......... .

Copper Sources in 

Urban Runoff and 

Shoreline Activities

Information Update

Prepared for the Clean Estuary 

Partnership

November 2004

tdc

environmental
PREFACE

This is a report of research performed by TDC Environmental, LLC for the Clean Estuary 

Partnership. Views or information expressed in this report may not necessarily reflect 

those of the funding agencies. Because of the uncertainties inherent in research work, 

TDC Environmental, LLC does not make any warranty, expressed or implied, nor 

assume any legal liability or responsibility for any third party's use of the results or the 

consequences of use of any information, product, or process described in this report. 

Mention of trade names or commercial products, organizations, or suppliers does not 

constitute endorsement or recommendation for use.

ACKNOWLEDGEMENTS

The author greatly appreciates technical assistance provided by Ruby Pap, Bay 

Conservation and Development Commission; Joan Edwards and Karen McDowell, San 

Francisco Estuary Project; the Brake Pad Partnership Steering Committee and project 

team (Rodger Dabish, Pat Thesier, Tim Merkel, Christopher Shepley, Mark Phipps, Jim 

Pendergast, Michael Endicott, Mark Schlautman, and Sarah Connick); Thomas Barron; 

Nan Singhasemanon, California Department of Pesticide Regulation; Leigh Johnson, 

University of California Cooperative Extension; Brandt Grotte; Geoff Siemering, San 

Francisco Estuary Institute; Geoff Brosseau, Bay Area Stormwater Management 

Agencies Association; Arleen Feng, Alameda Countywide Clean Water Program; and 

Richard Looker, San Francisco Bay Regional Water Quality Control Board. 

Much of the scientific literature used in this report is from the Brake Pad Partnership 

Technical Reference Library, a special collection in the U.S. EPA Region 9 library.

Funding for development of this literature collection was provided by the U.S. 

Environmental Protection Agency, the San Francisco Estuary Project, and the Bay Area 

Stormwater Management Agencies Association.

REPORT PREPARER

TDC Environmental, LLC Project Manager: Kelly D. Moran, Ph.D.

4020 Bayview Avenue

San Mateo CA 94403

www.tdcenvironmental.com
i November 2004

COPPER SOURCES IN URBAN RUNOFF

AND SHORELINE ACTIVITIES

TABLE OF CONTENTS

Page

Executive Summary..........................................................................................................1

1.0 Introduction .................................................................................................................4

1.1 Background........................................................................................................4

1.2 Scope of This Report.........................................................................................4

1.3 Report Organization...........................................................................................5

1.4 Uncertainty.........................................................................................................5

2.0 Previous Copper Source Identification Studies..........................................................6

2.1 Copper Uses......................................................................................................6

2.2 Lower South San Francisco Bay Copper Source Studies................................6

2.3 Other Copper Source Studies ...........................................................................7

2.4 Lower South San Francisco Bay Copper Control Measures............................9

3.0 Review of Copper Sources and Control Measures..................................................13

3.1 Copper Sources Selected for Evaluation ........................................................13

3.2 Marine Antifouling Coatings.............................................................................13

3.3 Vehicle Brake Pads .........................................................................................20

3.4 Architectural Copper........................................................................................26

3.5 Copper Pesticides............................................................................................30

3.6 Industrial Copper Use......................................................................................40

3.7 Copper Air Emissions......................................................................................42

3.8 Soil Erosion......................................................................................................46

3.9 Copper in Domestic Water Discharged to Storm Drains ................................49

3.10 Vehicle Fluid Leaks and Dumping...................................................................51

3.11 Sources Not Evaluated....................................................................................53

4.0 Conclusions and Recommendations........................................................................56

4.1 Conclusions .....................................................................................................56

4.2 Recommendations...........................................................................................57

5.0 References ...............................................................................................................59

Appendices

A. Lower South San Francisco Bay Copper Action Plan Actions ................................65

B. Pesticide Calculations ..............................................................................................71

Tables

S-1. Summary of Copper Sources in Urban Runoff .......................................................2

S-2 Summary of Shoreline Copper Sources..................................................................2
ii November 2004

Tables (Continued) Page

S-3. Summary of Feasible Control Measures (Other than Public Outreach) and 

Priorities for Investigation for Copper Sources in Urban Runoff and Shoreline 

Activities...................................................................................................................3

1. Copper Sources Listed by the South Bay Copper Reduction Dialogue .................7

2. Copper Sources Summary from Metals Control Measure Plan .............................8

3. Copper Sources in Stormwater Entering Henriksdal Treatment Plant ...................8

4. Copper “Sources” in Maryland Urban Stormwater..................................................9

5. Estimated Copper Release Rates from Environmental Copper Sources...............9

6. Lower South Bay Copper Action Plan Baseline Actions.......................................10

7. Copper Action Plan Investigation and Implementation Actions and Copper 

Sources Addressed...............................................................................................12

8. Potentially Significant San Francisco Bay Area Urban Runoff and Shoreline 

Activity Copper Sources ........................................................................................13

9. Copper Use in Brake Pads on the 20 Best Selling Domestic Light Duty 

Vehicles, Model Years 1998-2002 ........................................................................22

10. Copper Roof Area Estimate...................................................................................28

11. Architectural Copper Release Estimate................................................................29

12. Copper-Containing Pesticides Active Ingredients and their Urban Uses.............32

13. Bay Area Copper-Containing Pesticide Use Estimate, 2002................................34

14. Bay Area Copper-Containing Landscaping Pesticide Use Estimate, 2002..........35

15. Bay Area Copper-Containing Algaecide Use Estimate, 2002 ..............................37

16. Motor Vehicle Fluid Improper Discharge Estimates..............................................52

17. Summary of Copper Sources in Urban Runoff .....................................................56

18 Summary of Shoreline Copper Sources................................................................56

19. Copper Load Estimates for San Francisco Bay....................................................57

20. Summary of Feasible Control Measures (Other than Public Outreach) and 

Priorities for Investigation for Copper Sources in Urban Runoff and Shoreline 

Activities.................................................................................................................58

A-1. Copper Action Plan Baseline (Table 4-1) Actions.................................................66

A-2. Copper Action Plan Phase I (Table 4-2) Action ....................................................69

A-3. Copper Action Plan Phase II (Table 4-3) Actions .................................................70

B-1. Bay Area Copper-Containing Pesticide Use Estimate, 2002................................72
Copper Sources in Urban Runoff and Shoreline Activities

1 November 2004

COPPER SOURCES IN URBAN RUNOFF

AND SHORELINE ACTIVITIES

EXECUTIVE SUMMARY

The purpose of this report is to summarize information on the sources of copper that is 

carried to San Francisco Bay in urban runoff and copper that is released directly into the 

Bay from shoreline activities. This report:

• Provides estimates of the amount of copper released to San Francisco Bay from 

each source;

• Estimates the relative degree of uncertainty in each copper release estimate and 

lists the sources of uncertainty for each estimate;

• Reviews available control measures for each copper source, providing control 

measure effectiveness information to the extent data are available;

• Identifies feasible control measures for copper sources in urban runoff and 

shoreline activities; and

• Identifies priorities for investigation of sources and control measures.

This report was prepared for the Clean Estuary Partnership to support Technical 

Task 4.11, Basin Planning Assistance for Cu/Ni North of the Dumbarton Bridge. 

Tables S-1 and S-2 (on the next page) summarize urban runoff and shoreline activity 

copper source load estimates and the uncertainties in these estimates. Although the 

total of the urban runoff estimates (45,000 – 47,000 pounds per year) is somewhat less 

than the total estimated copper discharge in urban runoff (90,000 pounds per year), the 

report concludes that it is unlikely that a major copper source has not have been 

identified. Given the long history of investigation of copper sources in the Bay area, it is 

more likely that one or more of the copper load estimates understates actual copper 

releases. 

Table S-3 (on page 3) summarizes the feasible control measures and priorities for 

investigation for each identified copper source.
Copper Sources in Urban Runoff and Shoreline Activities

2 November 2004

Table S-1. Summary of Copper Sources in Urban Runoff

(Pounds of Copper per Year Discharged to San Francisco Bay)

Copper Source Load Estimate Uncertaintya

Vehicle brake pads

Estimate includes:

Original equipment pads

Replacement brake pads

Brake pads on heavy-duty trucks, off-road 

 vehicles, rail cars, and motorcycles

>10,000

10,000

?

?

High

Architectural copper 4,500 Moderate-High

Copper pesticides

Estimate includes:

Landscaping

Wood preservatives

Pool, spa, and fountain algaecides

<8,000 – <10,000

1,200 to 2,500

1,400 to 2,800

<5,000

High

Industrial copper use 3,300 Moderate

Deposition of copper air emissions

Estimate includes:

Diesel and gasoline fuel combustion

Industrial facilities

Residential wood burning and forest fires

Unknown

8,800b

3 – 60

130

110

>8,000

Low to Moderate

Soil erosion

Estimate includes:

Construction

Hydromodification

7,000

2,600

<5,000

Moderate

Copper in domestic water discharged to storm 

drains

3,000 Moderate-High

Vehicle fluid leaks and dumping 600 Moderate-High

aUncertainty is defined as follows: Low indicates that the estimate has an error within 50%; Moderate

indicates that the estimate has an error up to 2 fold; Moderate-high indicates that the estimate has an error 

up to 5 fold; High indicates an error up to 10 fold (see Section 1.4).

bMay overlap with vehicle brake pad estimate.

Source: Section 3.

Table S-2. Summary of Shoreline Copper Sources

(Pounds of Copper per Year Released to San Francisco Bay)

Copper Source Load Estimate Uncertainty

Marine antifouling coatings 20,000 Moderate-High

Copper algaecides applied surface waters 4,000 High

Source: Section 3.
Copper Sources in Urban Runoff and Shoreline Activities

3 November 2004

Table S-3. Summary of Feasible Control Measures (Other than Public Outreach) and Priorities for Investigation 

for Copper Sources in Urban Runoff and Shoreline Activities

Copper Source Feasible Control Measures Priorities for Investigation

Vehicle brake pads • Brake Pad Partnership (BPP) • Improved load estimate (BPP)

Architectural copper • Requirements for management of wastewater from 

cleaning and treatment

• After completing the recommended investigation, consider 

limiting installation and/or requiring measures to prevent 

copper releases or to treat roof runoff

• Practicality and efficacy of control measures 

such as coatings and runoff treatment 

measures

Copper pesticides • Consider developing best management practices for wood 

preservatives to minimize copper use where releases are 

most likely

• Regulatory control measures for pool, spa, and fountain 

algaecides are feasible; use improved load estimate to 

determine if they are warranted

• Improved estimate of the copper load from 

algaecides (primarily pool, spa, and fountain 

algaecides); use estimate to determine 

whether regulatory measures are warranted

• Evaluate alternative practices and pesticides 

for landscaping to determine if safe and 

effective alternatives exist

Industrial copper use • Industrial stormwater permit program None

Copper air emissions • Not able to identify appropriate measures at this time

• Additional controls on identified sources are not warranted

• Identify major air emissions sources

• Determine overlap with brake pad wear 

debris (BPP studies will provide data)

Soil erosion • Construction stormwater permit program

• Hydromodification management plan requirement

None

Copper in domestic water 

discharged to storm drains

• None (other than public outreach) None

Vehicle fluid leaks and 

dumping

• None necessary (other than public outreach) None

Marine antifouling coatings • Not able to identify appropriate measures at this time

• Consider a non-toxic antifouling coatings pilot project 

• Bay Area-specific load estimate

• Participate in IACC Copper Antifouling Paint 

Sub-Workgroup investigation of copper 

problem and control measures

Copper algaecides applied to 

surface waters

• Aquatic pesticides permit program None

Source: Section 3.
Copper Sources in Urban Runoff and Shoreline Activities

4 November 2004

1.0 INTRODUCTION

1.1 Background

Copper has been a pollutant of concern in San Francisco Bay since the late 1980s. The 

1989 designation of lower South San Francisco Bay as impaired by copper (listing under 

section 304(l) of the Clean Water Act) caused government agencies and businesses to 

make a significant investment in copper source identification and copper reduction 

measures. These activities created a wealth of information on copper releases to 

surface waters—and greatly expanded understanding of options to prevent or reduce 

copper releases to San Francisco Bay.

The most recent compilation of copper sources in urban runoff is in the lower South Bay 

Copper Action Plan (Tetra Tech et al., 2000). The Copper Action Plan’s copper source 

list was based on copper source information from the mid-1990s such as the Metals 

Control Measure Plan (SCVURP, 1997), which in turn was based on a list of sources 

assembled in the South Bay Copper Reduction Dialogue (SBCRD, 1994).

Since the mid-1990s, activities in the San Francisco Bay Area (Bay Area) and scientific 

research from elsewhere have provided new information relevant to understanding 

copper sources and control measures. The purpose of this report is to update 

information on copper sources in Bay Area urban runoff. This report also explores 

shoreline copper sources that are not present in lower South San Francisco Bay, but 

that occur elsewhere in the Bay Area. 

1.2 Scope of This Report

This report has been prepared for the Clean Estuary Partnership to support Technical 

Task 4.11, Basin Planning Assistance for Cu/Ni North of the Dumbarton Bridge. The 

report was originally intended to provide up to date information about copper sources in 

urban runoff to facilitate development of a prioritized list of potential urban runoff copper 

source control measures that would provide the greatest relative removals per effort 

expended. However, during the course of the review it became apparent that shoreline 

activities represent a potentially significant source of copper to San Francisco Bay that 

were not considered in previous evaluations of Bay copper sources. Therefore, the 

report was expanded to include shoreline copper sources, even though such sources 

are not components of urban runoff. This information will be used in any San Francisco 

Bay Basin Plan amendments that follow out of the impairment assessment. Because 

one of the necessary elements of a Basin Plan amendment package is a source analysis

(which should be as quantitative as possible), this report provides quantitative load 

estimates to the extent possible with available information.

The focus of this report is copper sources in urban runoff to San Francisco Bay. Two 

types of non-runoff Bay shore copper releases not previously investigated are also 

included—marine antifouling paint and copper algaecides applied to shoreline lagoons. 

This report does not address discharges into or effluent from industrial or municipal 

wastewater treatment plants, nor does it address non-urban copper sources, like 

sediment erosion from open space, agricultural pesticide use, mine drainage, and 

reservoir releases. 

The information in this report was assembled from available data sources. Only existing 

information was used; sampling and chemical analysis were not conducted. 
Copper Sources in Urban Runoff and Shoreline Activities

5 November 2004

1.3 Report Organization

Section 2 summarizes previous copper source identification studies and reviews the 

urban runoff copper control measures from the lower South Bay Copper Action Plan. 

Section 3 identifies the major copper sources, estimates the relative magnitude of each

source and identifies the relative degree of uncertainty associated with these estimates, 

and reviews copper control measures, providing control measure effectiveness 

information to the extent it is available. Section 4 lists conclusions and 

recommendations and identifies priorities for follow-up activities to address critical data 

gaps and uncertainties relating to potentially significant copper sources.

1.4 Uncertainty

Available data do not support reliable quantitative estimates of copper releases from 

most copper sources. The estimates in this report are quite uncertain. While the scope 

of the report does not include a quantitative review of uncertainties underlying each

estimate, the report identifies the sources of uncertainty and uses qualitative review of 

the uncertainties to categorize the level of uncertainty in each estimate according to the 

following definitions (Tsai et al., 2001): 

• Low uncertainty indicates that the estimate has an error within 50%;

• Moderate uncertainty indicates that the estimate has an error up to 2 fold;

• Moderate-high uncertainty indicates that the estimate has an error up to 5 fold;

• High uncertainty indicates an error up to 10 fold.

In each section, possible methods to reduce the uncertainty in the estimates are 

identified. In light of the potential magnitude of the copper sources, quality of the data 

underlying each estimate and the existing control measures for each source, the report 

recommends priorities for future investigations to improve the quality of the copper load 

estimates.
Copper Sources in Urban Runoff and Shoreline Activities

6 November 2004

2.0 PREVIOUS COPPER SOURCE IDENTIFICATION STUDIES

2.1 Copper Uses

Most copper that is refined in the U.S. is used in copper wire and rod, products that have 

limited potential to release copper to surface waters. Other uses of copper and its 

compounds are highly varied, as shown in these examples compiled from the Copper 

Development Association and International Copper Association (CDA, 2002; CDA, 

2003a: ICA, 2004):

• Plumbing pipe

• Heat exchangers, radiators

• Industrial catalysts and electrodes

• Jewelry and other decorations

• Utensils such as pots and pans

• Coins

• Fertilizer

• Firework ingredient

• Coating in cathode ray tubes

• Animal feed additive

• Dietary supplement

• Roofs, gutters, flashing, and other architectural elements

• Motor vehicle components like bearings, bushings, gears, and wiring

• Pesticide (algaecide, fungicide, wood preservative, bactericide)

• Batteries (as an electrolyte or contaminant; an ingredient in alkaline batteries)

• Blue coloring for consumer products

• Semiconductor manufacture

This report focuses on applications of copper metal, copper compounds, and copper 

alloys (e.g., brass and bronze) that may be sources of copper releases to surface water. 

2.2 Lower South San Francisco Bay Copper Source Studies

For more than a decade, San Francisco Bay Area wastewater treatment plants and 

urban runoff management programs have investigated the many uses of copper to 

identify potentially significant sources of copper releases to surface waters. The 1992 

Santa Clara Valley Nonpoint Source Pollution Control Program Source Identification and 

Control Report was the region’s first compilation of copper source information—and its 

first comprehensive plan to reduce copper levels in urban runoff (SCVNPSPCP, 1992). 

The South Bay Copper Reduction Dialogue assembled a comprehensive compilation of 

copper sources, which is summarized in Table 1 (South Bay Copper Reduction 

Dialogue, 1994). Additional investigation has identified that many of the listed copper 

“sources” actually conveyed copper from one or more uses of copper into San Francisco 

Bay. Table 1 (on the next page) identifies which of the listed “sources” convey copper 

from elsewhere and lists the primary copper sources.

In 1997, the Santa Clara Valley Urban Runoff Pollution Prevention Program was the first 

stormwater program in the Bay Area—and probably the first in the nation—to attempt to 

quantify the specific sources of copper in urban runoff. Since 1997, the report 

documenting this effort—the Metals Control Measure Plan—has provided the only 

available basis for prioritizing efforts to manage copper in urban runoff in the Bay Area

(SCVURP, 1997). Table 2 (on page 8) presents the copper sources summary from the 

Metals Control Measure Plan.
Copper Sources in Urban Runoff and Shoreline Activities

7 November 2004

Table 1. Copper Sources Listed by the South Bay Copper Reduction Dialogue

Copper “Source” Primary Copper Source

Air deposition Conveys copper from many sources

Automobile dismantlers (runoff) Vehicle parts

Brake pads Brake pads

Commercial and residential land uses 

(runoff)

Conveys copper from many sources

Construction activities—copper in sand 

blasting slag and copper surface finishes

Copper in waste materials used for 

sandblasting, copper architectural 

materials

Copper algaecides (swimming pools, spas, 

fountains, and ornamental pools)

Copper algaecides

Copper algaecides in water supply systems 

and reservoirs

Copper algaecides

Copper fungicides and herbicides Copper-containing pesticides

Copper in imported water supply Copper in source water, copper 

algaecides

Erosion of native soils Soil

Gas Stations Brake pads, other vehicle sources

Highway runoff Conveys copper from many sources

Illicit connections Copper in wastewater (conveys copper 

from many sources)

Industrial land use Conveys copper from many sources

Landfills Conveys copper from many sources 

disposed in solid waste

Open space Soil

Parking lots and maintenance yards (runoff) Conveys copper from many sources

Spills and illegal dumping (copper 

contamination in motor oil, coppercontaining pesticides)

Many copper sources

Street runoff Conveys copper from many sources

Tap water Copper pipes, copper in source water, 

copper algaecides

Vehicle Fuels (Exhaust) Vehicle fuels

Wastewater treatment plants Copper in wastewater (conveys copper 

from many sources)

Source: South Bay Copper Reduction Dialogue, 1994 and analysis by TDC Environmental.

2.3 Other Copper Source Studies

A literature review identified three studies estimating contributions of various copper 

uses to copper levels in urban runoff. The findings of each study are briefly summarized 

below.

2.3.1 Stockholm

A Swedish study investigated sources of metals in runoff and sewage in a portion of 

Stockholm, Sweden (Sorme and Lagerkvist, 2002). The urban runoff contributions from 

copper roofs, brake pads, tires, and asphalt were estimated. Other sources were 
Copper Sources in Urban Runoff and Shoreline Activities

8 November 2004

Table 2. Copper Sources Summary from Metals Control Measure Plan

Copper Source

Estimated 

Load at 

Source (lbs/yr)

Adjusted 

Load to Bay 

(lbs/yr)a

% of 

Total 

Load to 

Bay

Point Sources (Wastewater Treatment 

Plants)

2,461 2,461 28

Nonpoint Load Estimate for Lower 

South San Francisco Bay

6,400 6,400 72

Urban Nonpoint 9,611 4,685 53

Brake Pads 7,700 3,753 42

Coolant Leaks 112 55 1

Coolant Illegal Dumping 116 57

Oil Illegal Dumping 7 3 0

Industrial runoff 693 338 4

Tailpipe Emissions 116 57 1

Construction Erosion 93 45 1

Pesticide Applicationb74 36 0

Water Supply/Corrosion 700 341 4

Other Nonpoint 

(Natural Erosion and Reservoir Spills)

3,519 1,715 19

Total 8,861 100

aNonpoint Source estimates were adjusted to be consistent with the nonpoint load estimated on the basis of 

creek monitoring data. 

bAgricultural and landscape maintenance applications only. Although the original table attributed this load to 

both fertilizers and pesticides, the calculations not appear to address copper from fertilizers.

