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I. Purpose and Scope <br /> This plan ("Plan'') outlines the groundwater monitoring well installation and sampling that will occur at the <br /> Colorado Stone Quarries(CSQ)Marble Mine to monitor groundwater for hydrocarbon constituents associated <br /> with the October 11, 2019 diesel fuel spill. The spill released approximately 5,500 gallons of diesel to the fill <br /> material near Portal 4 as a result of an accidental overfill of a generator day tank. <br /> On October 16, 2019, Colorado Stone Quarries (CSQ) reported to the Colorado Division of Reclamation, <br /> Mining and Safety (DRMS) and the Colorado Department of Public Health & Environment (CDPHE) that a <br /> diesel fuel release occurred on October 11, 2019 from an above-ground storage tank which impacted the <br /> underlying fill material below the tank and an associated generator. CSQ personnel discovered diesel fuel <br /> daylighting within a sump, approximately 1,200 feet downgradient from the release point. CDPHE issued a <br /> release spill tracking # 2019-0587 and noted that the DRMS will be the lead agency on monitoring the <br /> remediation. <br /> HRL Compliance Solutions Inc. (HRL) was contracted on October 23, 2019 to perform an initial onsite <br /> inspection and evaluate the impacted area to provide support for initial clean-up in conjunction with <br /> remediation, sampling, waste management and monitoring support. <br /> The following information provides details regarding the groundwater monitoring well installation, <br /> development, and sampling & analysis of the groundwater within and/or below CSQ's road fill material. This <br /> plan is designed to outline the frequency of sampling, sampling and analytical procedures, and contingency <br /> plans should detections above the regulatory thresholds be observed. It should be noted that changes in the <br /> nature and scope of this project may directly affect the specifics of this plan. <br /> II. Plan Applicability <br /> This plan is applicable to groundwater monitoring at the CSQ quarry within the former channel of Yule Creek. <br /> A total of four(4)groundwater monitoring wells are proposed;one will be installed upgradient from the release <br /> point and two will be installed downgradient of the release point.The fourth monitoring well,which has already <br /> been installed within the sump basin on November 15, 2019, is located approximately 1,200 feet from the <br /> release point. (See Figure 1) <br /> It should be noted that the sampling and analysis components of this Plan are currently being implemented for <br /> the sump well to monitor groundwater quality in the sump area. The other three wells (MW 1 — 3) located <br /> between the sump and the point of release have not yet been installed. MW 1-3 were initially planned for <br /> installation during late December 2019 or early January 2020. However, due to equipment failure, winter <br /> weather, freezing of the subsurface soils, and snow accumulation preventing access, installation of MW 1-3 <br /> was postponed until the Spring/Summer 2020. <br /> III. Monitoring Well Installation <br /> A groundwater monitoring well installation Notice of Intent (NOI) was submitted to the Colorado State <br /> Engineer's Office on November 12, 2019, satisfying the required 72-hour notice before installation was <br /> completed. The NOI is valid for a period of 90 days from the time of submittal. Therefore, due to the delay in <br /> installation of MW 1-3 a new NOI will need to be submitted as the previous one will have expired. <br /> l <br />