everything is not sustainable; it is resignation, and Joyce, who is senior planner for the Central Shenan-doah Planning District Commission (CSPDC), says there is a much better alternative than giving up.

The CSPDC serves close to two dozen jurisdictions in fi ve counties of the Shenandoah Valley region, including the cities of Staunton and Harrisonburg, providing consultation covering land-use planning, transporta-tion, water and wastewater utilities, natural resource management, afford-able housing, economic and commu-nity development, disaster mitigation and preparedness, agritourism, and human services.

Joyce advocates building resilience into every aspect of a community’s planning as one of the best ways to reduce damage, hardship, and loss, during and after a natural or

manmade disaster. Planning for resilience can give residents and businesses in areas prone to fl ooding not just the tools to deal with crises, but also the tools needed to recover quickly and to bounce back toward prosperity.

Being resilient can mean dif-ferent things in different situa-tions, Joyce says, but she also notes that preparing a pathway to recover from the worst should begin long before disaster strikes; it should begin by taking a close look at the risks that a community faces. And according to Joyce, fl ooding is not the only natural hazard facing residents of the Central Shenandoah Val-ley. The CSPDC All Hazards Mitiga-tion Plan notes that residents also might have occasion to deal with high winds from tornadoes and derechos; wildfi res have set off the alarm in the vast expanses of forests and public land in the region in the summer; and at the other extreme, epic snowstorms, ice storms, and sudden snowmelts in recent winters have proved that it would be wise for residents of Shenan-doah communities to be ready for almost anything.

Helping share that awareness and to share ideas on what to do about it is part of Joyce’s business.

The CSPDC is funded through grants and assessments to operate as a go-between and advisor to state and local government and the communities they serve on issues related to growth

and development. Joyce strives to encourage communities in the region to include resilience in their plans for future development as well as in cur-rent operations.

Storm TrackThe Shenandoah Valley in Virginia might not be the fi rst place that comes to mind when the subject of hurricanes comes up, but when they do show up they cause havoc. Hur-ricane Camille in 1969 marked a turning point in the way people in the area thought about fl ooding. It hit the Gulf Coast as a Category 5 storm and weakened to a tropical depression before reaching Virginia. According to a historical entry in the All Hazards Mitigation Plan, precipita-tion fell over many hours, dropping

Resilience: Communities Connect the Dots to Dodge Disaster

BY DAVID C. RICHARDSON


more than 27 inches of rain in Nelson County and over 10 inches in the area from Lynchburg to Charlottesville. Flooding and landslides, triggered by saturated soils, resulted in catastrophic damage. More than 150 people died and another 100 were injured. At the time, damage was estimated at more than $113 million. In the Central Shenandoah region, as a result of Camille, signifi cant fl ooding occurred in Rockbridge County, the cities of Buena Vista and Waynesboro, and the town of Glasgow. Twenty-three people died in Rockbridge County, with dam-ages exceeding $30 million (in 1969 dollars). The results were plain to see, Joyce says: “Some of the houses had water up to the second fl oor.”

During tropical storms, ortho-

graphic lifting makes things even worse for this largely agri-cultural district, with the winds wring-ing precipitation from moist tropical air forced up and over the Appala-chian and Blue Ridge Mountains. The result, Joyce says, is “pockets of fl ood-ing” that can occur almost anywhere after intense and rapid rainfall.

“We have had big trouble from hur-ricanes, because after they have made landfall and they are crossing the state and moving from the Gulf, they just stall out here and drop tons of rain,” she says.

And, since the time of Camille, the storms have continued, with Agnes in 1972 bringing 15 inches of rain. In 1985, Juan brought record fl ood levels to Waynesboro. In Buena Vista, 3 to

6 feet of water fl ooded homes and businesses. Hurricane Fran, in 1996, broke almost all fl ood records along the Shenandoah River with 8 to 14 inches of rainfall, and in 2003 during Hurricane Isabel, as much as 20.6 inches of rainfall was recorded by the upper Shenandoah monitoring station in Augusta County.

“Our cities have issues with fl ood-ing because they have creeks or streams that run through them,” says Joyce. In addition, she says that due to the peculiar feature of karst topog-raphy that honeycombs the region, the precise locations of fl oodplains are sometimes diffi cult to nail down. “A good portion of the fl oodplain is actually underground, so you don’t even realize that the water is rising, and it has to have somewhere to go, so it seeps through.” Which, she says, means fl oodwaters sometimes invade homes from the inside out.

But she notes that in most cases the fl ooding in the area “is the result of rivers swelling over longer periods of time” until they overfl ow their banks.

Moving UpThe fi rst resilience efforts in the region were fl ood mitigation projects such as the one in Glasgow, VA, at the confl u-ence of the Maury River and the James River. “Half of the town is in the fl ood-plain, so they had issues with repetitive fl ooding of houses,” explains Joyce.

With a grant from the Federal Emergency Management Agency (FEMA), Joyce says, CSDPC proj-ects “either elevated, relocated, or acquired” 53 houses in the fl ood-plain. “Now those houses are either protected because they are higher, or we’ve put them on the back of a truck and moved them out of the fl oodplain.

Flooding in Rockingham County during Hurricane Fran in 1996

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The land was acquired, and the house was demolished, and the land will be kept as an open space so that no one can build on it again.”

Stabilizing Triage To determine where to begin the pro-cess of acquiring or mitigating fl ood-plain properties, the CSPDC evaluated how deep each of the at-risk homes were in the fl oodplain. It then used a prioritization process dividing the fl oodplain houses into three categories based on fl ood depth and frequency. CSPDC used that information to triage its approach to mitigation. “The fi rst houses we dealt with were the ones that got the most repetitive fl ooding and the deepest fl ooding, then the second phases received the next tier of funding, and the third phase received the least. But all of them were signifi -cant, because when you receive the grants from FEMA you have to do a benefi t-cost analysis and prove that the mitigation projects you implement are cost effi cient based on the type of house and what you’re going to do.”

According to Joyce, establishing the triage process based on the severity of the risk for each property was a better approach than just having a list “where everyone was thinking: ‘I know I’m number one, or I know I’m number two.’” It not only served to reduce the potential for confl ict but also provided fl exibility for managing the program. “Sometimes during mitigation projects, personal issues or other things would come up where a person might be having surgery, or they couldn’t be out of the house for one reason or another. We had a group of houses we were working with, so if that one per-son had to be delayed we were able to keep going with the project.”

Compound DisasterThe Central Shenandoah Valley’s Haz-ard Mitigation Plan considers fl ooding itself a multifaceted hazard. The plan notes that as a result of fl oods, homes and business may suffer damage and be susceptible to collapse; that fl oods pick up chemicals, sewage, and toxins from roads, factories, and farms and therefore any property affected by the fl ood may be contaminated with

hazardous materials; and that debris from vegetation and manmade struc-tures may also be hazardous following the occurrence of a fl ood. In addition, fl oods may threaten water supplies and water quality, as well as initiate power outages.

With this in mind, CSPDC takes a

holistic view of dealing with disaster. For instance, recognizing that damage to critical facilities can signifi cantly increase the overall effect of a fl ood event on a community, The Hazard Mitigation Workgroup implemented a survey of key facilities in the region.

Using a geographic information system (GIS), the critical facility points were intersected with the FEMA fl ood zones. The CSPDC used a 30-foot buf-fer on the facilities to provide a radial distance from the center of the build-ing to determine the proximity to the fl oodplain. Although the initial study indicated that 52 critical facilities were located near or in the fl oodplain, the study also revealed “great diversity in the type of facility located within or in close proximity to the fl oodplain.”

The report, however, cautions that GIS determination of fl oodplain vulnerability should be used only as a planning tool. The plan notes, “In order to accurately determine if a structure is actually in the fl oodplain, site-specifi c information must be available.” CSPDC says it is then up to each jurisdiction, armed with this information, to decide

for itself the best way to prepare facili-ties for the possible hazards of fl ooding.

By 2004, the CSPDC had spon-sored almost 100 mitigation projects in eight localities to keep people and their homes safer in potential fl ood situa-tions. Almost $9 million in grant fund-ing was used to fl ood-proof, elevate,

relocate, or acquire homes. While a big part of promoting fl ood resilience is encouraging people not to reside or build their businesses in the fl oodplain, its bigger role is keeping people safe; for that reason, CSPDC projects have also included outreach efforts to special populations such as the disabled, elderly, and non-English-speaking com-munities. One such effort resulted in a successful evacuation adjacent to a fl ood-prone river in Waynesboro, VA, on the eve of Hurricane Isabel.

