First Half Mile Cleanup
The Housatonic River cleanup is divided into three segments, the first ½ mile adjacent to the facility, the next 1½ miles downstream to the confluence of the East and West Branches, and the Rest of River downstream of the Confluence.
Upper ½-Mile Reach Removal Action
The first ½ mile of the portion of the Housatonic River subject to remediation is located in a densely populated area near the center of Pittsfield. The area is primarily commercial/industrial, although there is one recreational property abutting the River. A portion of GE’s 254-acre property abuts the River to the north, and several commercial/industrial properties, a playground, and additional GE property abut the River to the south. The entire ½-mile section of the River was channelized by the city and the USACE in the 1940s and, as a result, there are relatively steep banks and minimal floodplain in this area. Five of the former oxbows discussed above are present in this stretch of the River. Many of the historical discharges to the Housatonic River were likely to have occurred within this ½ mile.
Remediation in the first ½ mile consisted of two separate cleanups. In December 1996, EPA issued GE a Unilateral Order to remove highly contaminated sediments and bank soils in the area adjacent to Building 68. As a result, in 1997 and 1998 GE excavated and disposed of 5,000 cubic yards of heavily contaminated sediments (average PCB concentration of approximately 1,534 ppm) from a 550-foot section of the river, and 2,230 cubic yards of heavily contaminated bank soils (average PCB concentration in surficial soils of 720 ppm and average concentration in subsurface soils of 5,896 ppm) from a 170-foot stretch of the riverbank. Sediment removal activities were performed “in the dry;” that is, by installing sheetpile into the river and diverting the flow of the river around the sheetpile, dewatering small sections, and removing the sediments with standard excavating equipment located on top of the riverbank.
The second phase of the cleanup consisted of further bank soil and sediment excavation throughout the first ½ mile. This action began in October 1999. Excluding the areas remediated during the Building 68 cleanup, the average surficial (0-1 foot depth) sediment PCB concentration was 54.8 ppm and average concentration of PCBs in the top 3 feet of riverbank soil was 56 ppm. Sediment excavation was performed in a manner similar to the Building 68 remediation. Sheetpile was driven into the middle of the river channel and the flow was diverted to one side. Sections of the river were then dewatered and the “dry” sediments removed by conventional equipment (e.g., backhoes, cranes, etc.). Sediment removal occurred wherever there was surficial contamination (approximately 75% of the area) and proceeded to a maximum depth of 2 ½ feet. Construction sampling results indicated that contamination will remain below 2 ½ feet and, therefore, restoration of the riverbed consisted of the placement of a cap containing a silty-sand sorptive layer, covered by an armored layer to return the riverbed to its original elevation and as a substrate for restoration. The ½-Mile remediation and restoration was completed in September 2002. Approximately 11,800 cubic yards of sediment and 6,400 cubic yards of bank soils were removed.
GE is currently performing all required post-removal site control inspection, monitoring and maintenance activities.