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HomeMy WebLinkAbout11-30-2004 Worksession Packet CITY OF OAK PARK HEIGHTS CITY COUNCIL JOINT WORK SESSION TUESDAY, NOVEMBER 30, 2004, 4:30 P.M. 4:30 p.m. Joint Worksession with City of Stillwater, Washington County and MnDOT Regarding St. Croix River Crossing / STH 36 Reconstruction Project 5:30.m. Adjourn • F • • • SRF CONSULTING GROUP, INC. Transportation • Civil • Structural • Environmental • Planning • Traffic • Landscape Architecture • Parking • Right of Way SRF No. 0034686 MEMORANDUM TO: Rick Arnebeck, Area Manager Mn/DOT FROM: Beth Bartz Principal Brett Danner Environmental Planner DATE: November 22, 2004 SUBJECT: ST. CROIX RIVER CROSSING PROJECT REVIEW OF TH 36 CUT AND COVER CONCEPT • A meeting with Mn/DOT and SRF staff was held on October 11, 2004 to discuss the Cut and Cover Concept (CCC), developed by the Cut and Cover Concept Team, as an alternative to the Trunk Highway (TH) 36 reconstruction presented in the St. Croix River Crossing Supplemental Draft Environmental Impact Statement (SDEIS) (referred to as Alternative F, or the buttonhook concept). The purpose of the October 11 meeting was to discuss access, geometric, water resource, and staging issues related with the CCC and propose modifications to the CCC to address those concerns. It was decided at this meeting that each attendee from Mn/DOT and SRF would review the CCC independently and provide a critique of the CCC. This memorandum is a compilation of these comments. General Assumptions The CCC has several conditions that were previously considered unacceptable by either the adjacent communities or Mn/DOT, including: • Depressing the TH 36 mainline, reducing visibility from TH 36 to adjacent businesses; • One -way frontage roads creating more circuitous paths to frontage road businesses; and 1 The Cut and Cover Concept Team consists of area volunteers who, according to information provided by the Cut • and Cover Concept Team, "worked with highway designers, engineers, hydrologists, city and county staff and Mn/DOT to create a concept that satisfied all the PAC requirements but one ". One Carlson Parkway North, Suite 150, Minneapolis, MN 55447 -4443 Telephone (763) 475 -0010 + Fax (763) 475 -2429 + http: / /www.srfconsulting.com An Equal Opportunity Employer Rick Arnebeck - 2 - November 22, 2004 Mn/DOT • Significant additional cost. 411 For the purposes of this technical analysis, these conditions were assumed to be acceptable by both parties. However, these issues will require further consideration as reconstruction is discussed. Review of the Cut and Cover Concept Any concept depressing the mainline of TH 36 through this area will face a number of challenges including profile /vertical distance concerns, the ability to squeeze multiple access points and required safe weaving distances into a 1.5 mile corridor, and storm water treatment concerns. In addition, traffic volumes on local streets as well as the interaction between TH 36 access and property access on the frontage road system provide an additional set of challenges. Finally, construction staging of a depressed facility is more challenging, particularly when it is assumed that traffic through the area and access to businesses is to be maintained during construction. A general discussion of these issues is provided below, including recommended modifications to the Cut and Cover concept. Vertical issues: the vertical difference between the elevation of the mainline and the elevation of the frontage road, and maximum acceptable grades for the ramps connecting the two roadway systems, create vertical distance needs that must be accommodated in the design. Specifically: • The ramp length needed to make up the 22 feet difference in elevation between the 110 mainline and the frontage roads, assuming a maximum 5% grade, would be 440 feet plus additional length to take into account the vertical curves needed to provide adequate landing areas at the top and bottom of the ramps. The slip ramps shown on the CCC are 200 feet to 300 feet long. Additional study would be needed to determine if these ramp lengths can be accommodated, or if the number of ramps must be reduced. • One approach to address this issue would be to have the TH 36 profile "rollercoaster" somewhat in order to sag and pass under the tunnel areas where 25 feet or more of vertical clearance will be required between roadways in order to accommodate the necessary structure depth and then crest where the very short slip ramp connections are shown. Some "rollercoaster" vertical alignments of the frontage roads may also help reduce this problem. The critical areas are where the slip ramp connections are shown. Because of their short effective lengths (one is as short as 200 ft.), the frontage roads and mainline roadways will have to be at similar elevations. The vertical alignment of all roadway elements must be more developed to fully understand the options and understand the potential interaction with tunnel clearances. • The steep bluff grades east of Osgood and interaction with the TH 95 interchange ramps also provide a unique challenge. The CCC ramps east of the government center access probably would be too steep in grade to construct, or will cause a weaving conflict or necessitating a braiding solution with the TH 95 ramps. The TH 36 grades are too steep 2 The mainline depth would be need to be 24'4" — 28'4" (16'4" clearance requirement; 6' structure depth; 2' • minimum cover to 6' maximum cover), not 22 feet as proposed by the CCC Team. Rick Arnebeck - 3 - November 22, 2004 Mn/DOT • for the profiles to work together. Those ramps probably would need to be shifted to a location west of Osgood, further requiring re- examination of the frontage road system