Memo from Mak Sweidan 11-30-04
CITY OF
CHANHASSEN
7700 Market Boulevard
PO Box 147
Chanhassen, MN 55317
Administration
Phone 952.227.1100
Fax 952.227.1110
Building Inspections
Phone: 952.227.1180
Fax 952.2271190
Engineering
Phone 952.2271160
Fax: 952.227.1170
Finance
Phone 952.2271140
Fax 952.227.1110
Park & Recreation
Phone: 952.227.1120
Fax: 952.227.1110
Recreation Center
2310 Coulter Boulevard
Phone: 952.227.1400
Fax: 952.227.1404
Planning &
Natural Resources
Phone 952.2271130
Fax 952.227.1110
Public Works
1591 Park Road
Phone: 952.227.1300
Fax 952.227.1310
Senior Center
Phone 952.227.1125
Fax: 952.227.1110
Web Site
\w^,i.ci .chanhassen. mn .us
MEMORANDUM
TO:
Bob Generous, Senior Planner
Mak Sweidan, Engineer ,-f
7
November 30, 2004
Wt0/~ IL
FROM:
DATE:
SUBJ:
Preliminary Plat Review of Pinehurst
Land Use Review File No. 04-08
Upon review of the plans submitted by Westwood, Inc. dated November 5,2004,
I offer the following comments and recommendations:
GRADING, DRAINAGE & EROSION CONTROL
The existing site is about 27 acres and has tree cover over approximately 18 acres
(65% of the parcel.) The existing parcel has a wide variety of grade changes
within its limits. The site elevations range from a high of 1070± to a low of
1006±. These severe elevation differences make this site a challenging one to
both develop and minimize grading. The plans propose to grade about 75-80% of
the site for the 43 new house pads, a proposed street system, three cul-de-sacs and
a storm water pond. The proposed grading will prepare the site for full basement,
look-out and walk-out type house pads. Retaining walls are proposed in
numerous locations throughout the site. The applicant must be aware that any
retaining wall over four feet in height must be designed by a registered civil
engineer and a permit from the city building department must be obtained. In
addition, encroachment agreements will be required for any retaining wall within
a public easement.
Staff does have a couple areas of concern in regards to the grading. The proposed
housepad on Lot 27, Block 1 has steep slopes draining to or away from it on three
out of the four sides. In staff's opinion, this grading design makes the lot
undesirable at best. Also, there are two retaining walls just south of the lot which
are adjacent to the proposed pond. If Lot 27 were eliminated, the pond could be
shifted to the north which would eliminate the need for the southerly portions of
the retaining walls. Because of the above reasons, staff is recommending that Lot
27, Block 1 be eliminated.
In addition, it appears that a large portion of the western end of the site is being
filled. This filling requires the use of five retaining walls on the western end of
the site. Staff would recommend that the applicant lower the western end of the
site in the area of the two private drives. This will help to minimize the overall
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
November 30, 2004
Page 2
amount of grading in the area, decrease the size of the retaining walls, and better
match the existing topography of the area.
The existing site drainage is encompassed within two different drainage areas.
Under existing conditions, the western part of the site drains off-site to an existing
wetland to the west; the eastern part of the site drains off-site to the south. Under
developed conditions, the applicant is proposing to capture all of the street
drainage, all of the front yard drainage and some rearyard drainage from the
interior lots. This stormwater will be conveyed via storm sewer to a proposed
pond in the south center of the site for treatment. The proposed pond must be
designed to National Urban Runoff Program (NURP) standards with maximum
3: 1 slopes and a 10: 1 bench at the NWL. In addition, the proposed ponding must
be sized to accommodate the drainage generated from the property to the north, as
shown in the City's Surface Water Management Plan (SWMP).
Drainage calculations for the site have been submitted and some changes remain.
The applicant is required to meet the existing site runoff rates for the lO-year and
100-year, 24-hour storm events. Storm sewer sizing calculations must be
submitted at the time of final plat application. The storm sewer must be sized for
a lO-year, 24-hour stOlID event. Drainage and utility easements must be dedicated
on the final plat over the public storm drainage system including ponds, drainage
swales, and wetlands up to the 100-year flood level.
