HomeMy WebLinkAbout2021-02-11 Council Work Session Agenda PacketCouncil Work Session Agenda
February 11, 2021 - 5:30 pm
1. Call to Order / Roll Call
2. Northeast Water Supply Planning*
3. Unscheduled Items
4. Adjournment
*Includes Materials - Materials relating to these agenda items can be found in the house agenda packet
book located by the Council Chambers entrance, or online at the City’s website at www.corcoranmn.gov.
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Technical
Memo
Wenck | Colorado | Georgia | Minnesota | North Dakota | Wyoming
Toll Free 800-472-2232 Web wenck.com
To:Kevin Mattson, PE, Public Works Director
From:Kent Torve, PE, City Engineer
Steve Hegland, PE
Date:February 5, 2021
Subject:NE Water Supply Work Session Summary
0.0 Purpose
The purpose of this memorandum is to provide a summary of work to date on establishing a
water supply, treatment and distribution system in the NE portion of Corcoran. This memo
frames the major topics for the presentation and subsequent discussion during the February
11th Council Work Session.
1.0 Background
The City of Corcoran has planned for sewer and water for urbanized development in
accordance with the Metropolitan Council’s planning process. The 2040 Comprehensive Plan
for the Metropolitan Urban Service Area (MUSA) shows trunk facilities, routes, and sewer
capacities on a city-wide basis which allows Met Council to plan for regional expansions
along while managing growth rate and limitations on the system. The cities are responsible
for planning of water infrastructure support, although Met Council is increasing their review
efforts in this arena. As shown in the 2040 Comprehensive Plan (Attachment A), the
Northeast portion of Corcoran is within the MUSA and is intended to be serviced via a
proposed public water network.
Regional
A joint (Quad City) study was funded by Met Council to look at the feasibility of a surface
water supply (Mississippi River) for the four cities. Corcoran participated in the panel
reviewing this study and Council directed staff to stay involved with the discussions.
Corcoran is a later phase of the project, however the project would deliver treated water to
the Corcoran/Rogers border after the treatment plant and infrastructure were constructed. A
presentation was made by staff at the April 23, 2020 Council meeting.
Regulatory
Water supply oversight from regional (Met Council) and State (Department of Natural
Resources (DNR) and Minnesota Department of Health (MDH)) agencies has seen an
increase in the past few years due to high profile surface water impacts in the
east/northeast metro along with evolving public health concerns. The establishment of any
water supply network within the Twin Cities will continue to be a heavily regulated process
through these agencies.
2.0 Water Supply Agreement
The establishment of a water supply system for a community can be challenging. The timing
and costs of creating a groundwater supply, identifying property, and constructing a
distribution system are financially challenging for the “start-up” period. Individual
developments can provide smaller wells and a pressure tank for household or small
Kevin Mattson, PEPublic Works DirectorCity of CorcoranFebruary 5, 2021
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community use, but these are insufficient for fire flows and are temporary. Corcoran opted
to work with Maple Grove, to gain access to a trunk water system and the communities
negotiated an agreement in which Maple Grove would supply the Corcoran MUSA area
adjacent to the two cities boundaries. A 30-year contract was formalized on December 4,
2012 that allowed for 5 million gallons a day (MGD) peak flow, which is 1.75 MGD average
flow. A Residential Equivalent Unit (REU) was used to estimate the commercial portion of
the total flows. The contract identifies 6,334 REUs for the 1.75/5.0 MGD supply.
3.0 Corcoran Areas
Water supply was initially started in SE Corcoran for the Ravinia development and the
existing Downtown properties. As NE Corcoran developed a connection was made north of
CSAH 30 along CR 101 to serve the Bellwether development. The original water contract
was amended but limited the NE Corcoran connection to the Bellwether development at that
time. The remainder of the original contract REUs would be fulfilled through SE Corcoran as
development continued. Attachment B shows the updated infrastructure (June 2020) for the
NE area.
4.0 Northeast Water Supply Investigation
As noted previously, the NE Maple Grove connection was contractually limited to the
Bellwether development, however regional growth and I-94 improvements/interchange have
increased development pressure and interest in the area. Therefore, the City initiated water
supply planning for Northeast Corcoran and authorized Wenck to begin putting together a
feasibility study on establishing a water supply system in NE Corcoran. A Draft copy of the
feasibility study is also distributed for the Workshop. This process was paused last fall to
ensure that the current Council review and set the timeline for improvements to the system.
The planning was initiated with more detailed information (Attachment B) for facilities,
groundwater and infrastructure. Financial work included cost analysis for the Trunk Line
Area Charge (TLAC), which was updated in 2020. This analysis reviewed the NE
infrastructure needs, buildable acres and provided the TLAC per acre charge in the current
fee schedule. The costs and buildable acres vary from NE to SE, therefore the TLAC fees are
representative of those geographical separations. The implementation of this charge allows
Corcoran to establish a viable method to fund the establishment of this system.
Water supply exploration began in a bedrock aquifer known to have adequate supply in the
region. Property access was obtained and a test well (June 2020) was drilled. The
production and water quality results were sufficient in order to identify the parcel as a
location for Municipal Well No. 1, which is along CSAH 116 and Hunter Drive. Water storage
volume is driven initially by fireflow requirements and can be accomplished in two ways,
either an underground storage “tank” or a more common water tower. Both methods are
utilized in the area and examples can be provided upon request. At this time an overhead
tower is being studied. Two figures from the Draft Feasibility study are given in Attachment
C, which also relate to the recent VanBlaricom concept submittal.
5.0 Current Status
The current status of NE Water Supply planning and investigation can be summarized as
follows:
A contractual limitation currently applies to Bellwether, which could be amended.
Financial planning (TLAC) is in place for both a NE and SE Corcoran system.
Kevin Mattson, PEPublic Works DirectorCity of CorcoranFebruary 5, 2021
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A Draft Feasibility Study is complete.
Pulte has provided a concept plan for continuing the Bellwether development on the
VanBlaricom property.
Other properties in NE Corcoran are receiving development interest. This is expected
to continue based on the current economy and regional transportation (I94)
scheduled improvements.
A time frame for startup of a NE system is approximately 1.5 to 2 years based on 6
months of design, 12 months of construction and some contingency for property
acquisition, startup, etc.
Regulatory agencies are aware of Corcoran supply development to date.
6.0 Next Steps
The project is feasible from the technical and engineering perspective and as development
continues a timeline will be important for land use acquisition, trunk system installation and
supply and treatment planning. Therefore, the next steps include:
Complete the acquisition on well and treatment plant site.
Complete the Draft Feasibility Study.
Update financial analysis.
Discuss timeline to initiate construction of Municipal Well No. 1.
Site the water tower and initiate tower site investigations
Finalize trunk infrastructure loops, and easement needs
Begin preliminary design for the 18-24 month process to supply water.
