Aquatic Pesticide Application Plan 

for the 

San Francisco Estuary Invasive Spartina Project 

This plan addresses herbicide application activities undertaken by 

ISP Partner agencies in the effort to eradicate non-native, invasive Spartina 

from the San Francisco Estuary. 

Annual update prepared by 

Drew Kerr 

2612-A 8th Street 

Berkeley, CA 94710 

dwkerr@spartina.org

for the 

State Coastal Conservancy 

1330 Broadway, 13th floor 

Oakland, Ca 94612-2530 

August 2008 

TABLE OF CONTENTS 

1. BACKGROUND ........................................................................................................... 1 

2. STATEMENT OF PURPOSE AND NEED ........................................................... 1

3. DESCRIPTION OF THE WATER BODY SYSTEM........................................... 2

Ecology ................................................................................................................................... 2

Natural Processes Affecting Water Quality............................................................................ 3

Water Quality.......................................................................................................................... 4

Sediment Quality .................................................................................................................... 7

4. DESCRIPTION OF TARGET SPECIES............................................................... 9

Native Pacific Cordgrass (Spartina foliosa) ........................................................................... 9

Atlantic Smooth Cordgrass (Spartina alterniflora) and its Hybrids..................................... 10

English Cordgrass (Spartina anglica)................................................................................... 13

Chilean Cordgrass (Spartina densiflora) .............................................................................. 13

Salt-Meadow Cordgrass (Spartina patens)........................................................................... 14

5. CONTROL TOLERANCES.................................................................................. 14

6. DESCRIPTION OF HERBICIDE ........................................................................ 15

Environmental Fate of Herbicides........................................................................................ 21

Potential Biological and Ecological Effects ......................................................................... 25

Non-Target Aquatic Plants and Algae.............................................................................. 27

Aquatic and Benthic Invertebrates ................................................................................... 28

Fish................................................................................................................................... 29

Birds................................................................................................................................. 31

Mammals.......................................................................................................................... 31

7. DESCRIPTION OF ALTERNATE, NON-CHEMICAL CONTROL 

METHODS............................................................................................................. 32

ISP-selected Non-chemical Control Methods....................................................................... 32

Hand-pulling and manual excavation............................................................................... 32

Mechanical excavation and dredging ............................................................................... 33

Covering/blanketing ......................................................................................................... 34

Other Non-chemical Methods Evaluated.............................................................................. 35

Mowing, burning, pruning, and flaming .......................................................................... 35

Crushing and mechanical smothering .............................................................................. 35

Flooding and draining ...................................................................................................... 36

8. HERBICIDE APPLICATION AREAS FOR 2007.............................................. 37

Site 01 – Alameda Flood Control Channel, Alameda County.............................................. 37

Site 02 – Bair & Greco Island Complex, San Mateo County ............................................... 37

Site 03 – Blackie’s Pasture, Marin County........................................................................... 39
Site 04 – Corte Madera Creek Complex, Marin County....................................................... 39

Site 05 – Coyote Creek & Mowry Slough Area, Santa Clara County .................................. 40

Site 06 – Emeryville Crescent, Alameda County ................................................................. 40

Site 07 – Oro Loma Marsh, Alameda County ...................................................................... 41

Site 08 – Palo Alto Baylands, Santa Clara County............................................................... 41

Site 09 – Pickleweed Park, Marin County............................................................................ 42

Site 10 – Point Pinole Regional Shoreline, Contra Costa County ........................................ 42

Site 11 – Southampton Marsh, Solano County..................................................................... 43

Site 12 – Southeast San Francisco, San Francisco County................................................... 43

Site 13 – Whale’s Tail / Old Alameda Creek Complex, Alameda County........................... 44

Site 15 – South San Francisco Bay Marshes, Santa Clara County ....................................... 45

Site 16 – Cooley Landing, San Mateo County ..................................................................... 45

Site 17 – Alameda Island / San Leandro Bay Complex, Alameda County........................... 46

Site 18 – Colma Creek / San Bruno Marsh Complex, San Mateo County ........................... 46

Site 19 – West San Francisco Bay, San Mateo County ........................................................ 47

Site 20 – San Leandro / Hayward Shoreline Complex, Alameda County ............................ 48

Site 21 – Ideal Marsh, Alameda County............................................................................... 48

Site 22 – Two Points Complex, Alameda County ................................................................ 49

Site 23 – Marin Outliers, Marin County ............................................................................... 49

Site 24 – Petaluma River, Sonoma County........................................................................... 50

Site 26 – North San Pablo Bay, Solano County.................................................................... 50

9. WATER QUALITY MONITORING PLAN ....................................................... 51

Objective............................................................................................................................... 51

Site Selection ........................................................................................................................ 51

Site Descriptions............................................................................................................... 52

Sampling Frequency and Sampling Design.......................................................................... 56

Sampling Procedures........................................................................................................ 56

Sample Analysis............................................................................................................... 57

Data Analysis ................................................................................................................... 57

10. APPLICABLE WATER QUALITY BMPS....................................................... 57

Applicator Calibration Training............................................................................................ 58

11. REFERENCES...................................................................................................... 60

Appendices 

1. Chemical properties, degradation rates, environmental fate, and toxicity of imazapyr, glyphosate, and aquatic surfactants evaluated for Spartina control 

2. 2008 Spartina Control Program Site Maps 

3. General Site Safety & Materials Handling Guidelines and Procedures for Spartina 

Control Projects in the San Francisco Estuary 
List of Figures 

Figure 1: Locations and mean discharges for municipal wastewater treatment 

plants in South San Francisco Bay.....................................................................4 

Figure 2: Conceptual Model of Possible Exposure of Biological Organisms to 

Herbicide Mixture Used by the Spartina Control Program.............................26 

Figure 3: Baywide map of 2008 Spartina Control Program treatment sites ...................38 

List of Tables 

Table 1: Dissolved concentrations of trace metals in water samples...............................7 

Table 2: Total concentrations of trace metals in water samples ......................................7 

Table 3: Ranges of trace pollutants in San Francisco Bay sediments..............................8 

Table 4a: Imazapyr herbicide mixture component concentrations and application 

rates for treatment of non-native Spartina in San Francisco Estuary ..............20 

Table 4b: Glyphosate herbicide mixture component concentrations and application 

rates for treatment of non-native Spartina in San Francisco Estuary ..............20 

Table 5: Summary of water quality monitoring sites for the 2008 season.....................52 

1. BACKGROUND 

The San Francisco Bay Estuary (San Francisco Estuary or Estuary) supports the largest 

and most ecologically important expanses of tidal mudflats and salt marshes in the contiguous western United States. This environment naturally supports a diverse array of native plants and animals. Over the years, many non-native species of plants and animals 

have been introduced to the Estuary, and some now threaten to cause fundamental 

changes in the structure, function, and value of the Estuary's tidal lands. Among these 

threatening invaders are several species of salt marsh cordgrass (genus Spartina). In recent decades, populations of non-native cordgrasses were introduced to the Estuary and 

began to spread rapidly. Though valuable in their native settings, these introduced 

cordgrasses are highly aggressive in this new environment, and frequently become the 

dominant plant species in areas they invade. 

One of the non-native cordgrass species, Atlantic smooth cordgrass (Spartina alterniflora), is rapidly spreading throughout the Estuary, particularly in the South San 

Francisco Bay (South Bay). Atlantic smooth cordgrass and its hybrids (formed when this 

species crosses with the native Pacific cordgrass, S. foliosa) are now threatening the ecological balance of the Estuary. Based on a century of international studies of comparable 

cordgrass invasions, these hybrids are likely to eventually cause the extinction of native 

Pacific cordgrass, choke tidal creeks, dominate newly restored tidal marshes, and displace 

thousands of acres of existing shorebird habitat. Once established in this estuary, invasive 

cordgrasses could rapidly spread to other estuaries along the California coast through 

seed dispersal on the tides. Non-native invasive cordgrasses currently dominate approximately 1,200-1,500 acres of the San Francisco Estuary in seven counties — on State, 

Federal, municipal, and private lands— and are spreading at an alarming rate. 

The California State Coastal Conservancy (Conservancy) initiated the ISP in 2000 to 

stave off the invasion of non-native cordgrass and its potential impacts. The ISP is a regionally coordinated effort of Federal, State, and local agencies, private landowners, and 

other interested parties, with the ultimate goal of arresting and reversing the spread of 

non-native cordgrasses in the San Francisco Estuary. When fully implemented, the ISP 

will provide opportunities to maximize resources, effectively disseminate information, 

facilitate regional monitoring, and reduce the occurrence of cordgrass re-infestation. The 

geographic focus of the ISP includes the nearly 40,000 acres of tidal marsh and 29,000 

acres of tidal flats that comprise the shoreline areas of the nine Bay Area counties, including Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma Counties, and Sacramento County. 

2. STATEMENT OF PURPOSE AND NEED 

The purpose of the Spartina control program is to arrest and reverse the spread of invasive non-native cordgrass species in the San Francisco Estuary to preserve and restore the 

ecological integrity of the Estuary's intertidal habitats and estuarine ecosystem. 

The Spartina control program is needed to prevent further degradation and loss of the 

natural ecological structure and function of the San Francisco Estuary. In the absence of 

any coordinated and wide-ranging control program, within decades one-quarter to oneSan Francisco Estuary Invasive Spartina Project 1. 2008 Aquatic Pesticide Application Plan 
half (up to 10,000 acres) of the existing intertidal flats are likely to be replaced with 

dense, invasive cordgrass marsh, and much of the native diverse salt-marsh vegetation 

replaced with nearly homogeneous stands of non-native cordgrass. This ecological conversion is likely to alter the structure and function of the Estuary, affecting fisheries, migratory shorebirds and waterfowl, marine mammals, endangered fish, wildlife, and 

plants, tidal sediment transport, and the rate, pattern, and magnitude of tidal flows. In addition, invasive cordgrasses may impede or preclude plans to restore up to 20,000 acres 

of diked baylands to native tidal marsh. Arresting and reversing the invasion of nonnative cordgrasses may not be feasible once these species have spread and become established, due to the expansive scale of the invasion and the effects of hybridization. To 

avoid these consequences, the ISP is implementing a regionally coordinated, long-term 

management program. 

3. DESCRIPTION OF THE WATER BODY SYSTEM 

Ecology 

Like most Pacific estuaries, the majority of the intertidal zone of the San Francisco Estuary naturally consists of unvegetated tidal flats, or mudflats. Native California tidal marsh 

vegetation is limited to the upper intertidal zones, above mean sea level in San Francisco 

and San Pablo Bays. Below mean sea level, waves erode and redeposit the upper layers 

of bay mud with each tidal cycle. Rich deposits of fine silt and clay from the SacramentoSan Joaquin Delta have accumulated in the Estuary to form highly productive mudflats, 

with abundant benthic invertebrates. The mudflats provide a critical source of nutrition 

and energy for migratory shorebirds and waterfowl, with more than one million shorebirds using the Estuary's mudflats and salt ponds during migration, and over half of the 

west-coast migratory diving ducks making this estuary their winter home. 

