HomeMy WebLinkAbout1.c. Sewer
DRAFT
Feasibility Report
Comprehensive Sewer Plan
City of Rosemount
May 2018
Submitted by:
Bolton & Menk, Inc.
1960 Premier Drive
Mankato, MN 56001
P: 507-625-4171
F: 507-625-4177
Prepared by: Bolton & Menk, Inc. Certification
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157]
Certification
Feasibility Report
for
Comprehensive Sewer Plan
City of Rosemount
T18.114157
May 2018
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.
By:
, P.E.
License No.
Date:
Prepared by: Bolton & Menk, Inc. Table of Contents
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] i
Table of Contents
1. EXECUTIVE SUMMARY .......................................................................................... 1
2. BACKGROUND .......................................................................................................... 3
3. Land Use ....................................................................................................................... 3
Land Use Categorization .................................................................................. 3
Developable Areas ........................................................................................... 3
4. Growth Projections ....................................................................................................... 4
Projected Residential Growth ........................................................................... 4
Projected Non-Residential Growth .................................................................. 5
Projected Land Use Phasing and Summary ..................................................... 5
5. Existing Sanitary Sewer System ................................................................................... 6
Current Service Areas ...................................................................................... 6
Existing Wastewater Flows .............................................................................. 6
Infiltration/Inflow ............................................................................................. 8
Evaluation of Existing Facilities .................................................................... 10
6. FUTURE SANITARY SEWER SYSTEM ................................................................ 11
Future Service Areas ...................................................................................... 11
Future Waste Water Flows ............................................................................. 12
Future Trunk Sanitary Sewer System ............................................................. 18
7. CAPITAL IMPROVEMENTS PLAN (CIP) .............................................................. 21
Estimated Cost of Trunk System Improvements ............................................ 21
Future Trunk System Funding ........................................................................ 22
Tables
Table 1 Capital Improvement Plan by Sewershed 2
Table 2 Gross Developable Acreage 4
Table 3 MCES Population Estimates 4
Table 4 Potential Ultimate Service Area 6
Table 5 Existing Wastewater Generated per Sewershed 7
Table 6 Water Demand to Wastewater Flow Ratio 8
Table 7 Existing Peak Flow Factors 9
Table 8 Existing Lift Station Capacities and Flows 10
Table 9 Existing System Trunk Main Capacity 11
Table 10 Summary of Gross Developable Acres by Sewershed 14
Table 11 Future Wastewater Flows by Sewershed 15
Table 12 Ultimate Regional Wastewater flows by MCES Connection Point 16
Table 13 Future Regional Wastewater FLow my MCES connection point and 10-year Increment 17
Table 14 Capital Improvement Plan by Sewershed 22
Table 15 Core Fund Assume Gross Acres Development 23
Prepared by: Bolton & Menk, Inc. Table of Contents
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] ii
Appendix
Appendix 1: Figures
Appendix 2: Opinion of Probable Costs
Appendix 3: Trunk Facility Construction Schedule
Appendix 4: Dakota County Maintenance Facility and Communications Center Cooperative
Agreement
Prepared by: Bolton & Menk, Inc. EXECUTIVE SUMMARY
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 1
1. EXECUTIVE SUMMARY
The Comprehensive Sanitary Sewer Plan is intended to serve as a guide to completing the future sanitary
sewer trunk system, and to help the City of Rosemount meet its short-term and long-term sanitary sewer
needs. The report, analysis, and figures were based on the City’s existing sanitary sewer system and
future development plans as of July 31st, 2018. Future development plans or the existing sewer system
may have changed since the “snapshot” in time the report was based on.
To estimate existing system wastewater flows and project future system wastewater flows the ultimate
land use plan was used as opposed to the 2040 land use plan. There are differences between the land use
plans, however, it was important to size infrastructure for service beyond the 2040 land use plan. The
ultimate land use plan included in Figure 3-1 was used for ultimate system infrastructure sizing.
Estimated flows for each of the MUSA boundaries were also calculated and can be found in Section 6.2
of the attached report.
The existing area with sanitary sewer service has been divided into sixteen (16) sewersheds, of which the
majorities are fully developed in accordance with the ultimate land use plan. Wastewater is collected by
the City’s sewer system, then conveyed to Metropolitan Council Environmental Services (MCES)
interceptors that flow to MCES wastewater treatment plants. The majority of the City’s existing sewage
flows to the Empire Wastewater Treament plant The existing sanitary sewer system is shown in Figure 5-
1.
The future service area was divided into seven (7) sewersheds. Existing and future sewersheds are shown
in Figure 6-1. Each sewer shed contributes wastewater flow to the sanitary sewer collection system. The
volume of wastewater that each sewer shed contributes depends on the future land use.
The topography of the undeveloped areas was studied to determine the extents of gravity sewer areas for
future trunk facilities. The intention with laying out the future system was to minimize the number of
trunk lift stations, while keeping the maximum depth of gravity sewers to less than 35 feet deep. The
City’s topography generally slopes from west to east, making it possible to avoid constructing many lift
stations. The layout of the future trunk sewer system is shown in Figure 6-2. The layout is general in
nature and exact routing will be determined at the time of final design. It is important that the general
concept and sizing be adhered to for assurance of an economical and adequate ultimate system.
Construction cost estimates were developed for the completion of the trunk sewer system. Typically,
developers are required to construct sewers and lift stations necessary to serve their development at their
own cost. Some gravity trunk sewers included in the ultimate system for this plan were as small as 8
inches in diameter, which is the minimum sewer size construction standards allow. It was assumed that
developers would fund and construct all 8-inch sewers, so the estimated quantity of trunk sewers 8 inches
in diameter has been included, but not the cost.
Prepared by: Bolton & Menk, Inc. EXECUTIVE SUMMARY
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 2
Table 1 below shows the estimated system expansion costs. Future improvement costs were based on
2007 construction prices, including a 10% construction contingency, and including 30% overhead (i.e.,
legal, engineering, and administrative). Street and easement costs and other miscellaneous costs that may
be related to final construction are not included. Detailed cost estimates for each district are available in
Appendix 2. Furthermore, construction schedules for trunk facilities in each sewer shed are included
Appendix 3. Current development fees were reviewed and appear to be adequate to fund the future
system expansion costs, but should be reviewed on a regular basis.
Table 1 Capital Improvement Plan by Sewershed
Capital Improvement Plan by Sewershed
District 2020 2030 2040 Ultimate Total
MWCC09 $0 $2,727,922 $0 $1,004,202 $3,732,124
Southeast $0 $5,415,200 $13,585,978 $0 $19,001,178
South Central $0 $1,356,162 $353,930 $3,556,893 $5,266,985
MWCC08 $1,944,498 $5,757,143 $0 $7,846,927 $15,548,568
Southwest $0 $0 $0 $1,078,451 $1,078,451
Lan-O-Ken $0 $969,620 $0 $0 $969,620
Northwest $0 $0 $0 $413,700 $413,700
MWCC10 $0 $456,680 $0 $0 $456,680
Total $1,944,498 $16,682,727 $13,939,908 $13,900,173 $46,467,306
1. Costs are for budgeting purposes only, and are subject to change as projects are studied,
designed, and constructed.
2. Costs are estimated based on 2007 construction costs.
3. Land acquisition costs are not included.
Prepared by: Bolton & Menk, Inc. BACKGROUND
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 3
2. BACKGROUND
The City of Rosemount is located in north central Dakota County in the southeast suburbs of the Twin
Cities Metropolitan area. Rosemount has experienced considerable growth in recent years and anticipates
similar growth to continue. It continually experiences development pressures due to its location relative
to transportation arterials (US 52) and its proximity to St. Paul.
