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APTIM Work Instruction Number: AMS-830-19-WI-03103 Revision: 0 Approval Date: 8/13/2021 DIRECT PUSH GROUNDWATER SAMPLING ASTM D 4448 Guide for Sampling Groundwater Monitoring Wells ASTM D 4750 Test Method for Determining Subsurface Liquid Levels in a Borehole or Monitoring Well (Observation Well) QED Environmental Systems, Inc. http://www.cledenv.com/sales/hydropunch.html Geoprobe Systems, Inc. http://www.aeol)robe.com USEPA Clu-in. http://fate.clu-in.ora/direct push/dpproundwater.asp 6.0 WORK INSTRUCTION Certified drilling subcontractors typically conduct the pushing or driving of the sampling equipment to the desired sampling depth and associated collection of groundwater samples on APTIM projects. A rig geologist should be present at each sampling event to oversee sampling activities and to ensure that samples are collected from the proper depths and placed in the correct containers following appropriate protocols. All APTIM safety related requirements including those for protection of utilities in AMS-710-02-PR-01610 and for general drill rig safety, AMS-710-02-PR-07200 must be incorporated into subcontractor scopes and adhered to during the activity. 6.1 Design Issues Likely to Affect Sample Quality or Collection Sample quality is easily compromised by poorly selected or applied sampling techniques. Common and avoidable problems include the following: • Use of Unprotected Screens. Use of an unprotected screen creates a likelihood that pore fluid and possibly soil particles that are not from the target depth (final depth) of the screen will pass through the well screen and into the well chamber and be included in the sample. This creates uncertainty as to how representative the sample is of the target horizon. This Work Instruction recommends against the use of unprotected screens. • Excessive Sediment or Particulate Matter within Well Screen. The presence of sediment within samples may bias analytical result, hamper laboratory quality control, or have other deleterious effects. The presence of sediment from an aquifer that is contaminated with an organic contaminant may positively bias (i.e., increase) the concentration results from analysis of organic chemicals, as organic chemicals are typically sorbed onto sediment. The presence of sediment or other particulate matter may also positively bias the concentration results from analysis of metals. This Work Instruction recommends that entrainment of sediment into water within the well screen and the sample be avoided as much as reasonably possible. • Direct push groundwater sampling is commonly used in unconsolidated fine-grained and sandy soils. Problems are encountered when trying to push/drive the sampler through consolidated soils, cemented soils, coble or boulder beds, rubble fill, etc. In addition, some fine-grained beds may not yield water in enough volume to allow sample collection in a timely manner. • The specific sampling methods for collecting the groundwater samples should be developed to minimize disturbance or alteration of the samples. The methods should also allow appropriate or successful sample collection with respect to the expected UNCONTROLLED COPY IF PRINTED Page 4 of 6