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Record of Decision System (RODS)



City & State:  UPPER MERION TWP  PA  19406
EPA ID:  PAD980692024
EPA Region:  03
NPL Status:  Currently on the Final NPL
ROD Type:  Amendment
ROD ID:  EPA/AMD/R03-96/225
ROD Date:  07/20/1996
Operable Unit(s):  05
Media:  soil
Contaminant:  VOCs, 1,2,3-trichloropropane, benzene, trichloroethane, tetrachloroethene
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

Tyson's Dump site is an abandoned septic waste and chemical waste disposal site located in Upper Merion Township, Pennsylvania. Several unlined lagoons were used to dispose of septic and chemical wastes during the period of operation. A full description of the site can be found in the original Record of Decision.

In 1984, a Record of Decision (ROD) was issued for the excavation and off-site disposal of contaminated soils at the Tyson's site. Before the 1984 ROD was implemented, a revised ROD was issued in 1988. In the 1988 revised ROD, soil vapor extraction (SVE) was selected as the remedy for lagoon area soils. The 1988 ROD also specified the installation of a groundwater recovery and treatment system to prevent site-related compounds in the groundwater from entering the Schuylkill River. An SVE system was designed and constructed during the spring and summer of 1988 and full scale operation of this system began in November 1988. Since then, the SVE system has removed approximately 200,000 pounds of volatile organic compounds (VOCs) from the lagoon area soils. Although several enhancements and modifications have been employed to improve performance, the SVE system has reached a low asymptotic limit of mass removal and will not achieve the cleanup standards specified in the 1988 ROD in a timely or cost-effective manner. At that time, a Focused Feasibility Study (FFS) was conducted to identify an alternative remedial action for the lagoon area soils. This ROD Amendment addresses lagoon area soil contamination not fully remediated by the 1988 revised ROD. This Amendment does not modify the 1988 ROD with respect to the groundwater recovery and treatment system.
Remedy:  This response action addresses contaminated lagoon area soils at the site. The 1988 revised ROD addressed the lagoon area soils by using an innovative technology, namely soil vacuum extraction. That remedy did not achieve the cleanup standards specified in the 1988 Revised ROD.

At the Tysons site, the lagoon area soils present a principal threat to human health through the direct contact and inhalation pathways. These potential threats will be mitigated by placing a wet soil cover over the lagoon area soils.

The selected remedy includes the following major components: installation of a contingent vent layer consisting of a high permeability layer for grading of the site and control of lateral migration of vapors; installation of a low permeability barrier layer covering the vent later which will maintain nearly saturated conditions to control and virtually eliminate upward migration of vapors - this barrier would become nearly saturated through natural precipitation and surface irrigation; installation of a vegetated cover layer; installation of a surface irrigation system; continued operation of the existing french drain, seep sump pumps and groundwater well pumps; and installation of vent pipes as necessary.
Text:  View full-text ROD [ 40K ]
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