San Rafael | San Diego | Fort Bragg | Denver (415) 454‐8868 info@wra‐ca.com www.wra‐ca.com Old Canyon Road Bridge Scour Repair Biological Surveys and Permitting, Fremont, California WRA is teaming with David J. Powers & Associates and Schaaf & Wheeler to complete the environmental review and permitting studies necessary to repair scour on a bridge across Alameda Creek in Fremont, California.
Alameda Creek is not currently an anadromous fish stream, but restoration will begin in 2014 to construct fish ladders and return anadromous steelhead to Alameda Creek. The Old Canyon Road Bridge currently presents a low-flow fish passage barrier due to the presence of poured concrete in the creek bed beneath the bridge. The bridge scour repair will remove the concrete and install rock protection around the bridge abutments. WRA prepared Caltrans biological resources documentation for the project and engaged with the National Marine Fisheries Service in a Technical Assistance for concurrence that the design would not be detrimental to fish passage once the downstream fish ladders had been completed. WRA worked with the project engineers to assess potential fish passage issues at the bridge and to develop plans for fish passage that meet the National Marine Fisheries Service and California Department of Fish and Wildlife standards for fish passage. Dan was the project lead fisheries biologist for WRA and was involved in the preparation of environmental documentation and resource agency permit applications.
Mare Island Ship Yard Dry Dock Fish Salvage, Vallejo, California Marine vessels and barges are brought to the dry docks at the former Mare Island Naval Shipyard to be serviced and repaired. In accordance with permit requirements of USFWS, National Marine Fisheries Service (NMFS), and CDFW, biologists are required to be present during final stages of dewatering to salvage (rescue) stranded fish from the dry dock. Dan serves as project manager and lead fisheries biologist. He is responsible for leading field crews, coordinating with resource agency personnel, ensuring permit compliance, and authoring technical reports following each salvage event. He has also led consultation meetings, prepared biological assessments for the NMFS and USFWS permits, and assisted with amending an existing CDFW permit to reduce mitigation requirements for the dry dock. He is authorized to handle and relocate longfin smelt, Delta smelt, steelhead, Chinook salmon and green sturgeon at this site. This project is ongoing.
Pastori Avenue Bridge Outfall, Marin County, California Dan served as the lead fisheries biologist for a bank stability and outfall project in San Anselmo Creek within the town of Fairfax. Project work included a multi-day fish rescue and relocation under the authorization of a NMFS Biological Opinion. Several juvenile steelhead were successfully relocated out of the work area prior to the initiation of construction. During project work, Dan identified the invasive New Zealand mudsnail in the creek, which had previously not been documented for this watershed. NMFS and CDFW were notified of the occurrence.
Caltrans Southern California Lagoon Study, San Diego County, California California Department of Transportation is analyzing impacts and potential sources of mitigation for sensitive species and habitat for the Interstate 5 widening in San Diego County. As part of an analysis for increases in tidal inundation, Dan participated in wetland assessments and led field crews in biological assessments and topographic surveys within six coastal lagoons in northern San Diego County. During the biological assessments, several coastal California gnatcatcher pairs were identified and suitable breeding habitat for the species was mapped. The second phase of this project, which involves computer based simulation and analysis of increased tidal inundation, is ongoing.
Salmonid Habitat Assessment and Relocation in California Dan has worked on several projects designed to assess potential habitat for salmonid species. Survey techniques include CDFG protocol level stream habitat assessment, red and carcass spawning surveys, substrate composition and permeability sampling, geomorphic surveys, water quality sampling and analysis, various forms of netting and trapping, and snorkel surveys for identification purposes. Survey work has been conducted in Napa, Sonoma, Shasta, Santa Clara, Monterey, San Luis Obispo, Santa Barbara, Ventura, and Kern Counties.
Daniel Chase
San Rafael | San Diego | Fort Bragg | Denver (415) 454‐8868 info@wra‐ca.com www.wra‐ca.com Permanente Quarry Aquatic Baseline, Santa Clara County, California Permanente Quarry is a 3600 acre property located in western Santa Clara County at the northern extent of the Santa Cruz Mountains. As part of the quarry’s planned expansion, Dan designed and implemented a study of the habitat and aquatic fauna of two headwater creeks on the property. The following field studies were completed as part of this work: fish were surveyed by seine and visually to determine species composition, distribution and relative abundance; nocturnal time-constraint visual encounter surveys were employed to document amphibian species composition, distribution and relative abundance; benthic macroinvertebrates (BMI) were sampled at eight representative locations in accordance with the California Stream Bioassessment Procedure (CSBP). The collected BMIs were sorted by taxa and the data analyzed according to accepted metrics; and a detailed physical habitat study was conducted to quantify the condition and value of the current aquatic habitat. A technical report was completed that will serve as a baseline of the available habitat and existing fauna within the two watersheds.
Grady Ranch Creek Restoration and Permitting, Marin County, California As part of a proposed Grady Ranch Development in Marin County, a large scale creek restoration and fish passage improvement was designed and permitted. WRA provided biological services which included fish passage assessment, habitat mapping, fisheries surveys, California red-legged frog protocol level surveys, design review, agency consultation, permitting, and the preparation of long term monitoring plans. Dan served as the lead fisheries biologist for the project, and was involved with biological surveys, fish passage assessments, habitat mapping, consultation, and prepared a biological assessment to support the projects permits. While the project never went to construction, the restoration design was the process of receiving approval from the resource agencies.
Fish Passage Assessment in California
Dan has worked with several teams on the identification and assessment of fish passage barriers for anadromous species, which involved onsite qualitative habitat analysis and quantitative data collection utilizing a Total Station Survey Instrument. His survey work and professional assessments have been used as supplemental components to technical reports and as part of a state wide database that is in process for Caltrans. Fish passage assessments have been performed in various watersheds of Marin, Contra Costa, Monterey, Santa Barbara, Ventura and Los Angeles Counties.
Santa Clara River Estuary Habitat Restoration and Enhancement Feasibility Study, Ventura County, California
A Fisheries Restoration Grant Program through CDFW funded a feasibility study and conceptual design development for the restoration of estuarine fish habitat along the Santa Clara River Estuary. Following the preparation of an existing conditions technical report, stake holder outreach and restoration designs were crafted to focus on the conversion of an existing developed campground back to higher quality estuarine habitat. The campground would then be relocated from its current footprint. Dan served as the project manager and lead biologist. His work included a habitat assessment, report preparation, design review, participation in outreach meetings, and team management. The final feasibility report for the preferred concept will be released in 2015.
Napa Dry Bypass Flood Control, Napa County, California
As part of a comprehensive flood control program for Napa County, a high flow bypass channel and creek restoration at the confluence of Napa Creek and Napa River was constructed in downtown Napa. Dan served as the project’s lead fisheries biologist, which involved fish rescue and relocation, otter trawl fish sampling, fish exclusion, pile driving monitoring, and daily construction checks. He also assisted Napa County Flood Control District with a permit amendment to the project’s CDFW Incidental Take Permit. The completion of the dry bypass project resulted in increased flood capacity and improved habitat conditions for special-status fish including steelhead and longfin smelt.
Daniel Chase
San Rafael | San Diego | Fort Bragg | Denver (415) 454‐8868 info@wra‐ca.com www.wra‐ca.com Marin County Public Works Fisheries Services, Marin County, California Marin County Department of Public Works (MCDPW) underwent maintenance sediment removal at multiple culverts in West Marin. WRA provided biological support services for the sediment removal, which included preconstruction California red-legged frog surveys, environmental training, fish rescue and relocation and biological monitoring. During fish relocation, tidewater goby was encountered in an area they had not previously been documented to occur. Following the project work, WRA prepared a supplemental biological assessment of tidewater goby addressing sediment removal activities for MCDPW. Dan served as the project manager, lead fisheries biologist, and authored the supplemental biological assessment.
Callippe Preserve, Pleasanton, California
The Callippe Preserve was established as mitigation for the construction of the Pleasanton Municipal (Callippe) Golf Course. As a component of the wildlife management plan and USFWS Biological Opinion, Dan has conducted hydrological monitoring, annual sampling for California Tiger Salamander, and required predator monitoring and removal within the Preserve Conservation Areas. In 2009, Dan discovered a new population of California red-legged frog within a Preserve Conservation Area pond. Predator removal via hand capture, hook and line, gigging, shooting, and dipnet capture continued throughout 2009 and 2010. Successful breeding of California red-legged frog was confirmed in 2010. In October 2010, Dan, with approval of the USFWS and the landowner, dewatered the pond using a gasoline-powered trash-pump to rid it of bass and bullfrogs. Monitoring is ongoing, however California red-legged frog breeding success is expected to improve in 2012. In the fall of 2013, non-native predatory fish were detected in the golf course irrigation ponds. Dan assisted with draining the ponds and eradicate the fish in compliance with the USFWS Biological Opinion and associated management plans. Dan assisted with the captured and retention of 22 CRLF during the dewatering. CRLF were released back into the irrigation ponds as soon as refilling resumed.
Frenchman’s Creek Water District, San Mateo County, California Frenchman’s Creek Water District (FCWD) is a small water service provider located north of Half Moon Bay along coastal San Mateo County. A CDFW 1602 permit allows for the temporary installation of a flashboard dam and water withdrawal from the system. Dan serves as the fisheries biologist for this project and the FCWD, which involves monitoring flow and habitat conditions during the diversion period, permit compliance, and annual reporting. This project is currently ongoing.
Potrero Creek Restoration Carmel, California
Dan helped design, manage and implement the restoration of Potrero Creek, in the Carmel Valley, California. A large landslide altered the existing channel and was undermining a road. Dan aided with the design to restore the previous channel alignment and use the altered channel as a high water channel which would provide rearing habitat for steelhead and California red-legged frog. He conducted environmental training for the workers, pre and post restoration geomorphic surveys, served as the onsite biological monitor and restoration manager during construction, and assisted with the permitting of the project.
Draper Inverness Dock Permitting, Marin County, California In accordance with permit requirements of USFWS and NMFS, Dan performed pre-construction eelgrass surveys at a dock replacement project in Tomales Bay. Dan also performed daily construction monitoring for all inwater work, conducted environmental sensitivity training to on-site construction staff, and monitored environmental permit compliance for the project. Construction involved removal of creosote piles and installation of eelgrass friendly deck grating that allows light to penetrate beneath it. Following the construction of the dock, Dan led annual monitoring work to document the project effect on the eelgrass bed. Monitoring was completed in 2012 when the eelgrass bed was confirmed to have recovered to pre-construction conditions.
Patricia Valcarcel earned a MS in Wildlife Sciences while conducting research on the spatial ecology of the threatened giant gartersnake. She has worked on a variety of field research projects ranging from animal movements to behavior and reproduction. She has presented her work at many conferences and published in peer-reviewed journals.
Patricia has extensive experience working with giant gartersnakes in the Sacramento Valley and assisted with mark-recapture surveys for San Francisco gartersnakes in San Mateo County. She has performed surveys and other activities related to California red-legged frog in Alameda, San Mateo, Los Angeles, Solano, and Sonoma Counties. Patricia also has extensive experience throughout California’s Central Valley including protocol-level surveys for Swainson’s hawk, burrowing owl, and assessments for San Joaquin kit fox and blunt-nosed leopard lizard. In addition, she has conducted observations and coordinated compliance for Pacific herring spawning in San Francisco Bay.