Source: Metals Control Measure Plan (SCVURP, 1997).

assumed to be negligible, an assumption validated by the acceptable mass balance 

(sources estimated as 109-113% of measured load). Table 3 presents the load 

estimates. It should be noted that copper roofs are relatively common in Stockholm—

study authors estimated a total copper roof area of 623,000 square meters in an area 

with a population of 630,100. 

Table 3. Copper Sources in Stormwater Entering 

Henriksdal Treatment Plant, 1999

Copper Source Estimated Copper Load

(kg/yr)

Copper roofs 700-920

Brake pads 280

Tires 0.2

Asphalt 11-17

Total (Stormwater Only) 991-1217

Source: Sorme and Lagerkvist, 2002
Copper Sources in Urban Runoff and Shoreline Activities

9 November 2004

2.3.2 Maryland

A University of Maryland group explored sources of copper in urban residential and 

commercial runoff (Davis et al., 2001). While this study confused “sources” and 

conveyances of copper and makes some unverified assumptions, it nevertheless sheds 

light on the presence of copper in urban environments. The study involved washing 

various urban surfaces and measuring the amount of metal washed off. This technique 

cannot separate copper from the “source” and copper conveyed to the sources from 

elsewhere (e.g., from air deposition). The exterior surfaces examined did not contain 

copper so they are unlikely to be the primary source of the measured copper (copper 

roofs were not examined). The study also assumes that the material collected on 

vehicle wheels is entirely (and exclusively) brake pad wear debris, rather than a mixture 

of debris from road and vehicle sources. Table 4 summarizes study results.

Table 4. Copper “Sources” in Maryland Urban Stormwater

Copper Source Estimated Contribution to 

Residential Stormwater

Estimated Contribution to 

Commercial Stormwater

Roofs (non-copper) 9-10% 75%

Material washed from 

building siding

9-22% 7%

Brake pads 47-55% 15%

Tires 1% 0%

Oil 0% 0%

Wet deposition 7-8% 1%

Dry deposition 14-17% 2%

Source: Davis et al., 2001.

2.3.3 Copper Development Association

The industry association for copper manufacturers has compiled information about 

environmental copper releases into a report (CDA, 2003b). This report some of the 

relevant literature on copper releases and provides estimates of release rates from 

certain sources. These release rate estimates are summarized in Table 5. 

Table 5. Estimated Copper Release Rates from Environmental Copper Sources

Copper Source Estimated Copper Release Rate

(g/m2 material per year)

Copper roofs 0.5 – 3.0

Copper gutters 3.5 (old gutters)

7.8 (new gutters)

Composite roof shingles with copper mildewcide 0.17 

Copper-based marine antifouling paint 0.7 – 10 x 1013 (all boats)

6 – 8 x 1013 (well-maintained boats)

Source: CDA, 2003b.

2.4 Lower South San Francisco Bay Copper Control Measures

The lower South Bay Copper Action Plan lays out measures to control copper in 

wastewater and stormwater (Tetra Tech et al., 2000). These measures are divided into 

three phases: Baseline actions and Phase I and Phase II contingency plans. This 

section considers only the implemented (baseline) activities. Table 6 reproduces the list

of Copper Action Plan Baseline actions. Appendix A contains lists of Baseline, Phase I 

and Phase II actions and the copper source addressed by each action. 
Copper Sources in Urban Runoff and Shoreline Activities

10 November 2004

Table 6. Lower South Bay Copper Action Plan Baseline Actions*

Action Description

B-1 Vehicle washing consistency in level of implementation

B-2 Continue to track copper sulfate use by water suppliers (includes State & 

Federal water project)

B-3 Complete Industrial-2: investigations (based on MCMP), identify and 

implement reasonable controls in conjunction with industry (older printed circuit 

board manufacturers with copper plating) to reduce elevated levels in runoff 

from targeted industry including development/implementation of education and 

outreach plan

Clarify linkage with POTW Pretreatment program

B-4 1-Provide appropriate level of local support for agreed upon quantification 

studies to:

2-Investigate and/or track quantification studies for a wide range of existing 

copper control/pollution prevention measures and sources loadings (update 

copper pie charts contained in MCM based on data from B-6 and B-16)

3-Collect data and prepare annual reports on the following potential indicators

Copper content in new auto brake pads

• Total population in basin

• Auto/truck vehicle traveled in basin

• Copper sulfate (e.g., algaecide, pesticide, industrials; chemicals) sales in 

basin (aggregate basis-scaled to basin level estimate)

• Copper content in macoma tissue at Sand Point (Palo Alto

• Reproductivity index for macoma at Sand Point

• Benthic community assemblages at Sand Point

4-Prepare issue paper on feasibility of potential field investigation to monitor 

long-term trends between copper from brake pads and concentration in water

B-5 Provide appropriate level of local support for agreed upon BPP activities 

consistent with MCM

1-Review/assess/provide input on BMC/BPP brake pad wear debris research & 

brake pad content data

2-Ensure that other local state and Federal players are involved appropriately 

on brake pads issue as it is a widespread urban concern

3-Assist in making research data that are in the public domain accessible

B-6 Review appropriateness of transportation control measures, prioritize 

reasonable measures and identify potential efforts for further development as 

part of Phase I and implementation as part of Phase II

B-7 Establish transportation/impervious surface “forum”

• Consider results of VMT and imperviousness load estimates and control 

effectiveness evaluation; identify potential control efforts for further 

development as part of Phase I and implementation as part of Phase II

B-8 Continue to implement watershed classification and assessment efforts of 

SCBWMI and improve institutional arrangements for watershed protection 

(review Vol. II Chapter 5/CCMP/CONCUR findings for relevance and possible 

gaps as part of C-31)

*Transcribed directly from source.
Copper Sources in Urban Runoff and Shoreline Activities

11 November 2004

Table 6. Lower South Bay Copper Action Plan Baseline Actions (continued)

Action Description

B-9 Continue current efforts and track corrosion control opportunities:

• Continue educational outreach, within the City of Palo Alto, to plumbers and 

designers to reduce corrosion of copper pipes via better design and 

installation

• Track developments in (1) alternatives to copper piping (b) corrosion 

inhibitors, and (c) other methods of reducing copper corrosion

B-10 Utilize results of SEIDP indicator #5 (Sediment Characteristics and 

Contamination) to investigate development of an environmental indicator and 

investigate the linkage with SFEI sources and loading work effort

B-11 Consider need for Continuous Improvement of street sweeping controls and 

storm water system operation & maintenance controls (key emphasis is to 

develop SOP for disposal of collected materials)

B-12 Maintain existing education and outreach program for pools and spas

B-13 Track POTW Pretreatment Program efforts and POTW loadings

B-14 Track and encourage water recycling efforts

B-15 Utilize results of SEIDP to evaluate effective ness of related SCVURPPP 

Performance Standards and identify cost-effective modifications

B-16 Establish Information Clearinghouse 

(Track & disseminate new scientific research on copper toxicity, loadings, fate 

and transport, and impairment of aquatic ecosystems for use in CAP update; 

provide stakeholder resource)

B-17 Track and encourage investigation of several important topics that influence 

uncertainty with Lower South Bay Impairment Decision

• Phytoplankton toxicity and movement (IAR Section 5.3.1)

• Sediment cycling

• Loading uncertainty. Encourage incorporation of appropriate 

bioassessment tools into ongoing monitoring programs to track presence of 

copper-sensitive taxa in LSB

Prepare issue paper on feasibility and cost of addressing phytoplankton toxicity 

questions

B-18 Track and encourage investigation of important factors that influence copper 

and fate (potential reduction in uncertainty is moderate to high)

• Investigate flushing time estimates for different wet weather conditions

• Investigate location of northern boundary condition

• Determine Cu-L1 and L2 complex concentrations

• Investigate algal uptake/toxicity with competing metals

B-19 Continue to promote industrial water use and reuse efficiency. These 

programs may include workshops, outreach, incentives, or audits. 

B-20 Revise copper conceptual model report findings and produce status report 

(revise conceptual model uncertainty table, Appendix based on available 

information)

B-21 1-SCVURPPP & Co-permittees evaluate feasibility of discouraging architectural 

use of copper & explore feasibility of related policy

2-Promote Green Building principles and identify measures to investigate as 

part of Phase I

Source: Copper Action Plan Table 4-1 (Tetra Tech et al., 2000).
Copper Sources in Urban Runoff and Shoreline Activities

12 November 2004

The Copper Action Plan included a wide variety of measures, such as studies relevant to 

one or more copper sources, tracking activities of other entities that were addressing 

copper sources, general measures that relate to many copper sources, and 

implementation of control programs for specific copper sources. For purposes of this 

report, those measures involving investigation or implementation of control measures for 

specific copper sources to urban runoff are of interest. These items are listed in Table 7. 

The lower South Bay experience with these actions is reflected in the control measures 

discussions in Section 3 of this report (SCVURPPP, 2004).

Table 7. Copper Action Plan Investigation and Implementation Actions and

Copper Sources Addressed

Action Description Copper Source

B-3 Complete Industrial-2 investigations (based on MCMP), 

identify and implement reasonable controls in conjunction 

with industry (older printed circuit board manufacturers with 

copper plating) to reduce elevated levels in runoff from 

targeted industry including development/implementation of 

education and outreach plan

Industrial 

copper use

B-5 Provide appropriate level of local support for agreed upon 

BPP activities consistent with MCM:

1-Review/assess/provide input on BMC/BPP brake pad 

wear debris research & brake pad content data

2-Ensure that other local state and Federal players are 

involved appropriately on brake pads issue as it is a 

widespread urban concern

3-Assist in making research data that are in the public 

domain accessible

Brake pads

B-6 Review appropriateness of transportation control measures, 

prioritize reasonable measures and identify potential efforts 

for further development as part of Phase I and 

implementation as part of Phase II

Brake pads and 

other vehicle 

sources

B-12 Maintain existing education and outreach program for pools 

and spas

Copper 

algaecides

B-21 1-SCVURPPP & Co-permittees evaluate feasibility of 

discouraging architectural use of copper & explore 

feasibility of related policy

2-Promote Green Building principles and identify measures 

to investigate as part of Phase I

Architectural 

copper

Source: Copper Action Plan Table 4-1 (Tetra Tech et al., 2000).
Copper Sources in Urban Runoff and Shoreline Activities

13 November 2004

3.0 REVIEW OF COPPER SOURCES AND CONTROL MEASURES

3.1 Copper Sources Selected for Evaluation

On the basis of the Metals Control Measure Plan, other urban runoff copper source 

identification studies described in Section 2 and a review of recent literature, nine 

categories of copper sources were found to have the potential to make a significant 

contribution to copper levels in San Francisco Bay Area in urban runoff and in releases 

from shoreline activities. Table 8 lists these copper sources. Each copper source is 

considered in the subsection listed in Table 8. 

Table 8. Potentially Significant San Francisco Bay Area 

Urban Runoff and Shoreline Activity Copper Sources

Copper Source Section

Marine antifouling coatings 3.2

Vehicle brake pads 3.3

Architectural copper 3.4

Copper pesticides (including shoreline algaecides) 3.5

Industrial copper use 3.6

Copper air emissions 3.7

Soil erosion 3.8

Copper in domestic water discharged to storm drains 3.9

Vehicle fluid leaks and dumping 3.10

Source: TDC Environmental.

3.2 Marine Antifouling Coatings

Paints applied to boats and ships to control unwanted “fouling” growth1 on their hulls 

often contain copper-based biocides. Historically, the biocide tributyltin was commonly 

used in marine coatings. Its use on recreational boats was phased out in the late 1980s, 

when U.S. EPA restricted use of tributyltin-based antifoulants to ships longer than 25 

meters. Copper-based biocides—long used on recreational boats—became the primary 

antifouling coating option for recreational boats.

Because of the lack of marinas in the lower South San Francisco Bay,2 marine 

antifouling paint was not evaluated as a copper source in the Metals Control Measure 

Plan. In the Bay north of the Dumbarton Bridge, there are major ports, industrial piers, 

and dozens of marinas. Thousands of boats are berthed in the Bay; recreational boaters 

put thousands of additional boats into the Bay for short-term use. Larger vessels include 

about 2,000 shipping vessels that dock in Bay ports each year (BCDC and MTC, 2003), 

hundreds of commercial ships involved in trade and tourism, and hundreds of 

government-owned vessels to manage aquatic safety and resources. Boats and ships 

coated with copper-containing biocides may release copper directly into the Bay during 

storage, operation, and in-water maintenance. On-shore maintenance activities have 

the potential to release copper into urban runoff.

In the process of developing a Total Maximum Daily Load (TMDL) for the Shelter Island 

Yacht Basin, the San Diego Regional Water Quality Control Board (San Diego RWQCB) 

 

1

 Growth of seaweed, barnacles and other organisms. The presence of such growth on the hull reduces 

boat speeds and increases motor boat fuel consumption.

2

 The one small marina in Alviso indefinitely closed on October 22, 2003 due to encroachment of wetland 

vegetation (Santa Clara County Parks, 2004). 
Copper Sources in Urban Runoff and Shoreline Activities

14 November 2004

has explored the potential importance of copper-based antifouling paint as a source of 

copper in California surface waters. In a draft TMDL report, the San Diego RWQCB

estimated that 98% of the approximately 2,000 pounds of copper released into the Yacht 

Basin each year comes from marine antifouling paints on the 2,400 boats berthed in the 

marina (Dobalian and Arias, 2003). Of the approximately 1.8 pounds of copper 

estimated released per boat per year, about 95% is believed to leach from the paint 

while boats are moored at the dock; the remaining 5% is believed to be released during 

monthly underwater hull cleaning activities. 

The data that forms the basis of these estimates may not directly apply to San Francisco 

Bay. Water body specific factors (such as temperature, pH, salinity, and fouling rates) 

determine both release rates of biocides in antifouling coatings and coating maintenance 

and replacement requirements. The draft Shelter Island Yacht Basin TMDL report 

considered only dissolved copper releases and dissolved copper levels (Dobalian and

Arias, 2003); it did not consider copper releases from marina sediments, which are 

known to contain copper released in particulate form from marine antifouling paint.

San Francisco Estuary Project's (SFEP’s) Boater Education Program has worked with 

boaters and marinas since the early 1990s to develop and implement an education and 

outreach program to protect Bay water quality. The program has focused on marine 

waste management, encouraging boaters to use pump out and dump stations rather 

than discharging directly into San Francisco Bay and the Delta. SFEP is currently 

completing a comprehensive survey of Bay Area marinas that will provide data about 

boat sizes and marina occupancy levels (Patton and McDowell, 2004).

The San Francisco Bay 

Conservation and

Development 

Commission (BCDC) 

completed a pilot San 

Francisco Bay marina 

water quality study to 

explore the water quality 

impacts of marinas. To 

guide the monitoring 

study, BCDC established 

a multi-stakeholder task 

force and a technical 

advisory committee, each 

comprised of federal, state, and local agencies; environmental groups; and marina and 

boating organizations. The study, which includes both a literature review and sediment 

monitoring in four Bay Area marinas,

3 was published in August 2004 (Pap, 2004b). 

BCDC intends to work with the stakeholder task force to develop management strategies 

for any water quality problems identified by the pilot study (Pap, 2004a).

3.2.1 Background

Marine antifouling coatings rely on slow release of a biocide impregnated in the coating 

to prevent fouling growth on the hull. Two formulation types are common:

• Ordinary “hard” copper-containing antifouling paints must be cleaned often enough to 

remove early stages of fouling growth before it becomes established on the boat’s 

 

3

 Copper levels were measured in sediment samples, but not in water column samples.

Pete’s Harbor, Redwood City
Copper Sources in Urban Runoff and Shoreline Activities

15 November 2004

hull. Cleaning frequencies and methods vary by boat owner and location. In Shelter 

Island Yacht Basin, boat hulls are typically cleaned by a diver about once a month. 

• An alternative formulation, known as “ablative” or “soft” paint, wears away as it ages. 

This eliminates the need for cleaning. In San Diego, ablative paint is less common 

than hard paint, apparently because few ablative paint formulations meet applicable

air pollutant emissions requirements (Johnson and Miller, 2002). 

Marine antifouling paints are technically pesticides because they contain biocides. As 

such, antifouling paints are subject to the authorities of the California Department of 

Pesticide Regulation (DPR). DPR maintains public databases containing detailed 

information about pesticide formulations, sales, and use (DPR, 2004a; DPR, 2003a; 

DPR, 2003b). The discussion below is based on these data.

3.2.1.1 Coating Formulations

DPR product registration data show that the following copper-based biocides are used in 

marine antifouling coatings:4

• Cuprous oxide (copper (I) oxide)—The most popular marine antifouling paint biocide, 

cuprous oxide has been formulated by 11 manufacturers into 157 marine antifouling 

coating products that are registered for sale in California. Cuprous oxide 

concentrations in marine antifouling paints range from 26 to 76%; most paints are in 

the 40-70% range. Since cuprous oxide is 89% copper by weight, typical cuprous 

oxide marine antifouling paints are 36 to 62% copper by weight.

• Cuprous thiocyanate (copper thiocyanate)—This unusual marine biocide is 

formulated into 12 marine antifouling paints from one manufacturer. Cuprous 

thiocyanate is 52% copper by weight At concentrations of 9-23% by weight, the 

copper content of these paints is about 5 to 12%. 

• Copper hydroxide—Two cuprous oxide-containing products made by one 

manufacturer also contain copper hydroxide. Both products are 8% copper 

hydroxide by weight. (Since copper hydroxide is 65% copper, this translates into 

about 5% copper from copper hydroxide by weight.) Since this formulation is 

unusual and the copper contribution in these paints is small relative to the copper in 

the same paints from cuprous oxide, its contribution is assumed to be negligible. 

3.2.1.2 Sales

DPR compiles statewide pesticide sales data based on proceeds of DPR’s funding 

source, the “mill tax.” County-specific sales data are not available. Public data are only 

available for pesticides for which more than 3 companies (“registrants”) had registered 

products during the calendar year for which sales are reported. In 2002 (the most recent 

year for which data are available), 1,146,625 pounds of cuprous oxide products were 

sold in California (DPR, 2003a). Because there is only one manufacturer of cuprous 

thiocyanate-containing products, it sales volume is not public.

3.2.1.3 Reported Use

Certain pesticide uses (primarily agricultural and urban applications by licensed pest 

control operators) must be reported to DPR. DPR compiles these reports by October of 

the year following application into reports organized by pesticide and by application site 

 

4

 Two copper naphthenate-containing wood preservatives (neither of which are labeled as antifouling paints) 

are also allowed by the state to be used for marine antifouling applications. While it is possible that these 

products may occasionally be used for boat antifouling coatings, the high solubility of copper naphthenate 

makes this us e impractical.
Copper Sources in Urban Runoff and Shoreline Activities

16 November 2004

(DPR, 2003b). Unfortunately, because marine antifouling coatings are paints, applying 

them to boats is not typically considered to be a pesticide application. For this reason, 

most marine antifouling paint use is not reported to the state.5 In 2002 (the most recent 

year for which data are available), DPR records show that 15,184 pounds of biocides 

were reported applied to boats and piers—almost all of this (15,032 pounds) was copper 

oxide. Two other copper-containing biocides were also reported: 25 pounds of copper 

bronze powder (a marine antifouling paint that is no longer registered) and 52 pounds of 

cuprous thiocyanate.

6

The product registration and use reporting data summarized above suggest that the 

cuprous thiocyanate products are not likely to comprise a significant fraction of the 

copper used in marine antifouling paints. For this reason—and because sales data are 

not available—it is not considered further in this analysis.

3.2.2 Copper Loads

Copper releases from marine antifouling coatings to surface water relate to the amount

of copper applied to boats, the number of boats, the storage locations of those boats, 

boat use frequency, and maintenance practices. 

3.2.2.1 Copper Use in Marine Antifouling Coatings

Almost all copper-containing marine antifouling coatings use cuprous oxide as the 

biocide—and almost all cuprous oxide products are marine antifouling paints. Copper 

use in marine antifouling paint can be estimating by estimating cuprous oxide use. 

Because regional sales data are not available, this analysis starts with a look at 

statewide copper-based antifouling paint use.

Of the 195 cuprous oxide biocides registered in California, 157 registered specifically as 

marine antifouling paints. Most of the remaining products have a broader “wood coating” 

registration, but are sold commercially as marine antifouling paints. Only four of the 195 

products—from 2 manufacturers—have uses other than coating wood, and these other 

uses are almost exclusively agricultural. Since all agricultural pesticide uses must be 

reported, it is reasonable to assume that almost all non-reported use of cuprous oxide 

represents marine antifouling paint applications. In 2002, 214,000 pounds of cuprous 

oxide was reported used for applications other than marine antifouling paint (remaining 

reported use was almost exclusively agricultural, as expected). Assuming that all 

cuprous oxide sold was also used in 2002, non-reported use of cuprous oxide was about 

917,000 pounds. Since there are few non-reportable uses of cuprous oxide other than 

use in marine antifouling paint, this means that as much as 932,000 pounds of cuprous 

oxide (as much as 830,000 pounds of copper) could have been applied to California 

boats in 2002.