Can Money Buy Resilience?The federal government pours a lot of money into disaster relief, and the unfortunate reality is that disasters keep happening anyway. According to The Center for American Progress, the federal government spent $136 billion total from fi scal year 2011 to fi scal year 2013 on disaster relief.

“Nearly all of this disaster spending was for relief and recovery from major storms and other smaller natural disas-ters. Most of these disasters are symp-tomatic of manmade climate change,” the authors write. And you don’t have

Relocating a house in Glasgow, VA


to look far for predictions of more and worse to come.

The big question is how much can a federal government do in the face of compounding risks? FEMA itself has begun trying to encourage communi-ties to be more resilient as an alter-native to relying on the emergency management agencies to respond to try to rebuild post-disaster.

Joyce gives a good deal of credit for CSPDC’s success in implementing its hazard mitigation initiative to FEMA’s Project Impact program, which oper-ated at the federal level from 1997 until 2001. It helped hundreds of cities and local jurisdictions, including those in the Central Shenandoah Val-ley, with disaster readiness initiatives based on local needs and priorities. Although that program no longer exists, its spirit continues in the form of Tulsa Partners in Tulsa, OK, one of the communities that had participated while the program was in full swing.

Tim Lovell, executive director of Tulsa Partners, one of the direct

descendants of FEMA’s Project Impact, says he’s not arguing with NOAA’s and the National Weather Service’s predic-tions of increasing “severe weather and severe weather impacts”; he just wants to be ready.

The inspiration for programs pro-moting resilience, he says, “Seems to be coming from a number of perspec-tives. There is some effort from FEMA with their whole community approach to foster resilience at the local level. One of the things at the federal level is the awareness of the limitations that come with working at the federal level or the national level.”

But overall, he says, there is a dawning realization that “there are certain actions that promote resilience that can only be done locally by the communities involved.”

According to Lovell, there are two steps to becoming resilient. “One is to be informed of the issues and the kinds of things you can do to minimize the impact of disasters before they happen. And the second is to become

connected—know your neighbor.” He says, “Community connections

between local communities, as well as local communities to state regional and national and even community-to-community across the country, can provide mechanisms for communities to foster resilience to learn from one another, to fi nd models where they might be able to apply something that has been done in another commu-nity. The more connections you have within the community and also outside the community—that seems to make a difference with resilience. After a disaster, a more interconnected com-munity is able to bounce back faster.”

This is a lesson Tulsa has learned over hard years of experience. Lovell says that during the 1970s and 1980s the city had nine federal disaster dec-larations, primarily due to fl ooding.

The most devastating shock came in the midnight hours of Memorial Day 1984. A killer fl ash fl ood hit the city during a heavy rainstorm and took 14 lives, injured 288 people,

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damaged or destroyed nearly 7,000 buildings, and left $180 million in dam-ages ($257 million in 1994 dollars).

City offi cials responded immedi-ately and before the night was over had assembled the city’s fi rst Flood Hazard Mitigation Team to develop the city’s strategy by crafting a unifi ed program to curb fl ood losses.

Lovell says during the 1980s, “a coalition of the people who were impacted by the fl ooding, professional hydrologists and engineers who knew some of the ways that you could fi x this, and public offi cials got together and worked on the stormwater prob-lem.” During that process, he says, the group “made sure to inform the com-munity about what needed to be done.”

Ultimately, the program they put in motion included relocation of 300 fl ooded homes and a 228-pad mobile home park, $10.5 million in fl ood con-

trol works, and $2.1 million for master drainage plans. The total capital pro-gram topped $30 million, mostly from local capital sources, fl ood insurance claim checks, and federal funds. But it went further than that, giving birth to an ongoing collaboration in Tulsa of those impacted and concerned members of the community, focused on disaster preparedness.

During the late 1990s when FEMA was looking for communities to pilot its Project Impact, emphasizing public private partnership in disaster pre-paredness and recovery, Tulsa became one of the fi rst communities invited to participate, in part, Lovell says, because “the city already had a network of partners, and they had actually started working on multiple hazards.”

The effort has snowballed, and the city has since bought out 1,000 at-risk structures through FEMA repetitive fl ood loss grant programs.

Bill Robinson, Tulsa’s lead storm-water engineer, says the city has implemented regulations requiring all new storm sewer systems be designed for the 100-year fl ood event and has upgraded Tulsa’s fl oodplain regula-tions to employ a signifi cantly tougher standard than that required by FEMA. In addition, Robinson says, Tulsa’s participation in the community ratings system has achieved a Class 2 rating for the city, which helps the residents save money on fl ood insurance policies.

According to the Tulsa website, since the city adopted comprehensive drain-age regulations 15 years ago, none of the structures built in accord with those regulations has fl ooded. Nevertheless, says Robinson, Tulsa’s resiliency efforts are just at their beginning.

Robinson, who is also chair of Oklahoma Floodplain Management Association, says the city “has a pretty

active hazard mitigation program, but there is more to resilience than just hazard mitigation.” He gives the example of Tulsa’s Stormwater Drain-age and Hazard Mitigation Advisory Board, made up of citizens from public sector, private business, and non-profi t organizations, whose mission is to provide input to the mayor and city council on things that can be done to further the city’s stormwater manage-ment and hazard mitigation.

In addition to addressing stormwa-ter management issues, he says, the advisory board has become active in meeting a broad scope of emergency challenges. To address concerns over power outages that might occur as a result of fl oods or other disasters, the board has begun supporting legislation to require emergency generators or transfer switches on all nursing home facilities as well. “Back in 2007 we had a bad ice storm where parts of the city

were out of power for up to 10 days,” he says. “That put a big strain on the Fire Department, because they were charged with evacuating all these peo-ple on life support from nursing homes that didn’t have backup generators.”

Every Little Bit HelpsTulsa is constantly looking for new, cutting-edge solutions to stormwater quality issues, and under the right condi-tions, Robinson says, some of these mea-sures can have the desirable side effect of addressing water quantity as well. For instance, in conjunction with the Oklahoma Ready Mix Concrete Associa-tion, Oklahoma State University, and the National Ready Mix Concrete Associa-tion (NRMCA), Tulsa recently sponsored a pervious concrete demonstration pour on city property, in the parking lot of Street Maintenance Division. Five differ-ent concrete manufacturing companies poured their pervious concrete into test forms for monitoring to determine if pervious concrete will hold up under Tulsa’s weather and soil conditions.

Although pervious concrete might be considered a stormwater quality measure, small things add up when you are talking about low-impact develop-ment, or LID. “We’ve been seeing an increased trend in short-duration, 10-year storms,” says Robinson. Not many structural measures short of a levees, conveyance, or a huge basin can handle the runoff from a 100-year storm event; however, on the lower end of the scale, Robinson says, LID techniques, in addition to addressing water-quality issues for which they are designed, could have some potential for alleviating localized fl ooding that can occur as a result of high-intensity but short-lived downpours.

With the trend continuing toward more intense storms, life-saving mea-sures have become a central focus of Tulsa Partners’ approach. Although Tulsa Partners does not have an emer-gency response role in disaster recovery work, Lovell traveled to meet with com-munity leaders in the aftermath of the Moore, OK, tornado earlier this year. “I did actually see the damage myself. I talked to the emergency manager there along with some other people from Tulsa Partners and the NHMA as well

Tulsa is constantly looking for new, cutting-edge solutions to stormwater quality issues, and some of these measures can have the desirable side effect of addressing water quantity.


as the stormwater drainage advisory board,” he says. “At the city of Tulsa, much of what we’re trying to look at is what we can learn and what we can promote in the future in terms of disaster-resistant construction.”

He says he learned a major lesson—not precisely in the realm of storm-water management, but one he hopes to share not just in his hometown but also more widely: “Safe rooms proved themselves there. There is no evidence of a safe room failure in Moore, and in fact they saved lives. We’re having a lot of discussion about the need for safe rooms in schools.”

Robinson says Tulsa is also consider-ing a strategy to build back better in case disaster does return. “Typically, if a community is not ready in advance and they lack something in their building code to encourage building back better, after the disaster the focus is ‘Let’s get everything up and running again as soon as possible.’ You build back to the status quo—you don’t build it any better that it was before.”

Looking at the broad view of resil-ience in a community where disaster risks include not just fl oods but also severe thunderstorms, hailstorms, and devastating tornadoes, Robinson says, “We’re looking into fortifi ed building codes through the Institute for Busi-ness and Home Safety. They’ve got relatively inexpensive construction methods, so that for less than 5% of the cost of the structure, it can be hard-ened so that it can withstand 135-mile-an-hour winds.”