Attachment A
!O
!O
!O
#*
#*
#*#*
#*
#*
#*
#*City of GreenfieldCityofMapleGroveCity of Medina
City of Rogers
Bechtold RdPio
n
e
e
r
T
r
l TrailHavenRdCounty Road 116County Road 30
Schutte Rd
Oakdale Dr
County Ro
a
d
1
0
Horseshoe Trl
Co u n t y R o a d 5 0
Larsen Rd
Willow DrHunterRdCounty Road 19Homestead Trl Cain RdRolling Hills RdCountry Rd
Mohawk DrLarkin RdFoxline DrStrehler Rd
Dassel Ln
OldSettlersR
d
Stie
g
R
d
Kalk RdMeister Rd
Maple Hill Rd93rd Ave N
Tessmer Rd
Blue Bonnet DrJubertLn456710
456750
456719
456730 4567116
4567101
4567117
Brockton Ln N109th Ave N
4567101
")55 Hackamore Rd
Morin
Lake
Scott
Lake
Jubert
Lake
Goose
Lake
Cook
Lake
456710
R u s h C reekRushCreek
South F o r k Ru sh Creek SouthForkR u sh C r eek2040 COMPREHENSIVE PLAN
3,000 0 3,0001,500
Feet ±
Path: L:\2294\100\2040CompPlan\Trunk Water System.mxd
Date: 1/15/2019 Time: 1:36:40 PM User: ShuJC0243
Existing WatermainProposed Watermain
!O Potential Water Tower Locations
#*Existing Supply Connection withNeighboring Communities
#*Proposed Supply Connection withNeighboring Communities
#*
Emergency Connection withNeighboring Communities(Normally Closed)
#*Potential Water Storage
#*Potential Booster StationPotential Future Well Exploration AreasMunicipal Boundary2040 MUSAFuture MUSA Expansion AreaParcel BoundariesStreamsLake/Open Water
Map 9-2Trunk Water System
137
Attachment B
!O
#*
#*
#*
#*
#*
#*
#*
!O4567116
456730
4567116
456710
456730
456750
456750
456710
456730
4567117
4567116
456710
Horseshoe TrBechtold RdCSAH50
WillowDrKalk RdHomestead Tr
CSAH 10
CountryRd
Cain RdFoxlineDrHunters
Rdg
HunterRdLarkin Rd
AbileneLa
Schutte RdChisholmTr
OldSettlersRdTrail Haven RdHorseshoeBendDrBrandywineRdGleason RdBlue Bonnet DrCR-116Hig h B lu ffL a
73r d
Av e N
Meister RdStrehler Rd
Maple Hill RdStieg RdOakdale Dr
97thAveN
93rd Ave N
City of CorcoranCity of Maple GroveCity of Corcoran
City of Medina
City of Corcoran
City of Rogers
12''
12''
12''12''12''
16''
12''16''12''12''12''12''12''12''12''12''12''12''12''1
2
'
'24''16''16''12''16''16''12''
12''
12''
12''16''16''
16''12''12''12''12''
12''
12''12''12''
12''16''12''
SE TLAC
NE
TLAC
Path: L:\2294\Pro\TLAC\TLAC\TLAC.aprx
6/3/2020 10:53 AM shujc0243 Layout: Trunk Water System
Figure 1
JUN 2020
Trunk Water System
CITY OF CORCORAN
2,600 0 2,6001,300
Feet ¯
Legend
Municipal Boundary
Water TLAC Boundary
Parcel Boundaries
Existing Watermain
Proposed Watermain
!O Potential Water Tower
Locations
Well/Water Treatment
Plant
#*Potential Supply
Connections with
Neighboring Comm
#*Existing Supply
Connections with
Neighboring Comm
#*Emergency Supply
Connections with
Neighboring Comm
#*Potential Booster
Station
#*Potential Water
Storage
Wetlands
Bellweather Exception
Recently Developed/
Platted (Removed from
Analysis)
Attachment C
#*!O
4567116
4567116
456730 45673097th Ave N
Country Rd
HuntersRdgCR-116StiegRd
City of CorcoranCity of Maple GroveCity of Corcoran
City of Rogers
12''16''12''12'
'
1
2
'
'16''
Path: L:\2294\19-048\Pro\WaterSupplyArea\WaterSupplyArea.aprx
6/23/2020 3:56 PM shujc0243 Layout: Corcoran NE Water Supply Area
Figure 1
JUN 2020
Corcoran NE Water Supply Area
CITY OF CORCORAN
¯1,200 0 1,200600
Feet
Legend
Municipal Boundary
Parcel Boundaries
Bellweather Parcels
Existing Watermain
Preferred Water Tower
Locations
!O Potential Water Tower
Locations
Well/Water Treatment
Plant
#*Potential Supply
Connections with
Neighboring Comm
Wetland Delineation
NWI Wetlands
#*!O
4567116
4567116
456730 45673097th Ave N
Country Rd
HuntersRdgCR-116StiegRd
City of CorcoranCity of Maple GroveCity of Corcoran
City of Rogers
12''16''12''12'
'
1
2
'
'16''
Path: L:\2294\19-048\Pro\WaterSupplyArea\WaterSupplyArea.aprx
6/23/2020 3:56 PM shujc0243 Layout: Corcoran NE Water Supply Area
Figure 1
JUN 2020
Corcoran NE Water Supply Area
CITY OF CORCORAN
¯1,200 0 1,200600
Feet
Legend
Municipal Boundary
Parcel Boundaries
Bellweather Parcels
Existing Watermain
Preferred Water Tower
Locations
!O Potential Water Tower
Locations
Well/Water Treatment
Plant
#*Potential Supply
Connections with
Neighboring Comm
Wetland Delineation
NWI Wetlands
WENCK File #2294-0048
November 2020
Prepared by:
WENCK Associates, Inc.
1800 Pioneer Creek Center
Maple Plain, MN 55359
Phone: 763-479-4200
Fax: 763-479-4242
Prepared for:
City of Corcoran
8200 County Road 116
Corcoran
MN 55340
2020 Northeast Water System
Feasibility Study DRAFT
November 2020 1
WENCK File #2294-0048
November 2020
Table of Contents
EXECUTIVE SUMMARY ........................................................................................... ES
1.0 CERTIFICATION .............................................................................................. 1
2.0 WATER DEMAND ......................................................................................... 2-1
2.1 WATER DEMAND PROJECTIONS ............................................................ 2-1
3.0 WATER SOURCE INVESTIGATION ............................................................... 3-1
3.1 TEST PUMPING ................................................................................... 3-1
3.2 WETLAND WATER LEVEL TESTING ......................................................... 3-3
3.3 RAW WELL WATER QUALITY ................................................................. 3-4
3.4 CONCLUSIONS FROM TEST WELL, COST, AND SCHEDULE ........................ 3-5
4.0 WATER TREATMENT OPTIONS .................................................................... 4-1
4.1 TREATMENT PLANT CAPACITY ............................................................... 4-1
4.2 TREATMENT PROCESSES ...................................................................... 4-1
4.2.1 Sequester Iron and Manganese ................................................. 4-1
4.2.2 Filtration ................................................................................ 4-2
4.2.3 Softening ............................................................................... 4-1
4.2.4 Softening Conclusion ............................................................... 4-2
4.2.5 Treatment Recommendation ..................................................... 4-3
4.3 CONCEPTUAL TREATMENT COST ........................................................... 4-5
4.4 SCHEDULE ......................................................................................... 4-5
5.0 WATER STORAGE ........................................................................................ 5-6
5.1 WATER TOWER SITE ALTERNATIVES ..................................................... 5-6
5.2 WATER TOWER CONFIGURATION OPTIONS ............................................ 5-7
5.3 CONCEPTUAL COST ............................................................................. 5-8
5.4 SCHEDULE ......................................................................................... 5-8
6.0 CONCEPTUAL COSTS & SCHEDULE .............................................................. 6-1
6.1 CONSTRUCTION COST ESTIMATES FOR MUNICIPAL PRODUCTION WELL .... 6-1
6.2 COST ESTIMATES FOR WATER TREATMENT PLANT USING HORIZONTAL
PRESSURE FILTER ......................................................................................... 6-1
6.3 CONSTRUCTION COST ESTIMATES FOR WATERMAIN EXTENSION FROM WTP
TO WATER TOWER SITE ................................................................................. 6-1
6.4 CONSTRUCTION COST ESTIMATES FOR WATER TOWER ........................... 6-2
6.5 BUDGET RECOMMENDATION ................................................................ 6-2
6.6 SCHEDULE FOR CRITICAL DECISIONS ................................................... 6-3 DRAFT
November 2020 2
Table of Contents (Cont.)
