Approval Letter 12-12-06
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: 952.227.1190
Engineering
Phone: 952.227.1160
Fax: 952.227.1170
Finance
Phone: 952.227.1140
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: 952.227.1130
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
www.ci.chanhassen.mn.us
December 12, 2007
Mr. Jay Pomeroy
Anderson-Johnson Associates, Inc.
7575 Golden Valley Road, Suite 200
Minneapolis, MN 55427
Re:
Chanhassen High School
Planning Case #06-35
Dear Mr Pomeroy:
This letter is to confirm that on December 11, 2006, the Chanhassen City Council
approved:
A resolution of Negative Declaration of the Need for an Environmental Impact
Statement for the Chanhassen High School Campus.
And,
An Interim Use Permit to permit grading on the property in preparation of
development, plans prepared by Anderson-Johnson Associates, Inc., dated 10-19-06,
subject to the following conditions:
1. The 50-scale plans should be revised to clearly depict the wetland boundary
and wetland buffer areas.
2. Wetland buffer areas at least 16.5 feet in width should be preserved, surveyed
and staked in accordance with the City's wetland ordinance prior to grading
commencing. All wetlands and wetland buffer areas should be protected by silt
fence during grading.
3. The applicant should keep the goals set forth in the Bluff Creek Watershed
Natural Resources Management Plan (BCWNRMP) for the Lowlands Region
in mind as a plan is developed for the site and should work with staff to
achieve these goals for this property. The Primary Zone boundary and the 40-
foot setback should be shown on the plans. No grading is permitted within the
first 20 feet of the 40-foot setback.
4. The erosion and sediment control plan should be aimed at minimizing the
amount of exposed soil at any given time and preventing erosion of exposed
soil. Sediment control (especially perimeter controls such as silt fence) should
be viewed as a last resort. The applicant, the contractor and all subcontractors
should recognize that one silt fence at the bottom of a large slope of exposed
soil will not be sufficient to protect down gradient resources in even moderate
precipitation or snowmelt events. To decrease the potential for discharge of
The City of 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.
Mr. Jay Pomeroy
Chanhassen High School Site
December 12,2006
Page 2 of 4
sediment-laden water off-site, the applicant should prepare a plan for phasing the grading of
the project. In general, the areas within 200 feet of wetlands should be graded first and
permanently stabilized as soon as possible. Disturbed areas should be stabilized as soon as
possible after grading to minimize the total amount of exposed soil on site. New areas
should not be graded until after previously graded areas are stabilized.
5. Sediment & Erosion Control (SWPPP) Note 2.a.2 on Sheet C1.2 states that slopes steeper
than 6:1 should be "cat tracked." The applicant should take extra measures to ensure that this
occurs because cat tracking has been shown to significantly decrease the potential for erosion
on long, steep slopes. A detail should be provided for cat tracking.
6. The haul route between the Construction Staging Area and the Temporary Stockpile Area
should be shown on the 50-scale plans.
7. All upland areas disturbed as a result of construction activities shall be immediately restored
with seed and disc-mulched, covered with a wood-fiber blanket or sodded within two weeks of
completion of grading in each disturbed area. If practical, a seed and blown-compost mix
should be considered in lieu of dormant seed and straw mulch. The plans should be revised to
call out erosion control blanket locations and to provide a detail for blanket installation.
8. Chanhassen Type II silt fence should be provided adjacent to all areas to be preserved as
buffer (both 16.5-foot wetland buffers and the 20-foot "no grading" zone around the Primary
Zone). The silt fence should be installed in overlapping "J-hooks" to break up the sections
and provide additional water and sediment retaining capacity. Orange tree protection fence
should be installed upslope from the Type 2 silt fence around the wetland between
Temporary Sediment Basin No.3 and Temporary Sediment Basin No.4 as added protection
so equipment operators do not impact the wetland by driving heavy equipment through it.