The purpose of this study is to update the existing Comprehensive Sanitary Sewer System Plan in
accordance with Minnesota Statute 473.513. It provides the City with a plan to serve future development
and an estimate of future sanitary sewer system costs. The plan provides flow projections through the
year 2040, and ultimate system development in accordance with the City’s Comprehensive Plan.
This plan examined sanitary sewer service to future development. Population and water use estimates
from the City’s Comprehensive Water System Plan, initially from the Comprehensive Plan, were used to
maintain consistent planning for water and sewer service. Also, the plan estimated opinions of probable
cost for future improvements to develop a Capital Improvement Plan (CIP).
Sanitary sewer plans have been developed for various locations throughout Rosemount. However, these
studies have not been linked together to examine the future system as a whole. This study will tie
together previous studies in a sanitary sewer model (SewerCAD V8i) in an effort to determine service
requirements for all remaining developable acres.
The existing sanitary sewer system is sufficient to serve the existing developed area and was not included
in the SewerCAD model. However, the existing sewers were included in the analysis to confirm the
capacity was adequate to serve existing development and future development if necessary.
3. LAND USE
Land Use Categorization
Figure 3-1 is the current ultimate land use plan for the City of Rosemount. The ultimate land use
plan was used in order to size infrastructure appropriately beyond the 2040 time frame. This plan
was developed by the City and separates the planning area into fifteen (15) different land use
categories. Land use is a critical factor in locating and sizing future sanitary sewers because
different land uses generate different wastewater flow rates. Further detail regarding wastewater
flows generated by existing and future land uses is discussed in Sections 5 and 6.
Developable Areas
The area within Rosemount’s planning area is approximately 34 square miles or 21,800 acres,
excluding the river/wetland area for the Mississippi River in the northeast area of the City. There
is approximately 2,400 acres of undevelopable area (agriculture). Within the City, approximately
5,100 acres are developed with sewer service, and 2,800 acres are developed without sewer
service. Therefore, the total remaining developable area within the City’s planning area is
approximately 8000 acres.
The total acreage for each land use area was calculated. Existing developed, serviced and
unserviced areas, and undevelopable areas were subtracted to obtain developable acreage. This is
identified as “Gross” Developable Acreage because it includes roads and common or public areas
potentially included in developments. Roads, common areas, and parks typically consume 25%
to 30% of the gross area within a development. The Gross Developable Acreage by land use
categories is summarized in Table 2 and identified in Figure 3-2. Figure 3-2 indicates whether an
area is developed or available for future development.
Prepared by: Bolton & Menk, Inc. Growth Projections
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 4
Table 2 Gross Developable Acreage
Gross Developable Acreage
Land use Acres
Agricultural Research 0
Agriculture 0
Business Park 1905
Corporate Campus 508
Downtown 0
Existing Parks/ Open Space 0
General Industrial 603
High Density Residential 145
Industrial/Mixed Use 350
Medium Density Residential 703
Neighborhood Commercial 26
Public Institutional 0
Regional Commercial 261
Rural Residential 0
Transitional Residential 0
Urban Residential 3369
Waste Management 0
Total 7869
4. GROWTH PROJECTIONS
Projected Residential Growth
Rosemount’s 2010 population was 21874. In the last eight years, Rosemount’s population has
grown approximately 10%, with the bulk of growth occurring in areas receiving sewer service.
According to the 2000 and 1990 censuses, populations were 14,619 and 8,622, respectively.
Estimates of the population of the City of Rosemount, as published the Met Council have been
published and are shown in Table 3 below.
Table 3 MCES Population Estimates
MCES Population Estimates
Population
2010 2020 2030 2040
21874 25900 31700 35600
Households
2010 2020 2030 2040
7587 9300 11600 11500
Employment
2010 2020 2030 2040
6721 9900 13500 13100
Prepared by: Bolton & Menk, Inc. Growth Projections
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 5
DNR State Public Water Supply Inventories were obtained for the years 2000 through 2005 to
determine the number of water connections in the City’s system. Typically, the number of water
and sewer connections is equal, so sewer and water connections were assumed equal. Based on
the number of residential connections (4,127-2000 and 5,801-2005) and the estimated serviced
population (2000-12,801 and 2005-17,600), there are approximately three residents for every
connection. Should this trend continue, there would be approximately 12,700 residential
connections by the year 2040 based on the population projections. Further detailed growth
projections are included in Sections 5 and 6.
Projected Non-Residential Growth
In the past, Rosemount has attracted industrial and public/institutional growth. A major industrial
park consisting of Flint Hills Resources (an oil refinery serving much of the upper Midwest) and
several smaller industrial users is located along US Highway 52 and north of County Road 42.
Dakota Technical College is located one mile east of downtown, and the University of Minnesota
owns approximately 3,000 acres south of County Road 42 and east of Biscayne Avenue.
The non-residential growth trend will most likely continue in the future with the potential
development of new general industrial and commercial districts.
Flint Hills Resources, Dakota Technical College, and Rosemount Public Schools currently
comprise the major non-residential water users for the system, and assumed sewage flow
contributors. There are growth opportunities for these customers and these opportunities have
been accounted for by the City in the proposed land use plan. Also, these major customers have
been included in determining the appropriate wastewater flow per acreage per land use type.
Non-residential connection categories listed in the DNR State Public Water Supply Inventories
(2000-2005) included commercial, industrial, and other. Therefore, water customer categories do
not correlate directly to land use type. For that reason, non-residential connections have been
grouped together to determine future.
Non-residential water connections have grown consistently. Based on the number of non-
residential connections (156-2000 and 188-2005) and the estimated serviced population (2000-
12,801 and 2005-17,600), there are 80 to 90 residents for every non-residential connection.
Should this trend continue, there would be approximately 475non-residential connections by the
year 2030. Further detailed growth projections are included in Sections 5 and 6.
Projected Land Use Phasing and Summary
Potential service areas are shown in Figure 4-2 and summarized in Table 4. The potential service
area is shown for the years 2007, 2010, 2020, 2030, and ultimate developmen. Growth is
projected to occur primarily by surrounding the existing western service area then expanding
eastward.
Prepared by: Bolton & Menk, Inc. Existing Sanitary Sewer System
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 6
Table 4 Potential Ultimate Service Area
Potential Ultimate Service Area
MUSA 2020 2030 2040 Ultimate
Total Service Area
(ac)
5920 15691 18186 20787
5. Existing Sanitary Sewer System
Current Service Areas
Sanitary sewer systems consist of two elements: collection and treatment. The existing City
sanitary sewer system is a collection system only, MCES is responsible for treatment. Also,
MCES is responsible for major trunk facilities conveying wastewater across City boundaries to
treatment facilities.
The MCES Rosemount Interceptor flows from west to east across Rosemount to the existing
Rosemount wastewater treatment plant. However, future flows will not be treated at the
Rosemount wastewater treatment plant, but conveyed by the Empire Interceptor southwest to the
Empire wastewater treatment plant for treatment.
The existing service area is defined as the area from which wastewater flows are collected, and is
approximately 5,100 acres. It can be broken down into sewersheds based on its connection points
to MCES interceptors, City trunk sewers, and lift station service areas. Figure 5-1 shows the
existing service area, sewersheds, MCES interceptor sewers, and the City sewer system, including
lift stations.
As discussed in Section 3, there is still much developable land available within the City;
therefore, sewer service has not been extended to all properties. There are approximately 580
remaining properties that are not served by the City. The remaining unserved properties are
generally located in the undeveloped eastern area and northwestern rural residential area, but
there are some Individual Sewage Treatment Systems (ISTSs) scattered throughout the existing
served area. Figure 5-2 shows the existing ISTSs within the City limits.
