E. MN River Flood Mitigation StudyCITY OF MEMORANDUM
CUMNSEN TO: Todd Gerhardt, City Manager
7700 Market Boulevard 0,
PO Box 147 FROM: Paul Oehme, City Engineer /Dir. of Public Works
Chanhassen, MN 55317
DATE: September 26, 2011 '
Administration
Phone: 952.227.1100
SUBJ: Update on Minnesota River Flood Mitigation Study.– PW067E2
Fax: 952.227.1110
Both the TH 41 and TH 101 options include a 10 -ft. trail the full length of the
Phone: 952.227.1130
DISCUSSION
Building Inspections
12 -foot travel lane in each direction. However, since the right -of -way on TH 41 is
Phone: 952.227.1180
Earlier this year, MnDOT initiated a study to evaluate the feasibility of reducing
Fax: 952.227.1190
flooding closures by making modifications to one or more of the three existing
Engineering
Minnesota River crossings —TH 169, TH 101 and TH 41. The study was
Phone: 952,227.1160
undertaken in response to the disruption caused by the two flood closures in 2010
Fax: 952.227.1170
and the prediction of a third major flood event in the spring of 2011. The
Senior Center
frequency and duration of these floods raised concerns that if construction of the
Finance
new TH 41 river crossing was over three decades away, then other options should
Phone: 952.227.1140
be evaluated to determine if any short-term, lower cost projects could be
Fax: 952.227.1110
identified to reduce flood impacts. This study has developed three alternatives to
Park & Recreation
consider for funding; one for each of the three river crossings.
Phone: 952.227.1120
final report is expected within the next two weeks.
Fax: 952.227.1110
This study has included one public informational meeting and a project
management team comprised of membership from the local agencies. Three
Recreation Center
meetings were also held with the permitting and resource agencies —US Army
2310 Coulter Boulevard
Corp of Engineers, US Fish and Wildlife and Minnesota Dept. of Natural
Phone: 952.227.1400
Resources. Included in the background is the summery of the findings of the
Fax: 952.227.1404
report.
Planning &
Natural Resources
Both the TH 41 and TH 101 options include a 10 -ft. trail the full length of the
Phone: 952.227.1130
corridor. Both would be two -lane bridges that include 8 -foot shoulders, and a
Fax: 952.227.1110
12 -foot travel lane in each direction. However, since the right -of -way on TH 41 is
greater, that alternative assumed a typical roadway of 72 feet vs. only 56 feet on
Public Works
TH 101. During flood conditions, TH 41 could be restriped to 4 lanes whereas
7901 Park Place
Phone: 952.2271300
TH 101 could not. The TH 169 Bloomington Ferry Bridge was also examined as
Fax: 952.227.1310
a potential flood mitigation alternative. Temporary capacity improvements, such
as the restriping implemented during the 2011 spring flood, were identified along
Senior Center
with some additional improvements necessary to reduce shoulder pavement
Phone: 952.227.1125
damage and fix the constrictions at Old Shakopee Road. A more permanent
Fax: 952.227.1110
capacity improvement was also identified for TH 169 which would widen the two
Web Site
main spans, approach pavement, and 9 smaller bridges in the vicinity;
www.ci.chanhassen.mn.us
adding a full lane of capacity in each direction at a total cost of $44 million. The
final report is expected within the next two weeks.
Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow
Mr. Todd Gerhardt
September 26, 2011
Page 2
Scott County applied for STP Bikeway grant funds this year for a trail connection
from Scott County to the LRT trail at Bluff Creek Drive. The grant request was
for $5.5 million dollars. The total project cost is estimated at $6.875 million.
Most of the funds, if awarded, would be used to help offset the trail bridge cost.
MnDOT Metro District plans to request flood mitigation bonds from the Chapter
152 funding program. MnDOT has identified $50 million of these bonds for flood
mitigation projects and approximately $20 to $25 million of statewide funding
remains to be allocated to flood mitigation projects. MnDOT intends to start
reviewing projects for funding starting the week of September 26, 2011. Funding
decisions for that program are expected before the end of the year.
