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<br />~ <br />. <br /> <br />/. <br /> <br />Mr, Tom Daugherty <br />May 5, 1998 <br />Page two <br /> <br />1) Our understanding is that John Liou ofFEMA has directed that the current FIRM <br />delineation for Sawmill Gulch should be ignored, For that reason, the report <br />contains no map showing the proposed floodplain delineation superimposed on <br />the current FEMA floodplain delineation and matching that FEMA floodplain at <br />whatever location a match occurs. (Since there is flow down the channel and <br />down Four O'Clock Road, there should actually be two match locations,) <br />Concern #2 further elaborates on the question of matches between floodplain <br />analyses, <br />2) The CWCB has not received a clear statement by Foothill Engineering Company <br />anclJor FEMA of the current status of the floodplain restudy effort for Sawmill <br />Gulch downstream of Four O'Clock Road, It needs to be easy for us to <br />understand how the CLOMR floodplain ties in to the proposed FEMA floodplain. <br />Our present understanding is that there really is no hydraulic match on the main <br />channel at the culvert under Four O'Clock Road because the culvert is steep and <br />because there is a drop at its downstream end, We believe FEMA should clarify <br />that question. <br />3) There is, as mentioned in Comment #2 above, no hydraulic match for the main <br />channel profile at Four O'Clock Road. The water surface profile downstream of <br />Four O'Clock Road (to be prepared by Foothill Engineering) is essentially <br />independent of the profile upstream of Four O'Clock Road (already prepared by <br />Wright Water Engineers). There is no profile for the overflow down Four <br />O'Clock Road because the flow is so shallow. There is a water surface profile <br />within Tyra D showing the proposed water surface within the two drainage <br />collection systems, but it stops at the downstream end of the Tyra D site, We <br />presume that the modified FIS will include profiles for the main channel <br />downstream of Four O'Clock Road and upstream of it. <br />4) It appears that there may be a possibility of snow blockage at collection points in <br />the collection systems. Any runoff event that occurs when there is still snow and <br />ice on the ground should be monitored closely and appropriate maintenance steps <br />should be taken, In addition, the possibility that any collection lines might be <br />subject to freezing (inside the pipe) should be considered, Ice inside the pipe <br />could reduce the flow capacity, Our understanding is that there is excess capacity <br />in the pipes, so this problem may be moot. <br />5) The report includes your letter of April 23, 1998, which agrees conceptually with <br />the proposed design, We assume that the Town of Breckenridge believes that <br />continuing the current drainage pattern of overflows down Four O'Clock Road is <br />acceptable, In looking at current conditions, we presume that the current pattern <br />is not just acceptable, but actually desirable, Because of inadequate drainage <br />capacity downstream of Four O'Clock Road, if the overflows were kept in the <br />Sawmill Gulch channel instead of being permitted to go down the road, the town <br />would experience flooding problems further downstream, <br />