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J»rtMA CLAIM VALLEY WAT® QfMMll 
LIBRARY 

W« ALMADSN EXPRBB8WS3J 

SAN JOSE, CALIFORNIA 95U8 


A 15-year implementation plan 


Clean, Safe Creeks 
& Natural Flood 
Protection 


Behind your 



Impaired Water Bodies 
Improvement Program 

Executive Summary Report'. 

Guadalupe Watershed 
Mercury Study 


January 20, 2005 





Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


TABLE OF CONTENTS 

Definition of Terms Used in This Document 1 

Background 3 

Executive Summary 5 

Summary of the Study Results 9 

Recommended District TMDL Strategy 22 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Total Mercury: 

Dissolved Mercury: 
Methyl Mercury: 

Inorganic Mercury: 

Load Allocation: 

Load Reduction: 

TMDL: 

mg/kg: 

ug/l: 

ng/l: 

Dry weight: 


DEFINITIONS OF TERMS USED IN THIS DOCUMENT 


The measured amount of all forms of mercury in a sample of sediment or 
water sample; this includes methyl mercury, dissolved mercury, and 
elemental mercury. If a sample result is reported as “mercury 
concentration,” total mercury is assumed. 

The measured amount of mercury remaining in a water sample that has 
been filtered to remove suspended sediment. 

The most bioavailable and most toxic form of mercury. Methyl mercury is 
formed when anaerobic sulfate-reducing bacteria methylate inorganic 
mercury. 

Inorganic mercury compounds are formed when mercury combines with 
elements other than carbon, such as chlorine, sulfur, or oxygen. 
Elemental mercury is a form of inorganic mercury. 

The mass of mercury that can be released from a specific source on a 
daily or annual basis. 

The mass of mercury needed to be removed from a source to meet the 
load allocation for that source. 

A Total Maximum Daily Load (TMDL) is a plan for restoring water bodies 
that do not support beneficial uses because of impairment caused by a 
pollutant. A TMDL identifies and quantifies sources of the pollutant 
causing impairment, calculates the maximum daily load of the pollutant 
that a water body can receive and still support beneficial uses, and 
assigns load allocations for each source so that this daily (or annual) load 
is achieved. 

Milligrams of measured substance per kilogram of sample weight (also 
expressed as parts per million). A milligram is one-thousandth of a gram 
and one-millionth of a kilogram. The measure is equivalent to 
micrograms per gram (ug/g). Ex: The concentration of mercury in a fish 
sample expressed as milligrams of mercury per kilogram of fish or 
micrograms of mercury per gram of fish. 

Micrograms per liter (also expressed as parts per billion). Ex: The 
concentration of mercury in water expressed as micrograms of mercury 
per liter of water. 

Nanograms per liter (also expressed as parts per trillion). A nanogram is 
one-billionth of a gram, i.e. 10' 9 g. 

If a sediment sample is treated to remove moisture prior to analysis, the 
analytical results are expressed as dry weight. For example: 20mg/kg 
total mercury, dry weight. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Wet weight: 

Hypolimnion: 

Epilimnion: 

Thermocline: 


If a sediment sample is analyzed with the natural water content as 
received, the results are said to be “wet-weight” but wet-weight is not 
always stated. Unless “dry-weight” is stated, wet-weight must be 
presumed. Weight-wet sediment samples understate mg/kg mercury 
concentration by the percentage of moisture content. 

The cold lower layer of a stratified lake, under the epilimnion and 
beginning just below the thermocline. This layer is not directly affected by 
surface events. 

The warm upper layer of a stratified lake, beginning just above the 
thermocline. This layer is directly affected by surface events. 

The distinct interface between surface waters and cooler, deeper waters; 
the region between the warm upper layer (epilimnion) and the lower cold 
layer (hypolimnion) of the lake, where temperature declines abruptly (1C° 
or more per meter) with increasing depth. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


BACKGROUND 

In 1998, the San Francisco Bay Regional Water Quality Control Board (Regional Board) 
reported to the U.S. Environmental Protection Agency (EPA) that certain water bodies in the 
Guadalupe River Watershed did not support designated beneficial uses, in part, due to the 
presence of mercury in fish tissue that exceeded applicable criteria. In 1999, the Regional 
Board approached the recently formed Santa Clara Basin Watershed Management Initiative 
(WMI) to serve as the public stakeholder group for development of a plan for reducing mercury 
in fish tissue and thereby restore the impaired beneficial uses with regard to this specific 
pollutant. The plan is termed a Total Maximum Daily Load (TMDL), and the Regional Board is 
required by the Clean Water Act to develop TMDLs for water bodies that do not support 
beneficial uses. A TMDL identifies and quantifies sources of the pollutant causing impairment, 
calculates the maximum daily load of the pollutant that a water body can receive and still 
support beneficial uses, and assigns load allocations for each source so that this daily load is 
achieved. 

Also in 1999, the Regional Board formed a Mercury Council to develop a TMDL for mercury in 
San Francisco Bay. The Regional Board released a draft TMDL Project Report in June 2000 
that called for a 98% reduction of the load of mercury from the Guadalupe River to the Bay, and 
a 50% reduction of the load of mercury in urban runoff to the Bay. This TMDL, including these 
load allocations, was eventually adopted by the Regional Board in September 2004. The 
timeline in the TMDL requires reducing the load of mercury from the Guadalupe River by and 
annual average of 46 kilograms per year by the end of the first ten years of implementation, and 
by the full annual average of 92 kilograms per year by the end of the next ten years. This 
timeline also applies to the urban runoff load reduction. 

In response to the Regional Board request, the WMI formed a Work Group that was co-chaired 
by a representative of the Regional Board and by a representative of the Santa Clara Valley 
Water District (District). In 2000, the Work Group developed a Work Plan for development of 
the TMDL that was approved by the Core Group of the WMI. In September 2002, the District 
Board approved a staff request to execute a consultant agreement for the study ($884,583), and 
directed staff to negotiate a Memorandum of Understanding (MOU) with the Regional Board. 

In March 2003, the District Board and the Regional Board adopted a MOU that established roles 
and responsibilities for District and Regional Board staff, committed the District and Regional 
Board to use the WMI as the public forum for development of the TMDL, and confirms that 
District current, planned and future efforts to reduce mercury in the environment will be 
accounted for in both the Guadalupe River Watershed TMDL and the San Francisco Bay TMDL. 
The intent is to ensure that Implementation of the Guadalupe River Watershed TMDL will also 
satisfy implementation requirements for the San Francisco Bay TMDL. In the San Francisco 
Bay TMDL adopted by the Regional Board, credit for past activities conducted by the District is 
retroactive to 1998. 

The District’s contribution to the TMDL, as defined in the MOU, is to provide sufficient data and 
interpretation so that the TMDL is based on sound science. This will ensure that allocation of 
loads among source owners and source control measures will achieve the greatest benefit. In 
addition, the MOU ensures the provision and latitude to the District for projects that generate 
benefits greater than just reduction of mercury loading, such as restoration of habitat, thereby 
allowing the District to meet multiple objectives, including other environmental obligations. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Methyl mercury is the toxic form of mercury that enters the food web and bioaccumulates into 
higher trophic levels. The process of mercury methylation occurs primarily at the sediment- 
water interface under a particular set of environmental conditions. Methyl mercury produced 
from microbial processes is soluble and environmentally mobile, quickly entering aquatic food 
webs. Almost all mercury that is bioaccumulated is in the methylated form, primarily as a result 
of the consumption of prey containing methyl mercury. Methyl mercury accumulates in 
carnivorous fish to levels of 100,000 to 1,000,000 times those found in ambient water. 

