HomeMy WebLinkAbout2016-025 Council ResolutionCITY OF LINO LAKES
RESOLUTION NO. 16-25
RESOLUTION ACCEPTING FEASIBILITY REPORT FOR THE MATTAMY HOMES
WATER REUSE
WHEREAS, pursuant to Resolution 15-53, Authorizing the Feasibility Study for Mattamy
Homes Water Reuse adopted by the council on June 8, 2015, a report has been prepared by WSB
and Associates, and
WHEREAS, this report was received by the council on April 4, 2016, and
WHEREAS, the report provides information regarding whether the proposed project is
necessary, cost effective, and feasible.
NOW, THEREFORE BE IT RESOLVED by The City Council of The City of Lino Lakes:
1. The council hereby accepts the feasibility report, prepared by WSB and Associates dated
June 8, 2015.
2. The council will consider such improvements in accordance with the report and the
assessment of abutting property for a portion of the cost of the improvement pursuant to
Minnesota Statutes, Chapter 429.
3. A public hearing shall be held on such proposed improvement at a date to be determined and
the clerk shall give mailed and published notice of such hearing and improvement as required
by law.
Adopted by the Council of the City of Lino Lakes this 11th day of April, 2016.
The motion for the adoption of the foregoing resolution was introduced by Council Member
Kusterman and was duly seconded by Council Member Manthey and upon
vote being taken thereon, the following voted in favor thereof:
Kusterman, Manthey, Maher, Rafferty, Reinert
The following voted against same:
none
ATTEST:
Julianne Bartell, Cit Clerk
CITY COUNCIL
AGENDA ITEM 6F
STAFF ORIGINATOR: Diane Hankee, City Engineer
MEETING DATE: April 11, 2016
TOPIC: Consideration of Resolution No. 16-25 Accepting Feasibility
Report for Mattamy Water Reuse
VOTE REQUIRED: Simple Majority
INTRODUCTION
The City Council is to consider accepting Feasibility Report for Mattamy Water Reuse project.
BACKGROUND
The City Council approved Resolution 15-53 on June 8, 2015 authorizing the Feasibility Study
for the Mattamy Water Reuse. The feasibility study has been completed and was approved by
City's Environmental Board on March 30, 2016.
The feasibility Study provides an overview of three options for stormwater reuse in the proposed
Mattamy development:
1. Reusing stormwater to irrigate public places;
2. Reusing stormwater to irrigate public places and the townhomes; and
3. Reusing stormwater to irrigate the entire development.
A water balance was conducted to determine if there was sufficient water quantity available for
each of the three options. The balance evaluated runoff, precipitation, evaporation, and
irrigation. The proposed stormwater pond will receive enough runoff to implement Options 1 or
2, but a potable water connection will be required to implement Option 3. The developer has
reservations regarding option 3 based on their past experience.
In addition, the cost of each of the three options was estimated. After considering water supply
and cost, WSB recommended that the City implement Option 2: reusing stormwater to irrigate
public places and the townhomes for an estimated cost of $463,000. Financing was delineated
for the recommended option, as well as ownership and maintenance recommendations. It is
recommended that development fees cover $197,000 of the total cost, with the remaining funded
by the City's Trunk Water fund.
Requested Council Direction
Staff recommends Resolution No. 16-25 Accepting Feasibility Report for Mattamy Water Reuse.
Attachments
1. Resolution No. 16-25
2. Mattamy Homes Water Reuse Feasibility Report
2
City of Lino Lakes, MN
600 Town Center Parkway • Lino Lakes, MN 55014
•
talswolualwaast
FEASIBILITY
Report
June 8, 2015
Mattamy Homes
Water Reuse
City of Lino Lakes
Anoka County, MN
WSB Protect No. 2988-01
477 Temperance Street
WSB� St. Paul, MN 55101
Tel (651) 2-8450 Fax (651) 286-8488
&Awodates, Inc. wsbeng.com
FEASIBILITY REPORT
MATTAMY HOMES WATER REUSE
FOR THE
CITY OF LINO LAKES, MINNESOTA
June 8, 2015
Prepared By:
WSB & Associates, Inc.
