FLOOD05940 - Laserfiche WebLink

Home Browse Search

conduit below. The capacity of this inlet is inadequate and the inlet should be replaced with a new structure. This new inlet should have approximately 6 square feet of open area and be installed in a condition allowing for a minimum of l+foot of ponding depth above the grate. The discussion in Section D, Upper Cripple Creek, concerning development of the Cripple Creek channel bem'een structures holds true for tbis portion of the watershed as well. Also,thedesignguidelinespresentedinSectionC,SecondStreet Tributary, concerning design guidelines for the storm sewer system in Bennett Avenue hold true for storm sewer systent~ in this portion of the watershed. The following recommendations are made for improvements to existing struclllres within the hasins associated witb Cripple Creek and its trihutaries. 6. A new buried conduit is required in the area between existing structur eno.50 and existing inlet no. 104. As previously discussed, once flow enters a conduit, the conduit size ean be reduced beeause headlosses associated with entrance conditions are eliminated. It is recommended that approximately 150 lineal feet of 60-inch RCP be installed at a slope of approximately 4%. Recommendations for replacement of the remainder of this existing conduit will be discussed in Section E, Cripple Creek and Tributaries, of this report. E. Cripple Creek and Tributaries 1. Existing structure numbers 105 and 106 are inadequately sized conduits in extremely poor condition which convey flow from the Main Street Tributary into tbe conduit which intercepts flow from Upper Cripple Creek (location of existing structure numbers 50 and 1(4). The runoff associated with the 100- year design storm event at this location is 605 CFS. To adequately intercept this runoff. it is recommended that an ll'5"x 7'3" arch culvert complete w ith headwall. wingwalls and a minimum beadwater depth of 8'6" be installed. Once the runoff is intercepted by this arch culvert, the conduit size can be redu~'t"d to 60-inch RCP at a minimum slupe of 5%. Approximately 125 lineal feet of60-ineb RCP is required. Cripple Creek and its tributaries, as defined herein. begins at the lower end of Upper Cripple Creek. Cripple Creek flows southwesterly from this point to the confluencc of Poverty Gulch. Cripple Creek then continues to flow in a southwesterly direction through the soU!heasterly portion of the city's eorporate limits to its confluen cewith the Second Street Tributary and the Thurlow Avenue Tributary. At this point Cripple Creek turns and flows in a southerly direction until it leaves the city's corporate limits. Structures within Cripple Creek and its tributary basins are included in two gcneral categories. The first category is major structures in the Cripple Creek channel at road crossings. These stnletures appear to he severely undersized and are in need of replacement. The sccond category of structures primarily deals with inlets and storm sewer components within the husiness district. Again, a majority of these struetures are severely undersized and in need of replacement. 2. ExL~ting structure no. 46 is a continuation of the conduits deserihed above. As Cripple Creek and the Main Street Tributary have combined at this p()int, the design runoff associated witb the loo-year design storm event is 1,1\17 CFS. As with existing structure numbers 50, 105 and 106,existingstructure no. 46 is in extremely poor condition and needs to be replaced. [t is recommended that this structure be replaced with a 72-inch RCP at a minimum slope of 7%. Approximately 450 lineal foot of 72-inch RCP will be required. As an alternative, an open channel approach could be eonsidered. However,because U1eadjacent land uses have enjoyed the use and hencfit of the available land over the existing conduit, it would he a major changc in design and use for the adjacent business properties. VI-15 Vl-16