The final proposed design includes raising the curb height by 2 inches and placing three lateral pipes to convey water from the road to Spruce Avenue Wash. A schematic of the design can be seen in Figure 1 below. The pipe type will be Spec Dual Wall CMP - 18 Guage, Steel-Lined, Polymer-Coated, with a diameter of 24 inches. The design was created per the standards contained in the Coconino County Engineering Design and Construction Manual, the City of Flagstaff Stormwater Management Design Manual, and the Coconino County Drainage Design Criteria Manual.
Figure 1: Proposed design. Includes three lateral pipes and raising the curb and gutter by two inches along the entire road.
Flow Details
A gutter analysis was done in FlowMaster to determine an intercepted flow of 17.8 cfs. The pipe flows should not be much less than the intercepted flow or there may be flooding occurring at the gutter. Table 1 below contains the flows that were found for each lateral pipe using FlowMaster. Lateral 2 has a flow slightly below the intercepted flow at 17 cfs, but this is not significant enough to overflood.
Table 1: Flows found for each lateral using FlowMaster.
Curb Detail
The curb along Grandview Drive will be increased by 2 inches along the entire road. The curb will be constructed per MAG Standard Detail 220-1 Curb and Gutter Type C but will made to 6 inches instead of 4 inches.
Figure 2: MAG Standard Detail 220-1. Available: https://azmag.gov/Portals/0/Documents/MagContent/2020_MAG_Uniform_Standard_Details_for_Public_Works_Construction_DETAILS.pdf
Stormwater Drainage Inlet Design Detail
The catch basin inlets will be constructed per MAG Standard Detail 537, Catch Basin Type G. The dimensions of the catch basin are 29 inches by 58 inches.
Figure 3: MAG Standard Detail 537. Available: https://azmag.gov/Portals/0/Documents/MagContent/2020_MAG_Uniform_Standard_Details_for_Public_Works_Construction_DETAILS.pdf
Concrete Casing Detail
The lateral pipes include between 18 to 20 feet of concrete casing at the inlets because they did not reach the minimum depth of cover of 3 feet. The concrete casing is there for extra strength since there is not enough dirt cover between the surface and top of pipe to protect it. The concrete casings will be constructed per MAG Standard Detail 507 Encased Concrete Pipe (For Shallow Installation).
Figure 4: MAG Standard Detail 507. Available: https://azmag.gov/Portals/0/Documents/MagContent/2020_MAG_Uniform_Standard_Details_for_Public_Works_Construction_DETAILS.pdf