3.2.2.2 Boat Population

California Department of Motor Vehicles (DMV) records show that 963,379 marine 

vessels were registered in the state as of December 31, 2003 (DMV, 2004). California 

registration data do not include sailboats less than 8 feet in length or commercial vessels 

larger than 5 net tons or 30 feet. These must be registered (“documented”) by the U.S. 

Coast Guard, which does not have a readily available compilation of registrations by 

water body. California registration data are apparently compiled on the basis of the 

 

5

It should be noted that this treatment of marine antifouling paint is not unusual—other types of paint 

commonly applied by homeowners and professional painters contain biocides (e.g., bathroom paint, deck 

paint); use of these paints is sim ilarly not reported.

6

 About 75 pounds of tributyltin was also applied. Tributyltin may legally be applied to ships longer than 25 

meters.
Copper Sources in Urban Runoff and Shoreline Activities

17 November 2004

owner’s address, rather than the boat storage location. Registrations include boats used 

in California lakes and rivers as well as those used in bays and coastal waters. 

Vessel registration data are broken down by county—in 2003, 176,483 vessels were 

registered in the nine Bay Area counties (Alameda, Contra Costa, Marin, Napa, San 

Francisco, San Mateo, Santa Clara, Solano, Sonoma) (DMV, 2004). Most of these are 

pleasure craft; the remainder (a few hundred vessels) are government and commercial 

boats. About 20,000 are personal water craft (jet skis) (DMV, 2003).7 Other 

breakdowns of boat types (sail boat, motor boat), sizes, and storage location (e.g., inwater or on-shore) are not provided in the registration data summary. These data 

probably include some vessels used only in the ocean or other water bodies that do not 

drain to San Francisco Bay.

3.2.2.3 Antifouling Paint Use

Boats may be stored in the water, or on shore. On-shore storage (“dry storage”) is less 

expensive and requires substantially less maintenance than wet storage, so most boats 

are stored dry, often at one of the region’s many storage yards. Dry-stored boats, which 

only enter the water for short periods, normally are not treated with antifouling paint, 

which is not necessary and may be damaged during travel on a boat trailer. Only wetstored boats typically have antifouling coatings. These boats, perhaps 10 to 15% of 

registered boats, typically are larger and thus more difficult to transport and to move in 

and out of the water than smaller boats.

The San Francisco Bay Area has about 60 yacht harbors, with about 15,000 berths (Bay 

and Delta Yachtsman, 2004). Not all of these berths are occupied; colloquial information 

from industry professionals suggests that about 10,000 to 12,000 boats are berthed in 

San Francisco Bay.

3.2.2.4 Annual Copper Load

Not all of the copper applied to boats has the potential to be released to California 

surface waters. Copper releases from marine antifouling paint may occur several ways.

• Passive leaching and in-water hull cleaning. Because San Francisco Bay marinas

probably have cooler temperatures than San Diego Bay marinas, available copper 

leaching data is likely to overestimate both passive and cleaning-related copper 

releases. Colloquial information from boaters and boat maintenance facilities 

suggests that underwater hull cleaning is not common in San Francisco Bay, and 

frequent only among special groups (i.e., competitive sailors). In the absence of data 

relevant to San Francisco Bay, the release rate estimates from San Diego Bay can 

be used as a starting point to understand the potential magnitude of releases. 

Assuming that the copper release rates estimated for San Diego Bay (about 1.8 

pounds per 12.2 meter boat per year) apply to boats in San Francisco Bay, and that 

boat sizes are similar (averaging 12.2 meters), the 10 to 12,000 boats wet stored in 

San Francisco Bay could release as much as 20,000 pounds of copper per year. It 

is not known what fraction of this copper remains in marinas and what fraction moves 

into the main part of the Bay.

• Boat use. Available studies of copper antifouling paint do not estimate copper 

releases while boats are in motion; however, data suggest that release rates are 

likely to be higher than releases from stationary boats because motion removes 

biofilms that reduce copper releases. In the absence of data, it is assumed that 

 

7

 In 2002, 21,416 of the registered vessels in the 9 Bay Area counties were personal watercraft; 2003 data 

are not available.
Copper Sources in Urban Runoff and Shoreline Activities

18 November 2004

releases from watercraft in motion are the same as in-dock passive leaching rates

and thus included in the above estimate. Because dry-stored boats normally are not 

treated with antifouling paint, their use is assumed not to release copper.

• On-shore maintenance. Boat maintenance—such as on-shore hull cleaning and 

painting—has the potential to release copper to the environment, if the maintenance 

discharges are not controlled. Discharges from boat maintenance facilities in the 

Bay Area are regulated by stormwater management agencies and wastewater 

treatment plants. While some unregulated maintenance activities may occur at 

marinas, for purposes of this report, discharges are assumed to be negligible 

because they should be managed with best management practices and/or directed 

to wastewater treatment plants.

3.2.3 Control Measures

Currently there are no specific control measures in place to limit copper releases from 

marine antifouling paint in the San Francisco Bay Area. In response to concerns raised 

in San Diego, DPR and the State Water Resources Control Board are working together 

to explore the relationship between marine antifouling paints and copper levels in 

surface waters. To facilitate exploration of this issue, the Interagency Coordinating 

Committee (IACC), an existing working group composed of 28 State agencies involved 

in implementing California's Nonpoint Source Pollution Control Program, has created the 

Copper Antifouling Paint Sub-Workgroup of its Marina and Recreational Boating 

Workgroup. The purpose of the subgroup is to assess the degree and geographical 

distribution of copper pollution caused by copper antifouling paints in California’s aquatic 

environments. The subgroup, which held its first meeting in March, has not yet 

established a workplan or schedule. One of the goals of the committee’s work is to 

facilitate the evaluation of control measures by DPR and Regional Water Quality Control 

Boards. 

Alternative marine antifouling coatings. Other marine antifouling coatings exist. In 

recent years, coatings designed to prevent adhesion of fouling growth to boat hulls have 

entered the market. The University of California has evaluated these epoxy and silicone 

coatings (Carson et al., 2002) and has published an education piece for boaters about 

non-toxic antifouling strategies for boats (Johnson and Miller, 2002). To date, non-toxic 

alternatives have not been widely accepted in the boating industry, due to concerns 

about practicality and cost. If adopted, these alternatives would eliminate copper loads 

from marine antifouling paint.

Hull cleaning best management practices. Although modifying underwater hull cleaning 

practices to minimize copper release is possible, data from San Diego suggest that even 

with relatively frequently underwater cleanings, modified procedures are likely have little 

impact on copper loads (Schiff et al., 2003; Carson et al., 2002).

Prohibiting use of copper antifouling coatings. To date, no California agency has 

prohibited use of copper marine antifouling coatings. A San Diego RWQCB proposal 

that would effectively phase out their use in Shelter Island Yacht Harbor has met with 

stiff resistance (San Diego RWQCB, 2003). DPR has the authority to restrict their use, 

but has determined that further investigation of the need for restrictions through the 

IACC Copper Antifouling Paint Sub-Workgroup should be completed prior to 

consideration of possible restrictions (which would need to be based on data identifying 

the contribution of copper marine antifouling paints to surface water quality impairment).
Copper Sources in Urban Runoff and Shoreline Activities

19 November 2004

3.2.4 Uncertainty

Due to the lack of San Francisco Bay-specific information (such as the specific number 

and types of marine craft moored in the Bay, which marine antifouling paints are most 

common, copper release rates in Bay water, hull cleaning frequencies, and recoating 

frequencies) this estimate has moderate-high uncertainty. Sources of uncertainty in the 

current estimate include (but are not limited to):

• Marine craft information. Information about the number and sizes of boats, 

commercial ships, and government vessels wet-stored in San Francisco Bay is 

needed. Data needs include boat and ship numbers, typical sizes, cleaning 

frequency, common antifouling paint types, length of time in Bay waters, and 

recoating frequency. 

• Marina information. Most copper releases from antifouling paints probably occur into 

water and sediments in marinas. Both the Regional Water Quality Control Board and 

BCDC have marina sediment copper data. While the BCDC data shows copper 

enrichment, the Water Board data do not (it is not clear whether this data represents 

the active layer) (Pap, 2004b; RWQCB, 2004b). The extent to which this copper is 

transferred to the water column and sediments in the Bay is unknown.

• No total copper measurements. Studies prepared for the Shelter Island Yacht 

Harbor TMDL evaluated release of dissolved copper. Total copper releases were 

not measured. These studies note that paint particles are released upon hull 

cleaning. These paint particles, which probably contain copper (since such a high 

fraction of copper-based antifouling paint is copper), are assumed to deposit into 

marina sediments and become stabilized in a manner that prevents future 

contribution to dissolved copper levels. San Francisco Bay research has 

demonstrated that fluxes from copper bound in Bay sediments contribute to 

dissolved copper levels in the water column (URS and Tetra Tech, 1998).

• Local environmental different than San Diego Bay. The release rates of biocides in 

antifouling coatings are influenced by temperature, pH, salinity, and fouling rates; 

these factors may be water body specific.

• Boat usage increases copper release rates. The above copper release 

measurements were necessarily made in static conditions. Increased copper 

release rates have been measured from coatings after periods of motion (Valkirs et 

al., 2003). The increased copper release was attributed to the motion-induced loss 

of the biofilm that forms on antifouling paints (Valkirs et al., 2003). 

• Paint types unknown. Ablative paints may have somewhat higher copper release 

rates than hard paints, but received little attention in the San Diego studies because 

colloquial information suggested that they are little used due to region-specific air 

pollutant compliance requirements. 

• Other biocides. Contribution of biocides other than cuprous oxide are omitted (e.g., 

cuprous thiocyanate).

• Applications to materials other than boats. No available data suggests that copperbased antifouling paint is commonly applied to marine structures other than boats 

and ships; however, most marine antifouling paints are registered for use on other 

structures.
Copper Sources in Urban Runoff and Shoreline Activities

20 November 2004

3.2.5 Next Steps

• Load Estimate. Given the potential magnitude of copper releases from marine 

antifouling paint, a region-specific investigation of the copper load and related issues 

is a priority. An estimate would most efficiently be prepared in coordination with the 

two entities currently working with Bay Area marinas (SFEP and BCDC) and with the 

IACC Copper Antifouling Paint Sub-Workgroup.

• Control Measures. The IACC Copper Antifouling Paint Sub-Workgroup plans to 

facilitate evaluation of control measures, assuming its investigations identify the need 

to reduce copper releases from marine antifouling paint. Among the possible control 

measures that could arise from the subgroup are potentially costly measures like 

education programs and cost-effective measures like state agency restrictions on 

copper antifouling paint use.

8

 Given the lack of acceptance of non-toxic alternatives 

to copper antifouling paint, a non-toxic antifouling coatings pilot project would be an 

appropriate precursor to future control programs. 

3.3 Vehicle Brake Pads

San Francisco Bay Area drivers use their brakes millions of times a day, each time 

releasing small amounts of brake wear debris to the environment. In 1993, the Santa 

Clara Valley Nonpoint Source Pollution Control Program retained Woodward-Clyde to 

investigate the potential that vehicle brake wear debris contained water pollutants. The 

resulting report (Woodward-Clyde, 1994a)

identified vehicle brake pads as a potentially 

significant source of copper in urban runoff, 

sparking Santa Clara Valley water quality 

agencies’ interest in vehicle brake pads, 

and eventually leading to the formation of a 

partnership with the brake pad industry and 

other interested stakeholders to explore the 

issue. 

The Metals Control Measure Plan relied on 

the 1994 Woodward-Clyde report to 

estimate the copper load from vehicle brake 

pads. Substantial errors in these 

estimates, which were identified through 

the Brake Pad Partnership, are probably 

part of the reason that the copper load estimate in the Metals Control Measure Plan was 

about double the measured copper release from urban runoff into lower South San 

Francisco Bay.9

The Brake Pad Partnership is currently conducting investigations that will lead to a 

reliable estimate of the contribution of vehicle brake pads to copper levels in San 

Francisco Bay. The approach of the Brake Pad Partnership is to characterize brake 

wear debris and to conduct environmental transport and fate modeling to predict how 

copper released from brake pads enters the Bay and affects both the short-term and 

long-term concentrations of copper in the Bay. Results of these studies, which involve 

air, watershed, and Bay modeling, are anticipated in 2006.

 

8

 In considering such restrictions, DPR usually relies on other agencies to develop region-specific data 

identifying the contribution of the pesticide to surface water quality impairment.

9

 Estimated copper loads from urban runoff and other non-point sources were divided by a factor of 2 to 

match creek copper load estimates.

Behind the wheel: vehicle disc

brake pads and rotor
Copper Sources in Urban Runoff and Shoreline Activities

21 November 2004

3.3.1 Background

Currently, the Bay Area Air Quality Management District (BAAQMD) estimates that 

vehicles drive an average of 167.2 million miles per day in the San Francisco Bay Area 

(BAAQMD, 2004). More than 5 million vehicles are registered to Bay Area residents and 

businesses (MTC, 2004a). All of these vehicles rely on the friction between their brake 

pads (“brake linings”) and a rotor or drum to stop. 

While drum brakes are still common, most new vehicles have disc brakes that are open 

to the environment. With a disc brake, each vehicle stop wears off a tiny amount of the 

brake pad material (“friction material”), which may be deposited on the road, on the 

vehicle, or elsewhere in the urban area. 

Vehicle brake pads are manufactured by automobile parts companies that supply vehicle 

manufacturers—not by vehicle manufacturers themselves. Brake pad manufacturers 

use a wide variety of ingredients—including copper—in formulating brake pads. 

Manufacturers consider formulations, customer identity, and pad sales data to be trade 

secrets. Since brake pad composition is not regulated by any government agency, there 

is no independent central data source for information about vehicle brake pads.

3.3.2 Copper Loads

Estimating copper releases from vehicle brake 

pads into urban runoff involves two steps: 

estimating copper releases in the watershed, and 

then estimating the fraction of copper released 

that is washed off in runoff. The Brake Pad 

Partnership is currently exploring both of these 

questions. The estimate in this section is intended 

to serve as a placeholder until such time as the 

Brake Pad Partnership’s cooperative 

investigations are complete.

The discussion in this section is based primarily on preliminary information obtained from 

the Brake Pad Partnership.

10 The estimate of copper releases to Bay Area watersheds 

involves use of the best available data and assumptions that the Brake Pad Partnership 

believes are as accurate as currently possible given the available data. Because the 

Brake Pad Partnership has not yet addressed the potential for wash-off of copper in 

vehicle brake wear debris, the estimate of the fraction of copper that is washed off in 

urban runoff does not involve input from the Brake Pad Partnership; it is based on 

preliminary results of U.S. EPA modeling of copper runoff in Castro Valley. 

3.3.2.1 Copper Release to Bay Area Watersheds

The annual copper release from vehicle brake pads can be represented by the following 

equation:

Cu Release = Nvehicles x %wear x Cuvehicle

Where: 

Cu Release—Annual quantity of copper released (Lb Cu/yr)

Nvehicles—Number of vehicles

%wear—Percent of brake pad (friction material) worn off each year

Cuvehicle—Average brake pad copper content per vehicle (Lb Cu/vehicle)

 

10 Please note that this discussion represents the analysis of the report preparer; it does not represent the 

views of the Brake Pad Partnership.

Disc brake pads
Copper Sources in Urban Runoff and Shoreline Activities

22 November 2004

Ideally, this equation would be used to calculate the total annual copper contribution 

from vehicles driven in the San Francisco Bay Area. Unfortunately, since the copper 

content of vehicle brake pads is considered proprietary by manufacturers, the data to 

perform vehicle-specific calculations are not available. Limited aggregate data are 

available; these can be used with the above equation to generate a preliminary 

aggregate estimate of copper releases, as described below.

Copper content per vehicle. The best available data on brake pad copper content is 

from the Brake Pad Partnership. As part of the Brake Pad Partnership, U.S. brake pad

manufacturers have developed a procedure for reporting on the amount of copper used 

in brake pads on new vehicles each year. Reporting began in 1998; data are currently 

available through vehicle model year 2002 (see Table 9) (Brake Pad Partnership, 2004). 

The annual report provides the average quantity of copper per vehicle for vehicles in the 

reported model year. Although these data are not intended for use in copper load 

calculations, they are the most comprehensive and reliable data available regarding the 

copper content of automotive brake pads. 

Table 9. Copper Use in Brake Pads on the 20 Best Selling 

Domestic Light Duty Vehicles, Model Years 1998-2002

Model Year 1998 1999 2000 2001 2002

Copper per vehicle (kg) 0.0402 0.0517 0.0564 0.0561 0.0766

Copper per vehicle (lb) 0.0886 0.114 0.124 0.124 0.169

Source: Brake Pad Partnership, 2004

These data are for “original equipment” brake pads used in cars and light trucks. 

According to brake pad industry representatives these vehicles are most likely to have 

copper-containing brake pads. The data do not include “aftermarket” (replacement)

brake pads or brake pads used on heavy-duty trucks, rail cars, off-road vehicles, or 

motorcycles.11 Brake manufacturers indicate that the copper content of aftermarket 

brake pads is small, but no public data are available to confirm that statement. 

Colloquial information from brake manufacturers also suggests that copper use in trucks 

and off-road vehicle brake pads is limited and that motorcycle brake pads, while often 

containing copper, are so physically small that they comprise only a small fraction of onroad brake pad material.

The available data provide the basis for an estimate of the amount of copper released 

from “original equipment” brake pads used in cars and light trucks. At this time, it is not 

possible to estimate the contributions from other types of brake pads. 

Annual brake pad wear. Generally, automobile owners replace disc brake pads before 

the pad material has worn off (this is done as preventative maintenance and avoids 

damage to the rotor). Normally, all pads are replaced at once, leaving some pad 

material permanently unused. In early Brake Pad Partnership discussions of wear 

debris calculation methods, manufacturers provided colloquial information that on 

average, about 60% of brake pad material is worn off prior to replacement. This 

assumption has not been verified. 

Since brake pads are not replaced annually, the brake pad material wears off over the 

course of several years. According to brake pad manufacturers, original equipment 

brake pads are replaced, on average, after about 3 years of service. This estimate has 

not been verified, but it is consistent with typical automobile maintenance schedules. 

 

11 Manufacturers of these other friction material types are not currently participating in the Brake Pad 

Partnership.
Copper Sources in Urban Runoff and Shoreline Activities

23 November 2004

The actual lifetime of individual pads is highly variable, and pad lifetime on individual 

vehicles may differ significantly from the estimated three-year average. 

Due to the variability of pad lifetimes, it would be relatively complicated to develop the 

data needed to estimate the portion of brake pad wear that occurs from each vehicle 

with original equipment pads each year. However, since about the same fraction of 

material is worn off of all pads prior to replacement—and a similar mix of new vehicles 

enters the San Francisco Bay region every year, the overall wear rate for original 

equipment brake pads in the San Francisco Bay Area is relatively constant. Assuming 

that vehicle sales and the Bay Area fleet mix are relatively constant, the calculation can 

be simplified with the assumption that the amount of original equipment brake pad wear 

each year is equal to 60% of the amount of brake pad material sold on new vehicles 

each year.

Number of vehicles in use. To account for variation in vehicle sales, three years worth of 

data were averaged (this is consistent with the assumed typical 3-year lifetime of original 

equipment brake pads). In the San Francisco Bay Area, there are 5,432,514 registered 

cars and trucks (MTC, 2004a). While annual vehicle sales data for the San Francisco 

Bay Area are not readily available,12 California DMV data show that 33.63% of noncommercial registered vehicles are less than 3 years old (DMV, 2002), reflecting a

recent average of about 609,000 vehicles sold each year.

Copper release estimate. To account for variation in brake pad copper content, original 

equipment brake pad copper content data for the most recent three model years were 

averaged (0.139 lb/vehicle) (this is consistent with the assumed typical 3-year lifetime of 

original equipment brake pads). Putting this value and the above estimates into the 

equation yields an estimate of about 51,000 pounds of copper released to San Francisco 

Bay Area watersheds annually from wear of original equipment brake pads on 

passenger cars and light duty trucks. This estimate does not include contributions from 

replacement brake pads nor brake pads used on heavy-duty trucks, rail cars, off-road 

vehicles, or motorcycles.

3.3.2.2 Copper Washoff into Urban Runoff

Available information suggests that brake pad wear debris is deposited not only on 

roads, but also is widely dispersed in urban areas. Brake pad wear debris is comprised 

of very small particles (less than 10 microns in diameter), making air emissions a 

significant release method and a likely important transport pathway for brake pad wear 

debris (BMC/PEC, 2001; Garg, 2000; Sanders, 2002). Information from the literature 

shows that elevated copper concentrations appear at soil surfaces within about 20 

meters of roads (Heath et al., 1999; Sutherland and Tolosa, 2001), suggesting that a 

significant amount of brake pad wear debris is deposited near roads. Since most vehicle 

use occurs on roads in urbanized portions of Bay Area watersheds, this analysis 

assumes that most deposition occurs in the urbanized portion of Bay Area watersheds. 

