This news is based on documents MBA received from Missoula County and Montana Department of Transportation (MDT) under the Freedom of Information
Act. It also includes information received from the county’s engineering consultants, HDR.
PUBLIC MEETING #2
The Technical Design Committee (TDC) met June 14 at the offices of HDR Engineering. Project status was discussed, as was the date for the next public meeting. HDR will schedule the second public meeting, now tentatively planned for August 9 or August 11, 2016. Goals for this meeting were not discussed.
WORK IN PROGRESS
As of June 14, there has been no further fieldwork accomplished, but HDR showed bridge alternative designs to the TDC. Seven alternate designs were shown to us. These are preliminary designs, adapted to two crossings shown in this letter as Alignment B & C.
A hydraulics report should be completed during the week of June 21. This report will provide hydraulic feasibility of all 7 current bridge designs. DNRC and FEMA have suggested that the revised floodplain with the hydraulic modeling be submitted to them.
The noise analysis has advanced as far as it can pending selection of the road and bridge alignments. Consideration of the River Pines portion of the route by HDR discovered utilities in the right-of-way. This will require a utility survey to ascertain exactly what utilities are present and who owns them so the designers will know how to proceed. River Pines also requires additional consideration because a meander of O’Brien Creek comes quite close to the present roadway, and the elevation at the Big Flat Irrigation crossing is a key element in determining the elevation for the new bridge.
ROAD WIDTHS
Missoula County has asked that the bridge and approaches be designed for minor collector standards. That means a 32′ paved surface for the roadway, which allows for 12′ driving lanes with 4′ shoulders. Kona Ranch Bridge is a 32′ bridge with an additional 5′ walk and barrier.
ENVIRONMENTAL REPORT
The environmental report can not be completed until the preferred alternative alignment and bridge configuration have been determined. HDR reported to the TDC that the environmental document will not be complete in time for Public Meeting #2
RIVER ACCESS
This discussion centered around the new replacement bridge as well as removal of Maclay Bridge. The primary question was •How will access be provided without encouraging excessive use, loitering, etc. What restrictions will be in place, enforcement, etc. Though access routes and restraints were briefly mentioned, there was no conclusion and the discussion remains open for comment. Comments should be prepared for the Second Public Meeting.
ALIGNMENTS
HDR provided an overview Alignments A-E; narrowed to B and C. B is most direct other than A but reduces impacts to O•Brien Creek. Alignment C has gradual curves but crosses river at a perpendicular angle. Alignments B and C have been renamed Alignments 1 and 2 for future reference.
Missoula County doesn’t have specific standards for bridge width. MDT minimum for an off-system bridge is 28ft. Given the length of bridge and consideration to snow removal and drainage, a 32-ft minimum bridge roadway is proposed. Sidewalks/shared use path/additional shoulder widths have not been determined yet.
For the purpose of estimating costs, a 43-ft bridge deck width without walkways is assumed.
PREFERRED ALTERNATIVE
HDR’s preferred alternative is called Alternate 1B. It is a four-span welded plate girder bridge with spans of 160′, 200′, 200, and 160′, for a total of 720′. It offers a tangent (straight line) alignment and girder depth is within capabilities of local fabricators. It would require two piers in the active channel. It is the lowest cost alternative. Construction cost is estimated at $12,100,000.
Alternate 1A is similar and has one fewer piers in the active channel. Its cost is estimated at $14,400,000. Alternates 2A and 2B are similar in design, but alignment places a horizontal curve on the east bridge end.
Other alternates include several “Fracture critical” designs.