Lovell says becoming resilient is an ongoing process, not a one-time project. “And there’s a reason for that; any time you create anything or build anything, there’s going to be maintenance. Just like if you move into a new house you may expect not to have much mainte-nance at fi rst, but over time there will be. It’s the same with an effort to make a resilient community. Even if you reach the point where your community is 100% resilient, you’re still going to have some things you have to do to keep things up—you’re still going to

have people moving into the area who are not educated about the kinds of things may happen, you have children that grow, and the people who are here now may not be here in 20 years.”

In a fast-changing world, Lovell says, “you always will have to continue education, to continue looking at how things are and seeing what you need to do in order to continue to make the community a resilient one.”

He adds, “To me, the resilience of the community was really formed in a cru-cible of those nine federal disaster dec-larations and the fl ooding that occurred there, and it is still apparent today.”

David C. Richardson is a frequent contributor to Forester publications.

For related articles: www.stormh2o.com/flood-control

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The Principles of Gravity SeparationPart 2. Laminar settling, swirl concentration, and fl otationBY GARY R. MINTON

This is the second of a three-part series on gravity separation. Part 1 ( www.stormh2o.com/SW/articles/22950.aspx ) appeared in our October 2013 issue.

Gravity separation is a unit process in which gravity removes settleable solids and associated pollut-ants, fl oatables, and dispersed petroleum products. Gravity separation is the primary mechanism of pollutant removal in stormwater treatment systems. Figure 1 conceptually displays gravity separation. Removal occurs downward for solids denser than water like sediment: upward for solids lighter than water such as dispersed droplets of petroleum oil and paper. The former is sedimentation; the latter is fl otation. The fundamental engineering principle of gravity separation is the settling velocities of particles, and rec-ognition of two types of settling in stormwater treatment: dynamic and quiescent. Settling velocity is affected by par-ticle size, shape, and specifi c gravity, and water temperature.

Gravity separation consists of several unit processes, shown in Figure 1. This series of articles discusses sedimentation, the downward removal of stormwater particles.

Laminar settlingThe principle that hydraulic loading rate is the dominant factor with discrete sedimentation is exploited in the use of laminar settlers. Laminar settlers are constructed in vari-ous confi gurations, two of which are illustrated in Figure 2. Laminar settlers equate to a stack of very shallow basins. The concept is illustrated in Figure 3, which shows countercurrent settling: solids slide down the plate opposite the direction of the fl ow. Con-current settling (water fl ow from the top) as well as cross-fl ow settling (water entering from the

GRAVITY SEPARATIONSedimentation Floatation

Hydrodynamic and Vortexseparation Laminar settling

UNIT PROCESSES

SYSTEMPERFORMANCEWetlands Wet ponds

Swales and strips FiltersWet vaults Swirl Concentrators

UNIT OPERATIONS

PRINCIPLESSettling types Stokes Law

Settling velocitiesDynamic and quiescent settling

Figure 1. Elements of gravity separation

Figure 2. Laminar settlers Figure 3. Laminar settling


side) are also employed. Laminar settling devices have been in use in water treatment for over three decades and are now employed in stormwater treatment. Plates are typi-cally placed at an angle to facilitate self-cleaning. Laminar settlers provide a signifi cant increase in surface area per unit volume of basin, leading to a decrease in the size of the basin for the same design event. The effect is to achieve equivalent sediment removal effi ciency during the dynamic period but with a much smaller basin. The cost of the set-tlers is offset by the savings from a reduction in the size of the basin.

Care must be taken with the use of laminar settlers in stormwater treatment because of the importance of the quiescent period and basin volume rather than surface area. The volume of the basin may be so reduced that an insuffi cient volume of each storm is retained, with the consequence that the contribution of the quiescent period to removal effi ciency is compromised. The mathematics of horizontal plate projection are presented later in this article.

Swirl ConcentrationThe size of a settling basin may be reduced by swirl concen-tration, also known as vortex, accelerated gravity, or teacup separation. The collective name is hydrodynamic separation. The concept was developed for combined sewer overfl ows (CSOs) intended to remove coarse organic and inorganic solids. An example is presented in Figure 4. Figure 4 shows

a continuous withdrawal of the collected sediment, which is not practiced with stormwater treatment. The graphic is of a separator that takes sand out of wastewater. The water enters tangentially into the basin as shown typically at an elevation lower than the primary outlet, imparting a circular motion to the fl uid in the system.

Figure 4. Vortex separation

stormcapture.com


Terminology. What is the defi nition of hydrodynamic separation? There are two defi nitions used in settling theory. One is the separation of particles from moving fl uid. The second relates to air pollution equipment. When air is diverted in a turn of 180 degrees, the particles, due to inertia, continue on their direct path, hitting the wall and settling to the bottom of the device. The fi rst defi nition is very generic, applying essentially to all of the storm-water treatment devices. It is therefore a defi nition without uniqueness or merit. The term hydrodynamic separa-tor is useless because it also applies to wet ponds, wetlands, grass swales, etc.

The second defi nition applies to a process that does not exist in swirl concentra-tors. Consequently, the uses of the term hydrodynamic separators is misleading, implying some special attribute of these systems that does not exist. Although it has been in use for two decades, the term hydrodynamic separation should be dropped. It will also be shown, in the next section, that vortex separation plays a minor role in so-called vortex separators.

The original name for vortex sepa-rators was swirl concentrators. The term vortex separator came into vogue in the 1990s. The older terminology of swirl concentration (or separation) and swirl concentrators (or separators) appears to be more applicable. As an aside, the older terminology was originally applied to a separator with internal design elements signifi cantly different from what are called today vortex separators. However, this con-fi guration was found to be less effi cient because of excessive turbulence and was abandoned. Regardless, it is not unreasonable to apply this terminology to today’s “vortex” separators.

Process. A vortex is the rotating motion of a fl uid around a common center. As shown in Figure 5, the water enters tangentially into the basin, sometimes at an elevation lower than the primary outlet, which is the most effective method, imparting a circular motion to the fl uid in the system. The swirl motion initiates at a fl ow rate of about 10% of the separator’s capac-

ity. Systems with weak vortex forces improve settling only by 0.1 g, 1/10th of normal gravity: a minor increase. The minor addition is due to the fact that the infl uent velocities in stormwa-ter separators are modest.

Another aspect of the process is what is called secondary fl ow. Illus-trated in Figure 5, secondary fl ow is the movement of water toward the center axis as it swirls gently around the vault. One explanation for its presence is that friction at the separa-tor bottom slows the movement of fl uid relative to the surface, causing a

pressure difference between the water surface and the bottom at the perim-eter of the separator. The difference causes downward movement at the perimeter, the secondary fl ow. Sedi-ment, denser than water, settles in the center of the separator. Particles lighter than water, litter, collect on the surface at the perimeter. The combined effect of primary rotation about the axis and secondary fl ow increases the path length of the particle, increasing the opportunity to settle.

Because of the dominance of small storms, sediment tends to accumulate

Figure 5. Vortex motion

Plan View

Cross Section View


around the inlet during the small to medium storms, which are the most common storms, but is scoured and moved inward via secondary fl ow to the center where the radial velocity is zero. At high fl ows, velocities at the center of the vortex exceed the settling rates of many of the particles, causing upward movement and loss from the vault. Solid particles migrate toward the center and accumulate as long as they are heavy enough to withstand the updraft.

Figure 6 compares a laboratory study of a swirl concentrator to a simulation of Stokes Law. Comparison indicates that the concentrator did much better, apparently contradicting statements just made. The immediate observation to be drawn from Figure 6 is that the centrifugal forces play no role in stormwater separators. If they did, the performance would increase rather than decrease with increasing fl ow rate. Note that the performance goes down with rising fl ow rate, an indication that centrifugal motion is not present. Vortex separation and the other factors herein likely play a sig-nifi cant role at higher fl ow rates, which is apparent from Figure 6.

The immediate thought as to the cause of the spread of the two curves is added acceleration to the normal gravitational force, which occurs due to the radial velocity of the water: the greater the velocity, the greater the added force to gravity. However, as noted previously, the radial velocities in stormwater vortex separators are modest, on the order of a few feet per second at the entrance and less in the vessel. At these velocities the effect is less than 0.1 g at high fl ows for all but one swirl vault.

The line labeled “USEPA SWM” in Figure 6 is the simulated settling expected by Stokes Law, which was placed in the SWMM mode by the author of the study. However, SWMM contains an adjustment factor that rec-ognizes that vaults do not have 100% hydraulic effi ciency. Thus, the line does not truly represent settling expected by Stokes Law, whose calculations presume 100% hydraulic effi ciency. As only about half the difference is likely due to improved hydraulic effi ciency,

other factors must account for the remaining difference between two curves in Figure 6. It is not centrifugal force, as noted previously. The water velocities are insuffi cient.