Potential for wash-off. The City of Palo Alto and the Bay Area Stormwater Management 

Agencies Association (BASMAA) funded Clemson University to characterize brake wear 

debris from one brake pad provided by the Brake Manufacturers Council Product 

Environmental Committee (BMC/PEC). Clemson conducted copper leaching tests, 

using standard extraction test methods and some modified methods with 

environmentally relevant reagents to measure the ability of copper in brake pad wear 

debris to leach out in the environment. Test results show that a substantial fraction of 

copper in the tested brake wear debris can be mobilized in the environment

 

12 These data may be purchased for a fee from automotive industry sources.
Copper Sources in Urban Runoff and Shoreline Activities

24 November 2004

(Schlautman, 2002; Schlautman, 2003a; Schlautman, 2003b; Hur et al., 2003; Hur et al.,

in press). The copper solubility in the tested brake wear debris is probably due to the 

high surface area of brake wear debris13 and the chemical form of the copper in the wear 

debris.

If these data from one brake pad are typical of all copper containing brake pads,

14 the 

results would mean that in the long term, most of the copper can probably be mobilized 

from brake wear debris that remains exposed to water flows. This analysis assumes 

that the behavior of copper in vehicle brake wear debris has wash-off behavior similar to 

other anthropogenic urban copper sources.

Preliminary wash-off estimate. No specific estimates of brake pad wear debris copper 

wash-off are currently available. A rough estimate of wash-off can be made from 

preliminary watershed modeling information in combination with simplifying assumptions. 

On behalf of the Brake Pad Partnership, U.S. EPA staff has set up a model of copper 

runoff from the Castro Valley watershed. This preliminary model has not yet been 

incorporated into the Brake Pad Partnership’s investigations. In preliminary runs of this 

model based on currently available data (no data specific to vehicle brake pads), 

between 31 and 48% of anthropogenic copper annually deposited on impervious 

surfaces was estimated to be transported to San Francisco Bay in urban runoff

(Carleton, 2004).

15

 

In the modeled watershed (Castro Valley), the impervious surface area is about 50% of 

the total surface area. Assuming that all vehicle brake wear debris is deposited in 

urbanized portions of Bay Area watersheds and that Castro Valley’s impervious surface 

fraction is typical for the urbanized portion of Bay Area watersheds, this suggest that 15 

to 24% of copper in brake pad wear debris may be transported to San Francisco Bay in 

urban runoff.

3.3.2.3 Annual Copper Load

Combining the two above estimates (about 50,000 pounds per year of copper released 

from original equipment brake pads, of which 15 to 24% may be transported to the Bay 

in urban runoff) yields a copper load estimate of about 7,600 to 12,000 pounds per year 

(or with one significant figure, about 10,000 pounds per year). This estimate is highly 

uncertain (see below).

3.3.3 Control Measures

The Brake Pad Partnership has served as the primary control measure for copper in 

vehicle brake wear debris. Initiated by Santa Clara Valley Urban Runoff Pollution 

Prevention Program members in the mid-1990s, the Brake Pad Partnership is a 

cooperative effort of government regulators, brake pad manufacturers, stormwater 

management agencies, and environmentalists aimed at identifying and preventing 

impacts on surface water quality that may arise from the use of automotive brake pads. 

Together, the partners are investigating the issue of copper from vehicle brake pads in 

urban runoff. The Brake Pad Partnership anticipates completing its investigations in 

2006. As part of their participation in the Partnership, brake pad manufacturers have 

committed to voluntarily introducing reduced copper products within five years if the 

 

13 Clemson’s data show that brake wear debris has a much higher specific surface area (31 m 2

/g) than the 

standard copper-containing minerals tested (< 1.5 m2/g). 

14 In 2004, the Brake Pad Partnership plans to repeat the extractions on a representative sample of brake 

wear debris to answer this question.

15 Because this modeling effort involved matching washoff estimates and creek monitoring data, it accounts 

for copper removal via control measures like street sweeping and runoff treatment systems.
Copper Sources in Urban Runoff and Shoreline Activities

25 November 2004

Brake Pad Partnership determines that copper from brake pads is a significant cause of 

water quality impairment. While the Partnership’s investigations proceed, brake pad 

manufacturers are conducting research to develop low copper or copper-free pad 

formulations that meet safety standards.

Other control measures involve collecting copper after it is released to the environment

or reducing vehicle use. The major options are:

• Street sweeping—collects particles from streets and highways. Municipalities 

already sweep most Bay Area streets. Because street sweepers are relatively 

inefficient in collecting fine particles (Woodward-Clyde Consultants, 1994b; Brown 

and Caldwell, 1997), and wear debris probably deposits on many urban impervious 

surfaces not subject to street sweeping, street sweeping is not a very effective 

control measure for copper in vehicle brake wear debris. Available data are 

insufficient to determine if increasing street sweeping frequencies or adding more 

rural streets to the sweeping program would increase copper removal significantly

(Claytor, undated).

• Treating urban runoff—Runoff treatment devices vary in their ability to remove 

copper from urban runoff, with typical efficiencies in the 40-60% removal range 

(Winer, 2000). Removal efficiencies for dissolved copper are typically lower than 

those for total copper (Winer, 2000). Many devices are designed to remove trash 

and sediments from stormwater in watersheds; these devices are not designed to 

remove very fine particles like brake wear debris. Such devices are not very 

effective at copper removal (Woodward Clyde, 1996).16 Vegetation-based treatment 

methods—like grassy swales—and infiltration methods generally have the highest 

removal efficiency for copper (Winer, 2000). 

Urban runoff agency permits will soon require treatment of runoff from much of new 

urban development in the Bay Area. This requirement will require substantial 

financial investment for installation and maintenance of the treatment facilities. 

Treating runoff from existing development, while theoretically possible, would involve 

an enormous infrastructure investment (much greater than for new development, 

where installation can be paid for by developers)—plus significant annual 

maintenance costs. Treatment facility costs vary greatly—a BASMAA survey listed 

costs from $160 to $122,000 per acre (not including land costs) (Minton, 2003). 

While vegetation based systems are generally at the lower end of the cost range 

(hundreds to thousands of dollars per acre), Bay Area land costs—assuming land is 

even available—would likely make retrofitting such measures on a widespread basis 

cost-prohibitive.

• Reducing vehicle miles traveled. Reducing vehicle use would reduce release of 

vehicle brake wear debris. In response to Federal and California Clean Air Act 

requirements, the California Air Resources Board, the Bay Area Air Quality 

Management District, and Bay Area municipal congestion management and

transportation agencies have worked for the last several decades to reduce vehicle 

use. Due to population increases and land use patterns, these efforts have been 

unsuccessful—the number of vehicle miles traveled in the Bay Area increases each 

year and is anticipated to increase for the foreseeable future (MTC, 2004b). 

 

16 As it flows through watersheds, copper transfers to larger particles, generally after hours of contact time 

(Sansalone and Buchberger, 1997). In typical Bay Area urban watersheds, this transfer occurs in creeks, 

which have flows that are much too high for typical urban runoff treatment devices.
Copper Sources in Urban Runoff and Shoreline Activities

26 November 2004

3.3.4 Uncertainty

Given the many assumptions and omissions in the estimation of the vehicle brake pad 

copper load, this estimate should be treated as highly uncertain. Most of the data gaps 

will be filled by the much more complete and reliable estimate anticipated from the Brake 

Pad Partnership. 

Sources of uncertainty in the current estimate include (but are not limited to):

• Most brake pads are not included in the estimate. Because limited copper use data 

is available for replacement brake pads or brake pads used on heavy-duty trucks, 

off-road vehicles, rail cars, or motorcycles, the copper contribution from these pads 

was not estimated.

• Estimates assume that the behavior of copper in vehicle brake wear debris has 

wash-off behavior similar to other anthropogenic urban copper sources. This 

assumption is based on data from only one copper-containing brake pad. There are 

several different chemical forms of copper used in brake pad formulations. 

• Copper use data are not designed for mass load calculations. The Brake Pad 

Partnership’s copper use reporting program does not document total copper use; 

instead, it assumes that copper usage in disc brake pads for the top 20 models of 

domestically-manufactured light vehicles (accounting for approximately 40% of 

vehicle sales) serves as a valid indicator of the industry’s overall copper use. 

• Vehicle fleet mixes vary. Within a region or watershed, variations in fleet mix and 

vehicle use patterns also contribute to differences in copper content and amounts of 

wear debris released to the environment. 

3.3.5 Next Steps

• Load Estimate. The Brake Pad Partnership is currently conducting investigations 

that will lead to a reliable estimate of the contribution of vehicle brake pads to copper 

levels in San Francisco Bay.

• Control Measures. Continue participation in the Brake Pad Partnership, which 

serves as the primary control measure for copper in vehicle brake wear debris. 

3.4 Architectural Copper

Architects and building occupants enjoy 

the beauty and longevity of copper 

architectural features like roofs, gutters, 

and flashing. Nationally, architectural 

use of copper has increased in recent 

years (CDA, 2003b). Copper roofs and 

gutters cost far more than ordinary 

materials, limiting their use to a 

relatively small number of structures in 

the San Francisco Bay area. 

Perhaps due to the relative rarity of 

copper roofs, the Metals Control 

Measure Plan did not estimate copper 

releases from architectural copper 

features. Since the late 1990s, a series of papers in the literature have revealed 

relatively high concentrations of copper in copper roof and gutter runoff (Barron, 2001; 

Copper roof, Redwood Shores California
Copper Sources in Urban Runoff and Shoreline Activities

27 November 2004

Wallinder and Leygraf, 1997; Zobrist et al., 2000; Wallinder and Leygraf, 2001; 

Leuenberger-Minger et al., 2002). In some studies, copper concentrations in roof runoff 

exceeded 1,000 μg/l (Barron, 2001). Concerned about these findings and an upward 

trend in the use of copper roofs and gutters in new construction, Palo Alto commissioned 

a study to estimate copper releases from copper architectural features (Barron, 2001). 

The Palo Alto study estimated that architectural copper runoff comprises about 20% of 

the copper load in Palo Alto creeks.

3.4.1 Background

While all copper pieces start with a shiny metal appearance, if left untreated, the copper 

will develop a patina, oxidizing to shades of green and brown as it ages. Oxidation 

forms compounds that are soluble in water. Factory or field treatments immediately give 

the copper a desired patina, by oxidizing the surface to create a complete coating of 

oxides. Occasionally, architectural materials may be clear coated to maintain a desired 

hue (typically a penny-colored brown). 

Some composite roofing shingles are treated with copper granules to retard moss and 

mildew growth. Like the copper in pure copper roofs, the copper granules will age, 

become covered with an oxide patina, and be subject to runoff when it rains. 

3.4.2 Copper Loads

3.4.2.1 Copper Release to Bay Area Watersheds

The amount of copper washed off 

architectural copper features is 

proportional to the area of those 

features and the copper release 

rate. Both of these can be 

estimated using information 

compiled by Palo Alto (Barron, 

2001). The major types of 

architectural copper features 

(roofs, gutters, and copper-treated 

composite shingles) are included 

in this estimate; the contribution 

from other materials (flashing, 

ornamentation) is assumed to be 

relatively small.

Presence of copper architectural features. No quantitative data is available about the 

presence of architectural copper or the installation rate of new copper roofs and gutters

(Barron, 2001). The Palo Alto estimate relied on colloquial information obtained from a 

survey of contractors, building departments and similar entities and a visual inspection of 

buildings in Palo Alto to create a very rough estimate that copper roofs are installed on 

0.05% of residences, 0.3% of industrial commercial buildings, and 1.5% of other 

structures. The “other structures” category was region-specific,17 to reflect the relatively 

high frequency of copper use in the institutional structures in that region (Barron, 2004). 

The Palo Alto study estimated that 0.03% of residential roofs use composite roofing 

shingles with copper biocides, and that these shingles had negligible use on structures 

in other land uses. Roof coverage was assumed to be 30% for residential land and 50% 

for other developed land.

 

17 The region includes East Palo Alto, Los Altos, Los Altos Hills, Mountain View, Palo Alto, and Stanford.

Copper roof section, prior to installation
Copper Sources in Urban Runoff and Shoreline Activities

28 November 2004

Using these estimates, the copper roof area can be estimated as follows:

Copper roof areaLU = Acres LU x Roof CoverageLU x Copper Roof FractionLU

Using land use data from the Association of Bay Area Governments (ABAG, 2003) the 

copper roof area in the San Francisco Bay Area is estimated to be about 466 acres and 

the composite shingle with copper biocide roof area is estimated to be about 39 acres 

(see Table 10). 

For copper gutters, the method was very similar (Barron, 2004)—except 0.06% of 

residential buildings were assumed to have copper gutters (to reflect the presence of 

copper gutters on some buildings without copper roofs). The surface area of building 

gutters was assumed to be about 3.25% of the roof surface area. Using these figures, 

the estimated copper gutter area in the San Francisco Bay area is 15.5 acres (2.5 acres 

residential; 13 acres commercial/industrial/institutional).

Table 10. Copper Roof Area Estimate

Land Use

Land 

use 

area

(Acres)

Total 

Roof 

Coverage

Copper 

Roof 

Fraction

Copper 

Roof 

Area

(Acres)

Copper 

Biocide 

Roof 

Fraction

Copper 

Biocide 

Roof 

Area

(Acres)

Residential 428,660 30% 0.05% 64 0.03% 39

Commercial/Industrial/

Institutional

267,630 50% 0.3% 402 -- --

*Local streets and some highways are included within land use estimates (ABAG, 2003).

Source: TDC Environmental calculations based on data from ABAG, 2003 and Barron, 2001.

Copper release rates. Published literature and limited measurements conducted by Palo 

Alto provide the estimates of copper releases from copper architectural features listed in 

Table 11 (on the next page) (Barron, 2004). Note that the copper release rates are 

within the range of the release rate estimates provided by the Copper Development 

Association (see Table 5 on page 9).

3.4.2.2 Copper Washoff into Urban Runoff

Since the copper release rates for architectural copper are based on copper 

concentrations in runoff, no additional adjustment for wash-off fraction is necessary. 

Since discharge configurations vary—and often involve direct discharge to storm 

drains—this analysis assumes that the net copper load is essentially the same as the 

quantity of copper in runoff from architectural copper features. This approach does not 

account for losses of copper between the release point (i.e., downspout) and surface 

waters. While there is a potential for significant reduction in copper levels in roof runoff if 

the runoff flows through vegetation or passes through a treatment device, the variation in 

discharge locations for copper roofs provides no rational basis for assuming a certain 

fraction removal of the copper.

3.4.2.3 Annual Copper Load

Multiplying the architectural copper roof area estimate by the estimated copper release 

rates gives the copper load estimates in Table 11 (on the next page), a total of about 

4,500 pounds per year of copper releases.
Copper Sources in Urban Runoff and Shoreline Activities

29 November 2004

Table 11. Architectural Copper Release Estimate

Architectural Material Estimated Area 

(Acres)

Estimated 

Release Rate 

(g/m2 material

per year)

Estimated Copper 

Release 

(lb Cu/year)

Copper Roofs 466 1 4,200

Composite Roofs with 

Copper Biocide

39 0.17 59

Copper Gutters 15.5 2 280

Total 4,500

Source: TDC Environmental calculations based on data above.

3.4.3 Control Measures

Many control measures to reduce architectural copper releases are possible—measures 

could include public education to reduce copper use, coating copper to reduce releases, 

treating runoff to collect released copper, and restricting copper use. In the San 

Francisco Bay Area, a few municipalities have used education to limit use of copper 

architectural features; one municipality (Palo Alto) has prohibited most architectural 

copper use. 

Public education. Education of architects, planners, and the public has the potential to 

reduce copper use in buildings. SCVURPPP has encouraged South Bay municipalities 

to incorporate avoiding copper architectural features into municipal green building 

programs. Ordinarily, green building programs do not address copper architectural 

features. The general effectiveness of such educational programs is unknown, although 

colloquial information suggests that education can limit copper use.

Treating copper or runoff. In theory, architectural copper features could be coated in a 

manner that would maintain the copper’s appearance, but would prevent release of 

copper to the environment. In practice, the efficacy and maintenance requirements for 

such coatings have not been demonstrated. As described in Section 3.3.3, treatment of 

runoff for copper removal is also possible. Treatment systems have significant technical 

downsides—they require management and maintenance and have incomplete copper 

removal. Costs for treatment would include building owner costs for installation and 

maintenance, and municipal costs to ensure that treatment systems meet performance 

standards.

Collecting copper wastewater. Cleaning and treating copper architectural features 

(particularly patina treatments) involves corrosive solutions that may contain relatively 

high concentrations of copper. These solutions could be collected, tested to determine 

their waste classification, and managed according to accepted best management 

practices for wastewater from building surface cleaning activities (BASMAA, 2000).

Prohibiting architectural copper use. Local governments have the authority to regulate 

the use of building materials. Many attractive alternative roofing materials do not contain 

copper (Barron, 2001). In August 2002, the City of Palo Alto adopted an ordinance 

prohibiting the use of copper for new roofs. Prohibitions include copper metal roofing,

asphalt shingles containing copper granules, and copper gutters. Copper flashing and 

ornaments are exempted. The ordinance, which became effective on January 1, 2003, 

includes provisions to protect historic buildings.
Copper Sources in Urban Runoff and Shoreline Activities

30 November 2004

3.4.4 Uncertainty

The major source of uncertainty in this estimate is the uncertainty in the surface area of 

copper architectural features in the Bay Area. This, combined with the uncertainty in 

copper release rates, suggests a moderate-high uncertainty for this estimate. Sources 

of uncertainty in the current estimate include (but are not limited to):

• Surface area. Estimates of the area of copper architectural features are based on 

colloquial information and are highly uncertain. No method to improve the estimates 

has been identified, though field surveys or photographic analysis may be practical 

for small watersheds.

• Release rates. Copper release rate estimates relate to weather conditions, air 

quality, distance from salt water and other region-specific factors. This analysis 

assumes that the copper release rate selected on the basis of the literature is 

representative of San Francisco Bay Area release rates. 

• Patina treatments and cleaning solutions. Load from runoff of field treatments to 

create a patina and cleaning solutions is not estimated. Since field treatments 

involve corrosive solutions, spent treatment solution and rinsate could have elevated 

copper levels. While construction stormwater regulations should prevent discharge 

of such solutions, improper discharges of such solutions could comprise a 

meaningful copper load.

• Copper removal from runoff. Some fraction of the copper released from architectural 

features may be removed from runoff if the discharge flows over landscaping or 

across other materials to which copper may bind. Depending on the drainage 

configuration, copper removal from runoff from some architectural copper features 

may be significant.

3.4.5 Next Steps

• Load Estimate. Although the load estimate is uncertain, the cost involved in 

preparing a more accurate load estimate—particularly the cost to inventory copper 

roofs in the entire region—is probably not justified. Community-specific load 

estimates may be necessary to support local decisions regarding restrictions on use 

of architectural copper features.

• Control Measures. Measures to control runoff from cleaning and treatments (e.g., 

patina treatments) of copper architectural features should be considered. Questions 

remain regarding the practicality and efficacy of measures to prevent copper 

releases (e.g., coatings) or to treat roof runoff. If such measures are practical and 

sufficiently reduce copper discharges, they offer a technically more complicated—but 

perhaps politically less difficult alternative to prohibiting architectural copper use 

(which is technically feasible). Architectural copper use limitations are feasible; 

these could be structured to allow installation with appropriate treatment measures, if 

such measures are found to be practical and effective. 

3.5 Copper Pesticides

Since the inception of copper control programs in the San Francisco Bay area, 

municipalities have sought to reduce use of copper-based pesticides. Pesticide use may 

release copper to urban runoff, to Bay area shorelines, to Bay area surface waters, or to 

wastewater treatment plants.
Copper Sources in Urban Runoff and Shoreline Activities

31 November 2004

In response to a request from the Regional Water Quality Control Board in the early 

1990s, some water suppliers have limited their use of copper-based algaecides. 

Wastewater treatment plants worked with the state legislature and the Department of 

Pesticide Regulation (DPR) to secure a 1995

prohibition on the sale and use of copper-based root 

control products in the San Francisco Bay Area (Palo 

Alto, 1999). Many municipalities have conducted 

public outreach efforts to reduce copper algaecide use 

in swimming pools, spas, and fountains.

Copper-based pesticides are among the most 

commonly used pesticides in surface water bodies. In 

response to a 2001 Federal court decision, the State 

Water Resources Control Board (SWRCB) initiated a 

program to regulate applications of pesticides to 

surface waters (SWRCB, 2004a). Concurrently, the 

SWRCB commissioned a study of the environmental 

effects of aquatic pesticide applications. The study, 

conducted by the San Francisco Estuary Institute 

(SFEI) found that dissolved copper from aquatic 

pesticide applications caused lethal and sublethal 

toxicity in juvenile trout for at least 24 hours after 

application, toxicity in ceriodaphnia dubia (water flea) 

for at least a week after application, and may relate to increased sediment copper 

concentrations (though results on sediment toxicity were inconclusive) (Siemering, 

2004).

The presence of the permit requirements has increased incentives for applicators (who 

are primarily public agencies) to reduce use of aquatic pesticides. The SWRCB permit 

has planning, monitoring, and reporting requirements on the use of copper-based 

aquatic pesticides (SWRCB, 2004a), increasing the incentives for applicators to 

transition to alternative pesticides or to non-pesticide control methods for aquatic weeds 

and algae.

