Future of Los Padres Dam and the District’s Role


Meeting Date:

August 14, 2013





Dave Stoldt,




General Manager





Prepared By:

Larry Hampson




SUMMARY:   The National Marine Fisheries Service (NMFS) has directed California American Water (Cal-Am) to resolve fish passage issues and aquatic habitat degradation associated with Los Padres Dam (Exhibit 3-A).  In its 2015-17 General Rate Case application to the California Public Utilities Commission, Cal-Am is requesting $4.2 million to improve downstream fish passage (Exhibit 3-B) and $1 million to complete a detailed feasibility study to determine the ultimate fate of the dam (Exhibit 3-C).  The proposed schedule is to award contracts for both projects in mid-2015.  Concerning the long-term feasibility study, Mark Schubert, one of Cal-Am’s managers states in his direct testimony that “California American Water only wants to propose a project that best addresses the concerns of NOAA Fisheries.”  In its 2012 Draft Recovery Plan for steelhead, NMFS recommended removal of Los Padres Dam. The following discussion focuses on the feasibility study for a long-term plan for Los Padres Dam.




Cal-Am’s proposal for the study focuses on two alternatives – dam removal and restoration of reservoir capacity (partial or full) with additional habitat and fish passage improvements.  A preliminary cost estimate for sediment removal is provided, which ranges from $52 million to remove about 500 acre-feet of sediment to $100 million to remove all the accumulated sediment (i.e., about 1,250 acre-feet).  No costs associated with constructing upstream fish passage improvements, dam spillway modifications, or habitat enhancement activities downstream of the dam are provided. Cal-Am described in its testimony that a strategy would need to be developed for working with the District on how to best manage the Carmel River under either option, because of on-going environmental programs.


MPWMD currently holds permit 20808B from the State Water Resources Control Board, which granted storage rights in the vicinity of Los Padres Dam to 18,674 acre-feet per year (AFY), with a complete application of water required by 2020 (i.e., facilities operational and used for water supply).  In order to provide additional supply to the Monterey Peninsula, the MPWMD Water Supply Planning Committee has discussed options at the dam site that would expand storage capacity to greater than the original 1948 permit for 3,030 AFY.  The option to expand the capacity of the existing reservoir to greater than 3,030 AF is not currently included in the Cal-Am proposal.


There are several component studies that should be carried out in order to fully evaluate options described by Cal-Am and the Water Supply Planning Committee at the Los Padres Dam site.  These include:


·         Unimpaired flow analysis – this analysis would be used as the “baseline” for comparing changes in flow with various alternatives.  The most recent analysis of unimpaired flows was in 2002 using the District’s Carmel Valley Simulation Model (CVSIM).  This model is no longer available and is proposed to be replaced with a linked, surface-groundwater model for the Carmel River Basin (see related item in this Water Supply Planning packet).  Flow analyses are combined with aquatic habitat information to characterize the availability and quality of steelhead habitat under various flow conditions (see below).


·         Flow analyses associated with alternatives – several flow analyses involving different levels of diversions would be required in order to evaluate alternatives including: existing conditions and Cal-Am operations; future Cal-Am operations as proposed in the Monterey Peninsula Water Supply Project; partial reservoir dredging; full reservoir dredging; reservoir enlargement; and dam removal (with future Cal-Am operations).  It is likely that a change petition to SWRCB involving Permit 20808B would result in a permit that includes maintaining minimum instream flow requirements (see next bullet).


·         Updated instream flow study – NMFS completed recommendations for maintaining instream flows in 2002.  A modified version of those recommendations is currently being attached by SWRCB to all new permits issued for the Carmel River.  The 2002 NMFS study does not accurately reflect significant changes in river habitat conditions and Cal-Am operations over the past 25 years.   District staff is currently working with a consultant to develop an updated instream flow analysis using the Instream Incremental Flow Method (IFIM).  The study will likely take two years to complete.


