09-20-21-WS - Laserfiche WebLink

Home Browse Search

Name: David Swearingen Date: September 15, 2021 Page: 3 A meeting with the Rice Creek Watershed District (RCWD) was also conducted to verify the project’s classification with regard to the watershed’s rules and determine the necessary rules to follow. The project is not considered a reconstruction by RCWD’s definition because the reclaimed aggregate material is proposed to largely remain in place, not exposing the underlying erosive soils. Because the threshold of exposing that underlying soil will not be exceeded, which was confirmed through discussion with RCWD staff, stormwater management (ponds, infiltration basins, etc.) is not required per RCWD. Permitting through the RCWD is anticipated for erosion/sediment control and any wetland impact permitting required related to minor, unrelated drainage work on the Cummings Lane / TH 51 ditch. This confirmation eliminated one significant potential constraint posed in previous iterations of this project development. DESIGN OPTIONS & ESTIMATED COSTS: Based on the information received during our design analysis research, the following three typical section design options were developed for City consideration. Each of these design options have been shown to Metro State Aid office staff and have been confirmed to meet the applicable state aid standards. Option 1 –Existing Rural Typical Section x Matches the existing corridor layout, essentially ‘put back what is out there’ x 8’ shoulder, 12’ drive lane, 12’ drive lane, and 8’ shoulder (40’ total paved footprint) x Preliminary estimated construction cost = $1,071,000 Option 2 –Rural/Urban Typical Section x 4’ turf clear zone, 6’ shoulder, 11’ drive lane, 10’ drive lane, 5’ shoulder, B612 curb & gutter, and 6’ concrete walk (38.67’ total paved footprint) x Preliminary estimated construction cost = $1,244,000 x Provides on-road space for bicycle users and provides an off-road concrete walk for pedestrians Option 3 –Urban Typical Section x B618 curb & gutter, 1.5’ curb reaction, 11’ drive lane, 11’ drive lane, 1.5’ curb reaction, B618 curb & gutter, 2’ bit clear zone, 8’ bit trail, and 2’ turf clear zone (36.34’ total paved footprint) x Preliminary estimated construction cost = $1,261,000 x Provides an off-road shared-use trail for bicycle and pedestrian users In developing the estimated construction cost, a 15% contingency was applied to the ‘option 1’ subtotal, yielding a contingency amount of $140,000. Preliminary estimate contingencies are typically estimates for unknown project risks potentially in the remaining project development process. In this case, the risk between alternatives is relatively uniform, however, application of percentage-based contingencies would serve to amplify cost differences unnecessarily, thereby skewing comparisons. As a result, the same $140,000 contingency was applied to options 2 and 3 rather than a percentage-based contingency. Recognizing the City of Arden Hills typically budgets for a 37% contingency, engineering, and administration figure on projects, similar methodology was applied for the remaining 22% to account for engineering and administration costs. Resulting total estimated project costs are reflected in the attached detailed estimate.