Projects: Site Assessments & Subsurface Investigations
Borehole Drilling and Logging, Water Supply Contaminant Investigation, Norwalk, CA
As a subcontractor to Komex, Inc., CGC recently directed drilling, lithologic logging and discrete-depth groundwater sampling for multiple boreholes drilled using mud rotary and hollow-stem auger methods in the city of Norwalk. CGC coordinated simultaneous drilling with multiple drill rigs and performed lithologic logging using the Unified Soil Classification System. We worked with Norwalk officials to arrange for permitting, waste disposal and traffic control. CGC interpreted field data and worked with Komex to identify potentially contaminated groundwater zones and likely target intervals for groundwater sampling and well screen placement. CGC documented all field activities and prepared a written summary of field work for Komex for inclusion in a summary report for the client.
As part of this project CGC also supervised geophysical logging of the boreholes. We arranged for a specialty geophysical subcontractor to perform a full suite of gamma and electric logging. Short normal, long normal and point resistivity, spontaneous potential, and gamma logging were performed in the boreholes. CGC interpreted the geophysical results, which were used to help identify likely zones of groundwater contamination and preferential groundwater movement. We documented all geophysical activities and prepared a written summary of the methods and results.
Borehole Drilling and Well Installation, Los Angeles Area
CGC has completed numerous soil borings and installed over 50 groundwater monitoring and vapor extraction wells as a subcontractor to a Los Angeles area oil company. We performed continuous core sampling and interval sampling at locations across southern California using geoprobe, cone penetrometer testing and hollow-stem auger methods. CGC logged the borings and wells using the Unified Soil Classification System and prepared detailed boring and well logs. CGC also prepared work plans, QA/QC plans and technical reports outlining results of the investigations and presenting recommendations.
Aquifer Testing: Industrial Manufacturing Facility Impacted by Chlorinated Solvents in Northern California
Mr. Colby of CGC planned and implemented aquifer tests at a state Superfund site in the San Francisco Bay area. The tests were performed using both manual and electronic data collection methods. The data were interpreted using software-based solution methods (using Aqtesolv) and Mr. Colby prepared reports of aquifer test results. Step-drawdown tests were performed to assess optimal pumping rates prior to starting the constant discharge tests. Aquifer test data were used in the development of a groundwater flow model for the site and to identify the location of a fault line that acted as a barrier to groundwater flow.
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