1c. The Preserve at Bluff Creek 2nd Addition Grading Plan Changes
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
w:."/I. ci. chan hassen.mn. us
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MEMORANDUM
TO: Paul Oehme, Public Works Director/City Engineeq ~
FROM: Alyson Fauske, Assistant City Engineer of ri:f:I
DATE: September 10, 2007
SUBJECT: The Preserve at Bluff Creek 2nd Addition- Proposed changes to the
final grading plan
BACKGROUND
On May 14, 2007 City Council approved the final plat for The Preserve at Bluff
Creek 2nd Addition. Approval of the 2nd Addition included mass grading the
future additions in order to balance the dirt work on the site.
During grading operations, the developer's engineer revised earthwork
calculations and estimate that there is approximately 43,000 cubic yards of excess
material on the site.
The attached memo from the developer's engmeer explains that the excess
material was generated due to the following:
1. Lowering the street stub to the Dorsey parcel to the east,
2. Import of structural fill for the realignment of the trunk sanitary sewer and
watermain on the west side of the site, and
3. The excavated material is not achieving the compaction assumed in the
original earthwork calculations. It's quite common for the earthwork not
to balance on any project due to the assumptions that must be made for the
earthwork computations. Earthwork balance is particularly challenging on
a project of this magnitude where over 400,000 c.y. of material was
moved on the entire site.
In August, 2007 the developer submitted a revised grading plan for approval.
Due to the amount of excess dirt proposed to be blended into the site, Staff
indicated to the development team that the proposed changes could not be
approved administratively.
At Staff's request, the proposed revisions will not raise the buildings on the north
side of the site, adjacent to Lyman Boulevard. The majority of the proposed fill
would be placed in the interior of the future phase.
The developer's engineer notes that raising the grades on the east side of the
property is required to reduce the height of the retaining wall adjacent to the
Dorsey parcel from 12 feet (maximum) to seven feet (maximum).
The orientation of the lots in the future phases is consistent with the preliminary
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.
The Preserve at Bluff Creek 2nd Addition- Grading Plan Revisions
Page 2 of 3
The developer does not propose any cut or fill over the realigned trunk sanitary sewer or trunk
watermain on the west side of the site. Utilities have not beeninstalled in the future phase,
therefore cover over watermain, sanitary sewer or storm sewer is not an issue with the proposed
changes.
The developer's engineer provided the attached cross sections to illustrate the proposed grading
changes. The proposed changes to the rooftop elevations are summarized below:
Change Change Change Change
Lot in roof Lot in roof Lot in roof Lot in roof
elevation elevation elevation elevation
1 +0.7 ft 1 + 1.0 ft 1 + 1.2 ft 1 + 1.6 ft
~ 2 - 2 +0.1 ft 2 + 1.2 ft 2 + 1.3 ft
~ 3 +0.4 ft 3 + 1.2 ft
c.I 3 +0.5 ft
0
- 3 4 +0.3 ft 4 + 1.2 ft 4 +0.2 ft
~ - <
N 5 +0.1 ft 5 + 1.2 ft 5 +0.2 ft
~
1 c.I 6 +0.9 ft < 6 + 1.2 ft 6