While the Metals Control Measure Plan included an estimate of copper releases from 

pesticides, the estimate was based only on use of copper sulfate-containing pesticides 

by professional pest control operators. Recognizing that use of any of the more than a 

dozen copper-containing pesticide active ingredients, for the last several years Palo 

Alto’s annual Copper Action Plan Report has compiled information about all copper 

containing pesticides and their use in Santa Clara Valley (Palo Alto, 2003).

3.5.1 Background

Copper-containing pesticides are widely used to control fungi, mildew, algae, and roots. 

Common applications include controlling fungi on plants; controlling roots and other plant 

growth in sewers; controlling algae in swimming pools, ponds and lakes; controlling 

aquatic plant growth on boat hulls; serving as biocides in commercial products; and 

preventing rot and mildew on wood, roofing, and other outdoor surfaces. 

As of February, 2004, there were 19 copper-containing pesticide active ingredients in 

products registered for sale in California. Primary uses are as algaecides, marine 

antifouling paint biocides, root killers, and wood preservatives, agricultural and garden 

fungicides. Table 12 (on the next page) summarizes the registered copper-containing 

pesticide active ingredients and their urban uses.

Retail pesticide display
Copper Sources in Urban Runoff and Shoreline Activities

32 November 2004

Table 12. Copper-Containing Pesticides Active Ingredients and their Urban Uses

Pesticide Active Ingredient Name

Number of 

products

Algaecide

Marine Paints

Root Killer

Wood 

Preservative

Garden 

Fungicide

Copper 49 X X X

Copper 8-quinolinoleate 8 X

Copper Ammonia Complex 5 X

Copper Ammonium Carbonate 4 X

Copper Carbonate 8 X X

Copper Ethanolamine Complexes, 

Mixed

11 X X

Copper Ethylenediamine Complex 1 X

Copper Hydroxide 45 X X

Copper Naphthenate 27 X

Copper Oxide (Cuprous) 212 X

Cupric Oxide 12 X

Copper Oxychloride 13 X

Copper Oxychloride Sulfate 6

Copper Resinate 3

Copper Soap (Copper Octanoate) 4 X

Copper Sulfate (Basic) 25 X

Copper Sulfate (Pentahydrate) 61 X X X X

Copper Thiocyanate 16 X

Copper Triethanolamine Complex 8 X

Source: DPR Product database (DPR, 2004a)

3.5.2 Copper Loads

Using DPR data, it is possible to develop a gross estimate of copper containing pesticide 

use in the San Francisco Bay Area. The estimate uses pesticide sales data, reported 

pesticide use data, and a calculation of unreported use as described below. To ensure 

consistent use of pesticide data, DPR provides its reports in units of pounds of pesticide 

“active ingredient” (A.I.). With a simple calculation based on the copper mass fraction of 

each copper-based pesticide, this can be converted to pounds of copper.

Pesticide Sales Data. DPR compiles statewide pesticide sales data based on proceeds 

of DPR’s funding source, the “mill tax.” County-specific sales data are not available. 

Public data are only available for pesticides for which more than three companies 

(“registrants”) had registered products during the calendar year for which sales are 

reported. 
Copper Sources in Urban Runoff and Shoreline Activities

33 November 2004

Reported Pesticide Use. Certain pesticide applications are required to be reported to 

the County Agricultural Commissioner, who, in turn, reports the data to DPR. 18 In 

general, the pesticide uses that require reporting are agricultural uses or urban 

applications done by licensed pest control operator. DPR compiles pesticide use reports 

annually into a document that identifies pesticide application locations by broad 

categories that are sufficiently defined to allow differentiation of urban uses from other 

uses, but not to evaluate the details of urban uses.

Unreported Pesticide Use. Assuming all pesticides sold are used within a particular 

year, unreported pesticide use is (approximately) equal to the difference between 

pesticide sales and reported pesticide use. The primary exceptions to the use reporting 

requirements are urban uses: home and garden use and most industrial and institutional 

uses. (Pesticides used in consumer products are also often unreported.) Additional 

analysis of the uses of particular active ingredients can improve this assumption 

somewhat, but it is a highly uncertain estimate. 

Table 13 (on the next page) presents an estimate of the copper content in coppercontaining pesticides used in the San Francisco Bay Area (see Appendix B for additional 

details). The estimate is based on an estimate of statewide urban use of copper-based 

pesticides, which is a sum of reported urban pesticide use and unreported pesticide use. 

Assuming that urban copper pesticide use per capita is the same in the San Francisco 

Bay Area as it is statewide, the statewide urban copper estimate was adjusted on the 

basis of population to create a Bay Area estimate. 

The next step in the analysis is to evaluate how the copper-containing pesticides are 

used and the potential for each to be released to surface waters. To simplify the 

analysis, the seven pesticides with estimated Bay area use less than10 pounds are not 

considered further. The remaining pesticides are divided into the following groups 

(recognize that some pesticides have multiple uses and therefore fall into multiple 

groups):

• Landscaping fungicides—copper, copper ammonia complex, copper hydroxide, 

copper oxychloride, copper sulfate (basic);

• Wood preservatives—copper, copper carbonate, copper ethanolamine complexes 

(mixed), copper naphthenate, cupric oxide, copper sulfate (pentahydrate);

• Algaecides—copper, copper carbonate, copper ethanolamine complexes (mixed), 

copper ethylenediamine complex, copper sulfate (pentahydrate), copper 

triethanolamine complex (the copper content of potable water discharged to storm 

drains is discussed in Section 3.9);19

Marine antifouling paint (copper oxide [cuprous], copper thiocyanate, and negligible 

quantities of copper hydroxide)—primarily a shoreline copper source, not an urban runoff 

source—is discussed in Section 3.2. Root control products (copper sulfate) are 

assumed not to be used, in compliance with the state prohibition on their sale and use 

(Palo Alto, 1999).

 

18 Pesticide uses for the production of any agricultural commodity, except livestock; for the treatment of postharvest agricultural commodities; for landscape maintenance in parks, golf courses, and cemeteries; for 

roadside and railroad rights -of-way; for poultry and fish production; any application of a restricted material; 

any application of a pesticide designated by DPR has having the potential to pollute ground water when 

used outdoors in industrial and institutional settings; and any application by a licensed pest control operator 

must be reported the County Agricultural Commissioner, who, in turn, reports the data to DPR.

19 The copper content of reservoir releases is not an urban stormwater copper discharge and thus is not 

included in this report.
Copper Sources in Urban Runoff and Shoreline Activities

34 November 2004

Table 13. Bay Area Copper-Containing Pesticide Use Estimate, 2002

Pesticide

2002 

Statewide 

Sales 

(lb A.I.)

2002 

Statewide 

Reported 

Use

(lb A.I.)

Estimated

Statewide 

Urban Use 

(lb A.I.)

Copper in 

Statewide

Estimated 

Use

(lb Cu/yr)

Estimated 

Bay Area 

Copper 

Usea

(lb Cu/yr)

Copper 326,000 45,857 286,805 286,805 56,501

Copper 8-quinolinoleate --

b

10 10 2 0

Copper Ammonia Complex 14,277 5,543 9,697 9,697 1,910

Copper Ammonium 

Carbonate

-- 42 12 4 1

Copper Bronze Powder -- 25 0 0 0

Copper Carbonate 14,274 7,878 6,228 3,550 699

Copper Ethanolamine 

Complexes, Mixed

171,230 17,721 166,318 166,318 32,765

Copper Ethylenediamine 

Complex

-- 2,557 1,456 1,456 287

Copper Hydroxide 3,940,156 2,592,460 1,355,936 881,358 173,628

Copper Naphthenate 380,620 84,476 380,605 38,061 7,498

Copper Oxide (Cupric) -- 127,523 126,210 100,968 19,891

Copper Oxide (Cuprous) 1,146,625 229,214 918,075 817,087 160,966

Copper Oxychloride 84,997 58,934 26,489 15,364 3,027

Copper Oxychloride 

Sulfate

-- 174,700 0 0 0

Copper Resinate -- 18,612 35 3 1

Copper Soap (Copper 

Octanoate)

250 0.007 250 45 9

Copper Sulfate (Basic) 1,455,054 876,722 579,200 306,976 60,474

Copper Sulfate 

(Pentahydrate)

5,646,324 2,916,477 2,649,632 675,656 133,104

Copper Thiocyanate -- 61 9 5 1

Copper Triethanolamine 

Complex

256 2 256 256 50

TOTAL 3,303,610 650,811

a

19.7% of statewide estimate, based on a California’ population of 35,591,000 and a San Francisco Bay 

Area population of 6,994,500 as of January 1, 2003 (DOF, 2003).

b

Data not made public by DPR because there are 3 or fewer registrants.

Source: TDC Environmental calculations with data from DPR (DPR, 2004a; DPR 2003a; DPR, 2003b).

3.5.2.1 Landscaping

Copper Release to Bay Area Watersheds. Most urban uses of copper ammonia 

complex, copper hydroxide, copper oxychloride, and copper sulfate (basic) are as lawn 

and garden fungicides. Although there are other miscellaneous uses (e.g., copper 

hydroxide is incorporated into soil to prevent root growth into structures), this analysis 

assumes that all estimated Bay Area urban use of these products is on urban 

landscaping. Almost all products with copper metal as the active ingredient are 
Copper Sources in Urban Runoff and Shoreline Activities

35 November 2004

algaecides; however, there are 2 professional turf products that use copper metal. Since 

professional pesticide applications should be reported, the outdoor garden use of copper 

metal is assumed to equal to the extrapolated Bay Area fraction of its statewide reported 

landscaping use, 672 pounds. Similarly, use of the one copper sulfate product 

registered for landscape use (which is assumed to be a professional product as it was 

not observed in a recent retail shelf survey) is assumed to equal to the extrapolated Bay 

Area fraction of its statewide reported landscaping use, 6,800 pounds. Using these 

assumptions, Table 14 presents the total San Francisco Bay area use of copper in 

copper-containing landscaping pesticides.

Table 14. Bay Area Copper-Containing Landscaping

Pesticide Use Estimate, 2002

Pesticide

Estimated Bay Area 

Copper Use

(lb Cu/yr)

Copper 672

Copper Ammonia Complex 1,910

Copper Hydroxide 173,628

Copper Oxychloride 3,027

Copper Sulfate (Basic) 60,474

Copper Sulfate (Pentahydrate) 6,800

TOTAL 250,000

Source: Table 13; s ee text.

Copper Washoff into Urban Runoff. Only a small fraction the copper applied to 

landscaping is washed off in storm water runoff, as copper tends to bind to soil and 

vegetation. A study of copper runoff from tomatoes treated with copper fungicides found 

that about 1% of applied copper was washed off of a tomato cultivation study area 

(Dietrich and Gallagher, 2002). This study involved the use of plastic mulch for the 

tomatoes, which is known to increase pesticide wash-off rates (Rice et al., 2001). The 

runoff fraction is consistent with known washoff rates of many other pesticides, which 

are typically less than 0.5% of the amount applied (Wauchope, 1978). 

Annual Copper Load. Assuming the runoff fraction is 0.5 - 1%, the copper release to 

San Francisco Bay Area urban runoff from landscaping pesticide use would be about 

1,200 to 2,500 pounds.

3.5.2.2 Wood Preservatives

Copper Release to Bay Area Watersheds. The primary uses of copper carbonate, 

copper naphthenate, and cupric oxide are for wood treatment. These may be used 

individually or combined with other ingredients to produce well-known wood 

preservatives like chromated copper arsenate (CCA). Most or all of the estimated Bay 

Area use of these three pesticides (about 28,000 pounds of copper) is assumed to be for 

wood protection. While three other pesticides (copper, copper ethanolamine complexes 

[mixed], copper sulfate [pentahydrate]) may be formulated into wood preservative 

products, these are believed to be minor uses of these pesticides based on the relatively 

small number of products.

Copper Washoff into Urban Runoff. Copper is known to leach out of wood treated with 

copper-based wood preservatives. The amount of copper leaching, particularly after the 

first few months, is not well understood (CDA, 2003b). A recent U.S. Geological Survey

(USGS) study of a 580-acre watershed with a 27 acre lake suggests that even in a 
Copper Sources in Urban Runoff and Shoreline Activities

36 November 2004

watershed with relatively extensive use of copper-treated wood, the wood preservatives 

are a relatively minor source of copper releases to surface water (Rice et al., 2002). In 

the USGS study watershed, CCA-treated wood is used for bank stabilization along about 

75% of the lake shoreline. In addition, the watershed contained copper-treated decks 

and docks. Nevertheless, copper leaching from preserved wood was estimated to 

represent only about 4% of the annual copper load in the small watershed; the main 

source (comprising about 90% of the copper) was road runoff. Since copper-treated 

wood use in the San Francisco Bay area is far less dense than in study watershed 

studied by the USGS, it is reasonable to conclude that copper-based wood preservatives 

release only a relatively small amount of copper to San Francisco Bay.

In the USGS study, the authors note that most of the copper in treated wood is removed 

when the wood is removed from service, typically after 10 to 20 years of use. Since they 

estimated that it would take about 180 years to leach all the copper from treated wood 

posts and pilings submerged in water, a conservative assumption would be that about 

8% of copper used to treat wood (15 years divided by 180 years) is released while it is 

used. In the San Francisco Bay area, the main uses of copper wood preservatives are 

not along shorelines, but in fences, decks, and other outdoor landscaping. It is therefore 

reasonable to assume that wood preservative copper releases would be attenuated by 

runoff across soil surfaces in a manner similar to runoff losses of other urban copper 

releases, and therefore that the runoff fraction would be similar to the runoff fraction for 

other copper pesticides used in landscaping (see above). 

Annual Copper Load. To simplify the estimate, it is assumed that all copper that will be 

released from a year’s worth of wood preservative use occurs in the first year—in other 

words, it is assumed that all the copper released from annual sales of 28,000 pounds of 

copper wood preservatives occurs in the year the wood is sold. If the runoff fraction is 

0.5 - 1%, the copper release to San Francisco Bay Area urban runoff from wood 

preservative use would be about 1,400 to 2,800 pounds.

3.5.2.3 Algaecides

Copper Release to Bay Area Watersheds. Most urban uses of copper ethanolamine 

complexes (mixed), copper ethylenediamine complex, and copper triethanolamine 

complex are as algaecides, so this analysis assumes that other uses of these three 

pesticides are negligible. Since most copper carbonate products are wood 

preservatives, algaecide use is assumed to be minor. Separating out algaecide uses of 

copper metal and copper sulfate (pentahydrate) is quite difficult. Of 61 copper sulfate 

(pentahydrate) products, 16 are root control products; 3 are wood treatments; one 

product is for landscaping, 9 are agricultural products; 27 are swimming pool algaecides, 

and the remainder are specialize algaecides (e.g., for aquaria, industrial water). The mix 

of products containing copper metal is similarly confusing. With this mix of products and 

the limitations of available data, it is not possible to estimate quantitatively all algaecide 

uses, though it is likely that use exceeds 50,000 pounds per year. Table 15 (on the next 

page) summarizes available information about San Francisco Bay Area copper 

algaecide use. 
Copper Sources in Urban Runoff and Shoreline Activities

37 November 2004

Table 15. Bay Area Copper-Containing Algaecide Use Estimate, 2002

Pesticide

Estimated Bay 

Area Copper 

Use (lb Cu/yr)

Number of 

Swimming Pool 

Products

Notes

Coppera Unknown

(<55,829)

24 of 49 Unclear what 

fraction is used as 

an algaecide.

Copper Ethanolamine 

Complexes, Mixed

32,765 4 of 11

Copper 

Ethylenediamine 

Complex

287 0

Copper Sulfate 

(Pentahydrate) b

Unknown

(<126,304)

27 of 61 Unclear what 

fraction is used as 

an algaecide

Copper Triethanolamine 

Complex

50 7 of 8

a

Total reduced by 672 pounds to reflect reported use of professional landscaping products.

b

Total reduced by 6,800 pounds to reflect reported use of professional landscaping product.

Source: Table 13 and DPR product information (DPR, 2004a); see text.

Copper Washoff into Urban Runoff. Copper-based algaecides are applied to many 

different types of water, with very different potential to release copper to urban runoff or 

San Francisco Bay. The primary uses are considered below:

• Surface water applications to non-drinking water bodies—While some non-drinking 

water surface waters may be treated with copper algaecides, the majority of such 

treatments in the San Francisco Bay Area are treatments by municipalities made to 

lagoons and sloughs bordering San Francisco Bay (RWQCB, 2004a). Since lagoons 

and sloughs generally release water directly to San Francisco Bay, this analysis 

assumes that all copper applied to non-drinking water bodies is released to the Bay 

and is therefore a shoreline copper source, rather than an urban runoff copper 

source (actual releases are somewhat lower due to copper deposition in the treated 

water body). 

• Reservoirs and water supply conveyance channels—These common applications to 

prevent unpleasant taste and odor from algae growth and to ensure smooth 

operation of potable water systems are part of the copper considered in Section 3.9. 

• Industrial applications—Copper has many industrial algae control applications, often 

in systems that do not regularly discharge to either the sewer or storm drain systems 

(e.g., irrigation ponds, recirculated cooling water). Stormwater discharges from 

industrial facilities are considered in Section 3.6.

• Swimming pools, spas, and fountains—much of the applied copper is collected by a 

pool’s filtering system, or bound to pool, spa, or fountain walls and fixtures, but an 

unknown fraction remains in the water. When emptied (not a common event), pools, 

spas, and fountains may be discharged to sewers or to storm drains (under 

municipal stormwater permits, dechlorinated swimming pool water is an exempted

discharge). No estimate of the fraction discharged to storm drains is available; 

however, based on copper’s efficient binding to solids like pool, spa, and fountain 

surfaces and materials in pool filtration systems, it is reasonable to assume that less 

than 5% of pool, spa, and fountain algaecide copper is discharged to storm drains. 
Copper Sources in Urban Runoff and Shoreline Activities

38 November 2004

Annual Copper Load. Of the above algaecide uses, all must be reported to DPR except 

homeowner applications to swimming pools, spas and fountains. DPR has a database 

tool that allows reported pesticide uses to be obtained for specific California counties. 

This tool was used to obtain reported non-industrial copper-containing pesticide 

applications to surface water bodies in the nine San Francisco Bay Area counties (a 

region larger than the area discharging urban runoff to the Bay) Reported applications

were 3,700 pounds in 2002 (DPR, 2004b). 

This report may not very accurately reflect actual copper algaecide use in Bay Area 

surface waters. Aquatic pesticide application permit records for 2002 (RWQCB, 2004a)

provided numerous examples of copper algaecide applications to surface waters that do 

not appear in the DPR database results, suggesting that the database does not include 

accurately classification of use reports (or possibly that some uses reported to the Water 

Board were not reported to DPR). It should be noted that this report includes 

applications to reservoirs and water supply conveyance channels, which are not 

shoreline copper sources.

Of the remaining application types listed above, copper algaecide use in pools, spas, 

and fountains is most likely to have a potential to release meaningful quantities of copper 

into runoff. A rough estimate of this algaecide use can be made by assuming that the 

swimming pool, spa, and fountain use of copper pesticides with multiple uses is 

proportional to the fraction of products labeled for pool, spa, and fountain applications. 

This assumption gives a rough estimate of <95,000 pounds. Assuming that less than 

5% of this copper is discharged to storm drains, a rough load estimate would be <5,000 

pounds.

3.5.3 Control Measures

Control measures are available for all types of copper pesticide uses. In the San 

Francisco Bay Area, control measures have focused on copper algaecide uses.

Algaecides for pools, spas, and fountains. Currently, the primary control measure to 

prevent copper releases from pools, spas, and fountains to San Francisco Bay is public 

outreach. Outreach discourages uses of copper (copper-free alternatives, such as 

hypochlorite-containing shock treatments, are available), and encourages discharge of 

copper-containing pool, spa, and fountain water to the sewer, not the storm drain. 

SCVURPPP developed model source control measures for pools, spas and fountains. 

These model measures provide (1) that there be no direct discharge of pools to storm 

drains or sanitary sewer manholes; (2) pools should be drained to the sanitary sewer via

a clean-out (with POTW permission); and (3) for new pools, local codes should require 

installing a clean-out in accessible area near the pool. In the lower South San Francisco 

Bay, outreach about copper-containing algaecide use and pool water discharge started 

in the mid-1990s. Outreach programs target both residential pool owners and pool 

maintenance professionals. SCVURPPP has concluded that effectiveness of these

programs cannot be measured at this time (instead, performance evaluation is based on 

the quantity of outreach materials distributed) (SCVURPPP, 2004). 

Other algaecides applied to surface waters. The primary control measure for copperbased pesticide applications to surface waters is the Aquatic Pesticide General Permit

program, managed by the State and Regional Water Quality Control Boards. (Certain 

municipal stormwater permits also include provisions requiring development of 

performance standards for aquatic pesticide applications.) The aquatic pesticide general 

permit requires an Aquatic Pesticides Application Plan describing best management 

practices to mitigate effects to water quality resulting from pesticide application, 

monitoring, and reporting of pesticide applications and monitoring results to the Regional 
Copper Sources in Urban Runoff and Shoreline Activities

39 November 2004

Water Quality Control Board (SWRCB, 2004a). In response to permit requirements, 

copper algaecide use in lagoons and sloughs discharging to San Francisco Bay has 

declined significantly (RWQCB, 2004a).

