“Underground” Sustainability in Texas

Chris L. Schultz, P.E., PMPSeptember 27, 2013

• Per Wikipedia:

“The capacity to endure”• To the A/E/C industry it means designing and

constructing in a way that protects our natural resources, but by definition, it also means building something that lasts.

• When dealing with the underground, many times “Best Practices” with regard to natural resources are in conflict with building improvements that lasts.

Sustainability

• Sometimes subsurface conditions are:

In Texas

• Sometimes expansive.

In Texas

• How does that impact sustainability?

In Texas

• Low Impact Development Practices for Heavy Clay Soils; Fouad H. Jaber, PhD

• Urban Storm Drainage Criteria Manual, Volume 3; August 2011; Urban Drainage and

• Estimating the Economic, Energy, and Environmental Impact of Earthwork Activities; Lewis and Hajji, ASCE Construction Research Congress 2012

• Stormwater Management for Federal Facilities under Section 438 of the Energy Independence and Security Act; 2007; United States Environmental Protection Agency

• MGM/UA Entertainment Company

Acknowledgments

• Low Impact Development (LID) and Sustainable Design

• Subsurface Conditions in Texas• Pervious Pavements• Bioretention• Other “Underground” and Material Selection

Sustainability Considerations• Building Pad Construction• Recycled Materials• Warm-mix asphalt• Geothermal Heat Pumps

Agenda

• Sustainable stormwater management strategy

• Goal is to reduce runoff resulting from new development to reduce flooding, erosion and pollution

• Most “strategies” involve reducing impervious cover, collecting water and attempting to “put it in the ground”

Low Impact Development (LID)

• Utilized for many years in Asia and Europe

• Mandated on Federal Project under Section 438 of the Energy Independence and Security Act (2007) • Stormwater Management for

Federal Facilities

Low Impact Development (cont)

• EPA Website

• Impervious cover reductions

• Porous pavements• Vegetative practices• Cisterns• Green roofs

Low Impact Development Strategies

• Per 1973 study by Holtz, expansive soils cause more damage to buildings and infrastructure than any other natural phenomenon

• Expansive soil related movements greater than 4 in. and up to 12 in. are common in Texas

Expansive Soil Sites

• Expansive soils will exhibit swell pressures in excess of 10,000 psf, lifting lightly loaded, ground supported improvements

• When inundated, expansive soils ultimately loose their strength

• Expansive soils are “impermeable” which increases flooding

Expansive Soil Sites (cont)

Expansive Soil Sites

Expansive Soils

Expansive Soils

• The goals are diametrically opposed to one another

• Geotechnical engineers will want the water removed and removed fast

• Strategy is to prevent surface water from infiltrating the ground

LID vs Expansive Soil Sites

• Government wanted Integrated Management Practices (IMP):

• Permeable pavements• Excavate 4 ft. in landscape areas

and backfill with sand to hold water

CAPT. C. P. Miller, U.S. Army Quartermaster Corps, to the Quartermaster General, U.S.A., Washington, D.C.

“Sir, the following report is respectfully submitted in regard to the settling and cracking of buildings at Fort Sam Houston:

In spite of the system of drainage that has been put around the foundations, there is still much settling and an examination shows that in all cases where this trouble exists, there is a chance for the water to get in against the foundation walls from the surface.

Where the ground is properly graded from the building and the leaders and gutters are in good condition, there is little complaint. I would see no evidence to confirm the theory that the whole ground was sliding, and careful examination satisfies me that it is necessary to keep the surface water away from the buildings to make the foundation secure.”

January 18, 1894.

Ft. Sam Houston – Expansive Soils Win

Can they coexist?

LID and Expansive Soils

• Basic strategy is to construct pavements with materials that freely drain to allow movement of water into the layers below the pavement surface

• Reduces volume of runoff

• Underlying layers filter the water resulting in improved water quality

• Allows for slow release of stormwater

Permeable Pavements

Permeable Pavements

2

Permeable Pavements

Paver Blocks

Porous Asphalt

Porous Concrete

Turf Paver Expanded Shale Mix

• Can be utilized, but on sites with moisture sensitive subgrades, must be constructed as “No-Infiltration” pavements

• Good Guideline: Urban Drainage and Flood Control District (Denver), Urban Storm Drainage Criteria Manual, Volume 3, Chapter T-10, dated August 2011

Permeable Pavements in Texas

• Still reduces volume of runoff and allow for controlled release of runoff

• Underlying layers do filter the water resulting in improved water quality

• Must determine if other local stormwaterrunnoff requirements might prevent their use (aquifer recharge).

