Consider Recommendation to City Council Authorizing Well Siting Study Requests for Proposals for Wells #9 and #10

Purpose:
The purpose of this case is to consider a recommendation to City Council to authorize the solicitation of Requests for Proposals for a Well Siting Study for proposed municipal groundwater wells #9 and #10. 

Background:
The City of Ramsey’s existing municipal wellfields are comprised of 8 wells. Wells 1 and 2 are located in the southeastern portion of city limits, while Wells 3 through 8 are located in the south-central portion
of the City. All 8 wells draw water from the Tunnel City-Wonewoc aquifer and range in depth between 316 and 390-feet.

Attached is a copy of the 2021 Feasibility Study containing detailed information on the city’s existing water supply system and groundwater aquifers.  The following italicized text copied from pages 24 and 25 of the study confirm the city’s source water aquifer is anticipated to continue to produce potable water to meet present and foreseeable future demands, and that the city should plan additional well sites to ensure static water levels will remain sufficiently above top of aquifers to meet MnDNR thresholds.

At present, there is no reason to assume that the current source water aquifer for the City of
Ramsey will not be able to supply potable water for the foreseeable future. The City of Ramsey’s
source water aquifer and wells are able to meet present day demand and appear to have a
noticeable but temporary radius of influence on the surrounding aquifer. The wells are able to
support high pumping rates with specific capacity showing acceptable drawdown alongside the
aquifer’s ability to recharge to static levels within a day of pumping.

The City of Ramsey will need to balance water demand with drawdown to meet Minnesota
Department of Natural Resources drawdown thresholds described in MN Rule 6115.0630
Definitions Subps.15 and 16. Two thresholds are in place and regulate that wells must not
drawdown MnDNR assigned static water levels to within 50-percent and 25-percent to the top of
aquifer. These threshold values are set by a MnDNR observation well and would typically be
enforced if long term issues are observed. Thresholds for the City of Ramsey could become a
concern if there is extended pumping within a single well or pumping by multiple wells in close
proximity.

In summary, it is SEH’s opinion that there is a 95% to 99% certainty that the source water
aquifer for the City of Ramsey will continue to produce potable water to meet present and
foreseeable future demands; however, the City of Ramsey should plan additional well
sites to ensure static water levels remain sufficiently above top of aquifers to meet MnDNR
thresholds.

Single well pumping for the City of Ramsey, as depicted by Well 5 in May, 2019 saw
approximately 90 to 100 feet of temporary drawdown. This observed drawdown nears the
MnDNR 50-percent threshold; however, the pumping extended multiple days and recharged
within the same time period back to static levels. This supports the ability of the wells to supply
continued water and ability to stay within prescribed State Statute.

A single well also creates a radius of influence drawing down adjacent water levels. The zone of
influence for a single well was observed and modeled to be approximately two to three thousand
feet, meaning that a single well pumping at approximately 800 feet will not cause a significant
drawdown in another well. When multiple wells are being utilized such as under heavy day
demand or under 2040 conditions the modeled and observed drawdown in nearby wells sees a
substantial drop in static water levels from that of a single well pumping. Modeled drawdown
during present heavy day conditions depict 30-40 feet of drawdown approximately 1,500 feet
around the wellfield. After pumping stops, the aquifer will recharge to static levels within one or
two days. In general, it appears new well sites should be spaced at least 1,500 to 2,000 feet
away from existing wells to ensure a pumping scheme that gives the aquifer sufficient time to
recharge.

Future well sites should attempt to balance the City’s current economics, well spacing, and take
into account the underlying geology. The City of Ramsey should continue to utilize the current
source water aquifer for both a water quantity and a water quality standpoint. The source water
aquifer is underneath protective “confining” units that appear to inhibit the influence of new water
from brining contaminants to the City’s wells and will likely produce consistent water quality
unlikely unconfined sources such as surface water that may have a highly variable water quality.

