SR 06:242 - Laserfiche WebLink

Marion Pavan Page 2 July 12, 2006 ROOll lb. Debris Flow HazardlFlooding - To address tPis issue, BGC performed additional aerial photographic analyses, and reviewed pertinent subsurface information in their files. Aerial photographic base maps were used to show potential debris flow source areas and run-out paths. Based on this additional work, BGC does not believe debris flows have the potential to affect the proposed development. With respect to flooding, BGC states, "We doubt the southern and northern drainages pose a flooding hazard to adjacent proposed building pads..." BGC indicates that the project civil engineer should address the flooding hazard for the central drainage. CSA Comment - The Project Geotechnical Consultant has adequately addressed the debris flow issue. We recommend that prior to final approval of the lot configuration and grading plan, the Project Civil Engineer address the potential for flooding of the proposed building pads from the adjacent drainages based on the latest grading plan. 2a. Retaining Walls - BGC recommends that cantilever walls be used instead of modular block walls if the proposed streets or driveways would be located closer to walls than two wall heights. CSA Comment - We agree with the use of cantilever walls instead of modular block walls near important facilities, however, this recommendation does not include buildings, only streets or driveways. Also, if the terrain behind the wall is level, this results in a 2H:1 V setback line from the base of the wall to the street/driveway. However, if the terrain is sloped, a 2H:1V line from the base of the wall would intersect the facility. We recommend approval if the wording is changed such that cantilever walls will be used if buildings, streets or driveways are within an imaginary 2H:1V line extending from the base of the wall, 2b. Lot Drainage and Downspouts - BGC recommends that concrete lined v.ditches be provided at the tops of graded slopes, and at the base of slopes adjacent to streets or driveways, BGC also indicates that future lot-specific geotechnical engineers should be responsible for providing recommendations for roof downspouts, drainage gradients away from homes and suitable locations for disposal of collected water. CSA Comment - As conditions of building permit approval, we recommend that consideration be given to requiring all downspouts to be collected in tightline pipes and that geotechnical recommendations are provided for drainage gradients away from homes, and that drainage discharge be in suitable locations on an individual lot basis. COTTON, SHIRES & ASSOCIATES, INC.