Loading...
HomeMy WebLinkAboutItem 3A - Public Comment - OswithLandTrust 1 July 18, 2025 Palm Springs City Council City of Palm Springs 3200 E Tahquitz Canyon Way Palm Springs, CA 92262 Subject: Consideration of Environmentally Sensitive Alternative at South Palm Canyon Drive & Bogert Trail low crossing bridge Dear Mayor and Members of the City Council, On behalf of Oswit Land Trust (OLT), we appreciate the opportunity to submit this letter regarding the City’s proposed flood project at the low water crossing at South Palm Canyon Drive and Bogert Trail. Oswit hired a civil water resources engineer with 35-year experience to evaluate, conduct engineering modeling and determine if there was an alternative that would achieve the same public safety goals but reduce the habitat destruction for the endangered bighorn sheep and other wildlife. We were successful in this endeavor. We respectfully submit an environmentally sensitive alternative. We have attached the 40-page full engineering analysis with copies of all the modeling and studies that were performed using the same methods used by county flood controls, corps of engineers, the state and the federal governments. This environmentally sensitive alternative has been shown to achieve better flood control performance and preserve 2.5 acres of sensitive pristine desert habitat (including eliminating the need for streambed alteration), which is critical for the federally endangered Peninsular bighorn sheep—a species increasingly threatened by habitat loss, fragmentation, and human 2 disturbance. Photo evidence (attached) confirms regular sightings of sheep in the flat wash area of Oswit Canyon. Overview of City’s Proposal • Low-water crossing bridge system consisting of a 5-barrel box culvert. • New engineered 2.5-acre channel west of the culvert. • Rock-lining of channel for erosion control. • Based on a 2001 Tettemer hydrograph with a 2,955 cfs peak flow estimated using conservative methods. *The current city design does not fully eliminate flood risk at the intersection as there will continue to be water that will enter the roadway south of the bridge system and flow north toward the Bogert Trail intersection. Oswit Land Trust’s AlternaKve • Retains the City’s bridge / culvert design (majority of the current design). • Eliminates the engineered channel, preserving the natural wash and bighorn habitat. • Introduces a roughly 2.5-foot-high floodwall along the sidewalk at South Palm Canyon Drive to prevent overtopping (see attached rendering). o Two options were analyzed: a short floodwall to the City/Oswit property line and a long floodwall to match road grade. We support the short wall. • Incorporates erosion control measures (e.g., riprap) at culvert inlet/outlet (which is required in city design as well). • Hydrologic modeling using HEC-RAS 2D shows this alternative performs at least as well as and likely outperforms the City’s proposal. See the water levels in the chart below. 3 Key Findings • Under both a 100-year and a more intense design storm, OLT's alternatives reduce water depth at the Bogert Trail intersection at least as well as and likely better than the Channel system. • No additional erosion risk compared to current conditions. • Preserves natural wash and habitat for endangered wildlife. Responses to Staff Concerns 1. Performance and Reliability City staff was concerned that the velocity (speed of the water), would not be handled with the alternative design. However, velocities remain within safe thresholds on both the city design and the alternative design. The velocity profiles at most locations are not greater in the alternative design compared to the city design. Riprap can control any erosion at the culvert inlet where velocities may increase. Reminder: this is not a river; it's a design handling a 100-year flood, which is the storm that has a 1% (1 in 100) probability of happening in any year. 2. Land Ownership and Permitting The recommended short-wall design lies entirely on City/OLT property, ending at the City’s southern easement boundary—no tribal land is affected, simplifying approvals. In 4 addition, the flood wall would only be constructed adjacent to the sidewalk within a typical Right of Way easement. Any embankment to the west of the flood wall required to stabilize the floodwall would likely not extend significantly westward depending on how it was designed. 3. Timeline and Funding Risks Additional modeling and detailed design to have the addition of the wall ready for bid would take no more than one to two months. The bulk of the city's original design is remaining the same. The city can be working on this alternative while finishing its environmental review updates. In fact, including this alternative in the environmental review could benefit the environmental review process. 