1m. Authorization to Expend Surface Water Mgmt Program Funds 1
CITYOF
I ... /4/1
ClIANBASSEN
1 690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317
(612) 937 -1900 • FAX (612) 937 -5739 moo by ail
111 MEMORANDUM d
TO: Don Ashworth, Manager
Dap. ` /07' _
TO D Ahwrth City
' y M g NI Submitted to Commisstoli
FROM: Paul Krauss, Planning Director Pk 1 rL Ma Submitted to
DATE: February 18, 1993
' SUBJ: Authorization to Expend Surface Water Management Program Funds
For the past two months, staff has been working with a potential developer of a parcel located
at 7500 Frontier Trail. The developer's intent is to subdivide the property into single family
home sites. When Planning and Engineering staff saw the property, we recognized that this was
an area that has been identified by the Surface Water Management Program as being a major
' contributor to water quality impacts on Lotus Lake. There is a drainage area of approximately
60 acres that drains down through a ravine over the property in question, ultimately discharging
directly into Lotus Lake adjacent to a beachiot. When we looked at this proposal, we realized
' that we had an opportunity to develop an impoundment basin that could handle a significant
percentage of this water. By coupling this project with a development proposal, the city stands
to save significant costs. This is part of a project that our consultants had originally estimated
to cost $200,000 to $300,000 due to the need to acquire property. By coupling this proposal with
a subdivision request, we can essentially obtain the property for little or no cost, and would only
' need to cover costs due to oversizing of improvements.
To get a better understanding of what we want to undertake on this parcel, we have asked
1 Bonestroo to give us some advice. They have drafted a written proposal that costs $3,243 to
complete. When this work is completed, it will allow us to tell the developer exactly what we
need to have accomplished on the parcel as well as what cost share is appropriate.
' The SWMP Committee reviewed this item at their February 17 meeting and recommended that
funding be authorized by the Council. Funding would be drawn from SWMP Program funds
which have been dedicated for these purposes.
Staff Recommendation
Staff recommends the Council authorize expending $3,243 of SWMP Program funds with
Bonestroo Engineering to provide detailed information on storm water quality and quantity
improvements for the parcel located at 7500 Frontier Trail.
�� PRINTED ON RECYCLED PAPER
1 Otto G. Bonestroo. P.E. Howard A. Sanford. P.E. Michael P Rau. P.E. Miles 8 Jensen, P.E.
Bonestroo Robert W. Rosene. PE.. Keith A. Gordon. P.E. Agnes M. Ring. Ai C.P L. Phillip Gravel III. PE.
Joseph C. Anderlik. P.E. Robert R. PfefferIe. P.E. Thomas W Peterson, P.E. Karen L. Wiemen. P.E.
Marvin L Sorvala. P.E. Richard W. Foster. P.E. Michael C. Lynch. P.E. Gary D. Kristofro. P.E.
Rosene Richard E. Turner, PE. David 0. Loskota. PE. James R. Malang. PE. F Todd Foster. PE.
Anderlik & Glenn R Cook P.E Robert C. Russek. A.I.A. Jerry D. Pertach, P.E. Keith R. Yapp, P.E.
Thomas E. No P.E. Jerry A. Bourdon. P.E. Kenneth P Anderson. P.E. Shawn D. Gustafson. P.E.
Robert G. Schunicht PE. Mark A. Hanson, P.E. Mark R. Ras. P.E. Cecil* Olivier. P.E.
A ssociates Susan M. Eberlin, C.P.A. Michael T. Rautmann, P.E. Mark A. Seib P.E. Charles A. Enckson
*Senior Consultant led K. Field, P.E. Gary W. Morlen, P.E. Leo M. Pawelsky
Thomas R. Anderson. A.I.A. Daniel J. Edgerton. P.E. Harlan M. Olson
Engineers & Architects Donald C. Burgardt P.E. Daryl K. Kirschenman, P.E. James F Engelhardt
Thomas E. Angus. P.E. Philip J. Caswell. P.E.
1 Ismael Martinez P.E. Mark D. Wallis P.E.
February 16, 1993
1
City of Chanhassen
1 690 Coulter Drive
Chanhassen MN 55317
1 Re: Letter Report on Stormwater Quality Improvements
for Forcier Property at Frontier Trail
Our File No. 393 Gen.
1
Dear Paul:
1 As requested by Dave Hempel last February 12, we have developed a scope of study to evaluate
possible stormwater quality and quantity improvements of Forcier Property west of Frontier
1 Court.
This letter presents the proposed scope and estimated engineering cost of developing a
1 preliminary analysis of improvements and recommendations for future stormwater management
at the site.
1 SCOPE OF SERVICES
1 * Detailed stormwater quality and quantity modeling of all key drainage elements.
1 * Identification of the most cost effective alternative (1 pond versus 2 ponds) from both
quality and quantity standpoint.
1 Preliminary cost estimate of all proposed stormwater quality and drainage elements.
* Estimation of City's and Developer's share of the total cost of improvements.
1 * Preparation of a letter -report showing everything described above plus a digitized map
showing the proposed design alternative and results.