One reason commonly given is that with swirl motion the particles move along a longer fl ow path before reach-ing the bottom than if settling directly to the bottom, giving the particle more time to settle. This view ignores fundamental settling theory, in which discrete settling is function of hydraulic loading rate rather than residence time. Consider the following thought experi-ment. Two circulars basins are the same in all respects. In one, a particle is released into the center of the basin at the surface. It falls directly to the bottom in accordance with Stokes Law. In the second basin, the particle enters via a horizontal inlet pipe, tangentially as with a common swirl concentrator. As it enters, the particle has only hori-zontal velocity. But as soon as it enters, it begins to experience a downward velocity due to gravity. Its fl ow path is longer than the particle in the fi rst basin given its forward motion, but its downward velocity is the same as the particle in the fi rst basin. Consequently, both particles in the two basins arrive at the bottom at the same time.

A factor to consider is the bound-ary. A vortex in open water has no distinct boundary. But vaults have a distinct hard boundary, the outer wall and the bottom. The presence of a distinct boundary has two effects. Bar-ring boundary turbulence, the fi rst is that the water velocity and shear stress at the boundary are zero, resulting in particle settling. The second effect is the striking of particles against the wall. The fl ow rate into a swirl concentra-tor is substantial in proportion to its volume, much greater than in sedi-mentation basins. Boundary conditions are irrelevant with large sedimentation basins; not so with swirl separators or direct-entry vaults. In effect, there is a large fl ow rate entering a basin with a small diameter, which results in a substantial rate of particles hitting the wall. Many of these particles succeed in settling to the bottom.

The long fl ow path may also be a factor, not because it increases the

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detention time per se, but because it increases the opportunity for particles to strike the wall. Also, eddy motions in the vicinity of the wall “push” particles toward the wall. There is also a tendency of particles to be drawn to the wall, specifi cally those particles that move ahead in the water as they enter the vessel. Particles that move faster than the fl uid migrate toward the wall, whereas particles that move more slowly migrate toward the center. Lift is the principal cause of radial migration. As particles approach the wall they are drawn toward the wall particularly under laminar conditions.

A fi nal consideration is the phenom-enon of two ships moving in parallel close together such as a naval supply ship supplying an aircraft carrier. The ships tend to move together, which the helmsmen on both ships must care-fully avoid. This phenomenon occurs because the pressure of the water on the outboard side of each ship is less than on the inboard side. A similar phenomenon could occur with respect

to particles near the wall of the separa-tor. Regardless, the full answer as to the processes in swirl concentrators and their respec-tive roles is not fully understood. It has been stated that no theory explains all of the experimental results regarding the radial migration of particles.

As a fi nal note, the difference between the two curves in Figure 6 is a function of the particle size distribution. The effect is less as the percentage of coarser material increases. One could include boundary effects as a component of vortex separation. If so, vortex removal would be the primary factor for all of the products with respect to the differ-ence between the two curves in Figure

6. However, inasmuch as vortices in nature do not pose a boundary effect, it seems reasonable to identify it as a separate removal process.

The above observations raise the reasonable question as to why those vaults not employing swirl motion do not benefi t from the striking of par-ticles against the vault wall. It is likely

Figure 6. Laboratory vs. simulation results

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www.StormH2O.com has a lot to offer professionals involved in stormwater and surface water quality who want to keep up. But the one most important reason for visiting the Stormwater home page is to get the breaking news in the industry. So you won’t want to miss Janice Kaspersen’s Web editorial, spotlighting what’s new and interesting, and be sure to catch The Latest, a compendium of today’s hottest stories.

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that they do, but not as well because of greater turbulence than found in swirl concentrators. The swirl motion in swirl concentrator separators likely results in a better “management” of the stormwater with respect to the bound-ary condition; that is, less turbulence with the outcome being a higher percentage of particle strikes resulting in particle removal.

Oddly it has been observed that a true vortex motion should be avoided at high fl ows. A strong vortex results in upward velocities at the center, which exceed the settling velocities of previously captured particles, resulting in their resuspension and loss from the system. Removal occurs in the vortex eddy. Performance is increased by about 25% over an empty tank and about 15% over tube (lamella) settlers. These differences may increase with increasing fl ow. This phenomenon may exist in wetlands and swales, with the vegetation serving as the plates. But this is unlikely.

Performance. Swirl vaults vary considerably with respect to separa-tor geometry, sediment storage, and elements to moderate fl ows to avoid resuspension and loss of collected fl oat-ables. Thus, swirl vaults of the same size will differ in performance. The presumed enhancement of small vaults is the result of a combination of effects: improved hydraulic effi ciency, particles striking the wall, longer particle shear zones where there is an abrupt redirec-tion of water fl ow, and vortex motion.

The relative role of each is in turn dependent on many factors, including particle settling velocity and density, inlet velocity, system confi guration, and internal elements such as baffl es. As such, it is essentially impossible to identify the relative role of each effect and the contribution of each factor. Performance equations must be empirical, developed for each type of vault. The relationships typically take the form of simple ratios such as the hydraulic loading rate to the settling velocity of the particle, the settling velocity to the inlet velocity, and the chamber to inlet diameters.

Mathematical modeling of perfor-mance has taken several forms with differing observations as to its ability

to satisfactorily predict performance as well as the appropriate equations to scale the results from a small labora-tory unit to larger fi eld units. With few exceptions, the studies have been of systems with bottom discharge and of a particular confi guration. Computa-tional fl uid dynamics (CFD) appears to satisfactorily simulate fl ow paths. However, simulation of particle settling is sensitive to the assumed boundary condition as to its effect on the reten-tion of particles upon contact with the bottom or wall. Mathematical modeling may be limited to comparing the effect of design changes or differences in design elements on the relative rather than absolute performance.

Laboratory tests are typically con-ducted at steady fl ow rates. It should be recognized that the non-steady fl ow characteristics of stormwater may decrease the effi ciency from what may be estimated or determined from testing under constant fl ow. The examination of one product found that it had low separation capacity for 1 to 25 microns, but this result is certainly applicable to all the small vault prod-ucts. It was also determined that the particle size distribution had a greater infl uence on performance than fl ow rate. This suggests that non-steady fl ow is of less concern.

For CSOs the practical lower limit of vortex separation is a particle with a settling velocity of 12 to 16.5 feet per hour (0.10 to 0.14 centimeter per second). As such, the focus with CSOs has been with settleable solids generally 200 microns and larger, given the presence of organic solids. For inorganic solids, the above settling velocity range represents a particle diameter of 50 to 100 microns. Swirl concentrators are therefore generally perceived to be limited to the removal of sand and silt down to about 50 microns. Some clay and smaller silt is also removed, but only to the extent of the volume of fresh dirty water captured during each storm, which is small relative to the total storm volume that enters the unit over time. These very small particles will be lost from the vault at higher fl ow rates. The improved performance of swirl concentrators over direct-entry vaults

is more likely due to several factors other than vortex separation. The fi rst is improved hydraulic effi ciency. It is possible that a swirling motion is more hydraulically effi cient than that in direct-entry vaults. Better hydraulic effi ciency results in a condition closer to the theoretical hydraulic loading rate. The second is particles striking the wall. The third is the increased fl ow path, which increases the oppor-tunity for strikes.

FlotationMaterial lighter than water includes petroleum hydrocarbons, paper, ciga-rette butts, and plastic bags. Although fl otation can remove litter, a common practice is screening. The focus of this section is oil/water separators. Petro-leum is present in fi ve forms, three of which are removable: free, dispersed, and sorbed oil. Dispersed hydrocar-bons are small droplets, 10 to 100 microns. Most sorb to suspended solids and settle rather than fl oat.

Free and dispersed oil concentra-tions are typically less than a few mil-ligrams per liter. Nonetheless, this small amount produces a sheen, which many regulatory agencies dissallow. The two remaining forms are not removable by fl otation. Oil chemically stabilized by a surfactant such as detergent is not removable with standard separators. Dissolved oil is removable only by sorptive fi ltration but is a very small fraction in stormwater.

Sizing separators is based on Stokes Law. As the specifi c gravity is less than one, the settling velocity is negative and is called the rise rate. The rise rate is analogous to the hydraulic loading rate. To size a separator, the droplet size is selected such that removing it and all larger droplets provides the desired removal effi ciency. Other criteria are the specifi c gravity of the petroleum product and the operating temperature. The specifi c gravity of fresh motor oil is 0.88 at 20˚C (68˚F), although weathering alters this value. It should be higher when it washes from pavement, because the oil would have weatherized to some extent. The mean January temperature is selected in northern latitudes as it represents the time of year when the rise rate is


the lowest—typically January in wet climates. Given the presence of snow throughout the winter, April may be the best for these cold climatic areas. The mean July temperature would be used in the southern hemisphere.

