FIELD DOCUMENTS - Laserfiche WebLink

Home Browse Search

Ms. Marilyn Petruescu September 30, 2024 The samples will be labeled with a unique sample ID and placed into an ice-filled cooler for transportation to a State-certified laboratory under chain-of-custody protocol. Once the total depth of the monitoring well is reached, and depth to first encountered groundwater has been identified, the monitoring wells will be constructed using 2-inch diameter Schedule 40 polyvinyl chloride (PVC) casing and 0.010 or 0.020-slot screen. Based on existing stratigraphic data, it is anticipated that ten-foot screens will be installed from approximately 13-23 feet bgs in each well. After the monitoring well casing and screen are installed in the open borehole, a sand pack, consisting of#2/12 or #3 sand, will be placed in the borehole annular space to approximately two feet above the top of the slotted casing. A bentonite seal will be placed approximately three feet above the sand pack and hydrated to prevent the entrance of grout into the sand pack. The annular space will then be backfilled with neat cement grout to just below ground surface. The monitoring wells will be completed with flush-mounted traffic-rated well boxes and secured with a locking cap. Proposed well construction details are summarized on Table 1. The well locations, total depths, and screen intervals may change in the field based on field observations. Well Development The wells will be developed a minimum of 48 hours after installation by bailing, surging, and/or pumping to remove sediment left in the well during construction and to enhance the hydraulic communication between the well and surrounding formation. Measurements of pH, temperature, specific conductance, quantity, and clarity of water withdrawn will be recorded after each purged well volume. The wells will be developed until approximately 10 casing volumes are removed or until relatively sediment-free water is observed. Well Survey The top of casing elevation, latitude, and longitude for all of the UST wells will be surveyed by a licensed surveying subcontractor. GEO_XY and GEO_Z files documenting the installed wells' coordinates and elevations will be prepared and uploaded to GeoTracker. Investigative Derived Waste Water and soil generated during field activities will be placed in properly labeled 55-gallon drums and temporarily stored onsite near the GSH operated Groundwater Extraction and Treatment System. Once the investigative derived waste (IDW) profile is completed, the IDW will be transported by a licensed hauler to an appropriate off- site disposal facility. Purge water will also be sampled for characterization and disposal. Following review of the purge water analytical data, it will be determined if the water will need to be transported for off-site disposal, or if the Groundwater Extraction and Treatment System can process the water. Site Investigation Report Following completion of the proposed field activities, Arcadis will prepare a Site Investigation Summary and Well Installation Report which will be submitted to the CVRWQCB within 90-days following well development and sampling activities. The report will include site plans, boring logs, well construction details, elevation data, tabulated summaries of laboratory analytical data, and additional investigation recommendations if needed. www.arcadis.com 5/7 Lathrop UST Site Investigation and Well Installation WP 9.30.24_final