After a mine shuts down, M&A helps convert an industrial wellfield to a supply source that can meet the demands of future residential or industrial water users.
Client: International mining company - Time frame: 1988–present
- Location: Confidential
Until the late 1990s, this industrial wellfield not only produced groundwater to meet on-site processing needs, but it also provided municipal supplies to local residents. Located near a perennial-to-intermittent river reach, the wells pumped water from deep basin-fill sediments and could meet peak demands exceeding 16,000 AFY. After industrial operations were shut down, water use declined steadily in the ensuing period as closure operations came to completion.
Currently, the operator pumps less than 10 percent of historical rates, providing only municipal supplies for the adjacent town. In response to the reduced demand and the need to ensure a reliable, high-quality water supply for the town, the owner decided to abandon several of the original wells and replace them with two new production wells. M&A oversaw associated drilling, testing, and well construction operations.
We continue to help this client develop strategies for meeting the future water demands of a growing local population and to evaluate opportunities for supplying potential industrial users. Ongoing monitoring and modeling tasks provide information about the relationship between deep pumping and conditions within the shallow aquifer that is connected to the stream.
M&A evaluated wellfield operations and performance, projected potential sustainable yields, and developed recommendations for abandoning, rehabilitating, and replacing various production wells. As part of this evaluation, we characterized downhole flow and water quality conditions at both existing and new production wells. Field characterization efforts (which we designed and oversaw) entailed collecting critical data using a variety of techniques — including spinner flow-meter logging, borehole geophysical logging, and discrete-zone sampling. This data was used to identify well completion intervals that would maximize yield while minimizing arsenic and TDS concentrations.
M&A also designed and oversaw the installation of a monitoring well network to assess the degree to which water levels in the shallow alluvial aquifer system respond to pumping from the basin-fill aquifer. The well network covers a wide area and monitors a range of depths within the alluvial and basin-fill aquifers.
Groundwater levels are recorded continuously using downhole pressure transducers and dataloggers. M&A also monitors streamflow and vegetation conditions via visual inspection, automated cameras, and analysis of satellite imagery, focusing on a 6-mile reach of the river adjacent to the wellfield. This reach is characterized by perennial to intermittent flows. To support the evaluation of streamflow and riparian ecosystems, we worked with our client to interface with field biologists and conservation groups.
M&A is in the process of developing a groundwater flow model to project long-term drawdown in both the shallow alluvial and deeper basin-fill aquifers in response to pumping. We are integrating long-term monitoring data and hydrogeologic information into the model.
Our client wanted to explore strategies for developing water supplies for potential future industrial uses on its property. In response, M&A developed an economic analysis of the value of groundwater produced from its wellfield compared to the value of alternative water sources in the region. Results of this analysis were used to evaluate project feasibility.
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