At elevations above the intertidal zone (in areas that have not been diked and removed 

from tidal action), are the Estuary's tidal salt and brackish marshes. Pacific salt marsh 

vegetation is more diverse in plant species than its Atlantic counterparts. Until recent 

decades, the native Pacific cordgrass exclusively occupied the lower reaches of the Estuary's tidal salt marshes. At slightly higher elevations, a relatively flat tidal marsh plain 

(reaching near the average level of the higher daily tides), is dominated by low-growing, 

mostly perennial plants such as pickleweed, saltgrass, and other salt-tolerant herbs. The 

tidal marsh plain is punctuated by salty shallow ponds (pans), and dissected by irregular 

tidal creeks. Above the tidal marsh plain, at the uppermost edges of the marsh, are an 

even greater number of plant species. 

Many endemic (unique to the area) plant and animal species, including many rare or endangered species, survive only in the Estuary's remaining tidal marshes. They remain at 

risk of extinction because of the severe decline over the past century in the abundance, 

distribution, and quality of tidal marshes. Most of the Estuary's rare species have narrow 

or specific habitat requirements, and the health of their populations usually is sensitive to 

structural changes in their habitats - particularly the condition of the marsh vegetation. 

Strong dominance of the vegetation by one or more plant species necessarily results in 

lower overall species diversity, and can push rarer species to local extinction. 

San Francisco Estuary Invasive Spartina Project 2. 2008 Aquatic Pesticide Application Plan 
Natural Processes Affecting Water Quality 

Water quality within the San Francisco Estuary is connected to and affected by complex 

regional and local natural processes. Hydrologic relationships between the Pacific Ocean, 

the Estuary, and the many freshwater tributaries (including the Sacramento-San Joaquin 

River system) govern salinity levels in different portions of the Estuary and along the Bay 

margins. Variable natural factors such as tidal cycles, local winds, basin bathymetry, and 

salinity gradients interact with river flows and affect the circulation of Estuary waters 

through channels, Estuary margins, and bays, distributing nutrients, salt concentrations, 

and pollutants. Major processes affecting water quality are described below. 

Tidal Cycles. The Estuary has two low tides and two high tides every 24.8 hours. During 

each tidal cycle, an average of about 1.3 million acre-feet of water, or 24 percent of the 

Bay and Delta’s volume, moves in and out of the Golden Gate. On the flood (incoming) 

tide, ocean water moves through the Golden Gate and into the Estuary’s southern and 

northern reaches, raising the water level at the end of the South Bay by more than eight 

feet, and raising the height of the Sacramento River at the upstream edge of the Estuary 

by about three feet. It takes about two hours for the flood tide to reach the end of the 

South Bay and eight hours to reach Sacramento. 

Subregional Conditions. Suisun and North Bay subregions receive the majority of 

freshwater input from the Sacramento and San Joaquin River system. In the open bays, 

density-driven currents show ebb dominance of the surface water and flood dominance of 

the bottom water. Waters in these embayments are well oxygenated, with low- to moderate-salinity and high-suspended solids concentrations. Water residence time affects the 

abundance and distribution of many estuarine organisms, the amount of primary production by phytoplankton, and some of the chemical and physical processes that influence 

the distribution and fate of pollutants. During low flow periods of the year (late summer), 

the residence time of freshwater moving from the Delta to the ocean can be relatively 

long (on the order of months) compared to periods when outflow is very high (winter), 

when freshwater can move from the Delta to the ocean in days. 

The Central Bay subregion is influenced by ocean waters that are cold, saline, and lower 

in total suspended sediment. Water quality parameters fluctuate less than in other sectors 

of the Bay due to the predominance of ocean water. Net exchanges of ocean and Bay waters depend on freshwater flow in the Bay, tidal amplitude, and longshore coastal currents. 

The southern part of San Francisco Bay receives less than 10 percent of the natural 

freshwater flow into the Bay, but the majority (>75 percent) of wastewater discharges. 

The largest flow is from San Jose, where approximately 120 million gallons per day 

(MGD) of treated wastewater are released into Artesian Slough, a tributary to Coyote 

Creek (Figure 1). This fresh water flow creates a local zone of brackish water in the otherwise saline tip if the South Bay. The rest of the South Bay, because it has so little 

freshwater input, is essentially a tidal lagoon with a relatively constant salinity (approximately the same as ocean water, 32 parts per thousand, ppt). South Bay waters are influenced by Delta outflow only during the winter months, when low-salinity water moves 

southward into the southern reach displacing the saline, denser water northward. In the 

summer months, however, South Bay currents are largely influenced by wind stress on 

San Francisco Estuary Invasive Spartina Project 3. 2008 Aquatic Pesticide Application Plan 
the surface; northwest winds transport water 

in the direction of the wind, and the displaced water causes subsurface currents to 

flow in the opposite direction. 

Currents and Circulation. Circulation patterns within the Bay are influenced by Delta 

inflows, gravitational currents, and tide- and 

wind-induced horizontal circulation. The 

cumulative effects of the latter three factors 

on net circulation within embayments tend to 

dominate over that of freshwater inflows except during short periods after large storm 

events (Smith 1987). Exchanges between 

embayments are influenced both by mixing 

patterns within embayments and by the magnitude of freshwater inflows (Smith 1987). 

Currents created by tides, freshwater inflows, 

and winds cause erosion and transport of 

sediments. Tidal currents are usually the 

dominant form of observed currents in the 

Bay. Tidal currents are stronger in the channels and weaker in the shallows (Cheng and 

Gartner 1984). These processes enhance exchange between shallows and channels during the tidal cycle, and contribute significantly to landward mixing of ocean water and 

seaward mixing of river water. Also, the South Bay begins flooding while San Pablo Bay 

is still ebbing, making it possible for the South Bay to receive water from the northern 

reach (Smith 1987). 

Figure 1. Locations and mean discharges for municipal 

wastewater treatment plants in South San Francisco 

Bay. Adapted from Schemel et al. 1999, based on Davis 

et al. 1991. 

Tides have a significant influence on sediment resuspension during the more energetic 

spring tide when sediment concentrations naturally increase, and particularly during the 

ebbs preceding lower low water when the current speeds are highest. Powell et al. (1989), 

however, observed no correlation between tidal cycle and suspended sediment loads or 

distribution in the South Bay. Their conclusion was that winds are the most important 

factor in resuspending sediments in the South Bay, and that sources of sediments are 

more important than transport of sediment resuspended from other parts of the Bay 

(Reilly et al. 1992). 

Wind-induced currents have a significant effect on sediment transport by resuspending 

sediments in shallow waters (Krone 1979; Cloern et al. 1989). An estimated 100 to 286 

million cubic yards of sediments are resuspended annually from shallow areas of the Bay 

by wind-generated waves (Krone 1974; SFEP 1992b). 

Water Quality 

Water quality in the San Francisco Estuary has improved significantly since the enactment of the California Water Quality Control Act (Porter-Cologne) in 1969 and the Clean 

Water Act in 1972. Nevertheless, the Estuary waters still carry significant loads of pollutants from human sources. Under Section 303(d) of the Clean Water Act, states were reSan Francisco Estuary Invasive Spartina Project 4. 2008 Aquatic Pesticide Application Plan 
quired to develop a list of water bodies that do not meet water quality standards; this list is 

referred to as the “303(d) list.” This list defines low, medium, and high priority pollutants 

that require immediate attention by State and Federal agencies. Portions of the Estuary have 

high-priority 303(d) listings for a number of pollutants, including dioxin compounds, furan 

compounds, PCBs, mercury, copper, nickel, and exotic (plant and animal) species. 

The most comprehensive information describing water quality in the Estuary comes from 

the Regional Monitoring Program managed by the San Francisco Estuary Institute (SFEI) 

and ongoing studies by the Interagency Ecological Program (IEP). In addition, numerous 

short-term studies that focus on specific sites, resources, or pollutants are conducted on a 

regular basis by researchers and entities conducting permit-specified monitoring of waste 

discharges. The primary water quality parameters discussed below are: temperature, salinity, dissolved oxygen (DO), pH, total suspended solids (TSS), turbidity, and pollutants. 

Temperature. Water temperatures in the Estuary range from approximately 10 ̊C to 22 ̊C 

(50 ̊F to 71.6 ̊F). Temperatures are influenced by seasonal solar cycles and variable inputs of river and coastal ocean waters. Temperatures are typically at the higher end of this 

range along the Estuary margin during daylight hours as the influence of solar energy 

warms the water. 

Salinity. The salinity of the Estuary varies spatially and temporally. Along the northern 

reach the salinity increases from the Delta to the Central Bay. At the mouth of the Sacramento River, for example, the mean annual salinity averages slightly less than 2 ppt; in 

Suisun Bay it averages about 7 ppt; and at the Presidio in Central Bay it averages about 30 

ppt. In the South Bay, salinities remain at near-ocean concentrations (32 ppt) during much 

of the year, except in the vicinity of the San Jose wastewater outfall at Artesian Slough, 

where salinities are less concentrated. During summer months in dry years, high evaporation rates may cause salinity in South Bay to exceed that of ocean water. 

Seasonal changes in the salinity distribution within the Estuary are controlled mainly by 

the exchange of ocean and Estuary water, and by river inflow. River inflow has the 

greater influence on salinity distribution throughout most of the Estuary because inflow 

varies widely, while variations in ocean inputs are relatively small. In winter, high flows 

of freshwater from the Delta lower the salinity throughout the Estuary’s northern reach. 

High Delta flows also intrude into South Bay, lowering salinity there for extended periods. In contrast, during the summer, when freshwater inflow is low, saline water from the 

Bay intrudes into the Delta. The inland limit of salinity intrusion varies greatly from year 

to year. In addition, channel dredging can increase gravitational circulation and enhance 

salinity intrusion (Nichols and Pamatmat 1988). 

Dissolved Oxygen. Oxygen concentrations in estuarine waters are increased by the mixing 

action of wind, waves, and tides; photosynthesis of phytoplankton and other aquatic plants; 

and high DO in freshwater inflow. DO concentrations are lowered by plant and animal respiration, chemical oxidation, and bacterial decomposition of organic matter. 

The Estuary’s waters are generally well oxygenated, except during summer in the extreme southern end of the South Bay where concentrations are reduced by poor tidal mixing and high water temperature. Typical concentrations of DO range from 9 to 10 milligrams per liter (mg/l) throughout the Estuary during periods of high river flow, 7 to 9 

mg/l during moderate river flow, and 6 to 9 mg/l during the late summer months when 

flows are the lowest. Unlike the 1950s and 1960s, when inadequately treated sewage and 

San Francisco Estuary Invasive Spartina Project 5. 2008 Aquatic Pesticide Application Plan 
processing plant wastes depleted oxygen in parts of the Bay and Delta, today there are 

few reports of places in the Estuary where low oxygen concentrations adversely affect 

beneficial uses. Today, the lowest concentrations in the Estuary are typically observed in 

the extreme South Bay but, in some instances, DO levels in semi-enclosed embayments 

such as Richardson Bay can be much lower than in the main water body (SFEI 1994). 

pH. The pH of the water in San Francisco Bay is relatively constant and typically ranges 

from 7.8 to 8.21

. 