The focus of the District’s study of mercury in the watershed was to identify where methyl 
mercury is being produced in the watershed, the sources of mercury to those areas, and if there 
are any potential controls for reducing methyl mercury production. In contrast to the San 
Francisco Bay Mercury TMDL, which focuses only on inorganic mercury associated with 
suspended sediment, the Guadalupe River Watershed TMDL will recognize the importance of 
methyl mercury in addition to inorganic mercury in sediment. This will result in an 
implementation plan that prioritizes actions to reduce methyl mercury production by: 

• reducing loads of mercury in sediment to areas where methyl mercury is produced; and, 

• controlling factors associated with increased methyl mercury production 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


EXECUTIVE SUMMARY 

The Santa Clara Valley Water District conducted a study of mercury in the Guadalupe River 
Watershed between March 2003 and December 2004. The purpose of this study was to 
develop the data to support development of a Total Maximum Daily Load (TMDL) for Mercury in 
this watershed based on sound science. The District conducted this study under a 
Memorandum of Understanding with the San Francisco Bay Regional Water Quality Control 
Board (Regional Board) in part, to ensure that a single Implementation Plan would be developed 
to address mercury in the watershed and in San Francisco Bay. 

The TMDL for the watershed is required because fish tissue concentrations of mercury in fish 
collected from various water bodies in the watershed exceed applicable criteria for human 
consumption. The study was conducted because of the lack of information regarding mercury 
sources, fate and transport, and lack of understanding of the linkage between mercury in 
sediment and mercury in fish tissue. 

The study included four main bodies of work: 

• An initial review of all available data related to mercury in the watershed. 

• A reconnaissance-level survey of the watershed to identify sources of mercury, collect 
soil and water samples for mercury analyses, and develop dry season load estimates of 
mercury and methyl mercury. 

• Development of a conceptual model of mercury impact and transport in the watershed. 

• Collection of soil, water and fish data to address data gaps identified in the conceptual 
model, test assumptions contained in the model, and develop wet season load 
estimates of mercury and methyl mercury. 

The key findings of the study are: 

• Mercury loads from the mining district to the reservoirs and to the creeks downstream of 
the reservoirs are significant and are about 10 times the loads measured in 
“background” areas away from the sites of mercury mining. 

• The largest source of mercury in the watershed is in-stream bank and bed deposits of 
sediment and mine wastes, primarily in Alamitos and Guadalupe Creeks, and most of 
this in-stream load of total mercury is mobilized during storm flows. 

• Most of the in-stream bed load of mercury is attached to sediment from Alamitos and 
Guadalupe Creeks, and is trapped in Lake Almaden and in the impound area (recharge 
basin) behind the Alamitos Drop Structure, respectively. 

• Water transfers through the Almaden-Calero Canal is a significant source of mercury to 
Calero Reservoir. 

• Loads of total mercury in the water column into Almaden, Calero and Guadalupe 
Reservoirs are greater than loads exiting the reservoirs to downstream creeks. 

• Loads of total mercury in the water column into the Alamitos Drop Structure impound 
area (recharge basin) and into Lake Almaden are greater than the load exiting the Drop 
Structure to Guadalupe River. 

• The load of total mercury in the water column exiting Guadalupe River to the Bay is 
greater than the collective load into the River from (a) mining district tributaries; (b) non¬ 
mining district tributaries, and (c) urban runoff. 

• Mercury concentrations in all adult fish collected from all reservoirs exceed the 
applicable criterion for human consumption. Nearly all mercury in fish occurs as methyl 
mercury. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


• Deposition of mercury from the atmosphere results in mercury concentrations in adult 
fish that exceed the applicable criterion for human consumption. 

• Mercury concentrations in adult and Age-1 fish from Guadalupe, Almaden and Calero 
Reservoirs and Lake Almaden are two to ten times higher than in adult and Age-1 fish 
collected from reservoirs affected only by atmospheric deposition and local un-mined 
geologic sources of mercury (Lexington, Stevens Creek, and Anderson Reservoirs). 

• Mercury concentrations in Age-1 fish collected below the reservoirs from streams 
impacted by mercury from the mining district (Alamitos Creek, Guadalupe Creek, 
Guadalupe River) decrease with distance downstream (from 0.39 to 0.08 mg/kg), and 
are three to thirteen times higher than mercury in fish (0.03 mg/kg) collected from a 
stream (Los Gatos Creek) not affected by mercury from the mining district. 

• Almaden and Guadalupe Reservoirs produce significant amounts of methyl mercury, 
and this is associated with seasonal depletion of oxygen in the hypolimnion of the 
reservoirs. 

• Methyl mercury concentrations in the water column decrease with distance downstream 
of the reservoirs during the dry season. 

• Mercury concentrations in fish are correlated with methyl mercury concentrations in the 
water column. 

The key implications of the study are: 

• Mercury loads need to be reduced, particularly those loads that enter sites where methyl 
mercury production is significant, including the reservoirs, Lake Almaden, and the 
flooded area behind the Alamitos Drop Structure. 

• Methyl mercury production needs to be reduced at sites where its rate of production is 
significant, including the reservoirs, Lake Almaden, and the flooded area behind the 
Alamitos Drop Structure. 

The TMDL for mercury in San Francisco Bay assigned load allocations based only on total 
mercury concentrations in the water column, and included an allocation for Guadalupe River. 
This allocation, expressed as 200ng/g total mercury in suspended sediment in the water 
column, will be included in the TMDL for mercury in the Guadalupe River. The Bay TMDL 
established a correlation between mercury concentrations in sediment and methyl mercury 
concentrations in fish from the Bay. The target concentrations for methyl mercury in fish from 
the Bay were used to establish the load allocations for the sources of total mercury in the 
suspended sediment in the water column to the Bay. 

In the Guadalupe River Watershed, a meaningful correlation between mercury in sediment 
samples and methyl mercury in fish samples was not observed. Nor was there a correlation 
between total mercury in samples from the water column and methyl mercury in fish samples. 
However, a correlation between methyl mercury in samples from the water column and methyl 
mercury in fish samples was observed. This will result in load allocations in the Guadalupe 
River Watershed TMDL expressed in terms of total mercury (for the load to the Bay) and methyl 
mercury (for loads within the watershed) in the water column. 

The Guadalupe River Watershed TMDL will contain numeric targets for mercury in fish, mercury 
in water and sediment, and methyl mercury in water that are protective of humans and wildlife 
exposed to mercury via consumption of fish. The load allocations in the TMDL will require 
reductions for the following types of loads of mercury in the water column: 

• total mercury loads in the water column to the reservoirs from tributaries draining the 
mining district; 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


• total and methyl mercury loads in the water column from the reservoirs to downstream 
creeks; 

• total mercury loads in the water column to downstream creeks from tributaries draining 
the mining district; 

• total mercury loads in the water column to Lake Almaden and to the Alamitos Drop 
Structure from in-stream bed and bank erosion; 

• total and methyl mercury loads in the water column from Lake Almaden and the Alamitos 
Drop Structure to the main stem of the Guadalupe River; 

• total mercury loads in the water column to Guadalupe River from urban runoff equal to 
the Bay TMDL; and, 

• total mercury load in the water column from Guadalupe River to the Bay equal to the Bay 
TMDL. 

From the perspective of the Regional Board, responsibility for meeting load allocations will rest 
with current property owners, and will be enforced by the Regional Board under their existing 
authorities derived from the Porter-Cologne Water Quality Act and the Clean Water Act. The 
Bay TMDL provides twenty years to achieve the load reductions from all sources, and estimates 
that full recovery of the Bay may take another century beyond that, due to the mercury already 
existing in the Bay sediments. The Guadalupe River Watershed TMDL will include a similar 
reasonable time period for achieving load reductions, but it is anticipated that the time required 
for at least partial restoration of the beneficial uses (e.g. relaxation from an outright ban of 
consumption to a restricted consumption of fish) will be much shorter. However, the 
importance of atmospheric deposition as a contributor to mercury in fish tissue was 
demonstrated by this study. Achieving non-restricted consumption of fish from all water bodies 
in the watershed (and possibly the Bay) is unlikely to occur until global sources of atmospheric 
mercury are reduced. 

