Memo from Mak Sweidan 2-14-06
CITY OF
CHANHASSEN
7700 Market Boulevard
PO Box 147
Chanhassen, MN 55317
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Fax: 952.227.1110
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Web Site
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MEMORANDUM
TO:
Bob Generous, Senior Planner
FROM:
Mak Sweidan, Engineer ~ car
February 14, 2006
DATE:
SUBJ:
Preliminary Plat Review of Powers Circle
Land Use Review File No. 98-1
Upon review of the plans prepared by BRW dated January 4, 2006, I offer the
following comments and recommendations:
GRADING. DRAINAGE. EROSION CONTROL
Approximately one-half of the parcel is proposed to be graded for the house pads
and street layout. The existing topography contains a very steep, partially wooded
slope along the westerly portion of the site. The westerly portion of the site
contains a variety of trees, shrubs and conifers. In addition, two drainage ravines
also intersect the parcel on this west slope. While previous upstream development
has decreased the amount of runoff that flows through the ravines, they still act as
a conduit to neighborhood drainage and need to be preserved. In an attempt to
preserve the drainage ravines, the applicant has proposed drainage and utility
easements over the ravines in Lots 3 and 4.
Lot 5 is proposed to be "custom graded". As such, a detailed grading, drainage,
tree removal and erosion control plan will be required at the time of building
permit application for staff review and approval. The front and rear house pad
elevation for all lots must be shown on the grading plan as well.
Generally, the overland drainage will be directed towards the homes on Lots 3, 4
and 5. The grading plan does not adequately address how this drainage will be
directed away from the homes. Staff is concerned about the volume of runoff
flowing through the ravine along both sides of Lot 3. The applicant must submit
hydrology calculations indicating the 100-year, 24-hour water elevations in each
ravine near the proposed building pads under the proposed grading conditions.
The lowest floor elevations for Lots 3 and 4 must be minimum three feet above
this elevation. The grading plan shows that the front of Lot 3 will sheet drain over
the private drive and to the front of the house pad on Lot 8. This drainage pattern
must be adjusted so that runoff will not be directed to Lot 3. Staff recommends
that the grading plan be revised prior to City Council consideration of the plat.
The City 01 Chanhassen · A growing community with clean lakes, quality schools, a charming downtown, thriving businesses, winding trails, and beautiful parks. A great place to live, work, and play.
Bob Generous
February 14,2006
Page 2
This development is adjacent to Powers Boulevard (County Road 17), which is
listed as a collector street in the City's Comprehensive Land Use Plan. According
to City Code, the development will require screening of the adjacent lots from
Powers Boulevard. The applicant has proposed a combination of landscaping and
separated berms to accomplish the screening. The separated berms will provide
openings for the runoff to drain out to Powers Boulevard as it does today.
Staff has some concerns with the berming and screening in the rearyard area of
Lot 1. The berm, which is meant to screen the rear of the house from Powers
Boulevard, does not extend far enough south to screen any of the rear house pad.
Staff is recommending that the berm be extended, approximately 40 feet, to the
south and that the berm be raised to an elevation of 910 at the northeast comer of
the lot.
The applicant and/or contractor must supply the City Engineer with a haul route
for review and approval prior to grading activities commencing. The applicant
should be aware that any grading outside of the property limits will require a
temporary easement.
The existing site drains from west to east onto Powers Boulevard where an
existing storm drainage system collects stormwater runoff and carries it north to a
stormwater quality pond for pretreatment prior to discharging into a downstream
wetland. The pond has been sized for development of this site and, as such, no
on-site pond will be required for this development. The parcel was not assessed
for any storm drainage improvements with the Powers Boulevard project and
therefore will be responsible for surface water management fees.
The plans propose two catch basins to convey stormwater runoff from Powers
Circle and the property to the north into the existing drainage system in Powers
Boulevard. There are also three proposed structures within the site to convey the
stormwater from the northern ravine, private street, and a large portion of the lots
to Powers Boulevard. In addition, storm drainage calculations for a lO-year and
100-year, 24-hour storm event must be submitted for review and approval along
with a drainage area map. No increase in off-site runoff rates to the south will be
allowed.
The sanitary sewer and watermain must be removed from the grading plan.
Erosion control measures and site restoration shall be developed in accordance
with the NPDES Construction Permit. Silt fence is shown along the majority of
the site perimeter where stormwater and sediment can run off the site. A 75-foot
rock construction entrance has been shown at the proposed street access off of
Powers Boulevard. In addition, tree preservation fencing needs to be added
around any and all trees to be saved.
Bob Generous
February 14, 2006
Page 3
UTILITIES
There is an existing home on the site which utilizes a well and septic system.
Upon installation of the public utilities, the existing house will be required to
abandon the septic tank and connect to the public sanitary sewer. The applicant
will have the option of doing the same with the existing well. In the meantime,
the existing septic and well locations need to be shown on the plans so they can be
protected during construction.
