HRA PACKET 06142022 - Laserfiche WebLink

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IV. Hydraulic Push Probe Soil Borings Prior to boring activities, subsurface utility lines will be marked by Gopher State One Call, Minnesota’s on- call utility locating service. In some instances, a private utility locator may be retained to locate on-site and or private utilities. Soil boring installations will be accomplished by hydraulic push-probe boring methodology. Soil sampling will be facilitated by hydraulically pushing an approximate 2-inch outside diameter, stainless-steel rod to the desired test depth. Soil samples will be collected continuously or as needed from each boring for field logging and screening for volatile organic vapor concentrations. To avoid cross contamination of soil samples collected during boring activities, the hydraulic push-probe boring sampling equipment will be cleaned between boreholes utilizing an Alconox solution and rinsed with distilled water. V. Groundwater Sample Collection from Boreholes Groundwater samples will be collected through temporary screened PVC monitoring wells placed in the boreholes. Groundwater samples will be collected from these borings utilizing poly tubing with a check valve or a single use disposable bailer with new line. In some instances, the borehole will be purged with a peristaltic pump and tubing prior to sample collection. Upon collection, groundwater samples will be placed in laboratory-prepared containers and examined for evidence of impacts using visual and olfactory criteria. Samples will be labeled with the same sampling information noted above (see soil sample collection). Immediately following collection, samples will be placed on ice in a field cooler. Samples will be then transported to a Minnesota-certified laboratory with chain-of-custody documentation. VI. Soil Vapor Collection Soil vapor samples will be collected through temporary soil vapor points placed in the boreholes. Vapor samples will be collected from the borings by attaching a vapor tip to the probe, advancing the probe to the desired depth, retracting the rod approximately 6-24 inches to allow for a vapor gap, opening up the vapor tip, and then connecting a length of new poly tubing. The tubing is then purged using a hand pump, and then extracting the sample using a vapor sampling canister following the laboratory’s instructions. Samples will be then labeled with the same sampling information noted above (see soil sample collection). VII. Field Log Preparation Boring logs will be used to document subsurface conditions encounter during the field activities. If the surface is less than 6 inches thick the boring location surface material will be recorded in the “notes” column on the log. The sample interval, recovery, and PID volatile organic compound readings will be recorded for each sample interval. In general, the methods outlined in the Standard Practice for Description and Identification of Soils (ASTM D2488-93) will be used to describe soil. The soil descriptions will be described in the following order: A description of the main soil group within the sample (e.g., silty sand, clay, silt, etc.). If coarse-grained soil (i.e., sand or gravel) is present, then a brief description of the predominant particle grain size(s) (e.g., fine, medium, coarse) will be included. If fine grained soil (i.e., clay or silt) is present, then the consistency based on finger pressure (e.g., very soft = thumb will penetrate soil more than 1 inch, soft = thumb will penetrate soil about 1 inch, firm = thumb will penetrate soil about ¼ inch, hard = thumb will not indent soil, but thumbnail will easily make a mark, very hard = thumbnail will not indent soil) will be included. If another soil group is present in the sample its concentration with an adjective based on the percentages present within the sample (i.e., trace = < 5%, few = 5 to 10%, little = 10 to 25%, some = 30 to 45 %) will be included.