The recommended strategy for the District is as follows: 

• Quantify mercury removal and estimated load reductions already achieved by the 
construction of the Lower and Downtown Guadalupe River Flood Protection Projects, the 
Guadalupe Creek Restoration Project, and annual stream maintenance activities already 
completed since 1998. This will determine the credit available to the District to apply 
toward the Bay TMDL load reduction requirement. 

• Incorporate and quantify mercury removal and load reductions into the Upper Guadalupe 
River Flood Protection Project. 

• Recognize mercury removal benefits of ongoing and planned routine stream 
maintenance programs in the watershed. 

• Incorporate mercury as a criterion for prioritizing erosion control activities. 

• Evaluate the potential of using Pond A8 as a repository for sediment mobilized under 
high flow conditions as part of a multi-objective approach to providing flood protection 
and restoration of habitat. 

• Establish an annual goal for mercury removal projects as a percentage of all stream 
maintenance activities in the watershed as part of a multi-objective approach to meeting 
goals of stream restoration, habitat enhancement, property protection, and mercury load 
reduction. 

• Develop and implement a routine maintenance program to remove sediment from 
behind the Alamitos Drop Structure, at the inlet to Lake Almaden, and at other sediment 
accumulation sites. 

• Investigate and implement methods to reduce methyl mercury production in reservoirs, 
Lake Almaden, and behind the Alamitos Drop Structure as part of a multi-objective 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


approach to meeting goals of improved fisheries, improved water quality, reduced water 
treatment costs, and methyl mercury reduction in water and fish. 

• Develop a long term plan for restoration of the Lake Almaden-Alamitos Drop Structure 
area, including sediment removal, reducing methyl mercury production, improving fish 
passage, and enhancing habitat and recreational opportunities. 

• Evaluate the potential of retiring Almaden Reservoir and/or Guadalupe Reservoir as part 
of a long-term approach to restoration of Alamitos Creek and Guadalupe Creek. 

• Develop staff expertise in monitoring and sampling water, sediment and biota to address 
mercury and other existing or potential pollutants. 


This strategy addresses the Cleaner, Greener, Leaner goals of the District: 

• Cleaner: 

o Improved water quality for fisheries in the reservoirs and downstream creeks 

• Greener: 

o Restored and enhanced environment in the reservoirs and downstream creeks 
o Improved fish habitat and related food cycle and wildlife habitat in the reservoirs 
and downstream creeks 
o Improved recreational opportunities 

• Leaner: 

o Utilization of existing projects and other proposed multi-objective projects and 
activities to simultaneously address stream stewardship, flood protection, and 
water supply interests 

o Proactive action to minimize regulatory administrative burden 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


SUMMARY OF THE STUDY RESULTS 

The District championed a comprehensive approach to conducting the study, utilizing the public 
stakeholder group to provide review and comment on draft work products, and to reach 
consensus on the direction of the study as it progressed. A Technical Review Committee was 
formed to provide independent, third-party expert review of the Draft Conceptual Model and the 
Draft Data Collection Plan. The work products produced by the consultant are listed below and 
are available on the District’s web site: 

• Preliminary Problem Statement 

• Synoptic Survey Plan and Report 

• Draft Final Conceptual Model Report 

• Data Collection Plan and Report 

Preliminary Problem Statement 

The initial work product of the study was a Preliminary Problem Statement Report that 
summarized existing data and information in the watershed. The report provided: 

• Background information on the watershed setting for the TMDL by summarizing 
important water quality, pollutant discharge, land-use, and resource protection issues. 

• A description of the water quality impairment which necessitated the TMDL development 
that includes the identification of the water body segments for which the TMDL is being 
developed and the potentially applicable water quality standards for mercury. 

• A description of the current understanding of processes and factors controlling mercury 
in the watershed, emphasizing that a mechanistic understanding of the fate, transport 
and bioaccumulation processes of mercury in the watershed, based on locally collected 
data, is essential to the development of a successful TMDL. 

Synoptic Survey 

The Synoptic Survey, conducted during the dry season (Summer 2003), was a field 
reconnaissance of the watershed to visually identify sites of significant erosion, mine waste 
deposits, and creek vegetation, and also included collection of fish from Guadalupe Reservoir 
and sediment and water samples from various locations in the watershed. The Synoptic Survey 
was designed to meet two primary objectives: 

• Complete a visual inspection to provide a general view of mercury contamination in the 
watershed. The survey had wide spatial coverage surveys for wetland vegetation 
(Figure 1), sediment erosion and accumulation sites, and to identify areas of existing 
deposits of mercury mine waste (Figure 2). 

• The second objective was sampling to produce an early indication of key locations 
where transformation of solid phase mercury to bioavailable mercury is and is not 
occurring in the surface waters of the Guadalupe Watershed that drain to the tributaries, 
outfalls, Guadalupe River, and the Bay. Samples for chemical analyses were collected 
at 24 different locations in the creeks and reservoirs, using a consistent set of sampling 
and analytical methods. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Draft Final Conceptual Model 

The Preliminary Problem Statement Report and the Synoptic Survey Report provided sufficient 
information to develop a Draft Final Conceptual Model for the impact and transport of mercury in 
the watershed. The Draft Final Conceptual Model Report used data from the two reports to 
identify important sites of methyl mercury production during the dry season, to estimate mercury 
loads from atmospheric deposition, to estimate loads in reservoir inlets and outlets, to estimate 
in-stream loads, and to estimate loads from the Guadalupe River to the Bay. 

In the model, the system is divided into five groups of water bodies: 

• Reservoirs 

• Streams and creeks in the upper watershed (above Ross Creek) draining the historic 
mercury mine areas 

• Creeks in the upper watershed draining areas not known to contain mines 

• Guadalupe River downstream of Almaden Lake to St. Johns Street 

• Guadalupe River from St. Johns Street to Alviso Slough 

Overview of Conceptual Model 

Most of the mercury remaining in the watershed seems to exist as relatively insoluble mercury 
sulfides in mine wastes that have accumulated in reservoir deposits and sediments, and in 
stream bottoms, banks and flood plains. Because of the strong association of mercury with 
solids, the movement of mercury in the watershed is closely tied to the transport of sediments. 
Sediment mercury concentrations in the creeks exhibit a significant and consistent decline with 
distance downstream of the mining area. 

The conceptual model indicates the following: 

• Wet season high flows deliver practically all of the total mercury transported in the 
watershed. 

• The four major reservoirs, Lexington, Almaden, Guadalupe and Calero are sinks for 
total mercury; they all release less total mercury than they receive. 

• Inputs of mercury derived from mine wastes are substantially greater than atmospheric 
deposition inputs for Guadalupe and Almaden Reservoirs, and for Alamitos and 
Guadalupe Creeks. 

• Atmospheric deposition appears to account for a significant fraction of the mercury input 
to both Calero and Lexington Reservoirs. 


