IDOT Southwest Arterial Corridor
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~, 430 S;xteenth Avenue SW FAX, 319-364-9614
P.O. Box 3150, Cedar Rapids, IA 52406-3150
August 29, 2000
Ref: STP-32-1 (I 0)--2C-31
Dubuque County
City of Dubuque
Michael C. Van Milligen
City Manager
50 West 13th Street
Dubuque, IA 52001-4864
SUBJECT: Moratorium on U.S. 20 - Southwest Arterial
Dear Mike:
This letter is in response to your letter dated August 9, 2000 concerning my earlier request for a moratorium of
one year on approving development actions along U.S. 20. This request is based on a proposed Southwest
Arterial connection to U.S. 20 near Seippel Road. In my letter I stated that I would provide limits of the
impacted area when available.
Please find attached the corridor study limits for the proposed Southwest Arterial connection to U.S. 20 near
Seippel Road. The properties affected are identified. Also attached is a letter from our engineering consultant,
HDR of Omaha, Nebraska, which provides a very preliminary environmental review of the proposed study
area. I hope this information addresses your first concern.
The area included in the corridor study limits north of U.S. 20 does exceed the limits for corridor preservation
for the proposed U.S. 20 improvement project. The reason for this is the possible need for a different
interchange configuration than those previously considered (no Southwest Arterial connection). As we
proceed with the location and environmental studies for both the U.S. 20 and Southwest Arterial corridors, we
will continue to better define and, therefore, reduce the area of potential impact. As an ongoing effort, the
limits of the moratorium can also be minimized, which is your second concern.
If the city determines that it has the legal authority to impose the moratorium based on the request of the
department, then I will also ask the county to do likewise. This should answer your third concern.
I plan to attend the City Council meeting on September 5, 2000.
Please contact me at the above phone number if you have any questions.
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Attachment
cc: Anne O'Shea, Zoning, Dubuque County Courthouse
Robert Krause, Transportation Planner, Iowa DOT, Dyersville, IA 52040
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To
Brad Hofer
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From
Will Sharp
Dick Gorton
Randy Graham
Memorandum
Date
August 3, 2000
Subject
DUBUQUE COUNTY
PROJECT NO. STP-U-21 00(12)-70-31, STP-32-1 (1 0)-2C-31
Proposed Study Area - Southwest Arterial Junction with U.S. 20
A brief environmental review was conducted of the proposed interchange alternatives of the
Southwest Arterial junction with U.S. 20 in the vicinity of Seippel Road, and is documented
below. Wetlands and floodplain issues were evaluated. Based on the conceptual interchange
design and environmental review completed to date, we propose the study area on the attached
figure. The study area was developed by overlaying the various concepts developed to date to
determine a worst case scenario. As noted below, all alternatives currently being considered have
varying levels of impact to the Catfish Creek floodplain, and this is anticipated to be a key issue
in the environmental process.
Wetlands Investigation. A field investigation of the site determined that there are no wetland
resources that would be impacted by the interchange. Catfish Creek exists at the site and has a
well defined bed and bank and is, therefore, a 404 jurisdictional water. Some of the interchange
concepts at the site involve relocation of this creek. The Corps of Engineers will view this as an
impact that should be avoided. Consequently, any attempt to pursue an alternative requiring
relocation of the creek will require a demonstration that the other interchange alternatives are not
practical.
The field investigation did identify one problem in conjunction with Seippel Road Extension that
should be corrected. There is a wetland developing at the culvert on the west side of Seippel
Road extension where it junctions with U.S.20. This area is in the process of becoming a
wetland. Although it would not have yet developed hydric soils, the site has developed wetland
vegetation. Unless the city intends this area to become a wetland, drainage should be installed to
prevent ponding. Otherwise, this area will eventually become a jurisdictional wetland.
Attached are captioned photos of the area which show the wetland, Catfish Creek, local drainage,
and the vegetation of other areas. As can be seen from the photos, most of the area has- no 404
regulatory issues.
Floodplain Review. This following is a brief hydraulic review of four proposed Southwest
Arterial alignments with U.S. 20. This review is not intended to be detailed in nature, but a
general evaluation of potential hydraulic advantages and disadvantages for each proposed
concept.