Total Suspended Solids (TSS) and Turbidity. Turbidity and TSS are generally used as 

measures of the quantity of suspended particles. The distinction between the two terms 

lies mainly in the method of measurement. In general, higher TSS results in more turbid 

water. 

Regions of maximum suspended solids occur in the North Bay in the null zone2 (generally 50 to 200 mg/l, but as high as 600 mg/l TSS). The specific location of the null zone 

changes depending upon freshwater discharge from the Delta. TSS levels in the Estuary 

vary greatly depending on the season, ranging from 200 mg/l in the winter to 50 mg/l in 

the summer (Nichols and Pamatmat 1988; Buchanan and Schoellhamer 1995). TSS also 

varies with tidal stage and depth (Buchanan and Schoellhamer 1995). Shallow areas and 

channels adjacent to shallow areas have the highest suspended sediment concentrations. 

The Central Bay generally has the lowest TSS concentrations; however, wind-driven 

wave action and tidal currents, as well as dredged material disposal and sand mining operations cause elevations in suspended solids concentrations throughout the water column. 

Pollutants. Pollutant loading to San Francisco Bay has long been recognized as one of 

many factors that has historically stressed aquatic resources. Pollutants enter the aquatic 

system through atmospheric deposition, runoff from agricultural and urbanized land, and 

direct discharge of waste to sewers and from industrial activity. 

The Bay’s sediment can be both a source and a sink for pollutants in the overlying water 

column. The overall influx of pollutants from the surrounding land and waste discharges 

can cause increases in sediment pollutant levels. Natural resuspension processes, biological processes, other mechanical disturbances, dredging, and sediment disposal can remobilize particulate-bound pollutants. 

Metals. Ten trace metals in the aquatic system and in waste discharged to the Bay are 

monitored on a regular basis. Total and dissolved fractions are sampled three times a year 

at Regional Monitoring Program (RMP) stations throughout the Estuary. Tables 1 and 2 present dissolved and total trace metal concentration ranges in Bay waters during 1998 (SFEI 

1998). 

Organic Pollutants. Three general types of trace organic contaminants, polycylic aromatic 

hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pesticides, are measured in 

San Francisco Bay water on a regular basis. 

 

1 Water or solutions that are acidic have a pH of less than 7.0, and basic or alkaline water have a pH greater than 7.0. A pH of 7.0 is considered neutral. 

2 The null zone is area or region of an estuary where the bottom, high-density and surface, low-density currents have equal and opposite 

effects. It is defined as the zone where the mean near-bottom speed is zero. The actual location of the null zone migrates in response to 

changes in river discharge. It is important because it is typically characterized by high concentrations of suspended particulate matter and 

rapid sediment accumulation. 

San Francisco Estuary Invasive Spartina Project 6. 2008 Aquatic Pesticide Application Plan 
Water column concentrations of dissolved and total PAHs in 1998 ranged from 2.1 to 46 

parts per trillion (pptr) and from 20 to 300 pptr, respectively (SFEI 1998). Total PCB 

concentrations in Bay waters during 1998 ranged from 70 to 7,000 parts per quadrillion 

(ppq), and were below the U.S. Environmental Protection Agency (U.S. EPA) 4-day 

(chronic toxicity) water quality criteria (30 pptr) (SFEI 1998). Dissolved PCB concentrations ranged from 12 to 930 ppq. Bay waters also contained measurable concentrations of 

chlorinated pesticides, including chlordanes and DDTs. Total chlordane concentrations 

ranged from 21 to 5,700 ppq, while total DDT concentrations ranged from 190 to 9,900 

ppq (SFEI 1998). 

A recent review of historical data from several sources found several previously unidentified 

organic contaminants in the San Francisco Estuary (SFEI 2002). In this study, p-nonylphenol, 

a common constituent in detergents and other household products, agricultural surfactants, 

and many industrial products, was identified in Sacramento and San Joaquin River water (at 

19 ng/L and 5 ng/L, respectively), but it was not detected in Estuary water. 

Sediment Quality 

Sediment quality in the Estuary varies greatly according to the physical characteristics of 

the sediment, proximity to historical waste discharges, the physical and chemical condition of the sediment, and sediment dynamics that change with location and season. Generally, the level of sediment contamination at a given location will vary depending on the 

rate of sediment deposition, which varies with seasons and tides (Luoma et al. 1990). 

Chemical contaminant dynamics in an estuary are closely associated with the behavior of 

suspended and deposited sediments. The physical and chemical characteristics of sediTable 1. Dissolved Concentrations of Trace Metals in Water Samples (SFEI 1998) 

Ag 

μg/L 

As 

μg/L 

Cd 

μg/L 

Cr 

μg/L 

Cu 

μg/L 

Hg 

μg/L 

Ni 

μg/L 

Pb 

μg/L 

Se 

μg/L 

Zn 

μg/L 

Minimum 0.0002 0.83 0.003 0.09 0.37 0.0003 0.56 0.002 ND 0.07 

Maximum 0.006 4.8 0.09 3.8 3.5 0.015 7.2 0.40 6.1 22.5 

WQ Criteria 

1-hour 

1.9 69 42 1100 5 74 210 90 

WQ Criteria 

4-day

 36 9.3 50 3.1 8.2 8.1 81 

ND – Not detectable at laboratory limits 

Table 2. Total Concentrations of Trace Metals in Water Samples (SFEI 1998) 

Ag 

μg/L 

As 

μg/L 

Cd 

μg/L 

Cr 

μg/L 

Cu 

μg/L 

Hg 

μg/L 

Ni 

μg/L 

Pb 

μg/L 

Se 

μg/L 

Zn 

μg/L 

Minimum 0.002 ND 0.009 0.29 0.42 0.0006 0.63 0.05 ND 0.77 

Maximum 0.20 9.4 0.36 101 20 0.73 49.0 15.8 6.8 98.6 

WQ Criteria 

1-hour 

2.3 69 43 1100 2.1 140 58 

WQ Criteria 

4-day 

 36 9.3 50 0.025 7.1 5.6 

ND – Not detectable at laboratory limits

San Francisco Estuary Invasive Spartina Project 7. 2008 Aquatic Pesticide Application Plan 
ments, and the bioavailability and toxicity of sediment-associated chemicals to aquatic 

organisms, are particularly important in determining their potential impact on environmental quality. 

While pollutant loading to the Estuary from point and non-point sources has declined 

dramatically over the past two decades, and surface sediment contamination may be declining from historical highs, Bay sediments are still an important source and sink of pollutants. Much of the data documenting concentrations of trace metals and organics in Bay 

sediments are found in the historical summary of Long and Markel (1992) and in the 

more recent monitoring efforts by the State’s Bay Protection and Toxic Cleanup Program 

(BPTCP) (SFBRWQCB 1994) and Regional Monitoring Program (SFEI 1994 and 1998). 

Concentrations of Metals and Organic Pollutants in Sediments. Mean concentrations of 

trace metals and organics in sediments vary according to grain size, organic carbon content, and seasonal changes associated with riverine flow, flushing, sediment dynamics, 

and anthropogenic inputs. Anthropogenic inputs appear to have the greatest effect on 

sediment levels of copper, silver, cadmium, and zinc, as well as several chlorinated and 

petroleum hydrocarbons (SFBRWQCB 1994). Ranges in sediment metals and trace organic concentrations during 1998 are listed in Table 3. The table also compares measured 

concentrations to effects range-low (ER-L) and effects range-median (ER-M) values, 

which are levels that are rarely associated with adverse effects to benthic organisms from 

exposures to sediment-associated contaminants and levels that are frequently associated 

with adverse impacts, respectively (Long et al., 1995). For most pollutants, ranges in 

measured concentrations exceed the respective ER-L values but are below the correTable 3. Ranges of Trace Pollutants in San Francisco Bay Sediments (SFEI 1998)

SEDIMENT SAMPLES (MG/KG) EFFECTS LEVELS (MG/KG) 

Minimum Maximum ER-L ER-M 

Arsenic 3.1 19 8.2 70 

Cadmium 0.1 2.1 1.2 9.6 

Chromium 63 216 81 370 

Copper 8.5 76 34 270 

Lead 5.4 65 46.7 218 

Mercury 0.03 0.82 0.15 0.71 

Nickel 68 228 20.9 51.6 

Selenium 0.06 0.52 

Silver ND 2.0 1.0 3.7 

Zinc 64 256 150 410 

TOTAL PAHS 0.033 6.30 4.022 44.792 

Total PCBs ND 0.26 0.0227 0.18 

Total DDTs No Data 0.00158 0.0461 

Total Chlordanes ND 0.0099 0.0005 0.006 

Key: Concentrations bolded exceed the Lowest Observable Effects Level (ER-L) 

 Concentrations bolded and underlined exceed the Median Observable Effects Level (ER-M) 

 ND – Not detectable at laboratory limits

San Francisco Estuary Invasive Spartina Project 8. 2008 Aquatic Pesticide Application Plan 
sponding ER-M values. The exceptions are mercury, nickel, total PCBs, and total chlordanes, which exceed the ER-M values at one or more locations in the Bay. Some sites 

within San Francisco Bay, such as Lauritzen Canal, the Port of Oakland near San Leandro Bay, and Richmond Harbor, which have been greatly affected by historical contamination, contain sediment pollutant levels which are considerably higher than those measured by the Regional Monitoring Program. 

4. DESCRIPTION OF TARGET SPECIES 

There are one native and four non-native species of cordgrass in the San Francisco Estuary. The native species is Pacific cordgrass (S. foliosa), which is not a target of the ISP’s 

control efforts, and is actually the recipient of conservation by controlling the invasive 

species). The non-native species are Atlantic smooth cordgrass (S. alterniflora), English 

cordgrass (S. anglica), Chilean cordgrass (S. densiflora), and salt-meadow cordgrass (S. 

patens). The non-native Atlantic smooth cordgrass hybridizes with the native Pacific 

cordgrass, and their offspring (referred to in this APAP as "Atlantic smooth cordgrass 

hybrids" or "hybrids") are highly invasive and considered non-native. Key aspects of the 

cordgrass species found in the Estuary are contrasted below. The biological contrasts 

among these species and their roles in their native habitats help to demonstrate how nonnative cordgrasses are likely to alter the Estuary's salt marsh ecosystem. First described is 

the native Pacific cordgrass, followed by the non-native species. 

