Village of Cold Spring, New York Brownfield Site Investigation and Remedial Alternatives, Analysis of a Former Manufactured Gas Plant Site, NYSDEC ERP Program
Posted on June 12, 2015
Client: Village of Cold Spring/New York State Department of Environmental Conservation
Location: Cold Spring, New York
Project Type: Brownfield Site Investigation and Remedial Alternatives, Analysis of a Former Manufactured Gas Plant Site, NYSDEC ERP Program
Project Cost: $130,000
The firm was retained by the Village of Cold Spring to implement a Site Investigation and Remedial Alternatives Analysis (SI/RAA) of a former Manufactured Gas Plant (MGP) site, located in the Village of Cold Spring. This project was completed under the New York State Department of Environmental Conservation’s (NYSDEC’s) Environmental Restoration Project (ERP) program. The ERP program was established by the State of New York to assist local municipalities with the remediation and redevelopment of Brownfield properties. Funding of the program was made possible through the New York State Clean Water/Clean Air Bond Act of 1996.
The objectives of the Cold Spring former MGP site SI/RAA project included (1) identify the nature and extent of contamination associated with the former MGP; (2) identify the potential impacts of this contamination to human health and the environment; and (3) select appropriate remedial actions needed to address the site-related contamination.
D&B successfully completed the project for the Village of Cold Spring on schedule and under budget.
Background and Site History
The Cold Spring former MGP site is located in the picturesque Village of Cold Spring, New York approximately 250 feet east/southeast of the Hudson River. Currently, there are no above ground structures present on the site that were associated with the former MGP. The site is currently an unpaved parking lot and lawn owned by the Village. The Cold Spring Boat Club property is located directly to the west of the former MGP site.
The Village of Cold Spring and surrounding land became a major industrial hub of the Hudson River Valley in the 19th century that was centered around the West Point Foundry located directly to the south of the Village. During this period, the foundry was one of the largest munitions manufacturers in the United States. The former MGP site was just one small part of the Village’s industrial history.
Details concerning the history and operation of the former MGP are very limited but the facility appeared to have been in operation as early as 1868. Historical maps indicated that the former MGP was no longer in operation by 1897, an operational period of less than 30 years. In addition, based on the limited records, it can be concluded that it was a rather small operation compared to most MGP facilities. Based on the estimated period of operation, it was concluded that the MGP was a coal carbonization plant and did not operate as an oil/gas plant, a process that was only common after 1900. Therefore, it was highly unlikely that liquid petroleum feed stock was ever stored or used at the former MGP site.
Site Investigation Scope of Work
Shortly after signing the contract with the Village of Cold Spring in July 2008, D&B developed a SI/RAA Work Plan and Citizen Participation Plan in an expedited basis in order to have the field investigation work underway by the coming fall as desired by the Village. D&B worked closely with the NYSDEC project manager in developing the project scope of work during the work plan development. Through this cooperative effort and with D&B’s extensive experience in the characterization of former MGP sites, the work plan was approved by the NYSDEC with only minor comments by the end of August 2008 and the field investigation was underway by September 2008. Since much of the fieldwork had to be completed within the adjoining Cold Spring Boat Club property, D&B worked closely with the operators of the club to ensure that their normal activities were not disrupted during the execution of this work. The field investigation scope of work was completed on schedule and under budget and included the following elements:
- Geophysical Survey – Prior to undertaking any intrusive activities, a geophysical survey of the former MGP site was conducted utilizing terrain conductivity, electromagnetic technologies and ground penetrating radar (GPR).
- Surface Soil Sampling – In order to assess if MGP-related contaminants were present at the ground surface, a total of 8 surface soil samples were collected in the vicinity of the former MGP site for chemical analysis.
- Soil Boring and Subsurface Soil Sampling – A total of 25 soil borings were completed up to 30 feet in depth as part of the field investigation using direct push sampling techniques, i.e., Geoprobe.
- Monitoring Well Installation and Development – Five groundwater monitoring wells were installed using pre-packed wells screens and a Geoprobe direct push sampling unit.
- Monitoring Well Sampling and Water Level Measurements – The five newly installed monitoring wells, along with one existing well were sampled for chemical analysis.
- Vapor Intrusion Sampling/Indoor Air Sampling – In order to determine if soil vapor intrusion was a potential exposure pathway for VOCs associated with the former MGP, two sub-slab soil vapor samples and two indoor air samples were collected from inside a building located adjacent to the former MGP site.
- Surface Water and Surface Water Sediment Sampling – The NYSDEC collected a total of six sediment samples from three locations on the Hudson River downgradient of the former MGP site as part of the investigation in order to determine if MGP-related constituents have impacted river sediments.
Key Findings of the Site Investigation
As with all our remedial investigation projects, the generated field and chemical data was evaluated by D&B’s highly experienced technical staff in order to characterize the hydrogeology of the site and surrounding area and to assess the nature and extent of contamination in the affected environmental media such as soil, soil vapor and groundwater. D&B determined the potential impacts to human health and the environment associated with the identified contamination by undertaking a qualitative human health and environmental exposure assessment that took into consideration the completed site characterization, the current and future land use of the site and surrounding areas and the location of sensitive environmental receptors.
