Industrial Stormwater Treatment along the Lower Duwamish Waterway Nathan Holloway Clear Water Services, LLC. Everett, WA Abstract This paper and subsequent presentation will focus on a showcase of industrial facilities located along the Lower Duwamish Waterway (LDW) that are utilizing active and passive treatment systems to comply with stringent water quality regulations. The LDW is known for legacy contamination due to decades of industrial activity and associated proximate runoff. The waterway is a 5 mile portion of the Duwamish/Green River which flows into Elliott Bay of the Puget Sound. In 2001, the EPA added the LDW site to the Superfund National Priorities List due to sediment contaminants such as Polychlorinated biphenyls (PCBs), Polycyclic aromatic hydrocarbon (PAHs), Phthalates and Mercury. Since then, the EPA, Washington Department of Ecology (Ecology) and other local agencies have led source control efforts to limit sediment pollution in the LDW prior to initiating further cleanup activities. Despite years of industrialization the LDW continues to remain critical habitat to many salmonid and supporting species which also continues to sustain Native Tribes. PHOTO #1: Duwamish Waterway looking toward Elliott Bay. Courtesy King County Wastewater Treatment Division
Transcript
Industrial Stormwater Treatment along the Lower Duwamish Waterway
Nathan Holloway Clear Water Services, LLC.
Everett, WA
Abstract
This paper and subsequent presentation will focus on a showcase of industrial facilities located along the Lower Duwamish Waterway (LDW) that are utilizing active and passive treatment systems to comply with stringent water quality regulations.
The LDW is known for legacy contamination due to decades of industrial activity and associated proximate runoff. The waterway is a 5 mile portion of the Duwamish/Green River which flows into Elliott Bay of the Puget Sound. In 2001, the EPA added the LDW site to the Superfund National Priorities List due to sediment contaminants such as Polychlorinated biphenyls (PCBs), Polycyclic aromatic hydrocarbon (PAHs), Phthalates and Mercury. Since then, the EPA, Washington Department of Ecology (Ecology) and other local agencies have led source control efforts to limit sediment pollution in the LDW prior to initiating further cleanup activities. Despite years of industrialization the LDW continues to remain critical habitat to many salmonid and supporting species which also continues to sustain Native Tribes.
PHOTO #1: Duwamish Waterway looking toward Elliott Bay. Courtesy King County Wastewater Treatment Division
North Boeing Field:
The North Boeing Field early action source control project was one of the first facilities required to install active treatment in an effort to reduce recontamination of PCBs into the LDW prior to commencement of dredging activities. Although significant source control efforts were employed by Boeing and the engineering team, the size and complexity of the aging conveyance infrastructure demonstrated the need for treatment to meet discharge targets established by the EPA. Chitosan Enhanced Sand Filtration (CESF) was one of many treatment technologies evaluated to meet the proposed discharge limits. A one year pilot system was deployed to demonstrate the effectiveness of the treatment technologies. The pilot study demonstrated that by constantly removing the suspended solids to below 10 nephelometric turbidity units (NTUs) the contaminants of concern could be reduced to levels acceptable to EPA to ensure recontamination of Slip 4 of the LDW would not reoccur. Specifically the PCBs were consistently removed to below 0.030 micrograms per liter. The pilot project also demonstrated the CESF would meet the water quality objectives of the project without utilizing a more traditional and expensive adsorptive media (such as activated carbon or ion exchange resins) as a polishing component to the treatment train. A full scale 1500-gallon per minute (gpm) CESF treatment system was installed in 2011 and has maintained compliance with the project’s early action plan. The project has been used as a case study in many other early action cleanup plans and other industrial treatment engineering designs along the LDW and the west coast.
PHOTO #2 (left): Threatened Coho Salmon harvested by local Native Tribes. Courtesy Duwamish River Project via You Tube
PHOTO #3 (right): Warning sign Posted to Public and LDW at low tide in the background. Courtesy Duwamish River Cleanup Coalition
Large Scale Bulk Recycling & Barge Loading Facility:
This facility is one of the largest high volume recycling and material handling facilities located along the LDW. The volume of material processed at this facility requires aggressive stormwater management BMPs including an active treatment system. The facility is currently discharging treated stormwater under an Ecology issued National Pollution Discharge Elimination System (NPDES) Industrial Stormwater General Permit (ISGP). A new individual NPDES permit is currently being drafted by Ecology which will likely include new interim discharge limits for copper and zinc. PCBs discharge limits are also expected to be added. The Fact Sheet associated with the permit also introduces proposed limits to be implemented in the future. Table 1 below summarizes the individual NPDES permit interim limits and proposed limits from the accompanying Fact Sheet:
PHOTO #4: North Boeing Field Long Term Treatment System nearing the completion of system installation during an EPA inspection. Courtesy: The Boeing Company
pH SU 6.00 9.00 6.00 9.00 a. Average monthly effluent limit means the highest allowable average of daily discharges over a calendar month. To
calculate the discharge value to compare to the limit, you add the value of each daily discharge measured during a calendar month and divide this sum by the total number of daily discharges measured.