The IFIM can be used to evaluate how changes in flow affect steelhead habitat and fish passage.  Alternatives being considered at Los Padres Dam would have significant effects on the flow regime in the dry season and could affect the flow regime in the “shoulder” seasons of late fall/early winter and late spring/early summer. 


·         Steelhead habitat evaluation of the Carmel River watershed – MPWMD’s 2004 evaluation of steelhead habitat in the watershed estimated that 50% of the spawning habitat in the watershed was upstream of Los Padres Dam.  Similarly, MPWMD estimated that 42% of the suitable rearing area in the watershed was above Los Padres Dam and that it was of exceptional quality due to its location within the Ventana Wilderness.  These estimates were based on habitat conditions between the 1980s and early 2000s and included the effects of unauthorized diversions.


The value of steelhead habitat both upstream and downstream of Los Padres Dam should be re-evaluated in the context of improvements to habitat in the main stem due to the removal of San Clemente Dam, stream restoration in the lower 15 miles of the river, proposed reductions in Cal-Am diversions, and any proposed gravel replenishment projects associated with sediment management at Los Padres Reservoir.  A combination study using IFIM and habitat suitability index assessments should be used to better understand the value of each reach of the river and each tributary and the potential for improvements downstream of Los Padres Dam.


·         Yield and cost/benefits analysis – increasing storage capacity at Los Padres Reservoir can be achieved through dredging, increasing the spillway elevation, or a combination.  Each alternative should be evaluated for costs and benefits to water supply.


·         Impacts analysis – Each alternative would have varying environmental benefits and impacts that may make them infeasible to permit.  An initial screening of alternatives should be carried out to rank alternatives and determine if there are fatal flaws.  For example, reservoir area at the existing spillway elevation is about 55 acres and increases slightly with elevation.  It is thought that with a 14-foot increase in the existing spillway elevation (about 800 AF in volume), the reservoir backwater would extend to the Ventana Wilderness.  A project that raises elevations above the level that reaches the Ventana Wilderness boundary would likely trigger the land swap approved by Congress in the late 1980s for the New Los Padres Project.  However, the status of the land swap would need to be investigated.  Because the dam is under the authority of the Division of Safety of Dams, any modifications to the spillway would require a permit from DSOD.  Modifications that trigger a Corps 404 permit process and change hydrology of the river would require formal consultation and a biological opinion from NMFS concerning potential impacts to steelhead.


·         Sediment management – Los Padres Reservoir is a more difficult and expensive site to address sediment issues than at the San Clemente Reservoir, where a unique situation allowed sediment to remain in place.  A fundamental issue with Los Padres Dam that needs to be addressed with any proposed project is both the short term and long term management of sediment.  The long term average sediment inflow is about 20 AFY or the equivalent of about 2,200 tandem truckloads of sediment annually.  Sediment starvation downstream of the dam continues to degrade the river through the armoring effect (winnowing of spawning gravel) and downcutting into the riverbed.  Failure to address this degradation will compromise efforts to reduce diversions and may lead to further destabilization of streambanks in the lower 15 miles of the river.


CONCLUSIONS:  In its 2015-17 General Rate Case, California American Water has proposed carrying out a feasibility study beginning in 2015 for a limited number of alternatives at Los Padres Dam.  These include dam removal and partial or full recovery of the original storage capacity.   The focus of the study is to satisfy National Marine Fisheries Service concerns about ongoing impacts to downstream habitat and passage of steelhead from operation of the dam.  The proposed outline for the study appears to consider many, but not all, of the issues, opportunities, and studies associated with a long term plan for the dam.


It appears that Cal-Am believes the District’s role in this study would be focused solely on environmental considerations, rather than on any water supply options.  The Water Supply Planning Committee may wish to consider making a recommendation to the Board of Directors about the District’s role in determining the future of Los Padres Dam and a response to the Cal-Am General Rate Case proposal. 



3-A      April 23, 2013 letter, Butler to Svindland

3-B      Cal-Am Project II 5-400049, Los Padres Dam Fish Passage

3-C      Schubert Testimony and Cal-Am Project 115-400100 Los Padres Dam Long Term Plan