SITE INFORMATION AND CORRESPONDENCE

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S Joaquin County lEtiviroritnental Heaith(W-jision Recommended Groundwatei Sampling Guidelines :r . San Joaquin County Public Health Services, E=nvironmental Health Division (PH5/EHD) is providing these guidelines to increase the confidence and reliability of the groundwater sample results. Variance from s" these guidelines may result in a lower confidence level and results may not be recognized as representative of actual site conditions: Recommended Procedures 1. All wells should be measured for de th to water D and total de tH Dprior to purging the r7� wells. A water/oil interface probe shouid be used when free product is suspected. Field notes ' should include the condition of the well in and around the traffic box, stove pipe, well seal protection, obvious odors, general site conditions and weather conditions. All requested data Y should be collected in field notes and included in subsequent reports. .M 2. Weils should be purged 'using either a pump that minimally disturbs groundwater or by hand € balling using a hailer. At least three to five casing volumes should be purged, using DTW and -r, - TD measurements io calculate casing volume, or until water from the well has been shown to be , h stabilized, using pH; temperature and electrical conductivity data gathered at frequent intervals before and during the purging process. ' ;R.4. 3. Purging instruments should be decontaminated between wells by thorough cleaning and rinsing between sampling to prevent cross contamination or the'introduction of cleaning agents. 4. After the appropriate volume of water is removed and before a sample is collected, another DTW i measurement should be taken and recorded. If the well has not recovered to 80% of the original s, depth, within a reasonable amount of time ( '? condition should be noted in the field notes. °. .' 5. Wells should be sampled in the order of the cleanest weil.to the most contaminated well, if prior information is available: 6. Volatile, semi-voiatile or non-volatile samples should be collected in the appropriate pre-chilled W ,. containers for the analysis requested. If no preservative is used, then the samples must be arialyzed within 7 calendar days of the date of sampling.` if preservative is used samples must ` .' be completely analyzed within 14 days of the date of sampling. gam: s` 7. Samples should be collected 'using a ballet or a pump t: During sample collection, the volatile d sample container should be filled with no observable air bubbles. No headspace should be present in the sample container once the container has been capped a To avoid dilution of the . Ft _ preservative, sample containers should not be overfilled. Samples'should be collected to minimize contact with the atmosphere to prevent the loss of volatile constituents from the sample. When appropriate travel blanks should be collected. f 4 8. The samples should be stored in an insulated ice chest cooled with ice to ensure that the + };;,i samples achieve 4° C. ^k �* 9. Chain of Custody forms must be complete. Mail couriers must also be noted on the chain of custody and supported with documentation. Chain of Custody forms must be legible. Notation should be made on the chain of custody by the receiving fab indicating the condition and r s: temperature of the samples. ._ t-pumps lased for purging or sampling collection should have good flow controllability to permit low flow f r rates, <100 milliliter per minute, for sampling volatile chemical constituents. pumps should be simple to operate, durable, portable, cleanable and should minimize the physical and chemical disturbance of the groundwater to avoid conditions which would interfere with the collection of a representative sample. I For more information, please contact the site mitigation ON at (269) 468-3450 y Jv 2/i5/95