General:
In general all four concepts may require channel modifications, including channel relocation.
The mapping provided reflects a channel that may have already realized channel straightening
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from approximately the downstream portion of the knee of the bend of Catfish Creek, located
approximately in the Southwest portion of the project, up to the next bend situated upstream.
Although channel straightening may lead to channel instability, with upstream migrating channel
bed degradation and subsequent bank sloughing, a relatively short realignment, with design and
construction of appropriate grade control structures, should not present a significant hydraulic
problem. However, channel straightening or relocation is anticipated to present difficulty in the
approval of other permit applications.
A more significant hydraulic impact of any of the four concepts to Catfish Creek will be the
floodplain impact. All four appear to present a potentially large constriction to the available
conveyance capacity of the floodplain. All four concepts appear to eliminate the left (north)
floodplain with the placement of the ramps as well as the highway alignments. The right
floodplain, located along the outer portion of the bend, also appears to have significant blockage
due to the highway alignments.
Such constrictions increase the potential for bridge structure failure due to local scour during rare
event floods at the abutments and piers. Such potential may be mitigated through the design and
construction of appropriate river training and grade control structures. It is noted that the
existing U.S. 20 embankment within the Catfish Creek floodplain does block a significant
portion of the conveyance potential within these floodplains. However, relative to the proposed
alternatives, the existing condition does present a more localized constriction and, subsequently,
less impact to design water surface profiles.
Because construction in the floodplain is required for all concepts, a permit from the Iowa
Department of Natural Resources will be required. As a part of the permit approval, Iowa DNR
will likely want documentation that construction in the floodplain cannot be avoided. This
review will be more critical if the construction is in a designated FEMA floodway.
Should the floodplain be in a FEMA designated floodway, a mitigation channel would need to be
provided, or the floodway would need to be redefined through a public process, in order to allow
the higher regulatory water surface profile. The design of a mitigation channel would appear to
be difficult due to the apparent large compensation necessary for the loss of floodplain
conveyance. The design would need to increase the main channel size, or an improved channel
and floodplain channel, to compensate for the lost conveyance. The design would also need to
incorporate the effects of flow being redirected from the natural floodplain and channel into an
improved floodplain and channel, resulting in additional momentum losses. Such design would
again present difficulty in the approval of other permit applications and present a potentially high
construction cost to provide the mitigation channels.
Concept SW-Al
This concept was briefly reviewed to evaluate the option of shifting the Southwest Arterial east
at the U.S. 20 junction to minimize Catfish Creek impacts. This option would require partial
reconstruction of the Seippel Road extension to tie into the shifted Southwest Arterial alignment.
This concept effectively blocks floodplain conveyance for approximately a third of a mile, from
the exit ramp from eastbound Southwest Arterial onto southbound U.S. 20 to the exit ramp from
southbound Southwest Arterial onto the westbound U.S. 20. In addition, the ramp allowing
eastbound U.S. 20 traffic to exit onto southbound Southwest Arterial also is situated just
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downstream of a bend and is placed in a strong skew position. The bend situation presents
problems in that shear forces are typically tripled along the outer edge immediately downstream
of a bend, increasing the potential for significant scour.
In addition, with the potential loss of floodplain conveyance, the channel will be carrying the
additional flow, further increasing the stream power of Catfish Creek. Finally, the piers will
need to be angled normal to the flow to avoid additional inducement of scour, thus increasing
design costs. It is noted that the most downstream ramp is also placed in a skew position, thus
realizing the same potential for either increased cost or additional inducement of scour.
Concept SW-Bl
This concept effectively blocks floodplain conveyance for approximately a third of a mile, from
the Cousins Road extension to the exit ramp from northbound Southwest Arterial onto the
eastbound U.S. 20. In addition, the ramp allowing eastbound U.S. 20 traffic to exit onto the
Southwest Arterial also is situated just downstream of a bend and is placed in a strong skew
position. The bend situation presents problems in that shear forces are typically tripled along the
outer edge immediately downstream of a bend, increasing the potential for significant scour.