9. The plans should be revised to include Chanhassen's standard details where available (e.g.,
Detail 5300 for silt fence; Detail 5301 for rock construction entrance). It appears that detail 3
on Sheet CIA is intended to depict the proposed checks within the temporary drainageways
shown on Sheet C1.2. This should be clarified and the checks should be installed as often as is
necessary to minimize the velocities of runoff in the drainageways. The plans should be revised
to show a minimum 75-foot long rock construction entrance.
10. In lieu of the proposed outlet pipes for the temporary sediment basins, temporary perforated
risers and stable emergency overflows (EOPs) are needed; details should be included in the
plan. The basins should be properly sized for the watershed areas, according to NPDES
requirements (i.e., the basins should provide storage below the outlet pipe for a calculated
volume of runoff from at least a 2-year, 24-hour storm from each acre drained to the basin,
except that in no case shall the basin provide less than 1800 cubic feet of storage below the
outlet pipe from each acre drained to the basin). The outlet pipes should discharge upstream
from the edge of the receiving wetlands and should be stabilized with riprap.
11. In the present design, water is routed into the wetland in the northeast comer of the site
instead of into Temporary Sediment Basin No.4. The grading in this area of the site should
be revised to ensure that all discharge from disturbed areas is directed into either Temporary
Mr. Jay Pomeroy
Chanhassen High School Site
December 12, 2006
Page 3 of 4
Sediment Basin No.3 or Temporary Sediment Basin No.4 prior to discharge into the
wetland.
12. Street cleaning of soil tracked onto public streets shall include daily street scraping and street
sweeping as needed.
13. The applicant shall apply for and obtain permits from the appropriate regulatory agencies (e.g.,
Riley-Purgatory-Bluff Creek Watershed District, Minnesota Pollution Control Agency) and
comply with their conditions of approval.
14. All temporary stockpiles shall be temporary seeded and mulched within 7 or 14 days, in
accordance with the NPDES Phase II construction site permit.
15. Rock dissipation shall be installed at all pipe outlets within 24 hours of placement of the
outlet pipes.
16. Slope lengths greater than 75 feet shall be broken up with a minimum 12-foot wide bench
every 75 feet.
17. A minimum12-foot buffer area shall be maintained between the perimeter control and all
stockpiles to provide access around the stockpiles for maintenance purposes.
18. Dewatering activities shall only be allowed after consulting with the on-site city inspector of
the project to ensure compliance with the NPDES permit for dewatering activities.
19. Silt fence shall be placed parallel to contours. In locations where silt fence will cross
contours, J-hooks shall be installed at 75-foot intervals. Silt fence shall not be staked on site
by scaling off the proposed plan, but shall be staked by the survey crew taking shots in the
field. The applicant shall contact SWCD staff prior to silt fence installation so staking on site
can be reviewed to ensure compliance with this request.
20. Drainage swales and ditch cuts shall be employed during mass grading to maintain a positive
flow of stormwater to the temporary basins.
21. During final grading of the site, the height of the berm over the sanitary sewer shall be
reduced to the maximum extent practicable, otherwise additional drainage and utility
easements may be required.
22. The developer is required to televise the section of sanitary sewer over which grading
operations will occur before and after construction to determine if the site grading damaged
the pipe.
23.ISD 112 shall be responsible for repairing any sections of sanitary sewer damaged during
construction.
24. The developer must place sanitary sewer manhole sections on the existing manhole to bring
the top of manhole up to the existing grade.
Mr. Jay Pomeroy
Chanhassen High School Site
December 12, 2006
Page 4 of 4
25. No more than eight inches of rings is allowed on the sanitary sewer manhole.
Prior to beginning site grading, please schedule a pre-construction meeting, which can be
coordinated through Gordy Stauff, Construction Manager, at (952) 227-1166. If you have
additional questions, please contact myself at (952) 227-1131 or Alyson Fauske, Assistant City
Engineer, at (952) 227-1164.
Sinc;,~ r
'~J<~
I
J~~~
Robert Generous, AICP
Senior Planner
ec: Kate Aanenson, Community Development Director
Alyson Fauske, Assistant City Engineer
Gordy Stauff, Construction Manager
c: Steve Pumper
Independent School District 112
11 Peavey Road
Chaska, MN 55318
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