477 Temperance Street
St. Paul, MN 55101
651-286-8450
651-286-8488 (Fax)
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
CERTIFICATION
I hereby certify that this plan, specification, or report was prepared
by me or under my direct supervision and that I am a duly
Licensed Professional Engineer under the laws of the State of
Minnesota.
27.'°-;2ed,7'a-
Greg F. Johnson, PE
Date: April 11, 2016 Lic. No. 26430
Prepared By:
Erin J. Heydinger
Date: April 11, 2016
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
TABLE OF CONTENTS
1. EXECUTIVE SUMMARY 4
2. MATTAMY HOMES WATER REUSE 5
2.1 INTRODUCTION 5
2.2 GENERAL BACKGROUND 5
23 PROPOSED IMPROVEMENTS 6
3. FINANCING 8
3.1 OPINION OF COST 8
3.2 FUNDING 8
4. RECOMMENDATION 10
Appendix A
Figure 1 — Project Location
Figure 2 — Option 1: Irrigating Public Spaces
Figure 3 — Option 2: Irrigating Public Spaces and Townhomes
Figure 4 — Option 3: Irrigating Entire Development
Appendix B
Table 1 — Estimated Annual Irrigation
Appendix C
Table 1 - Water Balance Summary
Table 2 — Option 1 Cost Summary
Table 3 — Option 2 Cost Summary
Table 4 — Option 3 Cost Summary
Appendix D
Water Balance Tech Memo
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
1. EXECUTIVE SUMMARY
The proposed Mattamy Homes Development is a 400 acre residential development located east
of Interstate 35E and north of Main Street in the City of Lino Lakes. Surface water management
for the project would include storm water quality, storage and rate control. The storm water
storage area will hold a significant amount of water that can be used to provide irrigation verses
conventional groundwater use for irrigation.
Over the past three years, management of both surface water and groundwater resources have
received increased awareness both locally and regionally. Lino Lakes is included in the North
and East Metro Groundwater Management District established by the Department of Natural
Resources (DNR). The goal is to protect of water resources through sustainable water use
solutions such as the one being proposed.
The water reuse project was evaluated through a water balance analysis and multiple options for
an irrigation reuse system. The options for an irrigation reuse system are:
1. Irrigate the park and public spaces
2. Irrigate the townhomes, park, and public spaces
3. Irrigate the entire development, including single-family residences
The options were evaluated based on the estimated costs, ownership, storm water requirements,
and maintenance. Option 2 is recommended: it includes irrigation of the townhomes, park and
public spaces.
The estimated project cost for Option 2 is $463,000 which includes 10% construction
contingency and 20% indirect costs. Funding for the project is proposed through development
fees generated from surface water management fees, and City trunk water system funds.
This project is feasible and cost-effective from an engineering standpoint, and should be
constructed as proposed herein.
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
2. MATTAMY HOMES WATER REUSE
2.1 INTRODUCTION
2.1.1 Authorization
On June 8, 2015, the City of Lino Lakes City Council authorized the preparation of a
feasibility report for the Mattamy Homes Water Reuse project.
2.1.2 Scope
The Mattamy Homes Development includes a large storm water storage area that can be
used as an irrigation source. The proposed project includes storm water used for
irrigating the development. This report evaluates several options for water reuse and
considers water resources, cost, regulatory requirements, and value of the reuse irrigation
system.
2.1.3 Data Available
Information and materials used in the preparation of this report include the following:
• City of Lino Lakes Comprehensive Plan
• City of Lino Lakes Base Map and/or Topography Maps
• Minnesota Department of Natural Resources Water Usage Reports
• Grading plans and plat for the Mattamy Homes development
2.2 GENERAL BACKGROUND
2.2.1 Project Location
The Mattamy Homes Development is located in the City of Lino Lakes, west of Interstate
35E, east of 20th Avenue North, north of Main Street, and south of the bounds extended
by 77th Street East. A map showing the project area can be found in Figure 1, Appendix
A of this report.
2.2.2 Existing Conditions
The existing land use at Mattamy Homes is agricultural, with stormwater currently
running through the site via Anoka County Ditch 55 (ACD -55) and Anoka County Ditch
72 (ACD -72). These ditch systems receive storm water runoff from watersheds located in
the cities of Hugo and Lino Lakes and discharge to Peltier Lake. A study is being
completed to address the surface water in the NE area or Lino Lakes. This report
assumes that ditch water is not available as a source for irrigation and will be addressed
through the NE Drainage Study.
