Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Groundwater Modeling topic
No spam. Unsubscribe anytime.
Dennis Water District approves $94,000 townwide groundwater model to assess wastewater discharge
Summary
The Dennis Water District voted Oct. 24 to hire Callahan Consulting for $94,000 to build a townwide groundwater flow model intended to evaluate how proposed wastewater discharge sites could affect the district’s supply wells; the board discussed data needs, timeline and test-well costs before approving the contract.
The Dennis Water District on Oct. 24 approved a $94,000 contract with Callahan Consulting to develop a townwide groundwater flow model aimed at evaluating potential impacts from the town’s wastewater discharge facilities on the district’s supply wells.
Maura Callahan of Callahan Consulting told the board the model will start with the U.S. Geological Survey base model, convert it to Modflow, then apply telescoping mesh refinement for higher resolution near the district’s wells. "The immediate purpose of the model is to evaluate the potential impacts from the town's wastewater discharge facilities so that we can protect the water quality at the district's supply wells," Callahan said. She outlined steps including compiling boring logs and pumping-test data, calibrating the model with historical pumping tests, running sensitivity and uncertainty analyses, and producing scenario runs to map zones of contribution and plume travel times.
Board members pressed on data gaps and cost drivers. Staff said some historic pumping-test records exist in town files and in the reports produced by CBM/ CDM Smith, but older records are sporadic and will require staff time to assemble. Callahan said limited site-specific work (test borings and monitoring wells) may be needed at about $15,000–$50,000 depending on depth and mobilization; she estimated the initial model build and calibration could be completed in roughly three months.
Vice Chair Bob Perry described the project as a defensive investment and framed the model as a tool to use both to evaluate proposed discharge sites and for future planning: "We're playing defense to the tune of some significant cost," Perry said, while adding that a townwide model would offer long-term value even if a particular site proved not to threaten the district’s wells.
The board discussed funding options and whether to stage work. Staff noted an existing operating appropriation for technical engineering services and a reserve fund are both possible sources; several members agreed the board could authorize an initial contract to get the model in place and then pursue site-specific work only when the town identifies a discharge location.
A board member moved to authorize the chair to sign the contract with Callahan Consulting for $94,000; the motion was seconded and the board voted in favor.
Next steps: staff will finalize the contract and begin collecting available records (boring logs, pumping tests and CDM/CBM Smith files) for the consultant. The model will be used immediately for systemwide assessments and later for site-specific modeling if and when the town selects a discharge site.
