Update October 13, 2009

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.

The New York State Department of Environmental Conservation (NYSDEC) and National Grid (formerly KeySpan) have completed the installation of the jet grout barrier wall at the sector of the former manufactured gas plant site on which the gas holder and supporting facilities were located (the OU-1, 40 Willow Avenue parcel).  Quality assurance coring and hydrogeologic testing of select areas of the barrier wall have been completed, and the four walls have been certified by the Engineer-of-Record.  Final site restoration activities are underway.  The contractors have commenced demobilization activities for the site which are projected to be completed by the end of October.

Site personnel have collected measurements from wells and sampling points around the work zone as part of the Soil Vapor Monitoring Plan (SVMP) and air quality measurements that are elements of the site’s Health and Safety (HASP) and Community Air Monitoring Plans (CAMP) to ensure worker and community safety during the barrier wall installation activities.  From the start of field work through completion of the jet grout barrier and quality assurance testing in September, concentrations of vapors and dust associated with intrusive site activities have been measured and monitoring results have been below action levels in the NYSDEC and New York State Department of Health (NYSDOH)-approved plans.  The post remediation soil vapor and ground water sampling event was conducted during the first week of October and will be incorporated into the final SVMP report.

Ongoing activities:

  • 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

Future (two week look-ahead) activities:

  • 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. 

Completed Activities:

  • 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.

Operable Unit 2 (25 Willow Avenue)

OU-2 is the former manufactured gas plant that previously operated at 25 Willow Avenue.  There are two off-site areas that are located adjacent to OU-2 at 89 Willow Avenue and 1 Edgewater Street.  The remedial activities at OU-2 have progressed with the approval of the final remedial design work plan by NYSDEC and NYSDOH.  The preliminary remedial design activities were placed on hold to allow for completion of the OU-1 remedy which uses the 25 Willow Avenue property as a staging area.  With the completion of the OU-1 remedy, the preliminary design activities for the OU-2 remedy can commence

  • 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.

Community Air Monitoring Plan Summary

A Community Air Monitoring Plan (CAMP) and Soil Vapor Monitoring Plan (SVMP) has been implemented in support of barrier wall installation activities at 40 Willow Avenue Operable Unit 1 (OU-1) of the Clifton Former MGP Site.   The CAMP consists of an automated network of fixed air monitoring stations that is supplemented with measurements collected daily during intrusive barrier installation activities.  The fixed stations were replaced with portable units at the end of September with NYSDEC approval.

CAMP monitoring summary from September 5, 2009 through October 9, 2009:

CAMP monitoring confirmed that concentrations of vapors and dust associated with intrusive site activities were below levels requiring action in the NYSDEC and NYSDOH- approved plan. Copies of weekly CAMP and SVMP reports and other site documents are being provided to the two public document repositories for the project.  The repositories are located at:  

Community Board 1
One Edgewater Plaza
Room 311
Staten Island, NY 10305
Phone #: (718) 981-6900
Borough President’s Office
Borough Hall
Staten Island, New York 10301
Phone #: (718) 816-2057

If you have any questions or comments about the work on the site, please use the site's Telephone Hotline at 718-982-7349.