Site 78 getting closer to cleanup
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In October 2009 Picatinny Arsenal submitted a draft final Proposed Plan for Site 78 (PICA 013) to the USEPA and the NJDEP. PicatinnyArsenal stated that this plan was based on the Feasibility Study for Site 78 (PICA 13) and that it “...include[s] the agreement with EPA that monitoring will ‘follow the frequency established in the Area B and Area E Remedial Designs’…..” A pilot study involving injection of sodium lactate into the core of the Arsenal’s groundwater plume to evaluate in situ enhanced biodegradation for reduction of chlorinated solvents in ground water was completed in 2004. Chlorinated volatile organic compound (VOC) concentrations were reduced significantly from the time of injection to the final pilot study sampling in 2007. Natural degradation rates there were calculated to be between 1.9 and 3.8 years for the contaminants of concern:(trichloroethene, cis-1,2-dichloroethene, and vinyl chloride). Based on its evaluation of its own criteria the Army selected as its Preferred Response Action for groundwater option GW-2 : Monitored Natural Attenuation and Land Use Controls. The Proposed Plan states the following:
“MNA is the most appropriate remedy for the groundwater plume at Site 78 (PICA 013) because it achieves the threshold criteria and provides the best balance of tradeoffs relative to the five balancing criteria. Because the plume was significantly degraded when investigations began (due to the ambient groundwater environment), and subjected to enhanced degradation through injection of sodium lactate, RAOs will be achieved through MNA in a time frame only slightly longer (5 – 7 years longer) than that required for all other alternatives. Moreover, MNA will achieve RAOs at lower cost and with no further disturbance to natural resources (i.e., wetlands) in this area of Picatinny Arsenal.” |
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The present worth cost of GW- 2 is estimated to be $310,000. It is estimated on the basis of historical data trends that it will require approximately 13 years to “restore groundwater to concentrations below the LOCs in the AA [area of attainment].” In contrast, Response Action GW-3 – Enhanced Reductive Dechlorination, Post-Remedial Monitoring, and LUCs is estimated to cost $480,000 and require approximately 2 years of semiannual injections followed by 5 years of post-remedial monitoring to achieve the remedial action objectives (RAOs). The USEPA provided comments on the Proposed Plan in correspondence dated December 2, 2009. As a general comment the USEPA noted that:
“…Chlorinated volatile organic compounds were found in the groundwater which discharges into the Green Pond Brook. Although significant concentrations of these contaminants were not found in the surface water, it may [be]appropriate to include a discussion of the pore water evaluation. Additionally, the long-term monitoring program should include pore water sampling.”
According to the US Geological Survey, pore water is defined as “water filling the spaces between gains of sediment.” Many of the comments related to minor issues and to data that did not need to be included in the proposed plan. However, several USEPA comments did cite specific instances of language in the proposed plan which a layperson, unfamiliar with such documents, could conceivably deem to be either confusing or misleading. Some of these comments are reproduced below: ‘7. Human Health Risk Assessment, Site 78 (PICA 013), risk table, page 7 – The risk table shows the cancer risks and non-cancer hazards associated with the evaluated pathways. The table should be edited to include the cancer risks and non-cancer hazards associated with future residential use |
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of the groundwater, and the cancer risks and non-cancer hazards associated with the supplemental on-site worker evaluation. The text should also describe the current/future industrial/research worker cancer risk as being at the upper-bound of the acceptable risk range instead of referring to it as being "within or below". 9. Human Health Risk Assessment, Site 78 (PICA 013), fourth paragraph, page 7-8 a. Based on Table 2, vinyl chloride exceeded the LOC in 54 of the samples, therefore, the argument presented that the risk is associated with the maximum detected concentration does not provide a realistic view of the contamination. Although the risk estimate may have used the maximum detected concentration for the supplemental risk evaluation, the fact remains that a large percentage of the samples exceed the acceptable drinking water standards for vinyl chloride. This should not be hidden from the audience. b. The last paragraph in the risk assessment section typically provides rationale for why an action is or is not necessary at the site. Based on the information in the rest of the risk assessment section (at least once it is updated using the comments above), the text in this paragraph should focus on the cancer risks being above the acceptable risk range for several populations (future residential and on-site workers using the most recent groundwater data) and above the acceptable drinking water standards and highlight that this indicates a need for a remedial action. This will then support the text on page 9 in the second column in the Groundwater section that states "Through the Remedial Investigation, it has been determined that a response action is necessary for the site 78 (PICA 013) groundwater." Information that indicates that there is no risk to human health should be deleted. |