Existing Wastewater Flows
5.2.1 Existing Sewershed Flows
The City’s existing sanitary sewer system shown in Figure 5-1 identifies trunk sewers,
MCES interceptors, lift stations, and resulting existing sewersheds. The flow meters and
lift station service areas were reviewed to estimate the existing sanitary sewer flow within
each sewer shed. The estimated unit wastewater flow, discussed in the following section,
was multiplied by the number of existing platted units. Table 5 shows the estimated
average flow rates for the City’s existing sewersheds compared to the 2017 average flow
rates measured by the MCES flow meters in Million Gallons per Day (MGD). A possible
explanation for the difference between estimated and metered data is that some units may
be platted but not constructed or occupied, resulting in a higher quantity of existing units
generating wastewater flow. Another factor is that the flowrates used in design tend to be
conservative in nature and over predict the actual flow contributions.
Since existing flows for each sewer shed did correlate to the total existing flows
measured at the MCES flow meters M641 and M655, estimated unit wastewater flows
were assumed to be a level of accuracy sufficient for determining existing infrastructure
capacity.
Prepared by: Bolton & Menk, Inc. Existing Sanitary Sewer System
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 7
Table 5 Existing Wastewater Generated per Sewershed
Existing Waste Water Generated per Sewershed
Sewershed
Estimated Average
Flow (MGD)
Metered Average
Flow (MGD)
LS 3 0.335
Danville 0.101
M641 0.436 0.294
150th 0.191
Canada 0.104
LS 1 0.046
LS 4 0.126
LS 5 0.138
LS 6 0.007
LS 7 0.023
LS 8 0.089
LS 9 0.041
Auburn 0.013
Business
Parkway 0.085
Biscayne 0.079
Connemara 0.233
Lan-O-Ken 0.117
MWCC10 0.018
MWCC08 0.063
M655 1.729 1.137
5.2.2 Estimated Unit Wastewater Flows
The Comprehensive Water System Plan provided a detailed analysis of the estimated unit
water demand for each land use type. The analysis found the existing land uses exhibited
the following water demands:
Residential – 95 gallons/capita/day (gpcd)
Public/Institutional – 250 gallons/acre/day (gpad)
Commercial – 800 gallons/acre/day
Industrial – 800 gallons/acre/day
Flint Hills/Waste Management – 55 gallons/acre/day
To verify existing sanitary sewer flows as a percentage of water demand, annual average
flows were compared to winter water usage in Table 6 below. Winter average water
usage (October through March) correlated 100% to average sanitary sewer flows.
Therefore, the difference in annual water demand and sanitary sewer flows is caused by
Prepared by: Bolton & Menk, Inc. Existing Sanitary Sewer System
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 8
lawn watering. The ratio of annual water usage to annual wastewater flow is shown in
Table 6 as well.
Table 6 Water Demand to Wastewater Flow Ratio
Water Demand to Wastewater Flow Ratio
2002 2003 2004 Average
Winter Water Use (MGD) 1.031 1.086 1.129 1.082
MCES Sanitary Annual Avg. Flow (MGD) 1.062 1.091 1.157 1.103
WW/Water Ration Winter Avg 103.00% 100.48% 102.44% 101.97%
Annual Daily Water Use (MGD) 1.463 1.872 1.818 1.718
MCES Sanitary Annual Avg. Flow (MGD) 1.062 1.091 1.157 1.103
WW/Water Ratio Annual Avg 72.58% 58.29% 63.62% 64.23%
Since the majority of Rosemount is residential, it is critical to accurately represent
residential density in sewer planning and design. Existing development densities for the
serviced area were determined in the Comprehensive Water System Plan (Water Plan),
and were based on typical development densities for each land use found throughout the
City at the time. At the time the water plan was completed, there were 2,400 developed
residential acres, 6,013 residential connections, and a serviced population of 18,038,
yielding 2.5 units/acre and 3.0 people/connection. The Water Plan projected the
following densities (per gross acre) per residential land use type.
Urban Residential – 3 units/acre (future), currently 2.6 units/acre
Transition Residential – 2 units/acre
High Density Residential – 12 units/acre (future), currently 10 units/acre
Medium Density Residential – 7 units/acre
Each land use type was assumed to have 3.0 people/unit and 65% of water use flows to
sanitary sewers as evidenced by Table 6 above. Therefore, the resulting wastewater flow
for each existing residential unit was assumed to be 185.25 gallons per day (gpd) per unit
(95 gpcd X 3 people/unit X 65%).
Infiltration/Inflow
5.3.1 General
Infiltration is water that enters the sanitary sewer system by entering through defects in
the sewer pipes, joints, manholes, and service laterals, or by deliberate connection of
building foundation drains. Water that enters the sewer system from cross connections
with storm sewer, sump pumps, roof drains, or manhole covers is considered inflow.
Water from inflow and infiltration can consume available capacity in the wastewater
collection system and increase the hydraulic load on the treatment facility. In extreme
cases, the added hydraulic load can cause bypasses or overflows of raw wastewater. This
extra hydraulic load also necessitates larger capacity collection and treatment
components, which results in increased capital, operation and maintenance, and
replacement costs. As sewer systems age and deteriorate, I/I can become an increasing
problem. Therefore, it is imperative that I/I be reduced whenever it is cost effective to do
so.
Prepared by: Bolton & Menk, Inc.
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 9
The MCES has established I/I goals for each community discharging wastewater into the
Metropolitan Disposal System (MDS). In February 2006, MCES adopted an I/I
Surcharge Program which requires communities within their service area to eliminate
excessive I/I over a period of time. All communities exceeding their wastewater flow
goal for the period of June 1, 2004, through June 30, 2006, were charged at the beginning
of 2007, and from July 1, 2006, to June 30, 2007, will be charged at the beginning of
2008. The City of Rosemount was not identified by MCES as a community with
excessive I/I and, therefore, is not on the MCES I/I Surcharge List.
5.3.2 I/I Analysis
The majority of the City’s existing sanitary sewer system has been constructed within the
last twenty years. City construction standards have been followed to minimize I/I flow
contributions to the system.
Included in the City’s System Statement for the 2030 Regional Development Framework
adopted by the Metropolitan Council in 2004 was the City’s I/I goal for the years 2010,
2020, and 2030 based on MCES assumed flow increases. MCES assumed peak flow
factors used as the limit for peak I/I flow rates are variable depending on the average
flow. The sliding scale used by MCES has been included in Appendix 1. The City’s
current peaking factors are well below the MCES guidelines as shown in Table 7 below.
Table 7 Existing Peak Flow Factors
Existing Peak Flow Factors
Year
Average
Flow (MGD)
Peak Flow
(MGD)
City Peaking
Factor
MCES
Maximum
Peak Factor
M641
2013 0.303 3.8
2014 0.293 3.9
2015 0.29 3.9
2016 0.31 3.8
2017 0.273 3.9
M655
2013 1.109 3.3
2014 1.137 3.3
2015 1.141 3.3
2016 1.157 3.3
2017 1.139 3.3
Total
2013 1.412 3.2
2014 1.43 3.2
2015 1.431 3.2
2016 1.467 3.2
2017 1.412 3.2
Prepared by: Bolton & Menk, Inc.
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 10
5.3.3 Municipal I/I Reduction
The City’s strategy for preventing excess I/I is based on requiring new development to
conform to City standards and ongoing maintenance. The City performs maintenance on
the sanitary sewer system on a consistent basis, and the City reconstructs several streets
within the City annually. As a part of street reconstruction projects, sanitary sewers are
replaced or lined if they are in poor condition.