Data Collection Plan and Report 

The Data Collection Plan included seven elements, each of which was intended to address 
specific questions and hypotheses developed by the public stakeholder group. The data from 
Sampling Elements 1 through 4 resulted in the estimation of wet season loads of total, 
dissolved, and methyl mercury within the watershed and from Guadalupe River to the Bay. 
These data will be the core of the TMDL regarding loads and load allocations. The estimated 
loads for the wet season are shown on Figures 3 and 4. The sampling elements to develop 
these load estimates were as follows: 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


® Sampling Element 1 collected data to estimate the contribution of mercury in runoff from 
the tributaries to the reservoirs, providing estimates of the “background” mercury load 
(defined as the sum of atmospheric deposition and local un-mined geologic sources) and 
the relative increased load due to mercury in tributaries draining the mining district 
(identified as “mines” on Figure 3). Background loads of total mercury to Almaden, 
Calero and Guadalupe Reservoirs range from 13.9 to 27.5 grams per season. The 
background load to Lexington Reservoir is estimated to be 112 grams per season, 
comparatively larger due to its much larger watershed. Similarly, methyl mercury from 
the mining district sources is higher than background sources. 

® Sampling Element 2 collected data to estimate the contribution of mercury in runoff from 
in-stream mobilization of bank and bed sediment in Alamitos, Guadalupe and Calero 
Creeks. The total mercury load appears to decrease in Guadalupe Creek with distance 
downstream of Guadalupe Reservoir, with about 61% of the load retained in the creek 
and behind the Alamitos Drop Structure. The total mercury load appears to increase 
significantly in Alamitos Creek between Almaden Reservoir and its confluence with 
Calero Creek (indicating in-stream mobilization of sediment as a source of mercury in 
the water column), with about 31% of the load retained in Alamitos Creek, Lake Almaden 
and behind the Alamitos Drop Structure. The total mercury load appears to decrease in 
Calero Creek with distance downstream of Calero Reservoir, with about 33% of the load 
retained in the creek. Methyl mercury loads behave similarly. 

® Sampling Element 3 provided data to estimate the contribution of mercury in urban 
runoff. The data show that, for most urban drainages, the contribution of total and 
methyl mercury in urban runoff is about the same order of magnitude as the contribution 
from background sources. 

® Sampling Element 4 provided data to determine what happens to the mercury as it 
reaches the main stem of the Guadalupe River and how much is discharged to the Bay. 
The estimated total mercury load to the Bay (9956.3 grams per season) is about 12 
times higher than the estimated loads into the River from all sources (821.4 grams per 
season), indicating in-stream mobilization of sediment as a source of total mercury in the 
water column. The methyl mercury load to the Bay (26.7 grams per season) is over 3 
times higher than the estimated loads into the River from all sources (7.4 grams per 
season). 

Load estimates were calculated separately for the wet and dry season because of the 
dramatically different flow conditions in each season. For comparison, the daily load 
estimates of total mercury for the dry season, derived from the Synoptic Survey data, are 
shown on Figure 5. The dry season data indicate that: 

• Total mercury entering the reservoirs from atmospheric deposition and (for Calero 
Reservoir) transfers from San Luis Reservoir, range from 0.011 grams per day (as 
shown or 1.3 grams per season) to 0.1 grams per day (12 grams per season). During 
the dry season, there is no significant flow from the mining areas upstream of the 
reservoirs. 

® Total mercury exiting the two reservoirs (Almaden and Guadalupe Reservoirs) in the 
historic mining area is a significant source (0.11 grams and 0.27 grams per day, as 
shown, or 13.2 and 32.4 grams per season) and each is greater than the load from 
Calero Reservoir, which is in the non-mining area (0.03 grams per day, as shown, or 3.6 
grams per season). The total mercury load from Lexington Reservoir, which is also in 


12 



Executive Summary Report: Guadalupe Watershed Mercury Study January 20, 2005 


the non-mining area, is estimated to be 0.73 grams per day (87.6 grams per season), 
due to its much larger volume of dry season releases. 

The dry and wet season loads of total mercury exiting the reservoirs are compared below: 

Almaden Reservoir 

• Dry Season Load: 13.2 grams (to Alamitos Creek) 

• Wet Season Load: 111.8 grams (to Alamitos Creek) 

190.2 grams (to Calero Reservoir) 

Guadalupe Reservoir 

• Dry Season Load: 32.4 grams (to Guadalupe Creek) 

• Wet Season Load: 149.2 grams (to Guadalupe Creek) 

Calero Reservoir 

• Dry Season Load: 3.6 grams (to Calero Creek) 

• Wet Season Load: 27.7 grams (to Calero Creek) 

Lexington Reservoir 

• Dry Season Load: 87.6 grams (to Los Gatos Creek) 

• Wet Season Load: 141 grams (to Los Gatos Creek) 

• Methyl mercury loads (not shown on Figure 5) exiting the two reservoirs in the historic 
mining areas (Almaden and Guadalupe Reservoirs) during the dry season are significant 
sources (7.6 grams and 14.2 grams per season) and are greater than the loads from 
Calero Reservoir (2.6 grams per season) and Lexington Reservoir (5.2 grams per 
season). The dry and wet season loads of methyl mercury exiting these reservoirs are 
compared below: 

Almaden Reservoir 

• Dry Season Load: 7.6 grams (to Alamitos Creek) 

• Wet Season Load: 0.8 grams (to Alamitos Creek) 

0.8 grams (to Calero Reservoir) 

Guadalupe Reservoir 

• Dry Season Load: 14.2 grams (to Guadalupe Creek) 

• Wet Season Load: 1.4 grams (to Guadalupe Creek) 

Calero Reservoir 

• Dry Season Load: 2.6 grams (to Calero Creek) 

• Wet Season Load: 0.3 grams (to Calero Creek) 

Lexington Reservoir 

• Dry Season Load: 5.2 grams (to Los Gatos Creek) 

• Wet Season Load: 0.9 grams (to Los Gatos Creek) 

• In the dry season, total mercury concentrations increase with distance downstream of all 
of the reservoirs, but methyl mercury concentrations decrease with distance downstream 
of all reservoirs. This indicates that the amount of methyl mercury produced in the 
creeks is less than that produced in the reservoirs. 


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Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Wet Season Total Mercury Loads 

(10/1/2003 to 5/31/2004) 



Background 
112.0 g 


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Background o 

1999 '$//////////*' 


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\ \ 

149.2 g ^ ^ ^ 

^ Guadalupe Creek 
Background \ 


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Background I Urban Runoff 
40.5 g I 88.9 g 



58.1 g 


11.7 g 


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^\^55.4g 


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\\ Guadalupe River 
\ below Almaden Laki 

to St. Johns St. \N995^g 



Background 
27.5 g 


190.2 g 


'*7777777777 % I 

\ $ N N 355.49 

\ \ 515.3 g \ X 

in an \ ., , , \ ^ \ AlamitosCreek \ 

ni.bg ^ Alamitos Creek V_— O . . « \ 

O . OlMwko below confluence O 

\ above confluence _ . _ . \ 

^withCaleroCreek X w,thCaleroCreek ^ 

'b/z/ Z/s/S/M J77 ////////7X 

18.0 g i 


Urban Runoff 

1.7 g 


Central Valley 


Calero 

Reservoir 


Background 
9.6 g 


27.7 g 


Calero Creek 


Background 

12.7 g 


Urban Runoff 
17.3 g 


56.4 g 


Background 
13.1 g 


Background 
13.9 g 


Background 
10.3 g 


Urban Runoff 
2.4 g 


Ross Creek 


| Urban Runoff 
28.1 g 


113.5 g 


Canoas 

Creek 


Urban Runoff 
43.7 g 


Background 

24.6 


To South 
San Francisco Bay 


- Arrows are proportional to estimated mass 
transport 

Boxes are proportional to estimated source 
mass. 

Uncertainty 

Low 

Medium 

High 

(1//////////X 

$ $ 

^ 303(d) Impaired Waterbody List 


Figure 3: Graphical depiction of total mercury pathways through the Guadalupe River Watershed. All loads are in grams. 


