HomeMy WebLinkAboutStaff Report 18A 02/20/1996 FEB 2 01996 18 A .
1 AGENDA ITEM•#
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3 • KEY WORD:,Aiternative
4 Design Payran
5 Bridge
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7 DATE: 2/20/96
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to DEPARTMENT:
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12 Engineering Department-
13 Thomas S. Hargis, Director of Engineering
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15 REOUESTED COUNCIL ACTION:
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17 Provide direction to staff for the alternative design of the Payran Street Bridge.
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19 RECOMMENDATION:
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21 Do not proceed with the currently:defined non-standard geometries due to the liability
22 exposure of the City with thattalternative..
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24 BACKGROUND:
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26 At the February 5, 1996 Council,Me eting staff was directed to pursue preparation of
21 an alternative design for the Payran Street Bridge. This alternative would provide 2-8'
28 sidewalks that could alsorbe utilized by bicyclists. 'There would be 2-12' lanes. This
29 would provide 24' curb to curb for vehicles. This design is in lieu of the completed
30 design which replaces the Payran Street Bridge as is, which includes 2-5' sidewalks, 2-
3 1 8' combined shoulder/bike/parking, and 2-12' lanes: This would provide 40' curb to
32 curb and match the existing'street,approach.
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34 The design firm of'Winzler & Kelly, was directed to prepare an alternative design for
35 bid that would provide for a different bridge structure. As arresult.of that initial design
3 6 effort and staff discussions, several issues have been raised which need to be evaluated
37 by the City Council.
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39 The e most issue i the construction of a bridge that does not meet National, State
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City This i s°a major concern from the viewpoint of Risk Management.
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42 The American Association of State Highway and.Transportation;Officials (AASHTO)
43 Standard e Highway-and g _.. .. roadway width shall
44 generally q ual thelwidth of happroach roadway �ncluding.sh ulder Where c ubed
45 roadway sections approach
a structure, the same section shall be carried across the
46 structure."
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48 Additionally, AASHTO's policy on„geometric design of highways and streets states
49 that, "The minimum Clear width for”all:new bridgesonturban,collector streets with
50 curbed approaches should be the same as.the curb to curb width of the approaches."
51 Caltrans references AASHTO-for standardsunlesstlocal standards suggest a larger
52 width. They also require as a minimum that, "structure shall not be less than 28 feet
53 curb to curb."
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1 The City's collector streettstandardswould provide fora-_40' curb to'cutb;street. City
2 standards'would;require a minimum street width of 28'.feet for reduced minor
3 residential street that serves less than'250 cars per day: `Payran Street carries'closer to
4 8000 cars per day. This narrowed street section would drop`the level of service below
5 "C" which would;not be permitted under the City's..General Plan without either a
6 General Plan amendment, or,la finding that a greater street width is unfeasible.
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8 A second+issue is the potential;costsavings. At the City Council discussion of March
9 5, I had indicated that'll would,cost'approximately $5000'to modify'the plan to narrow
10 the street 3 feet on,each side,by eliminating parking, but maintaining on-street bike
11 path. This was assuming tharthe supporting structure was essentially the same, and the
12 surface depth narrowing would result in savings of approximately $45,000.
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14 Because the proposed new'geometrics are so radically different, and in order to realize
15 any significantly differentrccost savings to the alternative bid, it is necessary to almost
16 start over and design a new bridge, i.e., starting from'the bottom up with supporting
17 elements of piers, girders, up through the,deck`including`seismic;analysis. This is .
18 going to cost.approximately$20,000 rather than $5000. Enough alternative design has
19 been prepared,to estimate that the alterative bid design would probably realize a savings
20 of $116,000 less the re-design cost of'$20,000, results a nettanticipated savings of
21 $96,000. This reduces the construction estimate from $1,900;000 to $1,804,000.
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23 The third item of concern is,impacts of the re-design,on'timing for the project In
24 order to allow time for contractorss;to prepare an alternative bid, the bid date is being
25 postponed from March 5, to Match 12, allowing one more week. This will result in
26 thtbid award'being made on the March 25 special Council Meeting, rather than the
27 March 18 regular meeting. This would still allow for construction starting early in
28 April.
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30 If the Council provides,definitive direction to staff'wecan.;continue to stay on our
31 construction time line. If'theCouncil chooses to pursue other alternatives there is the
32 potential for delaying the construction of the project. In,the wintertime is the best time
33 to obtain good bids on our projects and construction must"be,done during April 1
3 4 through October 30, in order to comply with Fish & Game requirements-for working
3 5 within the Petaluma River.
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37 The fourth item I wish to bringsto the.Council's attention is-that it was not possible to
38 comply with the Council's direction_as far the 12' lane-widths. Because,Payran Street
39 is curved as.it goes over the Petaluma River, it is necessary to have the,lanes be 13 feet
40 wide in order to have a full 12' lane on both ends. For purposes of economy in design
41 and construction, the Payran Street Bridge is a rectangular structure sitting on a curved
42 alignment. This is significantly more economical`than designing and constructing a'
43 curved structure. Therefore, I wanted,to be sure.the Council is aware of our need to
44 design 2113' lanes in order to achieve the 2-1'2 feet of useable space lanes.
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46 ALTERNATIVES!
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48 Continue with the alternativedesign,and bid two alternatives. Drop the,existing design
49 and only bid thealternativegdesign. This may provide more bidder confidence in the ,
50 project, and realize a betterbid.
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2 CONSEQUENCES OF NOT ACTING:
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4 Potential delays in bid opening award construction'time;schedule.,.
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6 ACTION FOLLOWING AUTHORIZATION:• .
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8 Subject to Council direction.,
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10 TSH/slh
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12 xc: de file
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14 Jack Balshaw
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16 psbabd