Sanitary Sewer System Plan - PDF by ujp66840


									Sanitary Sewer System Plan
The construction and maintenance of the sanitary sewer system is one of the more
costly services provided by the City and the Metropolitan Council. It is crucial
that the City plan for the continued need for sanitary sewer service and
maintenance of the system in the most responsible manner possible.

The purpose of this portion of the plan is to provide policies and management
practices in the event of land use changes and redevelopment activities that have
the potential to impact the City’s ability to provide reliable and cost-effective
sanitary sewer service to its residents and businesses.

The most significant amount of redevelopment and land use changes occurred and
will continue to occur along the I-394 corridor. The expansion of the Ridgedale
regional center, the redevelopment of the north side of I-394. To anticipate the
impact to the sanitary sewer system, an analysis of existing and projected sewage
flows is needed for the general sewer districts in the City.

Sanitary Sewer Plan Components
This portion of the plan has been prepared in accordance with the requirements of
the Metropolitan Land Planning Act, amended in 1995, and the content
requirements for the sewer element included in the Local Planning Handbook
prepared by the Metropolitan Council in 1996. The plan contains detailed local
system analysis to determine existing and future operational requirements, the
level of maintenance requirements, and future capital needs. Goals and policies
have been included to guide future decisions regarding the impacts and
opportunities to the operation, preservation, and overall maintenance of the sewer
system. The plan concludes with a set of recommendations that are designed to
reinforce the long-term viability of the sanitary sewer system.

Relationship to Comprehensive Plan Elements

The sanitary sewer system of a community is closely tied to its Comprehensive
Plan and official controls. The land use category identified for specific properties
in the Comprehensive Plan allows uses that generate typical sewer flows. The
intensity of the use as regulated by the zoning ordinance defines the daily sewer

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                             Sanitary Sewer System Plan

flow rate. The rate of sewage flow is utilized to determine the appropriate
capacity and facilities needed for the sanitary sewer system.

The sanitary sewer element has been developed utilizing the land uses identified
in the Land Use Plan portion of the Comprehensive Plan. Additionally, future
development information for properties that are scheduled to undergo a land use
change were obtained from the Future Land Use Plan map.

Relationship to Surface Water Plan

The City of Minnetonka has prepared a Surface Water Management Plan that is
consistent with the goals of the local watershed district plans. This plan describes
the manner in which the City has and will control development to meet surface
water goals and policies. In addition, it describes the storm water facilities
available or needed to accommodate planned levels of growth and storm water
control. The sanitary sewer portion of the Comprehensive Plan is related to the
Surface Water Management Plan because of the need to ensure that Aclean
water@ is entering the Minnesota River from surface water sources and system
discharges in Minnetonka.

The City is divided into four major watersheds which are regulated by the
Minnehaha Creek, Nine Mile Creek, and Riley-Purgatory Creek Watershed
Districts. There are numerous sub-watersheds within the larger watershed
districts. Ultimately, all surface and storm water sewer systems, and the
discharges from the sanitary sewer system via the Blue Lake Treatment Plant,
outlet directly to the Minnesota River. The surface and storm water sewer systems
consist of pipes, lift stations, ponding areas, streams, and lakes. The sanitary
sewer system has always been constructed and managed separately from the
storm water system and there are no known physical connections between the
sanitary and storm water systems.

Generally, the sanitary sewer system within the City follows a topographic-based
approach to the trunk sewers similar to the storm water sewers. The topographic
divisions allow for a gravity-based sewer system which reduces overall costs and
energy consumption. Lift stations are utilized in instances to serve isolated
neighborhoods that are characterized by unique topographic conditions.

In addition to the above, the City adopted the Metropolitan Council’s 1992
Interim Strategy to Reduce Nonpoint Source Pollution to all Metropolitan Water
Bodies in 1993 to further regulate development activity.

April 1999                            7-2                            City of Minnetonka
                          Sanitary Sewer System Plan

Existing Sanitary Sewer System
Previous Planning Efforts

The first comprehensive study to provide municipal sanitary sewer service in the
City was prepared in 1964. Titled Sanitary Sewer Collection and Disposal, the
study presented a trunk sewer system for the City. Due to the growing subregional
need for sanitary sewer service, the City (then Village) was instrumental in the
formation of the “Southwest Sanitary Sewer District” (SSSD) in 1968 which
originally included Minnetonka, Eden Prairie, Deephaven, Eagle Creek and Prior
Lake. The SSSD constructed several interceptor sewers and a treatment plant
located at Blue Lake in northern Scott County. During the construction of these
facilities, Chanhassen, Shorewood, Greenwood and Tonka Bay joined the SSSD.

