___________________________________________________________________ City of East Palo Alto Telephone Number: (650) 853-3116 EPA Government Center Confidential Fax Number: (650) 853-3111 2415 University Avenue
East Palo Alto, CA 94303-1164
OFFICE OF THE CITY MANAGER
Sent by email to [email protected]
Sent by email to [email protected]
April 4, 2023
California Department of Water Resources
c/o Mr. Ted Frink
P.O. Box 942836
Sacramento, CA 94236-0001
U.S. Army Corps of Engineers
San Francisco District, Regulatory Division
c/o Mr. Gregory G. Brown
450 Golden Gate Avenue, 4th Floor
San Francisco, CA 94102-3404
Subject: City of East Palo Alto’s Comments to the Notice of Preparation of Environmental Impact Report for the Searsville Watershed Restoration Project (proposed Project) dated February 14, 2023 (NOP) Dear Mr. Frink and Mr. Brown;
The City of East Palo Alto (City) appreciates the opportunity to provide comments on Stanford University’s Searsville Dam Project Notice of Preparation (NOP)/Notice of Intent (NOI) as part of their combined CEQA/NEPA process.
The City is concerned about the potential adverse impacts of the proposed Project on the City of East Palo Alto. The City’s primary concerns are: (1) the potential increase in flooding in the City, as well as (2) sediment transport in the San Francisquito Creek (Creek) and how Stanford will remove sediments that are transported to the City.
The City requests that the Project team address the following comments as part of the conceptual design and Environmental Impact Report:
1. The City currently experiences flooding. The NOP does not address how the proposed gate will be operated to reduce the likelihood of flooding downstream of the Searsville Dam. It appears that the most optimal time to conduct flushing is during significant rain events which may be at the same time that the City is experiencing flooding or about to flood. Flushing could cause or exacerbate flooding ___________________________________________________________________ in the City. The City requests that the flushing and/or gate operations not adversely impact the City.
2. Sediment modeling is inherently imprecise- we agree with Stanford that adaptive management is needed, with key triggers established for sediment volumes, water surface elevations, and water quality. Decision-making should be a joint effort with key stakeholders, including SFCJPA, Santa Clara Valley Water District, Caltrans and resource agencies.
3. We are concerned that our Reach 2 Project improvements could be negated by sediment deposition from Stanford’s Searsville Project with a single significant storm event. Therefore, upstream/offline detention features should be included in all alternatives. There are at least three reasons for this: 1) there is a large margin for error in sediment modeling (plus/minus 50%), 2) the modeled increases in water surface elevation due to sediment- up to 10 feet in the upper watershed- based on our meetings with Stanford’s modelers at Balance Hydrologics, and 3) the uncertainty of future climate change effects. These potential impacts should be considered individually, and cumulatively.
4. Mitigation measures must be proposed to ameliorate increased risks from the large amounts of sediment that will be deposited downstream, resulting in decreased channel capacity in varying locations over time. The downstream communities have been told that the Searsville Project will reduce flows downstream of the reservoir site, but not that it will reduce flood risk. If the reduced flow is only meant to mitigate for reduced channel capacity downstream, it will effectively transfer risk and cannot be supported by the downstream communities.
5. The Reach 2 Project widens the creek to accommodate an approximate 70-year storm event, with no margin for increases to the water surface elevation. The Stanford Searsville Project must compare impacts based on projected increases to water surface elevations as the baseline, and not on areas of modeled channel breakout.
6. The SFCJPA’s project plans do not include opening the fourth culvert underneath the West Bayshore/Highway 101 creek crossing. However, Stanford may need this for sediment movement. Based on preliminary modeling, it is known that this area accumulates a lot of sediment. Understanding the creek dynamics in this locationwith and without the fourth culvert- will be imperative for Stanford.
7. Stanford’s projected sediment removals do not resolve the increased risk of flooding due to loss of channel capacity. Moreover, sediment removal as presently proposed will be very difficult to implement. Stanford has suggested that annual sediment ___________________________________________________________________ removals will be required. Most of the sediment deposition is predicted to occur in an area of sensitive habitat near the tidally influenced area around U.S. Highway 101.
We suggest that Stanford consider removing a large portion of the accumulated sediment at the source. Regular sediment removals downstream are disruptive to the sensitive creek and tidal environment. Additionally, the traffic, noise, air quality and public safety risks from sediment removal trucking would be transferred from the upper watershed to the disadvantaged community of East Palo Alto.
