CONTAINER TERMINAL STORMWATER TREATMENT ON A SUPERFUND SITE Stephen Bentsen, Floyd Snider, Seattle

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1 CONTAINER TERMINAL STORMWATER TREATMENT ON A SUPERFUND SITE Stephen Bentsen, Floyd Snider, Seattle ABSTRACT SSA Terminals, LLC (SSAT), operates Terminal 18, a 200-acre container terminal located on Harbor Island, a Superfund site in Seattle, Washington. The facility operates under the National Pollutant Discharge Elimination System (NPDES) Industrial Stormwater General Permit (ISGP) and recently completed installation of stormwater treatment for 80 acres of the container terminal, including a 3,000-gallon per minute (gpm) chitosan enhanced sand filtration (CESF) system and three modular wetland treatment systems. The stormwater treatment was installed as part of Level 3 corrective actions (treatment). Various stormwater treatment technologies were evaluated in an Engineering Report prepared for the Washington State Department of Ecology to ensure that the corrective actions met the regulatory requirements and to ensure that the systems would minimize impacts to the operations at the terminal. The evaluation included identification of appropriate treatment systems and cost estimates for both capital costs and annual operation and maintenance costs. To assist in selection of the appropriate treatment system, a weighted matrix was developed to evaluate which system was the best suited for each subbasin in regards to technical feasibility, constructability, and long-term operability. The selected treatment systems were a 3,000-gpm CESF system to treat 61 acres of the container terminal and three modular wetland treatment systems sized at 100, 200, and 570 gpm to treat an additional 19 acres of the container terminal. Numerous issues made the implementation of the treatment systems challenging. Several key items affected the project, including the following: The terminal is located within the Harbor Island Superfund site, administered by the U.S. Environmental Protection Agency (USEPA), and governed by a Consent Decree entered into between the Port of Seattle and USEPA. Contamination due to historical practices predating SSAT s lease and operations is present in subsurface soils, groundwater, and aquatic sediments. These conditions presented additional difficulties for handling disposal of soil, the ability to discharge extracted groundwater from dewatering, and the paving requirements for areas of the terminal that are covered by a cap. SSAT does not own the property but leases it from the Port of Seattle. The facility has an aging infrastructure that was installed prior to SSAT s current lease. Records for the stormwater collection and conveyance system were inaccurate and the quality of the conveyance system was largely unknown and sometimes was in disrepair. Significant records research and conveyance system inspections were necessary to obtain accurate information about the conveyance system and to identify key areas that needed repair. The majority of the construction occurred near the bulkhead and required deep excavations, significant shoring, and dewatering to allow construction to be conducted. Due to the heavy loading requirements of the terminal, all subsurface structures had to be designed as top-pick load rated structures. A significant quantity of soil thought to be reusable proved to be geotechnically unsuitable, requiring additional backfill to be imported and the unusable soil to be exported. Construction began in April 2016 and was completed on schedule in October Page 1