Proposed erosion control must be developed in accordance with the City's Best
Management Practice Handbook (BMPH). Staff recommends that Type II silt
fence, which is a heavy duty fence, be used adj acent to the existing wetland,
existing creek area, and around the proposed pond. In addition, tree preservation
fencing must be installed at the limits of tree removal. Erosion control blankets
are recommended for all of the steep 3: 1 slopes with an elevation change of eight
feet or more. All disturbed areas, as a result of construction, must be seeded and
mulched or sodded immediately after grading to minimize erosion. The applicant
should be aware that any off-site grading will require an easement from the
appropriate property owner. If importing or exporting material for development
of the site is necessary, the applicant will be required to supply the City with
detailed haul routes.
UTILITIES
Municipal sewer and water service is available to the site from Manchester Drive
and water service is available from Galpin Boulevard. The water and sewer
mains will be extended north from Manchester Drive to serve the site. The
watermain will then be looped with the existing 12-inch diameter main along
Galpin Boulevard. In addition, water will be extended to the north property line
for future development of the parcel to the north. The water and sewer is also
proposed to be extended within two private streets (D and E) off of Street A. The
watermain in Private Drive D is proposed to be connected with the existing
Bob Generous
November 30, 2004
Page 3
watermain from the Brenden Court private street to the west. This watermain
extension can be direction ally bored which will preserve the existing trees within
the western side of the site. The watermain connection will provide a "looped"
system for the majority of the western side of the site.
The applicant is also proposing a second gravity sewer line to serve the western
two-thirds of the site. This sewer line, which runs from MH-18 to an existing
manhole in Lake Lucy Road, is proposed to go south outside of the pavement and
right-of-way, through Lot 17, Block 1 and cross over City-owned property prior
to connecting to the existing sewer line in Lake Lucy Road. Staff is
recommending that this western sewer line be eliminated for the following
reasons. First, the City-owned land that the sewer would run through is very
steep. City staff has concerns with access and maintenance of such a line on a
steep slope. Second, the City-owned property was originally acquired as a
possible future well site. The location of the sewer line on the property could
limit the possible well locations. Finally, the existing sanitary line in Manchester
Dri ve was stubbed to this property to serve the entire site.
City Code requires a minimum 30-foot wide public easement over the public
sewer and watermain within private streets. Due to the depth of the proposed
sanitary sewer from MH-20 to MH-17, however, the required easement width will
need to be increased to 50 feet.
The underlying property has been previously assessed for sewer and water
improvements and those assessments have been paid. The sanitary sewer and
water hookup charges along with the Lake Ann Interceptor charge will be
applicable for each of the new lots. The 2004 trunk hookup charge is $1,458.00
per unit for sanitary sewer and $2,814.00 per unit for watermain. The total 2004
Lake Ann Interceptor charge is $2,102 per unit and the SAC fee is $1,425.00 per
unit. All of these charges are based on the number of SAC units assigned by the
Metropolitan Council. Sanitary sewer and water-main hookup fees may be
specially assessed against the parcel at the time of building permit issuance.
All of the utility improvements are required to be constructed in accordance with
the City's latest edition of Standard Specifications and Detail Plates. Upon
completion of the utility improvements, the utilities will be turned over to the City
for maintenance and ownership. The applicant is also required to enter into a
development contract with the City and supply the necessary financial security in
the form of a letter of credit or cash escrow to guarantee installation of the
improvements and the conditions of final plat approval. The applicant must be
aware that all public utility improvements will require a pre-con meeting before
building permit issuance. Permits from the appropriate regulatory agencies will
have to be obtained, including but not limited to the MPCA, Department of
Health, and Carver County.
Bob Generous
November 30,2004
Page 4
STREETS
The plans propose two full accesses to the site; one off of Galpin Boulevard from
the east side and the other from the extension of Manchester Drive to the south.
Additionally, Street B will be extended to the north property line to allow for a
future street connection with Crestview Drive when the property to the north is
developed. A temporary cul-de-sac turnaround for emergency vehicles will be
required at the north end of Street B along with a sign stating that the road will be
extended in the future. All of the proposed public streets comply with the
minimum required right-of-way and pavement widths.
For Street C, the applicant is proposing a very wide right-of-way with a large
island in the center. Due to maintenance concerns with such a large right-of-way,
staff is recommending that Street C be revised to be a standard cul-de-sac. Also,
Galpin Boulevard is designated as an arterial road in the city. Per City Code,
arterial roads are required to have 100 feet of total right-of-way or 50 feet from
each side of the centerline of the road. As such, this development is required to
provide enough additional platted right-of-way which results in 50 feet of right-
of-way on the western side of the Galpin Boulevard centerline.