TABLES
Table 2-1: NE Corcoran Water Demand Projections
Table 3-1: Water Quality Parameters
Table 3-2: Corcoran Water Hardness and Standard Hardness Scale
Table 4-1: Treatment techniques
Table 4-2: Pressure Filter Information
Table 4-3: Gravity Filter Information
Table 4-4: Ion Exchange Information
Table 4-5: Nanofiltration Information
Table 5-1: Details of Proposed Water Tower Locations
FIGURES
Figure 3-1: Change of Water Level During Step Pumping Test
Figure 3-2: Change of Water Level During Constant Rate Test
Figure 3-3: Wetland Surface Water Level During Pumping Tests
Figure 4-1: Horizontal Pressure Filter Section View (courtesy of Tonka Water, filter media
shown is not specific to Corcoran)
Figure 4-2: Gravity Filter (courtesy of Tonka Water)
Figure 4-3: Conceptual Layout the Corcoran Water Treatment Plant
Figure 4-4: Proposed Site Plan for The Water Treatment Plant, Test Well and Production Well
Figure 5-1: Proposed Tower Locations and Trunk Water System Options
Figure 5-2: Composite Water Tower
Figure 5-3: Pedestal Water Tower
ATTACHMENTS
Attachment A: Test Well Log
Attachment B: Lab Reports-First Sampling and Second Sampling
Attachment C: Test Well Water Quality Summary Table
Attachment D: Municipal Production Well Construction Cost Estimates
Attachment E: Water Treatment Plant Cost Estimates
Attachment F: Watermain Extension Construction Cost Estimates
Attachment G: Water Tower Construction Cost Estimates DRAFT
November 2020 1
WENCK File #2294-0048
November 2020
Executive Summary
Corcoran is a developing community in the northwest portion of Hennepin County. Drinking
water for existing homes in this area is obtained through private wells and new
development within the Municipal Utility Service Area (MUSA) is connected to Maple Grove.
An amendment to Corcoran’s water service contract with Maple Grove limiting northeast
supply to the Bellwether development triggered the need for development and design of a
Corcoran municipal water supply system.
This Water Supply Feasibility Study for NE Corcoran, as defined by the area from east of CR
116 to west of CR 101 and from north of CR 30 to south of CR 117, was performed to
investigate water system demand, investigate water sources, evaluate treatment and
storage system options, and costs. The key findings and recommendations are:
Water Demand
Water demand currently observed in NE Corcoran and the future projected community
development was used to establish the near-term and long-term water demand through a
20-year planning period. Near-term water demand was projected for the completion of
Bellwether development. Long-term water demand was projected for full build-out of the NE
Quadrant. At buildout of the NE Quadrant, a system size of 800 gpm is justified.
Recommendation - The proposed Corcoran water supply system should be designed
to provide 250 gpm initially and expand to 1,000 gpm as development in the area
progresses. This is equivalent to 0.36 million gallons per day (MGD) to 1.44 MGD.
Water Source
NE Corcoran is well-positioned to obtain groundwater as source of the water supply system.
A test well exploration suggested a pumping capacity of at least 400 gpm can be achieved.
Water quality analysis indicated the groundwater meets all the primary (health risk)
drinking water standards, but exceeds a few of the secondary (taste, color, odor) drinking
water standards. Test results indicate relatively high iron concentration, moderate
manganese concentration, a small concentration of ammonia and high hardness.
Recommendation - The proposed location for a municipal production well is favorable
for obtaining the required water flow rate and water quality.
Treatment Methods
The primary outcome of a proposed water treatment system for NE Corcoran will be
reducing the iron and manganese concentration present in the raw water. Sequestration,
filtration, and softening options were evaluated. Preliminary sizing, concept layout, and
staging plan for the water treatment system was analyzed in this report.
Recommendations:
A water treatment plant with pressure filters is recommended. The treatment plant
will be able to provide to 500 gpm on Day 1, with the capability to expand to 1,000
gpm through a 30-year planning period. The plant site will have the capacity for
further expansions. The recommended treatment process includes:
•Horizontal pressure filtersDRAFT
November 2020 2
• Pre-chlorination upstream of the filters
• Fluoride addition
• Chlorine disinfection
• Backwash water recovery returned to the head of the plant
Water Tower
Water storage and system pressure will be provided via an elevated water tower. The water
tower will hold 750,000 gallons to provide a conservative storage volume while maintaining
regular mixing of water within the tower for good water quality. The tower will be
constructed on higher ground in the NE service area to minimize vertical construction cost
and to ensure all connections are served from the tower without the need for booster
pumps.
Recommendation - The recommended tower configurations are single pedestal style
or composite style tower for aesthetic and maintenance advantages.
Cost and Schedule
It is recommended that the City budget $7,500,000 to $8,000,000 for the NE Quadrant
water supply and distribution system construction. The cost includes construction of the
production well, raw watermain, water treatment plant, watermain from plant to water
tower, water tower, and engineering and administrative fees. Overall, this cost estimate is
similar to the previous number provided for financial planning. The costs are itemized as
follows:
Municipal Well $350,000
Water Treatment Plant $2,700,000
Watermain Extension from WTP to Tower $800,000
Water Tower $3,000,000
*Engineering, Legal, and Admin $1,100,000
Total $7,950,000
Recommendations for Schedule:
• Municipal production well: Allow at least six months for, bidding and
construction/testing. The design is currently 90% completed via the test well and
permitting process.
• Water Treatment Plant: Allow six months to one year for design and permitting and
one year for construction and startup activities. The water treatment plant would be
operational in the fall of 2022 based on a January 2021 design kickoff.
• Water Tower: It is necessary to allow nine months for design and approximately one
year for construction. Coordinate completion of the water tower with startup of the
water treatment plant.DRAFT
November 2020 2-1
2.0 WATER DEMAND
Drinking water systems are designed to provide a community with high quality, safe water
at all times, including during an extreme event such as a fire. A drinking water system
includes the water source, treatment, storage and distribution. This section discusses future
water demand predicted from community growth forecasts and historical water demand
data. Future water demand projections are used to guide sizing of the new system. The
water system will be designed to allow future expansion as the community grows.
2.1 WATER DEMAND PROJECTIONS
Previous planning for drinking water supply to the northeast quadrant of Corcoran (west of
CR 116 and north of CR 30) established the near-term and long-term water demand
through a 20-year planning period, based on available buildable acres and typical water
demand per acre per land use type (in reference to Corcoran 2020 Comprehensive Plan).
The proposed water system is necessary because water demand from development beyond
Bellwether cannot be fulfilled by the existing water supply agreement with Maple Grove.
Some developments could install private wells until the municipal supply is available (i.e.
Nelson Trucking). However, this redundancy is not always financially feasible. Long-term
water demand was projected for full build-out of NE Corcoran. Table 2-1 summarizes the
water demand projections. The water system will be designed to provide 250 gpm initially
and expand to 1,000 gpm as development in the area progresses.
Table 2-1. NE Corcoran Water Demand Projections
Water Demand Average (gpm*) Peak Day (gpm)
Near-term (Bellwether) 50 250**
Long-term (full build-out) 333 800***
*Gallons per minute
** Small systems use a higher peak factor of 5.0
*** Long-term maximum day demand sets the design flow for the water supply and
treatment systems.
For more details on development of these water demand projections, refer to the NE Water
Supply FS Update prepared by Wenck (July 3, 2019). DRAFT
November 2020 3-1
3.0 WATER SOURCE INVESTIGATION
The July 2020 Test Well memo summarized that Corcoran is well positioned to obtain
groundwater for its municipal water supply system. A 440 ft deep, 6” diameter test well
(Unique Well Number: 840775) was constructed near the proposed municipal production
well location. The well log (See Attachment A) confirms that the test well extends to the
Tunnel City-Wonewoc (formerly known as the Franconia-Ironton-Galesville (FIG)) aquifer.