14 





















































Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Wet Season Methyl Mercury Loads 

(10/1/2003 to 5/31/2004) 


Background I ■ Urban Runoff 
0-2 9 i 0.6 g 



Background 9 
1.1 g 


^ 7777777777 ^ 

-p— ^ Mg 

Mines N - 

O- 4 9 \ Guadalupe 

V Reservoir \ 

- ►V \ 

Background \ 

°'° 9 



01 g ¥77777777777 

Ji 

— *4 ^ 

Background O' 

019 \kzzzzz/zzz7x 


1.0 g 


W77777777. 

% 

Guadalupe River 
\below Almaden Lake' 
^ to St Johns St. ^ 




:777777777777 

\ X 

\ Alamitos Creek \ 
N above confluence N 
^ with Calero Creek ^ 

'$/////7////k 


*{7777777777^ 


Background 
0.1 g 


^ | „ L„ 

-\ below confluence XT 

^ with Calero Creek X 

jkzTZZZZZZA 

- i Background Urban Runoff 

0.1 g ■ 0.2 g 


Background 

0.1 g 



To South 
San Francisco Bay 


Background 
0.1 g 



Arrows are proportional to estimated mass 
transport 

Boxes are proportional to estimated source 
mass. 

Uncertainty 

Low 

Medium 

High 


f 1 
I I 


303(d) Impaired Waterbody List 


Figure 4: 


Graphical depiction of methyl mercury pathways through the Guadalupe River Watershed. All loads are in 
grams. 


15 













































Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 




Total 

Hg = 1.37 njy/ 

4 ~ 

Total Methyl 

Hg * 0.57 ng/r 

- A 

Sediment Concentration ■ 0.03 mg/kg 


Total Hg = 12.8 ng 1 ' 
Methyl Hg - 076 ngi 
Flow = 23 cfs 
Load = 0 73 g 


Lexington Reservoir 



Total 

Hg = 10.6 ng/r 

A" 

Total Methyl 

Hg = 3.3 ng it 

4 

Sediment Concentration - 2.4 mg/kg 


Total Ho = 18.9 ng/< 
Methyl Hg = 8.27 ng/' 
Flow - 5.9 els 
Load = 0 27 g 


Guadalupe Reservoir 





Total 

Hg « 5.6 ng/r 

4 : 

Total Methyl 

Hg « 2.26 ng/r 

TL 4 

Sediment Concentration = 27 mg/kg 


Total Hg - 7 5 ng/< 
Methyl Hg = 4 3 ng/< 
Flow = 6 cfs 
Load = 0.11 g 


AlmadenCalero Canal 


Almaden Reservoir 




Total 

Hg = 3.2 ng/r 

4‘ 

Total Methyl 

Hg * 0.04 ng/r 

*1 4 

Sediment Concentration =o.04 • 0.06 mg/kg 


How = 5 4 cfs 
Load = 0.04 g 





Total 

Hg = 38.9 ng/r 

4 

Total Methyl 

Hg = 1 ng/r 

** 4 

Sediment Concentration =21.9-125.3 mg/kg 


Row = 6 ds 
Load = 0 56 g 


Daily Summer loads and Concentrations 
(JULY 28 - AUGUST 1, 2003) 



Total 

Hg = 17.6 ng/r 

A 

Total Methyl 

Hg = 0 36 ng/r 

"\ 4 

Sediment Concentration = 0.6-1. i mg/kg 


Total 

Hg = 26 ng/r 

4: 

Total Methyl 

Hg = 0.3 ng/r 

*:4 

Sediment Concentration =19.7-168.5 mg/kg 


Flow = 9 6 els 
Load = 0.16 g 



^DataJ 


Total 

Hg - 3.8 ng/r 

4 “ 

Total Methyl 

Hg = 1.35 ng/r 

4 

Sediment Concentration = 0.08 mg/kg 


Total 

Hg = ng/r 

4“ 

Total Methyl 

Hg = ng/r 

*: 4 

Sediment Concentration = 0.11 mg/kg 


Row = 0 cfs 
Load = 0 g 


Row = 0 8 ds 
Load = 0 004 g 


^/Urban Runofh 
Og/day j 

f 

Total 

Hg = 105 ng'r 

4 

Total Methyl 

Hg = 0.32 ng/r 

4 

Sediment Concentration =2.8-10mg/kQ 0 



Flow = 3-15 ds 
Load = 0 75-4 g 


Total 

Hg* 28.2 ng/r 

4 “ 

Total Methyl 

Hfl«_ng/r 

^ A 

Sediment Concentration =1-6 mg/kg 


Row = 3 ds 
Load = 0 19 g 


- To South 
San Francisco Bay 


y Guadalupe River, 

^ - Downstream of 

'Sediment \ Almaden Lake to 

Removal ) St. Johns St. 

Kj8.3g/dM/ 


Notes 


Guadalupe River, 
St. Johns St. 
' Sediment\ to Atvlso Slough 

Removal 
\48 2g/day 


1) Flow estimates are from the District's web site lor hydrologic data, 

http:/ alert.va 1 leywat er.org 

2) Water column concentration data are from the Synoptic Survey, 
except for data on Guadalupe River from Coleman Avenue to San 
Francisco Bay, which was a basetlow value reported in Thomas et 
al., 2002. 

3) Sediment data, are from the Synoptic Survey, 

Thomas et al., 2002, and WCC, 1992. 

4) Mercury concentration in fish identified by degree of shading: 


! ; '0ata.rJ No fi 8 * 1 data 

<0.5 ppm 
0.5-1.0 ppm 
1.0-1.5 ppm 
2.0 ppm 


Fish Species 

;{] Black cripple 


. ... * 

V 

-c? 


: Largemouth Bass 


" 


Figure 5: Graphical depiction of total and methyl mercury pathways through the Guadalupe River Watershed in the dry 
season. All loads are in grams. 


16 





































































Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


• Sampling Element 5 provided information regarding the mercury content of bank and 
bed sediments in Guadalupe River, Guadalupe Creek, and Alamitos Creek. The data 
show that mercury concentrations decrease with distance from the mining district, 
ranging from 40 mg/kg above the Alamitos Drop Structure to 0.3 mg/kg at Highway 
237. The data show that Lake Almaden and the Alamitos Drop Structure are obstacles 
to the transport of bed load sediment from the most contaminated creeks to 
Guadalupe River. Control measure activities in this area will be a critical component of 
the TMDL Implementation Plan. 

• Sampling element 6, conducted during the dry season of 2004, was made possible by 
collaboration between the District and EPA. The District had the necessary permits 
and staff resources to collect fish from the creeks below the reservoirs. EPA provided 
the equipment and staff (supplemented with District biologists) to collect fish from Lake 
Almaden and from Almaden, Calero, Guadalupe, and Lexington Reservoirs, and for 
laboratory analyses of the fish samples. District staff collected fish from Los Gatos, 
Alamitos, and Guadalupe Creeks, and from Guadalupe River. 

Adult Largemouth Bass 

Total mercury concentrations were measured in muscle tissue samples from adult largemouth 
bass collected from Lake Almaden and from four reservoirs in the watershed (Table 1). 

Table 1 

Summary of Adult Largemouth Bass Mercury Data 


Total Mercury Concentrations 

(mg/kg wet)Total Length (cm) 


Water body 

Sample 

Size 

Average 

Min. 

Max. 

Coefficient 
of Variation 

Average 

Min. 

Max. 

