DAVID EVANS & ASSOCIATES - 2015 - Laserfiche WebLink

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Task 3 — Geotechnical Investigation Project Set-up and Coordination Under the direction of the project manager, a staff professional from Converse will set-up the project to provide the services outlined under our scope of work. The assignment under the project set-up will include the following: • Coordinate with DEA and the City representative to schedule the field investigation. • Stake the boring locations prior to drilling. • Notify Underground Service Alert (USA) to clear the boring locations of conflict with underground utilities. • Arrange for a drill rig. Field Exploration: Our field exploration program will include drilling exploratory borings. The purpose of the borings will be to obtain subsurface information and undisturbed and bulk samples of the various soil types for laboratory testing. We plan to drill three (3) borings ranging in depth between five (5) to twenty (20) feet below existing ground surface. The borings will be drilled using a truck -mounted rig equipped with hollow -stem augers for soils sampling, Soils will be continuously logged and classified by the geologist/ engineer in the field by visual examination in accordance with the Unified Soil Classification System. Both undisturbed ring samples and bulk samples of the subsurface materials will be obtained at five- foot intervals, at changes in soil profiles, or where unusual conditions are encountered. The relatively undisturbed ring samples will be obtained using a Modified California Sampler (2.4 -inch inside diameter and 3.0 -inch outside diameter) lined with thin-walled sample rings. The sampler will be driven into the bottom of the boreholes with successive drops of a 140 -pound hammer falling thirty (30) inches, The number of successive drops of the driving weight ("blows") required for one (1) foot of penetration will be shown on the boring summary sheet in the "blow/foot" column. The soil will be retained in brass rings (2.4 -inch in diameter and 1.0 inch in height). The central portion of the sample will be retained and carefully sealed in waterproof plastic containers for shipment to the laboratory. Bulk samples of representative soil types will be collected in plastic bags. Groundwater levels, if encountered in the borings, will be recorded. The borings will be backfilled loose with soil cutting. As a result, the surface may settle over time, If construction is delayed, we recommend the owner monitor the boring site and backfill any settlement or depression that might occur, or provide fencing around the area of the boring locations to prevent trip and fall injuries from occurring near the area of any potential settlement. Water Infiltration Tests The five (5) foot deep boring will be prepared to perform water infiltration tests. This will include installing a two (2) -inch diameter perforated plastic pipe inside the boring. Pea gravel filter pack will be poured down the center of the auger while withdrawing the auger to surround the pipe casing and bottom with the gravel filter pack. Water will be added to the bore hole until the water level is as near the ground surface as could be achieved, and allowed to pre-soak for at least two (2) hours. After presoak, we will conduct the test. Each separate trial will be conducted by adding water to the borehole until the water level is at ground surface. The water level will be measured every ten (10) minutes to the nearest 1/10 - foot. At least four (4) sets of measurements will be taken for each test. Attempts will be made to remove the pipe from the boring. If the attempts fail, the pipe will be abandoned in place and the boring backfilled with soils cutting. We have assumed that water will be available on site.