Common use of Geotechnical Design Clause in Contracts

Geotechnical Design. Conduct a geotechnical investigation and develop parameters to support design of the proposed improvements. Work will include completing a subsurface exploration program, laboratory testing, field reconnaissance, pavement visual survey, and geotechnical engineering analysis, design and reporting. A geotechnical report will include a summary of geologic and seismic hazards, site and subsurface conditions, design parameters, and construction recommendations for the improvements listed below. Geotechnical recommendations will be based on the latest ODOT design practices, Oregon Structural Specialty code recommendations, and design inputs recommended by Tillamook County. Design elements include the following: ▪ Cape Kiwanda Parking Lot improvements including a new restroom foundation, pavement, sanitary pump station, utility trenching, sign support footings, civil overlook planned to accommodate sand aggradation degradation, and a retaining wall along Cape Kiwanda Drive. ▪ Methods of maintaining pavement operation at the intersection of Cape Kiwanda Drive, Sunset Drive and Pacific Avenue during seismic events. ▪ Vault toilet excavation and foundation. The geotechnical and pavement investigation shall include the following: ▪ Review readily available maintenance records, as-built drawings, geotechnical reports, pavement design reports, or other relevant documentation relating to the proposed alignment. ▪ Conduct a visual distress survey of the existing pavement, including logging the type, severity, and extent of existing distresses. ▪ ▇▇▇▇ ▇▇▇▇▇▇ locations in the field and coordinate underground utility locating at the boring locations. ▪ Prepare traffic control plans and obtain right-of-way permits from the County. Provide traffic control per the approved traffic control plans during the field exploration work. ▪ Conduct subsurface exploration along project alignment, including: ▪ Up to four (4) geoprobe explorations in the parking area and restroom areas up to a depth of 40 feet below ground surface (bgs). ▪ Complete one (1) geoprobe exploration at the pump station location. Install a 2- inch diameter well to a depth of 20 feet and complete an infiltration rate slug test within the well. ▪ Up to six (6) dynamic cone penetration (DCP) tests will be completed on the subgrade in accordance with ASTM D6951 to aid in the assessment of in situ resilient moduli. ▪ Up to two (2) hand augers behind the existing retaining wall to depths of up to 10 feet. ▪ Up to two (2) cone penetrometer (CPT) explorations to a depth of up to 100 feet bgs or refusal in the retaining wall and intersection areas. ▪ Representative soil samples will be retained from the geoprobe samplers. Upon completion of each exploration, drilled materials will be placed back in the explorations. Any holes in paved areas will be capped with aggregate material and asphalt concrete (AC) cold patch to approximately match the existing pavement section thicknesses. Excess spoils will be drummed and disposed of at an approved location. ▪ Up to one (1) stormwater infiltration test(s) using City of Portland encased falling head procedures, up to 5 feet below ground surface (bgs). ▪ Maintain a detailed log of each exploration, visually classify the soils encountered, obtain soil samples as appropriate for the soil conditions encountered, and observe groundwater conditions in each exploration. ▪ Conduct the following laboratory tests on soil samples obtained from the explorations: ▪ Moisture content tests on up to fifteen (15) samples in general conformance with American Society for Testing and Materials (ASTM) D 2216 ▪ Tests for soil quantity passing the U.S. No. 200 sieve on up to two (2) samples in general conformance with ASTM D 1140 ▪ Atterberg limit tests on up to six (6) samples in general conformance with ASTM D 4318 ▪ Conduct falling weight deflectometer (FWD) tests at approximately 50- to 100-foot intervals. ▪ Analyze the FWD data to back-calculate the in situ resilient modulus of the subgrade soils and the effective structural number of the existing pavement structure. ▪ Estimate traffic loading by calculating equivalent single-axle loads (ESALs) based on traffic data available from the Preferred Concept Plan traffic study and forecasting the ESALs over the design period. ▪ Provide recommendations for design of new pavements in the parking area and at the intersection. Design recommendations will include up to two (2) design alternatives comprised of perpetual pavement design and AASHTO methodologies. ▪ Complete engineering analysis and develop geotechnical design parameters including the following: ▪ Static and seismic design parameters for structure foundations, ▪ Design recommendations for mitigation of dune erosion, ▪ Recommendations for design build retaining wall including global stability analysis. ▪ Provide guidelines related to geotechnical aspects of construction. ▪ Review and provide comments on geotechnical aspects of plans and specifications. ▪ Up to eighteen (18) hours is sufficient to review Task 13 thru 15 deliverables relative to geotechnical considerations. ▪ Site reconnaissance and exploration program is expected to take up to four (4) days, using one (1) mobilization. ▪ No contamination will be encountered at the site. If contamination is found at the site, operations will stop to contact the County for direction. ▪ Utilities will be located using the statewide one-call service and using a private locator. County will provide information available on known utilities within the exploration area.