RECOMMENDED CONDITIONS OF APPROVAL
1. The applicant will be required to meet the existing site runoff rates for lO-year
and 100-year, 24-hour storm events. The proposed ponds must be designed to
National Urban Runoff Program (NURP) standards. In addition, the proposed
ponding must be sized to accommodate the drainage generated from the
property to the north, as shown in the City's Surface Water Management Plan
(SWMP).
2. The storm sewer must be designed for a lO-year, 24-hour storm event.
Submit stOlID sewer sizing calcs and drainage map prior to final plat for staff
review and approval.
3. Drainage and utility easements must be dedicated on the final plat over the
public stOlID drainage system including ponds, drainage swales, and wetlands
up to the 100-year flood level.
4. Staff recommends that Type II silt fence, which is a heavy duty fence, be used
adjacent to the existing wetland, existing creek area, and around the proposed
pond. In addition, tree preservation fencing must be installed at the limits of
tree removal. Erosion control blankets are recommended for all of the steep
3: 1 slopes with an elevation change of eight feet or more.
5. All plans must be signed by a registered Civil Engineer in the State of
Minnesota.
Bob Generous
November 30, 2004
Page 5
6. Permits from the appropriate governmental agencies must be obtained
including: MPCA, MDH, and Carver County.
7. On the utility plan:
a. Show all existing and proposed utility and pond easements.
b. Maintain lO-foot horizontal separation between all sanitary/water/storm
sewer maIllS.
c. Increase the watermain pipe size in Street D to 8-inches in diameter.
d. Add a storm sewer line between Lots 7 and 8, Block 1 with a catch basin
at the north property line for future connection by the property to the
north.
e. Extend sanitary manhole #12 to the north property line with an invert
elevation of 1049.0.
8. On the grading plan:
a. Show all existing and proposed easements.
b. Show the benchmark used for the site survey.
c. Maximum allowable side slope is 3: 1; revise in the rearyard of Lots 14
and 15, Block 1 and the rearyard of Lot 3, Block 2.
d. Show the location and elevation of all emergency overflows; the elevation
must be 1.5' lower than any adjacent house pad elevations.
e. Show the retaining wall top and bottom elevations.
f. Use storm sewer class 5 in roadway; revise note under general grading
and drainage notes accordingly.
9. Any retaining wall over four feet in height must be designed by a registered
civil engineer and a permit from the city building department must be
obtained. In addition, encroachment agreements will be required for any
retaining wall within a public easement.
10. The sanitary sewer and water hookup charges along with the Lake Ann
Interceptor charge will be applicable for each of the new lots. The 2004 trunk
hookup charge is $1,458.00 per unit for sanitary sewer and $2,814.00 per unit
for watermain. The total 2004 Lake Ann Interceptor charge is $2,102 per unit
and the SAC fee is $1,425.00 per unit. All of these charges are based on the
number of SAC units assigned by the Metropolitan Council. Sanitary sewer
and water-main hookup fees may be specially assessed against the parcel at
the time of building permit issuance.
11. All disturbed areas, as a result of construction, must be seeded and mulched or
sodded immediately after grading to minimize erosion.
12. The applicant should be aware that any off-site grading will require an
easement from the appropriate property owner.
Bob Generous
November 30,2004
Page 6
13. If importing or exporting material for development of the site is necessary, the
applicant will be required to supply the City with detailed haul routes.
14. Due to the depth of the proposed sanitary sewer from MH-20 to MH-17, the
required easement width will be increased to 50 feet.
15. All of the utility improvements are required to be constructed in accordance
with the City's latest edition of Standard Specifications and Detail Plates. The
applicant is also required to enter into a development contract with the City
and supply the necessary financial security in the form of a letter of credit or
cash escrow to guarantee installation of the improvements and the conditions
of final plat approval.
16. A temporary cul-de-sac turnaround for emergency vehicles will be required at
the north end of Street B along with a sign stating that the road will be
extended in the future.
17. Eliminate Lot 27 and shift the proposed pond to the north to eliminate some of
the retaining wall.
18. Delete the western sanitary sewer line; all sanitary sewer must drain to
Manchester Drive.
19. Revise Street C to be a standard cul-de-sac.
20. Lower the western end of the site in the area of the two private drives.
21. This development is required to provide enough additional platted right-of-
way which results in 50 feet of right-of-way on the western side of the Galpin
Boulevard centerline.
c: Paul Oehme, Public Works Director/City Engineer
Matt Saam, Assistant City Engineer
g:\eng\projects\pinehurst (mancino prop.)\spr.doc