In 1970, the state legislature passed the “Metropolitan Sewage Act” resulting in
the formation of the Metropolitan Sewer Board to assume the functions of the
SSSD in the continuation of the construction program. In 1970, the City with a
population of 35,500 was unsewered except for a small area in the northeast part
of the City. This portion of the City was served by the St. Louis Park sanitary
sewer system. In anticipation of the completion of the Blue Lake treatment
facility in 1971, a report titled Restudy of Trunk Sanitary Sewer System for
Minnetonka was completed in 1970.

As part of the development of the 1981 Comprehensive Plan, the Minnetonka
Sanitary Sewer Policy Plan was prepared. This plan identified that the sewer
system was capable of handling the flows being experienced at that time, but that
some trunk sewer improvements would be necessary to address flows projected
for ultimate development. All of the necessary system improvements identified in
that policy plan have been completed. However, continued development pressure
has resulted in updates to zoning and the future land use plan, resulting in the
possibility of wastewater flows increasing to the point of exceeding existing
sewer system capacities.

Metropolitan Interceptors and Treatment Plant

The collection and treatment of sanitary wastewater are primary functions of the
City of Minnetonka and the Metropolitan Council. The Minnetonka collection
system flows in a southerly direction and access three main MCES interceptor
sewers. The MCES interceptors that carry Minnetonka wastewater eventually
merge with the Chaska interceptor in the central portion of Eden Prairie which
carries effluent to the Blue Lake wastewater treatment facility in Shakopee.

The MCES interceptors that carry Minnetonka wastewater are identified as
Interceptor Nos. 6801, 7016, 7018-2, 7073, 7073-1, and 7118 as depicted on

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                           Sanitary Sewer System Plan

Figure 7-1. Interceptor No. 7018-2 accommodates the north Lake Minnetonka
communities of Wayzata, Long Lake, portions of Orono, Greenfield,
Independence, Maple Plain, Minnetonka Beach, Minnetrista, Mound, and Spring
Park. It enters Minnetonka at the northwest corner of the City at the TH 101
bridge over Grays Bay and merges with another interceptor to become Interceptor
No. 7073 at the west central portion of Minnetonka near the intersection of
Woodlawn Avenue and Minnetonka Boulevard. The diameter of the portion of
the interceptor is 36".

The western portion of Interceptor No. 7073 serves the western Lake Minnetonka
communities of Deephaven, Greenwood and portions of Excelsior. In
Minnetonka, this interceptor accommodates municipal trunk connections in the
western portion of the City as depicted on Figure 7-1 and ranges in size from
42"to 60" in diameter.

Interceptor No. 7016 enters Minnetonka at its southwest corner and accepts
wastewater from the south shore Lake Minnetonka communities and a small area
of southwest Minnetonka. The diameter of this interceptor in Minnetonka ranges
from 30" to 36" in size. It merges with Interceptor No. 7073 near Creek Ridge
Trail and Scenic Heights Drive. Wastewater flows from the Minnetonka trunk
sewers in the Riley-Purgatory watershed exit the City via this interceptor along
the Purgatory Creek floodplain immediately east of the Scenic Heights Drive
intersection with Co. Rd. 62.

Wastewater from the south central area of Minnetonka enters MCES Interceptor
No. 7118 in Eden Prairie near the entrance to the Glen Lake Home School on Co.
Rd. 62. This area represents the western portion of the Nine Mile Creek
watershed in Minnetonka.

Wastewater from municipal trunk lines in the remaining portion of the City enter
MCES Interceptor No. 6801 in Eden Prairie near the Rowland Road/Co. Rd. 62
underpass. The service area for this intersection is large and represents
approximately three-fourths of the area of the City. The MCES interceptor service
area accommodates wastewater in the Bassett Creek, Minnehaha Creek and
eastern Nine Mile Creek watersheds in the City.

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                                Sanitary Sewer System Plan

Metropolitan Service Districts and Flows

There are four metered interceptor service areas and one unmetered service area
within the City as depicted on Figure 7-1. The service areas are determined by the
geographic area served by the municipal trunk sewer that enters a particular
metropolitan interceptor.

Wastewater from Minnetonka properties flows through the three metropolitan
interceptors and is measured at MCES metering stations located along the
southern boundary of the City. The flows are metered to determine the allocation
of annual operations and maintenance costs of the metropolitan system per
community. The three metering stations that measure Minnetonka flows are
labeled as M412, M411 and M410 on Figure 7-1.

Meters are located along the western Minnetonka border to determine wastewater
flows entering the City from adjacent communities. These meters gauge flows
from neighboring cities including Deephaven, Eden Prairie, Shorewood, and
Wayzata. Wastewater from several Minnetonka neighborhoods at the extreme
western edge of the City are not metered and estimates of flow rates from these
areas are prepared by MCES staff. The unmetered calculation also includes the
flow from sewer connections in homes that have private wells and MCES septage
disposal site no. 7. This site will be relocated from Minnetonka Boulevard to
Clear Springs Road in summer 1998.