Coefficient 

of 

Variation 

Guadalupe Reservoir 

18 

6.1 

3.1 

13 

0.40 

41.8 

30.7 

53.2 

0.18 

Almaden Reservoir 

20 

4.3 

2.2 

7.4 

0.30 

43.9 

33.8 

51.2 

0.11 

Lake Almaden 

20 

2.3 

1.1 

3.8 

0.34 

41.8 

31.2 

53.2 

0.16 

Calero Reservoir 

20 

1.1 

0.8 

1.6 

0.16 

36.7 

29.7 

47.7 

0.12 

Lexington Reservoir 

11 

0.6 

0.4 

1.0 

0.27 

40.8 

35.8 

50.2 

0.12 


While all of the samples exceeded the State and Federal criterion of 0.3 mg/kg (for human 
consumption of fish), there were distinct differences in the fish mercury concentrations 
between the water bodies sampled. The mercury concentrations in adult largemouth bass in 
the immediate vicinity of the mining district are some of the highest fish mercury levels found 
to date in California. The maximum mercury concentrations in adult largemouth bass at 
Guadalupe and Almaden Reservoirs and Lake Almaden ranged from 3.8 - 13 mg/kg. In 
comparison, the maximum mercury concentration in largemouth bass muscle tissue measured 
statewide in the Surface Water Ambient Monitoring Program between 1986 and 2001 was 3.5 
mg/kg. 

Comparison to Regional Data 

The Surface Water Ambient Monitoring Program (SWAMP) Report for the San Francisco Bay 
Region prepared by the San Francisco Bay Regional Water Quality Control Board describes 
surveys of reservoirs in which edible fish were collected and their tissues analyzed to 

17 






Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


determine the concentrations of contaminants, including mercury, which may affect human 
health. Mercury concentrations were measured in largemouth bass in nine reservoirs in 
Marin, Contra Costa, Alameda, and Santa Clara Counties (Table 2). The comparison shows 
that the concentrations of mercury in largemouth bass from Lexington Reservoir and Calero 
Reservoir, not directly affected by the mining district, are similar to mercury concentrations 
reported for adult largemouth bass at other locations throughout the San Francisco Bay 
region. The comparison also shows that the concentrations of mercury in largemouth bass 
from the water bodies in the vicinity of the mining district area of the Guadalupe Watershed 
(Almaden Reservoir, Guadalupe reservoir, Lake Almaden) are elevated above the 
concentrations in the other reservoirs sampled in the San Francisco Bay area. 


Table 2 

Water bodies Listed by Decreasing Mercury Concentrations (mg/kg wet wt) 
Standardized For A 40 Cm Largemouth Bass 


Highlighted and italicized^ reservoirs are from the 2004 SWAMP database. 


Water body 

Total Hg (mg/kg) 

Guadalupe Reservoir 

5.8 

Almaden Reservoir 

3.6 

Lake Almaden 

2.1 

Stevens Creek Reservoir 

1.4 

Anderson Reservoir 

1.3 

Calero Reservoir 

1.2 

Soulajule Reservoir 

1.1 

Del Valle Reservoir 

0.9 

Nicasio Reservoir 

0.8 

Lexington Reservoir 

0.6 

Lake Chabot 

0.6 

Lafayette Reservoir 

0.4 


• Sampling element 7, conducted during the dry season of 2004, was a focused study to 
evaluate the production of methyl mercury in Almaden and Guadalupe Reservoirs over 
the dry season. Methyl mercury is the chemical form of mercury most directly linked to 
uptake by biota. An understanding of methylation processes in reservoirs is needed to 
develop the linkage between mercury in the water column and mercury in fish. 
Elevated methyl mercury concentrations were measured in the hypolimnion and 
epilimnion of the reservoirs in the Synoptic Survey, but the zone of production of the 
methyl mercury is not known. 

Data on total and methyl mercury collected during the dry season, 6 times over a fourteen- 
week period, demonstrated clearly the gradual buildup of methyl mercury in Almaden and 
Guadalupe Reservoirs. Much of the methyl mercury generated in the reservoirs was 
produced in the hypolimnion, which is where the withdrawals for downstream supply take 
place. The most significant production of methyl mercury occurred when the hypolimnion 
was depleted of oxygen (dissolved oxygen concentrations less than 1 mg/I, Figure 6). 


18 





Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



May 


September 


Methyl 

Mercury 

Dissolved 

Oxygen 



May 


September 


Figure 6: Methyl Mercury Production and Dissolved Oxygen Depletion 


19 






Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Project Summary 

This project has produced a comprehensive set of data and data interpretations for use in 
development of a science-based TMDL for mercury in the Guadalupe River Watershed. In 
addition to providing technical information about numeric targets for the TMDL, the study has 
provided insight into implementation activities that will meet the targets effectively and 
efficiently. 

The TMDL will contain numeric targets for mercury in fish, mercury in water and sediment, 
and methyl mercury in water that are protective of humans and wildlife exposed to mercury via 
consumption offish. This will result in load reduction requirements as follows: 

• total mercury loads to the reservoirs from tributaries draining the mining district; 

• total and methyl mercury loads from the reservoirs to downstream creeks; 

• total mercury loads to downstream creeks from tributaries draining the mining district 
and from urban runoff; 

• total mercury loads to Lake Almaden and to the Alamitos Drop Structure from in- 
stream bed and bank erosion; 

• total and methyl mercury loads from Lake Almaden and the Alamitos Drop Structure to 
the main stem of the Guadalupe River; 

• total mercury loads to Guadalupe River from urban runoff; and, 

• total and methyl mercury loads from Guadalupe River to the Bay. 

The data indicate that significant mercury sources remain in the mining district, and mercury is 
transported primarily during storm events in drainages from the mining areas, including 
Randol Creek, Golf Creek, McAbee Creek, and Deep Gulch to creeks below the reservoirs, 
and Jacques Gulch and Los Capitancillos Creek to Almaden Reservoir and Guadalupe 
Reservoir, respectively. Sources of mercury are sediments eroding into the drainage and 
transported by flows, as well as erosion of the drainage banks and beds. The TMDL will 
establish load allocations for these drainages. The load allocations may be based on 
sediment concentration, suspended sediment concentration, water column concentration, or a 
combination of these. Some of the methods for achieving load reductions will be creek 
restoration, comprising sediment removal and erosion control within the District’s ownership 
and easement areas. 

Total mercury load allocations will also appear in the TMDL for Alamitos Creek, Guadalupe 
Creek, and Guadalupe River. These allocations may also be based on sediment 
concentration, suspended sediment concentration, water column concentration, or a 
combination of these. Again, some of the methods for achieving load reductions will be creek 
restoration, comprising sediment removal and erosion control within the District’s ownership 
and easement areas. 

In addition to total mercury, the TMDL process recognizes the importance of methyl mercury 
and the need to reduce its production at the same time that total mercury loads are being 
reduced. The TMDL will require load reductions of total and methyl mercury for the water 
bodies of the Guadalupe River watershed. However, reduction of total mercury exiting these 
water bodies is wholly dependent on reducing the sources of mercury entering these water 
bodies. Until the inputs are controlled, management of the water bodies to minimize the 
production of methyl mercury may be the only feasible choice. The District’s best choice is 
methylation control coupled with stream restoration where waste is present on District lands, 
but this must be coupled with erosion control of mine waste inputs from the upstream lands of 
others, especially the New Almaden and Guadalupe mines. 


20 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


The Implementation Plan of the TMDL will prescribe a control program that satisfies the load 
allocations within the watershed and the load allocation from Guadalupe River to the Bay, and 
the major areas where actions will be needed are depicted in Appendix A. Control programs 
for mercury have emphasized a combination of decreasing/eliminating mercury loads, 
natural/intentional burial of contaminated sediment, and reducing methyl mercury production. 
From the perspective of the Regional Board, responsibility for meeting load allocations will 
rest with current property owners, and will be enforced by the Regional Board under their 
existing authorities derived from the Porter-Cologne Water Quality Act and the Clean Water 
Act, enforced through the Basin Plan and permitting authority. 

