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.

• 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;
• Obtained final certification from the engineer of record for the southern and western jet grout barrier walls;
• Completed restoration activities including a new fence installation and landscaping on the western boundary;
• 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. 
• Continuing CAMP and air monitoring to protect workers and the community. 
• Continuing quality assurance coring and testing to determine the effectiveness of the installed jet grout columns.   Quality assurance core testing and hydrogeologic testing on the southern wall boundary confirms the columns have achieved project requirements.
• Continue soil vapor and groundwater sampling within the buffer zone of #53 and #55 Lynhurst as agreed to with the Lynhurst residents in the June 2009 meeting.
• Continue collection of monthly groundwater samples from peizometers in the area affected by the April grout water release as part of SVMP activities.
• Continue the collection of monthly soil vapor samples as part of the SVMP

• Obtain final certification from the engineer of record for the eastern and northern barrier walls which are the final two segments of the wall
• Continue waste management facility operations and off site transportation and disposal of generated wastes.
• Continue real time CAMP and air monitoring to protect the community until the completion of all intrusive work activities.
• Complete post barrier installation sampling in accordance with the SVMP.
• Finalize the site restoration plan to restore the site and adjacent residential properties to pre-construction conditions at the completion of jet grouting

• 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.
• The southern barrier wall adjacent to the residences has been installed and 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.
• Lynhurst Avenue properties (#53 and #55) buffer zones affected by the surface grout water release in April 2009 have been restored with clean soil and sod Laboratory testing results show a significant reduction of the residual compound concentrations beneath the area;
• Completed installation of the western jet grout barrier wall;
• Completed installation of the eastern and northern jet grout barrier wall.

• 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.
• We met with representatives of the Staten Island Railway to discuss access to install borings along the railroad right-of-way to evaluate soil conditions adjacent to OU-2.  The work plan for these borings is currently being developed.