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Department of Transportation recommending the Board approve and authorize the Chair to sign a Covenant and Agreement between the California Regional Water Quality Control Board, Central Valley Region, and the County of El Dorado to protect future health and safety and the environment as a result of potential risk related to the possible presence of hazardous materials as defined in Health and Safety Code §25260 pertaining to the Diamond Springs Parkway Phase 1B Project, Capital Improvement Program number 72334/36105011. (Cont. 8/15/2023, Item 20)
FUNDING: N/A
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DISCUSSION / BACKGROUND
Phase 1B of the Diamond Springs Parkway Project (Project) will construct a 4-lane arterial roadway that will connect Missouri Flat Road and State Route 49 near the community of Diamond Springs. A portion of the Project will be constructed on the site of a former lime plant with recognized environmental conditions. Residual lime materials exist at various depths within the site and are currently contributing to storm water runoff with elevated pH levels.
In 2018, the Department of Transportation (Transportation) retained Aptim Environmental & Infrastructure, Inc., to provide environmental remediation support services. These services included additional site characterization work, including subsurface investigation and testing, coordination with the California Regional Water Quality Control Board, Central Valley Region (Regional Water Board), and preparation of a Remedial Action Plan (RAP) for approval and implementation.
The remediation work identified in the RAP will be carried out as part of the future construction contract for the Project. The remediation work will involve excavating approximately 20,000 cubic yards of residual lime material from the site, of which a portion will be re-used as blended engineered fill, with the remaining disposed at an approved offsite facility.
Since the County’s remediation scope will not remove all the residual lime material...
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