Inter-community flow entering Minnetonka are estimated by MCES and deducted
from total metered sewage flow rates to determine total Minnetonka wastewater
production. Table 7 -1 depicts the wastewater flows at the three metering stations
at the south boundary of the City.

Table 7 -1
Metropolitan Service Area Flows (MGY)

       Service Area      1995                  1996          1997
     M410                1185.7                1832.6        1972.2
     M411                192.2                 193.8         204.1
     M412                498.18*               536.7         569.8
     Unmetered           -.44                  -.48          -.64
     Total               2545.56               2562.62       2745.46

    *estimated by MCES

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                             Sanitary Sewer System Plan

Description of Municipal System

The sanitary sewer collection system is available to all properties within the City.
Almost 100 percent of residences and businesses are connected to the sanitary
sewer collection network. There are several residences within the City that still
rely upon functioning on-site disposal systems although municipal sewer is
available to the property. It is anticipated that the on-site septic systems will be
phased out in the next several years.

System Characteristics

Since the late 1960's, the City has sequentially served existing and new
development with municipal sanitary sewer service. The sewered population
represents nearly 100 percent of the total population as depicted on Table 7 -2

Table 7 -2
Sewer Connection Characteristics
       Year     Population       Sewered           Total           On-Site
                                Population      Connections        Systems

      1990    48,700            48,652         14,675             16
     1991     49,000            48,950         14,895             16
     1992     48,658            48,613         15,037             13
     1993     49,000            48,960         15,107             11
     1994     49,266            49,230         15,212             10
     1995     50,569            50,380         15,099             10
     1996     51,000            50,970         15,474             10
     1997     51,250            51,220         15,622             10

Since 1990, the number of on-site systems has steadily declined as the result of
further development of large parcels.

The majority of sewer connections in the City are residential as depicted on Table
7 -3. Each single detached family home is required to have an individual sewer
connection to the municipal system.

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                             Sanitary Sewer System Plan

Table 7-3

Sewer Connection Characteristics

 Year        Single          Multiple        Institutional   Commercial       Total
             Family          Family                          /Industrial
 1990        13,678              185              55              472         14,675
 1991        13,905              190              58              522         14,895
 1992        14,241              206              57              533         15,307
 1993        14,390              181              54              482         15,107
 1994        14,489              183              53              487         15,212
 1995        14,667              184              55              493         15,399
 1996        14,715              196              55              508         15,474
 1997        14,827              249              58              488         15,622

The sanitary sewer system in the City is comprised of 253.24 miles of trunk and
lateral sewer pipe. The majority of the system is gravity based but due to the
rolling topography in the City, a total of 35 public lift stations are required in
certain neighborhoods.

Lift Stations

The sanitary sewer system has been designed to rely on gravity flow to the extent
possible. Therefore, most of the trunk sewer system is placed within the lowest
areas of the City and generally follow the drainageways of the four watersheds.
However, because of the hilly nature of the City, lift stations are required in
numerous areas to pump wastewater to higher elevations to enable it to flow
downhill. The wastewater collection system includes 34 active lift stations
depicted on Table 7 -4 that are designed to pump sewage to forcemains or trunks
at higher elevations.

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                                 Sanitary Sewer System Plan

Table 7-4
Lift Station Characteristics

     No           Name              Pumps        No.          Name           Pumps
      1        Acorn Ridge             2         18    Minnetonka Blvd.         2
      2      Bantas Point Rd.          2         19     Moorland Road           2
      3       Brightwood Dr.           2         20       North Str..           2
      4         Burchlane              6         21           Opus              2
      5        Caribou Drive           2         22       Pine Lane             2
      6        Crosby Road             2         23    Powderhorn Terr.         2
      7         Day Place              2         24      Ringer Road            2
      8        Dickson Road            2         25    Sherwood Forest          2
      9      Fairchild Avenue          2         26     Sparrow Road            2
     10        Fetterly Road           2         27    Tonkawood Court          2
     11         Ford Road              2         28       Waymouth              2
     12       Gaywood Drive            2         29    West 34th Street         2
     13         Glen Lake              2         30       Westwood              2
     14       Lakeshore Ave.           2         31     Whitegate Lane          2
     15      MacKenzie Pt. Rd.         2         32     Williston Road          3
     16            Main                4         33    Windridge Circle         2
     17         Minnetoga              2         34       Woodgate              2

Three lift stations have been abandoned as a result of trunk sewer improvements.
The majority of the lift stations are located on the north side of Highway 7 as
depicted on Figure 7-2.

