Limestone Quarry Expansion: Illinois
Leggette, Brashears & Graham, Inc. (LBG) completed a hydrogeologic assessment to evaluate whether a proposed aggregate limestone quarry expansion might change the flow and/or water quality of a nearby spring. Although the spring flow had historically been contaminated by agricultural and domestic discharges, maintaining the aesthetic value of this aquatic natural resource was considered necessary for public-relations support.
SCOPE OF WORK
LBG completed the following hydrogeologic assessment and modeling activities to evaluate the potential impacts of proposed quarry expansion and dewatering activities on spring flow:
Desk-top study of available geologic, hydrogeologic, and geochemical data
Site reconnaissance of the proposed expansion area and nearby quarries
Geologic and hydrogeologic characterization of the expansion area Karst mapping using tracer-dye studies Groundwater flow and quality modeling using reference and site-specific data Post-processed model output using ArcGIS
THE GEOLOGIC MODEL
LBG’s assessment revealed that near-surface bedrock hosts a void network connecting surface water and ground water to the spring. Sinkholes providing recharge to the spring in the planned expansion area are significantly less prevalent than in the surrounding area. A main conduit to the spring was not identified. However, LBG concluded that ground water flows sub-horizontally along dipping and bedding planes to intersecting solution-enlarged vertical conduits oriented along a dominant joint set, and eventually the spring.
THE SOLUTION: MONITORING, REGULATORY COMPLIANCE AND PUBLIC RELATIONS
To minimize any potential impact to the spring flow, LBG recommended that selective rock quarrying in the expansion area be conducted in a controlled fashion. As the quarry expansion continues, LBG will meter the flow of the spring using continuously-recording water-level monitors. Monitoring and related permitting efforts include direct dialogue and regulatory compliance with the US Army Corps of Engineers, state regulatory agencies, county officials, and the local community.