KeySpan Energy Corporation Hempstead Former Manufactured Gas Plant Site

Posted on June 12, 2015

Client: KeySpan Energy Corporation
Location: Hempstead Former Manufactured Gas Plant Site
Project Type: Site Investigation Program

Major Components

  • Remedial Investigation
  • Human Exposure Assessment

Project Description


The firm was retained by KeySpan Energy (KSE) under a multi-year contract to undertake and complete remedial investigations at a number of its former manufactured gas plant (MGP) sites and gas holder sites throughout Suffolk, Nassau, Queens and Kings Counties, New York. The Hempstead facility is one such site.

KSE conducted this investigation as part of a Voluntary Cleanup Agreement (VCA) with the New York State Department of Environmental Conservation (NYSDEC). The objectives of the investigation were to identify source areas, delineate the extent of contamination, define pathways of contaminant migration, determine potential receptors and evaluate the need for corrective measures.

Background/Site History


The Hempstead former MGP site is located in the Villages of Hempstead and Garden City in Nassau County, New York. The site covers approximately 6.7 acres and currently serves as an active natural gas regulator station, however, the majority of the site remains vacant land.

The site operated as a gas plant from the early 1900s through the early 1950s. Records indicate that the MGP employed the Carbureted Water Gas manufacturing process throughout its operating life. Following the arrival of natural gas in the northeast, the facility served only as a peaking/emergency facility to ensure adequate gas supplies and was subsequently shut down and demolished in the mid-1950s.

The site property is presently owned by KSE. All operations at the site are conducted by KSE for both its internal gas operations and the electric operations of the Long Island Power Authority (LIPA). Residential properties are located to the north of the site and an automobile dealership and similar commercial businesses occupy the properties to the east of the site. Village property to the west of the site includes public parking areas, a recreational park and water district facilities, including public water supply wells. Various commercial entities border the site to the south, including an automobile dealership vehicle storage area and fuel oil loading facility.

Scope of Services


The scope of services for the Hempstead former MGP site includes the following:

  • Preparation of Technical Scope of Work
  • Preparation of Generic and Site-specific Work Plan
  • Preparation of Generic and Site-specific Health and Safety Plan
  • Preparation of Generic and Site-specific Quality Assurance/Quality Control Plan
  • Initial Project Investigation
  • Implementation of On-site and Off-site Field Investigation Program
  • Preparation of a Phase II Investigation Work Plan
  • Implementation of Phase II Investigation
  • Site Investigation Report
  • Coordination with State and Local Agencies

Initial Project Investigation


The initial component of the project involved the identification and review of background information regarding the former MGP site including historical facility plans, site and regional hydrogeology and prior environmental studies. This review process was instrumental in developing a focused field investigation scope of work designed to identify and define potential contaminant source areas. The following is a partial list of information sources and investigation techniques utilized in identifying likely contaminant source areas, as well as developing an overall conceptual model of the site:

  • Prior environmental studies/reports
  • Local agency files
  • State and federal environmental databases
  • Interviews with past/present property owners/occupants
  • Brown’s Directory of North American Coal Gas Facilities
  • Site reconnaissance
  • Historic aerial and site photographs
  • USGS publications concerning regional hydrogeology
  • Available geologic logs from the USGS and New York State Department of Environmental Conservation
  • Public and private supply well records maintained by the USGS, NYSDEC and Nassau County Department of Health
  • Site plans and construction drawings
  • Historic Sanborn (fire insurance) Maps

Due to the early period of operation of the former MGP site, particular attention was given to the acquisition and review of historic Sanborn Maps, historic aerial and site photographs, and site plans/construction drawings. These sources of information were utilized to evaluate former locations of MGP structures and potential source areas.

Review of available information on site and regional hydrogeology was critical in gaining an understanding of likely fate and transport mechanisms for MGP byproducts that may have been discharged to the subsurface environment and developing an overall conceptual site model. Based on this model, off-site sample locations were selected to assess impacts to potential off-site receptors.

Field Investigation Program


The field investigation for the Hempstead former MGP site included the following activities:

  • Soil Vapor Sampling – Installation of off-site and on-site soil vapor probes. Collection and laboratory analysis of soil vapor samples.
  • Surface Soil Sampling – Collection and laboratory analysis of surface soil samples from on-site locations.
  • Soil Borings/Probes and Subsurface Soil Sampling – Advancement of on-site and off-site soil borings and probes. Collection and laboratory analysis of subsurface soil samples.
  • Groundwater Monitoring Well Inventory, Assessment and Initial Sampling – Inventory, assessment, redevelopment, gauging and sampling of existing groundwater monitoring wells previously installed on-site and off-site.
  • Groundwater Probe Installation and Sampling – Installation of on-site and off-site groundwater probes. Collection and laboratory analysis of groundwater samples.
  • keyspanhmp5Groundwater Monitoring Well Installation and Sampling – Oversight of the installation and development of new on-site and off-site wells. Baseline gauging and collection of groundwater samples from all new wells for laboratory analysis.
  • Indoor Air Sampling – Collection of air samples from off-site buildings located downgradient of the site for laboratory analysis.
  • Temporary Well Installation and Sampling – Complete temporary wells to 200 feet in order to collect groundwater samples at various depths in order to assess the vertical extent of the groundwater plume.
  • Ambient Air Monitoring – Installation of fixed air quality monitoring stations at the site perimeter. Collection of air quality monitoring data at each station. Also, continuous monitoring data was collected at temporary stations established up and downwind of intrusive activities.
  • Test Pit Excavation, Field Oversight and Sampling – Excavation of test pits/trenches to confirm the location of former MGP structures or potential source areas. Field oversight, documentation and sampling services were provided during the excavation of test pits.
  • keyspanhmp6Surveying and Mapping – Coordination and supervision of surveying coordinates for all sample locations, monitoring well casing elevations and staff gauge elevations.
  • Property Access and Permitting – Provided technical support related to obtaining private property access and permit approvals with all local agencies and private entities for off-site sample locations.

Human Exposure Assessment Support

D&B provided technical support for the preparation of a Human Exposure Assessment that is being performed by others. Technical support included information regarding site history and on-site field conditions, as well as providing validated analytical results of all samples, data summary tables, sample location maps, sample depth and sample information summary tables and other pertinent information necessary for the preparation of the Human Exposure Assessment.keyspanhmp7

The objectives of the Human Exposure Assessment for the Hempstead former MGP site include:

  • Identify chemicals of potential concern (COPCs) that are related to the former gas manufacturing activities conducted at the site;
  • Identify potential pathways of exposure to people, plants and fish;
  • Estimate and characterize the potential ecological risks associated with these exposures; and
  • Indicate the need for mitigative measures to reduce potential exposures.keyspanhmp8

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