Jet Grout Barrier Wall Completed!

Operable Unit 1 (40 Willow Avenue)
National Grid and NYSDEC Reached a Major Milestone on the Final Major Phase of Remediation of OU-1 (40 Willow Ave. Sector) of Former Manufactured Gas Plant (MGP) Site with Completion of Barrier Wall.

• Managing the remainder of the jet grout wastes in the waste management facility and stabilizing the wastes for off site treatment and disposal in accordance with the approved work plans and state and federal regulations. 
• Continued groundwater sampling within the affected area of the buffer zone of two private properties
• Continued decontamination of all work areas and equipment at both 25 and 40 Willow Avenue properties.
• Demobilization of decontaminated equipment no longer needed from the site

• Continue waste management facility operations and off site transportation and disposal of the remainder of the generated wastes.
• Finalize the site restoration plan to restore the site and adjacent residential properties to pre-construction conditions.
• Continue decontamination of all work areas and equipment at both 25 and 40 Willow Avenue properties.
• Continue demobilization of decontaminated equipment no longer needed from the site
• A plan to evaluate the installation of non-aqueous phase liquid (NAPL) collection wells within the barrier wall is currently being produced and will provided to the NYSDEC for review. 

• A trench drain has been installed along the property line at the backyards of the Lynhurst Avenue properties to mitigate flow of surface water from the cap area to the Lynhurst Avenue properties;
• Community Air Monitoring Plan (CAMP) units are in place on the 40 Willow Avenue parcel and within the buffer zone on the Lynhurst residential properties to monitor for potential vapor and dust releases, if any, that might occur during construction activities at the site and to assist in determining when additional mitigation measures need to be taken. The CAMP units and Z-nose portable unit are calibrated to provide notice well before the NYSDEC and NYSDOH response levels are reached so mitigation can take place proactively -- long before CAMP action levels are reached.
• Soil vapor probes and groundwater piezometers have been installed within the buffer zone on the Lynhurst residential properties and around the former gas holder footprint to assess soil vapor and groundwater quality conditions for the on-going jet grout barrier installation.
• The vibration wire piezometers (VWP) have been installed within the sheetpile barrier and are operational. The 3 VWPs will be used to measure temperature and pressure variations during the jet grouting and provide useful data for optimizing the jet grout injection.
• The waste management facility retrofitting is complete and is operational 
• The reinforced concrete working surface has been installed at 40 Willow Avenue.  Jet grout collars have been cored into the concrete working surface to allow for an air tight seal between the drilling operations and the return lines to the waste management facility.
• Four jet grout columns using modified parameters were installed and quality assurance coring and testing was performed.
• A third large capacity pump to support the drilling operations is setup on 25 Willow Avenue and offers increased productivity. 
• Revised Site Management Plan for Jet Grout Vertical Barrier Wall Construction (OU-1) dated April 9, 2009 has been approved and submitted to the repositories.
• Installed the southern barrier wall adjacent to the residences, and the barrier meets the criteria for acceptance set forth in the Record of Decision.  No further jet grouting needs to be performed on the southern extent adjacent to the residential backyards.   
• Restored the Lynhurst Avenue properties buffer zones affected by the surface grout water release in April 2009 with clean soil and sod Laboratory testing results show a reduction of the residual compound concentrations beneath the release area;
• Completed jet grout production columns on the southern, western, eastern, and northern boundaries of the barrier in accordance with the contractor specifications and Site Management Plan;
• Completed quality assurance coring and hydrogeologic testing of the southern, western, eastern, and northern walls to determine the effectiveness of the installed jet grout columns.   Quality assurance core testing and hydrogeologic testing on the all four boundaries confirm the columns have achieved project requirements.
• Obtained final certification from the engineer of record for the southern, western eastern, and northern jet grout barrier walls;
• Completed post jet grout barrier installation sampling in accordance with the SVMP.
• Completed the full scale CAMP activities with fixed stations on September 30, 2009 following the completion of all intrusive and associated quality assurance testing of the barrier wall.  In the beginning of October, CAMP monitoring was completed with portable units in the vicinity of site restoration activities with NYSDEC approval.

• A remedial action has been completed on the 89 Willow Avenue parcel adjacent to the 25 Willow Avenue National Grid parking lot. Impacted shallow soils have been removed and the site has been backfilled and graded at the request of the property owner. Field work was performed under the observation of NYSDEC. 
• The plan to investigate an additional parcel acquired by the owner of 89 Willow and perform the additional limited excavation has been approved by NYSDEC and NYSDOH. Investigative borings have been installed at the 89 Willow Avenue property and samples analyzed to further evaluate soil conditions.  The results were provided to the NYSDEC for review.  
• After the excavation work is completed, a plan for future soil and groundwater management at the property will be developed for the 89 Willow Avenue.
• National Grid met with representatives of the Staten Island Railway to discuss access to install borings along the railroad right-of-way.  The work plan for these borings is currently being developed.
• The final remedial investigation report for 1 Edgewater Street has been approved by NYSDEC and NYSDOH. 
• A Draft Site Management Plan for the Edgewater property was prepared to manage soils and groundwater at the property.  The plan was provided to the NYSDEC and NYSDOH for review.