The City of Wayzata owns one lift station within the City of Minnetonka and is
located on Co. Rd. 15 at Glen Haven Road. This lift station accommodates
wastewater from the Wayzata Central Middle School campus, which flows
through Minnetonka to this lift station. Additionally, there is a privately owned
lift station that is on the Cargill headquarters property. Numerous homes are
equipped with private sewage lift pumps because the individual homesite

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                            Sanitary Sewer System Plan

elevations are lower than the municipal sewer. The homeowner is responsible for
the ownership and maintenance of individual house pumps.

Estimated Municipal Sanitary Sewer Flows

The municipal flows are estimated in a different manner than the MCES flows
because typically, cities do not meter individual sewer flows from properties. The
sewer flows are calculated from the fourth quarter water use records, which is a
period of time when outdoor water use does not occur. The flows are substantially
lower than those calculated by the MCES because of the method of calculation,
and the lack of infiltration and inflow into the sewer pipes from other sources.

The municipal sanitary sewer flows are grouped into residential and commercial/
industrial categories. The residential category includes all types of residential
units. The institutional category includes government uses, religious institutions
and other similar public uses. The commercial and industrial categories are
combined, and include all private businesses in the City. Table 7 -5 depicts the
estimated annual sewer flow from 1992 to 1997.

Table 7-5
Sanitary Sewer Flow Summary (MGY)

 Year        Residential   Institutional      Commercial/        Total
 1990           1382           59.1              596.5           2037.6
 1991          1177.4          56.2              599.6           1833.2
 1992          1148.3          55.7              562.3           1673.6
 1993          1154.7          54.3              587.6           1796.6
 1994          1192.6          52.5              610.7           1855.8
 1995          1194.7          52.5              615.8           1863.0
 1996          1022.3          41.8              472.0           1536.1
 1997          1042.5          52.3              575.0           1669.8

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                            Sanitary Sewer System Plan

The trend of estimated sewer flows indicate a general decrease over the past eight

High Flow Generators

High flow generators are those that are defined as producing more than 50,000
gallons per day of effluent. The water use records of commercial customers from
April 1997 to March 1998 were analyzed to determine those with sewage flows of
over 50,000 gallons per day. Typically, industrial sewage flows are slightly higher
than the amount of water consumed. Table 7 -6 depicts those that were billed for
more than 50,000 gallons of water per day on a daily basis or exceeded this
number for a period of time during the past year.

Table 7-6
High Flow Producers

 Name               Address                        Average Daily Flows
 Advance Circuits   15102 Minnetonka Boulevard           136,315 gpd
 Advanced Flex      15115 Minnetonka Boulevard           41,244 gpd
 Cargill            15407 McGinty Road                   46,836 gpd
 Culligan           6030 Culligan Way                    191,389 gpd
 Holiday Circuits   11120 Bren Road West                 209,740 gpd
 Holiday Circuits   111256 Bren Road West                38,660 gpd
 Marriott Inn       5801 Opus Parkway                    33,022 gpd
 Osmonics           5951 Clearwater Drive                114,312 gpd

Intercommunity Flows

There are several areas in neighboring communities adjacent to the municipal
boundaries where sewer facilities are provided by Minnetonka. First, there are
three neighborhoods in Plymouth that are served by the Minnetonka trunk system.
These neighborhoods include the Wayzata Central Middle School campus,
Carlson Center/Kingsview Drive area, and residences to the west of Wayzata East
Middle School on Ridgemount Avenue. Additionally, the Minnetonka municipal
sewer system provides service to residences adjacent to Ford Road in St. Louis
Park, several businesses in the Eden Prairie portion of Opus 2, several residences
in Hopkins and the Groveland Assembly grounds area in Woodland.

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                            Sanitary Sewer System Plan

Additionally, there are over 150 Minnetonka residences that are served by sewer
systems of adjacent communities due to topographic and service conditions. One
business and 100 residences are served by the Wayzata system, 33 residences are
served by Deephaven, 29 by St, Louis Park, one by Plymouth and two by the
Hopkins system. The intercommunity connections are allowed by City resolutions
or joint powers agreements, which dictate charges for services and other relevant

National Pollutant Discharge Elimination System

The National Pollutant Discharge Elimination System (NPDES) permits regulate
the manner and performance of wastewater discharges to surface waters. The
standards for the permits are established to protect surface and groundwater
quality. The permits are issued by the Minnesota Pollution Control Agency
(MPCA) to various industrial and governmental users that produce wastewater
discharges. The following NPDES surface water discharge permits are active
within the City of Minnetonka:

Minnetonka/Ridgedale Water BSTR (MN0060828): This facility discharges water
directly into a storm sewer system or surface water into Crane Lake.