To illustrate: droplet size of 80 microns, temperature of 10˚C (50˚F), and specifi c gravity of 0.88 give a rise rate, Vp, of 3.6 feet per minute (1.2 meters per minute). The rise rate is determined using Stokes Law. All droplets equal to or greater than 80 microns are removed, or about 90%. For the design fl ow, Q, the required surface area, A, of the separator is shown in Equation 1.

A = Q/Vp (Equation 1)The types of oil/water separators

include API, CP, and sorptive. The API (American Petroleum Institute) sepa-rater is a wet vault with baffl es at the entrance and exit. Because of generally poorer performance and large space requirements of the API separator, the coalescing plate (CP) separator is commonly used. A CP separator is a

wet vault with laminar plates, using the same concept as previously described. Cost of the plate system is offset by the lower cost of a smaller vault. Given their very large size, API separators are not generally used. API separators are ineffective with droplets smaller than 150 microns, whereas CP separators remove much smaller droplets.

Coalescing refers to the aggregation of oil droplets as they rise, induced by contact with the plates. There are other forms than plates that serve the same function. The third concept found in newer products is sorptive fi lter media. Some products use CP and sorptive media. As a CP separator is essen-tially a stack of shallow basins, the most effi cient confi guration is a stack of horizontal plates. However, plates are sloped to promote self-cleaning of sediment. An oil/water separator removes suspended solids as well as oil. A separator designed for a rise rate of 3.6 feet per hour also removes all particles with the same and greater settling rate. This settling velocity

represents inorganic particles of 20 to 35 microns. The angle to the horizon-tal, q, is generally between 45 and 60 degrees. Plate separation is one-half to three-quarters of an inch. The effec-tive area is the horizontal projection of each plate. The total plate area, Ap, is determined by Equation 2.

Ap = A/Cosine(q) (Equation 2)Litter must be removed to prevent

clogging of the plates. While pretreat-ment with a wet pool may adequately remove litter, more sophisticated devices may be needed for adequate protection.

Gary R. Minton, Ph.D., P.E., is a consultant on stormwater treatment and the author of the book Stormwater Treatment: Biological, Chemical, and Engineering Principles.

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The Colorado School of Mines located in Golden, CO, was established in the 1870s and reflects the importance of the

area’s abundant natural resources in its curriculum, with courses in mining engineering, geology, chemistry, min-eralogy, metallurgy, botany, math, and drawing. With this history in mind and an ingrained respect for the natural environment, the institution’s Cam-pus Facilities Master Plan called for the renovation and new addition of Brown Hall and the surrounding hard-

scape and landscape to meet LEED Silver certification.

In conjunction with the construc-tion of the new Brown Hall addi-tion, which was built to house the engineering and mining engineering

departments, the school wanted to create a beautiful yet functional pedestrian environment, where asphalt streets had previously been at the heart of the Colorado School of Mines campus. Mathew Evans,

PROJECT PROFILE

Achieving Silver at Brown Hall

Colorado School of Mines Maple Street pedestrian mall


RLA, ASLA, LEED-AP, of the land-scape architecture fi rm Lime Green Design in Denver, CO, was the project designer for this aspect of the project.

“The area around the new addition to Brown Hall had to accommodate a high volume of pedestrian traffi c, and as part of the campus master plan, an adjacent street was to be vacated and pedestrianized,” he notes.

The pavement solution not only needed to accommodate the loading of emergency and service vehicles, but also to avoid exceeding historic offsite stormwater fl ows on the site. In addi-tion, the pavement had to meet the campus maintenance requirements for a long-lasting, durable surface.

Evans adds, “An unanticipated second phase of the project became possible, which led to the pedestri-anization of another section of street. The success of the fi rst phase resulted in an extension of the use of the pavers in this new area. As part of the master plan, a preliminary study has identifi ed another two blocks of city street extending out from the original Brown Hall project, which will eventually be vacated, and the plan currently shows the continued use of permeable pavers in this new pedes-trian spine.”

Landscape designer Evans worked with installer JC Coniff of Rocky Moun-tain Hardscapes LLP and Colorado School of Mining facilities manager Bob Slavik on the selection and installation of 35,000 square feet of Eco-Priora permeable interlocking pav-ers manufactured by Pavestone LLC, a Uni-Group USA paver producer. The pavers complement the natural beauty of the site and met the necessary criteria for durability, with patented interlocking spacers that provide supe-rior structural stability under loads, as well as permeability to help manage stormwater fl ows. The designer and contractor worked together on details such as integration of the pavers and concrete collars around utility man-holes and valve covers.

The permeable pavement aspect of the project presented a number of challenges for the designer. There was an initial institutional resistance

to the use of a permeable pavement that had to be overcome. Techni-cal challenges included slopes in excess of 8% and concerns regard-ing traffi c loading from fi re trucks, service vehicles, and the occasional 18-wheelers delivering to the site. A portion of the site has no avail-able stormwater infrastructure, so any system used had to be designed to infi ltrate the area design storms, and water could not migrate into the subgrade within 10 feet of the face of the building. Moreover, with an average snowfall of over 5 feet per year, the Eco-Priora pavement had to be durable enough to withstand snow plowing and the use of deicers.

In addition, the construction schedule was dictated by the school year so as not to interfere with students and vehicles crossing the campus.

Evans notes, “The provision of product data, other project references, and site visits, along with meetings with the design team and paver reps, provided the assurances the school needed to proceed with permeable pavers. Selection of a contractor with suffi cient experience and credentials was critical to the project success, since a number of installation chal-lenges had to be addressed in the fi eld for a satisfactory outcome.”

Once the school was convinced of the viability of the permeable pave-ment system, design and construction of the project got underway. In areas

where the slopes were under 5%, a typical paver cross-section featuring partial infi ltration and 4-inch-diameter perforated pipe was used. Where the slopes exceeded 5%, site-specifi c detailing was required, including subsurface check dams and subdrains. In areas adjacent to the building, an impermeable PVC liner was included to protect the building foundation from surface water infi ltration.

Aggregate materials used in the pave-ment cross-section were specifi ed as ASTM #8 or #9 for the joint and bedding materials, ASTM #57 for the base, and CDOT #3 or #4 for the sub-base, which is equivalent to ASTM #2 or #3. Subgrade soils at the site consisted of mostly clayey sands. In addition, an electric snowmelt system was incorporated into the pavement design at building entrances.

Evans worked in collaboration with the building architect, Anderson Mason Dale of Denver, CO, to design a pavement pattern with charcoal bands in a tan fi eld laid in a her-ringbone pattern on most of the site. A former traffi c circle became the main intersection of walkways, where lighter-colored pavers were used for some of the bands in the radial pat-tern to meet the LEED Heat Island Effect credit.

Originally a LEED Silver certifi ca-tion was the goal; however, with the inclusion of the Eco-Priora permeable paver system, Brown Hall achieved LEED Gold certifi cation.

Site plan


“The building addition and site was LEED registered,” says Evans, “and the paving system helped obtain the Heat Island Effect and Stormwater credits. Ideally the selected pavement system would also contribute to the LEED Regional Materials and Content credits.”

The paver colors were specifi cally selected to meet the solar refl ec-tance values, allowing the project to achieve the LEED credit SSc7.1 Heat Island Effect—Non-roof. The perme-able paver system also contributed to Stormwater Management Quantity Control Credit 6.1; Stormwater Man-agement Quality Control Credit 6.2; and Regional Materials Credit 5.

The project also was the recent winner of an HNA Hardscape Award for the Concrete Paver—Commercial/Industrial Permeable category. The HNA Hardscape Project Awards are produced by the Interlocking Concrete Pavement Institute and supported

Above: The original asphalt street before conversion to a pedestrian plaza

Below: Lighter-colored pavers helped the project with the LEED heat island credit.


by the National Concrete Masonry Association and the Brick Industry

Association. The Hardscape Project Awards recognize outstanding hard-

scape projects by contractors building residential walkways, patios, driveways, commercial plazas, parking lots, and streets. Entries are judged on project intent, design, quality of construction and craftsmanship, compatibility with related construction materials and sys-tems, construction innovation, detail-ing, and overall design excellence.

