Data Collection Report - Flood Control District of Maricopa County

II. DATA COLLECTION RESULTSA. Existing and Planned Drainage FacilitiesFew drainage facilities exist within the study area. The drainage patternis predominantly overland in a northeast to southwest directionaccumulating along the Roosevelt Irrigation District (RID) Canal andalong the Southern Pacific Railroad and eventually reaching the Salt andGila Rivers on the south and the Agua Fria River on the west.Papago Diversion ChannelThe ADOT Papago Diversion Channel runs to the west along the northside of Interstate 10 and defines the north limit of the study area. Thischannel captures flow from the north and diverts it west to the Agua FriaRiver. Most of the storm drains from the north tie into the channel,although some pass to the south unintercepted.Other facilities receive and convey runoff by virtue of the fact that theyare within the path of the runoff even though they are not designed fordrainage. Existing features that receive runoff are the Buckeye FeederCanal, and several small Salt River Project (SRP) irrigation ditches alongagricultural properties. All of the canals in the project area are designedfor irrigation delivery rather than storm drainage. This results in floodingwhen runoff exceeds the capacity of the canals. Runoff that isintercepted by the railroad embankment makes its way westerly along theface of the embankment. Runoff flowing west along the embankmentponds behind section line roads that have raised profiles to pass over therailroad. The flow breaks out to the south when the ponding elevationexceeds the height of the embankment. None of the cross-roads haveculverts of a significant enough size to drain nuisance flows through theroadway embankment.Agua Fria LeveeThe Agua Fria Levee extends from north of Interstate 10 south toBuckeye Road near the Southern Pacific Railroad. The levee is designedto convey the 100 year storm flow in the river without overtopping thebanks. Consideration will be given to new outlets for any new drainageimprovements planned to discharge into the Agua Fria river.Holly Acres LeveeThe Holly Acres Levee is an existing bank protection project on the GilaRiver, extending from 113 th Avenue downstream to El Mirage Road.The levee was designed to accommodate a flow of 115,000 cubic feetper second (cfs) with three feet of freeboard, however at approximately100,000 cfs, the river flows over the north bank at 99 th Ave and aroundthe Holly Acres Levee. The levee is not in danger of being overtoppedsince it is outflanked before the river level rises high enough. Theoutflanking is not likely to cause damage to the levee, as it is armoredwith stones on both sides.Tres Rios projectThe Tres Rios project is an ongoing project in the Salt/Gila River withan effort to restore critical riparian and wetland habitats that have beenlost in the region as a result of water resources development in thePhoenix metropolitan area. The project extends from the 91 st Avewastewater treatment plant to just downstream of the confluence withthe Agua Fria River. The project is currently in a feasibility study phaseand will identify potential benefits for flood control, including bankprotection levees.All of the existing culverts in the study area are considered insignificantdue to their small size and incapacity to convey storm flows during thedesign event. Therefore the capacities of the existing culverts are notanalyzed.South Mountain Freeway (Loop 202)The possibility exists for a future Loop 202 Freeway extension to thesouth, approximately along the 59 th Ave alignment, which may blockwesterly drainage within the study area. It is anticipated that the designfor the freeway will include collector channels and basins to intercept therunoff, retain the flows, and drain south to the Salt River. The potentialmay exist to cooperate with ADOT in developing a new drainage outfallfor the area.B. Areas of FloodingAreas of flooding within the study area have been delineated as FEMAfloodplains along the Salt, Gila, and Agua Fria Rivers, along theupstream embankment of the RID Canal and along the SPRR. ExistingFEMA floodplains are shown on Figure II-1. Additionally localflooding problems have been reported and are known to exist along theBuckeye Feeder Canal, along 91 st Avenue between Interstate 10 and theSPRR, and along Van Buren Street in the vicinity of 95 th and 96 thAvenues.DIBBLE & ASSOCIATES 4 DURANGO ADMPDATA COLLECTION REPORT