Native Pacific Cordgrass (Spartina foliosa) 

The historic range of Pacific cordgrass was confined to estuaries from Point Reyes to 

Baja California, with large gaps in between; for example, it is historically absent in Monterey Bay and Morro Bay. Most of the Pacific cordgrass population exists in San Francisco and San Pablo Bays. Its northern limit is now Bodega Bay, a small and recent natural population. It even more recently established in Tomales Bay, where its population 

surged following major flood and depositional events of the mid-1990s. Pacific cordgrass 

is a perennial, salt-tolerant marsh grass, which spreads both sexually, by seed dispersal, 

and asexually, by long, creeping rhizomes (underground stems, or runners) that propagate 

small clusters of leafy shoots. Clonal (asexual) growth of rhizomes allows individual 

plants to form extensive colonies without being pollinated by another plant. A colony 

thus formed is referred to as a "clone." The slender leafy shoots with seed-heads seldom 

exceed five feet in height, and most shoots range from about one to three feet tall. The 

height of the cordgrass plant is related to how well it tolerates submersion in tidewaters, 

and thus how low in the intertidal zone it can grow. The relatively short stature of Pacific 

cordgrass corresponds with its limited occupation of lower elevations within the intertidal 

zone. 

Pacific cordgrass is genetically very similar to Atlantic smooth cordgrass, but the two 

species also have significant differences. In size, growth rate, production, and ecological 

tolerances, Pacific cordgrass is much less robust than Atlantic smooth cordgrass (Smart 

and Barko 1978, Callaway 1990, Boyer, Callaway and Zedler 2000). Pacific cordgrass 

grows more luxuriantly in clayey mud than sand, but it naturally grows in substrates 

ranging from sand and mud to peat. Its leaves and stems wither in fall and are shed in winter, as the clones die back to young shoots and buds near the mud surface. The sparse remains of Pacific cordgrass stands in winter are relatively ineffective in trapping sediment. 

San Francisco Estuary Invasive Spartina Project 9. 2008 Aquatic Pesticide Application Plan 
Pacific cordgrass is generally restricted to a narrow portion of the intertidal zone, between an elevation just above mean sea level and an elevation near the level of the average higher daily tide (mean higher high water, "MHHW"). It tends to fail in competition 

with plants like pickleweed on the marsh plain, which, in California estuaries, approaches 

the elevation of the MHHW. This modest range in tidal elevation restricts Pacific 

cordgrass to the sloping banks of tidal creeks, and the gently sloping upper edges of mudflats where sediment accumulates. This leaves the vast acreages of Pacific tidal flats below mean sea level entirely free of emergent vegetation in natural historic conditions. The 

vegetated marsh plain (middle to high marsh zone) supports either sparse Pacific 

cordgrass in lower areas, or none at all. 

Early experiments with Pacific cordgrass demonstrated that its slender, widely spaced 

leafy shoots and rhizomes are not as effective at stabilizing sediment compared with Atlantic smooth cordgrass, especially under exposed conditions at the bay's edge (Newcombe et al. 1979). Seedlings of Pacific cordgrass are seldom found in established 

marshes, and appear only intermittently in sheltered upper mudflats. 

Pacific cordgrass is particularly valued as habitat for the endangered California clapper 

rail, which spends most of its time foraging for food within, or close to, the protective 

canopy of cordgrass. Rails can move within Pacific cordgrass stands, and spend most of 

their time under cover of the cordgrass foliar canopy, usually selecting prey items such as 

invertebrates inhabiting the cordgrass stands and their edges. In contrast to the clapper 

rail of southern California tidal marshes, San Francisco Bay clapper rails generally do not 

construct "floating nests" in Pacific cordgrass; instead, they tend to build nests in gumplants or pickleweed in the higher marsh. 

Atlantic Smooth Cordgrass (Spartina alterniflora) and its Hybrids 

Smooth cordgrass is the closely related sibling to Pacific cordgrass. In the United States, 

it occurs along both the Atlantic and Gulf Coasts (Gleason and Cronquist 1991). It is 

unique among the world's cordgrass species in terms of its growth potential and ecological breadth, and it is the parent species of the other most invasive cordgrass species of 

hybrid origin, English cordgrass (S. anglica; Adam 1990). The San Francisco Estuary 

population of Atlantic smooth cordgrass was founded by seed from Maryland in the mid1970s, introduced experimentally for one of the first tidal marsh restoration projects on 

the west coast. We refer to the San Francisco Bay population of smooth cordgrass as Atlantic smooth cordgrass. 

Atlantic smooth cordgrass is a coarse perennial grass that, like its Pacific relative, spreads 

both by seed dispersal and by creeping rhizomes that form extensive clonal colonies. In 

parts of the San Francisco Estuary, the rate of lateral spread by rhizomes averages between 3.3 and 6.6 feet per year, in contrast with native Pacific cordgrass, which spreads 

only 0.6 to 2.4 feet per year in the same marshes (Josselyn et al. 1993). Similar rates of 

lateral spread of this species and its hybrids have been recorded more recently in 

Cogswell Marsh on the Hayward Shoreline (K. Zaremba, M. Taylor, pers. comm.) 

The size range of Atlantic smooth cordgrass is wide and highly variable, depending on its 

local genetics and environment. In nutrient-rich, well-drained marsh sediment, such as 

along tidal creek banks and on newly colonized tidal flats, extensive dense stands can exceed 10 feet in height. On poorly drained marsh flats, its vegetation is typically sparse 

and short, but its dense root and rhizome network maintains pure stands and effectively 

San Francisco Estuary Invasive Spartina Project 10. 2008 Aquatic Pesticide Application Plan 
binds marsh sediments. The "tall form" and "short form" of this species were so strikingly 

different that they were long assumed to be distinct varieties, rather than variations based 

on local environmental conditions. Modern research indicates that factors related to 

marsh drainage, such as waterlogged soil chemistry (especially accumulation of toxic soil 

sulfides), excessive salinity, and nutrient deficiency interact to cause the dramatic differences in growth-forms of Atlantic smooth cordgrass (Bradley and Dunn 1989, Mendelssohn and Seneca 1980, Valiela et al. 1978, Smart and Barko 1978). Genetic variations in 

height forms of Atlantic smooth cordgrass also has been defined in San Francisco Bay 

(Daehler et al. 1999) 

In the salt marshes of the Atlantic coastal plain, Atlantic smooth cordgrass is dominant 

over most of the intertidal zone. Depending on local tidal range, it can grow to and below 

mean low water (McKee and Patrick 1988), and it can occupy, and even dominate, the 

marsh plain and the low marsh. Vast, homogeneous stands of Atlantic smooth cordgrass 

are the characteristic signature of the Atlantic region's tidal marshes (Dame et al. 2000, 

Adam 1990, Chapman 1964, 1977). 

In contrast with Pacific cordgrass, Atlantic smooth cordgrass freely establishes in relatively exposed shorelines with significant wave action, including estuarine sand beaches. 

It is planted in its native range to stabilize shorelines and to trap and accumulate sediments, and the high density of its tall stems is highly effective at reducing estuarine wave 

energy (Gleason et al. 1979, Knutson and Woodhouse 1988, Knutson et al. 1990) 

In other environmental tolerances, Atlantic smooth cordgrass is also highly resilient. It 

can survive in salinity over 45 parts per thousand (well above ocean salinity), and grow 

luxuriantly in dilute brackish water. If buried, it can regenerate from up to about one foot 

of burial by deposited sediment. Atlantic smooth cordgrass, like other low marsh species, 

can supply air to its roots in oxygen-poor waterlogged mud, using porous air-filled chambers linking its foliage to roots and rhizomes. Atlantic smooth cordgrass can also tolerate 

the severe waterlogging and hypersalinity that develops in poorly drained depressions in 

the salt marsh, including salt marsh pans. Salt marsh pans are frequent and welldeveloped features of historic San Francisco Estuary marshes, and important habitat for 

migratory waterbirds (Goals Project 1999). Along the Hayward shoreline of San Francisco Bay, Atlantic smooth cordgrass has colonized many pre-existing pans, converting 

them to solid cordgrass marsh. 

In the San Francisco Estuary, Atlantic smooth cordgrass has displayed many of the ecological traits typical of its performance in its native salt marsh habitat, and some highly 

novel phenomena as well. Most colonies in the San Francisco Estuary are young, often 

forming nearly circular, discrete, expanding colonies, which merge into irregular patterns, 

resembling mold colonies in a petri dish. The edges of the colonies are tall and robust, 

while the centers often exhibit early symptoms of dieback or "short form" growth habits. 

The "donut" shape of colonies, in fact, is one of the species' signatures for identification 

in aerial photographs of San Francisco Bay. This trait is not typical of mature Atlantic 

salt marshes. In the mild Pacific winters, Atlantic smooth cordgrass shoots tend to retain 

green leaves and persistent dead leaves through much of the winter. This is an important 

contrast with native Pacific cordgrass: combined with the invader's much greater stem size 

and shoot density, year-round dense foliage gives Atlantic smooth cordgrass exceptionally 

high potential to accumulate and trap estuarine sediment during winter storms or floods. 

San Francisco Estuary Invasive Spartina Project 11. 2008 Aquatic Pesticide Application Plan 
The San Francisco population of Atlantic smooth cordgrass has generated some unusual 

growth forms with strikingly atypical appearance. The dwarf form develops a profusion 

of short lateral shoots instead of a tall main stem, forming pure stands with complete 

ground cover of dense, low turf-like ankle-high vegetation on the marsh plain. The 

growth rate of the dwarf form is, however, vigorous. The dwarf form is genetic, not environmentally, induced; it occurs in the same local environments that support luxuriant, tall 

stands of Atlantic smooth cordgrass, often contiguous with the dwarf patches. It has established at multiple locations in San Francisco Bay (Daehler et al. 1999). A comparable 

dwarf form of its hybrid daughter species, English cordgrass, independently evolved in 

Britain and New Zealand (Bascand 1970). 

Hybridization of Atlantic smooth cordgrass with native Pacific cordgrass. Perhaps the 

most novel and significant phenomenon of the San Francisco population of Atlantic 

smooth cordgrass is the rapid evolution of an aggressively expanding hybrid swarm 

formed by cross pollination with the native Pacific cordgrass (Daehler and Strong 1997). 

The hybrid swarm includes first-generation crosses between Atlantic smooth cordgrass 

and Pacific cordgrass with both species acting as pollen-parents and seed parents. Because the two species' pollination periods overlap little, first-generation crosses are infrequent. Hybrids, however, have a wide range of flowering times, and act as an effective 

reproductive bridge between the species. The hybrids produce pollen in much greater 

abundance (21 times greater) and with higher fertility than the native Pacific cordgrass. 

Superior hybrid pollen production and fertility so overwhelm populations of Pacific 

cordgrass ("pollen swamping") that native stands of cordgrass produce mostly hybrid 

back-cross seeds in the presence of flowering hybrid colonies, and fail to reproduce the 

species sexually (Ayres et al. 1999, Antilla et al. 2000). This process alone, called hybrid 

assimilation, can result in the extinction of the invaded species (Levin et al. 1996, Rhymer and Simberloff 1996). 

