Geotechnical Investigation for the Fix 5 Cascade Gateway Project

Geotechnical Investigation for the Fix 5 Cascade Gateway Project

The California Department of Transportation (Caltrans), using state and federal funding, plans to conduct a geotechnical investigation on Interstate 5 in Shasta County from post mile R13.9 to R23.2. Borings would be drilled at the following post miles: R16.15, R16.98, R22.08, and R18.48. The purpose of the geotechnical investigation is to collect data on subsurface conditions at various locations. The geotechnical investigation is needed because the data collected would be used to evaluate the subsurface conditions to provide foundation recommendations for overhead signs and a communication tower to be installed as part of the Fix 5 Cascade Gateway Project. Subsurface Investigation The proposed subsurface investigation would consist of drilling four borings (see Table 1) within Caltrans’ right-of-way. Borings will not extend deeper than 40 feet below the ground surface. The locations of the proposed borings may shift depending on identification of underground utilities and structures. Access to the boring locations would be from the existing roadway. The total area of topsoil disturbance associated with the geotechnical investigation would be negligible. Table 1. Proposed Locations of Borings Sign # Post Mile NB/CL/SB Depth Lane Closure Type Comments GH 1 R16.15 CL NA None Use GH 2 data GH 2 R16.15 NB 40 feet NB Shoulder 15 feet from FG NB GH 3 R16.98 CL NA None Use GH 4 data GH 4 R16.98 NB 40 NB Right Shoulder 15 feet from FG NB GH 5 R22.08 CL NA None Use GH 6 data GH 6 R22.08 NB 40 feet NB Right Shoulder 15 feet from FG NB GH 7 R18.48 SB 40 feet None 130 feet Rt FG SB FG-Fog Line, NB-North bound, SB-South bound, CL-Center Line, NA-Not Applicable Geotechnical laboratory testing will include corrosion analysis, compressive strength of soil and/or rock samples, potentially Atterberg limits and mechanical analysis. • Groundwater will likely be encountered, based on local geomorphology. • Each soil boring to take 3/4 days working 10 hours shifts (including travel). • Borings will be up to 6 inches in diameter by augers or 4 inches by Diamond Rock core sampling or a combination of both. • Traffic control: Shoulder closure (provided by Caltrans Maintenance or contractor). Drilling Procedures The drilling operations will be performed by a Caltrans drill crew or contracted drilling crew. If the Caltrans drilling crew will be used, a C-57 license and (LEA) permit will be acquired through Consultant Contract services. The drilling operation will utilize a truck-mounted or track-mounted drill rig equipped with a Standard Penetration Test (SPT) hammer will drill off the highway. Drilling will be conducted with a Hollow Stem Auger Boring (with a maximum eight-inch diameter) until practical refusal or groundwater is encountered. If refusal or the presence of free groundwater is encountered before the maximum proposed depth, the Mud Rotary self-casing drilling system (four-inch diameter) will then be conducted to achieve the required depth of the investigation. This mud rotary technique requires the use of drilling fluid to maintain hole stability, bring drill cuttings to the surface, as well as lubricate and cool the drill bit. The drilling fluid consists of water mixed with bentonite clay-based powder and/or liquid polymer. The Safety Data Sheets (SDS) for the bentonite and polymer are available for review. The drilling fluid is contained and recirculated through a closed system utilizing drill rod and a mud tank. The mud tank will be positioned on the surface of the ground and serves as a settlement tank for the soil cuttings, which are periodically removed and placed in 55-gallon steel drums. Once the desired boring depth has been reached, the hole will be flushed with clear water to displace the drilling fluid back into the mud tank. The drilling fluid and water will then be pumped from the mud tank into 55-gallon steel drums for disposal. After the total depth is reached, the boreholes will be conditioned for slope inclinometer or piezo instrumentation or destroyed in accordance with California Water Code and the LEA permit requirements. The 55-gallon steel drums will be removed from the job site and transferred to an appropriate staging area, usually Translab in Sacramento or a nearby Caltrans Maintenance yard. Drilling Equipment Typical drilling equipment consist of truck-mounted or trailer-mounted drill rig, water tender (water truck), and a crew cab with trailer. Also, one or two Engineering Geologist/Engineer’s vehicles are required to support the drilling operation. Schedule Based on the scope of the current project, the drilling operation for this project may take up to 1 (one) week to complete. The drillers work schedule is four ten-hour days, Monday through Thursday working during daylight hours is preferred to perform these drilling operations. Staging/Stockpiling Equipment storage for the drilling operation is typically located at the local Caltrans maintenance yard. Typically, the drill rig, water tender, and trailer are stored at the nearest Caltrans yard at the end of each workday. The support truck and vehicles will be transported off-site at the end of each workday. Disposal/Borrow Sites Soil (“cuttings”) removed from the boring holes would be placed into 55-gallon drums and temporarily stored at a nearby Caltrans maintenance yard or at the Caltrans Trans-Lab facility in Sacramento. The material would then be disposed of at a landfill that has previously undergone environmental review and is approved for use. The geotechnical investigation does not require the use of a borrow site. Utilities No new utilities would be installed and no conflicts with existing utilities are anticipated. Right-of-Way The geotechnical investigation would be performed entirely within Caltrans’ right-of-way. No federal land is present within the project limits. Permits No permits would be needed from regulatory agencies. Coordination/Consultation Caltrans performed a review of resource records and databases and consulted with applicable agencies, individuals, and tribes.

Redding, Shasta Lake

Shasta

Northern California