2.2.3 Stormwater Management
The Rice Creek Watershed District (RCWD) Rules state that stormwater volume and rate
control must occur in any location with new or reconstructed impervious surfaces, such
as the Mattamy development. Stormwater infiltration is the preferred method of volume
control. Prior to this feasibility study, an analysis was conducted to determine if the site
was suitable for infiltration. Because a large portion of the site is within a vulnerable
portion of the Drinking Water Supply Management Area (DWSMA), and the Minnesota
Department of Health recommends that infiltration not occur in a vulnerable DWSMA, it
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
was determined that infiltration is not feasible. In this instance, the RCWD Rules state
that stormwater irrigation can occur in lieu of infiltration as a volume reduction practice.
The three scenarios in this study reflect this determination.
2.2.3 Current Irrigation Practices
The City currently regulates irrigation within the community to promote water
conservation. It is estimated that irrigation accounts for 43% of the potable water used in
the City each year (Appendix B, Table 1). The large proportion of water allocated
towards irrigation presents an opportunity for the City to reduce its summer demand on
the potable water system through water reuse.
2.3 PROPOSED IMPROVEMENTS
There were three options identified to coincide with the Mattamy development
Option 1: Irrigating Public Spaces with Storm Water
Option 1 includes a water reuse irrigation system for public open spaces within
the Mattamy Homes Development. This system includes the park in the center of
the development as well as the berm on the east side of the development. In total,
the irrigated area for Option 1 is 11 acres. A figure depicting Option 1 is shown as
Appendix A, Figure 2.
Option 2: Irrigating Public Spaces and Townhomes with Storm Water
Option 2 includes a water reuse irrigation system for public open spaces and
multi -family residential (townhome) area in the southeastern portion of the
development. The townhome area includes 12 acres of green space that will
require irrigation, in addition to the 11 acres irrigated in the public space. A figure
depicting Option 2 is shown as Appendix A, Figure 3.
Option 3: Irrigating all of the Mattamy Development with Storm Water
Option 3 includes a water reuse irrigation system for public open spaces, multi-
family residential townhomes, and single-family residences. A fourth municipal
utility would be installed throughout the development. The third option requires
homeowner education and interaction for system management and coordinatation
with City maintenance staff. The total irrigated area for Option 3 is 144 acres. A
figure depicting Option 3 is shown as Appendix A, Figure 4.
A water balance analysis was completed and can be found in Appendix D. The water
balance summary for each option:
Option 1: Irrigating Public Spaces with Storm Water
The water balance model indicates that the storm water stored can sufficiently
supply water for irrigation of the public spaces with minimal pond level
fluctuations.
Feasibility Report
Mattamy Moines Water Reuse
WSB Project No. 2988-01
Option 2: Irrigating Public Spaces and Townhomes with Storm Water
The water balance model indicates that the storm water stored can sufficiently
supply water for irrigation of the public spaces and townhomes with minimal
pond level fluctuations.
Option 3: Irrigating all of the Mattamy Development with Storm Water
The water balance model indicates that the storage area cannot supply enough
irrigation water to support this option. The model showed that storage levels will
reach significantly low levels and that the reuse system would require
supplementation from the municipal water system. The cost to supplement the
water reuse system with the municipal supply is not a cost that required with
Option 1 or 2. In addition there will be vegetation issues if the storage area is
drawn down this low, along with it is anticipated that residents will not desire to
have the storage area this low.
Option 2 is recommended because it provides the most surface water reuse without a
fourth municipal utility system and individual service lines. Option 2 can be
implemented without supplementation/connection to the municipal water system.
2.3.1 Pump and Pipe Materials
Appendix C includes pump and forcemain layouts for each option, as well as suggested
meter locations. The pump size should be determined by the irrigation designer, and they
should be controlled by soil -moisture sensors, to ensure that watering is dictated by
weather and soil conditions. The proposed forcemain is 2 to 4" diameter, high density
polyethylene (HDPE).
2.3.2 Water Quality
Prior to each irrigation season, it is recommended that the storage area be tested for water
quality. The Minnesota Pollution Control Agency has recommended water quality
parameters as outlined in Appendix D. If the parameters are not met, additional
treatment should be considered to ensure the storage water remains of high enough
quality to use for irrigation.
2.3.3 Ownership Recommendation
It is recommended that the City own and operate the system, and within the townhome
area, the City should have a maintenance agreement with the HOA where they are
responsible for maintaining the system in the townhome area.
23.4 Metering, Usage, and Billing
It is recommended that the park and berm irrigation systems be operated with
independent meters so that the townhome maybe invoiced for their water usage to
support maintenance of the system. Watering restrictions should remain in place for
consistency and promote water conservation.
2.3.5 Permitting
A Rice Creek Watershed District (RCWD) permit will be required. The project will meet
volume reduction, treatment and rate control per RCWD rules. A Minnesota Department
of Natural Resources (DNR) appropriations permit will also be required for the project.
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
2.3.6 Right of Way
The proposed reuse system with Option 2 would be constructed within public right of
ways and public land or land owned by the Home Owner Association for the townhomes.
Option 3 may require additional easement or right of way dedicated through platting for
the distribution system.
3. FINANCING
3.1 OPINION OF COST
The detailed opinion of probably cost for each of the three options can be found in Appendix C
of this report. The opinions of cost incorporate estimated construction costs and include a 10%
construction contingency and 20% for indirect costs (legal, administrative, engineering, and
financing items).
Table 4 below provides a summary of the estimated cost for each of the three options
considered:
Option
Construction with
Contingency
Indirect
(20%)
Total
Option 1: Public Areas
Irrigated
$296,000
$60,000
$356,000
Option 2: Public Areas and
Townhomes Irrigated
$386,000
$77,000
$463,000
Option 3: Public Areas,
Townhomes, and Single-
$2,151,000
$431,000
$2,582,000
Family Homes Irrigated
3.2 FUNDING
Funding for the project is proposed through development fees generated from surface water
management fees, and City trunk water system funds. The proposed funding for Option 2 is
outlined as follows:
Funding Source
Amount
Surface Water Management
$197,000
Trunk Water
$266,000
Total
$463,000
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
The trunk fee is calculated based on 40% of the $4,069 trunk water fee for each townhome unit,
based on the estimated water savings. It was assumed that each townhome is one Residential
Equivalency Unit (REU).
The project may be eligible for grants from the Metropolitan Council of Environmental Services
for Targeted Storm Water. Grant funding opportunities will be evaluated during the design of
the project.
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
4. RECOMMENDATION
The project is feasible, necessary, and cost-effective from an engineering perspective. WSB &
Associates, Inc. recommends construction of the proposed improvements as detailed in this
report. The economic feasibility of this project will be determined by the City Council.
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
APPENDIX A
Figure 1: Project Location
Figure 2: Option 1: Irrigating Public Spaces
Figure 3: Option 2: Irrigating Public Spaces and Townhomes
Figure 4: Option 3: Irrigating Entire Development
Feasibility Report
Matta,ny Homes Water Reuse
WSB Project No. 2988-01
Project Area
Single Family Homes
Townhomes
Irrigation Source
Ponds
Park
Berm
ROW
Figure 1
Mattamy Homes Project Area
WSB
& Associates, Inc.
Document Path: K: \ 02988-010 \ GIS \M aos \Ficturel MatarnyHomeProlectArea.rnxd
Rehbein St
• .—
• •
fr-
7'1
73rd St
Irrigated Area
• Pump
Park Irrigation System
Berm Irrigation System
Project Area
Single Family Homes
Townhomes
Irrigation Source
Ponds
Park
Berm
~Y.
1,000
Feet
TI
ROW
C 1 T Y 0
[NOLA KES
Figure 2
Option 1 - Parks and Berm
WSB
& Associates, In, .
1.0-886Z01 )1 Med I,
N
Rehbein St
VA
Irrigated Area
■ Pump
Park Irrigation System
Berm Irrigation System
Townhome Irrigation System
Project Area
Single Family Homes
Townhomes
Irrigation Source
73rd St
-'{ IL I I I IH111
111111
111111
0 1,000
Feet
Ponds
Park
Berm
ROW
Figure 3
Option 2 - Parks, Berm, and Townhomes
Ak
WSB
& Associates, Inc.