Genetic analysis has revealed that numerous large populations of presumed Atlantic 

smooth cordgrass in the Estuary are predominantly hybrids and back-crosses (introgressants). The ecologically invasive, dominant traits of Atlantic smooth cordgrass appear to 

be prevalent in the hybrid swarm. "Pure" Atlantic smooth cordgrass is now a minority in 

most of the rapidly evolving hybrid swarms, and trends suggest that hybrids will eventually replace both parent species, as the hybrid-origin species English cordgrass did in 

Britain (see English Cordgrass, below). This recently discovered threat of genetic extinction to a native cordgrass from an alien cordgrass invasion is unique to the San Francisco 

Estuary. No native cordgrasses existed where Atlantic smooth cordgrass invaded Washington and Oregon estuaries, and the cordgrasses native to Europe are genetically isolated 

from their hybrids. 

Atlantic smooth cordgrass, and its hybrids with similar appearance and behavior, are now 

widely distributed in the Central and South Bay, but they have not yet been detected in 

the North Bay or Suisun, despite intensive searches. The northern limit of its distribution 

in 2005 on the east bay is the bay on the western shore of Point Pinole (Giant Marsh), and 

on the west bay is a clone north of Miller Creek mouth (north of China Camp). The 

abundance of Atlantic smooth cordgrass and hybrids remains greatest near the point of its 

original introduction circa 1977 (Pond 3, Hayward Shoreline, Alameda County), and sites 

of early transplanting (Colma Creek, San Mateo County), early pioneer colonies (Oakland, San Leandro Bay, Hayward Shoreline), and areas of subsequent transplanting 

San Francisco Estuary Invasive Spartina Project 12. 2008 Aquatic Pesticide Application Plan 
(Cogswell Marsh, Hayward). It now is nearly the exclusive marsh plant species of recently formed or restored tidal marshes along the San Leandro-Hayward shoreline, and 

this trend is expected to increase. Even as the Bay edge salt marshes and levees are eroding landward through wave action, Atlantic smooth cordgrass marsh is spreading in the 

opposite direction below the wave-cut marsh cliff. Its distribution becomes patchier south 

of the Dumbarton Bridge, decreasing in size and frequency to Alviso, where it is still 

relatively rare. It is well established as scattered, large but discrete colonies in the Dumbarton-Mowry Marsh, Newark, mostly in sloughs and disturbed marsh, or recently colonized mudflats. It is a common or dominant feature in marshes from San Bruno, the San 

Francisco Airport, south to Foster City, and is scattered in variable frequency along the 

Redwood City shoreline. The Napa-Sonoma and Petaluma Marshes are currently free 

from the Atlantic smooth cordgrass invasion, but young colonies have recently been detected in Bolinas Lagoon and Drakes Estero on the Point Reyes peninsula (K. Zaremba, 

pers. comm. 2005). 

English Cordgrass (Spartina anglica) 

English cordgrass is an aggressive invader of mudflats and salt marshes in Britain, New 

Zealand, Australia, and the Pacific Northwest, and thrives in cool temperate climates. It 

originated in Britain as a fertile hybrid derived from introduced Atlantic smooth 

cordgrass and common cordgrass (S. maritima), a small, slow-growing creeping 

cordgrass native to European coasts, now greatly reduced in abundance. Within a century 

after its origin, English cordgrass became the dominant salt marsh grass in Britain (Lee 

and Partridge 1983, Gray et al. 1990). It is shorter than Atlantic smooth cordgrass and 

more grayish in appearance, but partly shares other traits of its parent, such as vigorously 

spreading rhizomes, ability to transform mudflats into vast stands of low marsh vegetation, and ability to dominate and displace associated plant species. It was introduced to 

the San Francisco Estuary at Creekside Park, Corte Madera, Marin County, along with 

Chilean cordgrass, in 1976. Unlike Atlantic smooth cordgrass and Chilean cordgrass, this 

species failed (so far) to disperse from its point of introduction. It may be at or near its 

southern climatic limit on the Pacific Coast in San Francisco Estuary. 

Chilean Cordgrass (Spartina densiflora) 

Chilean cordgrass (also called dense-flowered cordgrass) is a distinctive cordgrass species native to South America. It has a bunchgrass growth habit, forming tight clumps or 

tussocks with short creeping rhizomes, and narrow, firm, in-rolled leaves (Spicher 1984), 

resembling European beachgrass (Ammophila arenaria). It is generally restricted to the 

middle marsh plain and high marsh zones where pickleweed, saltgrass, jaumea, and other 

low-growing herbs otherwise prevail. It does not spread into the low marsh where Pacific 

cordgrass and mudflats naturally dominate the Estuary (Kittleson and Boyd 1997). Chilean cordgrass lacks well-developed tissues specialized for transporting air from foliage to 

roots (Spicher 1984), a feature common to cordgrasses adapted to low marsh environments. 

Chilean cordgrass, along with other South American coastal species, was probably accidentally introduced to Humboldt Bay, California by ship ballast containing seeds from 

South American ports that traded lumber (Spicher 1984). For most of the 20th Century, 

Chilean cordgrass was erroneously treated as an "ecotype," or minor geographic variation, of the native Pacific cordgrass, despite the lack of diagnostic traits matching this 

San Francisco Estuary Invasive Spartina Project 13. 2008 Aquatic Pesticide Application Plan 
species. In the late 1970s, the presumed native "Humboldt Bay form" of Pacific cordgrass 

was deliberately transplanted to salt marsh restoration and landscaping sites at Creekside 

Park, Corte Madera, Marin County. Within the salt marshes fringing Corte Madera 

Creek, it has since become a locally dominant component of the middle and high salt 

marsh vegetation, displacing even robust pickleweed. 

A second population of Chilean cordgrass spontaneously established across the Bay from 

Creekside Park in the ancient marsh plain at Point Pinole (Whittell Marsh), Contra Costa 

County. The Point Pinole population was discovered in the mid-1990s, and has been 

largely controlled. A single, large, individual clump of Chilean cordgrass established in a 

very young restored tidal marsh (breached 1995) at the former Salt Pond 2A, Napa 

Marsh. That pioneer plant was also eradicated. 

Salt-Meadow Cordgrass (Spartina patens) 

Salt-meadow cordgrass is another rhizome-forming creeping cordgrass of Atlantic salt 

marshes, but unlike Atlantic smooth cordgrass, it has fine stems with narrow, soft, inrolled leaves, and is intolerant of waterlogged mud. It is naturally confined to the welldrained high salt marsh and relatively moist sandy depressions at or above tidal influence. 

Two distinctive geographic and ecological types have been recognized, and in the past 

have been treated as distinct taxonomic varieties. In peaty high salt marshes of the northeastern Atlantic coast, a relatively low form with lax, slender stems forming dense matted 

turfs with "cowlicks" was once treated as S. patens var. monogyna. These dense salt 

marsh turfs are often nearly pure stands of salt-meadow cordgrass crowding out most potentially associated species that occupy gaps in the cover caused by winter ice or drifted 

wracks. In sandy marshes associated with large barrier beaches and wash-over fans from 

Cape Cod through the Atlantic coastal plain, a coarser, erect type, formerly recognized as 

S. patens var. juncea, is prevalent. Intermediate forms are common. 

Between the 1959 publication of A California Flora (Munz and Keck 1959) and its 1970 

supplement, salt-meadow cordgrass was reported in Southampton Bay, Benicia, Solano 

County. The time and mode of introduction is unclear. Salt-meadow cordgrass at Southampton occupies large, discrete patches in pure and exceptionally thick stands compared 

with its native marshes. The patches are distributed close to tidal sloughs, a pattern suggesting local transport by currents. One large stand is spreading into a high marsh site 

(pickleweed-saltgrass vegetation) that supports a population of an endangered annual 

plant, soft bird's-beak (Cordylanthus mollis ssp. mollis). The Southampton Bay cordgrass 

population appears to match the type description of "variety monogyna," the fine-stem 

type of northeastern Atlantic marshes. 

5. CONTROL TOLERANCES 

As previously mentioned, the non-native Spartina invasion of the San Francisco Estuary 

is especially threatening to native marsh systems because of hybridization of Atlantic 

smooth cordgrass and the native Pacific cordgrass. This ability to hybridize, and the current expansion rates of the population of hybrid forms throughout the Estuary, defines the 

need for a zero tolerance threshold on invasive Spartina in San Francisco Bay. The Invasive Spartina Project is a regionally coordinated eradication effort that will ultimately be 

successful only if all infestations are effectively controlled and monitored to eradication. 

San Francisco Estuary Invasive Spartina Project 14. 2008 Aquatic Pesticide Application Plan 
A single small, expanding clone of hybrid Spartina within an otherwise native S. foliosa

matrix has the capability of ‘swamping’ S. foliosa flowers with hybrid pollen, effectively 

converting the native stand into a hybrid-producing population. Within a couple of growing seasons, the majority of new seedlings establishing in the area will be of hybrid origin, resulting in the eventual extirpation of the native S. foliosa from the stand. Repeated 

throughout the Estuary on various scales, this progression threatens the population stability of native pacific cordgrass stands. 

Therefore, where hybrid forms of Spartina are identified, efforts must be directed at removing all of the plants in the area. There is no acceptable level of hybrid presence in an 

otherwise native marsh, as the inevitable result of even a small amount of hybrid presence will be the relatively rapid conversion of the marsh to a non-native stand capable of 

infesting adjacent marshlands. 

Spartina densiflora has also been shown to have very rapid expansion rates in the Estuary. In addition, this plant invaded Humboldt Bay, CA to such a degree that approximately 80% of the mudflats and marsh lands have been dominated by it. We are fortunate 

in the San Francisco Estuary to have only isolated populations of S. densiflora at this 

point because of the efforts of the ISP and its partners, so as in the case with the more 

prevalent S. alterniflora hybrids, there is a need for zero tolerance and an excellent opportunity for the eradication of this species before it becomes widespread. 

For the other two invasive Spartina species in the Estuary, S. anglica and S. patens, each 

only inhabits a single infestation site and in a relatively small overall area. However, S. 

anglica is know to be the most invasive species of Spartina in the world, itself a fertile 

hybrid that has dominated introduction sites on several continents. With these types of 

threats, the fertile environment of the Estuary, and the current size of the infestations, a 

zero tolerance policy is appropriate. In addition, with a couple effective seasons of treatment, each of these species will be eradicated from the Estuary. 

6. DESCRIPTION OF HERBICIDE 

Herbicides have proven highly effective in controlling populations of cordgrasses 

(Spartina spp.). The aquatic formulation of imazapyr (Habitat®) was registered for use in 

the State of California on August 30, 2005. Previously, the Spartina Control Program 

used aquatic glyphosate-based herbicides (Aquamaster®, Rodeo®), which were the only 

herbicide formulations that could be used in sensitive estuarine systems and were designed to work on grasses/monocots. All ISP partners have since switched to imazapyr, 

although glyphosate will also be used at a single sub-site with special circumstances, and 

may be combined with imazapyr (according to the product labels) as a “brown-down indicator” to allow for more rapid detection of missed or skipped areas. Since imazapyr is 

such a slow-acting herbicide, it is difficult to know if the entire infestation at a site has 

been effectively treated until the following spring. Glyphosate treatment results in more 

noticeable yellowing/browning of the treated plants within a couple weeks. The use of a 

brown-down indicator would make any green, untreated plants stand out, and a follow-up 

spot treatment could be applied to these plants without losing a year of control. 

