base upon which to develop a final investigative program for the CPSL. One of the later reports concerning the site impacts, prepared for the USEPA in 1986, was utilized by the NYSDEC to classify the landfill as a cjass 2 inactive hazardous waste site under New York State law. A list 0% the previous investigations and study efforts is included in Exhibit A of this Record of Decision (ROD). The County is currently obligated to perform a complete remddial Program in accordance with federal and State legislation as Consent Order executed in Hay of 1989 with the NYSDEC. The continues to have Federal obligations relative to CPSL v. Edwin J. Michcailian. Reimbursement of up to 759 of incurred in the design and construction of the remedial program 4s available to the County through the New York State 1986 Environmental QualMy Bond Act (State Assistance Contract IC300069). II 111. CURRENT SITE STATUS I A. Summarv of Pield Investisations: The following paragraphs summarize the components anid conclusions of the current remedial investigations performed at the sitel. This investigation was conducted in accordance with plans fonnblly approved by NYSDEC in April 1989 and encompassed two separate phases ~f work conducted in 1989 and 1991. For more detailed information regardin the individual investigations or for additibnal regional information, re er t o the appropriate report(8) listed in the Administrative Record (Exhibit A). Many of the efforts discussed below were confirmatory actions to verify the large volume of existing information available from the extensive past efforts involving the CPSL. 1 I I Given the size, volume of, and location of this landtill, a decision was reached at the conclusion of the Phase I RI t o place he site into an early remedial action program. The NYSDEC and the County cknowledged that as a minimum the remediation at CPSL would include an eng'neered landfill cap system and authorized the design of a cap in early 19 0. It is this decision that has resulted in the final design plans that have been completed by Gibbs and Hill and are currently under contrbct for construction. The ROD acknowledges these facts and after comparison t o other alternatives in the Feasibility Study and considera ion of public input, selects the early remedy as a component of the fin 1 remedy for CPSL. I 6 I I I i i I 1 iI 1 B. S-rv of Site Conditions: For ease of reference, the following information sum/narizes the main characteristics of the Croton Point Sanitary Landfill site (all values are approximate): andf fill Area t o Remediate: Contaminated Media: 115 acres Landf illed wbstes Marsh sed+ents Leachates & Gas EmisCions 1 1 Regionally, groundwater in the unconsolidated aquife (shallowest and therefore threatened/contaminated by the site) flows to t e south-southeast towards Croton Bay and the Hudson River. However, the lo a1 flow pattern is such that the shallow groundwaters in the immediate vicin ty of the site flow outward from the center of the landfill in a radial attern, with greater gradients towards the eastern channel of the Crot n Marsh and towards the Haverstraw Bay in the vicinity of the closed each area. The presence of the Hudson river in close proximity to the wa te mass perimeter makes discussion of a "shallow groundwater aquifer" probl matic in nature. The groundwater in question is considered by many to be b ackish due t o tidal influences and is not a viable water supply source. The entire area is serviced by public water supplies. The deep groundwat r existing below the low permeable layers appears to be unaffected by the $ , The geology and hydrogeology of the site are Complex+ contamination at the site appears t o be contained within mass and the on-site The landfill is underlain by sands, organic peats/clays southeastern portions lacustrine deposits over prominent lodgement till outcrops at its outer and Enoch's point. This results in a the outcrops and towards the more The bulk of the of the ancient Croton river bed running southeast to northwest. the relatively high organic carbon content of the peat soils in the arsh area appear to be effectively retarding contaminant migration beyond he initial edge of fill. Although water quality standards are being exceed d in the immediate vicinity of the waste mass, it is believed that once t e site is isolated to stop the periodic leachate releases and upgradient cpean waters are routed around the landfill that the water quality will again be within standards. I Groundwater (GW) quality was evaluated through two rounds taken from +.\a 22 individual wells installed during this RI. compounds-L, concern are inorganice, many of standards. The contaminant concentrations in groundwater when the existing data base and the two rounds of current are reviewed. The most frequent inorganics iron,