CFA - Drainage Design Projects






	Typical Bailey Canyon Channel Bailey Canyon Flooding near Toll Road, December 31, 2005	Bailey Canyon Basin Drainage Study CFA completed a comprehensive stormwater drainage study of the Bailey Canyon Basin in June of 2006. The 15-square mile watershed is located southeast of Reno and ultimately discharges into Steamboat Creek near Geiger Grade. The purpose of the study was to improve the 100-year stormflow estimates from the basin and to quantify the flow amount crossing Geiger Grade to the north. The flow estimates were used to design existing and future storm drain facilities within the Curti Ranch subdivisions. The study included a detailed site survey and the development of a HEC-HMS hydrologic model to estimate the 100-year stormflow of about 2,900 cfs. A new storm frequency distribution based on the latest NOAA Atlas precipitation data was developed to improve the rainfall pattern. The model was also validated by comparing the results with a similar calibrated gaged basin and with other hydrologic methodologies including the Green and Ampt loss method, regression, and frequency analysis. A HEC-RAS hydraulic model was developed to determine the approximate flow split near the intersection of Toll Road and Geiger Grade. From this analysis, it was estimated that approximately 350 cfs would cross Geiger Grade in the event of a 100-year/24-hour storm event.

	Channel Protection Project Clear Creek Watershed	Channel Protection Project in Clear Creek Watershed Severe erosion is occurring at several locations in the Clear Creek watershed along U.S. Highway 50 between Carson City and Lake Tahoe. Erosion has caused problems related to slope stability along the roadway and has increased the maintenance requirements, especially those associated with drainage structures. The physical characteristics of the upper Clear Creek watershed include steep slopes, thin soil sections, and highly weathered bedrock, which allow erosion to proceed almost unchecked. In numerous cases, the erosion has manifested itself in the form of deep gullies and rilled slopes. A combination of laboratory tests and field studies were conducted to assess the performance of several rolled erosion control products (RECPs). These RECPs were found to be effective in reducing erosion over granular bare soil by a magnitude of three. In general, RECPs constructed with components containing rigid netting appeared to perform slightly better than other more flexible linings. This project was done by Patrick Fritchel for his thesis for his Master of Science degree at the University of Nevada, Reno.

	Summit Sierra Channel	Summit Sierra LOMR The Summit Sierra is a 72-acre master-planned retail development currently under construction at the intersection of Mt. Rose Highway and South Virginia Street. The property is bisected by the southernmost branch of Whites Creek, which is mapped as a FEMA Zone A (100-year flood). CFA performed hydrologic and hydraulic calculations and modified a previously prepared design for a flood channel to reroute the 100-year storm flows along the perimeter of the development. This flood channel was completed in December 2005. CFA prepared and submitted an application for a Letter of Map Revision (LOMR), which was issued by FEMA in March 2006, thereby, removing the developed portions of the property from the 100-year flood zone.

		Curti Ranch Master Drainage Plan Award-Winning Project The Curti Ranch Master Drainage Plan was a major component in a 567-unit subdivision site developed in Washoe County. The drainage from the pre-developed site was characterized by uncontrolled sheet flow conditions. Due to the lack of storm facilities or drainage easements downstream, concentrated stormflow was spread out to match existing sheetflow conditions. The Curti Ranch Drainage Plan was a complex solution that mitigated drainage impacts to downstream properties. The drainage plan includes three significant elements. First, a detention pond was designed to capture sediment and to reduce the peak discharge, which facilitated matching of flow quantities downstream of the project. Second, linear flow spread structures were designed to spread the concentrated flows to sheetflow conditions similar to existing conditions. The flow spread structures were also designed so that they may be converted to channels once drainage facilities are constructed downstream. Third, the Chandler Ditch was relocated. Because of the complexity of the ditch’s components (culverts, siphon, lateral weir, and adverse slopes), HEC-RAS was utilized for hydraulic and backwater calculations. In 2004, CFA received the Outstanding Achievement in Civil Engineering Award from the local chapter of the American Society of Civil Engineers for the effort and ingenuity put forth on this project.

		Sierra Star Master Drainage Study CFA prepared a master drainage study for the Sierra Star Master Plan in Mammoth Lakes, California. The study, which covers an area of approximately one square mile, estimated the existing- and post-development runoff rates. The Corps of Engineers HEC-HMS hydrology model was utilized in the analysis along with other hydraulic models to determine flow splits and diversions. Potential drainage alternatives were investigated to mitigate runoff increases due to development including detention and diversion.

