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<br />Addendum to Rational for Approval Recommendation Page 5 <br />Application for Stone Gravel Pit <br />Permit No. M-97-089 <br />February 17, 1998 <br />(east) perimeter of affected lands and/or treated for sediment by passing through straw <br />bale filter or silt fence prior to leaving affected lands. <br />5. The stream reconstruction plan provided admits that `Ye-vegetation of the stream bottom.../s <br />impractical, and shall not be required nor attempted in the rec/amation phase of the <br />operations".. lnstead, the applicant mere/y plans to tip-rap'the lower end of the stream <br />channel where there is a steeper stream gredient. Review of the application end revisions <br />leave the reviewer to guess the slope of this steeper gradient. Serious analysis of the <br />proposal is not possible due to the paucity of information provided by fhe applicant. /n any <br />event, app/icent provides no assurance that this reconstructed stream on a reclaimed hillside <br />with a supposedly even gradient will maintain its course over time or in any way avoid erosion <br />and siltafion during or after rec/amation of the proposed operefion. <br />The Technical Revision contained sufficient information for DMG to complete its analysis of <br />the proposed channel reconstruction. The purpose of the reconstructed drainage channel <br />is to contain and convey runoff from upland areas through the reclaimed areas. <br />To help clarify what is intended regarding the configuration of the reconstructed drainage <br />channel, DMG has attached a sketch of the proposed channel profile and cross section. <br />Profile and cross section sketches were drawn according to information submitted with the <br />application and available in the public file. The horizontal scale of the profile sketch is <br />similar to the scale of Exhibit F, Reclamation Map. The vertical scale of the profile sketch <br />has been greatly exaggerated to help illustrate the changes in gradient. <br />As depicted on the attached profile sketch, the pre-mining gradient of the un-named <br />intermittent drainage channel is approximately 2.5%. The overall gradient of the <br />reconstructed channel will also be approximately 2.5%. However, removal of material <br />necessitates modifications to affected portions of the channel gradient. <br />Approximately 180' after entering the west boundary of the permit area, the reconstructed <br />channel will comeYfown the 3H:1 V backfilled highwall. This drop includes an elevation <br />decrease of approximately 16', to occur within approximately 48' horizontal distance. <br />Slope =rise/run = 16'/48' = 0.33 or 33% <br />After the 48' of 33% gradient, the gradient of the reconstructed channel will remain <br />generally consistent at 1.5% for approximately 1,552', where it outlets to the undisturbed <br />section of the original un-named intermittent drainage channel. Total length of the <br />reconstructed channel is approximately 1,600'. <br />Slope =rise/run = 24'/1552' = 0.015 or 1.5% <br />