Patricia’s primary responsibilities are to conduct surveys, habitat assessments, and write associated biological assessment and technical reports for special-status wildlife species. She has experience with the San Joaquin County Multi-Species Habitat Conservation Plan as one of the oncall biologists for the San Joaquin Council of Governments. In addition, Patricia is involved in environmental permitting, permit compliance, and mitigation and monitoring efforts associated with these permits.
Representative Projects
East Bay Municipal Utility District Mokelumne Aqueduct Project, San Joaquin County, California 2012 – 2013
Recoating of the Mokelumne Aqueduct Phase 8 – Slough Crossing Project will be conducted at four project sites located in San Joaquin and Contra Costa counties. In accordance with permits, a USFWS-approved giant gartersnake biologist is needed to perform pre-construction surveys and compliance monitoring. Patricia holds a USFWS Recovery Permit for giant gartersnake and was approved to perform the pre-construction surveys.
She also monitored a Swainson’s hawk nest within the Project Area to confirm nesting status of the pair and EBMUD compliance with avoidance measures.
San Joaquin Council of Governments, San Joaquin County, California 2012 – Present
WRA is contracted for on-call services related to the San Joaquin County Multi-Species Habitat Conservation and Open Space Plan (SJMSCP).
Patricia has performed pre-construction surveys and recommended avoidance and minimization measures to ensure participants are in compliance with the SJMSCP. Wildlife species and habitats Patricia has encountered as part of this work include burrowing owl, California tiger salamander, and Swainson’s hawk. In addition, Patricia prepared and consulted with the California Department of Fish and Wildlife on a burrowing owl exclusion plan. Following approval by CDFW, Patricia implemented the exclusion and monitoring plan.
PATRICIA VALCARCEL, MS
Wildlife Biologist
[email protected]
o: 415.454.8868 x1220
Years of Experience: 9
Education
MS, Wildlife Sciences, Oregon State
University, 2011
BA, Environmental Sciences,
Northwestern University, 2003
Professional Affiliations/
Certifications
USFWS Recovery Permit for giant
gartersnake and San Francisco
gartersnake (TE-64146A)
California Department of Fish and
Wildlife Scientific Collecting Permit
The Wildlife Society
Specialized Training
• Biology and Management of the
Alameda Striped Racer, Alameda
County Conservation Partnership, May
2014
• San Joaquin Kit Fox Ecology,
Conservation, and Survey Techniques,
Central Coast Chapter of The Wildlife
Society, Summer 2013
• Swainson’s Hawks in California’s
Central Valley, Sacramento-Shasta
Chapter of The Wildlife Society, Spring
2012
• Workshop on the Biology and
Conservation of the California Tiger
Salamander, Alameda County
Conservation Partnership, June 2012
• Amphibian Inventory and Monitoring
Protocol, Northwest Partners in
Amphibian and Reptile Conservation,
Spring 2011
San Rafael | San Diego | Fort Bragg | Denver (415) 454-8868 [email protected] www.wra-ca.com @WrC
ENVIRONMENTAL CONSULTANTS
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PATRICIA VALCARCEL
Ridge Top Ranch Wildlife Conservation Bank, Solano County, California 2012 – 2015 WRA and Ridge Top Ranch, LLC (RTR) are in the process of developing over 280 acres of high quality California red-legged frog and callippe silverspot butterfly mitigation habitat located within Solano County, California. WRA, in consultation with the USFWs and under 10(a)(1)(A) Recovery Permit TE-212445-0, successfully translocated California red-legged frogs to created habitat within the RTR Wildlife Conservation Bank. WRA has been involved throughout the process, from selecting donor sites and planning habitat creation, to translocation of egg masses and monitoring the frogs to ensure that establishment at the receiving site was successful. Through the monitoring phase, Patricia assisted permit-holder Rob Schell in survey efforts, which included egg mass surveys at the donor site, visual counts at the receiving ponds, as well as the capture and handling of juvenile red-legged frogs to measure and install PIT tags. She also conducted a Callippe silverspot butterfly survey as part of annual monitoring efforts. Monitoring at this site is ongoing, and the Conservation Bank is in the final permitting stages.
Napa Valley Marina Permitting and Dredge Monitoring, Napa, California 2012 – Present The Napa Valley Marina is an active recreational marina along the Napa River near Bull Island. Maintenance dredging of the Marina is necessary for boat access to and from the Napa River. Patricia is involved with a variety of environmental consulting services for the maintenance dredging including preparation of applications for the Dredged Materials Management Office (DMMO) and the California Department of Fish and Wildlife Streambed Alteration Agreement. Maintenance dredging permits included monitoring for special-status species and habitat conditions such as temperature and salinity monitoring for longfin smelt. Patricia oversees monitoring and compliance surveys for the multi-year maintenance dredging project.
Port of Richmond Inner Harbor Maintenance Dredging, Richmond, California 2014 – 2015 Maintenance dredging of the Port of Richmond Inner Harbor Channel was necessary to maintain passageways for the active port. The Pacific herring is a protected fishery, and dredging operations within the Pacific herring spawning season were unavoidable. Patricia was a California Department of Fish and Wildlife approved observer for the Project, and she coordinated a team of observers for the maintenance dredging Project. One spawning event occurred within the Project Area during dredging activities and Patricia consulted with CDFW to establish buffers. All Project activities were completed in compliance with the Project’s Pacific Herring Work Window Waiver.
Bruno’s Island Bridge Repair Project, Southwestern Sacramento County, California 2014 Bruno’s Island is a small recreational boat harbor located off Andrus Island along the San Joaquin River in the western Delta. Bridge repair activities included sheathing piles within the channel and could potentially affect listed aquatic species. Patricia provided the hydroacoustic analysis and wrote the Section 7 Biological Assessment for Delta smelt, steelhead, and giant gartersnake. Through her work and advising on project design such as strike limits and use of bubble curtains outside of the work windows, a “Not Likely to Adversely Affect” was received from both NMFS and USFWS. This Project was completed in 2014. 12 Bridges, Santa Clara County, California 2012 – 2013
WRA was engaged by the County to prepare Natural Environment Study (Minimal Impact) reports, permitting documents, and Revegetation and Monitoring Plans for twelve bridges with critical abutment scour located throughout Santa Clara County, California. Patricia aided in the preparation of the Section 7 Biological Assessments for six of the bridges which incorporated California red-legged frog, California tiger salamander, Least Bell’s vireo, and salmonid species. Based on those plans, she has conducted the pre-construction surveys and biological monitoring required by the U.S. Fish and Wildlife Service Biological Opinion in 2012 and 2013 work seasons.
San Rafael | San Diego | Fort Bragg | Denver (415) 454-8868 [email protected] www.wra-ca.com
PATRICIA VALCARCEL
Burrowing Owl Surveys and Passive Exclusion, Legacy on 101, San Jose, California 2014 The Legacy on 101 project is a 16.35 acre property in Santa Clara, California that is to be developed into two 6- story industrial park/office/R&D buildings. The area is known to support burrowing owl, and a series of take avoidance surveys was conducted from 2008 to 2014. Patricia observed one burrowing owl occupying the property in 2014. Patricia developed the exclusion and monitoring plan submitted to CDFW. During the nonnesting season, she passively excluded the owl and excavated all potential burrows at the site. Patricia conducted monitoring at the site every other week until construction activities were initiated and performed a pre-construction survey immediately prior to grading, per the exclusion plan.
Napa Dry Bypass, Napa, California 2014
The Napa Dry Bypass is designed to divert 100 year flows around the oxbow reach to avoid flooding the Soscol Gateway area in downtown Napa. Patricia is a CDFW-approved biologist for this Project, and Patricia has been involved with this project by monitoring compliance and construction activities during excavations of the new river channel, as well as assisting with fish rescues within the coffer dams. Project permits include Biological Opinions from National Marine Fisheries Service and California Department of Fish and Wildlife Incidental Take Permits for steelhead (Central California Coast DPS), Delta smelt, and longfin smelt.
Marin County Department of Public Works Flood Control Line Replacement, San Rafael, California 2013 The Marin County Department of Public Works manages flood control projects throughout the county, including the city of San Rafael. The project consists of replacing an aging flood diversion pipe in a low-lying residential area adjacent to the south fork of Gallinas Creek. The project area is located in a salt marsh slough and has known populations of California clapper rail and salt-marsh harvest mouse. Patricia was a USFWS-approved biological monitor for the project and has monitored construction to ensure compliance with the project’s regulatory permits. Several California clapper rails were observed at short range and within the project area, and Patricia stopped work activities until the birds had safely left of the own volition.
Fitzgerald Marine Reserve Coastal Trail, San Mateo County, California 2012 – 2013 The Fitzgerald Marine Reserve project includes the design of a portion of the California Coastal Trail in San Mateo County, California. Major components of the project, in addition to the multi-use trail, included a free span pedestrian bridge and improved beach access and overlook. WRA provided environmental services in support of the proposed trail and public access improvements, and existing sensitive habitats were avoided to the extent possible in the public access design. WRA prepared the conceptual designs for the trail and improved access to the overlook and beach, performed wetland delineations, completed biological surveys, and prepared permit applications. As part of this process, Patricia was approved by the U.S. Fish and Wildlife Service under the Biological Opinion for the project to perform the pre-construction surveys and monitoring for San Francisco gartersnake and California red-legged frog. In addition, she provided advice on the design and materials for the wildlife exclusion fence, and oversaw its installation.
San Rafael | San Diego | Fort Bragg | Denver (415) 454-8868 [email protected] www.wra-ca.com San Rafael | San Diego | Fort Bragg | Denver (415) 454-8868 [email protected] www.wra-ca.com Nick holds a B.S. degree in Wildlife, Fish and Conservation Biology from the University of California, Davis. His coursework included ichthyology, mammalogy, ornithology, waterfowl and wetland management, population dynamics and invasive plant ecology.
Prior to joining WRA, Nick worked as a biological monitor on a transmission line project where he gained experience working with California tiger salamander, western spadefoot toad and nesting birds. In addition, he worked for two years as a Fisheries Technician in both the private and public sector. His work primarily revolved around population monitoring, invasive species removal, water quality and habitat assessments. He has worked extensively with Lahontan cutthroat trout and native species of the Sierra Nevada Mountains. Nick has also worked with the UC Davis Museum of Wildlife and Fish Biology and performed a cursory study on small mammal distribution throughout the state of North Dakota. He conducted live-trapping and collected specimens for the museum. The data collected was presented to the museum and the Smithsonian Institute in support of follow-up studies.
With WRA, Nick conducts fish salvages, habitat assessments, biological monitoring, focused wildlife surveys, and writes biological assessment reports. He has trained with Rob Schell, a U.S. Fish and Wildlife Service Recovery Permit holder for California red-legged frog (CRLF); Jason Yakich, Recovery Permit holder for California clapper rail (CCR); and Kate Allan, Recovery Permit holder for salt marsh harvest mouse (SMHM).