Alternative algae control methods. In addition to applying registered pesticides, aquatic 

pests can be controlled with biological, physical, and mechanical control methods, nonconventional chemical control methods, and/or preventive measures. Some alternative 

control measures have the potential to impact water quality and aquatic habitats 

adversely, though a study by SFEI showed that many alternatives had lesser impacts 

than aquatic pesticides (Greenfield, 2004). Appropriate alternatives methods need to be 

identified on a site-specific basis, which means that testing is a necessary step in 

transitioning to a non-copper control measure. The relative cost-effectiveness of 

conventional pesticides versus alternative methods varies among different management 

scenarios (Mann and Wittmann, 2003). 

Copper landscaping pesticides. Currently there are few control measures in place

specifically addressing copper-based pesticides used in landscaping. Some municipal 

integrated pest management policies include measures to limit use of copper-based 

pesticides. Little or no public outreach regarding use of copper pesticides has occurred. 

The transition to integrated pest management (IPM) by municipalities and efforts to 

promote IPM to communities are likely to reduce use of copper-based pesticides, but the 

reduction is unknown. Because copper-based landscaping pesticides are often less 

toxic to humans than alternative pesticides, any transition away from copper landscaping 

pesticides needs to be managed with caution. 

Copper wood preservatives. The U.S. EPA phase-out of chromated copper arsenate 

(CCA) has stimulated a transition to other copper-based wood preservatives. Colloquial 

information suggests that the most commonly available alternatives are also copperbased (but do not contain chromium or arsenic), such as copper naphthenate and 

ammoniacal copper quat. Borates are also commonly available, but are intended 

primarily for indoor (dry) applications. Based on an evaluation of wood preservative 

alternatives, San Francisco is considering adoption of a policy to minimize use of copper 

wood preservatives for structures built in or over water or where significant runoff would 

contact the treated wood (Dickey, 2003). Non-wood alternative materials, rather than 

wood treated with a different wood preservative, are likely to be environmentally 

preferable—but some alternative materials have potential adverse environmental effects

(Dickey, 2003). 

Regional copper-based pesticide sales or use restrictions. Another possible option is to 

ask DPR to consider regulating copper-containing pesticides. Given the relative 

magnitude of the potential copper load and the cost of alternative control measures, 

regulation would be most cost-effective for controlling copper-based pool, spa, and 

fountain algaecides. This option has not been explored to date. DPR generally requires 

quantitative information about the water quality and/or permit compliance problems 

associated with a pesticide (including quantification of the pesticide’s relative 

contribution to the problem) before it will consider restricting a pesticide’s sales and use. 

3.5.4 Uncertainty

Given the major data gaps, the estimated release from copper pesticides is highly 

uncertain. Sources of uncertainty in the current estimate include (but are not limited to):

• Sales data. Extrapolation of statewide pesticide sales data to the San Francisco 

Bay Area creates highly uncertain pesticide sales estimates. The lack of sales data 
Copper Sources in Urban Runoff and Shoreline Activities

40 November 2004

for 8 of the 19 copper-containing pesticides on the market only increases the 

uncertainty of the estimates made in this analysis.

• Region-specific factors. Estimates do not account for climate, lot size, regional pest 

problems or other reasons that pesticide use per person might vary across the 

state.

• Simplifying assumptions. The analysis relies on many simplifying assumptions 

(primarily regarding the relative importance of various uses of each coppercontaining pesticide active ingredient), each of which is noted in the text above.

• Washoff rates. Pesticide wash-off rates are based on very limited data.

• Inaccuracies in DPR databases. In general, DPR quality assurance programs 

ensure that DPR databases provide data with low uncertainty; however, review of 

records of surface water applications of copper-containing pesticides identified 

discrepancies between DPR records and reports filed with the Regional Water 

Quality Control Board, suggesting that the database does not include accurately 

classification of use reports (or possibly that some uses reported to the Water 

Board were not reported to DPR).

• Assumptions about pool, spa, and fountain algaecides. The load estimate relies on 

two assumptions that cannot be verified—(1) the assumption that the swimming 

pool, spa, and fountain use of copper pesticides with multiple uses is proportional to 

the fraction of products labeled for pool, spa, and fountain applications and (2) the 

assumption that less than 5% of this copper is discharged to storm drains.

3.4.5 Next Steps

• Load Estimate. Given the potential magnitude of copper releases from algaecides, 

an improved estimate of the copper load from algaecides (primarily pool, spa, and 

fountain algaecides) is a priority. Such a load estimate could determine whether 

voluntary programs are sufficient or regulatory programs (e.g., sale and use 

restrictions and/or more stringent controls on pool, spa, and fountain water 

management) are warranted.

• Control Measures. Evaluate alternative practices and pesticides for landscaping to 

determine if safe and effective alternatives exist. Consider developing best 

management practices for wood preservatives to minimize use of copper wood 

preservatives where releases are most likely to occur. Since the Aquatic Pesticides

General Permit regulates surface water algaecide applications, additional controls 

should not be needed (unless the permit does not continue to create a disincentive 

for copper use). Appropriate control measures for pool, spa, and fountain algaecides 

should be determined on the basis of a better load estimate. 

3.6 Industrial Copper Use

Industry has long been a focus of environmental regulatory programs, including both 

wastewater pretreatment and stormwater permit programs. Any industrial facility in one 

of 10 broad categories of industrial activities must participate in the State Water 

Resources Control Board’s industrial stormwater permit program. About 1,400 industrial

facilities in the San Francisco Bay Area are currently active participants in the program.

The Metals Control Measure Plan used a specialized estimate based on industrial 

stormwater runoff monitoring data compiled from the industrial stormwater permit 

program (Grotte, 1996; SCVURP, 1997). That analysis involved special categorization 

of industry to separate out metal-using industry categories and to focus particularly on 
Copper Sources in Urban Runoff and Shoreline Activities

41 November 2004

three types of companies with relatively high copper levels in their reported monitoring 

data (electroplaters, metals finishers, and semiconductor manufacturers) (Grotte, 1996). 

Subsequently, three Santa Clara Valley studies looked at elements of the Metals Control 

Measure Plan industrial copper load estimate. A detailed analysis of facilities in Palo 

Alto and Mountain View found that the previous estimates were imperfect, but the 

variations in subsequent monitoring data suggested that the imperfections reflect, in 

part, real variation in industrial monitoring data (Cooke and Bodine, 1997). Similarly, two 

subsequent studies of Santa Clara Valley electroplaters, metals finishers, and 

semiconductor manufacturers concluded that results were similar to previous estimates, 

given the inherent variability of the data (SCVURPPP, 1998; SCVURPPP, 2003b).

3.6.1 Background

Although quite a few industrial activities involve use of copper-containing materials, 

many of these activities occur indoors, where most copper releases would not have the 

potential to be released to runoff. Certain processes—like heated plating tanks—could 

potentially release droplets of copper-containing solutions into building air exhaust 

system and out onto building roofs and the surrounding area (SCVURPPP, 1998).20

3.6.2 Copper Loads

The specific analysis conducted for the Metals Control Measure Plan cannot be 

repeated with available information. While a similar analysis of region wide industrial 

stormwater monitoring data would be useful, such a significant effort was not possible 

within this project’s scope and budget.

Since no recent or region-wide analysis of industrial stormwater monitoring data has 

been identified, the estimate used in the Metals Control Measure Plan was assumed to 

be sufficiently representative of current industrial stormwater discharges to be

extrapolated to a Bay-wide estimate. The extrapolation on the basis of the number of 

acres of industrial facilities in the San Francisco Bay Area (89,266), as determined from 

the State Water Resources Control Board Industrial Stormwater Database for the San 

Francisco Bay Area (SWRCB, 2004b). Since previous total industrial acreage was not 

available, the number of acres of industrial facilities in Santa Clara County (18,835) was 

assumed to have remained constant since 1997. The extrapolated copper load is 3,300 

pounds per year.

3.6.3 Control Measures

The primary control measure for industrial runoff is the Industrial Storm Water General 

Permit program, managed by the State and Regional Water Quality Control Boards. The 

industrial stormwater permit requires the implementation of management measures that 

will achieve the performance standards of “best available technology economically 

achievable” and “best conventional pollutant control technology.” Facilities covered by 

the permit must prepare and implement Storm Water Pollution Prevention Plans and 

monitoring plans. The state regulatory program is supplemented by the required 

commercial/industrial element of municipal stormwater programs. 

Individual municipalities have explored a variety of methods to enhance the 

effectiveness of their industrial stormwater programs. For example:

 

20 Copper that is emitted to the air is considered in Section 3.7.
Copper Sources in Urban Runoff and Shoreline Activities

42 November 2004

• Many municipalities combine industrial stormwater inspections with other routine 

inspections of the same facilities (e.g., by wastewater pretreatment programs or 

certified unified program agencies). 

• On the basis of its investigations of copper in industrial runoff, the Santa Clara Valley 

Urban Runoff Pollution Prevention Program initiated a unique pilot outreach 

campaign designed to increase compliance with industrial stormwater permit 

requirements. The effort includes a partnership with industry to increase familiarity 

with practical best management practices to reduce pollutant levels in runoff. The 

effectiveness of this pilot project has not yet been evaluated (SCVURPPP, 2003b).

No data are currently available to estimate the effectiveness of these regulatory and 

education programs in reducing copper discharges.

3.6.4 Uncertainty

Although the estimate involves significant extrapolations, since it was based on actual 

industrial runoff monitoring data, the industrial copper load estimate is moderately

uncertain. Sources of uncertainty in the current estimate include (but are not limited to):

• Monitoring data. The estimate assumes that previous monitoring data is 

representative of current industrial stormwater discharges (regulatory efforts have 

probably reduced the industrial copper load.)

• Extrapolation. The estimate assumes that the previous estimate is representative of 

the industrial contribution to runoff from all industrial facilities.

• Industrial facility area. The estimate assumes that the number of acres of industrial 

facilities in Santa Clara County have remained constant since 1997 (substantial 

growth followed by a substantial economic downturn have occurred since that time.) 

3.6.5 Next Steps

• Load Estimate. Although the load estimate is uncertain, given that the control 

measures are unlikely to change, a more accurate load estimate is not necessary at 

this time. Using industrial stormwater permit data to compare previous and current 

pollutant loads could, however, be generally helpful in understanding the efficacy of 

stormwater permits as a control measure.

• Control Measures. Since the Industrial Storm Water General Permit already 

regulates industrial runoff, additional controls are not needed.

3.7 Copper Air Emissions

Air deposition conveys copper from copper air emissions sources into San Francisco 

Bay and onto surfaces subject to urban runoff. The actual emissions sources of the 

copper deposited onto the Bay and Bay watersheds are not fully known at this time. 

Sources include vehicle fuel combustion, fires, industrial air emissions, vehicle 

components, soils, and industrial air emissions.

The Metals Control Measure Plan estimated copper emissions from motor vehicle fuel 

combustion, but not from other copper air emissions sources. The basis of the Metals 

Control Measure Plan estimates was the California Air Resources Board model 

BURDEN7F. The metals data in this model are not recent—in fact they represented 

emissions from leaded gasoline, which was phased out in 1992. Although the copper 

emissions estimates were not noteworthy, the emissions estimates for several metals 

were high enough to merit follow-up investigation to obtain a more accurate—and 
Copper Sources in Urban Runoff and Shoreline Activities

43 November 2004

region-specific—load estimate. BASMAA coordinated with the California Air Resources 

Board and the University of California Santa Cruz to measure metals concentrations in 

San Francisco Bay Area gasoline and diesel fuel (Brosseau, 2004).

In 2001, the San Francisco Estuary Institute (SFEI) published results of a pilot study to 

measure wet and dry deposition of copper and other metals in the San Francisco Bay 

area (Tsai et al., 2001). The report included an estimate of the quantity of copper 

deposited from the air into Bay Area watersheds and—based on a general estimate of 

the wash-off fraction—the estimated copper load to San Francisco Bay from airdeposited copper. Samples were collected at locations somewhat away from human 

activity with the intent of obtaining a regional background load estimate not influenced by 

specific sources (like roads or industrial facilities). While this report did not identify the 

copper emissions sources, it provided a relatively reliable estimate of the contribution of 

copper deposited from the air to the quantity of copper in urban runoff.

3.7.1 Background

Air emissions may result from ordinary industrial or residential activities, like combustion 

of industrial fuels and firewood containing trace amounts of copper. Although copper 

emissions have not been a focus of air quality agencies, air pollutant emissions from 

industrial facilities and from vehicles are closely regulated by California air quality 

agencies.

In the San Francisco Bay Area, vehicle fuel combustion has proven of interest to water 

quality agencies due to the relatively large volume of fuel used in the Bay Area. Each 

day, almost 9 million gallons of gasoline and more than one million gallons of diesel fuel 

provide the power for San Francisco Bay Area vehicles to travel 167.2 million miles 

(BAAQMD, 2004). Given these fuel volumes, there exists the potential that even trace 

impurities in fuels could result in environmentally meaningful releases of water 

pollutants. Unlike lead, copper is not intentionally added to motor vehicle fuels. Copper 

is an impurity that comes from the crude oil or from equipment in the refining process.

Because fuel transportation is expensive, motor vehicle fuels are typically distributed 

regionally. Most of the San Francisco Bay Area’s supplies come from the region’s own 

oil refineries. The characteristics of fuel in a region are defined by the oil source, and to 

a lesser extent the specific refinery processes used to create the fuel from crude oil.

3.7.2 Copper Loads

3.7.2.1 Copper Release to Bay Area Watersheds

Although some fraction of copper emissions travel outside the Bay Area, because 

deposition patterns are source specific and unknown, all release estimates below 

assume that all emitted copper is deposited in Bay Area watersheds.

Vehicle Fuels. Pre-publication data provided by BASMAA (Brosseau, 2004) was used to 

estimate the copper releases from motor vehicle fuel combustion. Eighteen diesel fuel 

samples and 19 gasoline samples (five premium, one mid-range, 13 regular) were tested 

for copper concentrations. Copper was not detected in most samples; it was detected in 

one diesel and one premium gasoline sample. Assuming that these detects represent 

normal variation in copper concentrations, an average copper concentration range of 0.6 

– 8 parts per billion (ppb) was calculated for the diesel samples (low value assumes nondetected values were 0; high value assumes that non-detected concentrations equaled 

the detection limit). The concentrations were similarly averaged to estimate a copper 

concentration range of 0.7 – 8 ppb for gasoline, assuming that the sample mix was 

adequately representative of the sales fraction of the three gasoline grades. Fuel 
Copper Sources in Urban Runoff and Shoreline Activities

44 November 2004

densities were assumed to be equal to the density of octane (gasoline) and cetane 

(diesel) (Lide, 1998).

Fuel use estimates were obtained as follows:

• Gasoline. BAAQMD estimates 2003 San Francisco Bay Area gasoline use was 8.8 

million gallons per day (BAAQMD, 2004).

• Diesel. Since BAAQMD did not provide a diesel fuel use estimate, diesel use was 

estimated on the basis of statewide fuel use data from the California Department of 

Finance (DOF, 2002b). Assuming the fraction of the state’s diesel used in the San 

Francisco Bay Area is the same as the fraction of the state’s gasoline used in the 

Bay Area (21%), about 1.6 million gallons of diesel are used daily in the San 

Francisco Bay Area.

On the basis of this data, the copper released to Bay Area watersheds is estimated to be 

in the range of 10-200 pounds.

Industrial Air Emissions. The Bay Area Air Quality Management District (BAAQMD) 

prepares an annual inventory of air toxics emissions in the San Francisco Bay Area, 

based on reports from facilities with air pollutant emissions permits (BAAQMD, 2003). 

Although copper emissions are not required to be reported by any facility emitting less 

than 463 pounds per year, 53 industrial facilities reported a total of 410 pounds of copper 

air emissions in 2001 (BAAQMD, 2003). 

Fires. The Copper Development Association (CDA) estimated statewide copper 

releases from residential wood burning and forest fires (CDA, 2003b). Bay Area 

emissions can be roughly estimated on the basis of these statewide estimates. 

• Residential wood burning. CDA estimated annual copper emissions of 1371 pounds

statewide (CDA, 2003b). Assuming wood burning is proportional to population, Bay 

Area emissions would be 19.7% of statewide emissions (based on a California

population of 35,591,000 and a San Francisco Bay Area population of 6,994,500 as 

of January 1, 2003 [DOF, 2003]), or 270 pounds. 

• Forest fires. CDA estimated annual copper emissions of 1720 pounds statewide

(CDA, 2003b). Assuming forest fire emissions are proportional to land area, Bay 

Area emissions would be 4.0% of statewide emissions (based on the Bay Area Air 

Basin area of 6,619 square miles [BAAQMD, 2004] and California land area of 

163,696 square miles [DOF, 2002b]), or 69 pounds.

Together, these emissions total 340 pounds. These estimates do not include emissions 

from structural fires, which could release copper from wood and other copper-containing 

building components.

3.7.2.2 Copper Washoff into Urban Runoff

Copper deposited on Bay Area watersheds from both wet and dry deposition may run off 

to San Francisco Bay. SFEI estimated that 32% of copper in both wet and dry 

deposition is washed into San Francisco Bay (Tsai et al., 2001). In the absence of 

source-specific washoff information, this analysis assumes that the SFEI estimate is 

applicable to all air deposition sources.

3.7.2.3 Annual Copper Load

Using the above copper release and wash-off fraction estimates, the loads from 

identified copper air emissions sources can be estimated as follows:
Copper Sources in Urban Runoff and Shoreline Activities

45 November 2004

• Vehicle Fuels. If 32% of the 10 to 200 pounds of copper emitted from fuel 

combustion is washed into the Bay, the copper load would be 3 to 64 pounds per 

year.

• Industrial air emissions. If 32% of the 410 pounds of reported industrial copper 

emissions are washed into the Bay, the copper load would be 130 pounds per year.

• Fires. If 32% of the estimated release of 340 pounds is washed off, the copper load 

would be 110 pounds per year.

The total of the above copper loads (240 to 300 pounds per year) is substantially less 

than SFEI’s total estimate of copper load to San Francisco Bay from copper air 

deposition in Bay Area urban watersheds, 8,800 pounds per year (Tsai et al., 2001).

3.7.3 Control Measures

No control measures specific to copper air emissions have been identified. The 

BAAQMD regulates industrial air emissions to reduce releases of various air pollutants, 

including toxic air pollutants. It also conducts education programs that address all 

pollutant sources, including residential fireplaces. Many measures that reduce air 

pollution would also reduce copper emissions. Because the BAAQMD has not identified 

copper-containing compounds as a source of air quality problems, it has not specifically 

addressed copper emissions other than through the reporting requirements of its air 

toxics program.

The California Air Resources Board regulates air emissions from vehicles. While 

regulations technically address all air emissions, they focus on tailpipe emissions, which 

are significant contributors to major air quality problems in California. Vehicle emissions 

control devices probably remove some of the copper prior to emission from a vehicle’s 

tailpipe. This amount is unknown.

Measures to reduce vehicle miles traveled would reduce copper air emissions from 

diesel and gasoline fuel combustion. (See Section 3.3.3 for a discussion of these 

measures).

3.7.4 Uncertainty

The total air deposition quantity is based on actual measurements of copper deposition 

in the Bay area. After reviewing the data behind the estimate, its uncertainty was 

determined by SFEI to be low to moderate (Tsai et al., 2001). Sources of uncertainty in 

the estimates in this report include (but are not limited to):

• The industrial air emissions estimate may significantly understate copper air 

emissions, because BAAQMD does not require reporting of copper emissions less 

than 463 pounds per year. All reporting facilities emitted less than the reporting 

threshold. The high threshold may mean that many emitters are not reporting 

emissions. 

• The vehicle fuel estimate does not reflect any potential vehicular emissions from 

metals worn from engine parts that come in contact with the fuel, nor any metals 

losses within a vehicle engine or exhaust system.

• The fire estimate does not include emissions from structural fires.

• Vehicle brake pads are known to release copper to the air but are not included in this 

estimate because they are considered in Section 3.3. The extent to which air 

deposition measurements reflect copper from vehicle brake pads is currently not 

known. Investigations underway by the Brake Pad Partnership will estimate the 
Copper Sources in Urban Runoff and Shoreline Activities

46 November 2004

transport distance of vehicle brake wear debris. Using this information and 

information about the SFEI air deposition monitoring sampling locations, it will be 

possible to estimate the contribution of vehicle brake pads to the air deposition load 

estimated by SFEI.

• The contribution of other copper air emissions sources, such as wind and vehicle 

suspension of soils, is unknown.

3.7.5 Next Steps

• Load Estimate. Identification of the copper emissions that are the sources of 

measured air deposition is a priority. Since copper from vehicle brake pad wear may 

contribute to the measured deposition, the most cost-effective approach would be to 

wait to initiate the source investigation until after the Brake Pad Partnership 

completes its air deposition modeling (anticipated in spring, 2005).

• Control Measures. Additional controls on identified sources are not warranted. 

Feasibility of control measures for other copper air emissions sources should be 

explored once those sources are identified.