Single Family Irrigation System
Figure 4
Option 3 - Entire Development Irrigated
APPENDIX B
Table 1 - Estimated Annual Irrigation
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
Pumping Data
Average Monthly Winter Use:
2011 2012 2013 2014 Average
January
February
March
April
May
June
July
August
September
October
November
December
25,888,000
25,071,000
27,807,000
25,983,000
26,187,250
23,596,000
22,437,000
23,407,000
22,194,000
22,908,500
23,542,000
24,787,000
23,681,000
24,295,000
24,076,250
26,549,000
35,803,000
27,568,000
25,505,000
28,856,250
32,688,000
48,084,000
35,966,000
36,576,000
38,328,500
61,591,000
66,619,000
38,388,000
42,654,000
52,313,000
66,370,000
95,916,000
83,252,000
64,403,000
77,485,250
59,137,000
93,978,000
101,316,000
73,428,000
81,964,750
69,350,000
90,784,000
89,821,000
47,160,000
74,278,750
51,635,000
56,177,000
34,861,000
33,170,000
43,960,750
25,097,000
24,722,000
24,858,000
24,064,000
24,685,250
26,704,000
25,046,000
24,703,000
25,310,000
25,440,750
Total
Summer Usage:
Winter Usage:
492,147,000
609,424,000
535,628,000
444,742,000
520,485,250
367,320,000
487,361,000
411,172,000
322,896,000
397,187,250
124,827,000
122,063,000
124,456,000
121,846,000
123,298,000
Average Monthly Winter Use:
24,659,600
Average Monthly Summer Use:
56,741,036
Average Estimated Irrigation:
224,570,050
Percent of Total:
43.1%
APPENDIX C
Table 1 - Water Balance Summary
Table 2 — Option 1 Cost Summary
Table 3 — Option 2 Cost Summary
Table 4 — Option 3 Cost Summary
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
Townhome
ent*
depth
Irrigated Area
(ac)
Volume Required to
Irrigate Area (gal)
Average Days Irrigating
from Lake Yearly
Average Daily Irrigation
Demand (gal)
Annual Lake Water
Used (MG)
Annual Lake Water
Used (ac -ft)
Annual Potable
Water Used (MG)
10.79
42,000
156
35,336
6.54
20.06
0
23.04
88,000
156
74,038
13.69
42.02
0
143.7
547,000
134
460,215
73.09
224.3
12.05
Opinion of Probable Cost
Item No.
Description
Unit
Estimated
Total
Quantity
Estimated
Unit Price
Estimated Total
Cost
A. Irrigating Public Spaces (Park and Berms)
1
MOBILIZATION
LUMP SUM
1
$8,000.00
$8,000.00
2
CLEARING AND GRUBBING
LUMP SUM
1
$500.00
$500.00
3
DEWATERING
LUMP SUM
1
$5,000.00
$5,000.00
4
2” FORCE MAIN HDPE
LIN FT
6,991
$18.00
$125,832.87
5
ELECTRICAL SERVICE
LUMP SUM
1
$12,000.00
$12,000.00
6
IRRIGATION METER AND CONTROLS
EACH
2
$3,000.00
$6,000.00
7
LIFT STATION, FILTER, CONTROLS, AND APPURTENANCES*
LUMP SUM
2
$55,000.00
$110,000.00
8
SILT FENCE, TYPE HEAVY DUTY
LIN FT
250
$3.50
$875.00
9
CONCRETE PUMP PAD
EACH
2
$1,000.00
$1,000.00
SUBTOTAL $269,207.87
+ 10% CONTINGENCY $26,920.79
CONSTRUCTION SUBTOTAL $296,128.66
+ 20% INDIRECT $59,225.73
TOTAL $356,000.00
Opinion of Probable Cost
Item No.