Pumping tests confirmed that a production well in this location is likely to yield
approximately 400 gpm or more. Water quality samples were collected from the test well to
assist in selecting treatment techniques and equipment sizes.
3.1 TEST PUMPING
Two types of pumping tests (a step-drawdown test and a constant rate test) were
performed on the test well to estimate the anticipated flow rate of the proposed municipal
production well. The purpose of a step-drawdown test is to determine well performance
characteristics such as water level drop as pumping rate increases. The step test
incrementally increased the pumping rate from the well, beginning at 150 gpm and ending
at 275 gpm over 5 hours. The static water level of this test well is 28 ft from top of casing.
The change of water level in the well was recorded throughout the step pumping test
(Figure 3-1). Each time the pumping rate was increased, the water level in the well
decreased steeply and then leveled off, as expected.
0
50
100
150
200
250
300
0
50
100
150
200
250 0112233445566778899110121132143154165176187198209220231242253264275286297308319330341352Pumping Rate GPMFeet from Top of CasingMinutes
Corcoran Step Test
Water Level GPM GoalPumping Rate
Figure 3-1 Water Level During Step-Drawdown TestDRAFT
November 2020 3-2
The second type of pumping test was a constant-rate test at approximately 250 gpm for 24
hours (Figure 3-2). The water level in the well was measure for the extent of the pumping
period. After the pump was stopped the water level recovery was m onitored for the next 24
hours.
0
50
100
150
200
250
300
350
400
0
50
100
150
200
250 06012018024030036042048054060066072078084090096010201080114012001260132013801440150015601620168017401800186019201980204021002160222022802340240024602520258026402700276028202880Pumping Rate GPMPumping Level ft.Minutes Passed During Test
Corcoran 24 Hour Test Pump
Pumping Level GPMPumping Rate GPM
Figure 3-2 Water Level During Constant Rate TestDRAFT
November 2020 3-3
The soil and rock samples collected during development of the test well suggest that the
Tunnel City-Wonewoc aquifer was present at the expected thickness and depth below the
ground surface. These were analyzed by EH Renner and Sons well drilling company, Wenck
geologist, and Minnesota Geological Society. The results of the test well pumping tests
indicate that it is reasonable to expect Tunnel City-Wonewoc aquifer can provide the
required supply of water, and a larger-diameter production well installed near the test well
should meet the target production well capacity of at least 400 gpm. Production wells in this
aquifer in surrounding communities typically produce 400 gpm or above.
3.2 WETLAND WATER LEVEL TESTING
As requested by the MN Department of Natural Resources (DNR), a wetland in the vicinity of
the test well was monitored during pumping tests and for several days between pumping
test runs. Figure 3-3 shows the observed water surface elevation during the two pumping
tests. There was no evidence of the wetland water level significantly dropping due to test
well pumping. The pump testing results suggest that the local wetland surface water levels
are unlikely to be affected due to municipal well pumping. The DNR will require similar
monitoring during the future pump testing that will be conducted on the proposed municipal
well, which will be conducted at a higher pumping rate and for a longer time period (72-
hour).
DRAFT
November 2020 3-4
3.3 RAW WELL WATER QUALITY
Water samples were taken during the step pumping test and analyzed by Minnesota Valley
Testing Laboratory (MVTL) for the parameters regulated by the EPA primary and secondary
drinking water standards, as well as unregulated parameters such as hardness. The analysis
indicated the well water meets all the primary (health risk) standards, but exceeds a few of
the secondary standards, which are not health-based; rather, they are based on potential
aesthetic concerns such as taste, color, odor, etc. Additional sampling was completed a few
weeks later to confirm a few results from the first tests were anomalies. As is typical for this
region, the results indicate relatively high iron concentration, moderate manganese
concentration, a small concentration of ammonia and high hardness.
The concentrations of iron, manganese and ammonia detected in the raw water are not a
health risk or design complication for treatment. Instead, iron and manganese contribute to
poor taste and color at the tap if that raw water is not treated. Ammonia combines with
chlorine disinfectant ions, requiring the facility to add more chlorine to maintain the required
chlorine concentration in the distribution system.
Table 3-1 Water Quality Parameters
Constituent Concentration in
test well (mg/L)
Secondary (aesthetic)
Drinking Water
Standard (EPA) (mg/L)
Concentration found in nearby
municipal wells (TC-W aquifer)
Iron (Fe) 1.7 0.3
Loretto: 1.4 mg/L
Rogers: 1.3 – 1.6 mg/L
Dayton: 1 – 1.4 mg/L
Manganese
(Mn) 0.03 0.05 Loretto: 0.05 mg/L
Dayton: 0.2 mg/L
Ammonia
(NH3) 0.4 N/A No data available
Water hardness is a common descriptor for the concentration of calcium and magnesium
compounds dissolved in the water. Water with high hardness leaves mineral scale on
plumbing fixtures and is generally less desirable for aesthetics. Groundwater in the Corcoran
region is typically classified as “hard” or “very hard”. The test well water hardness is shown
in the following table along with the water hardness scale.
Table 3-2 Corcoran Water Hardness and Standard Hardness Scale*
Water Type Hardness Hardness
mg/L as CaCO3 grains/gallon
Corcoran Test Well 326 19.1
Soft 0 - 60 0 – 3.5
Moderately Hard 60 – 120 3.5 – 7
Hard 120 - 180 7 – 10.5
Very Hard More than 180 More than 10.5
*Water hardness scale adapted from Minnesota Pollution Control Agency webpage:
www.pca.state.mn.us/skinny-water-softners
Two lab reports for the first and second samplings are provided in Attachment B. The full
water quality data is summarized in Attachment C.
DRAFT
November 2020 3-5
The implications of the water quality data are:
• No substances were detected that are problematic for commonly used water
treatment methods.
• The test well water quality is similar to other wells in the Tunnel City-Wonewoc
aquifer in this area.
• High iron (and possibly manganese if concentrations increase slightly) will cause
aesthetic (taste, odor, and color) issues if no treatment is provided, but the
concentrations are not a health concern.
• Ammonia, although natural and low concentration, may increase the amount of
chlorine needed to maintain regulatory residual of chlorine in the distribution system.
• Water customers will still need to install home water softeners unless the water is
softened at a municipal water treatment plant.
3.4 CONCLUSIONS FROM TEST WELL, COST, AND SCHEDULE
It is recommended that future municipal production well is drilled near the proposed
location. The well is anticipated to be operational in December 2021. Since it takes about
five months from advertising a municipal well for bid to finishing installation, testing and
sampling. Design and regulatory review of the municipal well can normally be completed in
about four months; however, this time period will be reduced because Wenck already
obtained the initial permitting reviews from the DNR and MDH. Permit reviews were sought
to ensure that the proposed well location/aquifer were acceptable prior to the City’s
investment in a test well. Therefore, it is recommended the City allow at least six to eight
months for finalizing well design, bidding, and construction/testing of the municipal well.
The estimated cost for construction of the municipal production well is approximately
$275,000 to $ 300,000.
DRAFT
November 2020 4-1
4.0 WATER TREATMENT OPTIONS
A water treatment system for NE Corcoran will reduce the iron and manganese
concentrations present in the source water that would cause undesirable taste, odor and
color in the water provided to customers. A more complex water treatment system could
soften the water by removing much of the calcium and magnesium compounds. Fluoride will
be added as required by the EPA to prevent tooth decay. Chlorine will also be added to
prevent growth of pathogenic organisms in the distribution system. The proposed water
treatment plant would be constructed within the same City-owned parcel as the proposed
municipal well.