The City construction standards include prohibiting the connection of sump pumps, rain
leaders, and passive drain tiles to the sanitary sewer system. All developments are
designed and constructed as public improvement projects, therefore projects conform to
the City construction standards. In addition, development construction is observed to
verify construction is in accordance with plans and City standards. All newly constructed
sanitary sewers are televised and pressure tested to confirm they have been constructed in
accordance with City standards.
Evaluation of Existing Facilities
5.4.1 Wastewater Treatment
As discussed previously, the City of Rosemount is responsible for wastewater collection
only. Treatment is provided by MCES at the Empire wastewater treatment plant. The
Empire wastewater treatment plant is located south of Rosemount in Empire Township.
There are approximately 480 remaining properties within the City with ISTSs. These
properties are shown in Figure 5-2.
Property owners with ISTSs are required to connect to the City collection system within
ten (10) years of City service becoming available or when the City has determined the
ISTS has failed, whichever is earlier.
5.4.2 Lift Stations
The City currently has nine lift stations in service and their locations are noted on Figure
5-1. The total capacity, existing flow, and ultimate future flow for each lift station is
listed below in Table 8. Based on the service areas for Lift Stations No. 1 and No. 8,
estimated existing peak flows exceed the lift station capacity. However, City staff has
indicated that there have not been any incidents involving flows exceeding lift station
capacity
Table 8 Existing Lift Station Capacities and Flows
Existing Lift Station Capacities and Flows
Lift
Station
Estimated
Existing Avg
Flow (gpd)
Estimated
Ultimate Ave.
Flow (gpd)
Estimated
Ultimate Peak
Flow (gpd)
Lift Station
Capacity
(gpd)
LS 1 45993 45993 183971 432000
LS 3 335168 388758 1399528 1267200
LS 4 125970 125970 491283 864000
LS 5 138382 138382 539689 612000
LS 6 7410 7410 29640 50400
LS 7 23156 23156 92625 90720
LS 8 89291 89660 358639 64800
LS 9 41126 41126 164502 21600
LS 10 58870 58870 235480 172800
Prepared by: Bolton & Menk, Inc. FUTURE SANITARY SEWER SYSTEM
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 11
5.4.3 Trunk Mains
The existing City of Rosemount sanitary sewer system is comprised of gravity sewers
ranging in size from 6 inches in diameter to 30 inches in diameter. The City sanitary
sewer mains flow to the MCES interceptor sewers. The MCES interceptor sewers
provide service to the City of Rosemount only. Figure 5-1 shows the existing City
sanitary sewers and MCES interceptor.
Existing peak flows from each sewer shed were estimated based on the developed area
within each sewer shed and estimated unit wastewater flow. Table 5 shows the existing
average flows generated in each of the sewersheds; however, Table 9, below, shows the
peak flows from each sewer shed used to evaluate the adequacy of the existing trunk
sewer system. Table 9 indicates that all existing City trunk mains except for M641, have
adequate capacity to serve ultimate flows. The estimated peak flows at M641 are
marginally above the estimated ultimate peak flows. Further analysis of the existing
sewer should be completed to determine the remaining capacity in the line before any
substantial future development is undertaken.
Table 9 Existing System Trunk Main Capacity
All peak flows shown in the above Table 9 are based on MCES supplied peaking factors.
This variable ratio, called the peak flow factor, has been found to decrease as the average
flow increases. They are generally considered conservative, and are widely used for
planning in municipalities throughout the Twin Cities metropolitan area. Appendix 1
lists the peaking factors for this study.
5.4.4 Summary of Existing System Evaluation
Existing system infrastructure including gravity mains, lift stations, and force mains has
adequate capacity to serve existing system flows. Lift Stations No. 3, No. 7, No. 8 and
No. 10 may exceed ultimate peak flows and should be monitored by City staff.
6. FUTURE SANITARY SEWER SYSTEM
Future Service Areas
The future sanitary sewer system is based upon dividing up the ultimate potential service area
into major service areas or sewersheds and then dividing those major sewersheds into sub-
sewersheds. The existing City sewer shed locations were dictated by the location of existing
infrastructure; however, selection of future sewersheds was generally governed by existing
Existing System Trunk Main Capacity
Trunk Main
Existing
Trunk Main
Size (in)
Existing
Trunk Main
Capacity
(MGD)
Estimated
Ultimate
Average
Flow (MGD)
Estimated
Ultimate
Peak Flow
(MGD) Contributing Sewersheds
M641 15 1.617 0.472 1.651 Danville, LS 3
150th 27 5.181 0.990 3.167 LS 4, LS 5, LS 6, 150th, Canada,
LS 1, Biscayne, Business Pkwy
Lan-O-Ken 18 2.351 0.153 0.598 Northwest, Lan-O-Ken
Connemara 30 6.384 0.461 1.612 Connemara, LS 9, Lan-O-Ken,
Northwest, MWCC10
Prepared by: Bolton & Menk, Inc. FUTURE SANITARY SEWER SYSTEM
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 12
topography and or other existing features such as roadways. In addition, determining future
sewersheds was generally not affected by existing sewer shed locations, because existing
sewersheds typically flow into MCES interceptors without crossing undeveloped areas.
The ultimate future potential service area was broken up into seven (7) major sanitary sewer
districts: Northwest, MWCC08, MWCC09, Southwest, South Central, Southeast, and West
Central. Figure 6-1 shows the future sewersheds, and the existing sewersheds. The Northwest,
Lan-O-Ken, MWCC10, and North Central sewersheds were determined based on previous studies
including the North Central Sanitary Sewer Study and the CSAH 42/Akron AUAR.
The following is a brief summary of the steps taken to develop the future trunk sanitary sewer
system based upon the ultimate service area:
1) The ultimate potential service area was determined by eliminating large areas not likely
to be served in the future, which generally included the area surrounding Flint Hills
Resources.
2) The service area was divided into sub-sewersheds based on gravity sewer constraints and
roadway boundaries. Sanitary sewers were designed with minimal crossing of higher
capacity roads such as CSAH 42 and TH 52.
3) Sanitary sewer flows were generated for each sub-sewer shed based on the gross
developable acreage and the anticipated land use. The wastewater flow generation rates
for the various land use categories discussed in this section were used to project future
wastewater flows.
4) The sanitary sewer system was developed using the existing MCES interceptors as trunk
sewers except in the east. Future trunk sewers in the east area were laid out based on
ground contours which govern how far the gravity trunk sewers can feasibly be extended.
All trunk sewers were designed to be no deeper than 35 feet, and no shallower than 8 feet
from the existing ground surface.
5) Gravity sewer mains, lift stations, and force mains needed to accommodate the ultimate
service area were then sized for peak sanitary sewer flows from those sub-districts which
are tributary to each particular trunk gravity sewer main or lift station.
The remaining developable area, summarized in Table 2and shown in Figure 3-2, has been further
broken down by sewer shed and is shown in Table 10 on the following page. The Table shows
amount of developable area in each sewer shed by land use category. Some of the existing
sewersheds have been included because the sewer shed has not been fully developed.