2 INTRODUCTION SSAT operates Terminal 18 (the Terminal), a 200-acre container terminal located on Harbor Island, a Superfund site, in Seattle, Washington. The facility operates under the NPDES ISGP. In 2016, as part of a Level 3 Corrective Action (Treatment Best Management Practices [BMPs]) and in accordance with a settlement following a citizen lawsuit, end-of-pipe treatment was installed for Phase 1 of treatment, which included 80 acres of the terminal. FACILITY INFORMATION The Terminal occupies approximately 200 acres along the eastern side of Harbor Island, a 420-acre island located in the Duwamish River delta in Elliott Bay. The island was constructed on the Duwamish River delta with the addition of bulkheads and fill placed in the early 1900s. The facility is owned by the Port of Seattle (the Port) and leased by SSAT. The Port constructed the Terminal and installed utilities, including the stormwater collection and conveyance system, before SSAT s current lease. Approximately 175 acres (88.6 percent) of the 200-acre facility are dedicated to container yard consisting of roadways, drive aisles, and storage of stacked full and empty shipping containers. In addition to the container yard portion of the Terminal, there are a few specific areas of the facility (a total of approximately 5.9 acres, or 2.9 percent of the Terminal area) in which vehicle maintenance and equipment cleaning occurs. The remainder of the site is the Wharf Apron, administrative buildings, and parking areas. Refer to Figure 1 for a site map. Source: Google Earth As is typical for marine container terminals, the Terminal is predominantly flat to allow stacking of containers and enable easy onloading and off-loading. The Terminal is generally at an elevation of 16 to 19 feet mean lower low water (MLLW), or elevation 14 to 16 feet by North American Vertical Datum of The Terminal discharges stormwater through 16 outfalls to the East Waterway of the Duwamish River and through 3 outfalls to the West Waterway of the Duwamish River and through 1 outfall to Elliott Bay. Due to the tidal fluctuations, and tide gates installed by the Port at the outfalls (some of which no longer function properly), salty or brackish river water enters the stormwater conveyance system at the facility. This inflow Figure 1. Site Map severely limits the availability of proper conditions for stormwater sampling; stormwater samples characteristic of facility discharge can be collected only at times when a rainfall event is concurrent with a low tide during daylight hours when conditions are safe. SSAT installed new tide gates at several of the outfalls that were being sampled under the NPDES ISGP at the time of installation to ensure that these sampled outfalls had functional tide gates. The presence of functional tide gates prevents the inflow of river water and allows more frequent sampling (i.e., during rainfall events that occur during safe conditions without consideration of the tides). Page 2

3 SUPERFUND STATUS The Terminal is located within the Harbor Island Superfund site, administered by the USEPA, and governed by the Consent Decree entered into between the Port and USEPA. Contamination due to historical practices conducted on Harbor Island prior to SSAT s tenancy is present in subsurface soils, groundwater, and aquatic sediments. Three operable units (OUs) of the Harbor Island Superfund site pertain to the Terminal. The uplands portion of the Terminal is located within the Soil and Groundwater Operable Unit (S&G-OU1), the Terminal s wharfs are located over the East Waterway within the East Waterway Sediment OU (EW-OU10), and stormwater discharges to both the East and West Waterways (EW-OU10 and the West Waterway Sediment OU [WW-OU8]). Refer to Figure 2 for OU boundaries. The Port and USEPA maintain pavement caps and implemented institutional controls at the property to comply with Superfund requirements. These institutional controls place restrictions on SSAT as a tenant of the Port. SSAT is required to follow special Figure 2. Vicinity Map procedures for subsurface work due to the presence of contaminated soil and groundwater below the pavement. Infiltration of stormwater into facility soils is prohibited. In addition, subsurface contamination conditions pose a risk of contaminant infiltration from subsurface sources into the stormwater system installed by the Port. POLLUTANT SOURCES Due to its location within an urban environment in a highly industrialized area and in the vicinity of heavily trafficked and elevated roadways, the Terminal is subjected to air deposition of pollutants from the surrounding areas and activities. Based on experiences at other terminals and recent sampling by the Port, it is presumed that a significant portion of the pollutants present on facility pavement and roof surfaces is a result of this urban air deposition. s of the pollutants of concern at the Terminal are comparable to those in other urban areas with similar uses such as parking and truck traffic. The primary sources of potential pollutants throughout the Terminal and in the Phase 1 subbasins include the following: Air deposition. Pollutants from air deposition settle on the Terminal surfaces and become comingled in stormwater. Page 3