8. As presented in the proposed preferred project, sediment movement downstream is envisioned to occur in two stages- initial flushing of accumulated sediment behind Searsville Dam through winter storm flows and thereafter be an annual ‘normal’ sediment load, as historically occurred without the Searsville dam. This initial flushing is estimated to require 7-to-8-years and would depend on rainfall of adequate intensity and duration. We are concerned that the resulting turbidity will be deleterious to fish and again suggest that the bulk of the accumulated sediment be removed at the reservoir.
9. Water quality should be monitored using continuous water quality monitors. With increased sediment, Total Dissolved Solids will increase, with potential for significant water quality degradation, particularly for aquatic species.
10.Given the increasing variability of rainfall in California’s coastal range due to climate change, the estimated 7-to-8-year window for storm flow flushing is entirely unpredictable and is not a schedule Stanford can guarantee. Stanford’s proposal to evaluate sediment flushing success at the end of that 7-to-8-year period and potentially remove sediment from the reservoir area if needed indicates that mechanical removal from the reservoir area is already a possible solution. Stanford should consider this approach to sediment management as a primary component of the project.
11.Sediment management will require close coordination and planning with multiple agencies – CalTrans, Valley Water, the cities of Menlo Park, Palo Alto and East Palo Alto, as examples. Unless this coordination is established in a clear, contractual, and fully funded manner, there is no reason to expect long-term sediment management will be sustained and successful. All relevant entities need to be identified, authorized, funded, and have (or provide) regulatory approval as part of the Searsville project. These actions are Stanford’s responsibility as part of the longterm management of the Searsville project’s impacts on the downstream reaches of the San Francisquito Creek.
12.Stanford has indicated their plans include in-channel habitat improvements and large sediment traps in the area immediately downstream from the Searsville Dam. We ___________________________________________________________________ encourage Stanford to model the transport of cobbles and pebbles downstream from these constructed features, to ensure that downstream channel areas are not starved of these types of sediment, which could result in lower-quality habitat and channel configuration changes downstream.
13.Because all models, and future climate variability are inherently uncertain, Stanford should conduct pre-project, during project and post-project surveys, reviews, and assessments of project and watershed conditions to better integrate adaptive management into their project implementation and long-term watershed management plans. The SFCJPA is willing to partner in these reviews and assessments.
14.We encourage re-evaluating Stanford’s General Use Permit’s conservation easement on Lake Lagunita and consider constructing or allowing others to construct a new offline detention facility at the Lake Lagunita site through the excavation of the existing lake and expansion of the existing dam or construction of a new one. This site, if properly modified, could provide more storage than other identified sites for potential offline detention. The existing easement is for California Tiger Salamander (CTS) and specifies: “The first location for habitat protection easements shall consist of preserved, created or restored upland habitat within 500 meters of breeding habitat, including either Lake Lagunita or created ponds in which successful CTS reproduction has been documented for at least three consecutive years with near- or above-normal rainfall, excluding any intervening years with substantially below normal rainfall. When all areas that meet this description have been placed in easement protection, easements may be granted on other open space lands that provide migration and dispersal corridors for CTS to the breeding habitat.” Breeding locations in the Reservoir and Delta Reaches may offset any loss from Lake Lagunita (Figure 1). Stanford Water Rights S004661 authorizes the Figure 1. Distribution of Tiger Salamander at Stanford (Source:
https://conservation.stanford.edu/science-management/threatenedspecies/california-tiger-salamander ___________________________________________________________________ diversion of water from San Francisquito Creek to Lagunita for recreational and habitat purposes.
15.Groundwater and surface water are directly hydraulically connected. Stanford uses both groundwater and surface water of San Francisquito Creek. San Mateo County concluded in their 2018 Groundwater Assessment that: An analysis of surface watergroundwater interactions in the Basin suggests that increased use of groundwater in the Basin could potentially affect baseflow in certain, hydraulically-coupled sections of San Francisquito and San Mateo Creeks, with potential implications for certain listed aquatic species such as steelhead trout. Although groundwater levels are currently being monitored by Valley Water and San Mateo County, additional evaluation of the joint data collected, as well as expanded surface water baseflow monitoring is indicated to ensure that adequate flows are retained for fish and groundwater sustainability purposes.
16.Considering climate change effects, modeling by Stanford University faculty (unpublished work by Dr. Suckale, et al) estimates that the frequency of 500-year storm events will occur three times more frequently than today with newest estimate of effects beginning by 2030 (per the 2023 IPCC report). With the additional sediment loads that will occur with Stanford’s proposed project at Searsville, creek channel capacity may be diminished. We encourage Stanford to take the long view of potential project effects for downstream member communities and all inhabitants in the watershed.
Thank you in advance for your consideration.
Sincerely,
Melvin E. Gaines
City Manager
City of East Palo Alto