Decreasing or eliminating loads is a critical first measure, as it begins to reduce sediment 
mercury levels and the stock of new mercury to be methylated, and is usually the early 
emphasis of control programs. Dredging and removal or capping of contaminated sediment is 
employed less often than natural burial, primarily because of cost. Natural burial is 
problematic, due to the unpredictable behavior of sediments in active systems. Controlling 
methyl mercury production is a new frontier in restoration, since the factors involved are only 
now beginning to be well understood. However, it may be the best choice in certain 
situations, where other methods would be too environmentally destructive. 

The District is in a unique position with respect to the TMDL. While not responsible for the 
initial and continuing release of mercury to the water bodies from the original source area, the 
District may be responsible for addressing mercury as a result of its land ownership, 
constructed facilities, and jurisdictional responsibilities. Fortunately, the District incorporated 
into a special tax approved by the electorate funds earmarked for addressing mercury issues, 
and, more importantly, most of the control measures that will be needed are essentially 
extensions of existing projects and programs the District already implements. 


21 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


RECOMMENDED DISTRICT TMDL IMPLEMENTATION STRATEGY 

The District’s strategy to address mercury in the watershed is comprehensive and flexible, in 
that the entire watershed is being continuously assessed, and resources are applied where 
they are needed most. For convenience, the strategy is categorized according to major 
portions of the watershed (Figure 7). 

Main Stem Guadalupe River 

The main stem of the Guadalupe River is defined as extending from the downstream end of 
the Alamitos Drop Structure to the Bay. The emphasis in this portion of the watershed is 
reducing mercury loads to the Bay. Mercury sources under District control are bed and bank 
erosion. The study indicates that total mercury loading from this portion of the river is 
primarily due to in-stream processes. Methyl mercury production does not seem to be a major 
concern in this portion of the watershed, based on the fish tissue data and the water quality 
data. 

The District’s strategy in this portion of the watershed is to rely on its past and continuing 
routine maintenance program, that includes sediment removal and erosion control projects, 
and on its major flood protection projects, known as the Upper, Lower, and Downtown 
Guadalupe River Flood Protection Projects. The Lower project construction (from the 1-880 
bridge north to the Union Pacific Railroad bridge in Alviso), completed in 2004, is estimated to 
have removed over 400 kg of mercury from the Guadalupe River. The construction of the 
bypass in the Downtown project (from Grant Street north to Hedding Street) will result, by 
design, in a 20% reduction of sediment load (and, mercury load associated with that 
sediment) to the Bay. These accomplishments, plus continued maintenance of the Lower 
project to remove accumulated sediment is anticipated to achieve the average annual load 
reduction of mercury to the Bay specified in the Bay TMDL, at least for the initial 10-year 
period. Additional potential control measures that will be evaluated include periodic removal 
of sediment from the bypass, and the use of Pond A8 to capture sediment transported under 
flood flow conditions. 

Incorporating mercury reduction measures into the Upper project (from Highway 280 north to 
the Southern Pacific Railroad crossing downstream of the Willow Street Bridge) and following 
completion of its construction (currently estimated at 2020) will further reduce the sediment 
and mercury load to the Bay. The current project design includes a bypass similar to the 
Downtown project. If this becomes part of the final design, periodic removal of sediment from 
the bypass will be evaluated as an additional means of reducing loading of mercury to the 
Bay. The maintenance program for the main stem of the River will be modified to prioritize 
erosion control projects using an additional criterion of mercury content. The annual 
identification of sites will include an assessment of mercury content. The existing criteria for 
prioritizing projects are protection of property and restoration of flood carrying capacity. 
Adding this criterion will inform the decision of which projects to undertake in a given year, all 
other criteria being equal. 

Guadalupe Creek 

The District completed the Guadalupe Creek Restoration Project in 2001. This project 
resulted in the restoration and revegetation of nearly 7000 linear feet of the creek between 
Almaden Expressway and Camden Avenue. Nearly 36,000 cubic yards of material containing 
over 400 kg of mercury was removed during construction. However, sediment production in 
this watershed continues to deposit sediment at the mouth of this creek. In 2002, 720 cubic 
yards containing 18 kg of mercury was removed, and in 2004, 500 cubic yards containing 13 

22 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


kg of mercury was removed. Until upstream sources (primarily under private ownership) are 
identified and addressed, the District will continue to conduct this periodic removal of 
sediment. Portions of the upper reaches of Guadalupe Creek flow thorough areas where 
mine spoils (untreated waste soil and rock with elevated mercury concentrations) are eroding. 
Sampling results illuminate that tributaries draining mining areas are a continuing significant 
source of mercury load in high-flow conditions. Loads could be reduced beneficially if the 
mine owners would undertake restoration actions similar to those completed by the District 

Alamitos Creek, Deep Gulch, Golf Creek, Randol Creek, McAbee Creek 

The District has ownership and/or easement over Alamitos Creek from Lake Almaden to Harry 
Road (approximately four miles). Above Harry Road to Almaden Dam (approximately six 
miles), the creek is in private ownership and the District has no easements. Deep Gulch is 
wholly within Almaden Quicksilver County Park (Park). The District has ownership and/or 
easement of Randol Creek and McAbee from their confluence with Alamitos Creek to the 
boundary of the park. The District has easement over Golf Creek from its confluence with 
Alamitos Creek to Golden Oak Way. Between Golden Oak Way and the park boundary, Golf 
Creek was converted to a municipal storm drain owned and operated by the City of San Jose. 

Significant and numerous deposits of mercury are present in Alamitos Creek. Mine waste and 
debris comprise the bed and banks of much of the creek, with deposition events evident as 
visible strata on undercut banks (Figure 8). In 2003 and 2004, using grant funding from EPA, 
the District removed nearly 170 kg of mercury by restoring flood capacity, restoring vegetation, 
and reducing erosion potential at two sites on Alamitos Creek; Figures 9 and 10 show one of 
the sites before and after project construction. 

All of the creeks listed above have some portion of their watercourse flowing thorough areas 
where mine spoils (untreated waste soil and rock with elevated mercury concentrations) are 
eroding. Sampling results illuminate that tributaries draining mining areas are a continuing 
significant source of mercury load in high-flow conditions. Loads could be reduced 
beneficially if the mine owners would undertake restoration actions similar to those completed 
by the District. 

The District strategy is to identify and implement similar restoration projects along Alamitos 
Creek as part of its routine maintenance program. Generally, the projects serve multiple 
objectives of property protection, improving flood carrying capacity, restoration, and mitigation. 
In addition, the District will work with the property owners and regulatory agencies to develop 
a strategy for conducting projects in the privately owned portion of the creek. 

Randol Creek and McAbee Creek are highly urbanized waterways that have extensively 
armored banks and are largely void of riparian vegetation. The portions of the creeks under 
District ownership/easement primarily act as conduits for the transport of sediments generated 
by erosion in the upper parts of the creeks inside the park boundaries. Occasionally, the 
District removes sediment from these creeks, but most is transported into Alamitos Creek. In 
2002, the District removed 80 cubic yards of sediment containing 0.2 kg of mercury from 
Randol Creek. The strategy for these creeks is to work with the County to identify and 
evaluate erosion control options for these creeks. 


23 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



24 











Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 8 Example of stratum of mine waste on undercut bank (Alamitos Creek) 



Figure 9 Mercury removal project before construction (Alamitos Creek) 


25 






Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 10 Mercury removal project after construction (Alamitos Creek) 


Lake Almaden and Alamitos Drop Structure 

These two facilities are owned and operated conjunctively by the District to provide 
recreational opportunities, groundwater recharge, and channel stabilization. The drop 
structure was installed to check channel erosion of the main stem of the Guadalupe River. 
The District annually installs a flashboard dam on the drop structure to enhance groundwater 
recharge. 