The site has not been previously assessed for utilities. As such, the site will be
subject to one sanitary sewer and water connection charge for the installation of
the existing stubs to the site. The 2006 connection charges for both sanitary sewer
and water are $5,272/unit. The connection charges will be applied toward the first
building permit that is pulled for the site. The property is also subject to sanitary
sewer and water hook-up charges for all of the lots. The 2006 trunk utility hook-
up charges are $1,575 per unit for sanitary sewer and $4,078 per unit for water.
The 2006 SAC charge is $1,625 per unit. In addition, since the property is within
the Lake Ann Sewer District, a sewer interceptor charge of $1,347 per unit and a
sub-trunk charge of $1,412 per unit will be due on each lot. These charges are
collected prior to each building permit issuance.
In conjunction with the Powers Boulevard project, municipal sewer and water
service was extended to serve this parcel and the one to the north. An 8-inch
sewer line has been extended out along the northerly lot line of the site from
Powers Boulevard. The plans propose on extending the sanitary line into the site
and then going south to serve the lots. Staff is recommending that the southern
most sanitary sewer manhole (#1) be moved within the paved portion of the
private street. This will provide easier maintenance access for City utility
workers.
A 6-inch watermain is also proposed to be extended into the site along Powers
Circle and then along the private street. The watermain must be extended to
within five feet of the south property line for future looping with the property to
the south. The plat must be revised to provide minimum 10 foot drainage and
utility easements on each side of all public utilities.
The applicant has included public sanitary sewer and watermain stubs off of the
cul-de-sac for future development of the property to the north. Upon installation
of these utilities, the house to the north will be within 150 feet of the sanitary
sewer. As per City Code Section 19-41 (a), this house will then be required to
connect to the sanitary sewer system within twelve months of the sewer becoming
available. The applicant must be aware that drop manholes are required when the
pipe inverts are greater than three feet apart.
Bob Generous
February 14, 2006
Page 4
Since all of the lots will have a lowest floor elevation of 930 or less, in-home
pressure reducing water valves will be required on all lots. Utilities along the
private street will need to have a drainage and utility easement dedicated over
them. The minimum width will be 30 feet depending on the utility depth. The
interior site storm sewer will also need to have a minimum 20-foot wide easement
dedicated over it.
Detailed utility construction plans and specifications in accordance with the City's
latest edition of Standard Specifications and Detail Plates will be required for
review and approval by the City Council at time of final plat consideration. Since
the utilities and part of the street improvements will become owned and
maintained by the City, the applicant must enter into a development contract with
the City and provide financial security in the form of a letter of credit or cash
escrow to guarantee construction of the public improvements. Permits from the
appropriate regulatory agencies will be required, including but not limited to:
Watershed District, MPCA, NPDES, Dept. of Health, Carver County, etc.
STREETS
Upon City Council approval at the September 29,2005 consent agenda, the
development is subject to the $3,600/developable acre Arterial Collector Fee. All
new developments within the Lyman Boulevard corridor are subject to this fee.
The proceeds of this fee will fund the reconstruction of Lyman Boulevard.
Access to the site is proposed by both a public street (Powers Circle) and a private
street to serve up to four of the lots (1, 2, 3 and 4). There is no need to extend a
public street to the south since the adjacent parcel has access from Oakside Circle.
The parcel to the north will have access from Powers Circle. The preliminary plat
also shows a future street access to the north. Staff is recommending that this
street be stubbed out to the property line and constructed with this project. Staff
would also recommend that the proposed driveway entrance to the north be
revised and shifted further to west.
The public street width and right-of-way for Powers Circle per City ordinance
must be 31-feet back-to-back within a 60-foot wide right-of-way. Powers Circle
must meet the City's requirements; therefore, the grade must be a maximum 7%.
The private street must be paved to a minimum width of 20-feet and built to a 7-
ton design. A turnaround area must be acceptable to the City's Fire Marshall and
be provided along the private street, maximum slope of 7% (currently shown at 17
%). Minimum 100 foot pavement length at hammer head terminus (currently
shown at 73 feet). The private street must be located within a 30-foot wide
private easement and dedicated to the benefiting property owners.
Bob Generous
February 14,2006
Page 5
Access to the site from Powers Boulevard does have a right turn lane provided.
Therefore, no additional turn lanes will be necessary. As a result of this project,
both existing homes will be required to change addresses to correspond to the new
street name.
RECOMMENDED CONDITIONS OF APPROVAL
1. Lot 5 shall be designated as a "custom graded" lot. A detailed grading,
drainage, tree removal and erosion control plan shall be submitted to the
City at time of building permit application for review and approval.
2. The applicant and/or contractor shall supply the City Engineer with a
detailed haul route for review and approval prior to site grading.
3. Shift the proposed northern parcel access off Powers Circle further to the
west, stub it out to the north property line and construct with this project.
The existing driveway for the property to the north shall be revised to
come off of the new stub street.