3.8 Soil Erosion

Each year, hundreds of construction sites cover thousands of acres of San Francisco 

Bay Area land, digging up the soil to build new homes, businesses, industries, and 

infrastructure. In order to prevent releases of soil and other pollutants into stormwater 

runoff, the State Water Resources Control Board requires all construction sites larger 

than 1 acre to participate in the construction stormwater permit program. There were 

about 700 active construction sites in the San Francisco Bay Area in 2003 (SWRCB, 

2004b).

Construction of new impervious surfaces in Bay Area watersheds also changes the 

quantity and timing of runoff flows in urban creeks. These changes can accelerate 

erosion of stream banks—potentially contributing significantly to sediment loads in 

runoff. Recent new development related amendments to urban runoff agency permits 

require development of hydromodification management plans to protect beneficial uses

in Bay Area creeks. 

The copper load estimate in the Metals Control Measure Plan used construction 

stormwater permit data and a rough estimate of erosion to estimate construction copper 

loads. Since that time, expansion of the permit system to include sites as small as 1 

acre has probably reduced construction site soil erosion and thus copper loads. The 

Metals Control Measure Plan assumed that remaining sediments in urban creeks were 

from natural erosion. Any contribution from changes in creek flows or other urban 

activities (e.g., landscaping) was not identified or estimated.

In runoff, eroded soils become “suspended solids” because they are entrained in water 

flows before they deposit in creeks or the Bay. The San Francisco Estuary Institute 

(SFEI) estimated the total quantity of suspended solids in urban runoff in the report 

Contaminant Loads From Stormwater to Coastal Waters in the San Francisco Bay 

Region (Davis et al., 2000). The study estimated that about half (51%) of the solids in 

Bay Area stormwater come from agricultural land uses. Open space (22%) and urban 

areas (residential, commercial, and industrial land uses, 27%) each comprised about a 

quarter of the solids load.
Copper Sources in Urban Runoff and Shoreline Activities

47 November 2004

3.8.1 Background

San Francisco Bay area soils—like soils from elsewhere in the nation—contain trace 

levels of copper naturally. When soil washes off urban areas, it carries copper with it to 

San Francisco Bay. While a certain amount of soil erosion is normal, human activities in 

Bay Area watersheds have accelerated soil erosion. Watershed modifications like dams 

and flood control projects also change the flow of sediments to San Francisco Bay.

3.8.2 Copper Loads

3.8.2.1 Construction Sites

The estimation method from the Metals Control Measure Plan was used to estimate the 

regional copper releases to urban runoff from copper in construction site soils, starting 

with data from the State Water Resources Control Board Construction Stormwater 

Database for the San Francisco Bay Area (SWRCB, 2004b). The methodology involves

the following estimates:

• Area under construction. Using the information in the database, the average number 

of acres under construction during the rainy season (November-April) in 2003 was

estimated to be 9,067 acres. 

• Erosion rate and soil copper concentrations. The Metals Control Measure Plan

values (7,500 pounds per acre and 38.57 mg/kg, respectively) were used.

Using the above values, the copper load from construction sites is estimated to be about 

2,600 pounds per year.

3.8.2.2 Development-Related Hydromodification

No basis exists to prepare a specific quantitative estimate of the copper load from 

hydromodification of Bay Area urban creeks. The way creeks are affected by changes in 

flows are highly variable, depending on the characteristics of the watershed and the new 

development. Preparing an estimate would require an assessment of each Bay Area 

watershed affected by hydromodification. The load can, however, be bracketed by the 

copper load estimated from total urban suspended solids loads (below).

3.8.2.3 Annual Copper Load—All Soil Erosion Sources

Using SFEI’s best estimate of suspended solids discharges in stormwater runoff and the 

Metals Control Measure Plan soil copper concentration estimate, the annual copper load 

in urban runoff from soil erosion can be estimated. SFEI estimates that 27% of the best 

estimate of 680,000,000 pounds of suspended solids in all Bay Area runoff is from urban 

areas—a total of 180,000,000 pounds of solids. These solids contain about 7,000 

pounds of copper attributed to urban soil erosion.

3.8.3 Control Measures

Control measures are already in place for both construction and hydromodificationrelated soil erosion.

Construction. The primary control measure for construction site stormwater is the 

Construction Storm Water General Permit program, managed by the State and Regional 

Water Quality Control Boards. Facilities covered by the permit must prepare and 

implement Storm Water Pollution Prevention Plans and monitoring plans. The state 

regulatory program is supplemented by the required new development and construction 

controls element of municipal stormwater programs. 
Copper Sources in Urban Runoff and Shoreline Activities

48 November 2004

Individual municipalities have explored a variety of methods to enhance the 

effectiveness of their construction stormwater programs. For example, many 

municipalities combine construction stormwater inspections with other routine 

inspections of the same sites (e.g., by building code enforcement). Construction 

stormwater best management practices information is routinely distributed by municipal 

building departments. As municipalities incorporate new requirements for postconstruction stormwater treatment measures, they are changing their relationships with 

construction sites, which may modify the level of oversight occurring during the 

construction phase. 

No data are currently available to estimate the effectiveness of the regulatory and 

education programs in reducing copper discharges.

Hydromodification. The primary control measure for soil erosion from creek 

hydromodification due to urban development is the hydromodification management 

requirement within the new development requirements incorporated in Bay Area 

stormwater agency permits. This requirement addresses new development; it does not 

require retrofitting to manage erosion increases from past development, which may 

continue to occur for many years after the development is in place. Municipalities are 

just beginning to implement the required planning actions, so no data are available 

regarding their effectiveness in reducing soil erosion.

3.8.4 Uncertainty

On the basis of the uncertainty in SFEI’s total sediments load estimate Davis et al., 

2000), the soil erosion copper load estimate is moderately uncertain. Sources of 

uncertainty in the current estimate include (but are not limited to):

• Hydromodification-related sediment loads. Although site-specific studies have 

included sediment load estimates, no regional assessment of hydromodificationrelated sediment loads has been prepared. Site-specific studies (e.g., SCVURPPP, 

2003a) suggest that hydromodification related sediment loads—and thus copper 

loads—have the potential to be significantly higher than the <5,000 pounds 

suggested by the regional total sediment load estimate minus the construction load 

estimate.

• Construction site sediment releases. The primary source of uncertainty in the 

construction estimate is that the sediment release estimate, which is based on 

colloquial information and does not account for the soil erosion reductions achieved 

by the use of construction site best management practices required by construction 

stormwater permits. Metals concentrations used in the estimate (data from the 

Calabazas Creek watershed in Santa Clara Valley) may not be representative of 

copper concentrations in soils elsewhere in the Bay Area. 

• Omission of small construction sites. Since the Construction Stormwater Database 

does not includes sites smaller than 1 acre, small sites are not included. While small 

sites may contribute additional copper loads, this error is expected to be less 

important than other sources of uncertainty.

• Omission of soil erosion from non-construction urban activities. Accelerated soil 

erosion due to ordinary residential and business activities other than construction 

(such as landscaping) are not included in the load estimate.
Copper Sources in Urban Runoff and Shoreline Activities

49 November 2004

3.8.5 Next Steps

• Load Estimate. Given that the control measures are unlikely to change, a more 

accurate load estimate is not necessary at this time. Using the construction 

stormwater permit data to compare previous and current sediment loads could, 

however, be generally helpful in understanding the efficacy of stormwater permits as 

a control measure.

• Control Measures. Since the Construction Storm Water General Permit already 

regulates construction stormwater runoff, and the new development 

hydromodification planning requirement will control hydromodification-related soil 

erosion, additional controls are not needed.

3.9 Copper in Domestic Water Discharged to Storm Drains

Most of the San Francisco Bay Area’s drinking water supply flows into homes and 

businesses, where it is used indoors and discharged to the sewer—or piped outdoors to 

irrigate landscaping. A small fraction of drinking water flows into gutters and storm 

drains from activities like hydrant flushing, water main cleaning, outdoor water-based 

cleaning activities, and irrigation overflows. This water carries the traces of copper it 

contains into creeks and San Francisco Bay.

The Metals Control Measure Plan used detailed South Bay-specific information to 

estimate copper levels in the drinking water supply. This information was combined with 

a somewhat generic estimate of the fraction of drinking water that flows to storm drains

(10% of the volume of drinking water not discharged to sewers). The estimate assumed 

that all drinking water flows through copper pipes. Most of the estimated copper load 

was from corrosion of copper pipe. 

3.9.1 Background

Copper in the drinking water supply comes from the following sources:

• Trace copper in the raw water supply. This copper comes from natural minerals, or 

(in river water supplies) from upstream stormwater and wastewater discharges to the 

water source.

• Algaecides. To control nuisance algae—and prevent the unpleasant taste and odor 

associate with it—some water supply agencies apply copper-containing algaecides 

to reservoirs. 

• Corrosion of copper pipes in buildings. Although copper pipe is long-lasting, it slowly 

wears down during use, through a combination of chemical corrosion and physical 

erosion of the pipe surface. Corrosion rates—and therefore drinking water copper 

content—vary by water supply, depending on factors like pH and trace ionic 

composition.

Most—but not all—drinking water receives some type of purification treatment prior to 

distribution to homes and businesses. Water purification treatments typically remove a 

portion of the copper in the source water. Subsequent to purification, disinfectants (e.g., 

chlorine or chloramines) and additives to modify the water supply’s corrosivity and 

fluoride levels are added. Because additives are high purity chemicals, they are not 

believed to add significant amounts of copper to the water supply. 

3.9.2 Copper Loads

No additional information was identified to improve the load estimation method used in 

the Metals Control Measure Plan. Since water use is generally proportional to 
Copper Sources in Urban Runoff and Shoreline Activities

50 November 2004

population, the previous copper load estimate (700 pounds/year) was adjusted on the 

basis of the ratio of the San Francisco Bay Area population–6,994,500 (DOF, 2003) to 

the 1995 Santa Clara County population—1,568,200 (DOF, 2002a),

21 to estimate that 

copper releases from urban storm drains discharge of drinking water is 3,000 pounds 

per year.

3.9.3 Control Measures

Both reducing discharge of drinking water to storm drains and reducing the copper level 

in drinking water can reduce copper loads from domestic water discharged to storm 

drains. 

Reducing storm drain discharges. Most San Francisco Bay Area water suppliers have 

water conservation programs; some municipalities also have their own programs. These 

programs work in tandem with public outreach from municipal stormwater programs. 

However, most such programs emphasize messages other than reducing drinking water 

discharges to storm drains. Two water conservation pilot programs by the Irvine Ranch 

Water District (IRWD) have recognized and evaluated storm drain discharge reductions 

as a benefit of improved irrigation water management (IRWD, 2004). 

• Installation of evapotranspiration irrigation controllers and generally improving

irrigation water management in a test neighborhood reduced dry weather storm drain 

discharges by about 20% (IRWD, 2003).

• Wick irrigation of lawns is being tested in lawns; this method has the potential to 

almost eliminate lawn irrigation-related storm drain discharges.

Although IRWD materials do not specify the costs of these measures, costs are not 

insignificant, as these systems required physical installation of new irrigation controllers 

and/or new irrigation water distribution systems, in addition to outreach and education.

Reducing copper levels in drinking water. Water suppliers and wastewater treatment 

plants have explored options to reduce copper levels in drinking water. These options 

have been explored on a voluntary basis, because only the California Department of 

Health Services regulates drinking water supply quality. Many water suppliers have 

reduced copper-based algaecide use (see Section 3.5). Water supply modifications to 

reduce corrosivity have proven more challenging. The potential for copper reduction is 

very water supply specific, thus specific measures need to be developed and tested just 

to determine if reductions are feasible. Water suppliers vary in their willingness to 

consider modifying water supply corrosivity; they must grapple with customer 

acceptance, regulatory, cost, and management issues.

3.9.4 Uncertainty

Because of the many region-specific data used in the estimate extrapolated to the Bay 

Area, this estimate has moderate-high uncertainty. Sources of uncertainty in the current 

estimate include (but are not limited to):

• Contact with copper pipe. Most of the estimated copper load comes from the 

assumption that all discharged water flows through copper pipes. Since exterior 

copper pipes are relatively rare, this is approximately the same as assuming that 

discharged water flows through buildings. Much of the water discharged to storm 

drains never enters buildings. For example, water for hydrant flushing, water main 

cleaning, water supply system leaks, and some irrigation water—particularly for 

 

21 The Metals Control Measure Plan water supply use estimate was based on 1995 data.
Copper Sources in Urban Runoff and Shoreline Activities

51 November 2004

common irrigation overflow locations like median strips and large landscaped 

areas—never enters copper pipe.

• Fraction of drinking water discharged to storm drains. The estimate of the amount of 

drinking water discharged to storm drains is based on limited data from Santa Clara 

Valley water purveyors and wastewater treatment plants, and the assumption that 

storm drain discharges comprise 10% of the volume of drinking water not discharged 

to sewers. This estimate may not reflect conditions elsewhere in the Bay Area, and 

may not accurately reflect discharge volumes.

• Representativeness of Santa Clara Valley water supply copper data. The copper 

concentrations in water supplies in other portions of the Bay Area differ from those in 

Santa Clara Valley. It is uncertain whether this might bias the estimate high or low.

3.9.5 Next Steps

• Load Estimate. Developing a more accurate estimate would be costly, and would be 

unlikely to modify the ability to control the discharge.

• Control Measures. Since the available control measures are already being pursued 

by other agencies and have shown only limited efficacy, additional controls are not 

warranted.

3.10 Vehicle Fluid Leaks and Dumping

Photos of motor oil in water bodies—and the negative public reaction to this visible water 

pollution—was one of the motivations for initiation of Federal programs to regulate urban 

stormwater runoff. Oil spots in streets, parking lots, and driveways remain a visual 

reminder of this ubiquitous source of water pollution. 

Since their inception, municipal urban runoff programs have targeted illegal dumping and 

other improper discharges of pollutant-containing materials. Although little quantitative 

data are available to characterize improper discharges, increasing public awareness that 

storm drains carry water directly to creeks, San Francisco Bay, and the Pacific Ocean 

without treatment suggests that urban runoff programs have reduced improper 

discharges. Regulation of industrial and certain commercial discharges has terminated 

thousands of improper discharges in the San Francisco Bay area, eliminating many 

potential copper sources. Since municipalities focused on eliminating—rather than 

measuring—improper discharges, little or no quantitative data exists on such copper 

releases.

The Metals Control Measure Plan used colloquial and limited quantitative information to 

estimate copper releases from leaks and illegal dumping of vehicle fluids (motor oil and 

coolant). A recent study also estimated the potential contribution from vehicle fluids to 

copper in urban runoff, finding a negligible contribution (Davis et al., 2001). 

Measurements of copper concentrations in motor oil for that study found a typical 

concentration similar to that used in the Metals Control Measure Plan estimate. While 

other copper-containing improper discharges certainly occur, it is likely that urban runoff 

education and regulatory programs have directed the most copper-laden of these 

discharges (e.g., cooling water, vehicle service facility discharges, commercial vehicle 

wash water) away from storm drains.

3.10.1 Background

Neither motor oil nor coolants typically contain meaningful concentrations of copper. 

While inside vehicles, both fluids pick up copper from copper and brass vehicle parts. 

Spent solutions may be enriched in copper and other metals. 
Copper Sources in Urban Runoff and Shoreline Activities

52 November 2004

3.10.2 Copper Loads

Previous estimates from the Metals Control Measure Plan were adjusted as follows:

• Activity factor adjustment. Adjustments were made on the basis of the activity factor 

used in the Metals Control Measure Plan (MCM Plan)—see Table 16. The number 

of registered cars and trucks (5,432,514 in 2002) was obtained from the Metropolitan 

Transportation Commission (MTC, 2004a). The annual vehicle miles value (167.2 

million miles per day or 6.1 x 1010 miles per year in 2003) was obtained from the Bay 

Area Air Quality Management District (BAAQMD) (BAAQMD, 2004).

• Do-it-yourself vehicle maintenance survey data adjustment. Two assumptions were 

adjusted on the basis of a statewide do-it-yourself vehicle maintenance survey by the 

California Integrated Waste Management Board (CIWMB, 2002). The estimated 

fraction of do-it-yourself fluid changes was reduced from 50% to 19% and the 

estimated improper disposal fraction was reduced from 50% to 19%.

Table 16. Motor Vehicle Fluid Improper Discharge Estimates

Improper 

Discharge

Previous 

Estimate

(lb Cu/yr)

Previous 

Activity Factor

Current 

Regional 

Activity Factor

Regional 

Estimate

(lb Cu/yr)

Coolant leaks 112 1,130,000 

vehicles

5,432,514 

vehicles

500

Coolant dumping 116 1.2 x 1010 miles 

driven per year

6.1 x 1010 miles 

driven per year

90

Oil leaks <1 1,130,000 

vehicles

5,432,514 

vehicles

<1

Oil dumping 7 1,130,000 

vehicles

5,432,514 

vehicles

4

Total 600

Source: TDC Environmental calculations based on data sources and assumptions above.

3.10.3 Control Measures

All municipal urban runoff programs include commercial/industrial, illicit discharge, and 

public information programs as core program elements. Together these program

elements address all types of improper discharges. Other than the survey information 

used in developing the load estimate (which implies a reduction in illegal dumping), no 

quantitative data are currently available to estimate the effectiveness of these regulatory 

and education programs in reducing improper discharges of vehicle fluids.

3.10.4 Uncertainty

Given the paucity of data characterizing improper discharges, the estimate is 

moderately-highly uncertain. Sources of uncertainty in the current estimate include (but 

are not limited to):

• Copper concentrations in waste oil and coolant are from rather elderly sources. 

Current copper levels in waste fluids may differ, particularly because manufacturerrecommended fluid replacement frequencies are lower, so fluids spend more time in 

contact with copper-containing vehicle parts.

• Manufacturer-recommended fluid change frequencies have decreased.

• Leakage and dumping estimates were based on colloquial information. Data gaps 

include quantity, frequency, and copper content of improper discharges. In the 
Copper Sources in Urban Runoff and Shoreline Activities

53 November 2004

absence of authoritative data on leakage and dumping rates, the Metals Control 

Measure Plan relied on colloquial information and professional judgment. Given the 

effectiveness of education programs and improved vehicle designs in the last 

decade, both leak and dumping rates are likely to have declined.

• Estimates assume that all released copper flows to San Francisco Bay. Some or all 

of the copper in leaked fluids is likely to build up and wash off in a manner similar to 

other anthropogenic copper deposited on impervious surfaces, suggesting less than 

complete wash-off to San Francisco Bay (Carleton, 2004).

3.10.5 Next Steps

• Load estimate. Although the load estimate is uncertain, it is small enough that 

additional study of this source is not warranted.

• Control measures. Control measures already in place have addressed this source. 

Given the relatively small load estimate, additional controls are not warranted.

3.11 Sources Not Evaluated

In theory, there are thousands of potential sources for copper in urban runoff and 

shoreline activities. Since the purpose of this report was to identify major sources, it 

does not include a comprehensive review of other possible copper sources. This 

subsection provides a brief description of the reasons for omission of some of the copper 

sources mentioned in previous studies or in the literature. 

The following “sources” convey copper from primary copper sources into urban runoff:

• Runoff from residential, commercial, industrial, and institutional land uses

• Car washing

• Streets

• Parking Lots

The following are copper sources, but are not significant sources to urban runoff or from 

shoreline activities:

• Wastewater treatment plants and all discharge sources to the sewer system

• Mines

• Local reservoir releases, including algaecides directly discharged

• Non-urban soil erosion

• Agricultural pesticide and fertilizer use

• Landfills

The following sources are anticipated to be relatively small sources of copper release in 

urban runoff:

• Tires. Other stormwater source identification studies have not found tires to be a 

significant copper source (Sorme and Lagerkvist, 2002; Davis et al., 2001; CDA, 

2003b). Although tires wear off on roads during use, the copper content of tires 

(about 2 parts per million) is relatively low (less than 10% of the copper concentration 

in Bay Area soils). 

• Illicit connections and improper discharges. Illicit connections and improper 

discharges have been among the major focuses of urban runoff programs, which 

have sought to eliminate all identified improper discharges. Around the San 

Francisco Bay area, it is likely that thousands of discharge sources have been 

eliminated or redirected to the sewer system. Although copper-containing 

discharges (like cooling water from industry or debris from waste materials used in 
Copper Sources in Urban Runoff and Shoreline Activities

54 November 2004

sandblasting) may have occurred in the past, municipal, industrial, and construction 

stormwater permit requirements have ensured that regulators from Bay Area 

agencies and staff from local businesses and institutions have worked diligently to 

eliminate such discharges. It is unlikely that significant numbers of illicit connections 

remain after about 10 years of urban runoff regulation.

• Building paint. According to the Copper Development Association (CDA), copper 

pigments and biocides are commonly present in exterior paint. The CDA cites only 

one investigation of paint copper content, which found a medial concentration of 21 

parts per million (CDA, 2003b). Since this concentration is relatively low (lower than 

the copper concentration in Bay Area soils) if the data are representative, paint is 

probably a negligible source.

• Exposed electrical wires. Most electrical wires are made of copper. The only 

identified exposed electrical wires in the Bay Area are those associated with San 

Francisco MUNI’s electric bus and streetcar operations. The copper in these wires 

may wear off as streetcar electrical connections pass by them. These lines occur 

primarily (if not exclusively) in areas where the stormwater runoff flows to wastewater 

treatment plants, and thus are unlikely to contribute significantly to copper levels in 

San Francisco Bay area urban runoff.

