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~• i Northern Coal I Company OCTOBER 14 1980 ~ I I RESPONSE TO JULY 23, 1980 ~GMLR MEMO ~ C.lassification of the Fill; «I III«~II ~~« ~II The first section of the memo covers the definition of durable rock, the method of determination of durability, the implications of existing tmcertainty as to the nature of the refuse and Mr. Pendleton's feelings as to appropriate measures to be taken with any refuse placed before the completion of durability determinat:~~n. This discussion of the definition and determination ~of durable rock status is quite ' thorough and correct and we have nothing to add to it. r:~.P,endleton contends~~ha• the difference between dura~''le'and nondurable fill. is sign4~fi,cant and)that~as a esul s ~, • ~, s any material which ^lias~'not been established to •be durable must,":,be ~treafed~~ as nondurable (i.e., placed in th~~reeee foot lifts and compacted to 85% ASTM D698 maximum dry density). q~his~is"ta very reasonable lregturement and is~impul~e,,d.in~the H, .f.. ~ 'Panguage of the (application. Northern will•condtrct our disposal operation`in this~~ ~- ~ .. fashion. '• YConfiRuration of?,the Fill Terraces The next section of the memo, again, addresses issues that azise from the question of durability of the fill material. OSM regulation 817.74 clearly states that terraces,. on durable rock fills will slope into the embankment at 5% and that the cross slope ' will be 5%. If the waste material proves out to be durable rock, terraces `'ti. I constructed on the fill in later phases will have to conform to this regulation. It~,~'.~%' should be noted that this is not really an issue in this application, as no terraces are ! :' ' proposed in Phase I. ~igiire'13.1:2 is thereby amended to specify'the~5% terrace Gros ~~ ~:.,., •, ~., . wslopes and 5%~' terrace `slopes into the" embankment' as' this ?'configuration .rts ,~~ri ~$~L~;'. =:;;. i ~ i'!,~'i to ~Y~ui.a;