Representative Projects
Amy’s Kitchen, Rohnert Park, California, 2014 – Present During construction of facilities for Amy’s Kitchen in Rhonert Park, Nick was approved by CDFW as a biological monitor for California tiger salamander (CTS). During the course of the project, Nick monitored for environmental compliance at the site to assure that there was no take of covered species during construction. To date, no take of CTS has occurred.
Port of Richmond Inner Harbor Maintenance Dredging, Richmond, California 2014 – 2015
Maintenance dredging for the Port of Richmond Inner Harbor Channel was conducted in the winter of 2014 to maintain passageways for ships entering the port. Pacific herring is a protected fishery, and dredging operations within the harbor overlapped with the Pacific herring spawning season.
Nick was an approved California Department of Fish and Wildlife observer for the Project. During operations, one spawning event occurred within the Project Area. Nick observed the spawning event and informed crews on the required buffers to maintain compliance. All Project activities were completed in compliance with the Project’s Pacific Herring Work Window Waiver.
Nicholas Brinton, BS
Fisheries Biologist
[email protected]
o: 415.454.8868 x1780
c: 909.275.2358
Years of Experience: 3
Education
BS Wildlife, Fish and Conservation
Biology, UC Davis, 2012
Professional Affiliations/
Certifications
American Fisheries Society
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ENVIRONMENTAL CONSULTANTS
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NICHOLAS BRINTON
San Rafael | San Diego | Fort Bragg | Denver (415) 454-8868 [email protected] www.wra-ca.com Mare Island Ship Yard Dry Dock Fish Salvage, Vallejo, California 2014, - Present Mothballed vessels from the National Defense Reserve Fleet in Suisun Bay and private ships needing repair are brought to the dry docks at the former Mare Island Naval Shipyard. In accordance with permit requirements of USFWS, National Marine Fisheries Service (NMFS), and CDFW, biologists are required to be present during final stages of dewatering to salvage (rescue) stranded fish from the dry dock. Captured fish are placed in aerated holding coolers, identified to species, counted and measured before being returned to the Mare Island Channel of the Napa River. Nick is a lead fisheries biologist for this operation. He is responsible for leading a team of biologists who conduct salvage operations. He also coordinates with resource agency personnel, ensuring permit compliance, and writes technical reports following each salvage event. He is authorized to handle and relocate longfin smelt, Delta smelt, steelhead, Chinook salmon and green sturgeon at this site. This project is ongoing.
Healdsburg Veterans Memorial Dam Spillway Repair, Healdsburg, California, 2014 The Healdsburg Veterans Memorial Dam is a flashboard dam located within the city of Healdsburg on the Russian River. The dam is installed seasonally to create a temporary recreational lake. For this project, Nick was approved as the lead fisheries biologist, and biological monitor. He conducted pre-construction surveys for breeding birds as well as pacific pond turtle (PPT), and positively identified PPT in the project area. As the lead fisheries biologist he lead a team of biologists who performed multiple fish salvages within the project area following de-watering events. His team successfully identified, and safely re-located steelhead that were salvaged during the dewatering. Nick also conducted biological monitoring for PPT and special-status fish throughout the duration of the project to ensure that project activities were in compliance with agency permits. He conducted pre-construction checks, environmental trainings, and water temperature monitoring. The project was completed in compliance with relevant permits with no take of any special-status species.
Frenchman’s Creek Water District, San Mateo County, 2013 - Present Frenchman’s Creek Water District (FCWD) is a small water service provider located north of Half Moon Bay along coastal San Mateo County. A CDFW 1602 permit allows for the temporary installation of a flashboard dam and water withdrawal from the system. Nick serves as a fisheries biologist for this project, which involves monitoring flow and habitat conditions for steelhead during the diversion period, permit compliance, and annual reporting.
This project is currently ongoing.
Napa Dry Bypass, Napa, California, 2014 - Present
The Napa Dry Bypass is designed to divert 100 year flows around the oxbow reach of the Napa River to avoid flooding the Soscol Gateway area in downtown Napa. Nick has been approved as a lead fisheries biologist on this project and has conducted multiple fish salvage operations for longfin smelt, and steelhead. Nick also assisted in the otter trawl surveys and fish exclusion work which were required during impact hammer pile driving operations. He has also been involved with this project by monitoring compliance and construction activities including impact hammer pile driving. In addition, he assisted in the design and implementation of the environmental awareness training program to comply with both the streambed alteration agreement and incidental take permits. This project is ongoing.
Pristine Sun Solar Projects Pre-construction Surveys, California, 2014-Present WRA was contracted to implement environmental compliance measures for several Pristine Sun projects.
Projects involved creating 0.5-1 MW solar generation facilities in Glenn, and Shasta Counties. As part of these measures, Nick performed pre-construction surveys for Swainson’s hawk, white-tailed kite, long-eared owl, burrowing owl, and breeding birds at two sites.
Bridge Preventative Maintenance Program · Town of Fairfax Final Initial Study/Mitigated Negative Declaration | April 2026 Appendix C
APPENDIX C. CULTURAL RESOURCES REPORTS
Under separate cover and available for review at the Town of Fairfax. (.
Bridge Preventative Maintenance Program · Town of Fairfax Final Initial Study/Mitigated Negative Declaration | April 2026 Appendix D
APPENDIX D. HYDROLOGY STUDIES
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Alaska 129 Kristin Drive, Fairbanks, AK 99712 mobile/office 510-219-1064 California 2100 Fourth Street, No. 154, San Rafael, CA 94901 www.geomorphdesign.com Looking Downstream to Fairfax Creek from the Upstream Face of Marin Road Bridge (December 19, 2014) Location Hydraulic Study Report
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
Fairfax, California
January 2016
Prepared by:
Matt Smeltzer, P.E.
Geomorphologist/Hydrologist
CA Civil Engineer #71671
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LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Location Hydraulic Study Report
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
Fairfax, California
January 2016
Submitted to Town of Fairfax
This Location Hydraulic Study Report was prepared by a California Registered Professional Engineer using best available published hydrology and hydraulic information for the subject site in lieu of original hydraulic model analysis of the channel and bridge opening based on current channel topographic survey data. Best available hydrology and hydraulic information is deemed adequate for this analysis because the physical changes to the bridge inlet and outlet caused by the proposed bridge maintenance measures are evaluated to be sufficiently minimal such that the water surface elevation and scour effects are negligible and otherwise mitigated by design configuration of the measures and other proposed mitigation measures incorporated by the project. Limitations of this analysis are reviewed herein.
__________________________________
Matt Smeltzer, P.E.
Registered Civil Engineer No. C71671
__________________________________
Date
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Table of Contents
Summary of Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Project Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Purpose and Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary Potential Hydraulic Difference between Project and No-Project . . . . . . . . . . . . . . . . . . 9 Geomorphic Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Site Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Available Hydraulic Model Calculations for Existing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Potential Hydraulic Effects of Project Alternative and Recommended Mitigation Measures . . . 15 Scour Analysis and Recommended Mitigation Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Limitations of this Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Summary of Findings
Multiple bridge maintenance measures are proposed under the CalTrans Bridge Preventative Maintenance Program (BPMP) near the inlet and outlet of Marin Road Bridge spanning Fairfax Creek in Fairfax, California. This Location Hydraulic Study Report evaluates the potential effects that these BPMP measures may have on flood water surface elevation and channel bed scour, and proposes appropriate mitigation measures, if necessary. This analysis is according to the BPMP Design Plans prepared by California Infrastructure Consultancy (Sheets 7-9) and best available hydrology and hydraulic model information. A complete project description is contained in this report at page 7.
Of the four Marin Road Bridge BPMP measures outlined in the project description, three measures may have an impact on flood hydraulics and/or channel bed scour:
• Repairing the upstream right wingwall in place. The foundationless and thereby tensioncracked existing vertical concrete upstream right bank inlet wingwall would be repaired and reinforced in place with special grout and provided suitable foundation and scour protection by installing riprap behind and beneath the hanging wall toe. Riprap would be installed to fill void space beneath and behind the cracked wingwall and for forming an approximately 8-ft-long, 2- ft-wide, 2-ft-deep riprap prism toe in front of the wall. The riprap prism would be set to extending from existing bed grade to minimum 2-ft below existing bed grade. The riprap filling the void space behind and directly beneath the hanging wall toe would be carefully placed and steeply finish face sloped to minimize encroachment creekward from the wingwall toe.
However, some creekward encroachment from the existing wall face would be required for achieving wall toe foundation stabilization objectives with riprap; • Repairing the toppling downstream left wingwall in place. The existing cracked, slumped, and rotated bank-sloped concrete downstream left wingwall would be repaired and reinforced in place by grouting, soil nailing, shotcrete facing, and drill-and-bond connecting the existing wingwall repair section to the existing headwall; and,
• Repairing the rock slope protection (RSP) around the repaired-in-place downstream left wingwall. The existing slumped and rotated downstream left wingwall to be repaired and reinforced in place (above) would be provided improved scour protection and downstream bank erosion protection by removing the light rocks comprising the existing perimeter scour protection and installing appropriately sized riprap to provide bed scour protection along the toe of the repaired wall and bank surface erosion protection along the downstream edge of the repaired wall. An approximately 12-ft-long, 2-ft-wide, 2-ft-deep riprap prism would be installed on the bed at and below existing bed grade along the creekward toe of the repaired wall. An approximately 8-ft-high, 3-ft-long, and 2-ft-deep rip-rap prism would be installed on the bank at and below existing bank grade immediately downstream from the repaired wall. Overall, removing the existing failed light rock reinforcement from the bed and bank and replacing with properly sized and configured rock would serve to increase the hydraulic flood flow capacity of geomorphDESIGN
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com the bridge opening by removal of existing rock material encroaching creekward of the appropriate bed/bank envelope, especially within the bridge outlet cross-section.
Through design coordination with the Project Team, the BPMP measures have been designed to avoid and minimize potential effects on water surface elevation, scour depth, and downstream bank stability.
This analysis concludes that these BPMP measures would have a minor to de minimus impact on water surface elevation, bed scour, and downstream bank stability. This analysis further concludes that implementing the proposed measures would not substantially increase the Base Flood Elevation or otherwise increase potential for backwater damages to residences, other buildings, crops, or natural beneficial floodplain values. The measures would not substantially increase the potential for overtopping of Marin Road Bridge surface as may disrupt traffic or impact school bus or mail routes, emergency vehicle access, or emergency supply or evacuation routes.
However, mitigation measures are recommended (at p. 15) for further ensuring the project will not raise flood water surface elevations and for accommodating expected long-term permanent bed elevation decline and temporary scour during large floods.
This Study concludes that implementing the proposed BPMP measures at Marin Road Bridge – with or without also implementing the recommended mitigation measures – would cause no floodplain encroachment and minimal or negligible impact to flood water surface elevations. Therefore, a Summary Floodplain Evaluation Report has been completed for the project.
Figure 1 – Location Map Marin Road Bridge Site.
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Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Project Location
The Marin Road Bridge (site) is about 0.6 miles north-northwest of the downtown center of Fairfax, California (Figure 1). At the site, the bridge spans Fairfax Creek at a location about 135 feet west of Sir Francis Drake Blvd -- near decimal degrees latitude 37.993 N, longitude 122.595 W.
