Agenda - Council - 10/24/2017 - Laserfiche WebLink

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3. EXISTING CONDITIONS 3.1 Existing Pavement and Soil Conditions The streets were constructed in 1991. Based on results from the geotechnical report and ground penetrating radar (GPR) analysis performed by Braun Intertec, along with field observation, and record plan documentation, the street sections are typically 2.2-inches of bituminous pavement, 4.4-inches of aggregate base, bituminous curb, and a mix of concrete pipe and bituminous flume storm sewer. The streets were constructed to a width of 31-feet from back -of -curb to back -of - curb. The streets are generally centered within a 66-foot wide right-of-way. The only pavement maintenance treatments applied to the street segments were crackseal and sealcoat improvements in 1998. Spot patching has been performed on an as -needed basis, and has been needed more often in recent years as the streets deteriorate. In 2017, Staff observed a PASER of 4 on all the street segments. In July of 2017, City staff recorded a traffic volume of 147 average annual daily traffic (AADT) on Alpaca Street south of 165th Avenue, and 207 AADT on 163rd Lane east of Armstrong Boulevard. The posted speed limit is 30 mph for these street segments. Braun Intertec was employed to complete a Geotechnical Exploration and Engineering Review for this project, which included five (5) soil borings spaced approximately 500 feet along the streets, including one (1) boring at the cul-de-sac on 164th Lane, the intersection of 163rd and Chameleon, and the intersection of 163rd and Alpaca. The locations of the borings are shown in the Soil Boring Location Map in the Appendix of Braun's report, attached in Appendix C. The soil borings provide information on existing bituminous pavement and aggregate base course thicknesses, subsurface soil conditions, existing ground water elevations, and potential issues which may be encountered during construction. All borings terminated at a nominal depth of 11-feet below the existing ground surface. There was no groundwater observed during the soil borings. Based on only storm sewer utilities proposed with this project, depths of which are not expected to reach 11-feet below the existing surface, groundwater is not anticipated to be a significant issue for work completed with this proposed project. The soil borings generally indicate the existing bituminous pavement thickness is 3.0-inches, and aggregate base thickness ranges between 4.0 to 8.0-inches. The subgrade generally consists of poorly graded sand with silt and trace gravel at depths ranging from 2.0 to 11.0-feet below the top of the pavement. Native alluvial soils consisting of poorly graded sand (SP) generally extend to the bottom of the borings. Braun Intertec was employed to complete a GPR Analysis for the project area, which included driving the GPR equipped vehicle throughout all street segments within the project area. In general, the streets had similar results, a summary table and charts of the GPR analysis are attached in Appendix C. The GPR data resulted in an average bituminous pavement thickness of 2.2-inches and an aggregate base thickness of 4.4-inches, with an average total section thickness of 6.5-inches. The minimum total section thickness was found to be 3.4-inches located on Feasibility Report The North Forty Reconstructions City of Ramsey Project No. 18-01 Page 6