The breadth of water treatment options available to Corcoran are described in this section.
This section also addresses sizing of the treatment plant based on the demand projections
and source water quality data.
4.1 TREATMENT PLANT CAPACITY
As noted previously, the demand values show that at buildout of the NE Quadrant, a system
size of 1,000 gpm is justified. The treatment capacity will be achieved by designing a
system with two separate and similar 500 gpm treatment trains, with one being delayed
and provided at the later phase when additional capacity is necessary.
4.2 TREATMENT PROCESSES
Treatment objectives for the proposed water treatment system are driven by EPA’s National
Drinking Water Standards and aesthetic concerns. Table 4-1 summarizes water quality
constituents identified in the source water analysis that should be addressed by treatment,
as well as optional approaches for removing the hardness in a treatment plant.
Table 4-1 Treatment Techniques
Constituents Approaches for Treatment
Iron and manganese (Low concentration) Sequestration
Iron and manganese (High concentration) Chlorination or aeration to oxidize metals,
then filtration to remove
Ammonia Chlorination
Pathogenic microorganisms (Coliforms) Chlorination for disinfection
Hardness Precipitation, ion exchange, or
nanofiltration/reverse osmosis (NF/RO)
4.2.1 Sequester Iron and Manganese
A common method of controlling iron and manganese oxidation and subsequent rusty or
black deposits on water fixtures is to add polyphosphates upstream of any other chemical
addition. The phosphate compounds combine with the metal ions, making them unavailable
for reacting with oxygen and chlorine later in the treatment process.
Sequestration is typically recommended as a treatment option for raw water with less than
0.5 mg/L of iron. Ten States Standards, a commonly used engineering resource, state that
sequestration by polyphosphates should not be used when the iron concentration exceeds 1
mg/L. The iron concentration in the water pumped from the proposed production well in DRAFT
November 2020 4-2
Corcoran is expected to have 1.7 mg/L of iron. Therefore, polyphosphate sequestration of
iron and manganese is not a recommended treatment option for Corcoran’s water system.
4.2.2 Filtration
The media-based filtration systems are available to Corcoran include horizontal pressure
filters, gravity filters, and biological filters. Filter media can be granular activated carbon
(GAC), silica sand or greensand. Greensand is sand coated in manganese oxide to enhance
iron and manganese removal. Each system was assumed to have a single-unit treatment
flow rate of 500 gpm and a filter loading rate of 3 gpm/ft2, with the option to add a second
unit for treatment of up to 1,000 gpm at the same 3 gpm/ft2 filter loading rate.
Horizontal Pressure Filter
Pressure filters are horizontal pressure vessels containing the filter media layers, underdrain
and backwash trough inside the vessel (see Figure 4-1). Pressure is applied to the system
by the well pump to push water through the filter media. Chlorine is added upstream of the
pressure filter to oxidize iron and manganese, forming particles that can be filtered out of
the water. In-line aeration is occasionally used to enhance the particle formation. A
horizontal pressure filter vessel can be divided into multiple independent filter cells so that
one or more cells can be depressurized and removed from service while the remaining cells
operate.
Figure 4-1 Horizontal Pressure Filter Section View (courtesy of Tonka Water,
filter media shown is not specific to Corcoran)
Horizontal pressure filters have minor pressure drop across the filter media (less than 10
psi). This allows for a system in which the well pump can be sized to supply additional
pressure to move water through the pressure filters and on ward to elevated storage. The
system eliminates the need for a clear well and a second high service pump system to pump
finished water to the tower. DRAFT
November 2020 4-3
Table 4-2 Pressure Filter Design Information
Footprint (per unit) 8’ diameter X 23’ length
Treatment capacity (per unit) 500 gpm, 3 gpm/ft2 loading rate
Number of units Initial construction: 1
NE quadrant build-out: 2
Expansion beyond NE quadrant: Add’l units can be added in
parallel
Equipment cost, first unit $350,000-$400,000
Equipment cost, additional units $300,000 each
Advantages • No clear well or high service pumps required
• Filter cells within vessel operate independently, allowing
one to backwash while others continue filtration
• Minimal operator supervision required
• Allows for filter media to be upgraded to greensand
(silica sand is less expensive)
Disadvantages • Does not remove hardness
• Filter media and internal equipment are not easily
accessible
Gravity Filter
Gravity filters are not pressurized. Water trickles through the filter bed by gravity instead of
being pushed through the media under pressure. For Corcoran’s water system, the water
would be pumped from the well and aerated to allow formation of iron and manganese
particles before flowing into the gravity filter. Filtered water would be collected in a clear
well and pumped to the distribution system. A packaged gravity filter (Figure 4-2) combines
aeration and gravity filtration into one unit. Gravity filters allow easier access to the filter
media and components than pressure filtration and enable direct observation of the filtration
and backwash process. However, gravity filters require one additional pumping step to lift
the finished water to elevated storage.
Table 4-3 Gravity Filter Information
Footprint (per unit) 8’ wide X 21’ length X 12’-6” height
Treatment capacity (per unit) 500 gpm, 3 gpm/ft2 loading rate
Number of units Initial construction: 1
NE quadrant build-out: 2
Expansion beyond NE quadrant: Add’l units can be added in
parallel
Equipment cost, first unit $375,000-$400,000
Equipment cost, additional units $350,000 each
Advantages • Easy access to filter media and internal filter
components
• Minimal operator supervision required
• Allows for filter media to be upgraded to Greensand
Disadvantages • Does not remove hardness
• Clear well and high service pumps required
• Filter cells within unit operate are hydraulically
connected, and entire unit must be removed from
service during backwash
DRAFT
November 2020 4-4
Figure 4-2 Gravity Filter (courtesy of Tonka Water)
Biological Filter
Biological filtration is a third option for water treatment in Corcoran. The process involves a
series of pressure or gravity filters designed to enhance growth of aerobic bacteria on the
filter media. The bacteria remove ammonia by converting it to nitrite and nitrate. Enhancing
the biological activity in filtration is a relatively new technique for water treatment, and the
water community’s understanding of the process is still developing. It is typically used when
the ammonia concentration in raw water is high enough that maintaining the desired
chlorine residual in the distribution system becomes difficult.
Base on the ammonia concentration in Corcoran’s test well (0.45 mg/L) and the chemical
stoichiometry, additional chlorine demand for Corcoran will be approximately 4.5 to 5.4
mg/L, to maintain a minimum free chlorine residual of 0.2- 0.5 mg/L. Chlorine gas is
currently inexpensive, and increasing chlorine addition will be more economical and have
less complexity than installing, operating, and maintaining a biological treatment module.
Therefore, the biological filter option will not be pursued for Corcoran’s system.
DRAFT
November 2020 4-1
4.2.3 Softening
Hardness in the proposed source water is 326 mg/L as CaCO3. For this hardness level, the
City’s options for in-plant softening are lime softening, ion exchange or nanofiltration
membrane treatment. Discussions below are based on 500 gpm treatment capacity.
Lime Softening
Lime softening is accomplished by adding sufficient lime (Ca(OH)2) to elevate the water pH
above 10.3, at which point calcium hardness will precipitate as CaCO3. Magnesium hardness
can be removed by addition of soda ash (Na2CO3) and elevation of water pH to 11. Iron and
manganese will co-precipitate with the calcium and magnesium compounds. The
precipitated material is collected , dewatered and land applied, when possible, or disposed at
a landfill. The softened water is filtered before additional chemicals are added.