Figure 2 – Excerpt from 2014 FEMA FIRM Panel 451 showing the regulatory floodway and Special Flood Hazard Areas (SFHAs) in the vicinity of Marin Road Bridge Site. 7 5) (07L
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LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Fairfax Creek originates on the southeastern flank of Loma Alta and flows through Fairfax as tributary to San Anselmo Creek in Fairfax. San Anselmo Creek becomes named Corte Madera Creek in Ross, California, and drains to Corte Madera Creek estuary and San Francisco Bay near Larkspur, California.
The Marin Road Bridge spans Fairfax Creek about 1,845 creek feet downstream from “Westbrae Dam” bordering Olema Road, and about 735 creek feet upstream from Olema Road Bridge. According to the March 17, 2014 updated FEMA Flood Insurance Rate Map (FIRM Panel 451), the 1% annual chance flood is contained within the channel area of Fairfax Creek in the reaches immediately upstream and downstream from Marin Road Bridge (Figure 2).
The site occurs within a floodway designated by the March 17, 2014 FIRM revision. The FIRM implies that overland flooding resulting from the 0.2% annual chance flood and potentially shallow flooding resulting from the 1% annual chance flood originating from overflow onto Olema Road more than about 2,000 creek feet upstream from the site passes into Fairfax Creek over the right bank vertical concrete retaining wall immediately upstream from the site.
Purpose and Need
Concrete wingwalls at the inlet and outlet of Marin Road Bridge are in failed/failing condition requiring stabilization by reinforcement in place and placement of rock riprap toe foundation protection. The measures are needed for preventing ultimate complete failure and concomitant potential creek bank destabilization and/or temporary partial blockage of the bridge opening during floods, potentially damaging downstream private property by bank erosion effects and/or temporarily increasing the water surface elevation affecting multiple properties upstream from the site.
Project Description
Marin Road Bridge is a single span concrete earth-filled closed arch structure, constructed over Fairfax Creek presumably circa 1930. The exact date of the construction of the bridge may be different. The bridge is on a residential street leading to Sir Francis Drake Boulevard, a major arterial through the town of Fairfax. The structure is approximately 41 feet long and a little over 26 feet wide. It supports two lanes of traffic nearly 10 feet above the creek bed. There are no as-built plans available from the original design of the bridge, though a new General Plan (GP) from field measurements has been developed for the bridge. There are no sidewalks on the bridge but a separate steel pedestrian/bicycle bridge exists for non-motorized travelers immediately upstream of this bridge. (The latter bridge is not in the program.)
Marin Road Bridge is not eligible for National Register of Historic Places (NRHP) listing. It has a Sufficiency Rating (SR) of 68.0, but is flagged as neither Structurally Deficient (SD) nor Functionally Obsolete (FO) in the latest (2014) Caltrans Bridge Inspection Report (BIR).
The BPMP repairs for Marin Road Bridge and the method of construction will consist of:
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com • Repairing the toppling downstream left wingwall in place. The leaning, rotating and separated concrete wingwall on the southeast side (downstream of the bridge) will be repaired in place.
The wingwall is approximately 10 feet long and eight feet high. It will be reconnected to the existing bridge with steel dowels and rebar tied to its reinforcement, exposed by removing a strip of the wingwall concrete next to the bridge. The wingwall will be surfaced with a fresh layer of lightly-reinforced air-blown concrete (shotcrete), and stabilized with at least a couple of soil nails pinning it to the soil. Soil nails are steel tension elements placed in holes drilled through the concrete wingwall and the soil behind it for a distance of approximately 15’-20’, inclined at an angle of 15 degrees. The ends of these tension elements are buried in a bulb of grout pumped into the end of the drilled hole, called bond zone, allowing the bond zone to mobilize the soil through friction. The other end of the tension elements will protrude out of the wingwall surface and buried in the wingwall concrete overlay, anchored with special hardware and tensioned slightly to take the slack out of the line, creating a fastening system that will disallow the future movements of the wingwall. • Repairing the rock slope protection (RSP) around the repaired-in-place downstream left wingwall. The light rocks making up the scattered riprap will be collected and a course of rock riprap will be sized suitable for the top anticipated creek flow velocity. The soil volume below the bottom of the wingwall will be excavated along the front for a width and depth of two feet each to create a trench to place the rock in as a buttress against future scour. On the free edge of the wingwall not connecting with the bridge headwall a similar type of excavation will take place to place rock and connect to the RSP buttressing at the foot of the wall, in essence, surrounding the two exposed edges of the wingwall with rock riprap. Excavation at the edge of the wingwall for the RSP will be done manually and with small power equipment. The surface of the rock riprap will be flush with concrete wingwall, the creek bed and the embankment in order not to protrude into the waterway and impact the flows or flow capacity. The trenches housing the RSP will be lined up with special geotextile fabric to prevent the migration of the finely grained soil particles and erosion of the soil around the rock. • Repairing the upstream right wingwall in place. This second wingwall is on northwest side (upstream of the bridge) and vertical. It comes into the bridge headwall at an angle and is undermined, cracked horizontally near the bottom for five-six feet and dropped five to six inches below the crack due to gravity. The repair work will consist of cleaning the damaged and cracked concrete, patching the crack with special grout to prevent the further deterioration of this bridge structural element and burying some rock below the creek bed surface and in front of the wingwall to arrest its further undermining. Again, the surface of the rock riprap will be flush with the creek bed in order not to protrude into the waterway and impact the flows or flow capacity. Geotextile lining will be placed around the rock riprap here as well. • Repairing structural concrete spalls in the soffit of the structure. This is a manual operation on a handful of such structurally damaged spots in the concrete. After cleaning the rust from the steel rebars and removing the unsound concrete within the spall, a special agent, such as epoxy geomorphDESIGN
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An Area of Potential Effects (APE) drawing and a preliminary Bridge General Plan for the repairs have been developed for this bridge work. The work will be at both the deck and below deck levels and is expected to take as many as ten working days from start to finish. The bridge will remain entirely open to motorized and non-motorized traffic. A flag person directing traffic at times may be necessary but traffic queuing is not expected.
Summary Potential Hydraulic Difference between Project Alternative and No-Project Alternative Under the Project Alternative, the failed/failing inlet and outlet wingwalls would be repaired and reinforced in place – in the same position and configuration – as would have no effect on existing conditions or No-Project conditions flood flow hydraulics. However, stabilizing the inlet wingwall with riprap scour protection would necessarily encroach creekward from the face of the hanging wall toe, thereby minimally reducing the hydraulic flood flow capacity immediately upstream from the bridge inlet cross-section. Furthermore, installation of riprap scour protection at and below the creek bed elevation at the base of the reinforced inlet wingwall would reduce the scour depth during floods and thereby somewhat further reduce flood flow capacity at the bridge inlet cross-section. At the same time, replacing the failed riprap scour protection along the toe of the repaired in place downstream left bank wingwall would provide a commensurate increase in flood flow capacity at the bridge outlet. And installing new riprap scour protection along the toe of the repaired left bank wall would not decrease flood flow capacity by limiting scour depth during floods because the existing failed riprap scour protection currently effectively limits scour depth.
Therefore, overall, the proposed BPMP measures, as currently designed, in combination, would cause none, negligible, or de minimus increase flood water surface elevations.
And by also implementing the mitigation measures recommended in this report (at p. 15), the BPMP work would overall provide a negligible or de minimus decrease in flood water surface elevation.
Geomorphic Setting
The site occurs within a variably and in places very narrowly channelized reach of Fairfax Creek bordering Sir Francis Drake Blvd where the drainage area is about 2.6 square miles. The channel bed is sloped about 1.1% upstream from the site and 0.9% downstream from the site. Under existing conditions, ongoing intact geomorphic processes appear to be reinforcing a combination of meandering gravel-bedded pool-riffle and gravel-and-cobble-bedded plane-bed channel types (e.g., Montgomery and Buffington 1993).
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com However, pool-riffle sequence and inset floodplain development by channel meandering processes is strongly limited by severe confinement caused by historical channelization, historical channel bed incision, and construction of multiple non-deformable bank stabilization structures on private properties bordering the creek. Significant reach-scale changes requiring massive mobilization of dominating forced riffle bedforms, which appear to only result from very large floods capable of mobilizing large foreign rock and broken concrete materials dominating the bed framework materials at riffles. Large parts of many high-elevation coarse gravel bars established by the 1955 flood remain primarily intact in the reach, especially where root-reinforced by alder trees (Alnus rhombifolia) that established on the bar surfaces shortly after the flood (Stetson Engineers Inc. et al. 2000, Fluvial Geomorphology Consulting 2006). Short reach-scale and site-scale channel changes may also result from bank failures and treethrow during more frequent smaller peak flows.
Decades of broken concrete rubble and facing- to light-class rip-rap discharging into the channel from failed bank erosion protection structures and demolished-in-place creek bank retaining walls and bridge pier foundations has created an unnaturally high supply of fixed or infrequently mobilized large cobble and small boulder sized bed material in Fairfax Creek. Forced riffles set by large floods contain a substantial percentage of the bed material larger than large cobble to small boulder size material.
Coarse materials prevent riffles from being substantially deformed by smaller than 10-25-year floods, effectively preventing reach-scale changes to the riffle and pool locations and spacing.
Fairfax Creek became deeply incised beginning at the end of the 1800s and throughout the early 1900s (Stetson Engineers Inc. 2000). By the time of FEMA’s 1976 cross-section surveys for hydraulic model development (FEMA 1977) the bed elevations had reached practical minimum reinforced by multiple bedrock outcrops on the bed and low banks (typically well consolidated fine brown to gray sandstone, and often deeply weathered poorly consolidated fine brown sandstone exposed as dense clay) and grade controls created by concrete-floor bridge culverts and discharged large broken concrete debris.
Minimum bed elevation (thalweg elevation) measurements made at FEMA cross-section locations immediately upstream and downstream from Marin Road Bridge in 1999 showed minimal or negligible bed elevation differences from FEMA’s 1976 survey (Stetson Engineers Inc. 2000). Comparing FEMA’s 1976 and ca. 2010 minimum bed elevation profiles shows the bed elevation is relatively stable near the site (Table 1).
The 1976 downstream measurement was made 50 feet downstream from the bridge section while the ca. 2010 measurement was made about 25 feet downstream from the section. Some of the elevation difference (rise) shown downstream from the bridge is the result of surveying across a higher position on the steep riffle downstream from the bridge. The ca. 2010 downstream bed elevation is only about
0.5 feet higher than the 1976 elevation measured at the same location immediately downstream from the culvert outlet. The position of the riffle is not believed to have changed appreciably from 1976 to 2010 because it is forced by the high, coarse, alder root-reinforced right bank gravel bar immediately downstream from the bridge opening (see cover photo). It is plausible that the riffle crest position and elevation have varied somewhat at the site in response to scour and redeposition of the riffle bedform surface materials during the 1982 and 2005 floods.
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Table 1.
Comparison of 1976 and 2014 Minimum Bed Elevation Survey Data Immediately Upstream and Downstream from Marin Road Bridge.
