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E <br /> ai r -a• :ia� -,yam. ¢ .:nr �3-r.ss7: ;l.;i "u�r.,:t t - s Fr^, ','Fx -a <br /> ��,>54� F fls9•����$ -x/a'�"ir hx��4��, � ¢- �.4�.vXR �.N,���''" �`7d'"� k-.�.{i. ��.,�,.ryp `�•�"� <br /> .a^•i __y, <s i z"f.�.- �. ,r � Aw. a2�.,ygr ua- .. ryr �* �, ', . <br /> ���.zr".uS 'kj4"�-.��,,, :x v� ^rtfre:� `,'`l � �" =��.. <br /> Septen113er 13, 1991 <br /> Unocal Station No. 6981, Stockton, California <br /> —........... — -- —� <br /> evaluate in the fold the soil stratigraphy above 75 feet below surface grade before drilling <br /> deeper than 75 feet. proposed monitoring weds S W-6 Ilncunderground ora <br /> llderground stt-7 will be ge(tanksevaluate'and <br /> dissolved hydrocarbon concentrations downgradient <br /> .». d water below i5 feet below surface grade, and proposed <br /> dispenser islands in groun <br /> lved hydrocarbon concentrations <br /> monitoring well 41%V-8 will be used to evaluate disso <br /> upgradient of the underground storage tanks anel dispenser islands. <br /> if soil exhibiting field evidence of gasoline hydrocarbons is encountered in a boring to e <br /> drilled for construction of a deep monitoring well, the boring Will riot be drilled into groilnd <br /> er <br /> water, but will be grouted to surface and a well will not be installed. field evidence of <br /> if field <br /> boring will be drilled approximately 20 feet from the original boring. <br /> gasoline hydrocarbons is not evident, the boring will be drilled into ground water and a well <br /> will be installed in the boring. <br /> If a competent clay layer more than 5 feet thick is encountered below the previous water <br /> levels (below 55 feet) and field evidence of gasoline hydrocarbons is not evident, the boring <br /> will penetrate the clay layer and be drilled to the next water-bearing unit of the water table <br /> aquifer, or to a depth of 75 feet below surface grade. 1f ground water is not encountered <br /> above 75 feet belaw surface grade,we will evaluate in the field the soil stratigraphy above <br /> 75 feet below surface grade before drilling deeper than 75 feet. <br /> Ground-water monitoring wells constructed in the water-table aquifer below 55 feet will be <br /> used to evaluate whether ground water below 55 feel is confined or unconfined and whether <br /> the ground water below 55 feet has a direction of flow similar to the previously detected <br /> t ground water. One sail sample from the bottom of each boring will be submitted for <br /> permeability, sieve, and hydrometer analyses to evaluate the physical properties of the soil. <br /> 38032.4w <br />