4. The plans shall be revised as follows:
a. Show the front and rear housepad elevations for all lots.
b. Extend the berm in Lot 1 approximately 40 feet to the south and
raise the elevation to a high of 910.
c. Add a benchmark and legend to the plans. The legend should
define all of the different line types, utilities, contours, etc.
d. Move sanitary sewer manhole (#1) to within the paved portion of
the private street.
e. Extend the watermain to within five feet of the south property line
of the site.
f. Remove contour lines from the utility plan.
g. Show the utilities in light shading on the grading plan.
h. On the grading plan, the utilities show in double layout, revise
accordingl y.
1. On the grading plan, extend the silt fence further north along the
west side of Lot 3.
J. On the grading plan, add a note to remove the north parcel access
entrance off Powers Boulevard.
k. Reroute the proposed storm sewer from CBMH2-Existing CB to be
CBMH2-CBMH3.
1. Show the proposed utilities pipe class.
m. On the utility plan, sanitary manhole #3 must be an outside drop
manhole.
Bob Generous
February 14, 2006
Page 6
n. On the utility plan, add a note that any connection to existing
structure must be core drilled.
5. The developer shall be responsible for the applicable surface water
management fees.
6. The developer shall supply the City Engineer with storm drainage
calculations for a lO-year and lOa-year, 24-hour storm event for review
and approval along with a drainage area map. There shall be no increase
in off-site runoff rates to the south.
7. Existing well and septic sites must be properly abandoned in accordance
with City Code and the Minnesota Department of Health once the sewer
and water lines become operational and are accepted by the City.
8. Detailed utility and street construction plans and specifications shall be
prepared and submitted in accordance with the City's latest edition of
Standard Specifications and Detail Plates for City Council approval at time
of final plat consideration.
9. The developer shall enter into a development contract with the City and
provide financial security in the form of a letter of credit or a cash escrow
to guarantee construction of the public improvements and compliance with
the Conditions of Approval.
10. All disturbed areas as a result of construction activities shall be
immediately restored with seed and disc mulch or wood fiber blanket or
sod within two weeks of completion of each activity in accordance with
the NPDES Construction Permit
11. The applicant shall apply for and obtain permits from the appropriate
regulatory agencies, i.e. Carver County, Watershed District, Health
Department, MPCA, and NPDES and comply with their Conditions of
Approval.
12. The developer shall include a drain tile system behind the curb to convey
sump pump discharge from the units not adjacent to ponds and/or
wetlands. This includes the private street.
13. Any offsite grading will require a temporary easement.
14. The site has not been previously assessed for utilities. As such, the site
will be subject to one sanitary sewer and water connection charge for the
Bob Generous
February 14, 2006
Page 7
installation of the existing stubs to the site. The 2006 connection charges
for both sanitary sewer and water are $5,272/unit. The connection charges
will be applied toward the first building permit that is pulled for the site.
The property is also subject to sanitary sewer and water hook-up charges
for all of the lots. The 2006 trunk utility hook-up charges are $1,575/unit
for sanitary sewer and $4,07/unit for water. The 2006 SAC charge is
$1,625 per unit. In addition, since the property is within the Lake Ann
sewer district, a sewer interceptor charge of $1,347/unit and a sub-trunk
charge of $1,412/unit will be due on each lot. These charges are collected
prior to each building permit issuance.
15. Due to the low floor elevation of the proposed lots, in-home pressure
reducing water valves will be required on all lots with a lowest floor
elevation of 930 or less.
16. Utilities along the private street will need to have a drainage and utility
easement dedicated over them. The minimum width will be 30 feet
depending on the utility depth.
17. As per City Code Section 19-41 (a), the house to the north will be required
to connect to the sanitary sewer within twelve months of the sewer
becoming available.
18. The private street must be paved to a minimum width of 20-feet, built to a
7-ton design and 7% maximum slope. A turnaround area must be
acceptable to the City's Fire Marshall and provided along the private street.
The private street must be located within a 30-foot wide private easement
and dedicated to the benefiting property owners.
19. The interior site storm sewer will need to have a minimum 20-foot wide
easement dedicated over it.
20. The developer shall submit the storm sewer sizing calculations for review
and approval along with a drainage area map prior to final plat approval.
21. Add City Details Plate Nos. 1002, 1004, 1005, 1006,2001,2103,2109,
2201,2201,2202,2204,3101,3102,3106,5200,5203,5205,5206,5217,
5232, 5234, 5300 and 5301.
22. Upon City Council approval of the September 29, 2005 Consent Agenda,
the development is subject to the $3,600/developable acre Arterial
Collector Fee. All new developments along the Lyman Boulevard corridor
are subject to this fee. The proceeds of this fee will fund the
Bob Generous
February 14, 2006
Page 8
reconstruction of Lyman Boulevard between Audubon Road and Powers
Boulevard.
23. The applicant must submit hydrology calculations indicating the 100-year,
24-hour water elevations in each ravine near the proposed building pads
under the proposed grading conditions. The lowest floor elevations for
Lots 3 and 4 must be a minimum of three feet above this elevation.
c: Paul Oehme, Director of Public Works/City Engineer
Alyson Fauske, Assistant City Engineer
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