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HomeMy WebLinkAbout2001-04-23 City Council (5)TO: FROM: City of Palo Alto City Manager’s Report HONORABLE CITY COUNCIL CITY MANAGER DEPARTMENT: PUBLIC WORKS 1 DATE:APRIL 23, 2001 CMR: 207:01 SUBJECT:STATUS UPDATE ON SAN FRANCISQUITO POWERS. AUTHORITY’S PROPOSED LEVEE PROJECT CREEK JOINT RESTORATION This report is provided as background information for the Council study session. No action, is required. Staff will return to Council in approximately one month with a recommendation on the levee restoration project. BACKGROUND In March 2000, the San Francisquito Creek Joint Powers Authority (JPA) Board of Directors approved a project to restore the creek levees downstream of Highway 101 to their as-built (year 1958) conditions, in order to provide an increased level of flood protection for adjacent residents and businesses. The JPA identified restoration of the levees as a short-term project that could¯ provide some tangible flood protection benefits while a larger long-term flood control project is being developed and implemented. The project was 6riginally conceived as a relatively simple maintenance project. Earth fill material would be added, to the existing levees to restore the original design elevation. As design work and the¯ preparation of environmental documents proceeded, several new issues have been identified making the ¯levee project more complex and more costly. The JPA Board of Directors is approaching a decision point on whether to proceed with construction of a larger project. DISCUSSION Since Council approval of project funding in June 2000, several issues have arisen that have necessitated changes to the scope and cost of the levee restoration project. The JPA Board has begun to discuss the nature and the repercussions of these changes, and staff recommends that Council reexamine the project in Order to assess whether or not the City should continue to support it. The primary changes include upstream mitigation measures, right-of-way requirements, and increased project costs. Upstream¯,Mitigation Measures , When the levee restoration project was first proposed, it was consideredto be a relatively simple maintenance project with negligible environmental impacts. It has now been CMR:207:01 Page 1 of 4 determined that restoration of the levees downstream of Highway 101 will cause water levels to increase by up to 0.7 feet upstream of Highway 101 during a 1 percent (100- year) storm event (see Attachment A). Staff believes that this unintended impact must be mitigated as part of the project .so that there is no net loss in flood protection for adjacent residents. The mitigation entails the raising and/or replacement of the existing floodwall on the Palo Alto side oftheereek and the construction of a wall or berm on the East Palo Alto side. Staff recommends that the flood wall modifications be designed to also mitigate the earlier impacts of the Woodland Creek Apartments project. Using this approach, the wall modifications would extend for a distance of approximately 1800 feet upstream of Highway 101, to a point where the combined impacts of the levee restoration and the Woodland Creek Apartments on the creek water level would diminish to 0.2 feet or less. A conceptual design of improvements upstream of Highway 101 on the East Palo Alto side of the creek is still a work in progress at this point. While staff recommends the continuation of design development activities for the levee project, a decision on whether Palo Alto should support final design and construction of the project should be postponed until additional design information is available. Right-of-Way Requirements Construction of new or modified flood walls upstream of Highway 101 ~will require new or expanded easements from adjacent property owners. The Santa Clara Valley Water District (District) has easements for the properties on the Palo Alto side of the creek, but they are too narrow to accommodate the required construction equipment. The District will negotiate with individual property .owners to acquire the additional easement areas, both for the construction activity and for 16ng-term maintenance. During construction, ’ it is likely that rear property fences and some existing vegetation may have to be removed in order to accommodate the work. Following completion of the. work, fences will be restored (though they may be set back from existing fence locations as necessary to accommodate maintenance activities) and new vegetation will be planted. In at least one instance, a Palo Alto property owner has improperly constructed improvements within the District’s existing easement. The owner will be asked to remove these encroachments at his own cost. The District will