CROTON POINT SANITARY LANDFILL & RAILROAD 1 LANDFILL NYSDEC Site #360001 POST CLOSURE MONITORING AND SAMPLING REPORT Fifth Quarter Reporting October – December 2018 February – March 2020 May 2021 Louis J. Vetrone Deputy Commissioner 914-813-5429 Melissa-Jean Rotini Director of Environmental Management Operations 914-813-5416 1 Croton Point Sanitary Landfill & Railroad 1 Landfill NYSDEC Site #360001 Post Closure Monitoring and Sampling Report TABLE OF CONTENTS I. II. III. IV. V. VI. VII. VIII. Introduction and Purpose Post-Closure Sampling Methodology a. Sample Nomenclature b. Environmental Sampling and Locations Map Groundwater Sampling & Inspections Surface Water Sampling & Inspections Sediment Sampling Leachate Sampling Leachate Collection System Metro-North Source Contributions Recommendations for Modifications to Sampling Protocol Tables Table 1(RFW-1D) - Table 1(RWS-12S): Croton Landfill Groundwater Table 2(SRF-1A) - Table 2(SRF-3B): Surface Water Table 3: Sediment Table 4a: Leachate (Pump Station) Table 4b: Leachate (RR Sump) Table 5: Metro-North Source Contributions Table 6(RR-1) - Table 6(RR-7): Railroad 1 Landfill Groundwater Table 7(RR-R) and Table 7(RR-L): Railroad 1 Landfill Surface Water Appendices Appendix A - Laboratory Reports 2018 Appendix B - Laboratory Reports 2020 Appendix C - Laboratory Reports 2021 1 Croton Point Sanitary Landfill & Railroad 1 Landfill NYSDEC Site #360001 Post Closure Monitoring and Sampling Report I. Introduction & Purpose Pursuant to the Post Closure Monitoring and Sampling Program presented in the Croton Point Sanitary Landfill and the Railroad 1 Operation and Maintenance Manuals, environmental sampling occurs during the fifth quarter. This Report provides data for samplings taken on: a. October 30, 3019, through December 5, 2018; b. February 27, 2020, through March 12, 2020; and c. May 4, 2021, through May 25, 2021. The environmental media sampled and the results contained herein include groundwater, surface water, marsh sediments, and leachate, and were analyzed for baseline parameters. The analytical results contained herein are presented to:   Fulfill the requirements of the Post Closure Monitoring and Sampling Program as outlined in the Closure Operation and Maintenance Manuals. Present the results of laboratory sample analysis for this sampling event. II. Post-Closure Sampling Methodology The sampling and laboratory analysis presented herein were conducted as described in the Environmental Monitoring Program section of both the Croton Point Sanitary Landfill Operation and Maintenance Manual and the Railroad 1 Landfill Operation and Maintenance Manual. The Westchester County Bureau of Labs and Research provided all sampling reports. Anomalies and comments regarding testing are included in the analysis reports attached hereto as Appendices AC. a. Sample Nomenclature As described in the Post Closure Monitoring and Sampling Program, the following sample nomenclature was used in collecting samples and presenting laboratory analytical results, except where noted:    Duplicate samples are denoted by capital letters A and B Surface Water Samples Tellers Point = SRF-1 Public Beach = SRF-2 Eastern Channel of Croton Marsh = SRF-3 Groundwater samples are identified by the respective number of the well from which they were taken, as designated on the following location map. 2 Croton Point Sanitary Landfill & Railroad 1 Landfill NYSDEC Site #360001 Post Closure Monitoring and Sampling Report b. Environmental Sampling and Locations Map 3 III. Groundwater Sampling & Inspections As part of the post closure monitoring effort 17 groundwater monitoring wells are sampled for the Croton Landfill, and eight (8) groundwater monitoring wells are sampled for the Railroad 1 Landfill. The wells selected for sampling were installed during the RIFS effort and are identified as groundwater monitoring wells. The results of the sample analysis are presented in Table 1 for Croton and in Table 6 for Railroad 1. Note: Due to the time of year that the 5th Quarter Sampling occurred, frozen conditions prevented the collection of the 2020 Soil and Marsh Samples. As part of the groundwater sampling effort, the condition of monitoring wells was inspected and remains unchanged. Monitoring wells RFW-3S, 5S, 9, and 13 are identified in the RIFS report as leachate sampling points, but are not included in groundwater sampling. However, these leachate monitoring wells were physically inspected and their condition remains unchanged. IV. Surface Water Sampling Post-closure monitoring includes sampling of three surface water monitoring locations. These sites were selected to provide representative samples from areas most susceptible to possible impact from the landfill, i.e. the public beach (SRF-2) and eastern channel of Croton Marsh (SRF-3), and to provide a location for background surface water quality monitoring, Tellers Point (SRF-1). Duplicate samples were taken at SRF-1 and 3. SRF-2A and B were taken at opposite ends of the bathing beach. Sampling results are provided in Table 2 for Croton and Table 7 for the Railroad Landfill. V. Sediment Sampling Post-closure monitoring included three locations for sediment sampling. The results of sediment sample analysis are presented in Table 3. VI. Leachate Sampling Pump Station 2 (PS2) was selected as the leachate sampling point for the Post Closure