- 0 < -
- ~
2 ~ 7 +3.9 ft 7 + 1.5 ft lI'l 7 +0.4 ft
- ~ ~
3 8 +2.8 ft c.I 8 + 1.9 ft c.I 8 +2.6 ft
- 0 0
- -
4 - 9 + 1. 7 ft ~ 9 +1.7 ft ~ 9 +2.0 ft
5 - 10 +3.2 ft 10 +1.7 ft 10 + 1.7 ft
6 - 1 -0.2 ft 11 + 1.2 ft 11 +2.2 ft
< 7 + 1.0 ft < 2 -0.2 ft 12 - 12 +2.1 ft
~ 8 +0.8 ft ~ 3 + 1.2 ft 13 13 +2.3 ft
~ ~ -
c.I 9 +0.4 ft c.I 4 +1.7 ft 14 14 +5.4 ft
0 0 -
- -
~ 10 +0.4 ft ~ 5 +2.3 ft
11 +0.6 ft 6 +3.9 ft 1 +1.4 ft 1 +2.6 ft
<
12 +0.8 ft 1 +4.8 ft t'-
~ < 2 +1.8ft
13 +1.1ft 2 +5.0 ft c.I 00
0 ~
-
14 + 1.5 ft < 3 +2.2 ft ~ 2 +1.4ft c.I
0
~ - 3 + 1.7 ft
15 +1.7ft ~ 4 + 1.4 ft ~
16 -0.6 ft c.I 5 + 1. 7 ft 1 +0.1 ft
0 4 + LOft
-
~ 6 +2.7 ft < 2 +0.4 ft
7 + 1. 7 ft 0\ 3 +0.2 ft
~
8 +2.2 ft c.I 4
0 -
-
~ 5 +0.5 ft
6 + 1.0 ft
The proposed grading modifications entail changing the housing style on the following eight
lots:
Block Lot House style on Proposed house
approved plan stvle
Block lA Lots 10 and 11 Rambler Rambler/Side lookout
Lot 16 Side lookout Rambler
Block 2A Lot 6 Rambler Side lookout
Block 5A Lots 4 and 5 Walkout Lookout
Block 6A Lot 3 Lookout Rambler
The Preserve at Bluff Creek 2nd Addition- proposed changes to the grading plan
Page 3 of 3
Staff concurs that the proposed house style changes best fit the proposed grading.
Typical driveways include a flatter area adjacent to garage to provide a transition from a steeper
driveway to the garage. Minor adjustments for the following lots will be required with the
building permit application in order to accommodate a 10 foot long landing at minimum 3%
grade:
. Block lA, Lots 7 and 16,
. Block 2A, Lot 10,
. Block SA, Lots 8, 13 and 14, and
. Block 6A, Lots 3 and 6
If the grading changes are not approved, the development team estimates that 200 trucks per day
would haul material off site for one month. The vehicles would haul on Bluff Creek Boulevard
to Lyman Boulevard.
RECOMMENDED CONDITIONS OF APPROVAL
Staff recommends approval of the changes to the grading plan for The Preserve at Bluff Creek
2nd Addition.
Ene.
c: Mark Sonstegard, Ryland Homes
Justin Larson, Westwood Professional Services, Inc.
G:\ENG\PROJECTS\T-Z\The Preserve 2nd\09-1O-07 grading plan changes.doc
'"
Westwood
MEMORANDUM
Westwood Professional Services
1212 Rod fox Road
Arden H,:h. MN 55344
Date: August 20, 2007
,..." 651.288.0600
'^ x 651.288.0659
TOll "IF. 1.888.937.5150
fMAll v:ps(t\vC"st\\ooodps.(om
www.westwoodps.com
Re: The Preserve at Bluff Creek
File 2003-1110.01
To: Alyson Fauske, City of Chanhassen
From: Justin Larson
PROPOSAL
In working to balance earthwork operations and accommodate a variety of requests,
the applicant proposes to adjust phase-2 grading for the Preserve at Bluff Creek
project. The proposal holds the perimeter grades (i.e., 3:1 sloped embankment at rear
of pads), and raises the remaining pond and interior lots and streets, as well as lowers
the retaining wall and stub street located to the east as requested by representatives
from the property owner to the east.
The proposed adjustment averages 2 feet over the remaining phase 2 grading area. By
making this adjustment, there will be no additional impacts to flood plain or wetlands.
Nor will there be additional impacts to the northern embankment or lots backing along
Lyman Boulevard.
