Under a task order issued by the USACE Seattle District under our USACE Kansas City PRAC, KEMRON, as the prime contractor, completed the Well 12A Shallow Excavation Remedial Action located within the larger Commencement Bay – South Tacoma Channel Superfund Site. The site is a former oil recycling facility where off-site migration of chlorinated solvent-contaminated groundwater impacted the City of Tacoma’s drinking water well (Well 12A). Other site soil and groundwater contaminants include polychlorinated biphenyls (PCBs), volatile organic compounds (VOCs), metals and dense non aqueous phase liquid (DNAPL). Following a decrease in the effectiveness of the previous pump and treat remediation strategy, a Record of Decision (ROD) Amendment specified a combination of soil excavation, in situ thermal remediation, and enhanced anaerobic bioremediation to reduce groundwater contaminant mass leaving the site by 90%.
KEMRON prepared a Remedial Action Work Plan (RAWP) which described the intended remedial action to include abandonment of existing monitoring wells; removal of the 12-inch concrete pad and associated rebar; a geophysical survey using EM61 and GPR; removal of any USTs and other metal debris; and removal of the highly contaminated soil and filtercake. Metal debris was targeted for removal to prevent interference during future implementation of thermal remediation. Use of green construction technologies was also prioritized as part of the excavation strategy. Excavation was planned for two areas approximately 50 ft by 50 ft predicted to contain greater than 1,000 ug/kg VOCs in shallow soil (0-5 ft bgs) based on modeling of historical soil concentrations measured in nearby borings. In addition, the RAWP included a Green Remediation Plan, a Waste Minimization Plan and an Accident Prevention Plan (APP).
Unforseen field conditions encountered increased excavation complexity and impacted project schedule. . First, following removal of the concrete pad, elevated soil contamination levels encountered led to multiple rounds of soil sampling and analysis to better delineate the excavation footprint and determine disposal requirements and options. Second, the initially unknown dimensions of the one known UST were identified as being on the upper end of anticipated sizes (8-foot diameter and 38 feet long). Furthermore, the UST, thought to be nearly empty, contained a concrete “plug” approximately 3’ by 4’ that blocked the former access point, nearly 7,000 gallons of liquid waste, and 35 tons of pea gravel that had to be removed. The pea gravel was believed to be non hazardous based on previous data but was sampled and shown to exceeded Land Disposal Restriction (LDR) treatment standards for trichloroethylene (TCE) and lead. Additionally, oily filtercake and soil near the northwestern corner of the UST was sampled and determined to contain much higher contaminant concentrations. This material was excavated and fount to extend vertically to approximately 15 ft bgs. The horizontal extent of the filtercake abutted the former Time Oil building footings requiring excavation using trench boxes, piano key removal and use of controlled density fill. On-site chemical oxidation treatment using persulfate (and hydrated lime as an activator) was proposed and implemented as an innovative solution to the extremely high concentrations of VOCs which otherwise would have required disposal via incineration. A total of 2,131 tons of filter cake and contaminated soil were treated on site, excavated, then loaded and trucked offsite for disposal at a Subtitle C landfill. The excavation area was backfilled with clean backfill, new storm drains and storm piping were installed and then asphalt was installed to complete the restoration.
KEMRON implemented an on-site in-situ chemical oxidation treatment of the material containing high concentrations of VOCs, metals and PCBs to reduce VOC concentrations to below LDR thresholds. This allowed for excavation and disposal to a landfill approximately 270 miles away as material that will meet LDRs. This is an environmentally sound and cost effective alternative to simply digging and hauling to an off-site incinerator (located approximately 900 miles away).
KEMRON was awarded and completed a $17.1 FFP remediation with performance-based remediation for the US Army at Fort Sheridan, an Army installation being closed under BRAC. KEMRON successfully managed 13 task areas which included regulatory agency negotiation, remedy selection, remedy implementation, LTM, O&M, construction, site documentation, community relations, and managing the Administrative Record. Under this contract, KEMRON was responsible for achieving RIP or RC for task areas. RC was achieved for seven task areas including an NFA DD for another task area which encompassed seven separate sites. For the additional task areas, KEMRON was responsible for implementing land use controls (LUC), closing monitoring wells and/or preparing an approved DD. For the RIP sites, KEMRON was responsible for LTM. KEMRON developed and received regulatory approval for site plans including safety plans and other reports and documents. In addition, KEMRON prepared all CERCLA documentation and the first CERCLA five-year review. The following is an overview of a few task areas.
KEMRON finalized the design and constructed a 13-acre RCRA Subtitle C cap over Landfills 6 & 7. The RCRA cap consists of multiple layers of geosynthetics, drainage layers, and low permeability clay.KEMRON also installed a leachate and gas collection system. The finished area is used as an open green field and hiking trail with prairie grasses, plants, shrubs and trees. KEMRON gained approval from IEPA, Army and the Navy to irrigate a 1.8-acre parcel using leachate collected from Landfills 6 & 7 as part of a pilot study for alternative disposal of leachate (compliant with EPA Region 2 Clean Program). The six-month study saved $50,000 in off-site disposal costs for the summer watering season. This pilot study, approved as a long-term disposal option, could ultimately save the Army approximately $2 million in life cycle costs over the next 30 years.
Five additional task areas included the demolition of a lead-based paint contaminated structure and the remediation of four areas with contaminated soils. KEMRON elected to meet residential standards on these five sites, thus eliminating the need for LTM and LUCs. KEMRON’s SOW required preparation of DDs. As a means to accelerate closure and gain immediate regulatory concurrent, KEMRON proposed to the BCT to prepare a non-time critical Action Memorandum instead. As a result, the approval time was cut dramatically and the remediation was completed a year ahead of schedule. The excavated soils were transported to the low areas in Landfill 6 & 7 as part of the required subgrade preparation beneath the liner, thus saving disposal costs.
KEMRON prepared the DD and design documents including LUCs for Landfill 5 and Coal Storage Area No. 3 (CSA3). The key design features of the 2.2-acre modified Subtitle C landfill cap on Landfill 5 included two feet of compacted clay overlying an impervious geosynthetic clay liner which included improvements to the existing storm water control system beneath the landfill, installation of a new perimeter drainage pipe, ravine slope stabilization, and elimination/realignment of the overhead utilities.
The CSA3 consisted of excavation of PAH contaminated soils from remnants of the former CSA. The removal action was completed in and around residences which required coordination with homeowners. KEMRON managed a comprehensive community involvement program designed to keep the local residents informed and involved. KEMRON developed a project website to provide construction updates, pictures, and other information, providing immediate status to stakeholders.
One of the challenges at Fort Sheridan was the management of the remedial activities amid the concerns of multiple stakeholders. Although the Army maintains environmental liability on a majority of the site that has not already been transferred to the community, the Navy and Army Reserve now occupy all of the properties that were covered under this contract. As a result, it was necessary for KEMRON to ensure that the remedial approaches being proposed and conducted site-wide met the requirements of all of the multiple stakeholders to include the Navy, Army, AEC, USACHPMM, Reserve, the surrounding towns and the community.