design at this end, or elimination of these ramps. Horizontal issues: Required distances between ramp merge and diverge points combined with required ramp lengths, as well as interaction between the ramps and tunnel areas, establish constraints for the placement of these elements within the corridor. • A weaving analysis would need to be conducted to determine minimum distance between merge and diverge points, and lane adds /drops. • Auxiliary lanes could be used to address weaving concerns, but would add to the overall width of the roadway cross - section. Roadway Width/Typical Section: Cross sections should also consider staging and construction needs as well as the finished configuration, particularly when the goal would be to construct a depressed facility while maintaining traffic flow through the area, and are discussed further in a following section. • The future typical of this total roadway segment would need to be well thought out as additional width at a latter time would be difficult to provide. • The mainline typical section should be 114 feet per the requirements of the Mn/DOT Road Design Manual to meet safety and design standards assuming auxiliary lanes are needed per the above discussion (the CCC includes a mainline width of 92 to 100 feet). (Note: if auxiliary lanes are not needed from a weaving analysis, this amount of width may be needed in any case to accommodate construction staging needs.) This cross section width assumes a median barrier, instead of a planted median to conserve on width. A planted median would require an additional 15 to 20 feet at a minimum. • Adequate cross section width would be needed in the tunnel area to accommodate a central median support for the tunnel roof, adequate clear zone from tunnel walls and snow storage. The clear zone requirement for a 65 mph design for TH 36 (as proposed by the CCC Team) is 32.5 feet which can be met by providing 10.5 feet from the face of the curb on the outside shoulder to the tunnel or wall face (which would also accommodate snow storage) in addition to a 10 -foot shoulder and a 12 -foot travel/aux. lane. If a 45 mph design speed is considered, the 17 -foot clear zone requirement can be met by the 12 -foot travel lane and 10- shoulder; however, it is still desirable to have a minimum of 10 feet of snow storage outside the shoulder area. Thus, for either a 45 mph or 65 mph design speed, each tunnel portal (one direction only) would be approximately 67 feet from outside face to median support. Slip Ramp cross sections: • The concept needs to reflect the probable use of retaining walls on both sides of the access ramps. 3 Mainline typical section: 10 -foot outside shoulder, 12 -foot auxiliary lane, 2 -12 -foot through lanes, 10 -foot inside shoulder, 2 -foot barrier, 10 -foot inside shoulder, 2 -12 -foot through lanes, 12 -foot auxiliary lane, and 10 -foot outside shoulder. Rick Arnebeck - 4 - November 22, 2004 Mn/DOT • The slip ramps between the walls need to be a minimum of 28 -feet wide to meet clear zone requirements. This does not allow for a minimum of 10 feet for snow storage — to meet this requirement, the slip ramps should be 32 -feet wide. The slip ramp width provided by the CCC Team is 20 feet. Frontage road cross sections: • The frontage road would need to be two lanes wide in weaving segments between ramp noses and Texas turns and probably two lanes through the corridor. Turn lanes would need to be provided, especially on major turns and on some of the intersecting roads. This would conform to construction staging needs. • The minimum requirements for State Aid are 2 -12 -foot lanes with 2 -foot shoulders for a 30 mph frontage road. The trail width minimum is 8 feet for a pedestrian/bicycle facility, with 10 feet being the preferred dimension. The 4 to 6 -foot wide boulevard suggested by the CCC Team is appropriate. Assuming that the frontage roads will stay in their current location, there may be some areas where right of way taking will be necessary to provide width for a trail if that is desired. • Distance between the frontage road edge and the tunnel wall locations would need to be carefully planned to allow for the construction of the wall foundation while traffic is on the new frontage road (see discussion below.) A minimum of 20 feet would be needed to accommodate an estimated 15 -foot foundation "toe" and allow for construction activities. Drainage: Due to the elevation differences between a depressed mainline and the normal water • level of several existing or proposed ponds, these ponds could no longer be used for storm water treatment or attenuation. In addition, at least two existing storm water pipes that cross the TH 36 corridor to ponding locations would be severed by the depressed roadway. These changes would result in significantly larger storm sewer pipe and treatment ponds or other best management practices (BMPs) below the bluff. Furthermore, storm sewer pipe, in certain locations, will be very deep. While the cut and cover option is physically possible from a water resources perspective, this will result in additional right of way and wetland impacts as well as present significant construction staging challenges. Construction Staging: The sequence of construction activities needed to maintain general traffic through the area during the construction period will be complicated and involve a minimum of six construction seasons. While traffic through the area could generally be maintained, access to /from TH 36 and/or frontage roads could be limited for extended periods of time, particularly in close proximity to cross streets. • One staging approach would be to close the three existing signalized intersections one intersection at a time. This would leave two points to cross the TH 