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Northern <br />Coal <br />~ Company <br />Page 2 <br />CMLR July 23, 1980 Memo <br />~v,#acceptable for+, both durable rock and ~valley:.fill's,.`r~ A side issue not explicitly <br />-t ~ ~L..::. ~ {~ <br />addressed in Tor. Pendleton's memo is the requirement in~8-T7:74~~~haf ~;4e~top~~ o <br />d'urabl'e' rock:,fi~lls be sloped 'at 5%.~ Northern's original application (Figures 13.1.2 <br />pa!'`..•r wln:• <br />through 13.1.5) called for 2% slope on top of_the filh orthern,has, charged th <br />~i'gures to 5%as~~~that is acceptable for both valley aad durable rock~'•fillsl(817:'72~(e) <br />and 817.74 (e). <br />,Roadway Construction . <br />., <br />This section addresses two issues. The first is a typographic error on page 13-4, <br />section 13.4.1.4 where the reference to 30 CFR 817.163 (d) (11) should be 30 CFR <br />817.162 (d) (11). The change is noted. The second is that "Pazticulaz caze will have <br />to be exercised if waste materials are utilized in roadway embankment construction, <br />in order to avoid contamination with organic material, coal or coal blossom". <br />~ ~Nor$hernhfs not!~ii'sfa"si'e a+teYi'a~l ex roadv'~a',y'!'eonstru~d therefore <br />concurs with this statement. <br />Fill Site Foundational GeohydroloQ:y-,+ <br />In reviewing the ground water elevations in the report, we aze of the opinion that <br />the ground water levels used in our analysis are applicable, despite the high ground <br />water readings in the area of observation wells Nos. 2 and 3. The current reading of . . <br />P-2 (August 13, 1980) shows the ground water level to be at 8.6 feet below the <br />surface. We aze of the opinion that the previous high levels in P-2 and P-3 aze due <br />to a build up of hydrostatic pressure in a sand pocket underlying the clay'.;` <br />overburden, during a period of high ground water. Fluctuations in the hydrostatic, ro''~•:.. <br />A~; <br />gressure in this azea will vary depending upon the amount of precipitation, surface,' ".` ` <br />runoff and infiltration into the underlying sands. Once construction is stazted and ';,.~.,~.; <br />the diversion trenches aze constructed, the amount of ground water which can,''" <br />infiltrate into this underlying sand seam will be decreased. However, <br />alleviate'any fu~Gure,-increases of ground water in this azea and to ~*even <br />the surface in ,;this azea~~N.orthern will constructoa trench drain'~cor <br />~:;:.,. <br />- .. ~; ,. <br />„ .1~,:~: <br />