3. Watermain & Sewer Improvements Lake Riley Hills, Plans & Specs I 3 .
CITY OF
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690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317
In (612) 937-1900 • FAX (612) 9374-,5739
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IMEMORANDUM
TO: Don Ashworth, City Manager A - - /O - 3/-`i/
IIFROM: Charles Folch, City Engineer
L4 , _
IDATE: October 30, 1991 .,�:_ II-,-i---9/
SUBJ: Public Hearing for Trunk Watermain and Sanitary Sewer
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Improvements in Section 24 and Lake Riley Hills;
I Authorize Preparation of Plans and Specifications
Project No. 90-10
IThis is the public hearing on the feasibility study for trunk
watermain and sanitary sewer improvements in Section 24, Lake Riley
I Hills. The impetus for this project was a petition from John
Klingelhutz, the developer of the proposed Lake Riley Hills
Addition in the northeast corner of Section 24, northwest of Lake
Riley. The purpose of this study is to determine the feasibility
I of providing trunk sanitary sewer and watermain facilities to the
proposed Lake Riley Hills subdivision and adjacent service area.
The study area encompasses the properties north and west of Lake
I Riley, south of the proposed State Trunk Highway 212 corridor and
east of State Trunk Highway 101 and bounded to the south by the
Municipal Urban Service Area (MUSA) limits.
ITrunk Sanitary Sewer
I To determine the size and extent of trunk sewer facility
improvements needed, the capacity of the existing sanitary sewer
system was evaluated and compared to the overall needs of the
I defined service area. The investigation revealed that the proposed
Lake Riley Hills subdivision could connect into the existing
sanitary sewer system immediately upstream of Lift Station No. 17
without requiring any needed system improvements. However, full
I development of this subdivision would use up the remaining
available capacity of the existing Lift Station No. 17. Therefore,
any further development within the service area would require the
I construction of a new lift station with larger capacity pumps and
associated piping.
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ItSi PRINTED ON RECYCLED PAPER
I
Don' Ashworth
October 30, 1991
Page 2
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If the lift station pumping capacity is increased to meet demand,
' the next limiting factor would be downstream sewer main capacity.
It was found that existing downstream pipe capacity restrictions
would only allow approximately 1/3 of the service area to be
adequately served. To serve the entire study area, the capacity of
' the existing mains through the Rice Marsh Lake area would need to
be increased via reconstruction of the existing main or
construction of a new main. However, topography, poor soils and
environmental factors associated with the Rice Marsh Lake area
would make rebuilding or replacing the sewer main very costly if at
all permitted by the DNR.
' As this study was nearing completion, a separate comprehensive
sanitary sewer and water study was being conducted for the new MUSA
expansion area approved by the Metropolitan Council earlier this
' year. The MUSA expansion study revealed that the 1995 study area,
adjacent to the Lake Riley Hills study area, would need future
sanitary sewer service via a forcemain extending north along Trunk
' Highway 101 to the Lake Ann Interceptor. It is also possible that
this forcemain could serve the Bluff Creek drainage area, thus
eliminating the need for a future MWCC Bluff Creek Interceptor.
This idea is currently being reviewed by the MWCC to determine if
the Lake Ann/Red Rock Interceptors have sufficient capacity to
serve the Bluff Creek area. If the MWCC concludes that this is a
' feasible proposal, it would seem pore appropriate to construct a
trunk sanitary sewer and forcemain facility along Lyman Boulevard
to serve Lake Riley Hills and surrounding service area which would
' combine with the Trunk Highway 101 forcemain and reduce the overall
cost of providing trunk sanitary sewer to these two service areas
and avoid impacting the environmentally sensitive Rice Marsh Lake
' area.
The sanitary sewer cost presented in this report is representative
of the improvements to the existing facility which would only be
able to serve approximately 1/3 of this study area. Unless major
reconstruction of approximately one mile of sanitary sewer through
the Rice Marsh Lake area is undertaken, the existing facilities
' cannot serve the entire study area. Cost estimates are in excess
of $100 per foot of sewer pipe to construct through the wetland
area of Rice Marsh Lake.