Description
Unit
Estimated
Total
Quantity
Estimated
Unit Price
Estimated Total
Cost
B. Irrigating Public Spaces and Townhomes
1
MOBILIZATION
LUMP SUM
1
$16,700.00
$16,700.00
2
CLEARING AND GRUBBING
LUMP SUM
1
$500.00
$500.00
3
DEWATERING
LUMP SUM
1
$5,000.00
$5,000.00
4
2" FORCE MAIN HDPE
LIN FT
6,991
$18.00
$125,838.00
5
ELECTRICAL SERVICE
LUMP SUM
1
$12,000.00
$12,000.00
6
IRRIGATION METER AND CONTROLS
EACH
3
$3,000.00
$9,000.00
7
LIFT STATION, FILTER, CONTROLS, AND APPURTENANCES*
LUMP SUM
2
$55,000.00
$110,000.00
8
SILT FENCE, TYPE HEAVY DUTY
LIN FT
250
$3.50
$875.00
9
CONCRETE PUMP PAD
EACH
2
$1,000.00
$2,000.00
11
4" FORCE MAIN HDPE
LIN FT
3,807
$18.00
$68,531.73
SUBTOTAL $350,444.73
+ 10% CONTINGENCY $35,044.47
CONSTRUCTION SUBTOTAL $385,489.21
+ 20% INDIRECT $77,097.84
TOTAL $463,000.00
Opinion of Probable Cost
Item No.
Description
Unit
Estimated
Total
Quantity
Estimated Unit
Price
Estimated Total
Cost
C. Irrigating Entire Development
1
MOBILIZATION
LUMP SUM
1
$93,100.00
$93,100.00
2
CLEARING AND GRUBBING
LUMP SUM
1
$500.00
$500.00
3
DEWATERING
LUMP SUM
1
$5,000.00
$5,000.00
4
2" FORCE MAIN HDPE
LIN FT
6,991
$18.00
$125,838.00
5
ELECTRICAL SERVICE
LUMP SUM
1
$12,000.00
$12,000.00
6
IRRIGATION METER AND CONTROLS
EACH
8
$3,000.00
$24,000.00
7
LIFT STATION, FILTER, CONTROLS, AND APPURTENANCES*
LUMP SUM
6
$55,000.00
$330,000.00
8
SILT FENCE, TYPE HEAVY DUTY
LIN FT
250
$3.50
$875.00
9
CONCRETE PUMP PAD
EACH
6
$1,000.00
$1,000.00
10
CONNECT TO POTABLE WATER
EACH
6
$8,000.00
$48,000.00
11
4" FORCE MAIN HDPE
LIN FT
36,944
$18.00
$664,992.00
12
POTABLE WATER SYSTEM OVERSIZING
LUMP SUM
1
$650,000.00
$650,000.00
SUBTOTAL $1,955,305.00
+ 10% CONTINGENCY $195,530.50
CONSTRUCTION SUBTOTAL $2,150,835.50
+ 20% INDIRECT $430,167.10
TOTAL $2,582,000.00
APPENDIX D
Water Balance Technical Memo
Feasibility Report
Mattamy Homes Water Reuse
WSB Project No. 2988-01
WSB
/111111111111111111,,,,engineering • planning. environmental- construction 701 Xenia Avenue South
Suite 300
Minneapolis, MN 55416
Tel: 763-541-4800
Fax: 763-541-1700
January 21, 2016
Mr. Mike Grochala, AICP
Community Development Director
City of Lino Lakes
600 Town Center Pkwy
Lino Lakes, MN 55015
Re: Mattamy Homes Water Reuse — Water Balance Technical Memorandum
WSB Project Number 02988-01
Dear Mr. Grochala:
We are providing you this technical memorandum to summarize the results of the water balance
model for the water reuse feasibility study in the Mattamy Homes development. This document
describes the methodology used to calculate the quantity of stormwater available and the amount
used for irrigation purposes.
Project Background
The City of Lino Lakes wishes to implement a water reuse program using water from the lake in
the Mattamy Homes development to irrigate portions of the development. There are three
potential scales with respect to water reuse that were evaluated. The first is using water in the
lake to irrigate the development's park and the berms on the eastern edge of the development.
The second is to irrigate the park and the berms as well as the townhomes in the southeastern
corner of the development. Finally, the water balance modeled the feasibility of irrigating the
entire development, including single-family homes, with water from the lake.