4 Vehicles not owned by SSAT. The majority of the traffic at the Terminal consists of vehicles not owned by SSAT that enter the Terminal to deliver or pick up containers. These vehicles constitute short-haul and long-haul traffic. During peak activity levels at the Terminal, it is not unusual for approximately 2,000 gate transactions to occur per day with entrances and exits to the Terminal. Pollutants from these vehicles include the following: o Copper, zinc, dirt, and other debris from the surrounding roadways that adhere to vehicle undercarriages and tires and are tracked into the Terminal. o Copper (and zinc to a lesser extent) particulates from brake pads. o Zinc particulates from vehicle tires. Vehicles owned by SSAT. SSAT operates numerous vehicles at the Terminal to move containers about the facility. These vehicles include top picks, side picks, hustlers, bomb carts, forklifts, rubber-tired gantry cranes, fueling trucks, truck chassis, man lifts, pickup trucks, and several vans. Because the majority of these vehicles are limited to travel within the Terminal, their tracking-in of off-site pollutants is not a primary concern. Pollutants from these vehicles include the following: o Copper (and zinc to a lesser extent) particulates from vehicles with copper brake pads. Some SSAT vehicles such as top picks and side picks have wet brakes (encapsulated rotors in an oil bath) and no brake pads, and a majority of SSAT s cargo handling equipment brake pads are non-copper. o Zinc particulates from vehicle tires. Maintenance areas. Maintenance and repair areas typically have greater concentrations of pollutants, including copper, zinc, and turbidity due to maintenance activities, storage of materials, and high traffic volumes. Painted surfaces. Paint typically includes zinc as a part of its mixture, which may leach into stormwater over time. The concentration of zinc varies by paint manufacturer and the year it was produced. However, zinc is a common antioxidant used in paints for materials that will be exposed to salt air, such as shipping containers. At the Terminal, the primary painted surfaces that may include zinc (that have not already been painted or coated with non-zinc paint) include the following: o Containers that are brought into the Terminal by cargo ships and trucks. These containers are not owned by SSAT and the types and condition of paints on the containers vary. o Some building sidings with high zinc concentrations. These are typically under eaves and are not consistently exposed to stormwater. Building roofs. Roofs of buildings at the Terminal may contain galvanized zinc and contribute to zinc levels in the stormwater. TREATMENT SELECTION The three most important criteria for SSAT with respect to treatment selection were: 1. The system s ability to meet benchmarks and/or effluent limits, including likely potential to meet benchmark values or effluent limits introduced or changed in future ISGP permit cycles. 2. The cost of the system, including capital costs, construction costs, and long-term operation and maintenance (O&M) costs. 3. The size of the system, particularly with respect to impact on shipping container storage and disruption to terminal operations. Page 4

5 Each of these three factors was evaluated in detail for each system considered. Additional considerations included the extensiveness and difficulty of required system maintenance, and the relative ease or difficulty of construction, including scope of sub-surface disturbance and availability of pre-fabricated treatment system components. In order to select the most appropriate treatment system, it was first necessary to conduct additional analysis to better understand the characteristics of the pollutants in the water. Samples were collected within all the subbasins and analyzed for particulate size, total suspended solids (TSS), turbidity, ph, and both dissolved and total metals. These results and the average and maximum metal concentrations at each subbasin were used to identify a variety of appropriate treatment methods and were used with treatment system vendors for identifying anticipated removal efficiencies to determine if the NPDES permit benchmarks were achievable. Refer to Tables 1 and 2 for average and maximum removal efficiencies required to meet benchmarks. Table 1. Efficiencies Required to Meet s Subbasin 3 Subbasins 14 and 15 Subbasins 19 and 20 Efficiency Necessary to Meet Efficiency Necessary to Meet Efficiency Necessary to Meet Parameter Turbidity (NTU) % 27 25% % TSS (mg/l) Copper (µg/l) Zinc (µg/l) NA No Data No Data % % % % % % % Table 2. Maximum Efficiencies Required to Meet s Subbasin 3 Subbasins 14 and 15 Subbasins 19 and 20 Greatest Efficiency to Meet Greatest Efficiency to Meet Greatest Efficiency to Meet Parameter or Effluent Limit Maximum Maximum Maximum Turbidity (NTU) % % % TSS (mg/l) % No Data No Data 72 58% Copper (µg/l) Zinc (µg/l) % 68 79% 56 75% % % 1,250 91% To determine the appropriate treatment BMPs for each subbasin, removal efficiencies were compared to influent stormwater quality data. Both above- and belowground systems were evaluated. Vendor claims, available data from similar installations, pilot tests and bench scale studies, and professional judgment were used to determine that each of the proposed treatment systems could treat influent stormwater to the Page 5