ATTACHMENTS
1. Executive Summary, Minnesota River Flood Mitigation Study Final Report-
Draft
2. Highway 101 Preferred Bridge /Fill Option dated September 12, 2011
3. Highway 41 Preferred Bridge /Fill Option dated September 12, 2011
4. TH 101 Trail Crossing STP Bike Walk Project Limits
5. Letter to Nicole Peterson, MnDOT Metro District South Area Engineer dated
September 14, 2011
g: \eng \public \pw067e2 hwy 41 eis & river crossing studies \bkgd 092611 update on river crossing studyl.doc
Executive Summary
In February 2011, the Minnesota Department of Transportation (MnDOT) initiated the Minnesota River Flood
Mitigation Study to investigate lower -cost, shorter -term ways to improve local and regional mobility during
seasonal flooding in the Minnesota River Valley that can force closures of Trunk Highway 101 ( "Highway
101 ") between the Cities of Chanhassen and Shakopee and Trunk Highway 41 ( "Highway 41 ") in the City of
Chaska. In particular, these river crossings have closed due to flooding six times between spring 1993 and
spring 2011 with closure times varying from several days to several weeks. When Highways 101 and 41 are
closed, the value of the additional time and miles traveled (using the Metropolitan Council's 2030 Regional
Model to calculate the cost of closures) is $670,000 in the year 2009 and is forecasted to be $1,675,000 in the
year 2030. While a long -term replacement solution has been identified for the Highway 41 river crossing, it
will be decades before that crossing is replaced given current funding levels.
The purpose of this study is to identify a feasible design option at each river crossing that minimizes the risk of
flooding without causing an increase in the 100 -year floodway elevation. The overall study approach has been
built around the following major tasks: stakeholder and public involvement, traffic forecasting and analysis,
historical flooding analysis, river modeling using computer aided hydrological analysis, design alternatives
and analysis, and impact assessment and cost estimate preparation. The preferred concept at Highway 101 and
41 is described below and the key study findings are summarized in Table 1 (on the following page). It is
anticipated that the proposed projects would follow a state - funded project development path.
The preferred concept at Highway 101 involves constructing a 3,080 -foot land bridge within the existing
MnDOT right -of -way. The proposed bridge width is fifty -six feet; this includes: twelve -foot travel lanes,
eight -foot outside shoulders, and a twelve -foot trail with barrier separation from traffic. The existing bridge on
the north end of the crossing (MnDOT Bridge No. 10007) would be removed for the construction of the land
bridge. The existing road immediately north of the proposed land bridge would be raised to a minimum
centerline elevation of 724.0 feet. With this land bridge, the roadway closure elevation for Highway 101
increases from 709.4 feet to 722.0 feet. The conceptual layout and proposed typical sections for the preferred
concept are shown in Figure 3 at the end of this report.
The preferred concept at Highway 41 involves constructing a 1,350 -foot land bridge within the existing
MnDOT right -of -way. The proposed bridge width including concrete barriers is seventy -two feet (same as
Bridge No. 70041 which was designed to carry traffic while under construction). The proposed bridge width
includes: twelve -foot travel lanes, eight -foot outside shoulders, and a twelve -foot trail with barrier separation
from traffic. Bridge No. 70041 (low steel = 716 feet) would be replaced to avoid concerns over carrying
traffic while partially submerged. With this land bridge, the closure elevation for Highway 41, which is
controlled by the low steel on Bridge No. 10012, increases from 714.6 feet to 719.6 feet. The conceptual
layout and proposed typical sections for the preferred concept are shown in Figure 8 at the end of this report.
As this was a feasibility level study, further refinement of the concepts to a more developed design level
should be undertaken to minimize any potential adverse impacts, while retaining the benefits of reduced
frequency and reduced duration of roadway flooding and closure. Findings of this study will be used by
MnDOT to pursue flood mitigation funding in the fall of 2011.
Minnesota River Flood Mitigation Study Final Report - DRAFT MNTMD- 115709
Executive Summary (Continued)
E.S. Table 1 — Key Study Findings
Com Elements of
Proposed Land Bridge at Highway 101 Proposed Land Bridge at Highway 41
Existing (2009) ADT
20,400 vehicles per day 12,500 vehicles per day
non -flood conditions
Forecasi (203 ADT
24 760 vehicles day, 20 2b0 vehi 1es day
-rion -floods conditions).
