2021 Water System Study

Overview

Watch the video for information on the water system study improvements. Note: The survey at the end of the video has closed and the City is no longer seeking input on siting options. Additional question and answers are listed below.

Vea el vídeo en español (watch the video in Spanish)

On April 5, 2022, the City Council accepted the Water System Study and its Related Recommendations. The recommendations that were approved by the City Council were:
     - Construct a new drinking water treatment plant with gravity filtration and reverse osmosis.
     - Construct the drinking water treatment plant at either site 1 or 2 based on public input.
     - Site 3 is no longer being considered an option for siting so long as staff can acquire land at
       site 1 or site 2.
     - Staff should move forward with negotiation with property owners for land acquisition for the
       drinking water treatment plant and staff should begin the design of the water treatment
       plant by providing more refined site layouts for the drinking water treatment plant.

Location options as stated in the above recommendations:

Background on Why a Water System Study Was Conducted

In 2019, the City of Northfield in conjunction with the Minnesota Department of Health (MDH), had water samples taken as part of the Fourth Unregulated Contaminants Monitoring Rule (UCMR 4). As part of the analysis, manganese was analyzed within the drinking water. Samples were taken as part of the UCMR 4 and additional manganese samples were taken in 2020. The results are listed below. Since most of the wells are over 100 ug/L, guidance level for MDH, the City is analyzing ways to lower its manganese. Additional information on manganese in the City’s Drinking Water can be found at https://www.ci.northfield.mn.us/1293/Manganese-in-Drinking-Water

Well numberManganese level (ug/L)Average manganese level (ug/L)
0223.70, 40.2, 28.130.67
03139.00139.00
04136.00, 119, 344199.67
0597.20, 83.6, 81.087.27
06112.00112.00


Lowering manganese levels

As part of analyzing different ways to lower the manganese within the City’s drinking water supply, the City developed a Request For Proposals (RFP) for a Water System Study. As an outcome of the RFP, the City contracted the Water System Study with Bolton and Menk, Inc.

The Water System Study was to conduct the following items:

  • Gather and review background information
  • Water Demand Projections
  • Evaluation of the Existing Water Supply
  • Evaluation of the Water Quality
  • Evaluation Water Treatment Options
  • Treatment Plant and New Source Water Well Siting Study
  • Space Needs Assessment
  • Staffing Review and Analysis
  • Draft Report
  • Public Outreach
  • Final Report

Question and Answers

Q:    Why does the City need to build a water treatment plant?

A:    The City's water is above a Minnesota Department of Health guideline for manganese and
        is not recommended to be consumed by infants under 1 year old. The way to lower the level
        of manganese in the water is by providing treatment.

Q:    What treatment will the City water provide?

A:    The new water treatment plant will use gravity filtration with reverse osmosis to remove iron,
       manganese and hardness minerals or calcium and magnesium.

Q:    It seems like the treatment plant is very expensive, were there other options studied to
        provide safe drinking water for all residents?

A:    Yes, the City's consultant studied 3 treatment options:  gravity filtration, gravity filtration with
        reverse osmosis and gravity filtration with lime softening.

Q:    Why was gravity filtration with reverse osmosis selected as the best treatment option for the
        City?

A:    Gravity filtration with reverse osmosis was selected because of the removal of manganese
        in the drinking water, the resiliency to future contaminants, the quality of water provided
        and the reduction of chlorides being added to drinking water through home water softeners
        thus resulting in lower levels of chlorides being discharged to the Cannon River.

Q:    Did the City explore other treatment options, such as pressure filters, to remove iron and
        manganese?

A:    Yes, however they were not recommended as on option based on the scale of the drinking
        water system.

Q:    Will the water be softened?

A:    Yes, the water will be softened to roughly 90 milligrams per liter (mg/L) or what is considered
       moderately hard.

Q:    Do I need to further soften my water?

A:    The decision to further soften or not is up to residents, however, the City is recommending
        residents do not further soften their water.

Q:    Will the water hardness level cause issues with my high efficient appliances or void their
        warranties?

A:    No, the Minnesota Department of Health states that “If your water’s hardness is greater
        than 7 grains per gallon or 120mg/L, then you might need a water softener to ensure your 
        appliances run well.” The City will provide water with roughly 90 mg/L or lower than the
        Minnesota Department of Health’s recommended softening level.

Q:    When will the new water treatment plant be providing filtered and softened water to the
         Northfield properties?

A:    The water treatment plant is expected to be operational in 2025 to 2026.

Q:    When the water treatment plant becomes operational, will it cause water chemistry issues?

A:    When the water treatment plant first becomes operational, there will be a change in
        the water. City staff will conduct additional hydrant flushing to remove any built up
        discoloration in the water so that residents will be able to see the benefit of the new treated
        water as soon as possible.

Documents

Water System Study RFP

Bolton & Menk, Inc. Proposal

August 2021 City Council Presentation

Water System Study

Water System Study Open House Presentation February 22, 2022