This update of the cleanup project on Central Avenue in Needham is intended to apprise area residents and local officials of (1) the progress that has been made since the road was closed to through travel on May 14, and (2) what to expect in the coming weeks.

Work Completed June 4 - July 7

After the first three weeks of this project (May 14 - June 2), the preparatory work of fencing, traffic controls, soil pre-characterization, and mobilization of supplies and equipment to the site was substantively completed, and the trenching and installation of the Permeable Reactive Barrier (PRB) commenced. Installation of the PRB started during the week of June 4, and was completed on July 7. The now-completed PRB is 535 feet in length and was installed to a maximum depth of 54.5 feet. The zero-valent iron and sand mix was placed on the bedrock surface and extends to just above the groundwater table. Approximately 1,479 tons of zero-valent iron was used for the PRB.

Operationally, the construction of the PRB went very smoothly. There were two occasions when the biopolymer slurry broke down prematurely, and resulted in additional effort by the contractor (Geo-Con) to remedy the situation. However, despite these incidents, Geo-Con was able to meet their initial projection of a 5-6 week construction period for the PRB.

During the third week of the project, excavation began for the purpose of moving the storm drain line to an area under the street that would not be in the path of the Permeable Reactive Barrier. In addition to the storm drain re-location, water and sewer lines for several homes needed to be severed and re-located, and the above-ground wires for electric service, telephones, and cable had to be temporarily re-routed. Some of the utility work remains to be completed as part of the site restoration activities.

Upcoming Work

Now that the installation of the Permeable Reactive Barrier is complete, work associated with above- and below-ground utilities will be completed and site restoration work will be performed. There are a number of abutting private properties that need to be restored to their original condition, and the street must be re-paved. The de-mobilization process will begin during the week of July 9. The Linkbelt excavator will be disassembled and transported off-site along with any other equipment that is not needed for site restoration. In addition, various testing activities are necessary to ensure that the PRB is performing as designed. This testing will involve the installation of approximately 20 new monitoring wells. Drilling for these wells is expected to begin during the week of July 16.

The original estimate that the road would be closed for 12 weeks meant that we expected to be able to re-open the road by August 6. We are still on schedule to achieve that target.

The Needham Department of Public Works, the Board of Health, and the Conservation Commission have continued to periodically conduct site visits to inspect the project and monitor progress.