' If the joint Trunk Highway 101/Lake Riley Hills forcemain facility
is accessible to the MWCC, the associated improvement cost and
corresponding proposed assessments to benefitting properties could
' then be determined. At this time it is estimated that the area
trunk sanitary sewer assessment could range from $1, 500 to $2 , 500
per unit. Therefore, for the purposes of this study, a "ballpark"
estimate of $2, 000 per unit has been employed. For raw land guides
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Don Ashworth I
October 30, 1991
Page 3 I
for low density residential, a density factor of 1.85 units per
acre has been employed to estimate total units generated.
It should be noted that existing homes within the study area that
are currently connected to city sanitary sewer are not proposed for
assessment. The proposed Lake Riley Hills subdivision, however, is
included in the benefit area for trunk sewer assessments.
Trunk Watermain 1
The trunk watermain needs of the study area were also evaluated. '
Based on the study findings, it is recommended that a 20-inch
watermain be extended south along Trunk Highway 101 from the
Chanhassen Hills area and that a 12-inch trunk watermain be
extended from that point east along Lyman Boulevard to serve the
study area.
The associated cost for the trunk watermain improvements have also 1
been established. Based on past policy and practices of assessing
trunk watermain projects, an estimate of $830 per unit assessment
is presented. '
One of the important aspects of establishing trunk area and
connection charges is to adequately finance the cost- of the
installation of the trunk improvements and also future system
improvements which are not assessed such as wells, booster
stations, and storage facilities. There are many variables which
affect the cost for the system improvements and may cause
assessments for one service area to be higher or lower than an
adjacent future service area. These assessment differentials put
staff and Council in awkward positions at assessment hearings and
cause decision making to be very difficult. The Council has
experienced these problems recently for both utility and street
improvement projects and has since directed staff to develop
written assessment policies for capital improvements projects for
thier review and approval.
As I mentioned previously, the City has retained a consultant to
determine the comprehensive trunk sanitary sewer, watermain and
associated system facility needs for the MUSA expansion area which
includes the Riley Creek and portions of the Bluff Creek drainage
areas. Given the extent of the effort involved in this
comprehensive study, a limited addition to the study scope would
provide the City with overall system costs for the majority of the
undeveloped areas in the Riley/Bluff Creek Districts. Knowing
these costs would afford the City the ability to establish a
financing program using a combination of uniform area trunk
assessments and connection charges to finance the completion of the
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Don Ashworth
October 30, 1991
Page 4
sewer and water system facilities. These uniform area trunk
assessments and connection charges would be employed as development
drives capital improvements for sub-drainage district service
areas. These rates would be adjusted each year for inflation,
thereby yielding them applicable for capital improvement projects
within the Riley/Bluff Creek Districts in 1992 as well as into the
future. I would estimate that the needed work effort could be
completed within six weeks.
The area trunk assessments provided in this report are "ballpark"
estimates. These numbers may have to be adjusted somewhat to be
consistent with the forthcoming uniform assessment policies. It
would be appropriate to proceed with holding the public hearing on
these improvements in order to continue discussions with the
' affected property owners in the study area, some of whom attended
the recent neighborhood meeting and to gather input as to whether
the majority of property owners along Lake Riley Boulevard,
Deerfoot Path and Kiowa, who are currently on the sanitary sewer
and wells, would like to be included in the trunk watermain scope
of the project.
At the close of the night's discussions, if there is majority
support for these capital improvements and associated special
assessments, it would be appropriate to order the project and
' authorize the project consultant engineer to proceed with the
preparation of plans and specifications. If there should be a
significant number of questions and issues discussed which require
further investigation or if there is significant opposition among
1 affected property owners, I would recommend continuing the hearing
to a future date. December 9, 1991 would be the next opportunity.
ktm
c: Dave Mitchell, OSM
Bill Engelhardt, Engelhardt & Associates
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