b. Maximum daily effluent limit is the highest allowable daily discharge. The daily discharge is the average discharge of a pollutant measured during a calendar day. For pollutants with limits expressed in units of mass, calculate the daily discharge as the total mass of the pollutant discharged over the day. This does not apply to pH.
c. Total PCBs consist of 8 individual Aroclors. Limit concentrations are based off of a sum of the detected Aroclors.
The ISGP contains contaminant based “benchmarks” which require specific levels of corrective action if they are exceeded, however exceedance of the benchmarks is not necessarily a water quality violation as long as the appropriate level of corrective action is taken within acceptable timelines called out in the ISGP. The ISGP does call out a specific water quality “limit” for total suspended solids (TSS) when discharging to a Puget Sound Cleanup site, which includes and is characterized by the LDW. The individual NPDES permits typically include permit “limits” for all contaminants of concern listed in the specific permit. Exceedance of those “limits” is a violation of the water quality guidelines and can be subject to fines and additional regulatory action. In some cases, the individual NPDES permits can be a benefit to some industrial dischargers who have specific operational considerations or are able to utilize the mixing zone criteria to demonstrate water quality compliance at discharge concentrations above the “benchmarks” called out in the ISGP, however in general, permittees with individual permits and/or “limits” discharging to the LDW have more risk to manage and Ecology has essentially deemed those permittees as “high risk” in terms of stormwater discharge and source control management for potential recontamination of the LDW.
Since installation in 2012, the existing CESF treatment system has routinely met benchmarks in compliance with the ISGP but had shown occasional exceedances for total zinc due to fluctuations in pH and dissolved zinc influent concentrations. The CESF system was augmented with an automatic pH adjustment system to reduce the pH variability and effluent removal efficiency relative to zinc. Due to the increased risk associated with “limits” of the new individual permit, the facility elected to conduct an interim pilot study to evaluate the effectiveness and long term costs associated with additional adsorptive multi-media (AMM) options. The project team conducted a series of tests that compared four different AMM blends. Each blend or “treatment leg” accounted for approximately 2% of the total effluent volume in an effort to keep the pilot test costs to a practical level. The pilot test continued for 76 days and each “leg” processed approximately 875 bed volumes to fully evaluate the longevity of each media blend in comparison to the percent removal efficiency at each of six sampling events.
Figure 1: AMM Pilot Effluent Total Copper Concentrations
Figure 2: AMM Pilot Effluent Total Zinc Concentrations
Ash Grove Cement:
This case study will focus on the challenges associate with treatment on a very dynamic and large scale cement manufacturing facility. Each year site conditions change on this site so a flexible and robust treatment BMP was required. This section will also focus on the importance of proactive O&M activities. The Seattle Plant of the Ash Grove Cement Company is an approximately 18.5 acre site which is located directly on the Duwamish East Waterway of the LDW. A 610-gpm CESF treatment system with automated pH adjustment was installed in July of 2015 to treat for turbidity, elevated pH and total metals including; copper, zinc, mercury and arsenic. In the engineering and design phase of the project, it was determined that the majority of the contaminants of concern were directly related to suspended solids, as measured by turbidity. At that point, the maximum turbidity reading that was recorded in the data was 440 NTU. Since treatment system installation however, onsite source control measures have been modified to meet the plant’s operational requirements which in turn resulted in much higher influent turbidity readings. Due to space constraints onsite, the 610 CESF system originally included a limited volume of settling in tanks. Dependent on source control measures and rainfall intensity, these tanks have required sludge removal as frequently as a monthly basis. In March of 2016, due to high solids loading and additional flow volumes from previously unknown sources, Clear Water incorporated BHR-P50 (P-50) pretreatment into the treatment train to reduce the sand filter influent turbidity and reduce system bypass events. The facility is currently evaluating additional settling tanks and conveyance options in addition to material stockpile source control measures.