Imazapyr will also be used at a single site in 2008 to “chemically mow” Spartina areas to 

stop seed production but maintain above-ground biomass for endangered California clapper rail protection in sites where phased treatment is required. In this technique, a subSan Francisco Estuary Invasive Spartina Project 15. 2008 Aquatic Pesticide Application Plan 
lethal dose is applied to the plants, stopping their growth and seed production for a single 

season, but allowing them to return the following spring at or near their previous level on 

the site. 

There are a number of qualities that make imazapyr the ISP’s preferred choice over the 

previous alternative, glyphosate. Glyphosate tends to be strongly adsorbed to sediment 

and salt particles accumulated on the Spartina, rendering the herbicide inactive. It is 

common for the tides to deposit abundant sediment from the turbid San Francisco Bay 

onto the invasive Spartina in the adjacent salt marshes. Glyphosate also requires significantly longer dry times to fully penetrate the cuticle of the plant and begin translocation. 

Imazapyr does not have these issues that can reduce its efficacy. In addition, imazapyr is 

applied at lower concentrations and the applicator does not need to “spray to wet” as with 

glyphosate. This greatly reduces the amount of herbicide that will enter the environment 

as a result of the Spartina Control Program’s efforts, and allows for low volume applications such as aerial helicopter work. This herbicide delivery system is essential to the 

ISP’s initial efforts because of the vast acreage of Spartina infesting hazardous and difficult to access marshes. 

Aquatic herbicide formulations such as those used by ISP must be combined with a suitable surfactant to facilitate uptake and translocation of the herbicide down into the rhizomes. A harmless, inert marker dye or colorant is often added to the tank mix to assist 

the applicator at achieving full coverage while not over-applying to any areas. The following discussion addresses imazapyr, glyphosate, breakdown products, and typical surfactants and colorants. Detailed descriptions of the chemical properties, degradation rates, 

environmental fate, and toxicity of imazapyr, glyphosate, and all of the aquatic surfactants evaluated for the Spartina Control Program are provided in Appendix 1. 

Imazapyr. Habitat® or Polaris AQTM are solutions of 28.7% isopropylamine salt of imazapyr in water, equivalent to 22.6% imazapyr acid equivalents (a.e.) or 2 lbs. acid per gallon, and contain a small amount of an acidifier. Because Habitat® is purportedly the same 

formulation as Arsenal® and this product contains acetic acid, the acidifier in Habitat® is 

likely also acetic acid (Leson & Associates 2005.) No information has been found in the 

published literature on manufacturing impurities associated with imazapyr. Because virtually no chemical synthesis yields a totally pure product, technical grade imazapyr most 

likely contains some impurities. However, to some extent, concern for impurities in technical grade imazapyr is reduced by the fact that most existing toxicity studies on imazapyr were conducted with the technical grade product and encompass the toxic potential 

of the impurities (SERA 2004). A generic version of this aquatic imazapyr formulation is 

now available from NuFarm under the product name Polaris AQTM. 

Imazapyr inhibits an enzyme in the biosynthesis of the three branched-chain aliphatic 

amino acids valine, leucine, and isoleucine. Because animals do not synthesize branchedchained aliphatic amino acids but obtain them from eating plants and other animals, the 

engineered mechanism for plant toxicity, i.e. the interruption of protein synthesis due to a 

deficiency of the amino acids valine, leucine, and isoleucine, is not generally relevant to 

birds, mammals, fish or invertebrates. Any toxicity to these receptors occurs through different mechanisms (Entrix 2003). Imazapyr is relatively slow acting taking several weeks 

for the plants to show lethal effects. However, plants cease growth within 24 hours of a 

successful application (J. Smith, pers. comm. 2006). On Spartina, it takes 2-4 weeks after 

San Francisco Estuary Invasive Spartina Project 16. 2008 Aquatic Pesticide Application Plan 
treatment to see visible effects such as yellowing of the leaves, and complete plant death 

can take several months. In the San Francisco Estuary, with the relatively late season applications on invasive Spartina (mainly because of endangered species issues that effect 

access to the marshes), the treated plants may not reveal much of a response before natural senescence, but will simply not emerge in the spring of the following year if fully impacted. 

Glyphosate. Aquamaster® and Rodeo® are aqueous solutions containing 53.8% glyphosate in its isopropylamine salt form or 4 lbs. acid per gallon, and contain no inert ingredients other than water. The primary decomposition product of glyphosate is aminomethylphosphonic acid (AMPA), and the commercial product contains an impurity, 

2,4-nitrosoglyphosate (NNG). The potential effects of AMPA and NNG are encompassed 

by the available toxicity data on glyphosate and glyphosate formulations (SERA 1996). 

Glyphosate inhibits an enzyme needed to synthesize an intermediate product in the biosynthesis of the aromatic amino acids, essential for protein synthesis and to produce 

many secondary plant products such as growth promoters, growth inhibitors, phenolics, 

and lignin. Animals do not synthesize these aromatic amino acids and glyphosate therefore has low toxicity to these receptors. (Schuette 1998.) In general, glyphosate herbicides are somewhat faster acting than imazapyr herbicides. On Spartina, complete 

brown-down occurs within 7 to 21 days. (K. Patten, pers. comm. 2004). 

Surfactants. For most foliar applications of aquatic herbicide formulations, adjuvants 

must be added to spray solutions to improve the performance and minimize variation of 

herbicide efficacy. Surfactants are designed to improve the spreading, dispersing/emulsifying, sticking, absorbing, and/or pest-penetrating properties of the spray mixture (Tu et al. 2001). The pure herbicide formulation mixed with water will stand as a 

droplet on the waxy leaf surface and the small area of contact therefore provides little potential for uptake of the active ingredient into the foliage. Water droplets containing a 

surfactant will spread in a thin layer over a waxy leaf surface and improve herbicide uptake by maximizing herbicide distribution and forcing the fluid into the plant. As mentioned above, both Habitat® and Polaris AQTM, as well as the glyphosate herbicides 

Aquamaster® and Rodeo®, require the addition of surfactants for post-emergent applications such as the control of invasive Spartina. 

Imazapyr. The Habitat® specimen label recommends a variety of different spray 

adjuvants for use on post-emergent vegetation. For non-ionic surfactants the label recommends a rate of 0.25% v/v or higher, preferably of a surfactant with a hydrophilic to 

lipophilic ratio between 12 and 17 and with at least 70% surfactant in the formulated 

product (BASF 2003). Alternately, the label recommends the use of methylated seed oils 

or vegetable oil concentrates at the rate of 1.5 to 2 pints per acre. For spray volumes 

greater than 30 gallons per acre, the surfactant should be mixed at a rate of 1%. The label 

further indicates that these oils may aid in imazapyr deposition and uptake by the plants 

under moisture or temperature stress. Silicone-based surfactants, which may reduce the 

surface tension of the spray droplet, allowing greater spreading on the leaf surface as 

compared to conventional non-ionic surfactants, are also recommended. However, the 

manufacturer points out that some silicone-based surfactants may dry too quickly, limiting herbicide uptake (BASF 2004). 

San Francisco Estuary Invasive Spartina Project 17. 2008 Aquatic Pesticide Application Plan 
One study from Washington State concluded that the esterified seed oil surfactant tested, 

Competitor®, performed better than the other surfactants tested, i.e. Agri-Dex®, a crop 

oil-based surfactant, and R-11®, a non-ionic surfactant. This finding is also supported by 

Patten (2002) in which the author recommended using a methylated seed oil surfactant 

for aerial applications and for unfavorable conditions such as less than 6 hours of drying 

time or moist leaves. The experience of the ISP from 2005-2007 has shown that a lecithin 

product, Liberate®, has also been highly effective with imazapyr. In addition, this product 

acts as a drift retardant which may help in helicopter treatments as well as other broadcast 

applications to ensure full coverage on the target Spartina and minimize drift onto nontarget marsh plants.

Glyphosate. The Aquamaster® and Rodeo® specimen labels recommend the use of 

a non-ionic surfactant containing at least 50% active ingredient at a rate of 2 or more 

quarts per 100 gallons of tank mix (0.5% v/v). With glyphosate it is also important to balance the pH of the tank water to ensure effectiveness, and some adjuvants are designed 

with this purpose in mind, namely LI-700®. 

Not all surfactants provide the same effectiveness and surfactant costs vary widely. In 

general, non-ionic surfactants and crop oil concentrates are the least expensive of the surfactant classes, followed by esterified seed oils and organo-silicates. (Miller & Westra 

2004.) The ISP identified a number of potential surfactants for use with imazapyr and 

glyphosate. They include the non-ionic surfactants Liberate® and LI-700®, the crop-oil 

concentrate Agri-Dex®, the esterified seed oil Competitor®, and the organo-silicones 

Dyne-Amic® and Kinetic®. Based on the efficacy experienced by the ISP from 2004-

2007, and their superior relative toxicities, the ISP expects to continue to exclusively use 

Competitor® and Liberate® in the 2008 Spartina Control Program. LI-700® may be used to 

balance the pH of the tank if/when glyphosate is employed. 

Cygnet Plus® was evaluated and originally included in the ISP list of surfactant choices for 

2005, but it was shown to be ineffective with imazapyr and has been removed from the list 

available to the ISP partners. 

Competitor (Wilbur-Ellis Company) is a modified vegetable oil containing a non-ionic 

emulsifier system. The ingredients include ethyl oleate, sorbitan alkyl polyethoxylate ester, and dialkyl polyoxy-ethylene glycol. Toxicity studies classified this surfactant as a 

toxicity category of 3-4 (CAUTION). 

Liberate (Loveland Industries, Inc.) is a non-ionic, low foam penetrating adjuvant. Its active ingredients are lecithin (phosphatidylcholine, which is a naturally occurring lipid derived from soybeans that biodegrades readily), methyl esters of fatty acids, and alcohol 

ethoxylate. In a 1% solution, the pH is an almost neutral 6.8. Toxicity studies classified 

this surfactant as a toxicity category of 3-4 (CAUTION). It improves deposition and retards drift by producing a more uniform spray pattern. 

Dyne-Amic (Helena Chemical Company) is a proprietary blend of non-ionic organosilicone surfactants and a methylated vegetable oil. Toxicity studies classified this surfactant 

as a toxicity category of 3-4 (CAUTION). 

Kinetic (Helena Chemical Company) is a non-ionic wetting agent that allows for the 

rapid spreading and absorption of herbicide sprays into the target vegetation, and is especially effective with water-based herbicide formulations. Its active ingredients include 

San Francisco Estuary Invasive Spartina Project 18. 2008 Aquatic Pesticide Application Plan 
San Francisco Estuary Invasive Spartina Project 19. 2008 Aquatic Pesticide Application Plan 

organosilicone and polyoxypropylene-polyoxyethylene copolymer. Toxicity studies classified this surfactant as a toxicity category of 3-4 (CAUTION). 