The Colorado School of Mines Brown Hall project is intended to create a precedent for future projects on campus. By converting asphalt streets to beautiful permeable paver pedestrian-oriented areas that are also capable of supporting traffi c loads, the school is embracing low-impact, sustainable, environmentally benefi cial design.

For related articles: www.stormh2o.com/project-design

Workers screed bedding aggregate and install pavers in a 90-degree herringbone pattern.

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Designing Effective Sediment Containment Systems for Roadways ProjectsJerald S. Fifield, Ph.D., CISEC, CPESC & Tina R. Wills, PE, CISEC, HydroDynamics Inc.Wednesday, December 4 1 PDH / 0.1 CEU

Join Jerry Fifield and Tina Wills to explore a scientific and engineering assessment of parameters necessary to capture suspended particles while flood flows are discharging from a containment system.

Limitations of Commonly Found Roadway Construction Site Sediment Control BMPJerald S. Fifield, Ph.D., CISEC, CPESC & Tina R. Wills, PE, CISEC, HydroDynamics Inc.Wednesday, December 11 1 PDH / 0.1 CEU

Join Jerry Fifield and Tina Wills to explore temporary BMPs, their limitations (e.g., barrier BMPs), and the principles and practice in assessing and evaluating the effectiveness of barrier BMPs.

Making Erosion Control BMPs Work on Roadway ProjectsJerald S. Fifield, Ph.D., CISEC, CPESC & Tina R. Wills, PE, CISEC, HydroDynamics Inc.Wednesday, December 18 1 PDH / 0.1 CEU

Join Jerry Fifield and Tina Wills to explore the available erosion control methods and diversion structures, as well as how to develop seed mixtures, calculate fertilizer rates, and evaluate TRMs in drainage channels.

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IN-SITU INC.In-Situ Inc.’s new smarTROLL Rugged Dissolved Oxygen (RDO) Handheld Instrument and Smartphone Application simplify stormwater monitoring and dissolved oxygen (DO) spot checks. No training time is required to use the smarTROLL Probe or the intuitive smartphone app. Results are wirelessly transmitted to an iOS device—no bulky handheld meter is required. Users can e-mail data, log data to a smartphone, or export a data log to a standard file format. Site details can include geotags and photos for quick identification of sampling locations. Results for DO, barometric pressure, water temperature, and air temperature are displayed simultaneously on a smartphone.

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FORESIGHT PRODUCTSLabor and time-saving drive-type DUCKBILL earth

anchors are composed of corrosion resistant aluminum alloy to give the ultimate mechanical strength and extreme durability for a variety of soil stabilization

applications. The anchors offer a wide range of solutions for light to medium applications. Each solution can be

customized to meet specific needs, and the installation process involves three simple steps: drive, load, and set.

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STEWART-AMOSThe Galaxy R-6 regenerative air street sweeper is mounted on a compact, fuel-efficient, and highly maneuverable non-CDL chassis. It comes with a 6+ cubic-yard debris hopper and right gutter broom camera that can eliminate the need for dual steering. The hopper is made from easily replaceable bolt-together stainless steel panels, which come with a 5-year, no-rust factory warranty. A top hopper door opens during dumping to make screen and hop-per cleaning quicker, safer, and easier. www.stewart-amos.com

FILTREXX INTERNATIONAL LLCFiltrexx Trinity LivingWall combines innovative engineering from The Living Wall Company with the proven performance of Tricon wire forms and Filtrexx Bank Stabilization technol-ogy. It can be used to stabilize extreme inclines while providing a broad range of design and planting options. Tricon wire has been used for years in areas where an MSE wall is required. Filtrexx uses a high-quality Filtrexx GrowingMedia inside a tubular mesh to quickly establish permanent vegetation, whether established from seeds, sprigs, plugs, or bare root plants. The Filtrexx system delivers a measured, quality controlled, proven growth medium not available in other systems. www.filtrexx.com

49November/December 2013www.stormh2o.com

ARCADISARCADIS is a leading international company providing consultancy, design, engineering, and management services in infrastructure, water, environ-ment, and buildings. The company enhances mobility, sustainability, and quality of life by creating balance in the built and natural environments. ARCADIS develops, designs, implements, maintains, and operates projects for companies and governments. With 22,000 employees and more than $3.3 billion in revenues, the company has an extensive global network supported by strong local market positions. www.arcadis-us.com

MODULAR WETLAND SYSTEMS INC.The Modular Wetland System Linear is the only stormwater system to utilize Horizontal Flow Biofiltra-tion. The MWS Linear replicates natural processes to remove a variety of pollutants from stormwater runoff including fine TSS, bacteria, oils and grease, heavy metals, and harmful nutrients like nitrate and phos-phorus. While most systems utilize a single treatment method, the MWS Linear incorporates screening, hydrodynamic separation, sorbtive media filtration, and bioretention into a single system. Completely modular, the MWS Linear can either replace standard stormwater inlets or function perfectly in an online or offline design to replace downward flow systems. www.modularwetlands.com

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LANE ENTERPRISESThe Lane Reverse Q Pond Outlet represents a significant advance in pond outlet technology. It improves downstream water quality by managing both pond discharge quality and quantity. Because the RQ suspends the outlet orifice a few inches below the surface, it discharges from the highest quality water in the pond. In addition, by automatically varying the depth of the orifice according to the inverse of pond depth, peak dis-charges are delayed until after halfway through the specified drawdown period. This reduces downstream flooding potential at times when down-stream flows are at their highest levels. A sizing calculator is available. www.lane-enterprises.com

THIRSTY DUCK LTD.Thirsty Duck Buoyant Flow Control Devices (BFDs) function as floating outlets capable of delivering a constant flow rate by gravity, regardless of water surface elevation. When sized for the optimum discharge rate, detention volume can be minimized by as much as 50%! Thirsty Duck BFDs are university-tested, self-skimming, easily pass common debris, and are made from materials specially selected for the stormwater sys-tem environment. They are also approved for use by the Florida, Washing-ton, Massachusetts, and New York Departments of Transportation. www.thirsty-duck.com

TIDEFLEX TECHNOLOGIESMany potable water tanks or reservoirs depend on a typical common inlet/out-let to maintain drinking water quality. This system often proves inadequate when water outside the common inlet/outlet area of influence becomes stagnant, creating dead spots where bacteria are likely to multiply. Tideflex Technologies’ Tideflex Mixing System (TMS) greatly improves the quality of drinking water in finished water storage reservoirs. The TMS is a combination of patented Tideflex Check Valve technology and a piping manifold that separates the inlet and outlet. The TMS can be installed in new or existing water storage tanks of all shapes and sizes to eliminate stagnation and short-circuiting. www.tideflex.com

BARRIER SYSTEMS INC.The SandMaster is an attachment that quickly fills, transports, securely closes, and places multiple sandbags where they are needed. It’s capable of creating and placing 15,000–18,000 sandbags in a 24-hour period, and is the ideal system for erosion control, flood control, spill containment, or any use where the bagging of materials is needed. It works great with most materi-als, wet or dry, allowing the use of what’s available onsite and reducing labor while saving both time and money. www.barriersystemsllc.com

51November/December 2013www.stormh2o.com

US SAWSUS Saws recently announced the addition of the Robotron Manhole removal tool to their Break ’N Take line of magnetic lifting products. This newest model incorporates a patent-pending fulcrum that pro-vides a mechanical advantage over other magnetic lifters and provides for easier lifting and removal of most manhole covers. In addition to the pivoting base, the Robotron’s floating magnet design provides more secure contact with uneven surfaces. The Robotron uses three magnets with a 400 maximum pound lifting capacity. US Saws Break ’N Take Lifters are light-weight, compact, and convenient to use. www.ussaws.com

TECHNICAL ABSORBENTSPermeatecDS is a new acrylate-based polymer system. It can be applied as an aqueous surface spray to dust and loose, granular materials as a means of suppression or to provide a hard, durable surface. PermeatecDS is specifically designed to be dispersed in water, aiding application and improving safety and handling. It is able to coat and bind loose materials, forming a complex web of interlocking particles and polymer, which when dried, forms a hard, durable material. The ability to change application rates provides the user with precise control and allows stabilization levels, strength, and durability to be tailored as required. www.techabsorbents.com

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ForesterPress is seeking book proposals and manuscript submissions on current topics of high interest to civil engineers; municipal infrastructure professionals; consultants; industry professionals responsible for meeting soil, water, and energy compliance standards; academics; and other environmental-quality professionals.

We publish practical, progressive, reference, and professional development books in the following subject areas:

Stormwater Management • Soil Erosion and Sediment Control • Construction-Site Compliance and Best Management Practices • Solid Waste Management • Water Efficiency and Conservation • Onsite Energy Management

We offer generous royalties, high production quality, and effective marketing campaigns that target your book’s intended audience.

