any signidicant leakage through the cap, will be noticed right away and could be qqickly remedied to maintain the cap's integrity. Deed restrictions will ensure that this future use will not result in unacceptable exposure to contaminants. Because this remedy will not allow for unlimited use and unrestricted exposure to wastes, within five years after completion of remedial action, a five year review will be conducted. This evaluation will be done to ensure that the remedy continues to provide adequate protection of human health and the environment. IX- DOCUMENTATION OF SIGNIFICANT CHANGES The remedy presented to the public in the November 1992 PRAF' proposed Feasibility Study Alternatives 2 and 4B, design and construction of an engineered multimedia capping system with a lnachate seepage collection system, a atonnwater management system, an active gas collection system, and environmental monitoring. Although no comments or new information were received during the comment period for the PRAP which would fundamevtally change the nature of the State's preferred remedy, there have been some minor modifications/clarifications of the remedy based on the commeilts received. The leachate collection system will have sufficient storage capacity to avoid discharging leachate to the sewer system during high flow events; the stormwater management system will eliminate any detrimental ' discharge of sedirnonta Ce Che 1Iud.u~~niver; ana vegetative planting6 in specific areas of the landfill cover will provide a conducive habitat to various forms of wildlife while not compromising the cap's integrity with deep root systems. FIGURE I LEGEND Amblenl Alr Sampllng Locallon 0 VtntLocatlon Haverstraw Bay AIR SAMPLING LOCATIONS (CARBONtlENAX TUBESbPHASE I A Amblenl Air Sampllng Location 0 Vent Sampllng Location UR CANISTER BAUPUNG LOCAnoNs EVACUATED CAMSTEAS)-PHASES IL Hudson Rlver Not.: Walls RFW-lS. 55 and 93 .n U1.d 10 Montlor Laach.1. iROUNDWATER SAMPLING LOCATIOE (WESTON MONITORING WELLS) PHASE ISedlmenl Sampling Location t nmn $3 Croton Bay Alr, Groundwater and Sediment Sampling Locations - Sampllng Lowtlons Resampled Durlng PHASE U SEDIMENT SAMPLING LOCATIONS TYPICAL DETAIL A Nor 10 Y*LE FIGURE 4 wqrms ww--n - vr w-in yuN( ' ~ = l I l ! - ~ ym ag 11.L13s '09E W d P n=-wnb -1 'WyPyP SAN P38.L- WM w* dmna i-~ 91Y lm.l-3 - fJ2 ~ l W l l V w m 4 11.fX)S '09'2 W d P n-b roi YParlP S W 1 w - z Yl-lrv P3aL-lllM .1~1003 ' 0 9 md ~ P m -1 PolD )olt W M .L)3S ww -n@mo3 ~ n nu v w n=-+=m ON - K YlWlN ~1wlN ~ TABLE 2 COST COMPARISON TABLE CAPITAL, OPERATIONAL AND MAINTENANCE COSTS FOR REMEDIAL ALTERNATIVES AT THE CROTON POINT SANITARY LANDFILL, SITE #360001 i ALTERNATIVE i CAPITAL COST 1 1 I \NETPRESENT WORTH i I NOTE 2 I 1:NO ACTION I I $366,000 1 $3,917,000 i3 :OFFSITE 1 DISPOSAL i1$3,945,530,000 I1 $3,948,050,000 I I L i SEDIMENTS i $4,435,000 i I 4A :MARSH I NOTE 1 I I I O&M COSTS YEARLY I 1 $4,435,000 NOTE 3 1 I I I I I ! Note 1: Costs are based on the following senario, nsite disposal of approximately 45,000 cubic yards. For o fsite disposal costs increase to $8,935,000. Alt 4B has n capital costs. Note 2: net present worth based on a 30 year perioq and a discount rate of 5% using 1992 dollars & idcludes capital costs. Note 3: There are no annual costs associated direcdly with this alternative. TABLE 3 mS ARDS ITE IA AND GUI ANCE M R N ACTION-SPECIPIC SCGs 6 NYCRR 50: 6 NYCRR 182: 6 NYCRR 200: 6 NYCRR 212: 6 NYCRR 257: 6 NYCRR 360: 6 NYCRR 371: 6 NYCRR 375: National Primary and Secondary Ambient Air Quality Btandards Endangered and Threatened Species of Fish and WildlLfe General Air Provisions General Process Emission Sources Air Quality Standards Solid Waste Hanagement Facilities Identification and Listing of Hazardous Waste Inactive Hazardous Waste Disposal Site Remedial robr ram CHEMICAL-SPECIFIC SCGs USEPA Safe Drinking Water Act (SDWA), MCLs and MCLGs (40 CFR Part 141) 6 NYCRR Parts 700-705: NYSDEC Water Quality Regulations for Sufface and. Groundwaters ' 10 NYCRR Subpart 5-1: NYSDOH Maximum Contaminant Levels, public Water Supplies NYSDEC Air Guide 1 (1991 Printing) Guidelines for the Control of Toxic Ambient Air Concentrations - LOCATION-SPECIFIC SCGs 6 NYCRR Parte 662-665: Freshwater Wetlands Regulations National Historic Preservation Act (16 USC 470-470 et seq.) EXHIBIT A: ADMINISTRATIVE RECORD CROTON POINT SANITARY LANDFILL WESTWESTER COUNTY, N.Y. ID NUMEER 360001 I "Final Feasibility Study Report for: Croton Point Sanitary L ndfill," prepared for Westchester County by Velzy-Weston, Inc.; June 1 6 2 confirmed to September 1992. I "Final Remedial Investigation Report for: Croton Point Sanita Landfill," with appendices, prepared for Westchester County b Weston, Inc.; June 1992 confirmed to September 1992. "Contract Documents, Final Design Plans, Specifications, and 1 Information for Bidders for Croton Point Landfill Closure",