WORK PLANS - Laserfiche WebLink

Home Browse Search

0 • ATTACHMENT FIELD AND LABORATORY PROCEDURES CPT BORINGS The CPT method consists of advancing a cone -tipped cylindrical probe (1.7 inches -in - diameter) into the ground while simultaneously measuring resistance to the penetration. During completion of the CPT borings a Membrane Interface Probe (MIP) will be used to evaluate the presence of volatile petroleum hydrocarbons in soil and groundwater. The CPT method determines soil lithology by comparing the force (cone bearing pressure) required to advance the probe (Qt) to the friction ration (Rf). The Rf equals sleeve friction [Fs] divided by the probe tip load, times the penetration pore pressure [Ud]. Computer generated CPT logs will be plotted in the field that will provide a graphical log of subsurface soil lithology. A CPT test data report, which will include logs of all CPT technique, will be submitted with the final report. CPT testing will be performed in accordance with American Society of Testing and Materials (ASTM) Method D 5778-95 (Reapproved 2000). The CPT will be performed inside a grout collar installed at the ground surface. The grout collar will allow the CPT contractor to backfill the boring as the steel rods are retracted from the hole. Continuous grouting will prevent cross -contamination of water bearing zones that can occur through an open borehole. The boring will be backfilled to surface grade. Grout mix used to backfill the boring will be Portland cement with 5% bentonite. A concrete or asphalt patch will be placed over the borehole where applicable. Soil Sampling Soil samples will be collected at 2-1/2 foot intervals through the vadose zone at the CPT locations using a retractable sampler equipped with two 1-1/4 inch by 6 -inch brass sleeves. Soil sampling is conducted by advancing the sampler to the top of the desired sampling depth. The CPT operator subsequently retracts the rods approximately 12 inches, exposing the brass sleeves in the borehole. The sampler is then driven into the native soil. Select soil samples may be submitted for chemical analysis based on field detection methods (photo ionization detection, odor, and color), or the need to collect specific data. All soil samples for chemical analysis will be retained in brass, stainless steel, or plastic liners, capped with Teflon squares and plastic end caps, and sealed in zip -lock bags. The samples will be placed on ice for transport to a California Certified analytical laboratory accompanied by chain -of -custody documentation. All down -hole sampling equipment will be steam -cleaned following the completion of the soil boring. Down -hole sampling equipment will be washed in a tri -sodium phosphate or alconox solution between samples.