Mint Farm Groundwater Project

The City of Longview and Beacon Hill Water and Sewer District (BHWSD) supply customers with groundwater sourced and treated at the Mint Farm Regional Water Treatment Plant (RWTP). The Mint Farm RWTP reliably produces drinking water that meets all regulatory standards but a 2014 survey found the majority of customers were unsatisfied.

Plans

In 2016, the City investigated going back to the Cowlitz River using horizontal collector wells but this option is no longer being considered due to disappointing water quality results. Instead, focus shifted to improve water quality through optimization of the Mint Farm RWTP.

Air Injection System

In summer, 2018 the City will commission an air injection system at the Mint Farm RWTP to increase the amount of dissolved oxygen in the water. Aeration is simple and widely used for corrosion control, but also removes hydrogen sulfide and ammonia which tend to cause taste and odor issues. Increasing the dissolved oxygen will also help harden pipe scale and prevent iron release in the distribution system. Once the system is commissioned, it will take several months to slowly raise the amount of dissolved oxygen to meet target levels. Long term, if dissolved oxygen can reduce the dependency on chlorine to maintain a stable distribution system, we hope to reduce the amount of chlorine added to the water.

Based on an average increase of $12 to $15 per month for a typical single family household, a decision was made not to remove silica. This decision may be revisited at a later date once benefits of dissolved oxygen are seen.

Treatment Plant Overview Videos

Horizontal Collector Well Feasibility Study

Exploratory wells were drilled in January, 2016 to evaluate four possible sites where a horizontal collector well could be located on the Cowlitz River. Two sites proved feasible in regards to capacity but water quality testing showed high levels of iron, manganese, hardness and silica, the same constituents which have caused many of our current customer complaints. 

View the components of the study below:

  1. Executive Summary (PDF)
  2. Cowlitz River Alluvial Aquifer Collector Well Feasibility Study (Sites 1 to 3) (PDF)
  3. Rocky Point Alluvial Aquifer Collector Well Feasibility Study (Site 4) (PDF)
  4. Water Quality Summary (PDF)
  5. Work Plan (2015 to 2016) (PDF)