per , per
A
Current Closure
709.4 feet 714.6 feet
(Typically the first bridge to close and last to open with (Typically the second bridge to close and opens before
Elevation
hi her maintenance restoration costs than Highway 41 ) the Highway 101 river crossin
Proposed Closure
feet
722
�(gpproaces the 50 =year #loptl waft suifaee elevatron
Elevation
(Exceeds the 100 -year flood z ater surface elevation)
_; of 720 3 feet
56 feet with concrete barriers 72 feet with concrete barriers
Proposed Bridge Width
(Includes 12 -foot travel lanes, 8 -foot outside shoulders, (Includes 12 -foot travel lanes, 8 -foot outside shoulders,
and 12 - foot trail with barrier separation from traffic ) and 12 - foot trail wit barrier separation from traffic
The conceptsre lueed the flood`elevations of tKt mpst, 'requent Roods and tnefeased can Yeyance lQr ait,
Hydrodynamic Modelmg °
events There'were no mdicataoo frgm the feasibility inadglmg7to tha# tkiese,cpncpptsm?ay
- Summary ..`
roduce el alien es''that would suggest ' the : s cauld not be ftukhe `d�velo; ed
The concept of a land bridge is supported by the environmental review and permitting agencies since it
Wetlands /Wildlife
would restore wetlands and wildlife movement within the corridor.
Opportunities
Estimated onstrucf4on $ 7inalliori ,A, bkml)ion
7 `
Cosf Zisk
rQ
v
�v120 0
6 l."R i.�a. . � SN P 'f a ..±k .t, �' VMF —
Benefit -Cost Ratio
3.81 3.06
#aging �iid Constrilt�dU�idey Trafc 4 fi1f a1,a Ttme 18 r
_.� Full los e l- Monthluratn
Constriicta[nIi :
The design of the preferred concept supports the The Trunk Highway 41 Minnesota River
planned effort to turn back Highway 101 to Carver Crossing Tier I Draft Environmental Impact
Community
County. The preferred concept would also provide Statement (June 2007) identifies a long -term
Input/Additional
an important connection with a state regional trail replacement solution at the Highway 41 crossing
Considerations
further linking the communities of Chanhassen and that addresses capacity issues and elevates the
Shakopee. bridge out of the 100-year flood level.
Average Daily Traffic (ADT)
Z MnDOT closes these routes when flood waters reach an elevation of approximately two feet below the low road elevation at the crossing.
' Same as Bridge No. 70041 which was designed to carry traffic while under construction.
° Does not include project development
/design costs.
5 A benefit -cost ratio greater than one, means that it is beneficial project.
Mitigation Measures to Ease Congestion Prior to Implementation and/or During Construction
When the Highway 101 and 41 river crossings close, much of the traffic utilizes the U.S. Highway 169 and
State Highway 25 Minnesota River crossings which cause a cascading effect of congestion that affects
regional travel and costs travelers time and money. Although the U.S. Highway 169 river crossing is relatively
new, it does not have sufficient capacity to efficiently handle the traffic detoured during flood - related closures
at the Highway 101 and 41 river crossings. Highways 101 and 41 carry a combined average of 33,000 vehicle
trips per day across the Minnesota River. As a part of this study effort, the study team identified measures to
ease congestion at the U.S. Highway 169 river crossing to mitigate the impacts of detoured traffic resulting
from flood - related closures. The temporary capacity improvement would involve restriping the northbound
segment of Highway 169 to add a lane between Scott County Road 18 and Pioneer Trail (approximate) and
restriping the southbound segment of Highway 169 to add a lane between Pioneer Trail (approximate) and
Highway 101. It also includes minor bridge widening. The temporary capacity improvement is designed to be
a recurring project and would need to be individually let each time that it is needed (for additional information,
please see Appendix X).