This case study will review both passive and active treatment technologies on a large scale bulk break terminal facility. This study will focus on water quality characterization and installation of best fit technologies for each basin of this facility rather than a commingled or centralized treatment approach. The facility is comprised of four separate drainage basins, three of which discharge directly to the LDW. Drainage Area 1 is comprised mostly of paved surfaces and had demonstrated relatively low suspended solids levels but with a moderate level of particulate and dissolved metals. Drainage Area 2 is a gravel employee parking area that infiltrates and has no direct discharge to the LDW. Drainage Areas 3 & 4 are the most heavily used areas of the site and have demonstrated large fluctuations in both TSS and total metals. The facility installed a semi-passive, proprietary multi-media treatment unit in Drainage Area 1 however, the project team was unsure this technology would be effective to handle the solids loading and large fluctuations in influent water quality in Drainage Areas 3 and 4. A 400-gpm CESF pilot unit was installed and successfully met all permit benchmarks throughout an 8 month period. The pilot system remained onsite throughout the remainder of the infrastructure improvements and permanent treatment system installation phase to manage construction related stormwater. In late 2014, a 725-gpm system was installed in DA-4 and a 1200-gpm system was installed in DA-3. Both system have since added P-50 pretreatment as an additional pretreatment step to further aid in managing fluctuations in influent pH and turbidity.
PHOTO #7 (left): Drainage Areas 1,3 and 4 of the 70-acre facility. Courtesy: Northland Services
This section of the showcase will focus on solid waste/recycling handling facilities that are located along the LDW. We will review a contaminated soils handling facility, operations and material recycling facility (MRF) and a reload facility designed to capture and ship solids from ongoing dredge operations from the barge to rail cars. This section will also focus on differentiating between stormwater and process water handling technologies and methods.
A Seattle based contaminated soils trans-load facility manages the majority of the soils from dump trucks to rail cars in a covered area, however drainage from the yard demonstrated elevated levels for turbidity, zinc and copper above the benchmarks of the ISGP. A small CESF system, utilizing a dual-polymer system (DPS) was evaluated during a pilot phase, which also include a polishing step using ion exchange resin to remove any dissolved zinc. The pilot phase demonstrated that the CESF with DPS was sufficient to meet ISGP benchmarks without the use of the ion exchange media.
A newly installed MRF, located along the LDW, acquired an ISGP with a TSS limit. Most of the operations occur inside and the majority of the contaminants of concern were related to metals with relatively low TSS values. The project team selected a non-proprietary multi-media system that utilizes an upper tank to filter out solids and a lower tank with adsorptive media to remove dissolved metals. The design allows for onsite staff to regularly maintain the top tank media without compromising the lower tank’s more expensive media. The site has reached attained compliance for all parameters.
A facility along the LDW has been acquired by a national waste services provider to collect, process and transport contaminated soils from various dredging operations (including the future LDW dredge) throughout the Puget Sound region. The majority of this site contains offloaded solids from barges in a containment berm where water is decanted from the dredge spoils. The dredge dewatering and rainfall from within the containment structure is collected and processed through a treatment system prior to being discharged to the King County Industrial Wastewater (KCIW) system for further treatment at the local Publically Operated Treatment Works (POTW). The site is permitted by KCIW via the Major Discharge Authorization to discharge at a rate of 100-gpm, however the site is required to treat up to 250-gpm and store the remaining volume of treated water to attenuate a maintained maximum discharge rate of 100-gpm, due to infrastructure restrictions in the sanitary conveyance system. Due to the likely presence of PCBs, PAHs, metals, high solids volume, as well as, limited treatment capacity and technology to handle those contaminants at the POTW, KCIW required the site to design and install a treatment system to essentially meet the discharge limits that would be required to directly discharge to the LDW. However, as the majority of the water is deemed “process water” Ecology requires the site to discharge water from within the containment structure to KCIW. The 250-gpm system includes a CESF and pH adjustment system as well as a granular activated carbon (GAC) with the ability to increase the flow rate up to 500-gpm once adequate conveyance lines are available. The current system also includes 6-21,000 gallon flow attenuating discharge tanks and an auto-sampler unit to help demonstrate compliance with the KCIW permit. The site is currently engineering a separate stormwater treatment system to maintain compliance with an individual permit to discharge to the LDW for any water that is generated outside of the containment berm.
Author Biography:
Nathan Holloway has been working in the stormwater and environmental fields for the past 15 years. During that time he has developed strong working relationships with contractors, industrial permittees, municipalities and regulators to address complex projects with practical, cost effective and innovative treatment solutions. Nate's treatment experience ranges from high-flow active treatment systems to passive or enhanced low impact development (LID) features and he is well regarded for his ability to develop customized solutions to each project. Mr. Holloway is active in many committees and organizations related to water quality and is well known as an educator in the stormwater industry. In his role as Vice President at Clear Water Services, Nate is responsible for the Business Development and Operations functions of the company.