To submit your book proposal: Include a detailed description of the content, an annotated table of contents and a comprehensive outline, a sample chapter on the book’s topic, your curriculum vitae, and the names of recommended reviewers to:

Acquisitions EditorForesterPress PO Box 3100 Santa Barbara, CA 93130Phone: 805-682-1300 Fax: [email protected]

SEEKING BOOK PROPOSALS

FP_Publish_11_.5p REFERENCE RESOURCES FOR INFRASTRUCTURE PROFESSIONALS www.forester.net

FORESTER

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JERALD S. FIFIELD, PH.D, CPESC, CISECJERALD S. FIFIELD, PH.D, CPESC, CISEC

52

SHOWCASE


Showcase is based on information supplied by manufacturers. Some manufacturers did not respond to requests for information. Publication of materials received is subject to editing and availability.

PAVEDRAIN LLCThe PaveDrain System is an aesthetically pleasing Permeable Articu-lating Concrete Block/Mat (P-ACB/M) that provides installation ease and design flexibility for owners, engineers, and contractors. The PaveDrain System infiltrates more stormwater per 1 foot diameter than any other hardscape permeable surface. The joints between the blocks are left open for little to no maintenance. It is available in col-ors and is ADA compliant and AASHTO HS-20 and H-20 load tested. www.pavedrain.com

OLDCASTLE PRECASTTo detain stormwater runoff at the Metro Fire Station #21, the Met-ropolitan Government of Nashville and Davidson County elected to remove an aboveground detention pond and construct an under-ground stormwater detention system to gain back valuable land for parking during the recent replacement of the facility. In the final design, Oldcastle Precast’s Storm Capture stormwater manage-ment system was chosen and subsequently constructed under the entrance road, since it reduced the detention system width and overall footprint by over 40%, and easily fit under the fire station roadway. www.oldcastleprecast.com

SEALING SYSTEMSFlex-Seal Utility Sealant is a state-of-the-art plural component aromatic urethane with an incredible 800% elongation and a tensile strength of 3,200 psi. Flex-Seal is designed to prevent inflow/infiltra-tion and to provide corrosion protection at the grade adjustment ring section or joint section. Flex-Seal Utility Sealant provides an excellent seal, and it will pass a vacuum test according to ASTM standards. www.ssisealingsystems.com

SOLINST CANADA LTD.The Model 101 P7 Water Level Meter features extremely durable PVDF flat tape, with high tensile strength and electrical efficiency. Laser tape markings are every 1/100 ft or mm, certified traceable to national standards. The P7 Probe is submersible to 1,000 ft. (300 m). The sensor at the tip of the probe provides consistent measurements in wells, tanks, surface water, and even cascading water, with almost zero displacement. The sturdy reel is made for water level measurement in rugged environments.www.solinst.com

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May 2013 | www.stormh2o .com


May 2013 | www.stormh2o .com

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Case studies often examine the potential problem-solving nature of products such as speed of instal-lation, labor savings, and

the like. But when it comes to perfor-mance, it is often expressed by con-tractors or building managers in terms of expectations for the future, thereby remaining a mystery as to how the product fared months or even years later. In this case, however, a paver project was recently revisited six years after the pavers were installed and tested side-by-side with traditional concrete pavers.

The University of Minnesota Duluth (UMD) had selected AZEK permeable pavers for a project six years ago. The difference of these recycled-content alternatives compared to traditional con-crete pavers is clearly visible: no signs of cracks and minimal wear and tear, damage, and color change. The con-crete pavers installed at the same time, however, had buckled and raised up on one side, showing cracks and wear.

UMD’s need for a permeable solu-tion came about when the university was constructing a new civil engineer-ing building and wrestled with how to manage stormwater runoff on impervi-

ous surfaces around the building; the campus is located on a designated trout stream that drains into Lake Superior. The university’s stormwa-ter pollution prevention program required stormwater treatment, and the designer suggested AZEK perme-able pavers for their water infi ltration properties (made possible by spacer lugs on the sides of the pavers) up to 95% recycled content. The pavers are composed mostly of scrap auto tires, along with some plastics, and make it easier to attain LEED points than traditional pavers. In fact, AZEK pavers’ manufacturing to date has diverted

Comparing Paver Performance at the University of Minnesota

PROJECT PROFILE


sion of UMD’s plumbing shop where truck deliveries are made. Erik Larson, an engineer at UMD, explains that this was an appropriate test area because it had poor drainage and was frequently muddy after heavy rains; it receives vehicle, forklift, and truck traffi c. Set into their 16- by 16-inch interlocking grids, AZEK permeable pavers were installed next to traditional concrete pavers on the same engineered base.

The second area was a 75-square-

foot triangular area outside UMD’s Sports and Health Center, where the unloading of sports teams and student foot traffi c took a toll on the ground. Despite attempts by the Building and Grounds Division of Facilities Manage-ment to landscape the space, students kept cutting through it. It provided a good proving ground to see how the new permeable pavers handled foot traffi c in winter conditions.

After a tough Minnesota winter in

more than 10 million pounds of scrap rubber and plastics from US landfi lls, using recycled material from more than 535,000 scrap tires and 16 million plas-tic food containers and DVD cases. The manufacturing process also uses 95% less energy and produces 96% less in carbon dioxide (CO2) emissions than conventional pavers.

The big question was how they would perform in sub-freezing Min-nesota temperatures, with repeated freeze-thaw cycles, the scraping of snow plows, the snow itself, and the salt used for deicing. Top it off with heavy truck traffi c in a loading dock area and it presented an all-out challenge for a new paver technology versus the traditional pavers. Another question was how AZEK pavers would manage the rainwater runoff.

According to Mindy Granley, UMD’s sustainability coordinator, the area’s soil has a high clay content and is not conducive to absorbing water. “Rain-water from the campus can get down from the top of the hill to Lake Superior in just 10 to 15 minutes,” she says. She

points out that impervious surfaces can affect water quality and that by control-ling the volume and speed of the water fl ow, pollution and erosion are reduced.

The AZEK paver versus concrete paver test was set up in two high-traffi c areas. The fi rst was a 600-square-foot loading and storage area, an expan-

AZEK and concrete pavers side by side

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Join industry experts Jerald Fifield and Tina Wills for a comprehensive, six-part live and on-demand master class and workshop series exploring the ins and outs of effective sediment and erosion control plan design and review for roadway projects. Enjoy six online lectures and Q&A sessions and three interactive workshops presented by Fifield and Wills, delving into Fifield’s best-selling third edition of Designing and Reviewing Effective Sediment and Erosion Control Plans (included in your Master Class Series package) and focusing on the specific sediment and erosion control needs, challenges, and best practices for roadway projects. Sessions include:

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Nov. 26 Determining Performance Goals and Effectiveness of Roadway Sediment and Erosion Control Plans

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Dec. 11 Limitations of Commonly Found Construction Site Sediment Control BMPs

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spring 2008, UMD deemed the test to be favorable for the permeable pavers. Unlike concrete in the same areas, AZEK pavers showed no cracks or color fading. Facilities Management went on to add 990 square feet of pavers in the Civil Engineering build-ing’s loading dock area. UMD also kept the test installation.

Six years later, UMD is still encour-aged by the new pavers’ performance in all three locations. Whereas the concrete pavers took more of a beating from traffi c and snow and ice control, AZEK permeable pavers look more like the day they were installed.

According to Granley, they have proven to be an effective solution to UMD’s soil conditions as well as stand-

ing up to extreme winter conditions—both natural and manmade. Larson agrees, adding, “We do intend to use the pavers on future projects.”