		Evans Creek Restoration Award-Winning Project Evans Creek was restored as part of Mountain View Corporate Center, a 39-acre business park located in Southwest Reno immediately west of I-580 and south of Del Monte Lane. The project team consisted of CFA, Inc. (prime civil engineering consultant), Myers Design Engineering, Inc. (restoration consultant), and CSCON (wetland mitigation consultant). The project involved the restoration of an already degraded and unstable channel to a more natural-appearing and natural-functioning state. A half-acre wetland was also created in the floodplain to offset the disturbance of an existing jurisdictional wetland. The wetland mitigation was authorized by the U.S. Army Corps of Engineers under a Nationwide 27 Permit (stream and wetland restoration). The pre-restoration condition of the stream was characterized by vertical instability including oversteepened and eroded banks, active headcutting, and knickpoints. These characteristics indicated an intermediate evolutionary stage of an incising channel system that is entrenched and no longer connected to its former active floodplain. Stream restoration on this site accomplishes the following goals: Improves water quality by minimizing bed and bank erosion. Restores riparian vegetation and minimizes the need for hard lining materials. Reduces maintenance requirements. Provides compatibility with both aquatic and terrestrial forms of wildlife. To accomplish these goals, the slower gradient reaches of the stream were constructed as a meandering bankfull channel within a wider floodplain. In the higher gradient reaches of the stream, vortex weir drop structures, riffles (rapids), and plunge pools were incorporated into the design to dissipate channel velocities and mimic a step-pool channel system. Hydric soil in the existing wetland was blended with gravel (for scour control) and placed on the active floodplain to increase the potential of wetland re-establishment. CFA, Myers Design Engineering, and CSCON were awarded the 2004 Washoe County Design Award of Distinction for the Evans Creek Restoration Project. << Back to top >>

		Truckee River Levee and Floodwall CFA prepared final civil and landscape plans for 7,300± linear feet of levee and floodwall on the south side of the Truckee River between U.S. 395 and the East Second Street/Glendale Avenue bridge. As part of the Truckee River Flood Mitigation Project, the design required extensive coordination with numerous agencies, stake holders, and consultants, including the U.S. Army Corps of Engineers, Washoe County Department of Public Works, Washoe County Department of Water Resources, Reno-Sparks Indian Colony, Nevada Division of State Lands, Nevada Department of Transportation, Schaaf & Wheeler (hydraulics), Kleinfelder (geotechnical), and CEI Engineering Associates, Inc. (on-site design). The project is scheduled to break ground in early 2008.

		Master Drainage Studies A master drainage study is prepared at the outset of development as a road map for design of drainage facilities within each phase of development. The master drainage study must identify key drainage issues affecting the project and provide economical, code-compliant solutions. Below is a sampling of the master drainage studies that CFA has prepared for projects in Reno, Sparks, and Washoe County: ArrowCreek (1,090 lots) Spanish Springs Village (600 lots) Eagle Canyon (493 lots) Bridle Path Subdivision (351 lots) Oasis Bluffs (864 units) Monte Vista Village (20-acre office and retail development) FireCreek Crossing (70-acre shopping center) Summit Sierra (72-acre shopping center) Mt. Rose Station (89-acre hotel/casino and retail development)

		923 Tahoe Boulevard—BMP Retrofit The existing commercial project at 923 Tahoe Boulevard was conditioned by the Tahoe Regional Planning Agency (TRPA) to install an on-site surface water collection and infiltration system. CFA was contacted in March 2004 to provide surveying, civil design, and permitting for this project. The design for this site included stormwater collection and conveyance by means of retrofit curb and gutter, subsurface piping, sand/oil separation, and subsurface infiltration. CFA provided an existing conditions base map, final civil/landscape improvement drawings, and TRPA required BMP retrofit applications, forms, and checklists as part of this permitting process.

		Southwest Lemmon Valley Flood Channels CFA was the prime consultant in the final design of approximately 7,000 lineal feet of flood control channels in Lemmon Valley. Additionally, CFA prepared a flood control master plan, which included approximately 2.8 miles of flood channel design within the study area. Schaaf and Wheeler provided expertise in the areas of hydrology, hydraulics, and FEMA approvals. A Conditional Letter of Map Revision (CLOMR) for the channels and flood zone modifications was submitted to FEMA in August 1998. CFA expedited the approval process, and the CLOMR was issued in November 1998. The final design of Phase 1 of the project consists of channel and culvert improvements for storm flows up to 2,200 cfs. A triple reinforced concrete box culvert was designed across Military Road as well as channels ranging from 30’ to 150’ wide. Several channel linings were specified to prevent erosion including concrete, riprap, and fabric with revegetation. The project was constructed in 2003. CFA also prepared and processed a Letter of Map Revision (LOMR) through FEMA. The LOMR was approved in March 2005.

		Orr Ditch Pump Station Weir CFA assisted Sierra Pacific Power Company (SPPCo) in obtaining a Corps of Engineers 404 Permit for the construction of the Orr Ditch Pump Station weir on the Truckee River. The purpose of the weir was to locally increase water levels in the Truckee River, thereby, diverting additional water to the Orr Ditch Pump Station in order to meet capacity requirements at the Chalk Bluff Water Treatment Facility. CFA was responsible for determining the river’s water surface profile before and after the weir at ordinary high water line and base flood (100-year storm) and for recommending specific mitigations (bank protection) due to increased water elevations on several residential properties abutting the river. CFA assisted SPPCo in presenting the proposed mitigations to the property owners for approval. The weir and mitigations were constructed in 1992. Following the regional flooding in 1997, SPPCo retained CFA to compare actual high water marks with those predicted by the hydraulic model to demonstrate that the flow in the river had exceeded the design 100-year event. << Back to top >>

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