Feasibility of Fish Passage at Alameda Creek Diversion Dam

6.0 Additional Considerations and Analysis6 ADDITIONAL CONSIDERATIONS AND ANALYSISThis section provides a discussion of additional factors, beyond the preliminary analysis in Section 4and the cost analysis in Section 5, that warrant consideration when evaluating design components at aconceptual level. These include estimates of the amount of habitat that the design components couldprovide access to, the potential for the design components to sustain a population of steelhead, andthe other environmental considerations related to fish passage. Information from this section issubsequently used in Section 7, where the biological benefit of passage is analyzed.6.1 HABITAT AVAILABILITYA key consideration in assessing the opportunity for creating passage at ACDD for future steelhead isunderstanding habitat conditions upstream of ACDD. Detailed data regarding habitat conditions forO. mykiss in the Upper Alameda Creek Basin are limited and completion of habitat surveys was not withinthe scope of work for this conceptual feasibility analysis. This section summarizes information fromavailable literature and knowledgeable experts.The SFPUC’s property extends only 1.5 miles upstream from ACDD. If passage was provided at ACDD,it is assumed that future steelhead would gain access to additional habitat above the extent of SFPUC’sproperty. The Upper Alameda Creek Basin extends roughly 12 miles above ACDD, although theuppermost extent of the basin lacks suitable steelhead habitat (Figure 6-1). Based on analysis of aerialphotography, the uppermost extent of Alameda Creek is highly ephemeral. An aerial survey conducted inOctober 2002, following a dry water year, found that of the approximately 9.4 miles surveyed betweenACDD and the upper extent of Alameda Creek, 2.7 miles were dry (Entrix, 2003). At that time it wasestimated that approximately 4 of the 6.7 miles of wetted channel between ACDD and the upper extent ofAlameda Creek had potential to support rearing juvenile steelhead.An on-the-ground survey conducted in August and September 2005, following an above normal wateryear, found that 90 percent of the reach between ACDD and Camp Ohlone was wetted (HagarEnvironmental Science, 2008). The extent of the channel that remains wetted through the dry season, andthe extent to which portions of the wetted channel provide suitable O. mykiss rearing habitat will varyannually, but during all years the extent of suitable rearing habitat will be limited to a portion of the wettedchannel.SFPUC included a portion of Alameda Creek above the confluence with Calaveras Creek, up to CampOhlone, in their riparian zone monitoring project. Preliminary, reconnaissance-level habitat typing data,including identification of riffles, flatwater, and pools, was conducted in 2005 (SFPUC, 2008b). Flatwaterhabitat accounted for almost 50 percent of the surveyed reach, with pool comprising 30 percent, and riffle20 percent. Roughly half of the surveyed reach is below the confluence with Calaveras Creek, andtherefore outside of the Upper Alameda Creek Basin and the primary study area for this memorandum.Single-pass spawning surveys were conducted at several locations in Alameda Creek in 2006 (SFPUC,2008c), and six additional passes were made at overlapping and nearby locations between February andApril 2007 (Brian Sak, pers. comm., 2009b). Roughly 3,000 feet upstream of ACDD, an approximately1,000-foot-long reach of Alameda Creek is dominated by exceptional spawning and rearing habitat, andone redd was observed during the single pass survey in 2006 (SFPUC, 2008c). In 2007, six redds and fivediggings were observed in a 1.9-mile-long reach that begins 0.6 mile upstream of ACDD and continuesupstream to near Camp Ohlone (Brian Sak, pers. comm., 2009b). The reach of Alameda Creekimmediately above Camp Ohlone contains areas of suitable spawning gravel and pools with cover in theform of large woody debris and root wads (SFPUC, 2008c).ACDD Passage June 2009 Page 6-1