In Situ Bioremediation
-- Hydrogen Release Compound (HRC®) is a proprietary mixture produced by Regenesis that consists of ammonium chloride, potassium tripolyphosphate, lactic acid, yeast extract, and sodium hydroxide.
-- In the first application, HRC® was injected using 55 Geoprobe boreholes over a 2,000 square foot area, and to a depth of 6 to 18 feet below ground surface (bgs). A total of 1,140 pounds (114 gallons) was injected.
-- Following soil excavation to repair a leaky sewer pipe, HRC® was applied to the bottom of two excavations to address any remaining soil contamination. A third application (the second injection application of HRC®) was conducted in July 2000.
Mechanical Soil Aeration and Thermal Desorption
-- Soils exceeding the state cleanup level of 0.5 milligrams per kilogram (mg/kg) for PCE were mechanically aerated in an on-site treatment cell, which consisted of a plastic liner with straw bale berms.
-- Following mechanical soil aeration, these soils were transported off-site for treatment using thermal desorption.
-- In addition, approximately 80 cubic yards of soil excavated from the area close to the facility contained low levels of PCE (less than 0.5 mg/kg). These soils were also transported off-site for thermal desorption treatment prior to disposal.
State Corrective Action
Headquarters VCP Policy & Technical Manager
Department of Ecology
Toxics Cleanup Program HQ
300 Desmond Drive
Lacey, WA 98504
Phone: (360) 407-7244
Fax: (360) 407-7154
Environmental Associates, Inc.
2122 112th Avenue NE
Bellevue, WA 98004
Phone: (425) 455-9025
Fax: (425) 455-2316
1011 Calle Sombra
San Clemente, CA 92673
Phone: (949) 366-8000
Fax: (949) 366-8090
VOCs — PCE, TCE, DCE, and vinyl chloride
Dry cleaning facility operations.
Type/Quantity of Media Treated:
-- 6 to 18 feet bgs over a 2,000 square foot area
-- 24,000 cubic yards using in situ bioremediation (based on dimensions of injection area)
-- 86 cubic yards using ex situ thermal desorption (6 cubic yards also treated by mechanical soil aeration prior to thermal desorption)
Purpose/Significance of Application:
Full-scale remediation of VOCs in groundwater and soil using in situ bioremediation.
Regulatory Requirements/Cleanup Goals:
-- Groundwater cleanup goals are based on Washington State Model Toxic Control Act standards. Cleanup levels for three contaminants are based on residential use as follows: PCE at 5 micrograms per Liter (µg/L), TCE at 5 µg/L, and vinyl chloride at 0.2 µg/L. Cleanup levels for two other contaminants are based on universal use at all sites: cis-1,2-DCE at 80 µg/L and trans-1,2-DCE at 160 µg/L.
-- The soil cleanup levels for PCE and TCE are both 0.5 mg/kg.
In Situ Bioremediation:
Following HRC® injection into the groundwater in December 1998, PCE concentrations increased significantly at MW-1 (from 551 up to 67,000 micrograms per liter [µg/L]) in January, February, and March 1999. This increase was attributed to a leaking sewer pipe that allowed PCE-contaminated sewer effluent to seep into the subsurface. Following excavation activities, samples of remaining soils were collected and the results indicated concentrations below cleanup levels (0.5 mg/kg for PCE and 0.5 mg/kg for TCE). After excavation of soil, repair of sewer pipes, and treatment of soil with HRC® at the bottom of the excavations (second HRC® application), PCE and TCE concentrations in groundwater at MW-1 decreased by approximately 99% and 86%, respectively, but cleanup goals were not achieved. Concentrations of vinyl chloride in MW-1 increased due to increased degradation of cis-1,2-DCE. Samples of soil remaining in the excavations were below cleanup levels.
Following the third HRC® application, PCE, TCE, and DCE achieved cleanup goals. These concentrations decreased by 99.9% to less than 2 µg/L for PCE and TCE, and to 0.24 µg/L for DCE. Vinyl chloride also decreased by 99.9% but exceeded the cleanup level of 0.2 µg/L with a concentration of 0.29 µg/L in June 2004. Based on discussions with the project manager in June 2006, subsequent sampling indicated that concentrations of vinyl chloride were eventually reduced to non-detect levels. However, sampling data from the vendor were not available to verify the statement.
Groundwater samples collected from MW-4, MW-5, and MW-6, which are located further downgradient of MW-3, have not shown detectable concentrations of PCE or PCE-degradation by-products.
Mechanical Soil Aeration:
Laboratory analysis of treated soils indicated PCE concentrations ranging from 0.12 to 0.28 mg/kg prior to soil treatment using thermal desorption.
The cost of HRC® was $13,860 for the two injection applications (December 1998 and July 2000).
Cleaners #1 is an operational dry cleaning facility located in a retail strip mall in Kent, Washington. The facility is approximately 1,600 square feet in area and is surrounded by mixed retail, commercial, and residential properties.
Contamination was first discovered at the facility in August 1998, during a Phase II Environmental Site Assessment (ESA). Interior and exterior soil samples were collected from below the facility floor near the dry cleaning machine, and outside the facility near the rear door. Groundwater samples were collected outside the facility. PCE and TCE were found at concentrations above state cleanup levels in groundwater, and PCE slightly exceeded cleanup levels in exterior soil samples. Interior soil samples showed only trace levels of PCE.
Additional soil sampling conducted in September 1998 from six exterior borings and three interior borings indicated that PCE and TCE concentrations were not detected above state cleanup levels. However, groundwater samples collected from three of the six exterior locations showed PCE above the state cleanup levels, with the highest concentration being closest to the rear door of the facility.
Enhanced bioremediation using HRC® was used to primarily address groundwater contamination at the site, while also treating some residual soil contamination. Excavated soil was treated using thermal desorption and mechanical soil aeration. After the first round of HRC® injection at the site, PCE concentrations increased. To determine potential sources of the contamination, sampling of sewer effluent being discharged from the facility to the sanitary sewer system was conducted. Results showed that PCE was being discharged from the facility at levels above state cleanup standards through two potential leaks in the sewer pipe. Following this determination, approximately 86 cubic yards of soil were excavated and the pipes were repaired. HRC® was applied to the bottom of each excavation to address any residual soil contamination. Excavated soil was treated on site using mechanical soil aeration followed by off-site thermal desorption prior to off-site disposal. A third application included HRC® injection in July 2000. Subsequent sampling has shown PCE, TCE, DCE, and vinyl chloride at concentrations below state cleanup levels. The State of Washington is anticipating receipt of a No Further Action letter for this site.