Update September 4, 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.

The New York State Department of Environmental Conservation (NYSDEC) and National Grid (formerly KeySpan) have continued to make substantial progress on the major phase of remedial work 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).  A major milestone of the barrier wall construction was achieved with the installation of all the columns that comprise the barrier wall.  Quality assurance coring of select areas of the barrier wall will continue through September and demobilization from the site will be completed by the end of October.

The construction of the barrier wall resumed in February 2009. Because of the additional time needed to refine the optimum jet grout column installation parameters, the jet grout barrier schedule shifted to a new projected completion date of October 2009.  With the installation of all of the columns, we will meet this schedule. National Grid worked actively working with contractors and consultants as well as the NYSDEC to achieve this important objective for the community.

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 Plan (HASP) and Community Air Monitoring Plan (CAMP) to ensure worker and community safety.  From the start of field work to the present, concentrations of vapors and dust associated with intrusive site activities have been measured below action levels in the NYSDEC and New York State Department of Health (NYSDOH)-approved plans.

Ongoing activities:

  • 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

Future (two week look-ahead) activities:

  • 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

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.
  • 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.

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 have been placed on hold to allow for completion of the OU-1 remedy which uses the 25 Willow Avenue property as a staging area.  Remedial design activities at OU-2 will commence once the OU-1 remedy has been completed.

  • 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.

The final remedial investigation report for 1 Edgewater Street has been approved by NYSDEC and NYSDOH and a plan is being developed for soil and groundwater management at the property. 

Community Air Monitoring Plan Summary

A Community Air Monitoring Plan (CAMP) and Soil Vapor Monitoring Plan (SVMP) has been implemented in support of remedial 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 work activities. 

CAMP monitoring summary from August 11, 2009 through September 4, 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.