2019_01-22_PWETCpacket - Laserfiche WebLink

Home

Mark Culver, PE January 17, 2019 City of Roseville Page 8 Modifications to the Proposed Third Lane Project Upon further review of the proposed project SRF identified a slight modification to the project submitted in the proposal to Metropolitan Council where we propose to begin the third lane at County Road B2 as proposed on the east side of the northbound roadway, but then transition to the west side of the roadway north of County Road C to utilize the center median area for the additional lane. There is adequate space in the median area to accommodate this transition and the largest benefit is that the crossing distances of Snelling Avenue for pedestrians at County Road C2 and Lydia Avenue can remain the same. The construction cost estimate for this scenario is $7,498,650. This estimate is substantially higher than the estimate that was completed for the Regional Solicitation process submission. This prompted a more thorough review of the estimates to determine differences and assumptions. Third Lane Cost Evaluation Through our detailed review of the cost estimates it was determined that the major difference is relative to noise walls. Current construction cost estimates for the project without the noise wall is $2,516,250, which compares to the 2016 estimate of $2,037,865 that was submitted in the proposal. However, further review of the noise wall estimates noted significant differences. SRF's current cost estimate carries a noise wall construction cost estimate of $4,982,400, as shown in Figure 8, which is higher than the $1,360,000 noted in the Regional Solicitation submittal. We believe that this is likely a result of two factors: 1) the assumed cost of the noise walls. (MnDOT'S 2017 noise requirements assumes $36 per square foot for a concrete post and panel noise wall); and 2) the assumed length of the noise walls 1) Assumed Cost of Noise Wall. In 2016, MnDOT assumed a $20 per square foot estimate for a concrete post and panel noise wall. 2) Assumed Length of Noise Wall. In addressing length of noise wall, we conducted a high- level noise estimate utilizing a tool developed by MnDOT for their use with their stand- alone noise barrier program. Estimated levels on the east side ranged from 65.2 dBA (Leq.) to 68.6 dBA (Leq.). The Federal noise abatement criterion for residential land uses is 66 dBA (Leq.). If noise levels exceed the 66 dBA (Leq.) threshold, then mitigation must be evaluated. If we were to prepare a traffic noise analysis for the Snelling Avenue third lane (i.e., year 2040 Build volumes for the worst noise hour with the additional lane), we would expect to see noise levels exceeding 66 dBA at residential uses. On the west side of Snelling Avenue there is uncertainty about the need of a noise wall between Asbury Street and Glenhill Road. The tool estimates noise levels of 64 dBA (Leq.). Depending on the 2040 traffic volumes used in the analysis it may be possible that a noise wall would not be required. For this level of review we have assumed a worst case scenario for wall construction and included possibility of needing almost 6900 feet of wall in our construction estimate. It appears that the regional solicitation submittal had assumed 3400 feet of wall.