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. . . . . . . . . . . .' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bosley Wash Drainage Master Plan L, . . Phase2: Alternative Drainage Facility Evaluation inadvertent storage can be reduced and advantage can be taken of the beneficial aspects. Limited drainageway improvements are included in this alternative. The lO-year alternative relies on the crossings at G Road and the Government Highline Canal to control flow rates downstream and subsequently control the flood hazard. Unfortunately, this flooding creates a flood hazard upstream of these crossing and inundates several properties. To mitigate this hazard, it is proposed that the property subject to flooding during the lO-year flood will be purchased. It must be recognized that flooding during larger events will continue to occur and that damage outside the newly acquired property is likely. ~?a~ne1 iI?pr?v.e~e~ts within.the W~tershed include improvements to the Stub Ditch drainage channel. This includes the enlargement of the channel to carry 50 cfs. These improvements consist of channel excavation and embankment construction. In combination, this prevents the overtopping of the channel and the subsequent flooding of properties above the Government Highline Canal. There are limited additional areas where channel improvements are needed, primarily in conjunction with culvert improvements at select locations along the channel parallel to F % Road. Generally, these consist of the addition of another 48-inch diameter culvert parallel to the existing crossing at two driveway locations along the road. An alternative is the complete replacement of the existing crossings with a new 60..inch crossing. The cost of these structural improvements, including land acquisition for the areas flooded during the lO-year flood, is estimated to be $795,000. This represents the capital cost of the facilities, the cost of land, and the cost of any incidental construction such as roadway repairs or utility relocation. Table 2 presents a tabular summary of the costs of the improvements associated with this alternative. Page 20 ;-""'\ ~ ......._y' @l.