Agri-Dex (Helena Chemical Company) is a non-ionic surfactant consisting of a paraffin 

base petroleum oil, polyol fatty acid esters, and polyethoxylated derivatives of the fatty 

acid esters. Toxicity studies classified this surfactant as a toxicity category of 3-4 

(CAUTION).3

. Biodegradation of this adjuvant is presumed to be rapid. 

LI-700 (Loveland Industries, Inc.) contains phosphatidylcholine (lecithin), which is a naturally occurring lipid that biodegrades readily. It also contains methylacetic acid and alkyl 

polyoxyethylene ether. Toxicity studies classified this surfactant as a toxicity category of 1 

(DANGER) because of corrosive properties to the skin and/or eyes. Biodegradation of this 

adjuvant is presumed to be rapid because of the natural lecithin ingredients. 

Colorant. There are several colorants suitable for use in the marsh environment, all of 

which are similar in composition and performance. Blazon Spray Pattern Indicator (Milliken Chemical), a typical colorant, is a water-soluble polymeric product. As with most 

colorant products, the active ingredients in Blazon are proprietary; the Material Safety 

Data Sheet (MSDS) indicates that it is non-hazardous and non-toxic. The product information sheet reports that the product is non-staining to the skin or clothing. A literature 

survey on the toxicity of color indicators done for the U.S. Department of Agriculture 

reports “most commercial indicators are blue ... and most often a form of Acid Blue 9...” 

(McClintock 1997 and Zullig 1997 cited in SERA 1997b). Acid Blue 9 is a disodium salt 

classed chemically as a triphenelmethane color (SERA 1997b). The Cosmetic, Toiletry, 

and Fragrance Association (CTFA) name for certified batches of Acid Blue 9 is FD&C 

blue No. 1. 

Herbicide application. Impacts to water quality from herbicide application depend on 

environmental fate, degradation rates of active agents and decomposition products of the 

herbicides. The primary route by which herbicide solution may contact water is by overspray directly onto the water surface or onto areas that will be covered by water on the 

next tide. Herbicide may also be washed off plants by tidal inundation or precipitation. 

Imazapyr and glyphosate solutions will be applied as sprays to Spartina foliage for control of this invasive plant. Spray mixtures may be dispersed from manually transported 

tanks (backpack sprayers) or spray equipment mounted on trucks, amphibious tracked 

vehicles, boats, or helicopters. Application rates will be consistent with the product labels 

(Table 4). 

Applications from backpack sprayers or conventional spray truck entails workers walking 

through the marsh and applying herbicide directly to target plants, with limited overspray 

to surrounding plants or water surfaces. Spot application from amphibious tracked vehicles or boats would entail vehicles moving through the marsh or adjacent waterway applying herbicide with hand-held equipment to target vegetation with limited overspray. 

Aerial ap-plication is conducted by helicopter (the imazapyr label does not allow for 

fixed-wing air-craft to be used) with either a boom sprayer (a horizontal pipe with spray 

nozzles along its length, mounted to the bottom of the helicopter) or a spray ball (a hollow ball with nozzles suspended from the bottom of the helicopter). Broadcast aerial 

 

3 Toxicity categories are determined by the U.S. EPA for human health affects. See 

http://www.epa.gov/oppfead1/labeling/lrm/chap-08.htm for more information on pesticide label requirements. 
San Francisco Estuary Invasive Spartina Project 20. 2008 Aquatic 

Table 4a: Imazapyr herbicide mixture component concentrations and application rates for treatment of non-native Spartina 

ary (Leson & Associates 2005.) 

Application Method Spray Volume Formulation Active Ingredient1 Surfactant2 

High volume handheld sprayer 100 gal/acre 0.52-0.75% solution 4-6 pints/100 gal 1-1.5 lb a.e./acre 0.25% v/v NIS with ≥70% a.i

~1% v/v MSO, ESO, or VOC

SBS according to label 

Low-volume directed sprayer 20 gal/acre 0.75-1.5% solution 1.2-2.4 pints/20 gal 0.3-0.6 lb a.e./acre 0.25% v/v NIS with ≥70% a.i

~1% v/v MSO, ESO, or VOC

SBS according to label 

Broadcast sprayer/ Aerial application 10-30 gal/acre 2.5-7.5% solution 6 pints/10-30 gal 0.5-1.5 lb a.e./acre 0.25% v/v NIS with ≥70% a.i

~1% v/v MSO, ESO, or VOC

SBS according to label 

1 Active ingredient in Habitat® is imazapyr isopropylamine salt; values expressed as imazapyr acid equivalent 2 NIS = non-ionic surfactant; MSO = methylated seed oil; ESO = esterified seed oil; VOC = vegetable oil concentrate, SBS = silicone-based surfactant, %

volume by volume

Table 4b: Glyphosate herbicide mixture component concentrations and application rates for treatment of non-native Spartin

tuary (Leson & Associates 2005.) 

Application Method Spray Volume Formulation Active Ingredient1 Surfactant2* 

High volume handheld sprayer 100 gal/acre 1-2% solution 1-2 gal/100 gal 4-8 lb a.e./acre ≥0.5% v/v NIS with ≥50% a

Low-volume directed sprayer 25-200 gal/acre 1-8% solution 1-8 gal/100 gal 1.35-10.8 lbs a.e./acre ≥0.5% v/v NIS with ≥50% aBroadcast sprayer/ Aerial application 

7-40 gal/acre/ 

7-20 gal/acre 4.5-7.5 pints/acre 2.25-3.75 lb a.e./acre ≥0.5% v/v NIS with ≥50% a

1 The active ingredient in Rodeo® and Aquamaster® is glyphosate isopropylamine salt; values are expressed as glyphosate acid equivalent 

2 NIS = non-ionic surfactant, %v/v = percentage based on volume by volume
application involving a boom sprayer would result in a wider dispersion of herbicides, 

with greater potential for overspray onto non-target areas or the water surface. However, 

for aerial treatment on smaller patches of invasive Spartina, the boom may be shortened 

up and the apparatus turned on only when over the target vegetation. Aerial application 

will be used primarily at large areas of dense cordgrass infestations, particularly in locations where little native cordgrass and other non-target plants are nearby. 

Applications from backpack sprayers or conventional spray truck entails workers walking 

through the marsh and applying herbicide directly to target plants, with limited overspray 

to surrounding plants or water surfaces. Spot application from amphibious tracked vehicles 

or boats would entail vehicles moving through the marsh or adjacent waterway applying 

herbicide with hand-held equipment to target vegetation with limited overspray. Aerial application is conducted by helicopter (the imazapyr label does not allow for fixed-wing aircraft to be used) with either a boom sprayer (a horizontal pipe with spray nozzles along its 

length, mounted to the bottom of the helicopter) or a spray ball (a hollow ball with nozzles 

suspended from the bottom of the helicopter). Broadcast aerial application involving a 

boom sprayer would result in a wider dispersion of herbicides, with greater potential for 

overspray onto non-target areas or the water surface. However, for aerial treatment on 

smaller patches of invasive Spartina, the boom may be shortened up and the apparatus 

turned on only when over the target vegetation. Aerial application will be used primarily at 

large areas of dense cordgrass infestations, particularly in locations where little native 

cordgrass and other non-target plants are nearby. 

Environmental Fate of Herbicides 

Herbicide mixtures may be indirectly discharged to surface waters by tidal action or rainfall that rinses the herbicide solution from the plants. Rainfall is unlikely to occur during 

the planned application season (summer in the San Francisco Bay region), and herbicide 

applications would be postponed if rainfall were predicted, but tidal inundation is inevitable on a regular cycle. Applications to invasive Spartina along slough or creek banks or 

at the Bayfront on fringe marshes and mudflats will result in a small percentage of the 

herbicide directly entering the water column. 

Food-web exposures become significant only with chemicals that have a tendency to bioaccumulate or biomagnify. The adverse effects associated with bioaccumulative chemicals relate to their propensity to transfer through the food web and accumulate preferentially in adipose or organ tissue. Basic routes for organism exposure to bioaccumulative 

compounds are the transport of dissolved contaminants in water across biological membranes, and ingestion of contaminated food or sediment particles with subsequent transport across the gut. For upper-trophic-level species, ingestion of contaminated prey is the 

predominant route of exposure, especially for hydrophobic chemicals. 

U.S. EPA’s Hazardous Waste Identification Rule (USEPA 1999) identifies compounds 

that are recognized as having a low, medium or high potential for bioaccumulation. For 

bioaccumulation in aquatic systems, rankings were determined using bioaccumulation 

factors in fish, which are indicated in laboratory tests as having low octanol-water partitioning coefficient (or log Kow)) values for organic compounds. Bioaccumulation potential is defined as follows: 

San Francisco Estuary Invasive Spartina Project 21. 2008 Aquatic Pesticide Application Plan 
Bioaccumulation 

potential 

Bioaccumulation Factor 

(BAF) log Kow

High BAF >= 10,000 log Kow >= 4.0 

Medium 10,000 > BAF >= 100 4.0 > log Kow >= 2.0 

Low BAF < 100 log Kow < 2.0 

Imazapyr. Under typical environmental conditions of pH 5-9, imazapyr is ionized and is 

therefore highly soluble in water. Because of its high solubility, imazapyr has an inherently low sorption potential with a low soil organic carbon sorption coefficient (Koc) of 

8.81 (log Koc), suggesting very high mobility in soil and little adsorption to suspended 

solids and sediment. Its octanol/water partition coefficient (Kow) has been reported at 0.22 

(log Kow), reflecting its high solubility in water and low solubility in lipids, and hence 

low propensity to bioconcentrate. A low bioconcentration factor (BCF) of 3 was calculated for imazapyr, which suggests a low potential for bioconcentration in aquatic organisms (Leson & Associates 2005). 

Imazapyr is relatively mobile in soils because it only weakly adsorbs to soils and sediments. Adsorption increases with decreasing pH. Above a pH of 5, imazapyr is ionized 

and does not adsorb to soil. Aerobic degradation in soils occurs primarily by very slow 

microbial metabolism with quinoline as the main metabolite (Entrix 2003). 

Conditions in sediments differ substantially from those in soils, both in terms of the regular exchange of waters within the sediment pore water and over it, and in the degree of 

oxygenation in sediments that affect microbial metabolism. Because the pH of sediment 

surfaces and sediment pore water in intertidal mudflats is above neutral (pH >7), imazapyr will be entirely in its ionized form. Thus, adsorption to sediments is expected to be 

minimal. (Entrix 2003.) Microbial metabolism in sediments has been determined to be 

insignificant. One study determined the half-life of imazapyr in the pore water of aerobic 

sediment at 17 months. 

The degradation of imazapyr when applied directly to water largely mimics the pathway 

by which the herbicide would be mobilized at high tide after application to Spartina during low tide. Residual imazapyr on the plants that have not completely dried or did not 

get absorbed by the plants will be inundated by the incoming tide and presumably solubilized. Aquatic degradation studies under laboratory conditions demonstrated rapid initial 

photolysis of imazapyr with reported half-lives ranging from 3 to 5 days (SERA 2004). 

