Residential Well Monitoring & Impact Mitigation Projects
Upper Scioto West Interceptor Sewer Project, City of Columbus, Ohio: Eagon & Associates provided monitoring, assessment, and remediation of impacts on local groundwater resources as a result of the installation of a large sewer interceptor consisting of a 10 foot diameter tunnel 80 feet below the surface, bored about 5½ miles through the Columbus Limestone. Over 500 residential wells were located in the vicinity of the sewer project. The sewer was installed by tunneling through the aquifer in which most of the residential wells in the area were completed. A pre-construction well survey was conducted within the project area in order to collect baseline water-level and water-quality data. Eagon & Associates responded to and investigated over 300 complaints from local residents relative to groundwater quantity and quality impacts attributed to the construction dewatering. Information obtained during the baseline well survey and from routine groundwater level data monitoring was used to determine the validity of complaints. Eagon & Associates maintained an extensive database of groundwater level data from network piezometers and residential wells that was used for preparation of hydrographs and potentiometric surface maps. Fracture trace analysis and a detailed bedrock topography map were used to predict areas where tunnel grouting could potentially impact groundwater quality. Groundwater quality monitoring also was performed at residential wells located in areas identified as vulnerable to grout contamination, and any affected wells were remediated or replaced. All management and coordination of well replacements was conducted by Eagon & Associates personnel.
Village of St. Henry, Ohio: Eagon & Associates prepared technical specifications for the construction and testing of a new well field for municipal water supply, provided oversight of well construction, performed data collection, and analyzed pumping-test results for each well. Data collection included a well survey of surrounding residential wells and monitoring of water levels in representative wells during pumping tests to assess potential impact on groundwater levels as a result of well-field operation. Assistance to the Village was provided to develop a remediation policy for wells affected by pumping. Conditions in the aquifer were monitored during startup of the well field and recommendations were provided relative to specific requirements for residential well system upgrades and new wells where appropriate. A systematic program for water-level data collection was developed so that conditions could be reviewed periodically and modifications to the program could be made as required. As a result of these measures, legitimate claims were handled and remedial measures were made in a manner that was fair and acceptable to all concerned. Water-level monitoring has continued and a water-level map to define the cone of influence is updated routinely. These data also are used to monitor well performance based on static and pumping water levels. The well field continues to be operated and managed without any serious controversy. As demand for water increased, it became necessary to develop two additional supply wells at a separate location. However, owing to the individual well yields that could be obtained and interference due to the close proximity to the other well field, only a modest increase in net capacity could be developed. The analysis revealed that well sites located beyond the existing cone of influence will be needed to obtain additional well capacity.
Big Walnut Sanitary Trunk Sewer Extension, City of Columbus, Ohio: Eagon & Associates provided assistance to the project engineer relative to the definition, documentation, and evaluation of the groundwater conditions within the vicinity of a planned trunk sewer extension in Columbus, Ohio. Available published information regarding residential wells, groundwater quality, and bedrock topography were compiled and reviewed prior to conducting a residential well survey. A survey of approximately 150 residential wells was completed. Groundwater quality samples were collected and pumping tests were performed to document the existing condition of residential wells in the project area. A comprehensive database was generated that provided valuable information for evaluating well complaints. Pumping tests were performed to collect data regarding the hydraulic characteristics of the local bedrock and unconsolidated aquifers. This information was used to evaluate potential construction and alignment scenarios and determine dewatering feasibility. Hydraulic data obtained from the pumping tests were used to develop a groundwater flow model. Open trench excavation and tunnel construction methods were evaluated using the model, and the model simulations were used to predict potential impacts to residential wells for each construction alternative.
Quarry Dewatering: This project involved the assessment of existing and potential impact of quarry dewatering on residential wells in the vicinity of Big Darby Creek, west of Hilliard, Ohio. Initially, the investigation concentrated on an area where many residents were contemplating litigation. Groundwater levels and flow conditions were characterized and facts were established to validate or disprove each claim. Remedial actions were in the form of new wells or deeper pump settings when appropriate. The second phase involved a well survey over a three mile radius to document pre-mining conditions for a new quarry. Potential impacts were evaluated and wells at imminent risk were replaced or deepened. A network of existing wells was established to monitor water levels as quarry operations progressed and complaints of well problems were investigated whenever received. The baseline data proved invaluable to substantiate conclusions on actual impacts and remediation required.
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