The study indicates that Lake Almaden and the drop structure serve an important function of 
trapping the bed loads of mercury-containing sediment from Alamitos Creek and Guadalupe 
Creek, respectively (see Figures 11 through 14). The mercury content of this sediment is 
approximately 20 mg/kg, and the sediment represents a significant load of mercury that has 
been prevented from moving downstream to Guadalupe River and the Bay. The accumulation 
of sediment behind the drop structure is substantial, and the study indicates that this sediment 
is being mobilized during wet season flows and carried downstream. The study also indicates 
that the buildup of sediment in Lake Almaden, and possibly behind the drop structure, is 
creating conditions that promote methyl mercury production. 

The District will evaluate the addition of sediment removal projects behind the drop structure 
and at the inlet to Lake Almaden into its stream maintenance program within the next few 
years. The frequency and duration of additional removal events is dependent on the 
implementation and effectiveness of control measures to reduce mercury sources upstream. 
In addition, control measures to reduce methyl mercury production in Lake Almaden and 
behind the drop structure will be evaluated and implemented. The most promising of these, 
aeration of Lake Almaden, will be pilot tested within the next few years. The long-term 
strategy is to develop and implement a restoration plan for this entire area to provide better 
habitat, improve fish passage, and enhance recreational opportunities. 


26 



Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 11 Recent Photograph of Alamitos Drop 

Structure (A) and Lake Almaden (B) Area 


27 















Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 12 Sediment deposition behind Alamitos Drop Structure 


28 






Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 13 Sediment deposition areas in Lake Almaden 


29 





Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 



Figure 14 1976 Photograph of confluence of Alamitos and Guadalupe Creeks, 
showing the same areas outlined in Figures 19 and 20 


30 




Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


Almaden and Guadalupe Reservoirs 

Control measures for these two reservoirs include reduction of mercury entering the reservoirs 
and identifying and evaluating measures to reduce methyl mercury production in the 
reservoirs. The ultimate long-term solution for the reservoirs is to reduce the input of new 
mercury as much as possible as soon as possible, and allow natural burial to occur within the 
reservoirs. Management of the reservoirs to reduce the production of methyl mercury is 
essential to restoration of the beneficial uses in the shortest possible time. The District will 
also explore the potential of retiring one or both of these reservoirs as part of a multi-objective 
approach to restoration of the upper watershed of the Guadalupe River. 

The study demonstrated that methyl mercury production in the reservoirs is strongly correlated 
with depletion of oxygen in the hypolimnion during the warm dry season. Addition of oxygen 
to the hypolimnion of reservoirs is a developing industry that has been successfully 
implemented in water bodies the size of holding ponds to reservoirs with capacities of 
hundreds of thousands of acre-feet. The benefits of aerating reservoirs extend beyond the 
potential for reducing methyl mercury production, such as improving water quality and habitat 
in the reservoir and downstream. 

The District’s strategy for the reservoirs includes: 

• Implementation of a stream restoration project on Jacques Gulch to reduce the input 
of mining waste into Almaden Reservoir. Jacques Gulch is the only source of mining 
waste to Almaden Reservoir. This project is scheduled for completion in 2011. 

• Working with the County to identify and evaluate erosion control options for mining 
waste sources into Guadalupe Reservoir. 

• Conducting a feasibility study of aeration for these two reservoirs and pilot test 
aeration in one of the reservoirs by 2007. If successful, implement aeration in all 
three reservoirs by 2011. 

• Conduct a reconnaissance level evaluation of the potential for retirement of one or 
both of these two reservoirs. 

Calero Reservoir 

Control measures for this reservoir includes reduction of mercury entering the reservoirs and 
identifying and evaluating measures to reduce methyl mercury production in the reservoirs. 

The District’s strategy for this reservoir includes: 

• Identifying and evaluating erosion control options for mercury-containing sediment 
entering the Alamitos-Calero Canal that is used to transfer water from Almaden 
Reservoir to Calero Reservoir. 

• Inclusion of this reservoir in the feasibility study of aeration mentioned above. 


31 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


The recommended District strategy was developed to incorporate and integrate mercury 
issues into existing programs and projects to the maximum extent practicable. Mass removal 
of mercury is integrated into the existing stream maintenance program for those creeks over 
which the District has ownership/easement, and evaluating aeration of reservoirs is integrated 
into existing reservoir operations. Separate projects include evaluating aeration to reduce 
methyl mercury production in Lake Almaden and behind Alamitos Drop Structure, restoration 
of Jacques Gulch, and working with the County and private landowners on the creeks to 
evaluate erosion control options. This strategy addresses the Cleaner, Greener, Leaner goals 
of the District: 

• Cleaner: 

o Improved water quality for fisheries in the reservoirs and downstream creeks 

• Greener: 

o Restored and enhanced environment in the reservoirs and downstream creeks 
o Improved fish habitat and related food cycle and wildlife habitat in the 
reservoirs and downstream creeks 
o Improved recreational opportunities 

• Leaner: 

o Utilization of existing projects and other proposed multi-objective projects and 
activities to simultaneously address stream stewardship, flood protection, and 
water supply interests 

o Proactive action to minimize regulatory administrative burden 


32 


Executive Summary Report: Guadalupe Watershed Mercury Study 


January 20, 2005 


APPENDIX A 

Major Focus Areas for TMDL Implementation 


A-1 



Santa Clara County 


Location 


Stream Restoration (2001} 
Maintenance^; g* ^ 


Almaden Lake 

- Sediment Trapping/Removal 

- New Maintenance Program 

- Stream Restoration (?) 


^iaSonrr- 

Reservoir 


Guadalupe Creek (private) 
-Stream Restoration? 
^Maintenance? 


Alamitos Creek 


Santa Tere >a 
Treatment F ant 


Maintenance 


Stream Restoratii 


uuauaiuuc ncoci vun 

L extngwn 

} ■ es -. Treatment (Oxygenation)? 

- Operations? 

- Dam Removal 


yjdlmadeti 

[^jhesen'oii 


Los Capitancillos Creek 
(SCCPR) 

-Stream Restoration? 


Jacques Gulch 
-Stream Restorati 


Alamitos 

(private^) 



Legend 

A 

SCVWD Streamflow Station 

A 

USGS Streamflow Station 

— 

Canals 

r 

Water Treatment Plant 

T 

Pump Station 


Raw Water Turnout 


Levees 

# 

Historical Mercury Mines 

Instream Dams 


Historical Use/Permitted 


Historical Use/Retired Permit 

Water Distribution Systems 


Raw Water Pipeline 


Treated Water Pipeline 

Generalized Geology 


Babin Intel 101 (Confined Zone) 


Bed look Island 


Santa Clara County Uplands 


Unconfined Zone 


uadalupe 
atershed 


Existing Project/Prog ram 

Project/Prog ram Needed 


Project/Program Needed on 
Property Owned by Others 


Pond A8: 

g ^^Sediment Trapping 


Lower Guadalupe 
Sediment Removal 


/ -Capital Project (2003-04) 
\ -Maintenance 


Downtown Guadalupe 
Sediment Load Reduction 


SFEI 

Monitorin 

Station 


Bypass (2003-04) 
Maintenance 


DowntowrhGuadalupe 
Sediment Locicl Reduction 


Capital Project (202 
Maintenance 


Alamitos Drop Structure 
- Sediment trapping/Removal 


-.New Maintenance Program 

- 


Calero Reservoir 

-Treatment 

(Oxygenation)? 

-Canal Project 

-Operations? 


Almaden Reservoir 

\ -< • 

-Treatment 

(Oxygenation)? 

-Outlet Works Proie 


-Stre^ im Restoration? 
-Maintenance? 


-Outlet Works Proj 
-Operations? 

-Dam Removal? 


Santa Clara Valley Water District ( 

5760 ALMADEN EXPRESSWAY 
SAN JOSE, CA 96118 3686