Wellhead Protection Program Monitoring:

Based on the amount of time it takes a drop of water to travel from its source, through the Mint Farm aquifer and to the City's wellfield, a boundary was created to define the limits of the aquifer and establish an area for wellhead protection. 


As part of its Wellhead Protection Program, the City collects groundwater samples from deep sentinel wells surrounding the Mint Farm wellfield every six months to look for changes in water quality. In addition to compliance sampling required by the Department of Health, the production wells are also sampled annually as part of wellhead protection.  For a summary report and laboratory results for each sampling event conducted to date, click on the following links:

The City uses a live data engine to compile and analyze the data contained in the semi-annual Water Quality Reports.  This allows the data to be trended and visually displayed such that large volumes of data can be more easily monitored and interpreted.  An example dashboard look is provided here; copies of the complete workbooks for each of the wells can be downloaded using the following links:

Tableau Screenshot

  • Wellhead Protection Sampling Analyte List - A complete list of the analytes tested for as part of wellhead protection sampling including health based screening levels.  To define the risk to human health if an analyte is detected at a concentration which exceeds the screening level, a "criticality value" has been assigned to each analyte based on carcinogenity, mutagenicity, reproductive effects and overall toxicity.
  • Monitoring Well Sampling Program - A list of routine DOH test panels and special interest analytes originally recommended for semi-annual sampling events including recommended testing frequency, EPA test method and estimated laboratory costs. 

Sampling for wellhead protection uses a series of sentinel wells strategically located around the perimeter of the Mint Farm wellfield to establish a line of defense for advance warning of potential migration of contaminants from nearby industrial and commercial sources.

WHPA Well Map

  • Deep Monitoring Wells Construction Report - A detailed record of the geologic formation of deep monitoring wells DW-1 through DW-9 based on visual inspection of the cuttings produced during drilling and physical measurement made by instruments lowered into the hole.
  • Shallow Monitoring Well Construction Report - A summary of the drilling activity for the construction of the first set of shallow monitoring wells.  Provides the location, drillers well report, construction details and geologic log for wells SW-1 through SW-7.
  • Mint Farm Wellfield Source Approval (less appendices) - In accordance with WAC 246-290-139, this report was submitted to the Washington State Department of Health for regulatory approval of the Mint Farm wellfield.  It summarizes the initial planning, engineering and hydrogeological evaluation, well logs and water quality information for each of the four production wells.  
  • Wellhead Protection Program - The WHPP was developed to protect the groundwater source and comply with WAC 246-290-135 (3). The Department of Health approved the plan in March 2010 and it was incorporated in the City's 2012 Water Master Plan Update.
  • Water Supply Protection Ordinance No. 3209 - This ordinance supplements the WHPP to minimize the risk of contamination and provide a means of enforcement, while still allowing economic development which does not pose unreasonable risk to the aquifer. Staff continues to work with Cowlitz and Columbia counties to adopt similar ordinances to protect the groundwater supply.
Last updated: 6/19/2018 1:49:56 PM