Water Balance Theory
The water balance presented in this document evaluates the amount of water provided to the
pond via stormwater runoff, the amount that will be withdrawn for irrigation, and the resulting
lake levels. The estimate takes into consideration precipitation, runoff, evaporation, irrigation
demand, and pond overflow. While water balances rely on historic data and do not predict future
climate patterns, they are a helpful tool when determining if stormwater irrigation is feasible, and
if so, whether or not potable water augmentation will be required.
Calculating Drainage Area
To determine the amount of water available for irrigation, the drainage area to the lake was taken
from the current Lino Lakes Northeast Study being conducted by WSB & Associates for the
City. In addition, drainage information was obtained from the the developer to estimate the area
in the future development that will drain to the lake.
Equal Opportunity Employer
wsbeng.com
Mr. Mike Grochala
January 21, 2016
Page 2
The purpose of the water balance is to determine if the lake holds enough water for irrigation
purposes throughout the irrigation season. Therefore, a conservative approach was taken when
estimating the drainage area; only the immediate drainage within the development was
considered for the water balance.
Calculating Precipitation
Rainfall data was obtained from the Minnesota Climatology Working Group. Data was available
beginning on May 1, 1959, and extending to June 30, 2015. Days in which rainfall data was
missing were assumed to have received no precipitation.
Calculating Runoff
The water balance uses the United States Department of Agriculture (USDA) Natural Resources
Conservation Service method for determining runoff. This method, commonly known as the SCS
Runoff Curve Number method, has widespread use in hydrologic modeling. The curve number
for the drainage area was calculated as part of the Lino Lakes Northeast Study. The curve
numbers for the drainage area within the development was estimated using soil type and single -
and multi -family residential published curve numbers. Using the calculated curve numbers, an
S -value (the amount of maximum soil moisture retention after runoff begins) was determined
using the following equation:
1000
_
S 10
Curve Number
From the S -value, the initial abstraction (Ia) was calculated as 0.2*S, per the USDA. To predict
the amount of runoff (Q) from a particular rain event, the USDA gives the equation:
Q = {0 for P < IQ
(P-102 for P > 1
P—Ia+S
The equation dictates that there is no runoff from a storm where the amount that falls (in inches)
is less than the initial abstraction. In the single-family residential area, a storm of 0.47 inches is
required, and in the multi -family residential (townhome) area, a storm of 0.26 inches is required.
In the model, runoff from the three areas was considered independently to ensure the most
accurate estimate of total runoff volume possible. Using the equation above, the runoff entering
the lake was evaluated for each rain event from the historical rainfall data.
Calculating Pond Volume
Pond volume was determined using contour data from the grading plan for the lake. First, a stage
to surface area relationship was developed using surface area from the grading plan. Once the
surface area was evaluated at several elevations, the trapezoidal method was used to estimate
overall pond volume as well as the volume at several elevations. The storage capacity of the
pond is approximately 122 million gallons, with a volume of 86 million gallons at the normal
water elevation. The total possible volume was assumed to be the volume at the overflow
Mr. Mike Grochala
January 21, 2016
Page 3
elevation. The grading plans assume a normal water level of 900 feet, which was set as the initial
lake volume for modeling purposes.
Calculating Evaporation
Based on the estimated volume contained in the lake, the surface area was calculated in Excel
using the Forecast function. The Forecast function gives a predicted value of a variable using a
linear regression analysis. In this case, the function uses the elevation -surface area data
calculated in the pond volume analysis to predict what the surface area would be for any volume
of water. This is a necessary component for the model because the volume analysis as outlined in
the previous section gives volume at one foot increments only. Once the surface area is
estimated, the amount of evaporation is predicted using the pan evaporation method with a pan
coefficient, as outlined by the University of Minnesota. The guiding document recommends a
pan coefficient of 0.75 for Minnesota. The equation used is below:
36.98 inches
Evaporation = Water Surface Area (ft2)x 0.75 x 12 inches/ ft
The value of 36.98 inches is the average pan evaporation for the State of Minnesota between
1974 and 2004. The equation above provides annual evaporation. Therefore, in the water
balance, the value was divided by 180, or the approximate number of days in which evaporation
occurs annually.