Northern Telecom Inc. (MN0053376): This permit regulates the non-contact
cooling and process water discharge into a storm sewer system which eventually
discharges to Nine Mile Creek.

Osmonics Inc. (MNG255049): Osmonics produces water purification products for
a variety of international industries. This permit regulates the non-contact cooling
water discharge into the Nine Mile Creek watershed area.

The lift stations within the City no longer require NPDES permits according to
the MPCA staff. All permits in the City were terminated by the MPCA in 1977 as
part of an effort to streamline the entire NPDES permitting process. The MPCA
requires that the lift station bypasses be secured and that they be notified in the
event that the bypasses need to be utilized. In Minnetonka, the bypasses have
never been utilized.

There are several other businesses that are subject to NPDES permits in the City
of Minnetonka. These permits are issued in accordance with the amendments to
the Clean Water Act and apply to categorical industrial businesses that discharge
to storm water facilities in the City. The industrial businesses must adopt a
pollution prevention plan and employ Best Management Practice techniques at
the point of discharge.

Lastly, NPDES permits and State Disposal System (SDS) permits are issued for
projects that are under construction and runoff from the site enters storm water or

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                              Sanitary Sewer System Plan

surface water facilities. Permits issued for these projects extend for the life of the
construction project and stipulate that Best Management Practices techniques be

On-Site Systems

In 1997, approximately 10 properties continued to utilize individual on-site
disposal systems. The City has been phasing out the on-site systems with the
installation of municipal sewer and water facilities. There are several large
properties remaining in the City that rely on on-site septic systems. It is expected
that these properties will undergo development within the next ten years and that
all on-site systems will be eliminated.

Sanitary Sewer System Regulations,
Ordinances and Management Practices
The City has adopted a number of practices that are aimed at protecting the
quality of water resources within Minnetonka and the integrity of the sanitary
sewer system. These practices are crucial to the future performance and
investment required by the utility system because they represent the manner in
which this and previous sanitary sewer plans are implemented. This section
describes the regulations that the City has previously adopted.

Sanitary Sewer Regulations

The water and sewer utility ordinance requires that “properties where cesspools or
septic tanks have been in existence prior to construction of a sanitary sewer shall
connect with the public sanitary sewer when ... repairs are needed or within two
years of service availability, whichever occurs first.” Further, the ordinance
prescribes the design and manner in which individual connections and use of
public sewers are to be made. Generally, uses that threaten the integrity of the
sewer system or the capabilities of the Blue Lake treatment facilities, as
prescribed by state and federal laws, are prohibited.

The sanitary sewer regulations also limit the amount of inflow into the sanitary
sewer system. The ordinance prohibits the flows of “rain water from roofs, yards,
lawns, streets, ground water,” etc. and polluted drainage, into any public sanitary

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                             Sanitary Sewer System Plan

Development Regulations

The City zoning regulations determine the specific use and development intensity
of individual parcels in the community. The use and development intensity result
in typical sewer flow calculations that are utilized to “size” the utility systems.
Development and use assumptions based upon reasonable application of the
zoning regulations are critical for future utility planning purposes. As part of
specific project review, a portion of the zoning ordinance requires that utilities be
adequate to accommodate the use and development intensity of the proposed

The City subdivision ordinance requires that property to be developed be served
by the municipal sanitary sewer system. Further, all new sanitary sewer required
for development must be constructed or construction contracted by the City
according to plans approved by the City Engineer.

Wastewater Assessments and Charges

The construction of the municipal and metropolitan sanitary sewer systems and
their on-going operations are financed in several ways. First, a Service
Availability Charge (SAC) is allocated to each parcel by the Metropolitan
Council for use of the regional treatment facilities and interceptor sewers. The
SAC revenue is utilized for reserved capacity for future customers of the regional
system. The City collects the SAC charges at the time of building permit issuance
for the Metropolitan Council.

The construction of the municipal system is paid by assessments to properties
benefitted by the provision of sanitary sewer service. On-going operations and
maintenance costs of the municipal and regional system are financed by customer
charges that are paid on a quarterly basis. Sewer charges are based upon the total
community flow calculated by MCES and the customer category, i.e. residential.
A Strength Charge set by MCES is also applied to industrial users dependent
upon effluent characteristics. In 1998, the sewer charge was $1.70 per 1,000
gallons of water used per property plus the Strength Charge, if industrial.

On-Site System Regulations

The City’s existing regulations for individual on-site disposal systems relate to
connections to the sanitary sewer collection system and the installation of on-site
disposal systems. The existing on-site systems must remain in compliance with
the City on-site septic tank provisions of the water and sewer utilities ordinance
(Section 1000) and the State Division of Health regulations. The Community
Development Department is responsible for coordination and enforcement of
these ordinances.