Survey
Year
Minimum Bed
Elevation
(feet NAVD88)
Upstream from
Marin Road
Minimum Bed
Elevation
(feet NAVD88)
Downstream from
Marin Road
Source
1976 134.6 131.6 FEMA (1977)
ca. 2010 134.0 133.5 FEMA (2014)
Repeat site inspections made at the site mid-November and mid-December 2014 determined that none of the dominant larger-sized bed materials presumably emplaced in the December 31, 2005 flood were mobilized by the December 3 and December 12, 2014 high flows. Much larger flows are required to substantially scour the riffle at the bridge section. It appears that substantially deep scour may only occur at the inlet and outlet of the bridge opening during very large floods (e.g., 1982, 2005).
The riffle crest elevation occurring within the bridge culvert approximately mid-way through the bridge section is made high by the massive high-elevation coarse-grained alder root-reinforced right bank gravel bar immediately downstream from the bridge opening. Removal of the alder tree and the portion of the gravel bar reinforced by the alder roots, along with select removal of sediment grains larger than approximately 90 mm diameter contained in the riffle surface materials within the bridge section appears would allow for a lower elevation riffle to establish within the bridge section, possibly also at a section farther downstream from the center of the bridge culvert. These interventions would increase flood flow capacity of the bridge by lowering the bed elevation within the bridge section, allowing for deeper scour during small more frequent floods, and eliminating the potential for large floated debris to catch on the alder tree near the culvert outlet.
Site Hydrology
FEMA (2014) used regional regression equations to estimate various return interval peak flood discharges at locations upstream and downstream from the Marin Road Bridge site, from which estimates can be drawn for the site via drainage area apportioning (Table 2).
According to the Marin County Capital Improvement Plan Study (Stetson Engineers Inc. et al. 2011) the December 31, 2005 flood was estimated to peak near about 1,645 cubic feet per second (cfs) on Fairfax Creek at the inlet to Sherman Avenue culvert. Although it is generally believed that the 2005 flood was geomorphDESIGN
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Table 2.
Estimated peak flood flows at Marin Road Bridge (Site) determined by drainage area apportioning from FEMA (2014) published estimates at upstream and downstream Fairfax Creek locations.
Location Distance
upstream
from
mouth (ft)
Drainage
Area
(sq mi)
FEMA
(2014)
10-Year
Peak (cfs)
FEMA
(2014)
50-Year
Peak (cfs)
FEMA
(2014)
100-Year
Peak (cfs)
FEMA
(2014)
500-Year
Peak (cfs)
Fairfax Creek at
Corporate Limits
9,400 1.80 450 770 960 1,600
Fairfax Creek at Marin
Road Bridge (Site)
4,155 2.64 738 1,198 1,416 1,949
Fairfax Creek just
upstream from Bothin
Creek mouth
3,000 2.81 798 1,287 1,511 2,022
Fairfax Creek at inlet
Sherman Avenue
Culvert
480 3.57 1,038 1,661 1,945 2,594
Previously, FEMA (1977) had estimated the 100-year peak flow was about 1,720 cfs at the Sherman Avenue culvert inlet. FEMA (2014) estimated the 100-year peak flow there is about 1,945 cfs. Both FEMA (1977) and FEMA (2014) use as technical basis the regression equations of U.S.G.S (1971), but FEMA (2014) made adjustments or different adjustments for urbanization effects according to the same manual.
From apportioning 2014 estimates, the 100-year peak flow at the site is about 1,416 cfs (Table 2). From apportioning 1977 estimates, the 100-year peak flow at the site is about 1,336 cubic feet per second (cfs).
Available Hydraulic Model Calculations for Existing Conditions The only hydraulic models covering Fairfax Creek at the Marin Road Bridge Site are those prepared by FEMA (1977) and FEMA (2014). The 2011 Capital Improvement Plan study model used as its upstream domain the Scenic Avenue Bridge vicinity about 1,100 feet downstream from the site. Both FEMA models used similar cross-section spacing and do not reflect appreciable differences in bed elevation at geomorphDESIGN
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com the Site. However, as discussed above, the 1977 and 2014 hydraulic models used different estimated 100-year peak flood discharging for model-calculating the Base Flood Elevation (BFE) at the Site. the reach including the site were 1,450 cfs (1977) and 1,511 cfs For the purposes of this analysis, it is presumed that the FEMA contractors applied design discharges for (2014) – the peak flow values estimated
Figure 3
about 2.81 square miles.
for a location immediately upstream from the Bothin Creek tributary mouth where the drainage area is – Excerpt from 2014 FEMA FIS Flood Profiles (p. 121 of 123) showing calculated 0.2-, 1-, 2- and 10% The
Marin Road Bridge (Elevations NAVD88 datum).
annual chance flood water surface elevation profiles upstream and downstream from the Existing Conditions 2014 hydraulic model calculates a 100-year water surface elevation (BFE) drops about 3 feet from immediately downstream from the Marin Road Bridge (Figure 2, Fig about 145 feet NAVD88 immediately upstream from the Marin Road Bridge to about 142 feet NAVD88 ure 3). The three-foot drop in the
backwater effect on the 100
BFE occurring through the length of the bridge culvert indicates that the bridge opening exerts a -year water surface elevation under existing conditions.
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5 LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com By comparison, the 1977 FEMA hydraulic model calculates an approximately 2-foot drop in the BFE through the length of the Marin Road Bridge culvert, from about 142.6 feet NAVD88 immediately upstream to about 140.8 feet NAVD88 immediately downstream. Comparing the 1977 and 2014 model results shows that the calculated BFE immediately upstream from the bridge culvert opening raised about 2-3 feet from about 142.6 feet NAVD88 in 1977 to about 145 feet NAVD88 in 2014. The 2-3-foot rise in BFE cannot be entirely explained by potential 60-cfs increase in design 100-year peak flow discharge. Nor can it be explained entirely by approximately 0.5-ft rise in the downstream bed elevation. Presumably then, also, the 2014 model may have used higher Manning’s “n” roughness coefficient and improved high water mark calibration information gathered by Army Corps of Engineers after the 1982 flood and County of Marin after the 2005 flood. FEMA (1977) reports using Manning’s “n” channel roughness values for Fairfax Creek ranging from 0.025 to 0.080. FEMA (2014) reports using Manning’s “n” channel roughness values for Fairfax Creek ranging from 0.016 to 0.085.
According to existing conditions field measurements, the crown of the arch culvert at the inlet rises about 8.5 feet above the minimum bed elevation midway through the culvert length. FEMA (2014) calculated the BFE about 8.0 feet above the bed elevation at the bridge section, and FEMA (1977) also calculated the BFE about 8.0 feet above the bed. Therefore, it appears that the 100-year flood peak water surface elevation is about 0.5 feet lower than the crown of the culvert at the inlet. However, this does not imply that the culvert does not exert a backwater effect on the 100-year flood water surface.
As discussed above, the culvert causes a 2-3-foot rise -- the “shoulders” of the arch culvert inlet headwall on both sides of the crown cause pressure flow through the culvert. However, the resulting backwater does not rise above the bridge deck or the top of the vertical concrete right bank retaining wall extending upstream from the bridge inlet along Manor Road. Under existing conditions, there appears to be 2.5-3.5 feet of “freeboard” available before these structures are overtopped so as to cause flooding of the roadway.
Fluvial Geomorphology Consulting (2006) measured high water marks approximately 7.0 feet above the bed in the vicinity of Marin Road Bridge site resulting form the December 31, 2005 flood. Per the above discussion, the estimated peak flood flow during the 2005 flood is between the 50- and 100-year peak flow estimated by FEMA (2014).
The overtopping flood has not been estimated by FEMA, nor has it been estimated by this analysis.
According to the downstream bridge face elevation shown on Sheet 7 of the CIC December 2014 Design Plan Set, the top of the railing is 5.4 feet above the arch culvert crown. FEMA (2014) calculated the 500- year flood water surface elevation (WSE) is about 4 feet higher than the 100-year WSE about 0.5 feet below the crown. Therefore, FEMA (2014) estimated the 500-year peak water surface elevation would rise to within about 2 feet from the top of railing which would presumably cause flooding through the railing and over the right bank vertical concrete retaining wall upstream from the inlet onto the roadway. According to the FIS profiles, FEMA (2014) calculated the 500-year peak water surface elevation is about 2.5 feet less than the top of the Marin Road Bridge railing (e.g., Figure 3). geomorphDESIGN
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Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Potential Hydraulic Effects of the Project Alternative and Recommended Mitigation Measures Compared to the No Project (Existing Conditions) Alternative, implementing the maintenance measures comprised by the Project Alternative would have a minimal, de minimus impact on the 100-year flood water surface elevation at and upstream from the site, a potential effect that would be entirely mitigated by also implementing the recommended mitigation measures identified below in this section of the report.
Specifically, the proposed project would place 2-ft-wide rock rip-rap toe foundations extending approximately 8 feet upstream from the inlet corner and 12 feet downstream from the outlet corner that, in plan, would be located entirely within the culvert opening edge lines extended or appropriate contraction/expansion lines extended upstream and downstream from the culvert. Although the top elevation of the rock will be at the existing ground elevation so as to not increase the actual or effective bed elevation, the toe foundations structures, as configured by the California Infrastructure Consultancy (December 2014 Plan Set, Sheets 7-9) may have a minimal or de minimus increasing effect on water surface elevation within and upstream from the bridge culvert by displacing mobile bed material below existing bed elevation and directly adjacent to the inlet and outlet corners with immobile rock material resisting scour during flood flows near and exceeding the 100-year flood flow. The potential amount of water surface elevation increase would not be detected by standard one-dimensional fixed-bed stepbackwater hydraulic modeling, and may be less than the detection level (i.e., threshold) for more advanced (i.e., moveable bed) hydraulic models, if employed for this analysis. Furthermore, actual construction of the rock fill behind and beneath the hanging toe of the existing wingwall should require creekward encroachment of the finished face of rock material in as much as the riprap cannot be installed to form a vertical finished face. This will cause a minor reduction in the flood flow capacity near the bridge inlet section.
However, by also implementing the recommended mitigation measures listed below, the potential hydraulic effects of the proposed project would be entirely mitigated both by directly increasing the cross-sectional area of the hydraulic opening at the culvert outlet, and allowing the creek bed to scour more deeply during larger floods.
Recommended Flood Flow Capacity Protection Measures
1. As part of the removal and replacement of failed rock scour protection along the perimeter of the existing downstream left wingwall, remove existing encroached large concrete debris from the culvert barrel at the outlet corner (downstream bridge face), thereby enlarging the hydraulic opening and reducing energy losses at the transition from the arch culvert section to the sloped embankment cross-section immediately downstream;
2. Remove existing large broken concrete rubble debris from the channel bed about 15 feet upstream from the culvert inlet;
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3. Remove the existing mature alder (Alnus Rhombifolia) rooted on the gravel bar immediately downstream from the culvert outlet (see cover photo) and the portion of the gravel bar that is reinforced by the alder tree roots; and,
4. Remove exposed bed materials larger than 90 mm diameter from the creek bed everywhere within the culvert footprint and within the low-flow channel bed extending not less than 12 feet downstream from the bridge outlet.
Overall, with or without implementing the recommended mitigation measures, implementing the proposed maintenance measures represents a very low level of risk. The proposed project condition will not cause longitudinal encroachment, significant encroachment, or support incompatible floodplain development in any way. Also implementing the mitigation measures is consistent with creek management for reduced flood damage risk, improved freeboard, and reduced debris blockage potential.