Future Waste Water Flows
6.2.1 Estimated Unit Wastewater Flows
Future sanitary sewer flows, in conjunction with available slope, govern the capacity of
sanitary sewers. To determine future sanitary flows, existing water demand and MCES
recommendations were considered. MCES typically estimates 274 gpd/connection or 75
gpcd for residential estimates and 800 gpad for non-residential developments. However,
these estimates are used for determining flows in the MCES interceptors. On a local
design level MCES recommends sizing sanitary sewers for greater than 800 gpad for
non-residential. Typically 1,000 gpad for commercial/business park areas, and 1,500
gpad for industrial/mixed use areas. The following estimated flows per acre were
assumed:
Business Park – 1,000 gpad
Commercial – 1,000 gpad
Corporate Campus – 1,000 gpad
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General Industrial – 1,500 gpad
Industrial/Mixed Use – 1,500 gpad
Waste Management – 1,000 gpad
Future residential development was reviewed with the City Planning Department over the
course of developing the Comprehensive Water System Plan. MCES recommendations
of 75 gpcd were used in conjunction with planning department development projections
and densities. The following estimated flows were assumed:
Urban Residential – 3 units/acre, 3.0 person/unit, 75 gpcd = 675 gpad
Transition Residential – 2 units/acre, 3.0 person/unit, 75 gpcd = 450 gpad
High Density Residential – 12 units/acre, 3.0 person/unit, 75 gpcd = 2,700 gpad
Medium Density Residential – 7 units/acre, 3.0 person/unit, 75 gpcd = 1,575
gpad
Rural Residential – 0.2 units/acre, 3.0 person/unit, 75 gpcd = 45 gpad
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Table 10 Summary of Gross Developable Acres by Sewershed
Summary of Gross Developable Acres by Sewershed
Sewershed
High
Density
Residential
Urban
Residential
Medium
Density
Residential
Business
Park
Trans.
Residential
Rural
Residential Agr. Agr.
Research
Corp.
Campus Downtown
Parks/
Open
Space
Gen.
Industrial
Industrial/
Mixed Use
Neighborhood
Commercial
Public
Institutional
Regional
Commercial
Waste
Manageme
nt
Total
150th 0
Auburn 0
Biscayne 12.7 0.6 13
Business
Parkway 0.0 2.6 216.5 80.5 300
Canada 1.4 0.2 2
Connemara 0.0 0
Danville 0
Lan-O-Ken 36.0 5.6 42
LS 1 0
LS 3 1.2 44.9 3.4 17.5 67
LS 4 0
LS 5 0
LS 6 0
LS 7 0
LS 8 2.0 2
LS 9 0
MWCC08 59.3 1384.7 194.2 163.9 153.5 131.8 238.9 2326
MWCC09 4.7 1.7 68.6 0.0 337.7 19.6 115.9 548
MWCC10 127.4 127
Northwest 0
South Central 7.5 43.2 1030.6 39.6 114.5 1235
Southeast 85.5 1633.9 448.4 422.3 217.6 94.1 91.4 17.4 12.7 3023
Southwest 172.5 10.8 183
Total 145 3369 703 1905 0 0 0 0 508 0 0 603 350 26 0 261 0 7869
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6.2.2 Future Sewershed Flows
The estimated unit wastewater flows previously described was tied to the remaining
developable acres and potential ultimate service area in each sewer shed as shown in
Figures 3-2 and 4-2 to determine the future average future flows shown below in Table
11.
Table 11 Future Wastewater Flows by Sewershed
Future Wastewater Flows by Sewershed
Sewershed
Existing
Avg. Flow
(MGD)
2020 Avg.
Flow
(MGD)
2025 Avg.
Flow
(MGD)
2030 Avg.
Flow
(MGD)
2035 Avg.
Flow
(MGD)
2040 Avg.
Flow
(MGD)
Ultimate
Avg. Flow
(MGD)
150th 0.191 0.191 0.191 0.191 0.191 0.191 0.191
Auburn 0.013 0.013 0.013 0.013 0.013 0.013 0.013
Biscayne 0.079 0.079 0.080 0.081 0.081 0.081 0.081
Business Parkway 0.058 0.058 0.176 0.294 0.294 0.294 0.294
Canada 0.104 0.104 0.105 0.106 0.106 0.106 0.106
Connemara 0.232 0.232 0.232 0.232 0.232 0.232 0.232
Danville 0.101 0.101 0.101 0.101 0.101 0.101 0.101
Lan-O-Ken 0.103 0.103 0.107 0.111 0.111 0.111 0.111
LS 1 0.046 0.046 0.046 0.046 0.046 0.046 0.046
LS 3 0.317 0.317 0.344 0.371 0.371 0.371 0.371
LS 4 0.126 0.126 0.126 0.126 0.126 0.126 0.126
LS 5 0.138 0.138 0.138 0.138 0.138 0.138 0.138
LS 6 0.007 0.007 0.007 0.007 0.007 0.007 0.007
LS 7 0.023 0.023 0.023 0.023 0.023 0.023 0.023
LS 8 0.089 0.089 0.089 0.089 0.089 0.089 0.089
LS 9 0.041 0.041 0.041 0.041 0.041 0.041 0.041
MWCC08 0.061 0.338 1.536 2.734 2.949 3.163 3.163
MWCC09 0.000 0.037 0.614 1.192 1.307 1.422 1.422
MWCC10 0.016 0.016 0.025 0.034 0.034 0.034 0.034
Northwest 0.043 0.043 0.043 0.043 0.043 0.043 0.043
South Central 0.000 0.000 0.359 0.718 1.070 1.422 1.422
Southeast 0.000 0.166 0.743 1.320 1.876 2.432 3.565
Southwest 0.000 0.000 0.027 0.053 0.094 0.135 0.135
Total 1.789 2.268 5.167 8.065 9.343 10.621 11.754
As discussed previously, MCES regional interceptor capacities are planned for based on a
average wastewater flow generation rate of 800 gpad. Therefore, regional wastewater
flow projections are different than the local wastewater flow projections included in
Table 11. Futre regional average flow is show in Table 12 by sewershed and connection
point to MCES facilities. Table 13, immediately following shows the projected future
regional wastewater flows in 10 year increments
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Table 12 Ultimate Regional Wastewater flows by MCES Connection Point
Ultimate Regional Wastewater Flow by MCES Connection Point
MCES Facility Sewershed
Ex. Avg
Flow
(MGD)
Developable
Acres
Future Development
Avg. Flow (MGD)
Ultimate
Avg. Flow
(MGD)
Cumulative Ultimate Avg. Flow
at MCES Connection (MGD)
M641 LS 3 0.317 67 0.054 0.37 0.47
Danville 0.101 0 0.000 0.10
L74 to Blaine Ave. (CR 73)
MWCC08 0.000 756 1.392 1.39
6.38 MWCC09 0.000 357 1.128 1.13
Southeast 0.000 3023 3.565 3.56
MWCC09 0.000 191 0.294 0.29
Blaine Ave. to Akron Ave. South Central 0.000 1235 1.422 1.42 7.80
Akron Ave. (CR 73) to
Biscayne Ave.
Northwest 0.043 0 0.000 0.04
10.16
Lan-O-Ken 0.103 42 0.007 0.11
LS 9 0.041 0 0.000 0.04
Connemara 0.232 0 0.000 0.23
MWCC08 0.000 863 0.913 0.91
MWCC08 0.061 707 0.797 0.86
MWCC10 0.016 127 0.018 0.03
Auburn 0.013 0 0.000 0.01
LS 8 0.089 2 0.000 0.09
LS 7 0.023 0 0.000 0.02
Biscayne Ave. to City
Boundary (M655)
150th 0.191 0 0.000 0.19
11.28
Canada 0.104 2 0.001 0.11
LS 1 0.046 0 0.000 0.05
LS 4 0.126 0 0.000 0.13
LS 5 0.138 0 0.000 0.14
LS 6 0.007 0 0.000 0.01
Southwest 0.000 183 0.135 0.13
Business
Parkway 0.058 300 0.236 0.29
Biscayne 0.079 13 0.003 0.08
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Table 13 Future Regional Wastewater FLow my MCES connection point and 10-year Increment
Future Regional Wastewater Flow by MCES Connection Point and 10-Year Increment
MCES Facility
Cumulative
Existing Avg. Flow
(MGD)
Cumulateive
2020 Avg.
Flow (MGD)
Cumulative
2030 Avg.
Flow (MGD)
Cumulative
2040 Avg.
Flow (MGD)
Cumulative
Ultimate Avg.