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                             Sanitary Sewer System Plan

Section 1000.15 of the utilities ordinance provides regulatory procedures for
connections to the public sanitary sewer system and regulatory standards for
existing individual on-site disposal systems. MPCA requires inspections of
individual septic tanks every three years. The City will rely on Hennepin County
to do these inspections.

Maintenance Activities and Practices

The Minnetonka Operations and Maintenance Department is responsible for all
maintenance activities associated with the sanitary sewer system. Preventative
maintenance is conducted by the department on a regular basis and consists of
pipeline cleaning and chemical treatment to control tree root intrusion; lift station
maintenance monitoring and inspection; manhole repairs and rehabilitation; sewer
television, and customer service on a 24 hour, seven day per week basis. The
maintenance frequency is based upon inspection and historical data.

Inflow, Infiltration and Blockage

Basic problems that can affect the operation of a sewer collection system include
infiltration, inflow and blockages. Infiltration and inflow (I/I) is the amount of
clear water entering the collection system. Infiltration is the contribution of flow
that is primarily attributable to high groundwater levels, while inflow is attributed
to increased surface water amounts. It is important that I/I flows be kept to a
minimum to maintain pipe capacity and preserve treatment plant capacity.

The Metropolitan Council has established an I/I goal for a number of
communities in the west metropolitan area including Minnetonka. The I/I goal
that has been established for the City is that the ratio of maximum monthly MCES
sewage flows to minimum monthly sewage should not exceed 1.40. Since 1995,
the high flow months have been August, September and July, respectively. The
low flow months since 1995 have been February and March. Table 7-7 depicts the
ratio of high flow and low flow months since 1995.

In 1995 and 1997, the City remained below the ratio established by the
Metropolitan Council. The City has proactively initiated efforts to reduce I/I in
the sewer system by flooding storm sewers while sanitary mains are televised,
replacing manhole castings and coverings, and eliminating sump pump
connections to the sanitary sewer system.

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                             Sanitary Sewer System Plan

Table 7-7
Ratio of High Flow Months to Low Flow Months (Million Gallons)
                            1995              1996              1997
 Min. Flow Month            192.8             177.0             193.4
 Max. Flow Month            221.2             249.2             268.0
 Min./Max. Flow              1.15             1.41              1.38

Sewer pipe blockage does not allow for the regular flow of sewage. The most
common source of sewer blockages results from tree root obstructions. In
Minnetonka, the possibility of solids settling out and collecting within the
sanitary sewer collection system exists as a result of sewer lines flowing at less
than design capacity. This characteristic of the system could result in blockages.

Goals, Policies and Strategies for Municipal
The City of Minnetonka has established goals and procedures that govern the
capacity and operation of the municipal sanitary sewer system. Additionally,
goals have been adopted that establish the relationship of the city’s system to
regional interceptor and treatment plant facilities. This section of the plan
describes the City’s policies regarding the relationship of the sanitary sewer
system to metropolitan facilities, planning and development activities, municipal
investments, operations and environmental conditions.

Sanitary Sewer System Goals

The City has established a coordinated program towards water quality
management with the ultimate goal of maintaining unpolluted surface and
subsurface waters. The sanitary sewer component of the program is based upon
the following two goals:

 • To provide high quality sanitary sewer service to the residents and businesses
   of Minnetonka in the most economical manner possible.

 • To provide sanitary sewer service that meets the requirements of the 2020
   population and employment forecasts of the City.

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                            Sanitary Sewer System Plan

Relationship to Metropolitan System

The City of Minnetonka recognizes the importance of a coordinated regional
collection and treatment system. The continued investment and maintenance of
the system is of prime importance to the City as well as the region. Likewise,
anticipating growth and redevelopment to ensure future interceptor and treatment
plant capacity is a major goal of the City.


 • The City will take all measures necessary to protect the capacity of the
     interceptor sewers that serve Minnetonka.

 • The City will work with MCES staff to monitor the metered flows from the
     Minnetonka system.

Inflow and Infiltration

The presence of inflow and infiltration can restrict the capacity of sewer pipes and
the treatment facility. The City believes that the elimination of all inflow and
infiltration from the City system and ultimately, the MCES system is more cost
effective than adding additional capacities to sewage facilities.


 • The City will continually monitor the sanitary sewer system to identify points
   of inflow and infiltration.

 • The City will continue to eliminate points of inflow and infiltration to the
   sanitary sewer system on public property, and require the elimination of
   inflow and infiltration on private property.

The City will strive to limit the ratio of maximum monthly MCES sewage flows
to minimum monthly sewage to 1.40.

Relationship to Planning and Land Use Activities

Ideally, the size and capability of a municipality’s sanitary sewer and water
system should accommodate planned future growth and development. As a city
grows, overall reliance on private facilities should diminish as it becomes more
economically and environmentally feasible to provide centralized services. It is
equally important to ensure that land uses and development intensity do not
threaten the long term viability of the system.

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                            Sanitary Sewer System Plan


 • Design trunk sewer expansions in relation to the proposed land use
   intensities outlined in the Land Use Element of the Comprehensive Plan.

 • Provide municipal sanitary sewer service whenever practical to all existing
   buildings that rely on on-site disposal systems and future development.

 • Provisions for sufficient sewer system capacity must be made to serve the
   intensity of new development and redevelopment before final development
   approvals are granted by the City.

 • Periodically review and evaluate the sewer collection system, MCES
   treatment plant capacity, and the accuracy of metered flow data provided by
   MCES in relation to the continued community growth and development.

 • A determination of who is responsible for the payment of reconstruction of
   sewer facilities will be made if insufficient capacity is available to serve the
   intensity of new development or redevelopment provided the proposed
   development is approved by the City.

Municipal Investments

The installation, maintenance and operation of a public utility is a major
municipal investment and on-going service that is provided by the City. It is
imperative that the municipal investments be preserved over the long term and
that major changes to the system provide a positive benefit that is commensurate
with the associated cost.


 • Funding priorities will be placed on maintaining the existing municipal
   sanitary sewer system.

 • A financial analysis will be prepared prior to the reconstruction of any
   portion of the sanitary sewer system.

 • Funding of future sewer facility improvements will continue to be identified
   in the Capital Improvements Plan.

April 1999                            7-19                          City of Minnetonka
                            Sanitary Sewer System Plan

Municipal Operations and Maintenance

The overall maintenance of the municipal sewer system is an integral activity that
is directed towards the long-term preservation of the system. Further,
management practices are aimed at responding to customer complaints, system
upkeep and continual monitoring.


 • To maintain operating efficiency, minimize sewage blockages, and reduce
   the potential for infiltration/inflow.

 • Continue to improve the City’s maintenance and inspection program.


A goal of the City’s is to reduce point and non-point pollution sources within the
City to the extent possible. The construction of the municipal sanitary sewer
system and eventual elimination of private on-site systems is one of the major
strategies the City has utilized to achieve this goal.


 • All on-site systems shall comply with requirements of the Minnesota
   Pollution Control Agency and the Minnesota State Department of Health.

 • On-site systems shall be discontinued according to City policy when
   municipal sanitary sewer is available to serve the property.

2020 Sanitary Sewer System Plan
The 2020 Sanitary Sewer System Plan has been developed to portray the
condition of the Minnetonka sanitary sewer system under future flow conditions
assuming that the population and employment forecasts are achieved, and the
operational recommendations of this plan are followed on an annual basis. The
purpose in developing a future plan is to anticipate changes to the system that
may be required or to alter development control practices to allow for the
development of a responsible Capital Improvements Program for the sanitary
sewer system. Additionally, the development of a future plan allows the
Metropolitan Council to review the future adequacy of the metropolitan
interceptor sewer system and the Blue Lake treatment plant.

April 1999                           7-20                          City of Minnetonka
                                 Sanitary Sewer System Plan

Sewer Flow Forecasts

The Metropolitan Council prepares population, household and employment
forecasts on a periodic basis. These forecasts are based upon the policies reflected
in the Regional Blueprint and provide the basis for sizing metropolitan facilities.
The City has prepared their own forecasts that are based upon the availability of
vacant and redevelopable vacant land in the City, and local knowledge of
development trends. The forecasts are utilized to develop estimated sewer flows
for the metropolitan and municipal sewer systems that are generated in

The City projections are slightly lower than those prepared by the Metropolitan
Council and reflect implementation of the 2020 Land Use Plan. Table 7-8 depicts
the 1990 Census population, household and employment, and forecasts for 2000
to 2020 developed by the City.

     Table 7-8
     Population, Household and Employment Forecasts
                         1990     1996*     2000      2010    2020
   Population           48,401   51,000    48,156    50,032   49,815
   Household            18,687   20,603    20,332    22,013   23,111
   Employment           35,536   42,789    44,879    51,851   54,243
*Metropolitan Council Estimate

Citywide Sewer Flows

Citywide sanitary sewer flow projections for the period 1997 through 2020 are
determined by using the latest trends in residential and commercial/industrial base
flows. The residential flows were determined by averaging the estimated sewer
flows for residential properties reported by the City from 1993 to 1997, and
applying a per person usage to the population estimates to 2020. The base flow
for the residential increment is 61 gallons per person per day. The base flow for
commercial/industrial was determined by averaging the estimated commercial
and institutional flows reported by the City from 1993 to 1997 and applying a
estimated gallonage per employee based upon the employment estimates. The
estimated sewer flow per employee is 41 gallons per employee per day. Table 7-9
depicts the projected daily sanitary sewer flows in five-year increments to 2020.

