Early this year, four sites along the Cowlitz River were explored to investigate horizontal collector wells as a source of water to replace the Mint Farm aquifer. Initially, three sites were tested but less than desirable results prompted consideration of a fourth site. In the end, two sites proved feasible in regards to capacity but water quality testing showed high levels of iron, manganese, hardness and silica (download water quality test results and comparison, PDF 128 kb), the same constituents which are the cause of many of the current customer complaints.
Water quality may improve over time, with high-volume, long-term pumping eventually displacing groundwater and drawing more water from the Cowlitz River. However, the degree and rate of change is unknown and would require additional investment and testing to prove or disprove it.
The next steps of testing would involve drilling a larger test well, multiple observation wells and ongoing water quality tests. The technical consultant provided two testing options ranging in cost between $180,000 and 435,500.
The decision facing the City Council and BHWSD Commissioners was whether to approve this additional testing or cease further investigation.
In a special joint meeting on July 28, City Council and BHWSD Commissioners decided to cease further investigation of collector wells and reconsider Mint Farm improvement options. Later this year, staff will recommend next steps to address taste and odor complaints and propose methods to evaluate treatment options for silica removal. Download a schedule of work.