Lime softening requires purchase and storage of lime, large settling basins, recarbonation
(pH adjustment) basin and lime softening residuals collection, dewatering and disposal
systems. Due to the complexity of the treatment process, lime softening is typically used in
facilities that are much larger than Corcoran’s proposed water treatment plant and was not
considered further for Corcoran.
Ion Exchange
Calcium and magnesium compounds can be removed through a centralized ion exchange
process. Similar to a home water softener, calcium and magnesium ions in the raw water
replace sodium ions on an ion exchange media. The calcium and magnesium ions remain
attached to the media until it is recharged with a salt solution.
For Corcoran, softening would be accomplished with three 6-ft diameter ion exchange
vessels. With one vessel out of service, two vessels would treat approximately 347 gpm of
raw water at a loading rate of 6.1 gpm/ft2. The softened water would be combined with 153
gpm of bypass (unsoftened) water to provide 500 gpm of water at a blended hardness of
approximately 100 mg/L of CaCO3. This process does not remove iron or manganese. A
separate oxidation and filtration process would be required upstream of the ion exchange
process.
Table 4-4 Ion Exchange Information
Footprint (per unit) 6’ diameter X 6’ height
Treatment capacity (per unit) 500 gpm (347 gpm raw water + 153 gpm bypass),
6.1 gpm/ft2 loading rate
Number of 3-vessel systems: Initial construction: 1
NE quadrant build-out: 2
Expansion beyond NE quadrant: Add’l units can be added in
parallel
Equipment cost, initial installation $450,000-$500,000
Additional equipment cost, for full
build-out
$450,000-$500,000 per 3-vessel system
Advantages • Generates less sludge volume than lime softening
• Modular system can be added downstream of an iron
and manganese removal filter system
Disadvantages • Does not effectively remove iron or manganese, and
pre-treatment for these constituents is needed
• Produces a high-chloride waste stream
• Larger footprint than membrane system DRAFT
November 2020 4-2
Nanofiltration Membrane
Membrane filtration can be used to remove hardness compounds. Nanofiltration (NF)
membranes have a pore size of 0.1 - 10 nm and allow some single-valent ions (like
chloride) to pass through. A membrane system for Corcoran would consist of one 8-ft X 4-ft
array membrane skid. Iron and manganese can cause membrane fouling, so a granular
media filter, like the pressure filters described previously, should be installed upstream of
the NF membranes. A portion of the NF membrane influent is used to carry away the
material that cannot pass through the filter. Assuming 75% of the NF membrane influent
passes through the membrane to become softened water, 380 gpm of membrane influent is
needed to produce 285 gpm of cleaned, softened water (permeate). The permeate will be
combined with 120 gpm of unsoftened (bypass) water to produce 405 gpm of clean,
blended water with approximately 100 mg/L hardness as CaCO3. The membrane system will
require a separate clean-in-place system and several chemical systems to maintain the
membranes.
Table 4-5 Nanofiltration Information
Footprint (per skid) 8’ wide X 4’ length X 6’ height
Treatment capacity (per skid) 500 gpm input, 405 gpm output (285 permeate + 120 gpm
bypass)
Number of skids Initial construction: 1
NE quadrant build-out: 2
Expansion beyond NE quadrant: Add’l skids can be added in
parallel
Equipment cost, initial installation $450,000 - $500,000
Additional equipment cost, for full
build-out
$450,000 - $500,000 each skid
Advantages • Membrane waste does not contain high chloride
concentrations
• Modular system can be added downstream of an iron
and manganese removal filter system
• Smaller footprint than the ion exchange softening
system
Disadvantages • Iron and manganese need to be removed prior to
membrane filtration to prevent fouling
• A separate clean-in-place skid and chemical feed
systems for sodium bisulfite, anti-scalant and pH
adjustment are required
• Generates 6 times more wastewater than ion exchange
(however, it does not contain the high chlorides).
4.2.3.1 Softening Conclusion
The water softening options tend to be much more complex than the media -based filter
options. They also cost more than the filter options and will involve more in -depth
maintenance programs. For ion exchange and nanofiltration, pretreatment for iron and
manganese is required, essentially creating the need to run two complete water treatment
systems in a single plant. Water customers who want softened water can opt to install an
in-home water softener. For these reasons, in-plant water softening is not recommended for
Corcoran at this time.
DRAFT
November 2020 4-3
4.2.4 Treatment Recommendation
The treatment objectives of the proposed Corcoran Water Treatment Plant are:
• Consistent production of drinking water that meets all EPA National Drinking Water
Standards with good taste and aesthetics
• Simple operation
• Expandable
• Economical
The pressure and gravity filter options are typical for city water treatment systems, simple
to operate, expandable and economical. The pressure filters offer the advantage of being
able to backwash one filter cell while filtration continues in the other cell. The pressure filter
system does not require an additional pumping step to move the finished water to the
distribution system. This provides a small cost savings at initial construction and lower
power and maintenance costs over time. For these reasons , the recommended filter for the
treatment process is the horizontal pressure filter.
A complete water treatment process with horizontal pressure filters will include pre-
chlorination upstream of the filters, filtration, fluoride addition and chlorine disinfection. A
backwash water recovery basin can be added to return most of the backwash water to the
head of the plant rather than wasting all of it to the sanitary sewer. Chlorine and fluoride
systems will be installed within individual chemical rooms. An electrical equipment room and
restroom will also be included. Figure 4-3 illustrates the conceptual layout the Corcoran
water treatment plant.
DRAFT
FUTURE PRESSURE FILTERPRESSURE FILTER 1FUTURE FILTERFUTURE FILTEROH DOOROFFICE/LABCHLORINEROOMFLUORIDEROOMREST ROOMSINK ANDEYEWASHAIRBACKWASHBLOWERWELL WATERIN500 GPM EACHTREATEDWATER OUTFUTURE BUILDING EXPANSIONELECTRICAL ROOMMECHANICALROOMBACKWASH WATER
RECOVERY BASIN
(18,000 GAL. BURIED)PHOSPHATETANKM:\2294\0048 - NE Water Supply\3_DESIGN\CAD\2 EXHIBITS\figure 1 Water Supply Schematic.dwg
SHEET NO.:SHEET TITLE:10/5/2020 8:34:17 AM
CLIENT:CITY OFCORCORANCITY OF CORCORAN
NORTHEAST WATER SUPPLY
8200 COUNTY ROAD 116
CORCORAN, MN 55340 8200 COUNTY ROAD 116CORCORAN , MN 55340DWN BY:ISSUE DATE:PROJECT NO.:2294-0048ISSUE NO.:JVBCHK'D BY:JMBAPP'D BY:JMBCERTIFICATION:08/12/20201FIGURE 2EXAMPLE FILTRATIONPLANT FLOOR PLANFIGURE 4-3DRAFT
November 2020 4-4
The proposed plant layout is based on 1,000 gpm treatment capacity, with space to expand
the plant to the east to add additional vessels. The proposed site plan for the water
treatment plant, test well and production well is shown in Figure 4-4.