6 pollutant removal efficiencies necessary to assist the Terminal to reach permit benchmarks for copper, zinc, turbidity, and TSS. Because the Terminal is located on a Superfund site, subsurface soil and groundwater impacts must be considered when evaluating treatment options. Traditional municipal treatment BMPs that use large wet ponds, or other storage tanks and areas, were not considered suitable due to space and vertical elevation constraints and the constraints on disturbing the Superfund cap. Traditional municipal treatment BMPs are not preferred because of the complex structural, maintenance, and access issues associated with the treatment technologies, as well as the uncertainty associated with the treatment BMPs capability of meeting the required removal efficiencies. Treatment systems that minimize the need for subsurface soil removal and that minimize the need for reconfiguration of the subsurface stormwater conveyance features were considered preferable to systems that would require significant below-grade reconfiguration. The treatment systems that were carried forward for more detailed suitability analysis included the following: CESF treatment systems provided by four vendors: Clear Creek Systems, Corix, CORETECH, and StormPROOF by Storm Water Systems Electrocoagulation (EC) treatment systems provided by two vendors: WaterTectonics and Enpurion Passive filtration treatment systems, including two aboveground systems (Modular Wetland s MWS Linear [MWS], a biofiltration treatment system, and StormwateRx s Aquip enhanced filtration treatment system), and two belowground systems (Baysaver Technologies' BayFilter and Hydro International s Up-Flo Filter, both filter treatment systems) After identifying the potential treatment systems that would meet the benchmarks, a selection matrix was established that identified the key factors and a ranking to achieve the required criteria identified above (refer to Table 3). Comprehensive, subbasin-specific matrices identifying a rating for each system with respect to each of the factors evaluated were prepared for each subbasin. System size was evaluated for each system using vendor-provided size and configuration estimates for installation of their system in each of the subbasins identified for Phase 1 treatment, using subbasinspecific treatment flow volume requirements. Each of the vendors contacted were told that system footprint would be a major consideration in final treatment selection, and, therefore, to reduce footprint as much as possible for their initial design. Vendor-provided treatment system sizes were modified to include connection to the detention tanks, flow splitters, and lift stations that would be necessary to ensure proper operation of the treatment system. The footprints of these additional features were minimized to the extent capable for each system, including installation of some features below-grade or stacked when possible. Finally, the total aboveground footprint was converted to twenty-foot equivalent units (TEUs), which are equivalent to the amount of space taken up by one 20-foot-long shipping container. This is the size that was used for evaluation of the overall system size in each of the Phase 1 subbasins. Page 6

7 Table 3. Treatment System Evaluation Matrix Rating Considerations Weight Capital Costs (System Only) -- O&M Costs (Annual) -- Above Ground (A) or Below Ground (B) -- Above Ground System Size (SF) -- TEU Size Equivalent -- Space Utilization System Size (Above Ground) 10 Treatment System System Purchase Cost 8 Confidence to Meet s 10 Adaptability 8 System Simplicity 6 Constructability Construction Cost 8 Construction Difficulty 6 Simplicity of Pre-Fabrication 3 Operation And Maintenance O&M Costs 8 Worker Safety Systems 5 Access 5 Maintenance 6 Monitoring Ease 4 Each of the treatment systems evaluated was determined to be capable of reducing the influent stormwater concentrations observed at the Terminal to levels less than the applicable permit limits. Therefore, the final selection for each subbasin was made with consideration of system cost (including capital costs and expected O&M costs), aboveground footprint of the system, relative ease of construction of the system, long-term system maintenance requirements, power demand of the system, and compatibility of operational and maintenance requirements with terminal operations and staffing. A final score was determined for each subbasin and a treatment system was selected based on this score. The treatment systems selected are as follows: Modular Wetland System o Subbasin 3: 12 acres, 570 gpm o Subbasin 14: 2 acres, 100 gpm o Subbasin 15: 4 acres, 200 gpm Chitosan Enhanced Sand Filtration: o Subbasins 19 and 20: combined for 61 acres, 3,000 gpm Page 7