Scour Analysis and Recommended Scour Mitigation Measures As discussed above, historical channel bed incision has reduced the Fairfax Creek bed elevation to near minimum possible elevations constrained by bedrock exposures upstream and downstream from the site. More than 0.5 feet of additional long-term bed degradation is not expected to occur at the site.
By implementing the recommended flood flow capacity mitigation measures listed above, the bed elevation is expected to reduce about 0.5-1 feet within the culvert footprint and immediately downstream during floods subsequent following project implementation.
Therefore, as much as about 1.5 vertical feet of bed elevation lowering may be expected to occur at the site. Structures founded adjacent to the existing channel bed should be designed for future conditions having up to 1.5-ft lower year-round bed elevations.
In addition, the large gravel-sized material comprising the bed materials at the site after implementing the project and recommended mitigation measures should be expected to temporarily scour 2-4 vertical feet during large floods, with greatest scour occurring where the proposed rock rip-rap toe foundation structures are proposed.
Recommended Scour Protection Measures
1. Foundation structures constructed as part of the BPMP measures should be founded to sufficient depths below existing grade to perform as designed under future conditions including up to 1.5 feet of permanent long-term bed elevation lowering, as well as 2-4 feet of temporary bed elevation lowering by scour during floods.
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
Fairfax Creek at Marin Road Bridge (Br. No. 27C-0143)
January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Limitations of this Analysis
This analysis relies on existing best available information hydrology and hydraulic studies, primarily prepared by FEMA, for characterizing the existing conditions flood water surface elevation and scour potential at the Marin Road Bridge site. This analysis evaluates the potential effects on water surface elevation and scour potential of the proposed bridge maintenance measures according to professional judgment informed by understanding of basic hydraulic engineering principles regarding minimization of bridge inlet and outlet friction losses, rather than hydraulic model calculations for existing and proposed bridge geometry, in arriving at the conclusion that the proposed measures should have a de minimus effect on water surface elevations – including the base flood elevation – and scour potential, as should be entirely eliminated by incorporating recommended mitigation measures into the project. Conducting hydraulic modeling of the proposed project conditions is not recommended, in general, because the actual project effects on water surface elevation and scour potential are less than the increments likely to be detected either by standard one-dimensional fixed bed step-backwater analysis or twodimensional hydraulic analysis of detailed existing and design conditions site topography.
References Cited
Federal Emergency Management Agency (FEMA). 1977. Flood Insurance Study, Town of Fairfax, California.
Federal Emergency Management Agency (FEMA). 2014. Flood Insurance Study, Marin County and Incorporated Areas, Volume 1 of 2, Revised: March 17, 2014; Flood Insurance Study Number 06041CV001B.
Fluvial Geomorphology Consulting et al. 2006. Geomorphic Assessment of Fairfax Creek and San Anselmo Creek within the Town of Fairfax Limits, prepared for Town of Fairfax Public Works Department (July 31, 2006).
Montgomery, D. R. and J. M. Buffington. 1993. Channel classification, prediction of channel response, and assessment of channel condition: Olympia, Rep. TFW-SH10-93-002, 84 p., Wash. State Dept. of Natural Resources, Olympia.
Stetson Engineers Inc. et al. 2000. Geomorphic Assessment of the Corte Madera Creek Watershed.
Prepared for Friends of Corte Madera Creek and Marin County Department of Public Works.
Stetson Engineers Inc. et al. 2011. Capital Improvement Plan Study for Flood Reduction and Creek Management. Prepared for Marin County Flood Control and Water Conservation District.
U.S. Geological Survey. (1971). Open-File Report, Suggested Criteria for Hydrologic Design of StormDrainage Facilities in the San Francisco Bay Region. S. E. Rantz (author). geomorphDESIGN
LOCATION HYDRAULIC STUDY FORM *
Marin Road Bridge over Fairfax Creek in Fairfax, CA
Please see also “Location Hydraulic Study Report” for more information.
Dist. 04 Co. Marin Rte. 0 P.M. 0
EA Bridge No. 27C-0143
Floodplain Description:
The 1% annual chance flood is contained within the channel area of Fairfax Creek (Zone AE) in the reaches immediately upstream and downstream from Marin Road Bridge. The site occurs within a floodway designated by the March 17, 2014 FIRM revision. The FIRM implies that overland flooding resulting from the 0.2% annual chance flood and potentially shallow flooding resulting from the 1% annual chance flood originating from overflow onto Olema Road more than about 2,000 creek feet upstream from the site passes into Fairfax Creek over the right bank vertical concrete retaining wall immediately upstream (north) from the site.
1. Description of Proposal (include any physical barriers i.e. concrete barriers, soundwalls, etc. and design elements to minimize floodplain impacts) Repair and replacement in place in same configuration existing upstream right (west) wingwall at inlet and existing downstream left (east) wingwall and associated wall foundation riprap scour protection.
2. ADT: Current 110 Projected 129
3. Hydraulic Data: Base Flood Q100= 1,416 CFS
WSE100= 145 ft NAVD88 The flood of record, if greater than Q100:
Q= CFS WSE=
Overtopping flood Q= ___ ND/NA CFS WSE= 151 ft NAVD88
Are NFIP maps and studies available? YES X NO
4. Is the highway location alternative within a regulatory floodway?
YES NO X
5. Attach map with flood limits outlined showing all buildings or other improvements within the base floodplain. (See Location Hydraulic Study Report).
Potential Q100 backwater damages:
A. Residences? NO YES X
B. Other Bldgs? NO X YES
C. Crops? NO X YES
D. Natural and beneficial
FLOODPLAIN VALUES? NO X YES
6. Type of Traffic:
A. Emergency supply or evacuation route? NO X YES
B. Emergency vehicle access? NO YES X
C. Practicable detour available? NO YES X
D. School bus or mail route? NO YES X
7. Estimated duration of traffic interruption for 100-year event hours: 4
8. Estimated value of Q100 flood damages (if any) – moderate risk level.
A. Roadway $ NA
B Property $ NA
Total $ NA
9. Assessment of Level of Risk Low X
Moderate
High
For High Risk projects, during design phase, additional Design Study Risk Analysis May be necessary to determine design alternative.
Signature – Dist. Hydraulic Engineer Date
(Item numbers 3,4,5,7,9)
Is there any longitudinal encroachment, significant encroachment, or any support of incompatible
Floodplain development? NO X YES
If yes, provide evaluation and discussion of practicability of alternatives in accordance with 23 CFR 650.113
Information developed to comply with the Federal requirement for the Location Hydraulic Study shall be retained in the project files.
Signature – Dist. Project Engineer Date
(Item numbers 1,2,6,8)
• Same as Figure 804.7A Technical Information for Location Hydraulic Study located in Chapter 804 of the Highway Design Manual
SUMMARY FLOODPLAIN ENCROACHMENT REPORT
Marin Road Bridge over Fairfax Creek in Fairfax, CA (Br. No. 27C-0143) Please see also “Location Hydraulic Study Report” for more information. 1) Is the proposed action a longitudinal encroachment of the base floodplain? No.
2) Are the risks associated with the implementation of the proposed action significant? No.
3) Will the proposed action support probable incompatible floodplain development? No.
4) Are there any significant impacts on natural and beneficial floodplain values? No.
5) Routine construction procedures are required to minimize impacts on the floodplain.
Are there any special mitigation measures necessary to minimize impacts or restore and preserve natural and beneficial floodplain values?
No.
6) Does the proposed action constitute a significant floodplain encroachment as defined in 23 CFR 650.105q?
No.
7) Are Location Hydraulic Studies (same as Figure 804.7A Technical Information for Location Hydraulic Study located in chapter 804 of the Highway Design Manual) that document the above answers on file?
Yes. Both a Location Hydraulic Study Form (Attachment A) and a Location Hydraulic Study Report.
Alaska 129 Kristin Drive, Fairbanks, AK 99712 mobile/office 510-219-1064 California 2100 Fourth Street, No. 154, San Rafael, CA 94901 www.geomorphdesign.com San Anselmo Creek Looking Downstream to Upstream Face of Canyon Road Bridge (December 19, 2014) Location Hydraulic Study Report
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) Fairfax, California
January 2016
Prepared by:
Matt Smeltzer, P.E.
Geomorphologist/Hydrologist
CA Civil Engineer #71671
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LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Location Hydraulic Study Report
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) Fairfax, California
January 2016
Submitted to Town of Fairfax
This Location Hydraulic Study Report was prepared by a California Registered Professional Engineer with extensive hydrology and hydraulic modeling and analysis experience in the subject watershed. The study relies on best available published hydrology and hydraulic information for the subject site in lieu of original hydraulic model analysis of the channel and bridge opening based on current channel topographic survey data. Best available hydrology and hydraulic information is deemed adequate for this analysis because the physical changes to the bridge inlet and outlet caused by the proposed bridge maintenance measures are evaluated to be sufficiently minimal such that the water surface elevation and scour effects are negligible and otherwise mitigated by design configuration of the measures and other proposed mitigation measures incorporated by the project. Limitations of this analysis are reviewed herein.
__________________________________
Matt Smeltzer, P.E.
Registered Civil Engineer No. C71671
__________________________________
Date
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Table of Contents
Summary of Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Project Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Purpose and Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Project Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Summary Potential Hydraulic Difference between Project and No-Project . . . . . . . . . . . . . . . . . . 8 Geomorphic Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Site Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Available Hydraulic Model Calculations for Existing Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Potential Hydraulic Effects of Project Alternative and Recommended Mitigation Measures . . . 11 Scour Analysis and Recommended Mitigation Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Limitations of this Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Summary of Findings
Multiple bridge maintenance measures are proposed under the CalTrans Bridge Preventative Maintenance Program (BPMP) near the inlet and outlet of Canyon Road Bridge spanning San Anselmo Creek in Fairfax, California (Br. No. 27C-0146). This Location Hydraulic Study Report evaluates the potential effects that these BPMP measures may have on floodplain encroachment, flood water surface elevation, and channel bed scour, and proposes appropriate mitigation measures, if necessary. This analysis is according to the BPMP Design Plans prepared by California Infrastructure Consultancy (Sheets 4, 6, and 13) and best available hydrology and hydraulic model information. A complete project description is contained in this report at page 7.
Of the five BPMP measures outlined in the project description, two measures may have an impact on flood hydraulics and/or channel bed scour:
• Replacing the existing northwest wingwall. The existing left bank inlet failed/failing “sackrete” wingwall would be removed and replaced with a 15-foot-long vertical concrete retaining wall spanning completely between and smoothly joining with the existing vertical concrete retaining wall at its upstream end and the existing vertical concrete bridge abutment wall at is downstream end. The downstream most 9 ft segment of the wall would have a L-footing extending 3 feet toward the creek having a top elevation the same as the local minimum bed elevation. A 2’ wide by 2’ deep rip-rap prism would be installed creekward of the L-footing to prevent foundation scour; and,
• Repairing the existing northeast bridge wingwall. The existing left bank outlet vertical concrete wingwall would be removed and replaced with an extended wall to envelope an existing 18- inch-diameter RCP storm drain pipe downstream. The new wall would prevent ongoing backfill evacuation and bank erosion near the pipe outlet. The new vertical concrete wingwall will be doweled into the abutment wall and angled into the creek bank to provide approximately 1:1 hydraulic expansion ratio. The new wall would have an L-footing joining with the existing invert slab with the same top elevation. A 2’ wide by 2’ deep rip-rap prism would be buried into the creek bank flush with the exposed slope to protect the downstream edge of the footing. A new cable railing would be installed on top of the wall for fall protection.
