Remedial Action Plan - Rochford Field - Newhall Remediation Project

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The EC will encompass the entire Rochford Field site (shown in Figure 3). The EC design is consistent with direct exposure and PMC ECs approved by the CTDEEP at a number of sites in Connecticut. Section 22a-133k-2(f)(2)(B) of the RSRs requires that ECs be designed and constructed to meet the following conditions: 1) Function with minimum maintenance: The pavement surface covering portions of the EC will require similar levels of maintenance as the Town budget presently provides for. The grassy areas of the EC will be landscaped and maintained by the Town of Hamden. Maintenance will include cutting and watering the grass and properly winterizing the drainage system. In addition, periodic inspections of the EC will be conducted as part of an operation and maintenance (O&M) program to ensure that the control continues to function. 2) Promote drainage and minimize erosion or other damage to the control: The EC will be graded, and constructed with a gravel layer on top of the impermeable membrane to promote drainage and minimize erosion and other damage to the control. 3) Accommodate settling and subsidence of the underling soil so as to maintain the control’s integrity: Materials placed as part of EC construction will be compacted to prevent subsidence and settling. The O&M inspection program will include observations for evidence of significant settling or subsidence. If observed, repairs will be made to preserve EC integrity. Following construction, an O&M Plan will be prepared for the Town to use to ensure compliance with the above noted CTDEEP conditions. 4.2.3 Stormwater Management Stormwater drainage from the subject site was evaluated by Haley & Aldrich based on a recent 2012 study by others of seven basins within the Newhall Area of Hamden, CT (DTC Inc., “Newhall Area Drainage Study, Hamden, Connecticut” March 27 2012). Our evaluation was conducted using the methodologies presented in the Connecticut Department of Transportation Drainage Manual. The site is located along the northern edge of a 51-acre basin in the northeastern corner of the Newhall Neighborhood. Runoff from the site and this drainage basin discharges from a storm drain outfall located to the north of the former Hamden Middle School. Site stormwater runoff was estimated by comparison of the site to the 51-acre drainage area. Runoff estimates were then evaluated using a runoff coefficient selected for the existing site conditions and runoff coefficient selected for the future condition of the site with an impermeable barrier. Runoff estimates of both conditions were compared and indicate that the presence of an impervious cover will not significantly change existing drainage conditions. Refer to Appendix D for additional details. Based on the above analysis, the final design will incorporate the following stormwater management elements: Prior to installing the impermeable barrier, the existing downgradient stormwater drainage infrastructure will be inspected, cleaned, and if necessary, repaired. 17
The impermeable barrier will be sloped to drain to a perimeter water collection system. The perimeter collection system will be connected to the existing stormwater drainage infrastructure proximate to the subject site. Refer to Figures 3A and 5 for additional drainage details. 4.3 Monitoring Effectiveness of Remedial Approach over Time 4.3.1 Plan & Schedule for Inspection Quarterly inspections of the EC will be conducted by the Town to confirm damage to the EC has not occurred. During inspections, the site will be walked such that all areas of the EC are directly observed. Inspection will include visual observation to confirm that there are no breaches which would impair the integrity of the EC. Repairs to the EC will occur within a reasonable amount of time following discovery of any breaches which would impair the integrity of the EC. Documentation of the inspections and repairs will be maintained by the Town of Hamden. 4.3.2 Plan & Schedule for Maintenance Preventative maintenance activities will include filling seams or cracks and sealing asphalt surface portions of the EC on a five year basis. 4.3.3 Groundwater Monitoring Plan Long term groundwater monitoring will be conducted to demonstrate compliance with the RSRs and confirm the effectiveness of the EC at preventing migration of liquids through the release area. Details of the long term, natural attenuation monitoring plan are included in Section 5. 4.3.4 Plan & Schedule for Reporting 4.3.5 ELUR In accordance with Section B.3.1.(2). of the Consent Order, on or before 15 days of completing remedial actions, the Town of Hamden shall certify to CTDEEP in writing that the remedial actions have been completed as approved. For the first five years after installation of the EC, reports documenting inspections, repairs, and maintenance will be provided to CTDEEP on an annual basis. Subsequent reports will be provided to CTDEEP every five years. An ELUR will be filed for the site by the Town of Hamden as part of remediation. The ELUR will be used to render soils beneath the EC “inaccessible” and “environmentally isolated” and will include restrictions to prevent activities that could disturb the EC or underlying polluted soils. 18
Page 1 and 2: REMEDIAL ACTION PLAN ROCHFORD FIELD
Page 3 and 4: TABLE OF CONTENTS LIST OF TABLES LI
Page 5 and 6: LIST OF TABLES Table No. Ia Ib IIa
Page 7 and 8: The 4.84 acre Rochford Field is a l
Page 9 and 10: levels of VOCs; cyanide was detecte
Page 11 and 12: 2. CONCEPTUAL SITE MODEL 2.1 Genera
Page 13 and 14: groundwater flow patterns and obser
Page 15 and 16: presence of the oil scrap metal cor
Page 17 and 18: On-site soil washing Bioremediation
Page 19 and 20: 3.4 CTDEEP Selected Remedy In 2005,
Page 21: The depth of the liner and gravel w
Page 25 and 26: 5. LONG-TERM GROUNDWATER MONITORING
Page 27 and 28: TABLE Ia SUMMARY OF ANALYTICAL RESU
Page 49 and 50: TABLE Ib SUMMARY OF ANALYTICAL RESU
Page 69 and 70: TABLE IIa SUMMARY OF ANALYTICAL DAT
Page 71 and 72: TABLE IIa SUMMARY OF ANALYTICAL DAT
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TABLE IIa SUMMARY OF ANALYTICAL DAT
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TABLE IIb SUMMARY OF ANALYTICAL DAT
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APPENDIX B Selected Figures from Pr
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NEWHALL ROCHFORD FIELD WINCHESTER A
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BLAKE CIRCLE MILL ROCK ROAD MIDDLE
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TABLE X Page 1 of 3 SUMMARY OF CONC
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TABLE X Page 3 of 3 SUMMARY OF CONC
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Remedial Action Plan - Rochford Field - Newhall Remediation Project

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