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Project.No. 58080-06.02 September 30, 1994 Page,5, bottom of the screen interval to an elevation of two feet above the screen zone.. A two foot.thick seal consisting of hydrated bentonite chips will be placed above the filter pack. Above the seal a mixture of bentonite powder and cement will be placed 10 within two feet of grade level. A minimum 14-inch diameter, traffic-ranted security wellhead cover set in.A. ..concrete pad will be used to complete construction.. Task V Installation of Groundwater Monitoring Wells. Install:offsite groundwater monitoring wells 1'v W4 and NfUV=S in the adjacent public right-of-ways iatthe locat ons depicted on Figure 2. be wells will be installed to depths of 70 feet below the groundwater surface.- The monitoring wells will be constructed using 2-inch; diameter polyvinyl chlorid6 {P' � casing. T'he Lower porion of the:wells will be constructed using 20 feet of A020-inch.: slotted screen PVC casing. A filter pack Consisting of No lviontetey sand will be trimmed around the.screen from the:bottom of the boring to:an elevation of two:feet above the screen zone. A two foot thick seal consisting of hydrated bentonite chips will be; placed above the filter pack. Above the seal a mixture o€ bentonite powder and cement will be placed to within two 'feet of grade level, A minimum 14-inch. diameter, traffic-rated security wellhead cover set in a concrete pad will be used to - complete construction. • The top of casing elevations for the new groundwater monitoring wells will be surveyed relative to the designated temporary benchmark, Task VI - Groundwater Well Development Purgingand nd amplin • No Tess than 48 hours after the completion of well construction, develop the groundwater monitoring wells for approximately 10 minutes (or until turbidity stabilizes) utilizing a surge block,- No less than 48 hours after the completion of well development the depth-to- groundwater will be measured with a electronic water level meter: The water level meter will be cleaned with liquinox solution and triple rinsed prior to introduction intoa new well Tlyree to five borehole volumes of groundwater will be ;purged to allow fresh. format�vn water to infiltrate the wells. During purging, the pH temperature, and electrical conductivity of the groundwater will be measured. • Following purging; water will be collected from each well with a pre-cleaned disposable bailer. Th(i .collected water will be decanted into appropriate sampling Ontainers supplied 6y the analytical laboratory. Upon collection, the sampling containers will be sealed,labeled and placed into an ice-ch ;cooled with blue ice pending:delivery to the laboratory. Samples will be caillected and transported under standard chain-of-custody documentation: