SR0085267 - Laserfiche WebLink

Home Browse Search

Phelan Development Holly Master Plan - Buildings H & 1 15188.000.006 Geotechnical Exploration on October 21, 2021, CPTs on October 22, 2021, and test pits on November 4, 2021. The exploration locations shown on the Site Plan (Figure 2) are approximate and were estimated by utilizing smart phones with GPS and Google Earth; they should be considered accurate only to the degree implied by the method used. 2.1.1 Borings We observed drilling of two borings at the locations shown on the Site Plan, Figure 2. An ENGEO representative observed the drilling and logged the subsurface conditions at each location. We retained a truck-mounted Mobile B53 drill rig and crew to advance the borings using 4-inch-diameter solid-flight auger methods. The borings were advanced to a maximum depth of 31'/2 feet below existing grade. We obtained soil samples at various intervals in the borings using either a 3-inch O.D. California-type split-spoon sampler fitted with 6-inch-long steel liners or a 2-inch O.D. Standard Penetration Test (SPT) split-spoon sampler. The standard penetration resistance blow counts were obtained by dropping a 140-pound hammer through a 30-inch free fall. The 2-inch O.D. split-spoon sampler was driven 18 inches and the number of blows was recorded for each 6 inches of penetration. In addition, 2.5-inch I.D. samples were obtained using a Modified California Sampler driven into the soil with the 140-pound hammer previously described. Unless otherwise indicated, the blows per foot recorded on the boring log represent the accumulated number of blows to drive the last 1-foot of penetration; the blow counts have not been converted using any correction factors. When sampler driving was difficult, penetration was recorded only as inches penetrated for 50 hammer blows. We used the field logs to develop the report logs in Appendix A. The logs depict subsurface conditions at the exploration locations for the date of exploration; however, subsurface conditions may vary with time. 2.1.2 Cone Penetration Tests We retained a CPT rig to push the cone penetrometer to a maximum depth of about 93 feet. The CPT has a 20-ton compression-type cone with a 15-square-centimeter (cm2) base area, an apex angle of 60 degrees, and a friction sleeve with a surface area of 225 cm2. The cone, connected with a series of rods, is pushed into the ground at a constant rate. Cone readings are taken at approximately 5-cm intervals with a penetration rate of 2 cm per second in accordance with ASTM D-5778. Measurements include the tip resistance to penetration of the cone (Qc), the resistance of the surface sleeve (Fs), and pore pressure (U) (Robertson and Campanella, 1988). CPT logs are presented in Appendix C. 2.1.3 Test Pits We observed the excavation of 12 test pits at the locations shown on the Site Plan, Figure 2. An ENGEO representative observed the test pit excavation and logged the subsurface conditions at each location.We retained a rubber-wheeled backhoe to excavate the test pits using a 3-foot-wide bucket and logged the type, location, and uniformity of the underlying soil. The maximum depth excavated in the test pits was 16 feet. Test pits were marked with caution tape before loosely backfilling with excavated material; locations should be excavated during site grading operations and replaced as engineered fill. ENGEO December 13, 2021 Expect Exceltence