10-03-1988 Planning Packet - Laserfiche WebLink

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nation. An ideal arii for There are no residential the prevailing winds are for approximately 2,500 be excavated during the plastic immediately after analysis (EPA 601/602). iix inches thick. The soil h until it becomes froxec . After the initial month, arameters. After the fint reports will be forwarded cedure, a 2 inch O.D. split s. After an initial set of 6 12 inches is known as the f the relative density of lassified by the crew chief I were then returned to the ation. Logs of the borings rater level information and : the drill hole were made. ■ ■ f.. I. 4 5# t r M ^ • a ^ ■ ■ J 7 • -IJ ;0 lear* • • f a WECQMMENDATIQNS g.l General Delta recommends that a ground water recovery program be initiated due to the contaminant concentrations identified at this site. Based on site hydrogeologk: conditions, we believe that a recovery trench system would yield the best contaminant volumes. We propose to install a recovery trench pump out system at the WSI site as shown in Figure 4. The effectiveness of the trench system win be evaluated. Modifications to the system and/or the need for additional recovery system will be •aesed. g-1 Cancentaal Desitn The cut end of the recovery trench will contain a large diameter lump which will be equipped with a tingle total fluidt tubmenihle pump. The pump will route water from the trench lump to a diffuied aeration lyitem for treatment of volatile organic compoundi. The treated discharge water will then How into the unitary tewer avstem. The conceptual design of the recovery system and the anUcipateo TCE balance of the system are shown in Figure 5. g.3 Recovery Trench Design The recovery trench will extend from near monitoring well MW-2 toward the east to MW-4 (Figure 4). The total length of the trench will be approximately 250 feet and it will have a depth of approximately lg feet. A croa-iectional sketch of the trench is provided in Figure 6. The width of the ttench will be dependent on the slope subility encountered during the excavaUon. Drain tile will be placed near the bottom of the trench to enhance drainage toward the sump. The trench will be backfilled with coarw washed gravel to a depth of approximately five feet below the exiting ground surface (Figure 6). A plastic Uner will be placed over the washed gravel to inhibit surface water infiltration and to prevent fine grained materials from entering the drainage bed. The top five feet will be backfilled with ,1... „il removed during the trench installation. Soil removed during the trench installaUon exhibiting contaminant concentrations above five parts per million (ppm) total organic vapors, as detected by the hNu photoioniation meter, will be stockpiled and covered on-site. The recovery sump will be located at the eastern end of the recovery trench and will extend to a depth of approximately 18 feet below the ground surface. The top of the sump will be sealed with a lockable well cover. The sump will consist of a 12 inch casing slotted with 1/8 inch wide by three to six inch long slots cut at 45 degree angles. A cross section of the proposed sump is provided in Figure 7. 7:1 ^7 ■m ^:mmm liA; Mfi tu.. ‘ v<d . A; ■M- ■ -i Interv ffcct) - 4 Conce Sampl Heads clo.81