DRAFT
97.5' TO POND322' TO CENTERLINE OF CSAH 116150.9' TO FUTURE 30" SANITARY PIPECONCRETE BOLLARD(TYP.)920920
920925
930
918919921921
9
2
1
922
922 9
2
2
923923
923
924924
924
926
927
928
929931932
45' TO RAW WATERMAINRAW WATER TO FUTURE WELLSFUTURE STORMWATERPOND AREAWETWE
T
WETWET
WET
WETWETWETWETWETWET
WET
W
E
TWET WETWET
WET
WETWE
T WETWETWETWETWETPROPOSED PRODUCTION WELLE:459146.34'N:226354.86'EL. 925.00T119N-R23W-S12-NW14-NW14-NW14FIELDENTRANCEACCESS POINTFUTURE 30" TRUNK SEWERFUTURE 8" SEWER FOR WATER TREATMENT PLANTFUTURE WATERMAIN (TREATED)FUTURE RAW WATERMAINEXISTING OBSERVATION WELL(TEST WELL)FOR ALL TEST PUMPING ROUTETEMPORARY DISCHARGE PUMPING FROMWELL TO ENGINEER-SPECIFIEDDISCHARGE LOCATION IN THIS VICINITYAPPROXIMATELOCATION OFSEPTIC TANKS ANDDRAIN FIELD.FUTURE WATER TREATMENTPLANT EXPANSION (50'X30')BURIED BACKWASH WATER RECOVERY TANK (18,000 GAL)TANK DIMENSIONS 12' DIA. X 30'PROPOSED WATER TREATMENT PLANT(50'X50')FUTURE HENNEPIN COUNTY ROW TAKE (TOTAL 60' HALF ROW)PROPOSED DRIVEWAY ACCESS AND PARKING LOTSETBACK LINEGARAGE ACCESSM:\2294\0048 - Ne Water Supply\3_DESIGN\CAD\3 PLANSHEETS\C-101.dwg
SHEET NO.:SHEET TITLE:10/13/2020 8:54:16 AM
CLIENT:CITY OFCORCORANCITY OF CORCORAN
NORTHEAST WATER SUPPLY
8200 COUNTY ROAD 116
CORCORAN, MN 55340 8200 COUNTY ROAD 116CORCORAN , MN 55340DWN BY:ISSUE DATE:PROJECT NO.:2294-0048ISSUE NO.:JVBCHK'D BY:JMBAPP'D BY:JMBCERTIFICATION:08/12/20201C-102SITE IMPROVEMENTSPLANWARNING:THE CONTRACTOR SHALL BE RESPONSIBLE FOR CALLING FOR LOCATIONS OF ALL EXISTING UTILITIES. THEY SHALLCOOPERATE WITH ALL UTILITY COMPANIES IN MAINTAINING THEIR SERVICE AND/OR RELOCATION OF LINES.THE CONTRACTOR SHALL CONTACT GOPHER STATE ONE CALL AT 651-454-0002 AT LEAST 48 HOURS IN ADVANCE FORTHE LOCATIONS OF ALL UNDERGROUND WIRES, CABLES, CONDUITS, PIPES, MANHOLES, VALVES OR OTHER BURIEDSTRUCTURES BEFORE DIGGING. THE CONTRACTOR SHALL REPAIR OR REPLACE THE ABOVE WHEN DAMAGED DURINGCONSTRUCTION AT NO COST TO THE OWNER.GOPHER STATE ONE CALLTWIN CITY AREA: 651-454-0002TOLL FREE 1-800-252-1166CALL BEFORE YOU DIGEXISTING CONTOURFUTURE CITY PROPERTY (PURCHASE IN PROGRESS)PROPERTY LINESITE LEGENDHORIZONTAL/VERTICAL CONTROL NOTES1. THE HORIZONTAL CONTROL FOR THIS PLAN IS NAD83(2011) HENNEPIN COUNTYCOORDINATES SYSTEM US FOOT2. THE VERTICAL CONTROL FOR THIS PLAN IS NAVD88FIGURE 4-4DRAFT
November 2020 4-5
4.3 CONCEPTUAL TREATMENT COST
For water treatment plant construction, it is recommended that the City budget $2,700,000.
Engineering, legal and administrative costs are estimated to be $400,000, or roughly 15%
of the construction cost. For operation and maintenance activities, it is recommended to
budget $200,000 per year for the initial treatment capacity. Annual O&M cost is subject to
future treatment capacity expansion. The detailed conceptual cost estimate is presented in
Section 6.2.
4.4 SCHEDULE
The water treatment plant would be operational in 2022/2023 based on January 2021
design start. The design and permitting period for a water treatment plant of this size
typically lasts about 1 year, followed by another year for construction and startup activities.
DRAFT
November 2020 5-6
5.0 WATER STORAGE
As documented in the NE Water Supply FS Update (July 2019), the minimum water storage
volume for the NE Quadrant system is 650,000 gallons, which is based on fire flow
requirements when municipal demand is low, such as in Corcoran. Because 650,000 gallon
is not a standard water tower size, the recommended standard size of the elevated water
tower is 750,000 gallons to provide additional storage volume. The tower will be constructed
on higher ground of the NE service area to minimize vertical construction cost and to ensure
all connections are served from the tower without the need for booster pumps. This section
discussed site alternatives and tower configuration options.
5.1 WATER TOWER SITE ALTERNATIVES
Two general locations have been discussed as potentially favorable for construction of a
water tower. Selection of the two water tower locations was based on topography and
reasonable proximity to the proposed water treatment plant location. The two potential
locations and proposed trunk systems are shown on Figure 5-1.
DRAFT
#*!O
4567116
4567116
456730 45673097th Ave N
Country Rd
HuntersRdgCR-116StiegRd
City of CorcoranCity of Maple GroveCity of Corcoran
City of Rogers
12''16''12''12'
'
1
2
'
'16''
Path: L:\2294\19-048\Pro\WaterSupplyArea\WaterSupplyArea.aprx
6/23/2020 3:56 PM shujc0243 Layout: Corcoran NE Water Supply Area
Figure 1
JUN 2020
Corcoran NE Water Supply Area
CITY OF CORCORAN
¯1,200 0 1,200600
Feet
Legend
Municipal Boundary
Parcel Boundaries
Bellweather Parcels
Existing Watermain
Preferred Water Tower
Locations
!O Potential Water Tower
Locations
Well/Water Treatment
Plant
#*Potential Supply
Connections with
Neighboring Comm
Wetland Delineation
NWI WetlandsDRAFT
#*!O
4567116
4567116
456730 45673097th Ave N
Country Rd
HuntersRdgCR-116StiegRd
City of CorcoranCity of Maple GroveCity of Corcoran
City of Rogers
12''16''12''12'
'
1
2
'
'16''
Path: L:\2294\19-048\Pro\WaterSupplyArea\WaterSupplyArea.aprx
6/23/2020 3:56 PM shujc0243 Layout: Corcoran NE Water Supply Area
Figure 1
JUN 2020
Corcoran NE Water Supply Area
CITY OF CORCORAN
¯1,200 0 1,200600
Feet
Legend
Municipal Boundary
Parcel Boundaries
Bellweather Parcels
Existing Watermain
Preferred Water Tower
Locations
!O Potential Water Tower
Locations
Well/Water Treatment
Plant
#*Potential Supply
Connections with
Neighboring Comm
Wetland Delineation
NWI WetlandsDRAFT
November 2020 5-7
Location 1 (Oswald) is southeast of the WTP (CR 116) and Location 2 (City Park) is east of
the WTP. Location 2, being park land, will be City-owned. Location 1 (Oswald), which is not
currently under development, will require land acquisition. Table 5-1 summarizes
comparisons of the two sites.
Table 5-1 Details of Proposed Water Tower Locations
Base of
Tower
Elev.
HWL of
Water
Tower
System
Pressure
Approximate
Watermain
Extension* Considerations
ft. ft. psi ft.
Location 1
(Oswald) 950 160 69 3,800
Land must be
purchased for this
location
Location 2
(City Park) 940 170 74 3,000
Location requires
upsizing a watermain
in Bellwether, as
shown in Figure 5-1
Lower site elevation
requires a 10-foot
taller tower
*Proposed trunk watermain from WTP to water tower
The soil conditions at the proposed water tower locations are not currently known.
Geotechnical borings should be completed at each location before the preferred site is
selected. Geotechnical analysis can verify whether any extensive site improvements are
needed to support the tower.
5.2 WATER TOWER CONFIGURATION OPTIONS
Water tower configurations for a 750,000-gallon water tower include composite, single
pedestal, and multi-column configurations. A multi-column tower is not recommended for
Corcoran because:
• Multi-column towers are often recommended when good
seismic performance is needed, but Minnesota is not
recognized seismic zone.
• Cost, material, and labor for reconditioning of multi-column
tower is high compared to other tower configurations.
• Aesthetically, multi-column towers appear less modern;
Corcoran’s tower will be near new housing developments.
It is recommended that the City consider a com posite or a single
pedestal tower configuration. The features of the two configurations
are:
Composite
• Concrete pedestal, steel bowl (see Figure 5-2)
• Strong support for water tower higher than 150 ft
• Storage area at bottom of tower
• Dripping ring around bowl to prevent mold on lower portion of
bowl
Figure 5-2 Composite
Water Tower (courtesy
of KLM Engineering)
DRAFT
November 2020 5-8
• Minor maintenance to concrete
• Higher cost on construction
Single pedestal
• Steel pedestal and bowl (see Figure 5-3)
• Smooth transition and symmetrical
• Smaller footprint at tower bottom
• Prone to condensation and mold growth on bottom half
• Cost for reconditioning is typically more than composite because
all interior needs coating
5.3 CONCEPTUAL COST
For tower construction, it is recommended that the City budget
$2,500,000 to $3,000,000. The construction cost will vary with different
tower configurations, additional site-specific items and costs associated
with watermain extension. Major maintenance includes tower cleaning
and repainting, expected to occur every 15 years at a cost of
approximately $300,000 for a full recondition. A conceptual construction
cost estimate is presented in Section 6.0.
5.4 SCHEDULE
For a 750,000-gallon water tower, a six-month to nine-month period for design and
approximately 1-year construction period should be anticipated. In order to coordinate
startup of the water treatment plant and with completion of the water tower. Section 6.4
discusses a preliminary schedule.
Figure 5-3 Single
Pedestal Water Tower
(courtesy of KLM
Engineering) DRAFT
6.0 CONCEPTUAL COSTS & SCHEDULE
6.1 CONSTRUCTION COST ESTIMATES FOR MUNICIPAL PRODUCTION WELL
Description Cost
Construction* $ 275,000-$300,000
Contingency (15% of Construction) $ 41,250-$45,000
Total Construction Cost $ 320,000-$350,000
*Includes mobilization, contractor overhead, site work, utilities,
well drilling, development, testing and logging
Detailed cost estimate is attached as Attachment D.
6.2 COST ESTIMATES FOR WATER TREATMENT PLANT USING HORIZONTAL
PRESSURE FILTER
Description Cost
Construction* $ 2,300,000
Contingency (15% of construction) $ 350,000
Total Construction Cost $ 2,700,000
Total Annual OM&R** $ 200,000
*Includes mobilization, contractor overhead, site work, utilities,
architectural, structural, process, mechanical, electrical and
controls. Engineering, legal and admin fees will add $400,000 to
the total cost.
**The budget is for the initial treatment capacity. Annual O&M
cost is subject to future treatment capacity expansion.
Detailed cost estimate is attached as Attachment E.
6.3 CONSTRUCTION COST ESTIMATES FOR WATERMAIN EXTENSION FROM WTP
TO WATER TOWER SITE
Description Location 1
(Oswald)
Location 2
(City Park)
Watermain Extension in undeveloped area-16” $ 690,000 $ 520,000
Watermain Extension in undeveloped area-12” - $ 23,000
Upsizing Watermain in New Development-8” to 16” - $ 51,000 DRAFT
Description Location 1
(Oswald)
Location 2
(City Park)
Contingency $ 110,100 $ 89,000
Total $ 800,000 $ 700,000
*Land and easement acquisition cost will be added to the cost analysis when the information is
available
Detailed cost estimate is attached as Attachment F.
6.4 CONSTRUCTION COST ESTIMATES FOR WATER TOWER
160’ Tower (Location 1, Oswald) 170’ Tower (Location 2, City Park)
Description Low Estimate High Estimate Low Estimate High Estimate
Construction* $2,600,000 $3,000,000 $2,800,000 $3,000,000
*Includes site work, site utilities, foundation improvement, control and electrical improvement, and
contingency (15% of construction).
**Land and easement acquisition cost will be added to the cost analysis when the information is
available
Detailed cost estimate is attached as Attachment G.
6.5 BUDGET RECOMMENDATION
It is recommended that the City budget $ 7,500,000 to $8,000,000 for the NE Quadrant
water supply and distribution system construction and engineering, legal and administrative
fees. The construction budget on the high-end breakdown is shown below.
Municipal Well $350,000
Water Treatment Plant $2,700,000
Watermain Extension from WTP to Tower $800,000
Water Tower $3,000,000
*Engineering, Legal, and Admin $1,100,000
Total $7,950,000
*15% of total capital cost
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6.6 SCHEDULE FOR CRITICAL DECISIONS
The following schedule was developed to help the City to identify the major components of
the project and critical decision-making milestones.DRAFT
NORTHEAST WATER SUPPLYRevised on: 11/09/20202020212022ItemJanFebMarAprMayJunJulAugSepOctNovDecJanFebMarAprMayJunJulAugSepOctNovDecJanFeb1. Lother Property Acquisition (for Well & WTP)a. Contingent Purchaseb. Due Diligence Periodc. Finalize Property Purchase2. Test Wella. Obtain Quotesc. NTP & Mobilizationd. Drill & Develop Welle. Well Testing Activitiesf. Coordination w/DNR re: Pump Testing Muni Well3. Municipal Well #1a. Prepare Plans & Specificationsb. Submit Plans & Prelim WHPA to MDHc. MDH Review Period & Site Visitd. Comment Responses & Final MDH Approvale. Council Authorize Biddingf. Bidding Periodg. Council Awardh. Sign Contract, NTP & Mobilizationi. Drill & Develop Wellj. Well Testing Activitiesk. DNR Water Appropriation Permit4. Feasibility Study for WTP & Towera. Council Authorize Studyb. Geotechnical Study for WTP and tower sitesc. Discuss emergency connection w/ Maple Groved. Prepare Draft Reporte. City Review & Discussionsf. Finalize report g. City Council approve FS and initiate design phase5. Revision of Existing Plans (for water supply changes)a. DNR Water Supply Plan Revisionsb. MCES 2040 Comprehensive Plan Amendment6. Property Acquisition - Tower & Water Mainsa. Preliminary Discussionsb. Negotiation on Recommended Parcelsc. Finalize Property Purchases7. Design Period including Plans & Specifications(1 set for WTP & water mains; 1 set for tower)a. Basis of Design Report (incl. site survey & geotech)b. 50% Designc. 90% Designd. MDH Plan Reviews for All Elementse. Other Permit Approval Applications (1)f. Finalize Plans & Specificationsg. Bidding Periodh. Council Awardb. Council Award, contingent on MDH approval of municipal well locationDRAFT
NORTHEAST WATER SUPPLYRevised on: 10/30/2020222023ItemJanFebMarAprMayJunJulAugSepOctNovDecJanFebMarAprMayJunJulAugSepOctNovDec8. Construction - WTP, Tower, & Water Mainsa. Sign Contract, NTP & Mobilizationb. Constructionc. Start-Up9. Wellhead Protection Plan (MDH)a. Start of 4-Year Process10. Sanitary Sewer Extension (30")(Details TBD - Need to be in service by WTP start-up)11. Preliminary work for Well #2(Planning should begin in 2021)Notes(1) Permit applications include: wetlands, Department of Labor and Industry, building, county/utility ROW and MnDOT/FAA for towerDRAFT
Toll Free: 800-472-2232 Email: wenckmp@wenck.com Web: wenck.com
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