1982-03-18_REVISION - C1981013 (3)

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MAXWELL MINE - FILE #C-013-81 TECHNICAL REVISION #1 ADEQUACY RESPONSE This response addresses concerns of the division in the order that the issues were raised in the letter to CF&I dated March 9 , 1982 . Therefore , these responses are numbered 1 through 7 . 1 . The two-foot diameter culverts under the temporary access road will have 2-2/3" x 1/2" spiral corrugations and a gauge thickness of 0 .064 inches . The minimum cover required for an H-20 live load is 12 inches according to the Handbook of Steel Drainage and Highway Construction Products 2nd Ed . ) 108 . CF&I intends to limit the load to H-20 loading. Spacing between each culvert is to be at least one diameter ( 21 ) . According to the above mentioned handbook, the maximum cover allowed for the proposed 2 ft culverts is 124 ft . The plan as submitted calls for 2-1/2 ft of cover over the top of the culverts . 2 . As a check to determine whether inlet control is the limiting Hydraulic Condition for the temporary pipes , the Handbook of Steel Drainage and Highway Construction Products 2nd .Ed. was utilized to determine flow with inlet control . The results were that each pipe should be able to pass 24 cfs under inlet control conditions . This is_ a higher number than the 22 .5 cfs previously given in the original application for technical revision . Figure 4-18 , Inlet Control Nomograph from the above mentioned handbook , was used to predict inlet flow conditions and is included at the end of response #2. The HW/D ratio under maximum flow conditions is somewhat higher than manufacturers recommend for permanent installations . CF&I does not believe this to be a problem because this specific pipe installation will only be in use for a short time .