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AOC 65 Treatability Test Plan
Section 1 - Introduction
A treatability study will be performed at AOC 65 at CSSA. The treatability study will focus on evaluating the use of soil vapor extraction as a remedial alternative to address soil and groundwater contamination in the vicinity of Building 90. The treatability study will also be used to quantify the estimated mass of volatile organic compounds (VOCs), predominantly composed of PCE and TCE, that can be removed by an SVE system installed at the site.
The treatability study will consist of drilling and installing six vapor extraction wells (VEWs) and six multi-depth vapor monitoring points (VMPs) to depths ranging from 5 to 150 feet below ground level (bgl) to assess contamination in fractures above the water table. Monitoring wells installed as part of the RFI conducted at AOC 65 will be used as additional monitoring points during the treatability test.
In addition, a groundwater recharge study will be conducted at AOC 65. The groundwater recharge study includes continuous monitoring of meteorological and hydrological conditions in the study area to assess the nature, rate, and extent of groundwater recharge and flow in the subsurface. The groundwater recharge study will consist of installation of a weather station and six nested piezometers on the west side of Building 90. To assist in the determination of appropriate locations and construction details, geophysical surveys will be conducted at AOC 65 prior to VEW, VMP, and piezometer installation.
Activities conducted at AOC 65 will also include installation of 12 combination VEW/VMPs inside Building 90 to remove vapors from beneath the building. The Building 90 subslab ventilation system will assess the potential to remove contaminants in soils beneath the building without conducting excavation activities. However, if results from subslab ventilation indicate the system is not adequately removing contaminants, excavation of the Building 90 floor and the contaminated soils beneath it may be required.
Building 90 excavation activities will also include installation of up to 12 soil borings in areas outside Building 90. The exterior boring locations will be focused on the drainage ditch, near an abandoned drain outfall west of the building. Exterior soil boring data will determine the volume of soil within the ditch requiring excavation. Exterior soil borings and potential excavations beneath Building 90 are addressed in the Environmental Clean-up Plan for AOC 65, Parsons, April 2002.
This document outlines work to be conducted at Building 90 and AOC 65 in conjunction with the treatability and groundwater recharge studies. Section 2 of this report describes site conditions and Section 3 details the design and construction of each system to be installed. Section 4 outlines treatability testing to be performed on the completed SVE system and Section 5 presents reporting requirements.