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before it reaches Bennett Avenue and convey it underground to Cripple Creek. Runoff which cannot be intercepted before reaching Bennett Avenue will be intercepted by the storm sewer system on Bennett Avenue. The de~ign intent of the ,torm sewer system was to intercept and convey, by underground piping, all runoff within the commercial (downtown) and business area associated with the to-year design storm. N~o, runoff in the downtown area associated witlJ the l()()-year design storm would be intercepted to the point that flows remaining in the streets would not overtop curbs and create flooding of property outside of the public right-of-way. To meet the preliminary design intent of this Drainage Master Plan, the following are recommendations for structure improvements \\ithin the Second Street tributary. 1. Existing structure no. 23 (12-inch CMP with 2-foot of headwater) 1S inadequate to convey runoff from the to-year design storm. It 1S recommended that this culvert be replaced with a 24-inch CMP with a minimum of 3-foot of headwater. 2. Existing structure no. 22 (size unknown, clogged and damaged) must be replaced with a size adequate for conveying runoff from the 100year design storm. It is recommended that a 24-ineh CMP culvert with a minimum of 3-foot of headwater he in,talled at this location. 3. Existing structure no. 92 (I8-inch CMP with 2-foot of headwater) is inadequate to convey runoff from the ro-year design storm. It is recommended that this structure be replaced with a 22"x36" arch CMP with a minimum of3-foot of headwater. 4. Existing structure no. 91 (size unknown, clogged and damaged) must be replaced with a eulvert capable of conveying runoff from the to-year design storm. It is recommended that a 24-inch CMP culvert with II minimum of 3- f(lot 'lfheauwater be installed at thh location. VI-7 5. Existing structure no. 21 (36-inch CMP with 3-foot of headwater) is adcquate to convey runoff from the lO-year design storm (capacity equals 32 CFS while to-year design storm runoff equals 29 CFS). This culvert is located at the intersection of 2nd Street and Golden Avenue and discharges into a poorly developed channel on the west side of Second Street. This area is seen as the location where flooding problems in the business di~trict begin to form dLle to the inability of existing facilities to actually confine and convey storm rLlnoff. To eliminate flooding problems in the business district, it is necessary to find the location where those problems start and begin the necessary improvements at that point. This existing culvert is not capable of conveying runoff from storms in excess of the 10-year event. Therefore, flows overtop Golden Avenue and become unconfined on their way southerly towards tlJe business disuict. It is recommended that tlJis existing culvert be replaced with a culvert capable of adequately conveying runoff from the lQO-year design storm event (99 CFS). A 48-inch RCP with a minimum of 60 inches of headwater would adequately convey the required flow. Installation of the 48-inchculvertshouldindude headwalls. 6. Existingstrueture no. 20 (24"x26" arch CMP with 30 inches of headwater) is adequately sized to convey runoff from the IlJ.yeardesign ~tormevent hut is in very poor condition and needs to be replaced. It is recommended that this culvert be replaced with like size and kind. 7. Existing structure no. 26 (36.inch CMP with 4-foot of headwater) is adequately sized to convey runoff from the lO-year design storm event (capacity equals 45 CFS, to-year design storm runoff equals 37 CFS). As stated above for structure no. 21, this culvert is located in an area (intcrsection of Second Street and Eaton Avenue) which is contributing to the downstream Hooding problems in tbe business district. Improvements should he made in this area to adequately intercept the lOO'yeardesignslormrunllff. VI-8