The completed investigation identified MGP tar and related chemical constituents in subsurface soil and groundwater within and downgradient (southwest) of the former MGP site. The most significant tar impacts were present to the south and southwest of the former gas holder in an area generally restricted to the Village public parking lot and surrounding lawn areas. However, the MGP tar impacts did not appear to extend into adjacent residential properties located to the east. The most significant MGP tar impacts were located at least two feet below grade in the parking lot area and, therefore, direct exposure to this contamination was not expected under existing conditions.
The vertical extent of tar impacts in downgradient areas appeared to be limited to a maximum depth of 13 feet below grade. A low permeable clay unit was identified up to 20 feet thick in the area of the former MGP site which likely limits the vertical migration of tar. In general, MGP- related contaminants including VOCs and PAHs were found at lower concentrations in downgradient areas when compared to soil in the immediate vicinity of the former MGP. Evidence of free phase NAPL or tar was not detected in the monitoring wells located downgradient of the former MGP site. MGP-related contaminants that were detected in downgradient monitoring wells included several VOCs and PAHs and found at only low concentrations.
The soil vapor intrusion study completed at the adjacent building indicated that vapor intrusion of MGP-related contaminants present in soil and groundwater underlying the structure is not occurring and, therefore, is not considered a potential route of exposure.
Based on a southwesterly flow of groundwater, it is likely that groundwater containing MGP-related contaminants will discharge to the Hudson River. However, sampling of river sediments performed by the NYSDEC did not identify these contaminants at significant concentrations.
Remedial Technology Assessment and Recommended Remedial Alternative Evaluation
D&B developed site-specific remedial action objectives (RAOs) for the former MGP site in consultation with the NYSDEC based on the completed site characterization and the human health and environmental exposure assessment. Areas of the site and the surrounding properties and associated environmental media that warranted remediation were then identified. In accordance with the NYSDEC Division of Environmental Remediation draft technical guidance for site investigation and remediation dated December 2002 (DER-10), D&B completed a review and assessment of technologies and response options, and institutional controls, which have been demonstrated to be successful for remediating sites with similar MGP-related contaminants.
The remedial technologies that were considered potentially applicable to the site included:
- Institutional Controls
- Excavation and Off-site Disposal
- In-situ Solidification
- Hydraulic Barrier Technologies
- Surface Barriers
Based on the screening of the above technologies, excavation and off-site disposal and in-situ solidification were the only remedial technologies and process options retained for further consideration in the remediation of the site, either as remedial alternatives in and of themselves or in combination to form alternatives. Institutional controls were also retained in combination with these technologies/process options to form the possible remedial alternatives that could be utilized at the site and achieve the site-specific RAOs. In accordance with the NYSDEC DER-10, the alternatives were also compared against the NYSDEC remedy selection criteria including overall protectiveness to the public and the environment, short term and long term effectiveness and impacts, reduction in contaminant toxicity, and volume and implementability.
Based on the preliminary evaluation of the remedial technologies discussed above, the technologies selected for further consideration were developed into five potential remedial alternatives that could achieve the site-specific RAOs, including:
- Alternative 1: No remedial actions with institutional controls;
- Alternative 2: Excavation and off-site disposal of all soil exceeding SCOs;
- Alternative 3: Partial Excavation and off-site disposal of soil containing the most significant contamination (hot spot removal) with institutional controls;
- Alternative 4: Partial excavation and off-site disposal of soil containing the most significant contamination (hot spot removal) with in-situ solidification of the remaining soil and institutional controls; and
- Alternative 5: In-situ solidification of contaminated soil with institutional controls.
Based on the evaluation of the remedial alternatives described above, excavation and removal of “hot-spot” soil and establishment of institutional controls, as discussed in Alternative 3, was determined as being able to achieve the site-specific RAOs and met the NYSDEC remedy selection criteria and, therefore, was the recommended remedy for the site. Although implementation of Alternative 2 would provide for the removal of a larger volume of contaminated soil, this alternative would have required the demolition of nearby buildings, extensive excavation beneath public roadways, and the major disruption of Village residents and businesses. Therefore, it was not considered a viable option and is not necessary to achieve the stated RAOs for the site. Although Alternative 4 would also have met the remedy selection criteria, the implementation of the in-situ solidification along the Hudson River would have more significant short-term impacts. Placement of the in-situ solidification in this area would attempt to provide a barrier to mitigate further migration of the MGP material. However, due to the absence of any current impact to the Hudson River and the presence of sea walls along the Hudson River that are likely already providing some mitigation of migration of contaminants, implementation of Alternative 4 was not recommended for the site. Since the majority of the MGP-impacted material is readily accessible for removal and off-site disposal, Alternative 5 where a majority of the MGP-impacted soil will remain on-site, although immobilized, was not recommended.
The SI/RA Report provides additional detail concerning the recommended remedy for the former MGP site. The NYSDEC has formally approved the report and is currently drafting the Proposed Remedial Action Plan (PRAP) for the site.
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