In addition, with the potential loss of floodplain conveyance, the channel will be carrying the
additional flow, further increasing the stream power of Catfish Creek. Finally, the piers will
need to be angled normal to the flow to avoid additional inducement of scour, thus increasing
design costs. It is noted that the most downstream ramp is also placed in a skew position, thus
realizing the same potential for either increased cost or additional inducement of scour.
Concept SW-B4
This concept effectively blocks floodplain conveyance for approximately a third of a mile, from
the exit ramp from eastbound U.S. 20 onto Southwest Arterial to the bridges of the Southwest
Arterial. This concept does not present the bridge obstruction just downstream of a bend as the
previous two concepts, nor does it present a significant skew of the bridges to the stream as the
previous two concepts.
Concept SW-B6
This concept effectively blocks floodplain conveyance for approximately a third of a mile, from
the exit ramp from eastbound U.S. 20 onto northbound Seippel Road Extension to the exit ramp
from northbound Southwest Arterial onto the eastbound U.S. 20. In addition, the ramp allowing
eastbound U.S. 20 traffic to exit onto southbound Southwest Arterial also is situated just
downstream of a bend and is placed in a strong skew position. The bend situation presents
problems in that shear forces are typically tripled along the outer edge immediately downstream
of a bend, increasing the potential for significant scour.
In addition, with the potential loss of floodplain conveyance, the channel will be carrying the
additional flow, further increasing the stream power of Catfish Creek. Finally, the piers will
need to be angled normal to the flow to avoid additional inducement of scour, thus increasing
design costs. It is noted that the most downstream ramp is also placed in a skew position, thus
realizing the same potential for either increased cost or additional inducement of scour.
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Disk I Photo I Facing east toward US 20 from Point 1 on the map
Disk I Photo 2 Facing north paralleling US 20 from Point I on the map
Disk I Photo 3 Facing west away from US 20 down Seippel Road from Point I on the map.
Disk I Photo 4 Facing east toward US 20 from Point Ion the map at the intersection of Seippel Road and
US 20.
Diskl Photo 5 Facing south from Seippel Road along US 20 from Point 1.
Disk 1 Photo 6 Facing southwest from Point I, Looking at a cornfield and small developing wet area at
the base of the culvert.
Disk 1 Photo 7 Facing west along Seippel Road from Point 1 on map.
Disk 1 Photo 8 Facing northwest at Point 1. Looking at culvert under Seippel Road with developing
wetland within 20 feet of culvert outlet.
Disk I Photo 9 Facing northwest at Point L Looking at culvert under Seippel Road from top of US 20
grade, A developing wetland is located within 20 feet of culvert outlet.
Disk 1 Photo 10 Facing south along US 20 from Point I on map, Showing tbe low area between US 20
and the comtleld,
Disk I Photo I. 1 Close up photo of cul.vert on northwest side of Seippel. Road at Point I. on map.
Disk I Photo 12 Facing east. Looking toward US 20 bridge over Cattish Creek from Point 2 on map.
Disk 1 Photo 13 Facing east. Looking downstream at Catfish Creek toward US 20 from Point 2 on map.
Disk 1 Photo 14 Facing east. Looking downstream at Catfish Creek toward US 20 from Point 3 on map.
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Disk I Photo 15 Facing west. Looking upstream at Cattish Creek from Poim 3 on map,
Disk 1 Photo 16 Facing North. From Point 3 looking at low bench area and north bank of Catfish Creek.
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Disk 1 Photo 17 Facing south from Point 4- on map, Looking along ditch that parallels OS 20 to Catfish
Creek.
Disk I Photo 18 Facing southeast from Point 4 on map. Looking toward Catfish Creek from ditch shown
in Disk 1 Photo 17.
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Disk 2 Photo I Facing north looking along the ditch. on the east side of US 20 that tlow$ into Catfish
Creek.
Disk 2 Photo 2 Facing north (away from Catfish Creek) from Point 5 on map.
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Disk 2 Photo 3 Facing south toward Cattish creek from Point 5 on map.
Disk 2 Photo 4 Facing east looking at Cattisb Creek from Point 5 on map.
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Disk 2 Photo 5 Facing south from Point 5 on map. Looking across Catfish Creek into the drainage channel
noted at Point 4 on map.