8 Although it was originally suspected that below ground systems would be less expensive, it was found that the above ground treatment system was the preferred option. This was because of the costs for the additional excavation (including shoring) and contaminated soil disposal, combined with the increased O&M costs and the lack of adaptability. The evaluation also identified that, although the CESF system is more expensive, it was actually a more cost-effective option for the larger subbasins, which was a key reason why it was selected for the combined treatment area of subbasins 19 and 20. TREATMENT IMPLEMENTATION Following selection of the treatment system for each subbasin, construction documents were prepared and a contractor was selected. The treatment systems were installed successfully and were operational by the October 30, 2016 deadline. This section identifies some of the key challenges and unique features of this project: Superfund Status: Contamination due to historical practices predating SSAT s lease and operations is present in subsurface soils, groundwater, and aquatic sediments. Due to these conditions, all soil that needed to be disposed of off-site had to be sent to a Subtitle D landfill that was permitted to accept contaminated soil and extracted groundwater needed to be treated for pollutants prior to discharge to surface water. Additionally, there are paving requirements for areas of the Terminal that are covered by a cap. Each area within the cap needed to be tested for permeability following installation. Site Ownership: SSAT does not own the property but leases it from the Port. The facility has an aging infrastructure that was installed prior to SSAT s current lease. Records for the stormwater collection and conveyance system were inaccurate and the quality of the conveyance system was largely unknown and sometimes was in disrepair. Significant records research and conveyance system inspections were necessary to obtain accurate information about the conveyance system and to identify key areas that needed repair. During construction, several unknown utilities were encountered that required coordination with the utility companies and the Port to identify relocation methods. Site Conditions: The majority of the construction occurred near the bulkhead and required deep excavations, significant shoring, and dewatering to allow construction to be conducted. Due to the heavy loading requirements of the Terminal, all subsurface structures had to be designed as top-pick load rated structures. The site is located adjacent to the East Waterway of the Duwamish River, which is tidally influenced. Therefore, water levels around the excavation were variable and had to be managed with robust dewatering. Additionally, the treatment systems had to be designed to prevent salt water from entering the treatment systems as they are not designed to handle salt water. A significant quantity of soil thought to be reusable proved to be geotechnically unsuitable, requiring additional backfill to be imported and the unusable soil to be exported. Value Engineering: In order to provide SSAT with the best product possible, a cost-savings sharing incentive was implemented for the contractor throughout the project. This allowed the contractor to provide design change and material suggestions throughout the project that would save the client money and still provide the required treatment. This incentive reduced the overall project cost by approximately $300,000. Page 8

9 CONCLUSION Phase 1 was completed and the treatment systems were operational in October 2016 and have been meeting benchmarks. Throughout the wet season of 2016 to 2017, the treatment systems were adaptively managed to be the most efficient and have the maximum removal efficiencies. The CESF system has undergone treatability testing to determine the most efficient chitosan dosing rates and has met benchmarks throughout testing. The MWS have been operational and the manufactures are working on implementing the best media for the beds and for pre-treatment. In order to minimize SSAT s maintenance requirements, SSAT has signed vendor agreements to provide maintenance to each of the systems. Phase 2 is currently in design and will consist of end-of-pipe treatment for approximately 45 acres of the facility and will include five subbasins. Treatment technologies are being evaluated and are likely to include aboveground MWS and/or CESF systems. Phase 2 will be constructed in the summer of 2018 and will be operational by the October 30, 2018 deadline. BIO Stephen Bentsen is a professional environmental engineer and Associate Principal at Floyd Snider with 14 years of professional experience. Mr. Bentsen specializes in stormwater and wastewater regulatory compliance and treatment, marine/waterfront sediment and uplands remediation, and construction management. He is particularly skilled with projects that include development and evaluation of stormwater treatment alternatives, assembly of conceptual and design-level cost estimates, environmental and civil engineering design, and construction management. Page 9