1
1 Page 1.
393.cor
1 2335 West Highway 36 • St. Paul, Minnesota 55113 • 612-636-4600
1
1
ESTIMATED COST 1
The estimated engineering cost of preparing the letter -report on Forcier Property improvements 1
is presented in Table 1. The final not -to- exceed amount proposed by Bonestroo & Associates
is $3,200.
1
TABLE 1
COST ESTIMATE I
Labor Hourly Total
Category Hours Rate Cost
I
Principal Engineer 2 $80.00 $ 160
Project Manager 4 70.00 280 1
Project Engineer 40 53.50 2,140
Drafting 12 40.75 489
Word Processing 6 29.00 174 1
TOTAL $3,243
1
We look forward to working with you on this study.
Yours very trul Y� 1
BONESTROO, ROSENE, ANDERLIK & ASSOCIATES, INC. 1
T,,,,,±i5/1
1
Robert G. Schunicht
RGS:Ii 1
1
1
1
Page 2. 1
393.cor
1
1 c I TY 0 I()
CHANI1ASSEN
( 690 COULTER DRIVE • P.O. BOX 147 • CHANHASSEN, MINNESOTA 55317
(612) 937 -1900 • FAX (612) 937 -5739
MEMORANDUM
' TO: SWMP Committee
FROM: Paul Krauss, Planning Director
DATE: February 11, 1993
' SUBJ: Draft Proposal to Undertake Additional Water Quality Improvements in the
Frontier Trail Area of Lotus Lake
1
Now that efforts to develop our Surface Water Plan are drawing to a close, we have access to
growing volumes of information. We are using this information to develop new strategies to
protect and improve our water resources as opportunities arise. We have been contacted by the
owner of the property located at 7500 Frontier Trail regarding a potential subdivision. As soon
' as staff saw this property, we knew we had access to one of the most important locations for a
water quality impoundment basin on the southwest side of the lake. We are working with the
property owner to incorporate a NURP basin that wilhbe designed to intercept a significant
' portion of the large volume of water that runs down off through a ravine from development
located on the hill above Frontier:T'rail. At the present time, this water is discharged totally
untreated directly into the lake. Those of you who were on our bus tour last summer will
remember seeing this location in the lake where we observed a large delta being formed by
sediments deposited by the runoff. Since these improvements are likely to occur in conjunction
with development of the property, we anticipate being able to secure them with a relatively minor
' amount of funds. We will keep you posted as to progress on this project.
t.
t PRINTED ON RECYCLED PAPER
a Otto G Someone. P.E. Nowaid A Sr. PE. MrUnael P Rau. P.E. Mdes B Jensen. PE. 1
A u B o n e s t ro o Robert W. Rosen. P.E • Kenn A Gordon. PE Agnes M. Rung. A.I.C.P L. Philp Grayel P.E.
Joseph C. AnderFk P.E. Robert R Pfeffer*. P.E. Thomas W Peterson. P1. Karen L Wremen P1
Marvin 1. Sorvaa. P.E. Richard W kart P.E. Michael C. Lynch. P1. Gary D. Knstofr2. P.E.
1
Rosen Marvin
E. Tuner. P.E. David 0 Loskaa. P.E. James R. Maland. PE. F Todd Foster. P.E
il Anderiik &
Gehl n ,R Cool` Robert ert C Russet.. A.I.A. Jerry D. Pereach. P.E free" R Yam RE
Noyes. Jerry A Bourdon. P1. Kenneth P Anderson. ►E. Shswm D Gustafson. PE
Robert G Sehu icht P.E. Mark A Hanson. PE Mane R Rods P.E. Cecila Okver. Pi
A ssociates Susan M Eberin. C.P.A Michael T Raumann. PE Mark A Sep. P.E. Charles A Enckson
1
'Sensor Con n W. suta Ted K. Field. PE Gary Monen. P.E. Leo M Pawelsky
Thomas R Anderson. A.LA Dane) .1. Edgerton. P1. Halton M. Olson
Engineers & Architects Donald C Buryardt. P.E. Daryl K. Kescnenman. PE. James F Engelhardt
Thomas E. Angus P1. Philp J. Caswell. PE.
Insael Mater= PE. Mark D. tifalR PE. '
MEMORANDUM
TO: David Hampel, a , ty Ci of Chanhassen CITY OF CHANHASSEII Fax No: 937 -5739 i
G t EV
FROM: Cecilio Olivier _ RECEIVED 1
FEB 0 8 1993
DATE: February 5, 1993 FEB 0 8 1993
ENGINEERS DEPT ITY QF chntvrviEt! 1
RE: Comments on the concept plan for Forcier Property at Frontier Trail
File 393 Gen 1
INTRODUCTION. EXISTING CONDITIONS 1
We have performed a storm water and water quality preliminary review of the proposed
development of the Forcier Property at 7500 Frontier Trail. Our review was based on the 1
concept plan prepared by Sunde Land Surveying Inc., dated October 15, 1992.
Although this concept plat only subdivides approximately 4.5 acres into single family lots, 1
the total drainage area into the two ponds shown in the plat is approximately 66.3 acres.
