FAST TRACKED REMEDIAL DESIGN AND REMEDIAL CONSTRUCTION AT A FORMER MANUFACTURED GAS PLANT SITE

摘要

This paper summarizes a 'fast-tracked' remedial design and construction project at a former manufactured gas plant (MGP) site located in Pennsylvania. The project was located on a portion of the 1,000th site redeveloped under the Pennsylvania Land Recycling Program, where President George W. Bush signed legislation to assist developers in cleaning up brownfields in 2002. During 2004, PECO (a regional gas and electric provider) approached the owner of the property about performing environmental investigation and potential follow-up on remedial activities at this former MGP site (about 1 acre in size), which operated from 1875 to 1917 (Figure 1). The goal of this cleanup activity was threefold: (1) remediate this site as part of this utility's strong commitment to cleaning up former MGP sites that were inherited from its predecessor companies, (2) obtain environmental site closure from the state regulatory agency, and (3) complete remedial activities before the property owner began construction of a residential building complex at the site. A critical element of this remedial project was that the property owner had a tight schedule to construct this complex. Therefore, PECO (and its subcontractors) needed to quickly obtain subsurface information, develop a remedial design, and finish remedial construction within this tight schedule. Following negotiation of an access agreement between PECO and the Site property owner, URS Corporation (URS) performed an expedited site investigation to characterize soil and groundwater quality and to develop a plan for remedial action. Site characterization activities included the completion of a geophysical investigation, soil borings, test pits, and installation of groundwater monitoring wells. Based on the findings of the Site characterization, a remedial design was developed that involved: (1) removal and storage of the overburden soils within the 1-acre site footprint, (2) advancement of 760 linear feet of steel sheet pile, (3) dewatering the excavation, (4) moisture-conditioning of MGP impacted soils and (5) developing a groundwater treatment system that would meet the Publicly Owned Treatment Work's (POTW) specifications. The time from initial investigation to initiation of the remedial activities at the Site was a period of 11 months. During the 11 months that led up to the remedial action at the Site, the Remedial Action Work Plan (RAWP) was completed, remedial contract bid documents were prepared and a remedial contractor was selected. The successful partnership established between URS and the selected remediation contractor allowed for the expedited cleanup of the Site. The contractor selected for the remedial work was Enviro-Air Technologies, Incorporated, a small woman-owned business enterprise. Due to the size of the remediation contractor's company, and the capital expenditure for the project, cash flow for the remediation contractor was extremely important during the duration of the project. Therefore, PECO, URS and the remediation contractor developed a mutually agreeable arrangement that would allow a savings of 2% of each invoice paid within 20-days. This allowed for invoicing every ten working days and payment to the remediation contractor every 20-days for a savings of approximately $60,000 during the duration of the project. The length of the remedial construction project was 4 months, which resulted in the removal of 17,000 tons of MGP-impacted soils, treatment and discharge of 4,000,000 gallons of water to the POTW, and re-use of overburden soils. The area of excavation and shoring is presented on Figure 2. The project activities were completed on schedule with particular attention paid to safety and without incident.