In the fall of 2007, when UMD tested the new paver technology against traditional concrete pavers, the product was a recent invention, available only regionally and through architect specifi cation. In fall 2011, VAST Enterprises entered a strategic alliance

For related articles: www.stormh2o.com/project-design

Avg. No. Copies Each Issue During Preceding 12 Months

No. Copies of Single Issue Published Nearest to Filing Date

a. Total No. Copies 22,265 24,242b. Legitimate Paid/Requested Distribution:

(1) Outside County Paid/Requested Mail Subscriptions Stated on PS Form 3541

21,219 21,011

(2) In-County Paid/Requested Mail Subscriptions stated on PS Form 3541

0 0

(3) Sales Through Dealers and Carriers, Street Vendors, Counter Sales, and Other Paid or Requested Distribution Outside USPS

0

0

(4) Requested Copies Distributed by Other Mail Classes Through the USPS

16 26

c. Total Paid/Requested Circulation 21,235 21,037d. Nonrequested Distribution:

(1) Outside County Nonrequested Copies as Stated on PS Form 3541

362 465

(2) In-County Nonrequested Copies as Stated on PS Form 3541

0 0

(3) Nonrequested Copies Distributed Through the USPS by Other Classes of Mail

0

0

(4) Nonrequested Copies Distributed Outside the Mail 341 2,300

e. Total Nonrequested Distribution 703 2,765f. Total Distribution 21,938 23,802g. Copies Not Distributed 327 440h. Total 21,265 24,242i. Percent Paid/Requested Circulation 96.8% 88.3%

I certify that all information furnished on this form is true and complete.Dan Waldman, Publisher 9/4/2013

STATEMENT OF OWNERSHIP, MANAGEMENT, AND CIRCULATION1. Publication Title: Stormwater. 2. Publication No.: 1531-0574. 3. Filing Date: October 1, 2013. 4. Issue Frequency: Bimonthly with extra issues in May and October. 5. No. of Issues Published Annually: Eight. 6. Annual Subscription Price: $76. 7. Complete Mailing Address of Known Offi ce of Publication: 2946 De la Vina Street, Santa Barbara, Santa Barbara County, CA 93105. Contact Person: Daniel Waldman, 805-682-1300. 8. Complete Mailing Address of Headquarters or General Business Offi ce of Publisher: 2946 De la Vina Street, Santa Barbara, Santa Barbara County, CA 93105. 9. Full Names and Complete Mailing Addresses of Publisher, Editor, and Group Editor: Publisher, Daniel Waldman, 2946 De la Vina Street, Santa Barbara, CA 93105; Editor, Janice Kaspersen, 2946 De la Vina Street, Santa Barbara, CA 93105; Group Editor: John Trotti, 2946 De la Vina Street, Santa Barbara, CA 93105. 10. Owner: Forester Media Inc., 2946 De la Vina Street, Santa Barbara, CA 93105; Daniel Waldman, 2946 De la Vina Street, Santa Barbara, CA 93105. 11. Known Bondholders, Mortgagees, and Other Security Holders Owning or Holding 1% or More of Total Amount of Bonds, Mortgages, or Other Securities: None. 12. Tax Status: The purpose, function, and nonprofi t status of this organization and the exempt status for federal income tax purposes has not changed during preceding 12 months. 13. Publication Title: Stormwater. 14. Issue Date for Circulation Data Below: September 2013. 15. Extent and Nature of Circulation:

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with AZEK Building Products, known for its low-maintenance line of premium exterior building products. In December 2012, AZEK bought out the company, and AZEK pavers are now available nationally through lumber dealers that carry AZEK products, greatly expanding the market for the pavers.

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COMPANY URL PAGE


ADVERTISER’S INDEX

MARKETPLACE

American Peat Technology LLC. . . . . . . . . . . . . . . . . . . . . . www.americanpeattech.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

AP/M Permaform . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.permaform.net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Best Management Products . . . . . . . . . . . . . . . . . . . . . . . www.bmpinc.com. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Crumpler Plastic Pipe Inc. . . . . . . . . . . . . . . . . . . . . . . . . www.cpp-pipe.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

DOGIPOT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.dogipot.com. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Filterra Bioretention Systems . . . . . . . . . . . . . . . . . . . . . . . www.filterra.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cover 2

Filtrexx International LLC . . . . . . . . . . . . . . . . . . . . . . . . . www.filtrexx.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cover 4

Five Star Products Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . www.fivestarproducts.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

IN-SITU Inc. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.in-situ.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Invisible Structures Inc. . . . . . . . . . . . . . . . . . . . . . . . . . www.invisiblestructures.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

IPEX Inc.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.ipexinc.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

J.W. Faircloth & Son . . . . . . . . . . . . . . . . . . . . . . . . . . . www.fairclothskimmer.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Lane Enterprises. . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.lane-enterprises.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Modular Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.modularwetlands.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

North American Society for Trenchless Technology (NASTT) . . . . . . . . www.nodigshow.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Oldcastle Precast- Specialty Products . . . . . . . . . . . . . . . . . . www.oldcastleprecast.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Plastic Solutions Inc . . . . . . . . . . . . . . . . . . . . . . . . . . . www.plastic-solution.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Precision Pipe & Products Inc. . . . . . . . . . . . . . . . . . . . . . . www.precisionpipe.com. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Stewart-Amos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.stewart-amos.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

StormTrap LLC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.stormtrap.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Stormwater Equipment Manufacturers Association (SWEMA) . . . . . . . www.stormwaterassociation.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Taipei Economic & Cultural Office in Los Angeles - Press Division . . . . . www.taiwanembassy.org/US/LAX/mp.asp?mp=52 . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Thirsty Duck LP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.thirstyduckinc.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Triton Stormwater Solutions . . . . . . . . . . . . . . . . . . . . . . . www.tritonsws.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Tymco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.tymco.com . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

UF Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . www.ufedge.ufl.edu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Lowest maintenance and highest infiltration rate of any hardscape permeable system.

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READER PROFILE


BY CAROL BRZOZOWSKIAlexandra Dunn

As a young girl growing up in Westchester County, NY, Alexandra Dapolito Dunn would cross the Hudson River almost daily in a school bus. “I have strong memories of looking at that body of water,” she recalls.

She left the area at nine years old, and returned at 40. “I had my own family and was able to expose them to that watershed, and as an adult I had the chance to interact with dozens of passionate advocates for the ecosystem,” says Dunn. “I was part of an academic institution and collaborated with many other col-leges and universities to protect, restore, and bring the Hudson back to a healthy status.”

Today, Dunn is executive director and general counsel of the Association of Clean Water Administrators—a national, nonpar-tisan organization of state, interstate, and territorial offi cials responsible for implementing surface water protection programs, facilitating communication with the federal govern-ment, and promoting public education. In the past 11 years of Dunn’s 18 years of experience in environ-mental law and policy, she’s focused her efforts on water quality, water treat-ment, and implementation of the Clean Water Act. She writes and speaks about water policy, sustainability, and environmental justice; lectures about law at the Columbus School of Law and Catholic University of America; and is an advisor to the Environmental Law Society. She chairs the American Bar Association’s Section of Environment, Energy, and Resources; serves on the Environmental Law Institute’s board of directors; and serves as secretary of the US Water Alliance.

What She Does Day to Day A typical day for Dunn may involve a meeting at EPA head-quarters, calls to individuals running clean water programs in a half-dozen states, as well as interacting with her staff and interest groups in Washington DC devoted to the cause of clean water.

What Led Her to This Work It was her involvement in Girl Scouts—which gave her many opportunities to be out in the ecosystem—that instilled in Dunn a love for the outdoors and a desire to pursue a career to protect it. She earned her B.A., cum laude, in political science and French at James Madison University and her J.D., magna cum laude, at Catholic University of America, where she was

the Law Review’s editor-in-chief. During an internship at a Washington DC law fi rm, she worked with the environmental practice group, meeting people doing what she wanted to do: combine the power of words and persuasion with a passion for the outdoors to enact change.

What She Likes Best About This Work“It’s very results-oriented,” says Dunn of her job. “Although achieving the goal of the Clean Water Act is a multi-decade goal,

I see small steps daily along that journey, whether it’s a letter to Congress asking for greater funding for clean water, a meeting with EPA where a diffi cult issue is massaged, or providing someone some information. We are making progress to clean up water in the US.”

Her Greatest ChallengeKeeping her organization’s head above water with a staff of fi ve and providing the best service possible is Dunn’s greatest chal-lenge. “I don’t get a lot of sympathy for that, because my member state direc-

tors are also trying to do their jobs with not enough resources to maximize results in the near term,” she says.

Dunn is heartened by activities such as EPA’s integrated plan-ning initiative sequencing stormwater, clean water, and regula-tory obligations in a way that allows investments to be made at a reasonable pace; water quality trading programs; and green infrastructure innovations. “These small changes are designed to give our investment in clean water the greatest return,” she says. “That creativity was not as evident six years ago.” She’s also seen an exponential increase in collaboration among groups. “I see agricultural groups with different resources and tools work-ing closely with clean water groups and watersheds to improve the quality of rivers and streams. So much has happened in the years since I was crossing the Hudson River as a kid in the 1970s to when I came back in the mid-2000s. That period of my lifetime was one of incredible revitalization for that water-shed. I can say I’ve seen the Clean Water Act work.”

Carol Brzozowski specializes in topics related to stormwater and technology.

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THE JOURNAL FOR SURFACE WATER QUALITY PROFESSIONALS · 2020. 1. 20. · aged. After all, the SWPPP...

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