MNTMD - 115709 Minnesota River Flood Mitigation Study Final Report
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50 yr - 718.4 feet
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10 yr - 712.0 feet
74
BRIDGE REMOVE EXISTING
Existing Closure Elevation =
709.4'
745
735
70002 3000' LAND BRIDGE BRIDGE 10007
735
725
725
715
715
705
731.0'
EXISTING
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721 9' EXCAVATION
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MN RIVER CROSSING FLOOD MITIGATION STUDY HWY 101 - PREFERRED BRIDGE /FILL OPTION 9/12/2011 SEH
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PROPOSED BRIDGES
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EXISTING RIGHT OF WAY
— — — COISTRUCTIGN LIMITS
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Proposed Roadway/Bridge Low Elevation = 722.5'
REMOVE EXISTING Proposed Closure Elevation = 719.6'
Existing Closure Elevation = 714.6'
745 BRIDGE 70041 1350' LAND BRIDGE BRIDGE 745
735 / 735
10012
725 EXISTING _ — - 725
s �—
715 GROUND
705 /', \ FILL 705 100 yr — 722.5 feet
50 yr — 720.3 feet
718.4' 716.0' EXCAVATION 721.7' 719.6' 10 yr — 714.2 feet
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MN RIVER CROSSING FLOOD MITIGATION STUDY
HWY 41 - PREFERRED BRIDGE /FILL OPTION
9/12/2011
EH
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Project
Limit
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valley State
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State Trail
tA ' N Valley
Estimated Project Distance �`Je< Z
7,930 Feet (1.5 Mlles) � °
0 1,000 2,000 3, 000 3rd A ve' ? N
Fe srh Ave +
Scott County
�. Community Services Division
[SCOU Physical Development Department w TH 101 Trail Crossing
600 Country Trail East s STP Bike Walk Application
Jordan, MN 55352
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Attachment 2:
Project Limits
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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 Couller Boulevard
Phone: 952.227.1400
Fax: 952.227.1404
Planning &
Natural Resources
Phone: 952.227.1130
Fax: 952.227.1110
Public Works
7901 Park Place
Phone: 952.2271300
Fax: 952.227.1310
Senior Center
Phone: 952.227.1125
Fax: 952.227.1110
Web Site
www.ci.chanhassen.mn.us
September 14, 2011
Ms. Nicole Peterson
MnDOT Metro District South Area Engineer
MnDOT Metro District
1500 W. County Road B -2
Roseville, N4N 55113
RE: Minnesota River FIood Mitigation Study — PW067E2
Dear Ms. Peterson:
I would like to thank MnDOT for taking the initiative to study the Minnesota River crossings
in the southwest portion of the metropolitan area. As you know, TH 41 and TH 101 have
flooded several times in recent years, which created significant traffic problems for the
region. It appears the Minnesota River is trending for more frequent flooding and work on
improving the river crossings in this region is necessary. We are very supportive of every
effort to mitigate flooding on both TH 41 and TH 101 and feel both crossings should be
improved;. however, based on the mitigation report, TH 101 shows the greatest short and long
term benefits if only one river crossing can be improved at this time.
Based on the findings of the Mitigation Study, the benefits for making improvements to
TH 101areas follows:
• The TH 101 river crossing improvements have a better cost/benefit than the proposed
improvements to the TH 41 River crossing.
• TH 101 currently carries and is anticipated to carry more traffic than TH 41.
• TH 101 would be raised to a 100 year flood event. The proposed improvements to
TH 41 only raise the river crossing to a 50 year flood elevation.
• The Trunk Highway 41 Minnesota River Crossing Tier I Draft Environmental Impact
Statement (June 2007) identifies a long -term replacement solution at the Highway 41
crossing that elevates the bridge out of the 100 -year flood level.
• TH 101 currently floods more frequently and stays closed longer than the TH 41 river
crossing.
• The regional economic benefits will be greater since the corridor directly connects
two communities.
• The project is compatible with the fixture turnback of TH 101 and turnback funds
could potentially be leveraged as another finding source.
• MnDOT will be able to remove this corridor from its maintenance requirements once
the turnback is complete.
• The investment that MnDOT has recently made to the historic bridge in Shakopee
should be better utilized by constructing a pedestrian bridge with an improved
TH 101 Minnesota River crossing to connect to the LRT Regional Trail and the local
trail system on the Carver County side of the river.
Chanhassen is a Community for Life - Providing for Today and Planning for Tomorrow
Ms. Nicole Peterson
September 14, 2011
Page 2
• Hennepin County is planning to make improvements on Flying Cloud Drive to make
it more flood proof in 2015. These improvements will benefit the TH 101 Minnesota
River crossing.
• The length of time to construct TH 101 is shorter than the TH 41 improvements.
Improvements to the TH 101 corridor are a high priority for the City of Chanhassen, as it
would provide long -term benefit to the region and improve the state's trunk highway system.
For these same reasons, the City also supports designing the TH 10I improvements to
accommodate a 4 -lane design in order to plan for future growth. The City will `be a
supportive partner in this project if TH 101 is selected for finding. The City commits to
assist, in any way it can, by helping to identify and seek out additional finding for the .
project.
On behalf of the City of Chanhassen and its City Council, thank you for your continued
assistance and consideration of this letter expressing our support for the selection and funding
of the proposed improvements to the TH 101 Minnesota River crossing.
Sincerely,
CITYOF CHANFASS.EN
Tom Furlong
Mayor
TF:PO:k
g: \eng \public \pw067e2 hwy 41 eis & river crossing studies \th 101 final support letter with mayor modifications.doc