Remedial Action Plan - Rochford Field - Newhall Remediation Project

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4. SOIL REMEDY 4.1 Overview In accordance with Alternative 4 outlined in Section 3, proposed remedial measures to be used at Rochford Field include construction of an engineered control (EC), placement of an ELUR to restrict access to soil below the EC, and natural attenuation groundwater monitoring. The following sections address the remedial strategies will be used to bring Rochford Field into compliance with the RSRs. An overview of the proposed site design for Rochford Field is shown in Figure 3. The site design includes baseball and little league fields, landscaped areas and an entrance gate. A detailed profile view is shown on Figure 4. Plan notes and details are shown on Figure 5. 4.2 Engineered Control Design and Construction Section 22a-133k-2(f)(2) of the RSRs permits the use of an engineered control (EC) to physically isolate polluted soil from direct exposure to humans and/or infiltrating storm water from polluted soil to protect groundwater quality. CTDEEP published a “Guidance Document, Engineered Controls pursuant to Section 22a-133k-2(f) of the Connecticut Remediation Standard Regulations” dated February 2009 and revised November 2010. This guidance document describes an engineered Control as: A permanent physical structure designed to safely isolate pollutants which would otherwise not comply with the self-implementing remedial options allowed in sections 22a-133k-1 through -3 of the Remediation Standard Regulations (RSRs). An EC is a “variance” which requires the Commissioner’s approval. It generally contains inspection, maintenance and reporting requirements, the recording of an Environmental Land Use Restriction (ELUR), and the posting of financial assurance to ensure such measures will be sustained into the future. In accordance with 22a-133k-2(f)(2)(A)(iv), CTDEEP requires a variance to construct a direct exposure EC to prevent direct human contact with polluted soil. In the 2007 Remedy Selection Plan, CTDEEP has requested, and as such, approved construction of an EC at the subject site. 4.2.1 Overview The EC will be necessary to address RDEC and PMC compliance through the physical isolation of polluted soil. The EC will include an impermeable membrane and 2 ft of fill material; the EC design is shown in Figures 4 and 5 and described in the following section. Generally, the EC will be constructed with a gravel layer (above the impermeable liner) to facilitate drainage, graded to promotes runoff, resistant to erosion, and designed to account for settlement. The EC design will be locally modified to include: Shallow rooted trees with approximately 90 percent of root mass within two feet of the ground surface and no tap root (see Figures 4, 5 and 6); Footings for a retaining wall and sidewalk to be constructed along the perimeter of the site (see Figures 4 and 5). 15
The depth of the liner and gravel will be varied as needed to account for the excavations for the trees and footings. The EC will require similar levels of maintenance as the Town budget presently provides for. The site will consist primarily of grassy and landscaped areas which will be maintained as recreational ball fields. The uppermost surface of the EC will be inspected quarterly and repairs will occur within a reasonable amount of time following discovery of any breaches which would impair the integrity of the EC. An ELUR will be placed on the site restricting disturbance of soil beneath the impermeable liner. The site sprinkler system piping will be located in fill material above the impermeable membrane. There is no anticipated vapor intrusion pathway, and no enclosed structures will be constructed on top of the EC. There are no surface water bodies or wetlands located on the site that would be expected to interfere with the EC. 4.2.2 Engineered Control Design The EC will be constructed in six layers, as follows: A 6-inch thick soil cushion, to be placed on or about the existing ground surface/grade (or at the base of excavations for trees, posts or footings); A 40 MIL HDPE impermeable membrane (less than 1 x 10-6 cm/sec permeability); A 6-inch layer of gravel; A permeable geotextile fabric to protect the gravel layer from siltation; A 6-inch layer of common fill; A top layer consisting of either a 6-inch layer of topsoil covered with grass (thicker topsoil will be used around root balls for trees), or a 6-inch layer that includes 3 inches of subbase (gravel) and 3 inches of concrete pavement. Existing subsurface utilities will be abandoned in place prior to beginning construction. Drainage layer piping will be laid around the perimeter of the site and will discharge into the existing storm sewer in the northwest corner of the parcel. Because the EC construction includes raising the grade by 2 ft, a brick retaining wall and fence will be constructed along the perimeter of the field. Six of the existing groundwater monitoring wells will be maintained for future monitoring (RF- HA108-MW, RF-HA108-MWD, RF-HA207-MW, RF-HA123-MW, RF-HA115-MW and RF- HA110-MW). The wells will be protected during construction, and extended 2 ft to meet the finish grade. One new groundwater monitoring well (RF-HA301-MW) will be installed in the southwestern portion of the park. The wells will be completed with flush-mounted, locking caps. If wells are lost during construction, they will be replaced before the end of construction. Refer to Figure 2B for well locations. 16
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: 3.4 CTDEEP Selected Remedy In 2005,
Page 23 and 24: The impermeable barrier will be slo
Page 25 and 26: 5. LONG-TERM GROUNDWATER MONITORING
Page 27 and 28: TABLE Ia SUMMARY OF ANALYTICAL RESU
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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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