Calculating Irrigation Requirements
Using aerials and plans provided by the developer, the irrigated area was estimated for the
berms, park, townhomes, and single-family homes. It is estimated that to maintain a lawn, one
inch of water is required per week (including precipitation). 1 -inch of irrigation weekly results in
an average of 1/7, or 0.14, inches per day. Therefore, if the rainfall is greater than 0.14 inches in
a given day, it was assumed in the water balance that irrigation did not occur that day.
Rice Creek Watershed District rules dictate that stormwater irrigation occurs, at maximum, from
April 15 to October 15 for the generation of volume reduction credits. The water balance
calculates irrigation between these dates.
Phase
Irrigation Volume per Day (gal)
1. Park and berms only
42,000
2. Park, berms, and townhome area
88,000
3. Park, berms, townhome area, single family area
546,150
Water Balance: Final Calculation and Results
Once all of the above parameters were calculated, the balance was conducted to determine lake
levels throughout the irrigation season. The overall water balance equation is as follows:
Pond Volume = Initial Pond Volume + Stormwater Runoff + Ditch Inflow — Discharge — Evaporation — Irrigation
The average annual precipitation, including snowmelt, was 33.5 inches. The model predicted that
on average, irrigation will occur 156 days each year, out of 184 possible irrigation days. This
Mr. Mike Grochala
January 21, 2016
Page 4
leads to a weekly irrigation depth of 0.84 inches, resulting in a total water depth of 1.6 inches
applied to the turf on a weekly basis, including precipitation. Studies conducted by the
University of Minnesota indicate that this irrigation rate is likely slightly more than necessary
given the soils and precipitation. A small overestimation of the irrigation rate is desired so that
the model is conservative.
Option 1: Irrigating Public Spaces with Storm Water
Option 1 resulted in a daily irrigation rate of 42,000 gallons on days in which irrigation occurred
(days in which precipitation was less than 1 /7 -inch). The water balance model indicates that the
storage can sufficiently supply water for irrigation of the public spaces with minimal effect on
storage levels. Evaporation and irrigation combined resulted in maximum storage level
fluctuation of 36.8 million gallons (MG), or 4 feet in elevation change. Option 1 is feasible in
terms of water supply.
Option 2: Irrigating Public Spaces and Townhomes with Storm Water
Option 2 resulted in a daily irrigation rate of 88,000 gallons on days in which irrigation occurred.
The water balance model indicates that the storage can sufficiently supply water for irrigation of
the public spaces and townhome properties with minimal effect on storage levels. Evaporation
and irrigation combined resulted in maximum storage level fluctuation of 37.0 MG, or 4 feet in
elevation change. Option 2 is feasible in terms of water supply.
Option 3: Irrigating all of the Mattamy Development with Storm Water
Option 3 resulted in a daily irrigation rate of 547,000 gallons. The storage cannot supply enough
irrigation water to support this option. The model showed that storage levels will reach
approximately two feet in depth during the summer if irrigating at this rate. A protective
elevation can be set, such that at a certain storage depth the irrigation system does not run.
Depending on the elevation chosen, the system will turn off for different time ranges. If, for
example, the protective elevation is 896 feet (corresponding two an eleven foot depth), the
system would run off of potable water an average of 22 days per summer. Given the system and
operating cost, Option 3 is not feasible in terms of water supply.
Please contact me at (763) 287-8319 with any questions.
Sincerely,
WSB & Associates, Inc.
Erin Heydinger
Mr. Mike Grochala
January 21, 2016
Page 5
Sources:
Gulliver, J.S., A.J. Erickson, and P.T. Weiss (editors). 2010. Stormwater treatment: Assessment
and Maintenance. University of Minnesota, St. Anthony Falls Laboratory. Minneapolis, MN.
http://stormwaterbook. safl. umn. edu/content/evaporation-and-evapotranspiration
Minnesota Climatology Working Group. Nearest Station Precipitation Data Retrieval. Available
online: http://climate.umn.edu/HlDradius/radius new.asp
USDA. Urban Hydrology for Small Watersheds — Technical Review 55. Available online:
http://www.nres.usda.gov/Internet/FSE_DOCUMENTS/stelprdb 1044171.pdf