AgdaPkt 2019-11-25 Joint SA PFA - Laserfiche WebLink

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6.1. - Page 2 of 6 4) Storm drain inlets, manholes, reinforced concrete pipes, and other drainage modifications 5) Excavation, backfill, and compaction 6) Asphalt grinding and overlay 7) Traffic signal modifications 8) Temporary and permanent pavement delineation and roadway markings 9) Roadside signs and markers 10) Existing utility box/cover and fire hydrant adjustments to final grade 11) Restoration of existing landscape, irrigation, and hardscape improvements ANALYSIS As a part of the conditions of approval for the 601 Marshall Street Office Development (Development), the Development was responsible for the construction costs related to the construction of bulb -outs and associated improvements along their property frontage. At the intersections of Marshall Street and Jefferson Avenue and Marshall Street and Middlefield Road, the Developer would be responsible for improvements to one corner of the intersection, and the City would improve the other three corners of the intersection with the Development project paying into the Traffic Impact Fee (TIF) fund/Marshall Street Project. Between the time that the project received the planning entitlements and when the funds were needed, a study was completed that determined that downtown development projects would need to pay substantially less than the previous rates. This meant that the costs for the City's portion of the intersection improvements were significantly more than the available TIF funds, and so the City wrote the provisions for payment and design of the intersection improvements into the Improvement Agreement. This agreement required the developer to deposit $148,951 with the City prior to permit issuance and prepare design drawings for the intersection improvements prior to issuance of a Certificate of Occupancy for the Development. The funds have been paid, and the plans and specifications were prepared by BKF Engineers and used for the bidding of this project. The project designers estimated the existing asphalt concrete thickness on Jefferson Avenue and Marshall Street to be 9 inches. However, the contractor's exploratory potholing throughout the intersection discovered that the existing asphalt concrete thickness is 2" — 3" thinner than the designer's estimate. Verification of the pavement thickness was not performed during design phase because of the smaller footprint of the project (one intersection). On a larger corridor project that spans three or more intersections, staff would have required the designer to verify the pavement thickness during the design phase. The thinner -than -expected asphalt concrete thickness is an issue as the strength of a roadway pavement section is generally dependent upon the thickness of the asphalt concrete layer. The thicker the asphalt concrete layer, the stronger the pavement section. The thinner than expected asphalt concrete layer indicates that the pavement restoration method of 2" grind/overlay specified on the project plans will not provide sufficient strength for the expected traffic load. Additionally, staff identified Page 2 of 4 City of Redwood City 1017 Middlefield Road, Redwood City, CA. 94063 Tel: 650-780-7000 www.redwoodcity.ore 261