Flow (MGD)
Sewershed
Existing
Avg. Flow
(MGD)
2020 Avg.
Flow
(MGD)
2030 Avg.
Flow
(MGD)
2040 Avg.
Flow
(MGD)
Ultimate
Avg. Flow
(MGD)
M641 0.418 0.418 0.472 0.472 0.472 LS 3 0.317 0.317 0.371 0.371 0.371
Danville 0.101 0.101 0.101 0.101 0.101
L74 to Blaine Ave. (CR 73) 0.000 0.460 3.905 5.246 6.379
MWCC08 0.000 0.258 1.392 1.392 1.392
MWCC09 0.000 0.037 0.966 1.128 1.128
Southeast 0.000 0.166 1.320 2.432 3.565
MWCC09 0.000 0.000 0.225 0.294 0.294
Blaine Ave. to Akron Ave. 0.000 0.460 4.622 6.669 7.802 South Central 0.000 0.000 0.718 1.422 1.422
Akron Ave. (CR 73) to Biscayne
Ave. 0.622 1.101 6.560 9.035 10.158
Northwest 0.043 0.043 0.043 0.043 0.043
Lan-O-Ken 0.103 0.103 0.114 0.114 0.111
LS 9 0.041 0.041 0.041 0.041 0.041
Connemara 0.232 0.232 0.232 0.232 0.232
MWCC08 0.000 0.000 0.484 0.913 0.913
MWCC08 0.061 0.080 0.858 0.858 0.858
MWCC10 0.016 0.016 0.040 0.040 0.034
Auburn 0.013 0.013 0.013 0.013 0.013
LS 8 0.089 0.089 0.089 0.089 0.089
LS 7 0.023 0.023 0.023 0.023 0.023
Biscayne Ave. to City Boundary
(M655) 1.371 1.850 7.605 10.161 11.282
150th 0.191 0.191 0.191 0.191 0.191
Canada 0.104 0.104 0.106 0.106 0.106
LS 1 0.046 0.046 0.046 0.046 0.046
LS 4 0.126 0.126 0.126 0.126 0.126
LS 5 0.138 0.138 0.138 0.138 0.138
LS 6 0.007 0.007 0.007 0.007 0.007
Southwest 0.000 0.000 0.053 0.135 0.135
Business
Parkway 0.058 0.058 0.296 0.296 0.294
Biscayne 0.079 0.079 0.081 0.081 0.081
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Future Trunk Sanitary Sewer System
The future trunk sanitary sewer system layout is shown in Figure 6-2. It shows the proposed
trunk sewers, lift stations, force mains, and sewersheds. Using the projected wastewater flows for
each of the sewersheds and sub-sewersheds, design flows were determined for each segment of
trunk sewer to determine sizing requirements.
The sanitary sewer trunk system was divided into pipe lengths with collection points. Each sub-
sewer shed was designated one collection point, and the collection point was assumed to be the
location where the sub-district’s flow entered the pipe network. The collection points were
assumed conservatively and were typically the lowest elevation in the sub-sewer shed at the
greatest distance from the connection point to the trunk sewer.
A SewerCAD model was developed for the future trunk system based on the collection points.
Laterals were extended from the collection points to the trunk mains and were sized based on the
peak wastewater flow generated at the collection point. Trunk mains were appropriately sized
where collection laterals connected to each trunk main.
The sanitary sewer collection system must be capable of handling not only average flows, but
also the anticipated peak flows. These peak flows can be expressed as a variable ratio applied to
average daily flow rates. This variable ratio, called the peak flow factor, has been found to
decrease as average flow increases. The peak flow factors applied in this study are listed in
Appendix 1. These values were obtained from MCES. They are generally considered
conservative, and are widely used for planning in municipalities throughout the twin cities
metropolitan area.
6.3.1 Existing City Sewersheds
The City’s existing service area is located in the southwest area of the City. It was
broken down into sewersheds based on existing lift stations and connection points to
trunk sewers. The sewersheds named for connection points to trunk sewers were named
for streets where the majority of flows would be collected. Some sewersheds are fully
developed in accordance with the 2030 land use plan including Danville, 150th, Canada,
LS 1, LS 4, LS 5, LS 6, LS 7, Auburn, and Biscayne. These sewersheds will not generate
additional future flow unless major redevelopment occurs. The balance of the existing
sewersheds, LS 3, LS 8, LS 9, Business Parkway, Connemara, and Lan-O-Ken, have
developable area remaining.
Wastewater from existing development is collected by sewer mains ranging in size from
8 to 30 inches in diameter. All flows are conveyed to the Rosemount Interceptor, with
the exception of flows from the Danville and LS 3 sewersheds. Wastewater from those
sewersheds flows through MCES flow meter M641 in the southeast corner of the City to
Apple Valley and ultimately the Empire wastewater treatment plant.
The fully developed existing sewersheds will not require future improvements, since
additional future flows will not be generated. Of the existing sewersheds with
developable area remaining, only the Lan-O-Ken will require trunk main extensions.
Connemara, LS 8, LS 3, LS 9, and Business Parkway will require additional collection
laterals only.
The Lan-O-Ken trunk sewer extension was included in the North Central Sanitary Sewer
Study that closely reviewed the Northwest, Lan-O-Ken, MWCC10, and North Central
sewersheds. An 18-inch trunk main would be extended further west and north from the
current endpoint and a 950 gpm lift station would be required to pump flows from the
northern tier of the district and the Northwest sewer shed south to trunk main.
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The northern portion of the Lan-O-Ken sewershed is currently planned as a transitional
residential zone will likely be conveyed north into Eagan’s sanitary sewer. The area has a
potential average flowrate of 0.085 MGD and an estimated peak flow of 0.34 MGD.
Assuming the connection to Eagan is placed a the 10 State Standards minimum pipe
slope, a 8” trunk sewer line would be capable of serving the transitional residential area.
6.3.2 Northwest Sewershed
The Northwest Sewer Shed includes the existing developed rural residential area north of
the existing City service area and west of Robert Trail. There is no existing sanitary
sewer collection system in this developed area and wastewater treatment is accomplished
by ISTSs.
Additional trunk sanitary sewer improvements will be necessary, although it is not likely
this area will be served in the future. Sanitary sewer service to this area was originally
planned for in the North Central Sanitary Sewer Study. A 12-inch trunk main would
convey wastewater to the 950 gpm lift station in the Lan-O-Ken sewer shed. Sewage
would be pumped from the lift station to the Lan-O-Ken trunk main.
6.3.3 MWCC10
The MWCC10 Sewer Shed is bounded by Robert Trail on the west, the Lan-O-Ken and
North Central sewersheds to the north, the MWCC08 sewer shed to the east and 135th
Street to the South. The MWCC10 sewer shed is mostly developed rural and transition
residential, with the exception of some remaining developable urban residential in the
west. There is no existing sanitary sewer collection system in this developed area and
wastewater treatment is accomplished by ISTSs.
Additional trunk sanitary sewer improvements will be necessary to serve this area.