Permeable Pavements in Texas (cont)

No-Infiltration Section

Pipe Penetration Details - Critical

Geomembrane/Curb Detail - Critical

• A rain garden is a landscape feature consisting of a planted shallow depression that collects rainwater runoff from roofs, parking lot and other impervious surfaces

Bioretention – Rain Gardens

• Not recommended adjacent to structures• On clays subgrade sites, the clays

beneath will serve as a barrier which will trap water, so vegetation must be compatible to excess water

Landscape PlantsRedtwig Dogwood, Deciduous Holly, Larch, Red Maple, Elderberry

Annuals, Perennials, etc.Monarda, Physostegia, Goatsbeard, Astilbe, Turtlehead, Snakeroot, Meadow Rue, Ligularia, CardinalFlower, Forget-Me-Not (Brunnera) Spiderwort, Gooseneck Loosestrife, Ajuga, Balsam, Mimulus

• Where used in parking areas, you must protect base materials

Rain Gardens in Texas

Curb Detail for Landscaped Areas

• San Antonio Business Journal – April 15th, 2007: "You can't really say this is a sudden interest in the environment. It's been going on at least 30 years. In fact, the AIA had a national convention in 1993 on the subject of sustainability.” - Chris Schultz

– Chris Schultz, AIA

• Building pad construction• Recycled materials• Warm Mix Asphalt• On-site remediation of environmentally impacted

soils• Geothermal heat pumps

Other Subsurface/Material Sustainability Strategies

• According to National Institute of Building Sciences, site excavation and haul-off are the two highest contributors of CO2 emissions during construction projects.

• Recycling of materials and minimizing soil haul-off can significantly reduce the carbon footprint of the construction project.

• CO2 emissions are particularly high in clay excavations due to increased excavation efforts and total unit weight.

• In Texas, we tend to haul-off our problems, be it expansive soils, environmentally impacted soils, or construction debris.

• We can do better!

Excavation and Haul-Off

Excavations in Clay Soils

Source: Estimating Economic, Energy and Environmental Impactof Earthwork Activities – Lewis and Hajji, Construction ResearchCongress, 2012

• Most common way to deal with expansive soils is to over-excavate the upper expansive soils and backfill with imported select fill materials

• Site grading can be altered to reduce haul-off and “balance” the site, but the excavation, processing and transport of select fill materials has a major impact on the carbon footprint of the project

Building Pad Construction in Texas

• Other methods should be considered to treat on-site soils to reduce expansive potential and minimize import• Lime treatment of on-site clays• Cement treatment of on-site clays• Water treatment of on-site clays (be

careful)

• Chemical injection utilizing potassium based solutions – Added benefit of no excavation

Building Pad Construction in S. Texas

• Too much construction debris is hauled to landfills

• Concrete and/or masonry can be crushed and processed for use as base materials beneath pavements and building foundations

• TxDOT Specification Item 247 allows for crushed concrete for use as roadway base

Recycled Materials

• TxDOT Specification Item 3157 Cold Processed Recycled Paving Material (RPM) For Use As Aggregate Base Course

• Ceramics• Glass• Recycled Concrete….

• Recycled asphalt (RAP) becoming very popular

Recycled Materials (cont)

• Plant mix asphalt produced at lower temperatures while maintaining the workability required to be successfully placed

• Significantly reduced emissions • Aspha-min – North Carolina – 265oF

• 17.6% decrease in SO2• 3.2% decrease in CO2• 35.3% decrease in total hydrocarbons• 6.1% decrease in NOx

• Evotherm – Canada – 140oF• 45.8% decrease in CO2• 63.1% decrease in CO• 41.2% decrease in SO2• 58% decrease in NOx

• Direct comparisons are discouraged – different plants, different weather, different temperatures

Warm Mix Asphalt

Warm Mix Asphalt

Resource Recovery RemediationThe regulatory and physical transformation of environmentally affected materials from

a waste – to a resource – to a product

From Environmental Liability… … to Construction Asset

• Encapsulates environmentally impacted soils in asphalt pavements.

Benefits of On-Site Remediation•Cost effective

•Environmentally safe

•Reduced Carbon Footprint

•Less expensive than existing remediation practices

•Lowers overall operating costs

•Produces reusable specified materials

Resource Recovery Remediation

Resource Recovery Remediation

Before

Resource Recovery Remediation

After

Geothermal Heat Pumps

• Geothermal heat pumps are similar to ordinary heat pumps, but instead of using heat found in outside air, they rely on the stable, even heat of the earth to provide heating, air conditioning and, in most cases, hot water

• Significant advancement in this technology over the last five years making it more feasible for hot weather climates

• Studies show that approximately 70 percent of the energy used in a geothermal heat pump system is renewable energy from the ground

Geothermal Heat Pumps

• Alternative methods of building pad construction can significantly reduce the carbon footprint of a construction project

• Advances in recycled materials, warm mixed asphalt pavements and on-site remediation of environmentally impacted soils can significant reduce haul-off and lower CO2 emissions

• Advances are being made to determine how to use the constant ground temperature for long term energy reduction over the life of a structure

• Low Impact Development strategies can be implemented on Texas projects, but the devil is in the details

Conclusions

Questions