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Projects

Locust Point Quarry Hydrogeologic Study

Groundwater studies determine the effects of quarry dewatering on groundwater elevations, surface water flow, and residential well performance.
  • Sump pumps dewatering limestone quarry pit - Gannett Fleming

    Our predictive model estimates the effects of quarry dewatering on local groundwater elevation and surface water flow.

  • Stream flow gaged at flume downstream of quarry water discharge point - Gannett Fleming

    Our firm has collected water data for more than 25 years to support quarry permit renewals.

Client
Hempt Bros., Inc.

Location
Silver Spring, Monroe, Middlesex, and South Middleton Townships, Cumberland County, Pennsylvania

Our Role
Groundwater Monitoring, Geophysical Survey, Groundwater Modeling, Permitting.

Data
Size
74-square-mile study area
Duration
In Progress
Outcomes
  • Groundwater and surface water monitoring was used to understand quarry dewatering impacts
  • Groundwater elevation and stream flow monitoring and groundwater flow model support quarry expansion permitting
  • Our predictive model estimated dewatering rates from the proposed quarry.

Residential complaints to the Pennsylvania Department of Environmental Protection (PADEP) about decreased well performance and increased stream flow prompted Hempt Bros., Inc., to retain Gannett Fleming to perform detailed groundwater studies to determine the probable hydrologic impact of quarry dewatering on local residential wells. The surface mine pumps and discharges up to 12 mgd into a tributary stream. 

Our firm performed detailed aquifer and geophysical studies, groundwater and surface water monitoring, and constructed a numerical model to estimate the existing and future effects of quarry dewatering on groundwater elevations and surface water flow. 

What We Did

Gannett Fleming completed extensive groundwater elevation and stream flow monitoring for a period of years using numerous digital water level recorders, three large capacity ramp flumes, and staff gages. Groundwater studies and modeling indicated that seasonal precipitation variations strongly influence the size of the drawdown area caused by quarry dewatering. As a result, our firm provided alternative mining/dewatering scenarios and developed a water supply contingency plan for approval by PADEP. 

The numerical groundwater model was constructed in 1995 and has been updated and recalibrated in 2009 and 2014. Additional investigations and permit application preparations were completed for expansion of the Locust Point Quarry in 2012 and 2015. These permitting efforts included predictive modeling as required by the PADEP Bureau of Mining and Reclamation to describe the potential effects of dewatering at the proposed expanded quarry. Field work has included placing flumes to monitor and collect stream discharge and groundwater data. Our firm is currently providing quarterly water elevation, flow, and quality monitoring to support quarry permit renewals, as necessary.

Key Features

  • In situ testing of faulted carbonate rock aquifer
  • Automated and manual monitoring of groundwater elevations and stream flows
  • The GMS-MODFLOW groundwater flow model includes simulation of a fractured media aquifer, steady state flow simulations, use of specified flow and no-flow boundaries, and spatially variable recharge and hydraulic conductivity
  • Coordination with U.S. Geological Survey and PADEP
  • Data collection to support quarry permit renewals
  • Geophysical surveys, including a very-low-frequency electromagnetic wave survey and an electromagnetic study. 

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