Sanitary sewer service to this area was originally planned for in the MWCC08 Sanitary
Sewer Study. A 12- to 15-inch trunk main would be extended north along Bacardi
Avenue from the Connemara sewer shed to collect flows from the MWCC10 sewer shed.
6.3.4 MWCC08
The MWCC08 sewershed was re-delineated by the City of Rosemount in 2018 and
combines the sewersheds previously known as North Central, Southwest Central, and
Central sewersheds. The new sewershed flows into the Empire Interceptor.
The northern portion of the sewershed is planned as primarily rural residential. Further
south towards CSAH 42 the land use transitions to urban residential with small sections
of commercial and high density residential near the hiway. The souther portions of the
sewershed are primary urban residential with some sections of agricultural research on
the far southern end of the sewershed.
Due to the hilly topography of the northern portion of the sewer shed, an 850 gpm lift
station would be required to collect and pump wastewater south to an 18- to 21-inch
trunk main that would convey flows to the West Akron trunk main. If the rural
residential area in the west were to be served, three small lift stations with capacities of 5
gallons per minute (gpm), 15 gpm, and 25 gpm would be required to pump wastewater to
the 850 gpm lift station in the northern tier of the sewer shed.
Additional trunk sanitary sewer improvements will be necessary to serve future
development as shown in Figure 6-2. The sewer shed is broken up by two lift stations,
one in the north and one in the south. Wastewater from the southern area is collected by
8 to 10-inch mains and then pumped to the northern area by an 850 gpm lift station.
Trunk mains ranging in size from 8 to 18-inches in diameter collect wastewater from the
northern area. The southern lift station would pump sewage to the northern lift station
(2,200 gpm) and it would then be pumped to the Empire Interceptor.
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6.3.5 MWCC09
The MWCCO9 sewershed was also re-delineated by the City of Rosemount in 2018 to
combine what was previously the Southeast Central and the Northeast sewersheds.
sewer shed is bounded by the Rosemount wastewater treatment plant to the south, CR 71
to the west, and Pine Bend Trail on the east and north. It is mostly undeveloped with the
exception of some general industrial in northern portion and Flint Hills Resources. The
existing properties have septic systems, but may be served by the City’s municipal sewer
system in the future. The future land use is exclusively general industrial.
The Rosemount Interceptor flows from west to east through the district and terminates at
the Rosemount wastewater treatment plant along the southern boundary of the sewer
shed. Wastewater is then pumped from the existing Rosemount wastewater treatment
plant to the Empire Interceptor. A trunk main ranging in size from 8 to 15-inches was
constructed in 2007 running north along TH 52 from the existing Rosemount Interceptor
to Flint Hills Resources.
Trunk sewer improvements will be necessary to serve future general industrial
development north of the Rosemount wastewater treatment plant. An 880 gpm lift station
with an 8-inch force main would be required to pump wastewater from the future general
industrial area north of Pine Bend Trail and east of TH 52. Trunk mains ranging in size
from 8 to 21-inch would be required to collect flows from remaining future development
south of Pine Bend Trail and east of TH 52. The Flint Hills Resources trunk sewer is
used to collect flows from some of the future development south of Pine Bend Trail.
6.3.6 South Central Sewershed
The South Central sewer shed is similar to the south portion of MWCC08 in that it is
generally within UMore Park and is bounded by CSAH 42 on the north, 160th Street on
the south, Southwest Central sewer shed on the west, and TH 52 on the east. There is a
small area north of CSAH 42 that would be included in this sewer shed. The future land
uses within the district include business park, regional commercial,and small section of
agricultural research and medium density residential.
There is no existing sanitary sewer collection system in this area. The Empire Interceptor
is mostly force main along the northern border of the sewer shed, being pumped from
east to west.
Additional trunk sanitary sewer improvements will be necessary to serve future
development. The topography provided relief to create a 15 to 30-inch trunk main
flowing from the southern boundary of the district, northeast to the Rosemount
Interceptor in the Central sewer shed. The trunk main connects to the Rosemount
Interceptor just to the west of TH 52, but a crossing of CSAH 42 would be required. A
530 gpm lift station would be required to pump wastewater from an area in the southeast
corner of the sewer shed to the future trunk main.
6.3.7 Southwest Sewershed
The Southwest sewer shed is within UMore Park. It includes the area east of Biscayne
Avenue, west of the Southwest Central sewer shed, south of CSAH 42, and North of
160th Street. It is currently undeveloped and future land use would be almost exclusively
Urban Residential with a small portion of the developed area being planned as
commercial space.
The Rosemount Interceptor flows west to east, then north through the district. The
Empire Interceptor flows to the east along the northern boundary then south along the
eastern boundary of the district.
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Additional trunk sanitary sewer improvements will be necessary to serve future
development. Due to the proximity of both the Rosemount and Empire Interceptors, the
majority of sewers would be collection laterals. A 10-inch diameter main would be
required to collect flows from the largest sub-sewer shed and convey flows to a 470 gpm
lift station that would pump to the Empire Interceptor.
6.3.8 Southeast Sewershed
The Southeast sewer shed is generally located in the southeast corner of the City limits.
It is bounded by the City limits on the east and south, Pine Bend Trail on the north, and
the Northeast and Southeast Central sewersheds to the west. It is currently undeveloped,
however, there are some existing rural residential areas served by ISTSs. Future
development is planned to be largely urban residential, industrial/mixed use, corporate
campus, and business park, but there are smaller areas of commercial, medium density
residential, and high density residential.
There is no existing sanitary sewer collection system or MCES interceptor sewer within
this district.
Additional trunk sanitary sewer improvements will be necessary to serve future
development. Since there is no existing MCES interceptor east of the Rosemount
wastewater treatment plant (MCES L74 Lift Station), a major City interceptor was
required. The topography provided relief for a southeast interceptor flowing from the
eastern border, initially 24-inches in diameter increasing to 36-inches in diameter, then
west and north to a 6,300 gpm lift station located near MCES L74 Lift Station (L74).
The lift station would be required to lift flows a short distance since the existing invert at
L74 is near elevation 829 and the proposed trunk sewer invert would be approximately
800. The southeast interceptor would have to cross CSAH 42 and 140th Street.
The proposed trunk sewer would flow from the southeast to the northwest across land
that is largely owned by Great River Energy. Great River’s development plans are
unknown; however, the future trunk sewer can be routed around the land if it is not
developed. The future trunk sewer is not necessary until development occurs in the
southeast sewer shed, therefore, final routing should be reviewed once development
begins in the southeast sewer shed. In addition, as development begins to occur, the
trunk lift station may not initially be constructed with 6,300 gpm capacity. The lift
station could be constructed in phases with room for capacity expansions as development
increases in the southeast sewer shed. Lift station capacity phasing would be dependent
upon the rate of development at that time.
Other trunk sewer improvements would be required to convey future flows to the major
City interceptor. These improvements are shown in Figure 6-2 and include sanitary
sewers ranging in size from 8 to 18-inches in diameter, and three lift stations. The lift
stations include a 1,400 gpm station in the northeast that would generally serve the
corporate campus area, a 770 gpm station in the southeast to serve urban residential along
the southern City border, and a 130 gpm station in the southwest to serve urban
residential along the southern City border.
7. CAPITAL IMPROVEMENTS PLAN (CIP)
Estimated Cost of Trunk System Improvements
The projected ultimate sanitary sewer trunk system was broken down into improvements
based on sewersheds and development projection time frames. The overall cost
associated with trunk system components over the next 23 years is estimated to be
approximately $41,687,358 in 2017 dollars and ultimately $6,169,222 more. Table 14
summarizes the trunk improvement costs necessary for each district. Detailed cost
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City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 22
estimates for each district are available in Appendix 2. Furthermore, construction
schedules for trunk facilities in each sewer shed are included Appendix 3.