BACKGROUND
The Applicant is generating a surplus of excavated soils during grading operations and
is seeking to both adjust the final grading plan to balance the remaining earthwork on-
site and also work to reduce the grade difference to the abutting parcel to the east. A
number of factors are contributing to these conditions:
1. Raising Grades Along Retaining Wall. Representatives for the adjacent
property to the east have requested that the height of the retaining wall along
the common boundary be reduced. This request was reiterated by the
Chanhassen City Council during Final Plat approval of the 2nd Addition plat.
To do so, the Applicant must elevate River Rock Drive North and various
house elevations in the vicinity of the wall. Raising this portion of the
development has a cascading effect throughout the phase due to the rolling
topographic nature of the site. The consequence is that other areas will have to
be adjusted upwards as well. The Applicant has reduced the wall from its
original elevation of 12' down to 7'.
2. Adjustment for Public Access to Adjacent Property. Representatives for the
adjacent property to the east have requested that Mills Drive be lowered where
~: ~, T ;\ F; r ~ H r ') I h 1 t-, l6'
TWIN CITIESIMETRO
ST. CLOU 0
BRAINERD
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Westwood
August 20, 2007
Page 2
it stubs to their property. The result of this action is that the connection point
has been lowered 2 feet from the previously approved grading plan. The
consequence is that other areas abutting the section of street that is being
lowered will have to be lowered as well, generating additional material.
3. Phase -1 Import for Structural Fill. Approximately 1,500 cy was imported
to correct settlement of the Trunk Sewer and Water Main utilities located along
Bluff Creek. This work was performed as part of a relocation effort at the
urging of City staff to avoid future access and maintenance issues. An
unforeseen ramification of this exercise resulted in excavations of over 10' of
unsuitable foundation material to provide sufficient bearing for manholes and
pIpe.
4. Excavated material is not compacting to the anticipated volume during
grading operations. As soils are excavated from one location and placed in
another, the material is compacted to volumes usually greater than its original
in-place density to support houses and roadways. Due to the variability of soil
type and moisture composition, it's not uncommon to have a lot of fluctuation
during this process. In this case, approximately 400,000 cy is being excavated
as part of the grading activities. The Consultant and Contractor separately
assumed 25% compaction however the material appears to be compacting only
15% (10% less then assumed) yielding approximately 40,000 cy of excess.
Normally grade adjustments can be made across a project to resolve earthwork
discrepancies between design compaction factors and actual compaction factors
exhibited by the soils in the field or other issues that may arise. In this instance,
adjusting the project a half foot would balance the remaining earthwork; however there
are constraints on all sides that prohibit this from being done:
1. Northern Constraints - Lyman Boulevard, existing utilities and easements,
and the future installation of trunk water facilities.
2. Western Constraints - Bluff Creek and associated wetlands.
3. Southern Constraints - 1St and 2nd Addition is complete with streets and
utilities, home construction is underway.
4. Easterly Constraints - Property boundary and grade restrictions.
In addition to the above, the adjustment area is further limited in that the City has
asked that the Applicant lower grades for streets and lots adjacent to the trunk utilities
by as much as 10.' The benefit is that the sanitary sewer is not as deep and
maintenance and access will be easier in the future when residents have settled the
property .
[ '\ ';- .<'. 1 5 '1 i D I [~ ~! ! )
planning> engineering> surveying
"T
westwood
August 20, 2007
Page 3
SUMMARY
The Applicant is working towards balancing excavations on site as well as
accommodating other requests of both the City and representatives of adjacent
property owners. Due to a variety of constraints, the Applicant has to concentrate the
mass of this operation interior to the phase 2 grading limits while minimally impacting
the perimeter. Due to the topographical nature of the Bluff Creek corridor, the result of
the grade revisions will not have an adverse affect on adjacent properties nor degrade
environmental resources.
Please contact me if you have any questions.
Sincerely,
WESTWOOD PROFESSIONAL SERVICES
Justin Larson
Proj ect Manager
= ~
planning> engineering> surveying
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