Through design coordination with the Project Team, these BPMP measures have been designed to avoid and minimize potential effects on water surface elevation, scour depth, and downstream bank stability.
This analysis concludes that these BPMP measures would have a de minimus impact on water surface elevation and bed scour. This analysis further concludes that implementing the proposed measures would not substantially increase the Base Flood Elevation or otherwise increase potential for backwater damages to residences, other buildings, crops, or natural beneficial floodplain values. The measures would not substantially increase the potential for overtopping of Canyon Road Bridge surface as may disrupt traffic or impact school bus or mail routes, emergency vehicle access, or emergency supply or evacuation routes.
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com No additional mitigation measures are necessary to avoid and minimize potential project effects on upstream water surface elevations or scour depth.
This Study concludes that the proposed BPMP measures at Canyon Road Bridge would cause no floodplain encroachment and none or negligible impact to flood water surface elevations. Therefore, a Summary Floodplain Encroachment Report has been completed for the project that refers to this Location Hydraulic Study Report.
Project Location
The Canyon Road Bridge (site) is about 1.3 miles southwest of the downtown center of Fairfax, California (Figure 1). At the site, the bridge spans San Anselmo Creek at a location about 275 feet south of Cascade Drive -- near decimal degrees latitude 37.975 N, longitude 122.607 W.
San Anselmo Creek originates in Cascade Canyon Preserve and flows through Fairfax and San Anselmo before becoming named Corte Madera Creek in Ross, California, then drains to Corte Madera Creek estuary and San Francisco Bay near Larkspur, California.
Figure 1 – Location Map Canyon Road Bridge Site.
The Canyon Road Bridge spans San Anselmo Creek about 3,280 creek feet downstream from the Fairfax corporate limits near the downstream end of the Cascade Canyon Preserve, and about 2,270 creek feet upstream from the Meadow Way Bridge. According to the March 17, 2014 updated FEMA Flood -
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geomorphDESiGN
PROJECT
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1 LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Insurance Rate Map (FIRM Panel 451), the 0.2% and 1% annual chance floods are entirely contained within the San Anselmo Creek channel in the reaches immediately upstream and downstream from Canyon Road Bridge (Figure 2).
Purpose and Need
Left bank wingwalls at the inlet and outlet of Canyon Road Bridge are absent or in failed/failing condition requiring stabilization by removal of failed/failing wall components and installation of new vertical concrete retaining walls conforming smoothly to the existing vertical concrete abutment wall and the existing concrete slab invert bridge floor. The measures are needed for preventing ultimate complete failure of the left bank upstream from the bridge as would likely throw the existing cluster of large redwood trees at the top of bank into San Anselmo Creek to block the bridge opening, and preventing ongoing progressive bank erosion downstream from the outlet.
Figure 2 – Excerpt from 2014 FEMA FIRM Panel 451 showing that the 0.2% annual chance flood is contained in the San Anselmo Creek channel upstream and downstream from the site.
-
San Anselmo Creek
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LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Project Description
Canyon Road Bridge is a single-span precast voided slab concrete superstructure constructed in 1996 on two abutments remaining from a previous bridge at this location over San Anselmo Creek. This bridge is in a strictly residential area of the town of Fairfax leading to Cascade Drive, a major thoroughfare. The structure is approximately 30 feet long and a little over 15 feet wide. It supports a single lane of traffic and railings nearly 15 feet above the creek bed and has no sidewalks on it. Two sheets of as-built plans are available for the 1996 deck replacement project, but none are available for the original abutment supports in the creek. A new General Plan (GP) based on field measurements has been developed for the bridge. The bridge has a Sufficiency Rating (SR) of 72.8 and is flagged as FO by Caltrans in the latest BIR (2014) due to its narrow width. However, the narrow width is due to the Town’s decision to construct the new deck for a single lane bridge and the bridge should not be considered as FO for this reason. The bridge is not eligible for NRHP listing.
There is an elaborate concrete fish ladder that begins just upstream of the bridge and ends just downstream of it. It consists of a concrete invert on top of the creek bed covering the creek bed from abutment to abutment, and a depressed rectangular fish ladder structure in the middle having steel guides.
The Canyon Road Bridge BPMP repairs will consist of:
• Replacing the existing northwest wingwall. Currently, the wall is made up of bulging stacks of solidified concrete sacks. A cluster of old redwood trees behind the wingwall is causing the wingwall to bulge, making its collapse a real hazard. The stacked concrete sacks will be removed manually one by one and hauled away. The redwood tree cluster will be exposed thus and protected in place during the construction operations. The new vertical wingwall will be an approximately 15 feet long by seven to eight feet tall reinforced concrete wall, located a short distance in front of the redwood cluster and connected to the left edge of the existing bridge abutment. It will also be held back to the soil behind it with several soil nails going through the trunks and/or roots of the redwood trees. An arborist has determined no real harm would come to the trees from the drilling or operations. The new wingwall surface will come to the edge of the concrete fish ladder and will have a vertical expansion joint in it to allow the tree trunk to grow outwardly. Approximately a 9-foot segment of the wall will have a footing, protruding three feet away from the face of the wall, the top surface of which will be flush with the creek bed. Excavation at the edge of the creek for the wingwall and its footing will be done manually as well as with small power equipment lowered from the top. The surface of the new wingwall will be flush and in line with the existing abutment wall in order not to protrude into the waterway and impact flows or flow capacity. The space behind the wingwall, housing the redwood tree roots and base, will be backfilled with soil. A new cable railing will be installed on top of the wall for fall protection. A 2’ wide by 2’ deep course of rock riprap with geotextile lining will be placed in front of the foundation of the wall, flush with the creek bed, for protection of the footing from scour.
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com • Repair of the structural damage to the north abutment. To prevent the further deterioration of this bridge structural support, this work will consist of manually removing approximately two inches of the concrete on the surface of the north abutment wall, exposing the rebar grid behind the surface and cleaning the reinforcement. The concrete and dust from chipping and grinding the concrete surface will be captured and hauled away. Next, the reinforcement grid in the wall will be covered with a new two-inch layer of special grout and finished smoothly. • Repairing the existing northeast bridge wingwall. The short existing northeast wingwall on the right side of the above abutment will be removed and replaced with an extended wall to envelope an existing storm drain pipe daylighting adjacent to the bridge. The pipe discharge is eroding the creek back next to the bridge. The new wingwall will be doweled into the abutment wall and angled into the creek bank, avoiding any intrusion into the current hydraulic space.
The wingwall extension will be fortified with a couple of soil nails into the exiting bank. This wall will also have a short triangular footing in front, the top of which will be flush with the creek bed, joining with the existing invert slab. The downstream edge of the wall will be protected from erosion with a 2’ wide by 2’ deep course of rock riprap buried into the creek bank and flush with the exposed slope. A new cable railing will be installed on top of the wall for fall protection.
• Sealing the cracks in the bridge deck. This will be done with methacrylate, similar to Spruce Road Bridge. However, no polyester concrete will be used here. Since this is a one-lane bridge and it will be closed (after heavy traffic hours at night) for the sealing of its deck for a few hours, two measures to meet the needs of the residents will be implemented. First, a first-response crew and vehicle from Fairfax Fire Department will be positioned on the south end of the bridge for emergency situations. Secondly, the bridge will be opened for crossing by covering the sealing agent with plywood if an emergency crossing will be needed during the short duration of bridge closure. Prior notifications will be sent to the neighborhood. • New signage and railings. “Narrow Bridge” signs will be installed at each approach to the bridge a short distance away. Also, the existing wooden approach railings at all four corners of the bridge will be replaced with metal beam guard railings.
An Area of Potential Effects (APE) drawing and a preliminary Bridge General Plan for the repairs have been developed for this bridge work. The work will be at both the deck and below deck levels and is expected to take as many as fifteen working days from start to finish.
Summary Potential Hydraulic Difference between Project Alternative and No-Project Alternative Under the Project Alternative, the absent or failed/failing left bank vertical inlet and outlet wingwalls would be removed and/or replaced with new vertical concrete wingwalls with horizontal L-footings that would be carefully configured to avoid encroaching creekward of the existing retaining wall and creek geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com bed surfaces. Riprap prisms required for wall/foundation scour protection would be installed entirely below the existing creek bed elevation. Therefore, the Project Alternative would have none, negligible, or de minimus hydraulic impact on flood water surface elevations and reduce creek bed scour to an extent not affecting hydraulic flood capacity. Rather, the BPMP measures would increase the smoothness of the left bank wingwalls and the left bank bridge abutment wall, providing negligible or de minimus increase in flood flow capacity and reduction in flood water surface elevation.
Geomorphic Setting
The site occurs within a relatively natural unchannelized reach of San Anselmo Creek where the drainage area is about 3.5 square miles. The bed elevation drops about ten vertical feet at the Canyon Road Bridge Crossing. The floor of the bridge opening has been reinforced with a concrete slab and the headcut on the downstream side of the bridge has been protected with a sloping concrete apron and large rip-rap at the toe. A denil-type fish ladder runs up the center of the concrete apron covering the steep headcut slope.
The channel bed is sloped about 0.6-0.8% both upstream and downstream from the reinforced headcut at the bridge site. Upstream from the site the bed is gravel dominated and the channel type is expressly pool-riffle (e.g., Montgomery and Buffington 1993) with wide, low point bars and relatively wide, unconfined meandering processes primarily intact. Downstream from the site, San Anselmo Creek cuts down to the south into the very steep south canyon wall, its surface showing evidence of frequent hillslope failures in the exposed Franciscan mélange. As such, the channel is without organized bedforms, is essentially plane-bedded and dominated by lag deposits of large boulders from mélange derived colluvium.
San Anselmo Creek became deeply incised beginning at the end of the 1800s and throughout the early 1900s (Stetson Engineers Inc. 2000). By the time of FEMA’s 1976 cross-section surveys for hydraulic model development (FEMA 1977) the bed elevations had reached practical minimum reinforced by multiple bedrock outcrops on the bed and low banks. Bed elevations at the bridge sections were reinforced to prevent headcut advance at the road crossing. As such, there is no bed elevation fluctuation at the bridge. Bed elevation fluctuation upstream is minimized by the grade control at the bridge. Both the 1977 and 2014 FEMA Flood Insurance Studies show the bed elevation at the Canyon Road Bridge crossing to be 162 feet NAVD88 and 161 feet NAVD88 40 feet upstream from the bridge section (Table 1).
Site Hydrology
FEMA (2014) used regional regression equations to estimate various return interval peak flood discharges at locations upstream and downstream from the Canyon Road Bridge site, from which estimates can be drawn for the site via drainage area apportioning (Table 2). geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Previously, FEMA (1977) had estimated the same values shown in Table 2 as FEMA (2014). Both FEMA (1977) and FEMA (2014) use as technical basis the regression equations of U.S.G.S (1971). And although FEMA (2014) made adjustments to 1977 values on Fairfax Creek to account for urbanization effects according to the same manual, no such urbanization related adjustments were made for the San Anselmo Creek locations shown in Table 2.