At the present time the area is served by a 36 -inch storm sewer trunk and by overland
drainage through a natural ditch located where the ponds are proposed. This ditch ends 1
in a 36 -inch culvert that crosses Frontier Trail. The existing culverts are capable to handle
the peak flows generated during a 100 -year storm event.
1
• PRELIMINARY COMMENTS
The followin g are our initial comments on the.coticept plan for Forcier property: 1
Water Ouantity - The development must provide stormwater storage at the proposed ponds 1
with pond outlets large enough to handle 100 -year peaks and keep high water levels 2 feet
below the lowest house. , r • • .
A minimum of two 36 -inch culverts crossing Frontier Trail will be necessary to handle 100- 1
year peak flows under fully developed conditions of the drainage area.
1
393gen.cor 1
2335 West Highway 36 • St. Paul, Minnesota 55113 •612.6364600 1
Water Quality - Water quality is a very important factor in this area because of the lack of
upstream treatment and the proximity to Lotus Lake. The SWMP identifies this area as a
high priority area for storm water improvements. The SWMP is proposing two water
' quality ponds east of Frontier Trail to treat runoff generated in this area. Any pretreatment
performed at the ponds shown in the concept plan would both increase the treatment
efficiency and reduce the cost of the proposed downstream ponds.
' FUTURE OPTIONS
•
The following is a summary of the options modeled:
' 1) Use the existing storm sewers (two 36 -inch storm sewers) under Frontier Trail and
build the ponds to handle the 100 -year overland drainage.
•
' This option assumes that the existing 36 -inch trunk remains in place and that the ponds
will take the 100 -year from the 4.5 acres plus overland drainage coming from upstream.
' The following table shows the main results for this option.
Culvert Crossing
' West Pond East Pond Frontier Trail
Storage volume (Ac. ft) 0.3 0.45
HWL for 100 -year 924.0 917.2
' Outlet structure 36" culvert 4' weir 36" CMP
Peak outflow (cfs) 44.2 43.5 46.3
Comments:
* Water quality treatment would be provided only for the 4.5 acres developed.
' * Existing 36 inch trunk must be utilized and proposed house in lot #7 can not be
moved further south.
* Proposed ponds must provide at least the storage volume shown on the above table.
* Existing house can be removed to accommodate necessary storage volume.
* Existing culverts under Frontier Trail do not need any further improvements.
2) Connect existing 36 -inch trunk to the proposed ponds and remove the portion of the
g P P Po P
existing 36 -inch trunk that crosses lot #7.
I option assumes that all 100-year runoff from the 66.3 ac. upstream the u
Thi p m Y P
' development goes into the ponds.
The main results for this option are shown in the following table.
393gen.cor 2
1
Culvert Crossing
West Pond East Pond Frontier Trail
Storage volume (Ac. ft.) 0.4 0.55 --
HWL for 100 -year 924.2 917.2 • --
Outlet structure a 4.5' weir 7' weir 2 x 36" CMP
Peak outflow (cfs) 90.2 89.2 92.7
Comments:
1
* Some water quality treatment would be provided for the entire 66.3 acres.
* Existing 36 -inch trunk crossing lot #7 would be removed.
* Existing house can be removed to accommodate the necessary storage volume
shown in the table above.
* Existing culvert under Frontier Trail can not handle the 100 -year storm. Another 1
36 -inch culvert must be built under Frontier Trail.
3) Connect existing 36 -inch trunk to the west pond and provide an outlet from this and
g Po P pond
into the existing 36 -inch storm sewer.
This option assumes that for small storm events (up to 2- year), storm water from the
upstream area will drain into the two ponds and be treated. For bigger storm events
(2 -year to 100 -year) there would be two outlets from the west pond, one into the east
pond and the other into the existing 36 -inch storm sewer.
The following table shows the main results for this option. 1
Culvert Crossing
West Pond East Pond Frontier Trail
Storage volume (Ac. ft.) 0.45 0.5
HWL for 100 -year 924.2 917.2 --
Outlet structure 2 x 36" culverts 4' weir 36" CMP
Peak outflow (cfs) 85.0 45.0 48.1
Comments:
* Some water quality treatment would be provided for the upstream 66.3 acres.
* Existing 36 -inch trunk crossing lot #7 would not be removed.
* An additional 36 -inch outlet culvert must be provided at the west pond.
* Existing house can be removed to accommodate necessary storage volume.
* Existing 36 -inch culverts under Frontier Trail do not need further
improvements.
1
393gen.cor 3 '
1.
RECOMMENDATION
We recommend option 2 as the most cost effective option. Construction of another 36 -inch
culvert crossing Frontier Trail would be required. Also, additional storage volume must be
provided by expanding the proposed ponds as shown in the attached copy. Excavation will
' be necessary to provide for the maximum wet volume available. An average depth of 6 ft.
is recommended. Also, 10:1 pond slopes are recommended for safety reasons in the first
1 -2 feet of drop.
' If you want us to analyze in more detail some of the options presented herein, please let
us know. Also, if you have any comments please call me at 636 -4600.
1 Have a nice day!
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111 393gen.cor 4
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