• Asphalt. In an area with accelerated asphalt pavement wear due to use of studded 

snow tires, asphalt’s contribution to urban runoff copper levels was estimated to be 

relatively small (Sorme and Lagerkvist, 2002).

While no previous copper source identification study has found the following sources to 

be significant, available information does not provide sufficient evidence to evaluate their 

significance:

• Airplane brakes. While airplane brakes are known to contain copper, the exact 

copper content is not known. The primary point of potential copper release is on 

airport runways. At larger airports runways are cleaned (frequency unknown). At 

most airports the runoff is subject to some type of treatment. At Bay Area airports 

without runoff management systems, the runoff flows through vegetated areas prior 

to entering a drainage system or a surface water body. Airport stormwater 

monitoring data would likely be able to shed light on whether airport runoff is 

elevated in copper as compared to other urban runoff.

• Electrical motors. Most electrical equipment is used indoors or in relatively 

weatherproof outdoor locations, as water and moisture-related corrosion may 

damage it. Electrical motors and generators contain parts that may wear off, 

potentially releasing copper-containing particles. Some older design motors (“brush 

DC”) incorporate brushes that usually contain copper. If electrical motors are 

commonly placed in manners that do not contain wear debris—and if wear rates for 

copper-containing parts are significant—they could meaningfully contribute to copper 

levels in urban runoff. 

• Fertilizers. CDA reports that about 54 million tons of commercial fertilizers were 

used in the U.S. in 1996 (CDA, 2003b). Many fertilizers contain copper, according to 

the CDA at concentrations from 0 to 39,900 parts per million (CDA, 2003b) The 

average copper concentration of fertilizers is not available. Since plants use the 

copper as a micronutrient, it is unclear how much copper enrichment of soil surfaces 

occurs as a result of fertilizer application. The fraction of this copper that may wash 

off is not known, though it would be reasonable to assume that wash-off fractions are 
Copper Sources in Urban Runoff and Shoreline Activities

55 November 2004

similar to those for copper-containing pesticides applied to soils and therefore are 

probably small.
Copper Sources in Urban Runoff and Shoreline Activities

56 November 2004

4.0 CONCLUSIONS AND RECOMMENDATIONS

4.1 Conclusions

Conclusion 1. The significant sources of copper in urban runoff flowing to San Francisco 

Bay Area are vehicle brake pads, copper air emissions, architectural copper, industrial 

copper use, domestic water discharged to storm drains, soil erosion, and copper 

pesticides. Table 17 summarizes the copper load estimates and their uncertainties. 

Table 17. Summary of Copper Sources in Urban Runoff

(Pounds of Copper per Year Discharged to San Francisco Bay)

Copper Source Load Estimate Uncertaintya

Vehicle brake pads

Estimate includes:

Original equipment pads

Replacement brake pads

Brake pads on heavy-duty trucks, off-road 

 vehicles, rail cars, and motorcycles

>10,000

10,000

?

?

High

Architectural copper 4,500 Moderate-High

Copper pesticides

Estimate includes:

Landscaping

Wood preservatives

Pool, spa, and fountain algaecides

<8,000 – <10,000

1,200 to 2,500

1,400 to 2,800

<5,000

High

Industrial copper use 3,300 Moderate

Deposition of copper air emissions

Estimate includes:

Diesel and gasoline fuel combustion

Industrial facilities

Residential wood burning and forest fires

Unknown

8,800b

3 – 60

130

110

>8,000

Low to Moderate

Soil erosion

Estimate includes:

Construction

Hydromodification

7,000

2,600

<5,000

Moderate

Copper in domestic water discharged to storm 

drains

3,000 Moderate-High

Vehicle fluid leaks and dumping 600 Moderate-High

aUncertainty is defined as follows: Low indicates that the estimate has an error within 50%; Moderate

indicates that the estimate has an error up to 2 fold; Moderate-high indicates that the estimate has an error

up to 5 fold; High indicates an error up to 10 fold (see Section 1.4).

bMay overlap with vehicle brake pad estimate.

Source: Section 3.

Conclusion 2. Shoreline copper sources have the potential to contribute significantly to 

copper levels in San Francisco Bay. Table 18 summarizes shoreline copper load 

estimates and their uncertainties.

Table 18. Summary of Shoreline Copper Sources

(Pounds of Copper per Year Released to San Francisco Bay)

Copper Source Load Estimate Uncertainty

Marine antifouling coatings 20,000 Moderate-High

Copper algaecides applied surface waters 4,000 High

Source: Section 3.
Copper Sources in Urban Runoff and Shoreline Activities

57 November 2004

Conclusion 3. The total of all estimated urban runoff copper loads (45,000 – 47,000 

pounds per year, assuming air deposition does not overlap with other identified sources)

is less than the total estimated stormwater copper load to San Francisco Bay (90,000 

pounds per year, see Table 19). (Marine antifouling coatings and copper algaecides 

applied to non-industrial surface waters are assumed not contribute to urban runoff 

copper loads). Since many source estimates are highly uncertain, it is entirely possible 

that one or more estimates understates actual copper releases. While it is also possible 

that a significant copper source has not been identified, given the extensive 

investigations of copper sources for nearly 15 years in the San Francisco Bay Area, it is 

unlikely that a major source would not have been identified.

Table 19. Copper Load Estimates for San Francisco Bay

Sources Copper Load (lb/yr)*

All sources (excluding contribution from Delta) 160,000

Stormwater runoff from all land uses 150,000

Urban portion of total stormwater copper load 

(Residential, commercial, and industrial land uses)

90,000

*“Best estimate”

Source: Contaminant Loads From Stormwater to Coastal Waters in the San Francisco Bay Region (Davis et al., 

2000)

4.2 Recommendations

Recommendation 1. Control measures are warranted for vehicle brake pads, copper air 

emissions, architectural copper, industrial copper use, domestic water discharged to 

storm drains, soil erosion, and copper pesticides. Control measures are already in place 

for most of these sources. Table 20 (on the next page) summarizes identified feasible 

control measures (many of which are already being implemented by one or more San 

Francisco Bay Area agencies) and recommended priorities for investigation. In addition 

to the listed control measures, public outreach is feasible for all copper sources. 

Recommendation 2. Control measures are warranted for marine antifouling coating 

copper shoreline releases. No control measures are currently in place for this source. 

Prior to implementing control measures, additional investigation is recommended and a 

pilot project should be considered (see Table 20). 

Recommendation 3. Improved load estimates for copper pool, spa, and fountain 

algaecides are needed to determine the appropriate types of control measures.

Recommendation 4. Investigation is needed to determine appropriate control strategies 

for copper marine antifouling coatings and copper air emissions sources.

Recommendation 5. Because measures to reduce landscaping copper pesticide use 

could adversely impact human health or the environment, potential measures and their 

impacts should be evaluated for safety and effectiveness prior to implementation.
Copper Sources in Urban Runoff and Shoreline Activities

58 November 2004

Table 20. Summary of Feasible Control Measures (Other than Public Outreach) and Priorities for Investigation 

for Copper Sources in Urban Runoff and Shoreline Activities

Copper Source Feasible Control Measures Priorities for Investigation

Vehicle brake pads • Brake Pad Partnership (BPP) • Improved load estimate (BPP)

Architectural copper • Requirements for management of wastewater from 

cleaning and treatment

• After completing the recommended investigation, 

consider limiting installation and/or requiring measures 

to prevent copper releases or to treat roof runoff

• Practicality and efficacy of control measures 

such as coatings and runoff treatment 

measures

Copper pesticides • Consider developing best management practices for 

wood preservatives to minimize copper use where 

releases are most likely

• Regulatory control measures for pool, spa, and fountain 

algaecides are feasible; use improved load estimate to 

determine if they are warranted

• Improved estimate of the copper load from 

algaecides (primarily pool, spa, and fountain 

algaecides); use estimate to determine 

whether regulatory measures are warranted

• Evaluate alternative practices and pesticides 

for landscaping to determine if safe and 

effective alternatives exist

Industrial copper use • Industrial stormwater permit program None

Copper air emissions • Not able to identify appropriate measures at this time

• Additional controls on identified sources are not 

warranted

• Identify major air emissions sources

• Determine overlap with brake pad wear 

debris (BPP studies will provide data)

Soil erosion • Construction stormwater permit program

• Hydromodification management plan requirement

None

Copper in domestic water 

discharged to storm drains

• None (other than public outreach) None

Vehicle fluid leaks and 

dumping

• None necessary (other than public outreach) None

Marine antifouling coatings • Not able to identify appropriate measures at this time

• Consider a non-toxic antifouling coatings pilot project 

• Bay Area-specific load estimate

• Participate in IACC Copper Antifouling Paint 

Sub-Workgroup investigation of copper 

problem and control measures

Copper algaecides applied to 

surface waters

• Aquatic pesticides permit program None

Source: Section 3.
Copper Sources in Urban Runoff and Shoreline Activities

59 November 2004

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Copper Sources in Urban Runoff and Shoreline Activities

65 November 2004

APPENDIX A. Lower South San Francisco Bay Copper Action Plan

Actions

Information in this appendix: 

Table A-1. Copper Action Plan Baseline (Table 4-1) Actions

Table A-2. Copper Action Plan Phase I (Table 4-2) Actions

Table A-3. Copper Action Plan Phase II (Table 4-3) Actions
Copper Sources in Urban Runoff and Shoreline Activities

66 November 2004

Table A-1. Copper Action Plan Baseline (Table 4-1) Actions

Action Description Copper Source

B-1 Vehicle washing consistency in level of implementation Vehicle washing, 

including mobile 

cleaners (conveys 

copper from brake 

pads, other vehicle 

sources, and soil)

B-2 Continue to track copper sulfate use by water suppliers 

(includes State & Federal water project)

Copper algaecides

B-3 Complete Industrial-2: investigations (based on 

MCMP), identify and implement reasonable controls in 

conjunction with industry (older printed circuit board 

manufacturers with copper plating) to reduce elevated 

levels in runoff from targeted industry including 

development/implementation of education and outreach 

plan

Clarify linkage with POTW Pretreatment program

Industrial copper 

uses

B-4 1-Provide appropriate level of local support for agreed 

upon quantification studies to:

2-Investigate and/or track quantification studies for a 

wide range of existing copper control/pollution 

prevention measures and sources loadings (update 

copper pie charts contained in MCM based on data 

from B-6 and B-16)

3-Collect data and prepare annual reports on the 

following potential indicators

Copper content in new auto brake pads

• Total population in basin

• Auto/truck vehicle traveled in basin

• Copper sulfate (e.g., algaecide, pesticide, 

industrials; chemicals) sales in basin (aggregate 

basis-scaled to basin level estimate)

• Copper content in macoma tissue at Sand Point 

(Palo Alto

• Reproductivity index for macoma at Sand Point

• Benthic community assemblages at Sand Point

4-Prepare issue paper on feasibility of potential field 

investigation to monitor long-term trends between 

copper from brake pads and concentration in water

All sources
Copper Sources in Urban Runoff and Shoreline Activities

67 November 2004

Table A-1. Copper Action Plan Baseline (Table 4-1) Actions (Continued)

Action Description Copper Source

B-5 Provide appropriate level of local support for agreed 

upon BPP activities consistent with MCM

1-Review/assess/provide input on BMC/BPP brake pad 

wear debris research & brake pad content data

2-Ensure that other local state and Federal players are 

involved appropriately on brake pads issue as it is a 

widespread urban concern

3-Assist in making research data that are in the public 

domain accessible

Brake pads

B-6 Review appropriateness of transportation control 

measures, prioritize reasonable measures and identify 

potential efforts for further development as part of 

Phase I and implementation as part of Phase II

Brake pads and 

other vehicle 

sources

B-7 Establish transportation/impervious surface “forum”

• Consider results of VMT and imperviousness load 

estimates and control effectiveness evaluation; 

identify potential control efforts for further 

development as part of Phase I and implementation 

as part of Phase II

Brake pads and 

other vehicle 

sources

B-8 Continue to implement watershed classification and 

assessment efforts of SCBWMI and improve 

institutional arrangements for watershed protection 

(review Vol. II Chapter 5/CCMP/CONCUR findings for 

relevance and possible gaps as part of C-31)

n/a

B-9 Continue current efforts and track corrosion control 

opportunities:

• Continue educational outreach, within the City of 

Palo Alto, to plumbers and designers to reduce 

corrosion of copper pipes via better design and 

installation

• Track developments in (1) alternatives to copper 

piping (b) corrosion inhibitors, and (c) other methods 

of reducing copper corrosion

Copper pipes

B-10 Utilize results of SEIDP indicator #5 (Sediment 

Characteristics and Contamination) to investigate 

development of an environmental indicator and 

investigate the linkage with SFEI sources and loading

work effort

n/a

B-11 Consider need for Continuous Improvement of street 

sweeping controls and storm water system operation & 

maintenance controls (key emphasis is to develop SOP 

for disposal of collected materials)

Brake pads, other 

vehicle sources, and 

soil

B-12 Maintain existing education and outreach program for 

pools and spas

Copper algaecides
Copper Sources in Urban Runoff and Shoreline Activities

68 November 2004

Table A-1. Copper Action Plan Baseline (Table 4-1) Actions (Continued)

Action Description Copper Source

B-13 Track POTW Pretreatment Program efforts and 

POTW loadings

Wastewater (conveys 

copper from many 

sources)

B-14 Track and encourage water recycling efforts Wastewater (conveys 

copper from many 

sources)

B-15 Utilize results of SEIDP to evaluate effective ness of 

related SCVURPPP Performance Standards and 

identify cost-effective modifications

n/a

B-16 Establish Information Clearinghouse 

(Track & disseminate new scientific research on 

copper toxicity, loadings, fate and transport, and 

impairment of aquatic ecosystems for use in CAP 

update; provide stakeholder resource)

n/a

B-17 Track and encourage investigation of several 

important topics that influence uncertainty with Lower 

South Bay Impairment Decision 

• Phytoplankton toxicity and movement (IAR 

Section 5.3.1)

• Sediment cycling

• Loading uncertainty. Encourage incorporation of 

appropriate bioassessment tools into ongoing 

monitoring programs to track presence of coppersensitive taxa in LSB

Prepare issue paper on feasibility and cost of 

addressing phytoplankton toxicity questions

n/a

B-18 Track and encourage investigation of important 

factors that influence copper and fate (potential 

reduction in uncertainty is moderate to high)

• Investigate flushing time estimates for different 

wet weather conditions

• Investigate location of northern boundary condition

• Determine Cu-L1 and L2 complex concentrations

• Investigate algal uptake/toxicity with competing 

metals

n/a

B-19 Continue to promote industrial water use and reuse 

efficiency. These programs may include workshops, 

outreach, incentives, or audits (see Appendix 4-1 #35)

Industrial copper use 

(and other water 

supply sources)

B-20 Revise copper conceptual model report findings and 

produce status report (revise conceptual model 

uncertainty table, appendix __ based on available 

information)

n/a

B-21 1-SCVURPPP & Co-permittees evaluate feasibility of 

discouraging architectural use of copper & explore 

feasibility of related policy

2-Promote Green Building principles and identify 

measures to investigate as part of Phase I

Architectural copper
Copper Sources in Urban Runoff and Shoreline Activities

69 November 2004

Table A-2. Copper Action Plan Phase I (Table 4-2) Actions

Action Description Cu Source

I-1 Update findings and recommendations of BPP efforts and 

implement agreed upon Phase I measures and develop Phase 

II Work Plan

Brake pads

I-2 Update findings and recommendations of 

transportation/impervious surface “forum” and implement 

agreed upon Phase I measures and develop Phase II Work 

Plan

Brake 

pads, other 

vehicle 

sources

I-3 Update and re-evaluate source identification (MCMP for copper) 

and prioritize sources based on effectiveness evaluation of 

future potential control actions. Prepare and implementation 

plan reflecting the priorities and implement agreed upon Phase I 

control actions.

All sources

I-4 Prepare and implement a Phase I plan for improved corrosion 

control based on evaluation of results of Baseline measures

Copper 

pipes

I-5 Evaluate street sweeping and other design, operation and 

maintenance practices to identify potential improvements. 

Prepare and implementation plan reflecting the priorities and 

implement agreed upon Phase I control actions.

Brake 

pads, other 

vehicle 

sources, 

soil

I-6 Follow-up on relevance of copper in diesel exhaust Diesel fuel

I-7 Develop Phase II Implementation Plan for POTW expansion for 

water recycling

Wastewater 

(conveys 

copper 

from many 

sources)

I-8 Evaluate and investigate important topics that influence 

uncertainty with LSB Impairment Decision

• Phytoplankton toxicity and movement (IAR Section 5.3.1)

• Sediment cycling

• Loading uncertainty

n/a

I-9 Evaluate and investigate important factors that influence copper 

fate (potential reduction in uncertainty is moderate to high)

• Investigate flushing time estimates for different wet weather 

conditions

• Investigate location of northern boundary condition

• Determine Cu-L1 and L2 complex concentrations

Investigate algal uptake/toxicity with competing metals

n/a

I-10 Evaluate results of tracking industrial virtual closed-loop 

wastewater efficiency measures and develop potential actions. 

Prepare an implementation plan reflecting the priorities and 

implement agreed upon Phase I control actions.

Industrial 

copper 

uses

I-11 Develop Phase II implementation plan for POTW process 

optimization

Wastewater 

(conveys 

copper 

from many 

sources)

I-12 Develop a Phase II plan include a re-evaluation for Phase I 

actions

All sources
Copper Sources in Urban Runoff and Shoreline Activities

70 November 2004

Table A-3. Copper Action Plan Phase II (Table 4-3) Actions

Action Description Cu Source

II-1 Reconsider usefulness of management stormwater 

through POTWs

Urban runoff 

(conveys copper 

from many 

sources)

II-2 Implement agreed upon Phase II surface control 

measurement (transportation/imperviousness/brakepad)

Brake pads, other 

vehicle sources

II-3 Implement plan for additional corrosion control measures Copper pipes

II-4 Discourage use of copper based pesticides Copper-based 

pesticide

II-5 Implement control actions identified for copper in diesel 

exhaust

Diesel fuel

II-6 Implement Phase II POTW process optimization 

measures

Wastewater 

(conveys copper 

from many 

sources)

II-7 Implement agreed upon Phase II expansion of water 

recycling programs

Wastewater 

(conveys copper 

from many 

sources)

II-8 Re-evaluation Phase II Plan (developed as part of I-1) 

and finalize for implementation

All sources
Copper Sources in Urban Runoff and Shoreline Activities

71 November 2004

APPENDIX B. Pesticide Calculations

Information in this appendix: 

Table B-1. Bay Area Copper-Containing Pesticide Use Estimate, 2002
Copper Sources in Urban Runoff and Shoreline Activities

72 November 2004

Table B-1. Bay Area Copper-Containing Pesticide Use Estimate, 2002

Pesticide

% 

Cu

2002 

Sales 

(lb A.I.)

2002 

Statewide 

Reported 

Use

(lb A.I.)

Reported 

Ag. Use

(lb A.I.)

Reported 

Boat Use

(lb A.I.)

Reported 

Water

Use

(lb A.I.)

Estimated

Statewide 

Urban Use 

(lb A.I.)

Copper in 

Statewide

Estimated 

Use

(lb Cu/yr)

Estimated 

Bay Area 

Copper 

Use*

(lb Cu/yr)

Copper 100 326,000 45,857 38,661 0 534 286,805 286,805 56,501

Copper 8-quinolinoleate 18 10 0 0 0 10 2 0

Copper Ammonia Complex 100 14,277 5,543 4,580 0 0 9,697 9,697 1,910

Copper Ammonium Carbonate 33 42 30 0 0 12 4 1

Copper Bronze Powder 100 25 0 25 0 0 0 0

Copper Carbonate 57 14,274 7,878 0 0 1,650 6,228 3,550 699

Copper Ethanolamine Complexes, Mixed 100 171,230 17,721 19 0 4,893 166,318 166,318 32,765

Copper Ethylenediamine Complex 100 2,557 0 0 1,101 1,456 1,456 287

Copper Hydroxide 65 3,940,156 2,592,460 2,584,220 0 0 1,355,936 881,358 173,628

Copper Naphthenate 10 380,620 84,476 15 0 0 380,605 38,061 7,498

Copper Oxide (Cupric) 80 127,523 1,313 0 0 126,210 100,968 19,891

Copper Oxide (Cuprous) 89 1,146,625 229,214 213,518 15,032 0 918,075 817,087 160,966

Copper Oxychloride 58 84,997 58,934 58,508 0 0 26,489 15,364 3,027

Copper Oxychloride Sulfate 100 174,700 174,700 0 0 0 0 0

Copper Resinate 9 18,612 18,577 0 0 35 3 1

Copper Soap (Copper Octanoate) 18 250 0.007 0 0 0 250 45 9

Copper Sulfate (Basic) 53 1,455,054 876,722 875,681 0 173 579,200 306,976 60,474

Copper Sulfate (Pentahydrate) 25.5 5,646,324 2,916,477 2,867,412 0 129,280 2,649,632 675,656 133,104

Copper Thiocyanate 52 61 0 52 0 9 5 1

Copper Triethanolamine Complex 100 256 2 0 0 0 256 256 50

TOTAL 3,303,610 650,811

Source: TDC Environmental calculations with data from DPR (DPR, 2004; DPR 2003a; DPR, 2003b).