Disk 2 Photo 6 Facing west from Point 5. Looking at US 20 bridge over Cattlsh Creek.
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Cily Manager's Office
50 West 13th Street
DubuCJue, IOlVa 52001-1864
(319) 589.4110
(319) 589-4149 FAX
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August 9, 2000
Richard Kautz, P.E.
District Engineer
Iowa Department of Transportation
430 Sixteenth Avenue SW
Cedar Rapids, fA 52406-3150
Dear Dick:
The City of Dubuque received your July 17, 2000 letter requesting that the City
Council implement a moratorium for one year on approving development actions
along U.S. 20. At the August 7, 2000 City Council meeting, I was directed to seek
further clarification from you prior to any City Council action.
You should be aware that the City has been contacted by Menards, Ed Tschiggfrie,
William and Janet Siegert, Boogie Nights Tavern and Siesta Motel with concerns
about your request (attached).
On August 8, I received a copy of the attached fax from Bob Krause. While this
provides some clarification, I still have some concerns. First, a map like this would
need to be overlayed on a plat map to make it useful.
Second, we have been told that this moratorium is related to the Southwest
Arterial, which will connect Highway 20 to Highway 61/151, but a significant
portion of property on the north side of Highway 20 is included in the moratorium.
Even though a Corridor Protection Area has already been established for the
Highway 20 interchange and frontage roads that will be needed on the north side of
Highway 20. It is in the best interest of the City to keep the area under
consideration for a moratorium as small as possible.
Third, the moratorium area terminates very quickly to the south at Highway 20.
Will Dubuque County be provided u map with a designated area south of this point
and be asked for a development moratorium.
The note from Bob Krause advises that the information needed to consider this
request will not be available until after August 25. The earliest possible City .
Council agenda it could appear on would be Tuesday, September 5, 2000. For It to
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Highway 20 Moratorium
Page 2
appear on the agenda. I would need it by Wednesday, August 30.
I would appreciate it if you were ablo to attend the September 5 City Council
meeting to answer any questions they might have. The meeting will be held in the
Carnegie-Stout Public Library Auditorium beginning at 6:30 p.m.
Thank you for your assistance in thi~ matter. If you think a meeting with Public
Works Director Mike Koch and I would facilitate this process, please contact me.
Sincerely,
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Michael C. Van Milligen
City Manager
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Iowa Department of Transportation
District 6 Office
430 Sixteenth Avenue SW
P.O. Box 3150. Cedar Rapids, IA '52406-3150
FAX:
319-364-0235
319-364-9614
July] 7,2000
Ref: STP-J2-1(lO)-,.2C-31
Dubuque County
City of Dubuque
The Honorable Terrance M. Duggan, J\hyor
50 West 13ih Street
Dl;buq\lc, It\. 52001-4864
SUBJECT: Iowa 32 - Southwest Arterial
Df.~ar Mayor Duggan'
As I fldviscd YOtl previously, our st<lfT is beginning to evaluate an alternative for the Southwest
Arterial that connects to U.S. 20 in the vidnity of Scippcl Road. As we have reviewed the schcdl'lle
for this pwcess, we have concluded that we will,need about a year to fully complete thlg evaluation.
J would like to formally requc:'lt that the city cuuncil implement v. moratorium for this one.year period
Oll approving development actions (re-zoning, plaIting or building permit applications) along U.S. :20.
At this tin1c, the corridor study limits hav~ not yet been established but should be in the near future.
Once the limits have been cst<.1blished, we can be more definitive as to the impacted area. With
cooperation, we will be able to consider an allcrnative that won't be precluded by development during
the course of the planning study process. Once that process is completed lUld a location is approved,
we can implement official corridor preservation in accord with Iowa law.
If you have any g\lc~lions about this request, ph~BSC give me a call at 319-364.0235.
V cry truly yours,
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District Engineer
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cc: Robert Krause, Tran~port(]lioJl PI<lIlIK'I, Iowa DOT, Dycl"8vil!e, IA 52040
Tom Cackler..Director, Highway Divi:<ion, lowil nOT, Ames, IA 50010