Laserfiche WebLink
Ray Lazuk <br />March 19, 2014 <br />Page 2 <br />operation and identify problem areas or areas with limited capacity. The open canals, pipes, <br />culverts, and other interceptor appurtenances were photo- documented and basic <br />measurements were taken to provide a cursory understanding of the system. The 2012 <br />snowpack was one of the lowest on record thereby generating relatively low flow rates in the <br />interceptors, even though the field reconnaissance was performed at approximately the peak of <br />the snowmelt runoff. <br />Phase II: Wheeler oversaw a field survey of the interceptor systems to collect survey data for <br />the canal alignment, cross - sectional dimensions, and profile slope of the interceptors. These <br />data were needed for the planned hydrologic and hydraulic analyses to determine their flood <br />routing capacities. The survey was performed by InterMountain Engineering in August 2012 and <br />consisted primarily of representative cross - sections used to define alignment, invert profile, <br />bottom width, side slopes, bank crests, and culvert dimensions for each system. The survey <br />data were subsequently inserted into an AutoCAD drawing on the Climax coordinate system. <br />The surveyed point files could be provided upon request. <br />Phase III: Wheeler developed a HEC -HMS hydrology model and a HEC -RAS hydraulics model <br />of each system using data from Wheeler's previously developed hydrology models and the field <br />survey. HEC -HMS is a rainfall -runoff model, similar to HEC -1, published by the U.S. Army <br />Corps of Engineers to evaluate watershed hydrology. HEC -RAS is a one - dimensional <br />hydraulics model to evaluate steady -state and unsteady -state hydraulics of open channels, <br />culverts, and pipe systems. These models were used in concert to compare the capacities of <br />the interceptors to the modeled runoff rates from a rainfall event with a duration of 24 hours and <br />an estimated return period of 10 years. <br />Phase IV: Wheeler performed a second field reconnaissance of the interceptor system in 2013. <br />The intent of this phase was to compare the survey data and analysis results with actual site <br />conditions. New information that was identified during the second field investigation was then <br />incorporated into the hydraulics analyses and report. <br />The subsequent paragraphs describe the results and conclusions of the evaluation. <br />