From apportioning 2014 estimates, the 100-year peak flow at the site is about 1,550 cfs (Table 2).
Table 1.
Comparison of 1976 and 2014 Minimum Bed Elevation
Survey Data At and Upstream from Canyon Road Bridge.
Survey
Year
Minimum Bed
Elevation
(feet NAVD88)
at Bridge Section
Minimum Bed
Elevation
(feet NAVD88)
40 feet upstream
from Bridge Section
Source
1976 162 161 FEMA (1977)
ca. 2010 162 161 FEMA (2014)
Table 2.
Estimated peak flood flows at Canyon Road Bridge (Site) determined by drainage area apportioning from FEMA (2014) published estimates at upstream and downstream San Anselmo Creek locations.
Location Distance
upstream
from
mouth (ft)
Drainage
Area
(sq mi)
FEMA
(2014)
10-Year
Peak (cfs)
FEMA
(2014)
50-Year
Peak (cfs)
FEMA
(2014)
100-Year
Peak (cfs)
FEMA
(2014)
500-Year
Peak (cfs)
San Anselmo Creek at
Corporate Limits
44,280 3.10 725 1,300 1,480 2,100
San Anselmo Creek at
Canyon Road Bridge
(Site)
41,000 3.46 770 1,370 1,550 2,250
San Anselmo Creek at
Meadow Way Bridge
38,800 3.70 800 1,420 1,590 2,350
geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Available Hydraulic Model Calculations for Existing Conditions The only hydraulic models covering San Anselmo Creek at the Canyon Road Bridge Site are those prepared by FEMA (1977) and FEMA (2014). The County of Marin’s 2011 Capital Improvement Plan study model of San Anselmo Creek did not extend upstream from the Fairfax Creek tributary mouth.
Both FEMA models used similar cross-section spacing – and may have in fact used the same crosssection input data – and the same design discharges, and should be expected to calculate the same 100- year water surface elevations (WSEs) at the site.
The 2014 hydraulic model calculates a 100-year water surface elevation is 167.5 feet NAVD88 approaching the bridge opening and flows at critical depth (about 3.5 feet deep) through the bridge section -- supercritical flow occurs through the 10-foot dropping headcut on the downstream side of the bridge (Figure 3). FEMA’s 1977 Flood Insurance Study shows the same bed and water surface elevation profiles.
The 167.5-foot 100-year WSE is about 5.5 feet higher than the 162-foot-elevation concrete slab bridge floor. The Canyon Road Bridge opening is about 10.5 ft high. Therefore the 100-year flood water surface elevation is about 4.5 feet lower than the low chord of the bridge opening. Under existing conditions, the Canyon Road Bridge has sufficient flow capacity to pass the 100-year flood with considerable freeboard.
The overtopping flood has not been estimated by FEMA, nor has it been estimated by this analysis..
According to the FIS profiles, FEMA (2014) calculated the 500-year peak water surface elevation is about
3.5 feet less than the low chord of the Canyon Road Bridge deck (e.g., Figure 3).
Potential Hydraulic Effects of the Project Alternative and Recommended Mitigation Measures Compared to the No Project (Existing Conditions) Alternative, implementing the maintenance measures comprised by the Project Alternative would have a minimal, de minimus, beneficial impact on the 100- year flood water surface elevation at and upstream from the site.
Therefore, no mitigation measures are recommended.
Specifically, the proposed repair to the left bank wingwall at the bridge inlet will increase flood flow capacity of the bridge both by increasing the effective width of the bridge opening by about 1 foot, and by creating overall smoother transition between the upstream curved vertical concrete retaining wall and the vertical concrete abutment wall.
The proposed repair to the left bank immediately downstream from the bridge outlet will further increase the flood flow capacity of the bridge by providing a smoother hydraulic transition in the geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com expansion zone downstream from the bridge opening. As will replacing the surface of the existing left bank abutment wall.
Figure 3 – Excerpt from 2014 FEMA FIS Flood Profiles at p. 81P(c) showing calculated 0.2-, 1-, 2- and 10% annual chance flood water surface elevation profiles upstream and downstream from the Existing Conditions Canyon Road Bridge (Elevations NAVD88 datum)
Scour Analysis and Recommended Mitigation Measures
As discussed above, future channel bed incision is prevented at the site by the concrete floor placed within the bridge structure for preventing the advancement of a historically active 10-foot headcut immediately downstream from the bridge. Therefore, long-term permanent bed elevation decline is estimated to be zero.
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2 LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Temporary scour during large floods is maximum at the toe of the proposed new LOL type 6A retaining wall footing extension immediately upstream from the bridge inlet and the concrete slab. A permanent scour pool occurs at the junction of the slab and the existing failed/failing retaining wall. For the purposes of wall foundation design, it should be assumed that the bed elevation at the toe of the slab/wall corner reduces 3 feet lower than the existing bed elevation there during the short duration of large floods occurring at the site.
Limitations of this Analysis
This analysis relies on existing best available information hydrology and hydraulic studies, primarily prepared by FEMA, for characterizing the existing conditions flood water surface elevation and scour potential at the Canyon Road Bridge site. This analysis evaluates the potential effects on water surface elevation and scour potential of the proposed bridge maintenance measures according to professional judgment informed by understanding of basic hydraulic engineering principles regarding minimization of bridge inlet and outlet friction losses, rather than hydraulic model calculations for existing and proposed bridge geometry, in arriving at the conclusion that the proposed measures should have a de minimus effect on water surface elevations – including the base flood elevation – and scour potential.
Conducting hydraulic modeling of the proposed project conditions is not recommended, in general, because the actual project effects on water surface elevation and scour potential are less than the increments likely to be detected either by standard one-dimensional fixed bed step-backwater analysis or two-dimensional hydraulic analysis of detailed existing and design conditions site topography.
References Cited
Federal Emergency Management Agency (FEMA). 1977. Flood Insurance Study, Town of Fairfax, California.
Federal Emergency Management Agency (FEMA). 2014. Flood Insurance Study, Marin County and Incorporated Areas, Volume 1 of 2, Revised: March 17, 2014; Flood Insurance Study Number 06041CV001B.
Fluvial Geomorphology Consulting et al. 2006. Geomorphic Assessment of Fairfax Creek and San Anselmo Creek within the Town of Fairfax Limits, prepared for Town of Fairfax Public Works Department (July 31, 2006).
Montgomery, D. R. and J. M. Buffington. 1993. Channel classification, prediction of channel response, and assessment of channel condition: Olympia, Rep. TFW-SH10-93-002, 84 p., Wash. State Dept. of Natural Resources, Olympia.
Stetson Engineers Inc. et al. 2000. Geomorphic Assessment of the Corte Madera Creek Watershed.
Prepared for Friends of Corte Madera Creek and Marin County Department of Public Works. geomorphDESIGN
LOCATION HYDRAULIC STUDY REPORT
San Anselmo Creek at Canyon Road Bridge (Br. No. 27C-0146) in Fairfax, CA January 2016
Alaska · California mobile/office 510-219-1064 www.geomorphdesign.com Stetson Engineers Inc. et al. 2011. Capital Improvement Plan Study for Flood Reduction and Creek Management. Prepared for Marin County Flood Control and Water Conservation District.
U.S. Geological Survey. (1971). Open-File Report, Suggested Criteria for Hydrologic Design of StormDrainage Facilities in the San Francisco Bay Region. S. E. Rantz (author). geomorphDESIGN
LOCATION HYDRAULIC STUDY FORM *
Canyon Road Bridge over San Anselmo Creek in Fairfax, CA Please see also “Location Hydraulic Study Report” for more information.
Dist. 04 Co. Marin Rte. 0 P.M. 0
EA Bridge No. 27C-0146
Floodplain Description:
The 100-year flood is entirely contained in the channel at and near the Canyon Road Bridge site.
1. Description of Proposal (include any physical barriers i.e. concrete barriers, soundwalls, etc. and design elements to minimize floodplain impacts)
Repair and replacement of left bank (north) inlet and outlet vertical wingwalls and abutment wall surface with minor rip-rap foundation scour protection
2. ADT: Current 100 Projected 350
3. Hydraulic Data: Base Flood Q100 1,550 CFS
WSE100= 167.5 ft NAVD88 The flood of record, if greater than Q100:
Q= ND CFS WSE= 172.5 ft NAVD88 (December 31, 2005)
Overtopping flood Q= ___ND and NA CFS WSE=_177.5 ft NAVD88 Are NFIP maps and studies available? YES X NO
4. Is the highway location alternative within a regulatory floodway?
YES NO X
5. Attach map with flood limits outlined showing all buildings or other improvements within the base floodplain. (See Location Hydraulic Study Report).
Potential Q100 backwater damages:
A. Residences? NO X YES
B. Other Bldgs? NO X YES
C. Crops? NO X YES
D. Natural and beneficial Floodplain values? NO X YES
6. Type of Traffic:
A. Emergency supply or evacuation route? NO YES X
B. Emergency vehicle access? NO YES X
C. Practicable detour available? NO X YES ________
D. School bus or mail route? NO YES X
7. Estimated duration of traffic interruption for 100-year event hours: 4
8. Estimated value of Q100 flood damages (if any) – moderate risk level.
A. Roadway $ _NA__
B Property $ NA
Total $ NA
9. Assessment of Level of Risk Low X
Moderate
High
For High Risk projects, during design phase, additional Design Study Risk Analysis May be necessary to determine design alternative.
Signature – Dist. Hydraulic Engineer Date
(Item numbers 3,4,5,7,9)
Is there any longitudinal encroachment, significant encroachment, or any support of incompatible
Floodplain development? NO X YES
If yes, provide evaluation and discussion of practicability of alternatives in accordance with 23 CFR 650.113
Information developed to comply with the Federal requirement for the Location Hydraulic Study shall be retained in the project files.
Signature – Dist. Project Engineer Date
(Item numbers 1,2,6,8)
* Same as Figure 804.7A Technical Information for Location Hydraulic Study located in Chapter 804 of the Highway Design Manual
SUMMARY FLOODPLAIN ENCROACHMENT REPORT
Canyon Road Bridge over San Anselmo Creek in Fairfax, CA (Br. No. 27C-0146) Please see also “Location Hydraulic Study Report” for more information. 1) Is the proposed action a longitudinal encroachment of the base floodplain? No.
2) Are the risks associated with the implementation of the proposed action significant? No.
3) Will the proposed action support probable incompatible floodplain development? No.
4) Are there any significant impacts on natural and beneficial floodplain values? No.
5) Routine construction procedures are required to minimize impacts on the floodplain.
Are there any special mitigation measures necessary to minimize impacts or restore and preserve natural and beneficial floodplain values?
No.
6) Does the proposed action constitute a significant floodplain encroachment as defined in 23 CFR 650.105q?
No.
7) Are Location Hydraulic Studies (same as Figure 804.7A Technical Information for Location Hydraulic Study located in chapter 804 of the Highway Design Manual) that document the above answers on file?
Yes. Both a Location Hydraulic Study Form (Attachment A) and a Location Hydraulic Study Report.