April 1999                                7-21                       City of Minnetonka
                                   Sanitary Sewer System Plan

Table 7-9
Projected Annual Sanitary Sewer Flow

    Year      Population         Residential         Employee     Employment      Total Flow
                                 Flow (MGY)          Population   Flow (MGY)        (MGY)
    1990          48,370             1382.0            35,536        655.6           2037.6
   1996*          51,000             1022.3            44,027        513.8           1536.1
    2000          48,156             1072.0            44,879        671.6           1743.6
    2005          49,094             1093.0            48,365        723.8           1816.8
    2010          50,032             1114.0            51,851        775.9           1889.9
    2015          49,234             1096.0            53,047        793.8           1889.8
    2020          49,815             1109.0            54,243        811.7           1920.7
*estimate from the Metropolitan Council

The Metropolitan Council requires the submittal of sewer flow projections based
upon metropolitan interceptor sewer service areas and the utilization of past
trends of metered flows for each community. These flow projections are typically
higher than the community based flows because the projections take into account
inflow and infiltration, and unmetered flows. In 1995, the City flows were
approximately 73% of the metered MCES flows, and in 1996 and 1997 City flows
represented approximately 60% of MCES flows.

The Metropolitan Council has established a range of flows for Minnetonka that
are based upon historical MCES wastewater flow data and the Metropolitan
Council forecasts for future households and employment. Estimates of future
sewer flows have been established per service area based upon the City estimates
and historical MCES flows for Minnetonka. The estimates are depicted on Table
7 -10.

The existing municipal sanitary sewer system was designed and constructed to
accommodate a population of 160,000. The overall system capabilities are
adequate to accommodate the forecasted population and employment growth
noted on Table 7-9. However, it will be important to review existing sewer
facility capabilities when redevelopment within certain designated areas is
proposed to ensure that the pipe size and lift station characteristics can
accommodate the change in the intensity and type of use. Likewise, as the street
reconstruction program continues into the future, replacement of deteriorating
pipe should continue to be an integral part of any project, as appropriate.

April 1999                                    7-22                       City of Minnetonka
                            Sanitary Sewer System Plan

Table 7-10

Metropolitan Council Sewer Flow Estimates for Minnetonka (MGY)

 Service Area       2000       2005           2010    2015       2020
 M410                1860       1896          1932       1902     1925
 M411                181        185           188        185      187
 M412                543        553           564        555      561
 Total               2584       2634          2684       2642     2673

 Metropolitan Council Estimates

 Low                2384        NA            2561       NA       2678
 High               2700        NA            2882       NA       3005

The sewer forecasts based upon the City population and employment are within
the Metropolitan Council low and high flow forecasts. Therefore, there should not
be any impacts to the metropolitan system resulting from future population and
employment growth in Minnetonka.

Capital Improvements

The programming of major capital sewer facilities are planned and provided for in
the sewer and water portion of the City’s Capital Improvements Plan and
Program (CIP). The CIP prioritizes the timing for the identified improvements,
presents an estimate of the cost and identifies the funding source. The City will
make a final decision about actual improvement installation before construction is
authorized. The CIP is updated annually by the City Council.

While no new trunk sewer or additional facilities are required in the City due to
the completion of the overall system, there is a need for lateral sewer pipe
extensions, on-going system maintenance and replacement of system components
due to age or proposed redevelopment. Lateral sewer service needs to be provided
to the few remaining properties that will undergo development and existing
residences where service was not previously available. The lateral service
extensions are annually programmed in the CIP by developer or resident petition
the year preceding proposed construction. Additionally, on-going maintenance of
the sewer system and facilities is programmed in the CIP. The maintenance
improvements range from lift pump replacement and lift station improvements to
the removal of inadequate sewer pipe and replacement when street reconstruction

April 1999                             7-23                       City of Minnetonka
                               Sanitary Sewer System Plan

  Table 7-11 lists the 1998 sewer improvements from the 1998-2002 CIP
  improvements and those that have been programmed to the year 2003 from the
  1999-2003 CIP.

Table 7-11
Capital Improvement Program: 1998 - 2003

       Activity            1998        1999       2000       2001       2002         2003
Sanitary Sewer Laterals   Programmed in CIP year before proposed construction of subdivision

Lift Stations
Burchlane Replacement     $310,000
Old Bren Road             $70,000

Lift Pump Replacements
Opus                                 $200,000
Minnetonka Boulevard                             $70,000
Windridge                                                   $50,000
Whitegate/Glen Lake                                                   $60,000
Ford/Westwood                                                                     $70,000

  April 1999                             7-24                          City of Minnetonka

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