Future improvement costs were based on 2017 construction prices, including a 10%
construction contingency, and including 30% overhead (i.e., legal, engineering, and
administrative). Street and easement costs and other miscellaneous costs that may be
related to final construction are not included.
Table 14 Capital Improvement Plan by Sewershed
1) Costs are for budgeting purposes only, and are subject to change as projects are
studied, designed, and constructed.
2) Costs are estimated based on 2017 construction costs.
3) Land acquisition costs are not included.
Future Trunk System Funding
7.2.1 General
Future trunk sewer improvements are funded through the City’s Core Fund. As
properties develop, initial costs are paid by the core fund. Then, the core fund is
reimbursed by trunk area assessments and individual connection charges. The current
available balance in the core fund is approximately $5,000,000.00.
Trunk Area Assessments are collected when a developer applies for a plat/subdivision
agreement. Any fees not collected with the plat/subdivision agreement are collected as a
connection charge prior to system connection. The assessment is calculated based on the
entire parcel area to be developed. The current Trunk Area Assessment is $1,075 per
acre.
The SAC fee, or connection charge, is collected when a new or existing property applies
to connect to City sanitary sewer. The SAC charge is $1,200 per SAC unit, and is
equivalent to 274 gallons per day (gpd). A single family residence is considered one
SAC unit, but other types of buildings pay a prorated SAC fee relative to their estimated
sanitary sewer flows.
7.2.2 Future Connection Fees and Trunk Area Growth
Future connection growth dictates the expected future income of the core fund based on
Trunk Area Assessments and SAC collected from development. Table 15 below shows
the projected development fees based on the growth assumptions assumed in Sections 3
and 4.
Capital Improvement Plan by Sewershed
District 2020 2030 2040 Ultimate Total
MWCC09 $0 $2,727,922 $0 $1,004,202 $3,732,124
Southeast $0 $5,415,200 $13,585,978 $0 $19,001,178
South Central $0 $1,356,162 $353,930 $3,556,893 $5,266,985
MWCC08 $1,944,498 $5,757,143 $0 $7,846,927 $15,548,568
Southwest $0 $0 $0 $1,078,451 $1,078,451
Lan-O-Ken $0 $969,620 $0 $0 $969,620
Northwest $0 $0 $0 $413,700 $413,700
MWCC10 $0 $456,680 $0 $0 $456,680
Total $1,944,498 $16,682,727 $13,939,908 $13,900,173 $46,467,306
Prepared by: Bolton & Menk, Inc. CAPITAL IMPROVEMENTS PLAN (CIP)
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 23
Future developable area, discussed in 3.2 and shown in Figure 3-2, was correlated to the
projected land use phasing discussed in 4.3 and shown in Figure 4-2 to project the
development timing of remaining developable area broken down by land use.
The number of SAC units expected to develop were based on the estimated unit
wastewater flows discussed in 6.2.1. SAC units for residential land uses were based on
the estimated units for each type. However, SAC units for non-residential land uses were
prorated based on the assumed unit wastewater flow. For example, one acre of business
park development was assumed to generate 1,000 gpd, which was divided by the SAC
unit flow equivalent (274 gpd), to determine that each acre of business park development
would generate 3.6 SAC units of wastewater flow.
7.2.3 Core Fund Rate Analysis
To accurately reflect future infrastructure expenses, the Capital Improvement Plan
estimated costs for each design interval, but not increased for inflation. It was assumed
that rates would be increased at a rate similar to inflation. Full development was assumed
to occur in 2037. Table 15 shows existing rates’ impact on the balance of the core fund.
Existing rates appear to be adequate to fund future improvements, assuming they are
increased at a rate similar to inflation. The fund balance is estimated to decrease from
approximately $5,000,000 to $145,000 once the City is fully developed. Since the City
funds the initial infrastructure cost and is then reimbursed by development fees, it is
recommended to review rates on a regular basis. Some debt financing may be required to
fund future improvements depending upon the cost of individual sewer improvement
projects.
Table 7-2
Sewer Core Fund Balance Projection
Table 15 Core Fund Assume Gross Acres Development
Core Fund Assuming Gross Acres Development1
2018-2020 2020-2030 2030-2040 2040-Ultimate
Total Area Developed 726 5,429 2,493 1,398
Trunk Area Charge Rate per Acre $1,075 $1,075 $1,075 $1,075
SAC Fee Rate per Unit $1,200 $1,200 $1,200 $1,200
Beginning Year Balance $5,000,000 $6,464,835 $12,895,761 $8,944,002
Development Costs (CIP) $1,944,498 $16,682,727 $13,939,908 $13,900,173
Balance after Expenses $3,055,502
-
$10,217,892 -$1,044,147 -$4,956,171
Total SAC Fees $2,628,452 $17,277,390 $7,307,861 $3,598,261
Total Revenues $3,409,333 $23,113,653 $9,988,149 $5,100,877
Balance after Revenues (Year End) $6,464,835 $12,895,761 $8,944,002 $144,706
Balance change $1,464,835 $6,430,926 -$3,951,759 -$8,799,296
% change 29% 99% -31% -98%
1 Assumes SAC charged to newly connected properties served by ISTS
Prepared by: Bolton & Menk, Inc. CAPITAL IMPROVEMENTS PLAN (CIP)
City of Farmington - Comprehensive Sewer Plan ǀ [T18114157] Page 25
Appendix 1: Figures
Map Document: H:\ROSEMNT_CI_MN\T18116417\GIS\ESRI\Figures\GIS\3_1 LandUse.mxd Date Saved: 8/21/2018 10:23:16 AMComprehensive S anitary S ewer System Plan
City of Ros emount August, 2018Figure 3-1 Land Use Plan
Legend
Parcel Boundary
MUSA Boundary
2030
2040
2050
La nd U se
Agricultural
Agricultral Research
Business Park
Cor porate Campus
Downtown
Gener al Industrial
High Density Residential
Industrial /Mixed Use
Medium Density Residential
Nei ghborhood Commercial
Public/Infrastructur e
Parks & Opens Space
Regional Commercial
Rur al Residenti al
Transitional Residential
Urban Residential
Waste Management
0 1,5 00Feet
So urce:
!I
Map Document: H:\ROSEMNT_CI_MN\T18116417\GIS\ESRI\Figures\GIS\3_3 Gross Developable.mxd Date Saved: 8/21/2018 10:36:23 AMComprehensive S anitary S ewer System Plan
City of Ros emount August, 2018Figure 3-2 Gross Developable Land
Legend
Undeveloped
Developed
La nd U se
Agricultural
Agricultral Research
Business Park
Cor porate Campus
Downtown
Gener al Industrial
High Density Residential
Industrial /Mixed Use
Medium Density Residential
Nei ghborhood Commercial
Public/Infrastructur e
Parks & Opens Space
Regional Commercial
Rur al Residenti al
Transitional Residential
Urban Residential
Waste Management
0 1,5 00Feet
So urce:
!I
Map Document: H:\ROSEMNT_CI_MN\T18116417\GIS\ESRI\Figures\GIS\4_2 Potential Ult Service Area.mxd Date Saved: 8/21/2018 2:31:40 PMComprehensive S anitary S ewer System Plan
City of Ros emount August, 2018Figure 4-2 Potential Ultimate Service Area
Legend
2020 R esi dential
2020 N on-R esidential
2030 R esi dential
2030 N on-R esidential
2040 R esi dential
2040 N on-R esidential
2050 R esi dential
2050 N on-R esidential
0 1,5 00Feet
So urce:
!I