36 corridor. Construction would need to start at Osgood Avenue and progress to the west, allowing the drainage system to be built along with the roadway to maintain drainage. • Each cross street closure would construct the half of the roadway system (either eastbound [EB] or westbound [WB] first), then the other direction. In constructing each half of the roadway, both EB and WB TH 36 traffic would be moved to the two lanes of • existing TH 36. Frontage road traffic would be moved to the remainder of TH 36 and the • Rick Arnebeck - 5 - November 22, 2004 Mn/DOT • frontage road would be reconstructed during one season. Following reconstruction of the frontage road, frontage road traffic would be moved from TH 36 to the new frontage road. At this point, one half of two tunnels are constructed the following season (perhaps requiring multiple contractor teams). With half of the tunnel complete, TH 36 traffic would be moved to the completed tunnel portion; frontage road traffic would be moved to the remaining portion of old TH 36 and the process repeated for the other frontage road. When the frontage road is completed, frontage road traffic is moved from TH 36 to the new frontage road and the remaining section of TH 36 is reconstructed. The second side of the tunnel construction would then be completed in the third construction season. • This process is then repeated for the remaining cross streets (Oakgreen/Greeley and Washington/Norell). Temporary connections would be needed to connect the newly constructed roadways to existing TH 36 and frontage roads. • The frontage road sections on top of the tunnels would need to be configured temporarily to operate as two directional frontage roads until completion of all the tunnel sections. Following completion of the tunnel construction, the new frontage roads would need to be converted from their existing roadway network connections to the new one -way system. • Access to /from TH 36 during each of the construction seasons as well as individual property access would require extensive study. Tunnel construction is divided into two seasons to avoid having all three cross streets closed at the same time. Intersection Geometrics and Traffic Controls: Traffic movements between local streets, two - way frontage roads, and a one -way frontage road system must be carefully studied to ensure safety and traffic flow and avoid driver confusion. A number of geometric deficiencies regarding turning radii, intersection approaches (particularly to the roundabout) and channelization were noted during the concept review. Further traffic study is needed to ensure the proper number of through and turn lanes are provided and problematic queues are avoided. This issue could be addressed through further design study, but will probably require more physical room in the roadway system to resolve. Potential Impacts to adjacent properties: Addressing the above issues will likely result in additional impacts to adjacent properties: • Additional ponding requirements below the bluff may result in additional impacts to a high quality wetland adjacent to the St. Croix River. The US Army Corps of Engineers and USFWS have previously expressed concerns about any impacts to this wetland. • The south frontage road alignment from the government center appears to go into the Xcel Energy flyash landfill. It also appears that the tunnel and south frontage road east of Osgood Avenue would impact Tara Restaurant. Further study is needed to determine the extent of these impacts. • Access/Driveway Locations: Because of the vertical alignment issues, many driveways will need substantial revisions even if a connection remains possible. There are numerous weaving areas and other conflict points with free flowing traffic with this design concept. Driveways that are located close to these areas will need to be closed or • Rick Arnebeck - 6 - November 22, 2004 Mn/DOT relocated. While this design may ultimately have a smaller physical footprint in order to leave existing business buildings intact, this design may also make access to those same sites unworkable. • Construction impacts: At this time, maintaining access to all properties during the full extent of the 6+ years of construction appears to be a significant challenge and may not be workable. Access to and 'from TH 36 will also be highly restricted during the construction period. Economic impacts to businesses dependent on TH 36 traffic can be expected during this period. Future Analysis Needs • A scaled layout, profile and typical cross sections are needed to better analyze the Cut and Cover concept. • Detailed traffic operations analysis is needed to better understand lane needs and intersection configurations. A weaving analysis is necessary to understand ramp spacing needs. • Geometric details, including channelization, need to be refined. • Emergency vehicle access must be reviewed. • Air quality is a concern with any covered roadways. Final tunnel lengths should be determined to avoid required ventilation. • Routes for vehicles prohibited from tunnels should also be considered. Conclusions • The general consensus among Mn/DOT and SRF staff that have reviewed the CCC is that it is unworkable in its current state. The refinements suggested above would improve the CCC, but may result in fewer access points to TH 36, restricted access from the frontage roads to adjacent properties, and additional right of way and environmental impacts. In addition, the construction period is expected to be long and access restrictions during this time may also have significant economic impacts. BTD H:\Projects\4686\EP\TH 36 alt FCutCover Review \CutCover- RvsdMemo-22nov04.doc • 4 Areas would depend on final locations of ramp noses, u -turns and intersections.