4. Uncertain Costs Many costs (culvert, road, inlet/outlet) remain unchanged. Replacing a 2.5-acre channel with a narrow wall and embankment along the sidewalk has the potential to be cost- neutral or cost-saving. Concerns over increased cost are premature and speculative without an estimate. City staff had stated the cost of just the rock in the proposed channel would be nearly 1.5 million dollars. This alternative eliminates the need for such rock and eliminates the need to grade, build a maintenance road, etc. It is quite likely that building a 2.5 ft wall along the sidewalk would cost less than building a channel lined with rip rap. 5. Maintenance Access The maintenance road the city staff is referring to would only be built if a channel was constructed. Without a channel there is no need to drive into the canyon and no need for a road. 6. Land Area and Habitat Impact The floodwall’s width is approximately 1 foot. The width of the western embankment along the floodwall depends on how it is designed and keyed into the existing topography. An earthen embankment might be 5 feet in width to provide a 2:1 slope from the top of the flood wall to the elevation of the sidewalk. It would extend westward as necessary to meet the existing land elevation, which may be another few feet depending on the topography. Another embankment option is the application of a 5 rock-filled gabion system, which would be narrower than an earthen embankment, possibly on the order of another 2 to 3 feet from the sidewalk, resulting in an impacted area no more than 4 feet wide from the sidewalk. The entire floodwall embankment system would be located within areas adjacent to the roadway that are already degraded by road runoff. Unlike the City’s plan, this alternative avoids destroying pristine habitat used by bighorn sheep and other desert species. 7. Environmental Clearance Preliminary analysis suggests environmental impacts will be less than the original design, supporting a streamlined clearance process. In addition, we encourage the city to gather the opinions of US Fish and Wildlife Services, California Fish and Wildlife, Bighorn Institute and others regarding which design they support to have the least impact on endangered bighorn sheep and other wildlife. The city staff report mentions that this is the fifth design that has been submitted by Oswit Land Trust. Just to clarify, this is the only alternative that we have fully modeled and evaluated. This was an incredibly expensive endeavor for a non-profit to take on but we were committed to finding a solution that addresses both public safety and protection of critical habitat. Almost 5 years ago we submitted ideas to the city, but those ideas were never given the amount of evaluation/modeling that this alternative has been given. Other than this current design (which was originally developed to support the construction of hundreds of houses in the canyon [Proposed Eagle Canyon Development]), we are unaware of any other alternative flood designs the city has considered. With the change of use of the canyon, we would expect the city would look at alternatives. Conclusion Oswit Land Trust's environmentally sensitive alternative provides the same or more effective flood control, protects sensitive habitat and is potentially cost-neutral or even a less expensive solution to the City’s current/original flood design. It not only meets engineering 6 and public safety goals but also avoids irreparable harm to the habitat of the endangered Peninsular bighorn sheep—a species often observed in this exact floodplain. (See attached photo.) Palm Springs has a unique opportunity to implement a solution that reflects both sound engineering and environmental stewardship. We urge the Council to support this alternative and allow it to proceed toward implementation. Engineering and modeling can be completed with the alternative ready to bid within 30 to 60 days. We are happy to supply the city with all studies and modeling that were completed by our engineer. In addition, the city can certainly work with our engineer to move things along even faster. Thank you for your kind attention to our concerns. With regard, Jane Garrison, Executive Director Attachments: Photo: Peninsular bighorn sheep on Oswit Canyon floodplain Photo of potential flood wall along sidewalk Engineering analysis Bio of Richard Haimann, P.E., BCWRE, QSD, QISPcc: USFWS 7 cc. Palm Springs Planning Services planning@palmspringsca.gov Mayor Ron deHarte, City of Palm Springs ron.deharte@palmspringsca.gov Naomi Soto, City of Palm Springs Naomi.Soto@palmspringsca.gov Grace Elena Garner, City of Palm Springs Grace.Garner@palmspringsca.gov Jeffrey Bernstein, City of Palm Springs Jeffrey.Bernstein@palmspringsca.gov ScoC SDles, City of Palm Springs ScoC.SDles@palmspringsca.gov David H. Ready, City of Palm Springs David.Ready@palmspringsca.gov Alyssa Chavez, City of Palm Springs alyssa.chavez@palmspringsca.gov Nora Ayala, City of Palm Springs Nora.Ayala@palmspringsca.gov Peter SaDn, Coachella Valley ConservaDon Commission psaDn@cvag.org 8 Kathleen Brundige, Coachella Valley ConservaDon Commission kbrundige@cvag.org Jeff Villepique, California Department of Fish and Wildlife jeff.villepique@wildlife.ca.gov Chris Fust, California Department of Fish and Wildlife chris.fust@wildlife.ca.gov Heather Brashear, California Department of Fish and Wildlife Heather.Brashear@wildlife.ca.gov Jacob Skaggs, California Department of Fish and Wildlife Jacob.Skaggs@wildlife.ca.gov Lory Salazar-Velasquez, U.S. Fish and Wildlife Service lory_salazar-velasquez@fws.gov Noelle A Ronan, U.S. Fish and Wildlife Service noelle_ronan@fws.gov Mary Beth Woulfe, U.S. Fish and Wildlife Service marybeth_woulfe@fws.gov