need the support of the City in seeking .expanded easements from property owners. Although the levee restoration project has grown in complexity and cost, staff continues to support its development. The project will provide increased flood protection for Palo Alto residents and businesses adjacent to the improvements. Downstream of Highway 10.1, Palo Alto levees will be raised an average of 1.4 feet and a maximum of 2.6 feet. Under current conditions, flooding occurs at the Palo Alto golf course at a flow rate of approximately 3,600 cubic feet per second (cfs). With the levee improvements completed, capacity increases to approximately 5,900 cfs downstream of Highway 101. (6,000 cfs is the projected flow rate in this reach of the creek during a 1 percent (100- year) storm event). The levee project would provide a significant increase in the level of flood protection for the golf course, airport, athletic center and commercial properties east of Highway 101. The project would restore the level of flood protection upstream of CMR:207:01 Page 2 of 4 Highway 101 to the 1.evel that existed prior to the construction of the Woodland Creek Apartments. The factor of safety would actually be .higher since much of the "temporary" sacked concrete wall in this reach would be replaced with a stronger reinforced concrete wall. Furthermore, because any floodwaters that leave the creek flow away from the creek towards areas at lower elevations, the flood p~’otection benefits of ¯ the project actually extend to a large area of northeastern Palo Alto. RESOURCE IMPACT The levee restoration project was originally estimated to cost $750,000 (including $100,000 for replacement of the pedestrian/bicycle~path). In May 2000, the JPA Board approved a cost-sharing plan for the levee project (subject to the approval of the ruling councils/boards of the JPA member agencies) wherein the Santa Clara Valley Water District and the San Mateo County Flood Control District would each contribute $250,000, the cities of East Palo Alto and Menlo Park would each contribute $50,000, and the City of Palo Alto would contribute $150,000 ($50,000 + $100,000 for replacement of the existing pedestrian/bicycle path atop. the levee) towards the cost of the project. In June 2000, Council approved project funding of $150,000 as part of the FY 2000-01 City budget. The estimated project cost has escalated substantially for several reasons, including the following: .. ¯More extensive environmental and engineering analyses have been required in order to identify (and avoid where possibl~) the potential environmental and flood impacts of the project and to devise mitigation measures where needed. ¯More costly levee construction techniques have been recommended for use in certain areas in order to avoid disruption of sensitive vegetation and habitat that currently exists along the sides of the levees. ¯Additional funding will be required to raise or replace flood walls upstream of Highway 101 as mitigation for the downstream levee restoration. ¯Additional funding will be required for acquisition of construction and maintenance easements for the upstream wall modifications. Costs could increase to as much as $2.5 million for the revised levee restoration project. A new plan to allocate project costs to individual JPA member agencies has not yet been developed. Staff recommends that Palo Alto’s existing commitment of $150,000 should not be increased, since the Santa Clara Valley Water District (District) has primary responsibility for flood control in Santa Clara County. The District has funding earmarked for San Francisquito Creek in its Measure B spending package, .which. was approved by County voters in November 2000 at least partly due to strong support from Palo Altans. POLICY IMPLICATIONS This recommendation does not represent any change to existing City process. CMR:207:01 Page 3 of 4 TIMELINE The JPA’s original schedule for construction of levee improvements was the fall of 2001. Due to the more complex nature of the project, the current schedule is to start construction in the spring of 2002. The JPA Board of Directors is ~heduled to vote on whether to proceed with the project at its May 2001 meeting. ENVIRONMENTAL REVIEW An "Initial Study" of environmental impact is currently being prepared for the project by the JPA. The results of this study will be published and a public h-earing will be conducted-at a JPA meeting. An environmental document for the project will be evaluated and adopted by the JPA Board of Directors. ATTACHMENTS AttachmentA: Hydraulic impacts Upstream of Highway 101 PREPARED BY: DEPARTMENT HEAD: JOE TERESI Senior Engineer , Director of Public Works CITY MANAGER APPROVAL:~ ~ST City Manager CMR:207:01 Page 4 of 4 ATTACHMENT A