The Challenge

Previously, this site had been owned and managed by a pharmaceuticals manufacturer where past production and waste disposal practices caused site-wide contamination. As a result, several phases of remedial activities were required for compliance with environmental regulations of the U.S. Environmental Protection Agency (EPA) and the Pennsylvania Department of Environmental Protection (PADEP).

One of the remedial activities required was to contain and clean-up a large plume of contaminated groundwater migrating downgradient from the site. The groundwater constituents consisted of metals, volatile organic compounds, and semi-volatile organic compounds.

The Interdisciplinary Approach

Chester Engineers provided design/build services for a 360-gallon per minute treatment plant, 14 extraction wells and conveyance piping network. The scope of work for this project involved the selection of the treatment process, development of a site-specific permitting plan, and final design, equipment procurement, and turnkey construction.

In order to accomplish this task, Chester process engineers designed and built an on-site groundwater treatment plant which involves the use of an iron co-precipitation/adsorption process for metals removal, as well as a carbon adsorption system for the removal of volatile and semi-volatile organic contaminants. This system also includes a filter press for dewatering of solids that incorporates proprietary technology that dewaters the sludge more thoroughly, resulting in fewer solids and lower operating and disposal costs. The resultant sludge is sent to a nearby landfill. Once treated, the groundwater (which meets the PADEP's requirements under an NPDES permit) is returned to the environment by discharging to an adjacent creek.

In addition to the treatment plant design and build, Chester Engineers designed and installed the groundwater extraction system at this site which is comprised of two networks of impacted groundwater pumping wells. The first network includes perimeter wells installed in designated areas to minimize migration of the site-affected groundwater to off-site areas. The groundwater from the site's most contaminated areas is pumped by the second network of wells that were designed for mass removal.

Following treatment system initiation, Chester Engineers' hydrogeologists provided an update to an existing groundwater model. The model (developed in MODFLOWT) was updated and recalibrated to better represent the as-built and operational characteristics of the contaminant recovery system. It was recalibrated using a 5-year history of periodic head measurements and precipitation data. The model was used to predict future operational performance under alternative pumping regimes and recharge conditions.

Chester Engineers' geoscientists have been providing sampling, monitoring and reporting services for the groundwater extraction and treatment system at the Whitmoyer Laboratories Superfund Site, since 1998.

The Sustainable Result

Chester designed and built a treatment plant to removed metals and organics contaminants from groundwater. The iron co-precipitation process provides for the use of spent pickle liquor supplied by a local steel manufacturer. Thus the pickle liquor is being 'recycled' to help remove metals contaminants from groundwater at the Whitmoyer Superfund Site. Also, Chester introduced a dense sludge process which creates a high density/lower water filter cake, thus reducing the amount of sludge which landfilled.

Lastly, Chester was able to save our client considerable expense by retrofitting existing groundwater monitoring wells into groundwater extraction wells, thereby reducing the overall number of new extraction wells which needed to be installed.