Additional considerations for well Sites should take into account the thickness of the two
hydrogeologic units that make up the source water aquifer. The Tunnel City aquifer is not as
prolific an aquifer as the Wonewoc aquifer, meaning that the Wonewoc aquifer is a more
economical source of water. Figure 15 in Appendix D depicts three potential well sites taking into
account these issues. Well Site Area A has Tunnel City aquifer thickness ranging from 100 to 150
feet and Wonewoc thickness ranging from 45 to 60 feet. Well Site Area B has Tunnel City aquifer
thickness ranging from 0 to 80 feet and Wonewoc thickness ranging from 35 to 100 feet. Well
Site Area C has Tunnel City aquifer thickness ranging from 90 to 100 feet and Wonewoc
thickness ranging from 15 to 35 feet. All of these sites have potential for potable water sources,
but a test well will need to be installed to confirm their viability. As opportunities to investigate
these well sites present themselves the City should consider these as potential well sites.

Figure 15 in Appendix D of the Feasibility Study identifies two potential municipal well sites that will be explored in greater detail as part of the Well Siting Study.

In alignment with the Feasibility Study findings and recommendations, staff proposes to solicit Requests for Proposals from engineering consultants with significant experience in siting wells for municipal water supply systems to assist the city in determining the most desirable site(s) for two new municipal wells and the supporting wellhouses currently programmed for construction in 2027 and 2030. 

Notifications are not required at this time. 

Timeframe:
Staff estimates this case will take up to 15 minutes to present and discuss. 

Observations:
Detailed information on the geology of soils underlying the City of Ramsey can be found in the Anoka County Geologic Atlas, which can be viewed through links on the University of Minnesota Digital Conservancy website at https://conservancy.umn.edu/items/1d10e060-80aa-4db0-af8f-5514b14c0192.  Other websites include significant detail on this subject, such as the Know the Flow website at https://knowtheflow.us/2016/12/geologic-atlas-reveals-whats-under-the-surface/.

Attached is a copy of Anoka County Atlas Plates 3 and 4 that show the Surficial Geology and Quaternary Stratigraphy across Anoka County, which can be used by the selected engineering consultant to select the best location for the city’s next two municipal wells.

The engineering consultant will also utilize the Metropolitan Council’s groundwater model to ensure the new wells will have sufficient groundwater volumes for the city’s needs both now and in the foreseeable future.

Other attached reference materials include;

• 44-page 2020 Metropolitan Council Report “Water Supply Planning in the Twin Cities Metropolitan Area (2005-2020)”
• 4-page summary of the 2020 Metropolitan Council Report “Water Supply Planning in the Twin Cities Metropolitan Area (2005-2020)”

Tentative project schedule:

• May 19th – Public Works Committee recommends City Council authorization to solicit Requests for Proposals for a Well Siting Study for proposed municipal groundwater wells #9 and #10.
• May 26th – City Council authorizes solicitation of Well Siting Study Requests for Proposals.
• May 27th – Staff solicits Well Siting Study Requests for Proposals from applicable engineering consultants.
• July 21st – Public Works Committee recommends City Council acceptance of Well Siting Study Proposals and award of contract to the lowest responsible proposer.
• July 28th – City Council accepts Well Siting Study Proposals and awards contract to the lowest responsible proposer.
• July 29th - December 18th – Well Siting Study completed

Alternatives:
Alternative #1: Motion recommending City Council authorization to solicit Requests for Proposals for a Well Siting Study for proposed municipal groundwater wells #9 and #10.  

Alternative #2: Motion of other. 

 

Copies of the associated 2026 – 2035 Capital Improvement Plan sheets, sheets 295 and 296, are attached for reference. As noted, the CIP level cost estimate for the study is $50,000. All costs for the study will be paid from Water Funds.  

Staff recommends alternative #1 to ensure an adequate supply of water is maintained for municipal water supply system users.  

Motion recommending City Council authorization to solicit Requests for Proposals for a Well Siting Study for proposed municipal groundwater wells #9 and #10.