The two primary photodegradation products were rapidly degraded with half-lives less 

than or equal to 3 days and eventual mineralization to carbon dioxide (Entrix 2003). 

Degradation rates in turbid and sediment-laden waters, common to estuarine environments, are expected to be lower than those determined under laboratory conditions. In 

controlled field dissipation studies in two freshwater pond systems with application of 

1.5 lb imazapyr a.e./acre, imazapyr rapidly dissipated from the water with first-order halflives of 1.9 days and 12.8 days. No detectable residues of imazapyr were found in the water and sediment after 14 and 59 days, respectively. (Entrix 2003.) The ISP’s NPDES water quality monitoring at treatment sites over the past several years has found a standard 

reduction in imazapyr in the adjacent surface water of more than 95% one-week posttreatment over the amount present immediately after the application. 

San Francisco Estuary Invasive Spartina Project 22. 2008 Aquatic Pesticide Application Plan 
In estuarine systems, dilution of imazapyr in the incoming tide will contribute to its rapid 

dissipation and removal from the area where it has been applied. Studies in estuaries in 

Washington State examined the fate of imazapyr applied at a standard rate of 1.5 lb imazapyr a.e./acre directly to sediment. The study design was conservative because imazapyr 

was applied to bare mudflats with no algal or emergent vegetation intercepting the herbicide. The study measured immediate maximum concentrations of imazapyr in intertidal 

waters and sediment less than 3 hours after application and short-term concentrations between 24 and 72 hours after application. Sediment samples collected 3 hours after application were retrieved immediately after the first tidal wash over the area. Maximum concentrations in water and sediment were detected at 3.4 mg/L and 5.4 mg/kg, respectively. 

Measurable concentrations of imazapyr declined exponentially in both water and sediment, approaching the zero-asymptote at 40 and 400 hours with half-lives of <0.5 and 1.6 

days, respectively. Water collected 20 and 200 feet outside the spray zone with the first 

incoming tide was 99% lower than the maximum water concentration at the edge of the 

spray zone (Leson & Associates 2005). Application of the same amount of herbicide to a 

stand of 5.5-foot tall Spartina resulted in a 75% reduction in concentrations in sediment 

through interception by the canopy (Patten 2003). In sum, this research suggests that imazapyr quickly dissipates in estuarine environments. In addition, the same researcher observed that other vegetation rapidly colonizes the plots treated with imazapyr after the 

Spartina plants have died, which supports the conclusion of very low persistence of imazapyr in estuarine environments. The ISP has observed this phenomenon of rapid native 

plant colonization of treated areas at many sites around San Francisco Bay since 2005, 

usually involving either annual pickleweed (Salicornia europaea), perennial pickleweed 

(Sarcocornia pacifica), or Jaumea carnosa. 

Glyphosate. Under typical environmental conditions of pH 5-9, glyphosate is ionized. 

Glyphosate and its salts are readily soluble in water with a solubility of about 12,000 

mg/L. Its interactions with soil and sediment are primarily ionic, rather than hydrophobic 

and pH dependent. Laboratory and field studies indicate that glyphosate is strongly and 

reversibly adsorbed by soil, sediment, and suspended sediment. Glyphosate is inactivated 

through soil adsorption. Because glyphosate adheres strongly to particles, it does not 

readily leach to waters (Sprankle et al., 1977 cited in Albertson, 1998), and potential 

movement of glyphosate to groundwater is unlikely. Due to its negligible vapor pressure 

(7.5×10-8 mmHg) and its ionic state in water, glyphosate is not expected to volatilize 

from water or soil. Glyphosate’s Kow has been reported at 0.00033, indicating its high 

solubility in water, low solubility in lipids, and thus low potential to bioconcentrate. 

All reported bioaccumulation factor values for glyphosate in aquatic organisms are well 

below 100 (Ebasco 1993; Heyden 1991; Wang et al. 1994). The highest bioaccumulation 

factor of 65.5 was reported for tilapia (a species of fish) in fresh water (Wang et al.

1994). Other studies report much lower bioaccumulation factors in the range of 0.03 to 

1.6 for fish (Ebasco 1993). Most studies report rapid elimination and depuration from 

aquatic organisms after exposure stops (Ebasco 1993). Therefore, bioaccumulation of 

glyphosate is considered to be low and food-web transfer is not considered to be a significant exposure route. 

Soil studies have determined glyphosate half-lives ranging from 3 to 130 days. The soil 

field dissipation half-life averaged 44 to 60 days. (Leson & Associates 2005.) In the soil 

environment, glyphosate is resistant to chemical degradation, is stable to sunlight, is relaSan Francisco Estuary Invasive Spartina Project 23. 2008 Aquatic Pesticide Application Plan 
tively non-leachable, and has a low tendency to runoff (except as adsorbed to colloidal 

matter). It is relatively immobile in most soil environments as a result of its strong adsorption to soil particles. Glyphosate is rapidly and strongly adsorbed to sediment, which 

appears to be the major sink for glyphosate in aquatic systems. Like in soils, the herbicide 

is inactivated and biodegraded by microorganisms. 

Several studies indicate that glyphosate is stable in water at pH ranging from 3 to 6. The 

photolytic half-life of glyphosate in deionized water exposed outdoors to sunlight was 

approximately 5 weeks at 100 ppm and 3 weeks at 2000 ppm. Glyphosate shows little 

propensity toward hydrolytic decomposition. Its hydrolysis half-life is greater than 35 

days. It is also stable to photodegradation under visible light but photolyzes when exposed to UV radiation. Glyphosate’s loss from water occurs mainly through sediment adsorption and microbial degradation. The rate of microbial degradation in water is generally slower because there are fewer microorganisms in water than in most soils. Studies 

conducted in a forest ecosystem found that glyphosate dissipated rapidly from surface 

water ponds high in suspended sediment, with first order half-lives ranging from 1.5 to 

11.2 days. In streams, residues were undetectable within 3 to 14 days. Other studies using 

water from natural sources determined glyphosate’s half-life ranging from 35 to 63 days. 

(Leson & Associates 2005.) For all aquatic systems, sediment appears to be the major 

sink for glyphosate residue. A review of the literature on glyphosate dissipation applied 

under estuarine conditions suggests that 24 to 48 hours after applications, glyphosate 

concentrations in water were reduced by more than 60-fold. 

Energetic tidal cycles and tidal currents effectively disperse bound (adsorbed) glyphosate 

and surfactants and dilute them in microbially active suspended sediment. Studies of the 

fate of glyphosate and surfactants applied in tidal marshes and mudflats have reported 

that concentrations of both substances dropped below detection levels as soon as two 

tidal cycles (one day) to seven days (Kroll 1991, Paveglio et al. 1996) after application. 

The initial tidal submergence of sprayed surfaces disperses a large fraction of applied 

glyphosate and surfactant. 

Research conducted for the California Department of Food and Agriculture (Trumbo 

2002) studied the environmental fate and aquatic toxicity of Rodeo and R-11 in three locations, including a Sacramento-San Joaquin Delta slough, a riverine area, and a nooutlet pond. This study measured glyphosate, aminomethylphosphonic acid (AMPA; glyphosate’s primary metabolite), nonylphenol ethoxylate, and nonylphenol at treated sites 

one hour, two days, and eight days after application. The study also tested for toxicity 

using 96-hour toxicity tests with the fish species fathead minnow Pimephales promelas. 

The study found that concentrations of the tested constituents at slough and river sites 

(with moving water) was below detectible levels for all tests, and that there was no significant mortality of test fishes. The pond site, however, showed detectable residues of 

glyphosate, nonylphenol ethoxylate, and nonylphenol at one hour and two days after 

treatment, but all constituents were below detection limits by day eight. The one-hour 

pond samples experienced 30% mortality of test fishes, which, because of the relatively 

low concentrations of glyphosate (which is known to be non-toxic at the detected level), 

was attributed to effects caused by nonylphenol ethoxylate and nonylphenol. The two- and 

eight-day tests showed no significant mortality to test fishes. 

Patten (2002) compiled data on the fate of glyphosate in water and sediment following 

applications in estuarine environments. Data are presented as geometric means for immeSan Francisco Estuary Invasive Spartina Project 24. 2008 Aquatic Pesticide Application Plan 
diate maximum concentration (<3hrs after application) and short-term concentration (between 24 hrs and 48 hrs after application). For use rates between 8 and 16 kg/ha (7-15 

lbs/acre), the immediate maximum geometric mean glyphosate concentrations were 0.174 

mg/L (174 μg/L) in water and 2 mg/kg in sediment. The short-term geometric mean glyphosate concentrations were 0.003 mg/L (3 μg/L) in water and 1.9 mg/kg in sediment. 

These independent lines of research in the fate of imazapyr or glyphosate combined with 

a surfactant in tidal (and other) habitats suggest that potential impacts to water quality 

and beneficial uses of waters of the State caused by spraying these herbicide mixtures in 

intertidal environments are likely be small and temporary. Therefore, controlled applications (i.e., following label instructions) of registered herbicides are not expected to degrade water quality, except for limited temporal and spatial extent. 

In summary, the use of imazapyr or glyphosate combined with a surfactant to treat infestations of non-native cordgrass would result in less than significant impacts on water 

quality due to the rapid degradation rate and controlled application of herbicides only on 

target plants. Since application of herbicides would take place during low tide and low 

wind conditions, the herbicide would likely be absorbed by plants for a minimum of several hours (up to several weeks in high marsh) following application resulting in less than 

significant quantities of imazapyr, glyphosate or surfactants entering the water. 

Potential Biological and Ecological Effects 

The known properties of the herbicides, potential methods of application, and the ecological characteristics of the Estuary were evaluated to develop a conceptual model (Figure 2) and identify likely receptors and exposure pathways. This model includes identification of primary and secondary herbicide sources, release mechanisms, exposure media, 

exposure routes, and potential ecological receptors. 

For effects to occur, a receptor and a complete exposure pathway must be present. An 

exposure pathway is only considered complete when all four of the following elements 

are present: project- related source of a chemical, a mechanism of release of the chemical 

from the source to the environment, a mechanism of transport of the chemical to the ecological receptor, and a route by which the receptor is exposed to the chemical. 

The exposure routes associated with the complete pathways include direct contact with 

the herbicide mixture during and immediately after application, ingestion of contaminated surface water and sediments, direct contact with contaminated surface water and 

sediments, and food-web exposure. The conceptual model (Figure 2) illustrates the links 

between sources, release and transport mechanisms, affected media, exposure routes, and 

potentially exposed ecological receptors. Although several complete exposure pathways 

may exist, not all pathways are comparable in magnitude or significance. The significance of a pathway as a mode of exposure depends on the identity and nature of the 

chemicals involved and the magnitude of the likely exposure dose. For birds and mammals, ingestion is generally the most significant exposure pathway. Dermal contact is expected to be insignificant and unquantifiable due to the nature of the site and frequent 

movement, ranging habits, and furry or feathery outer skin of most wildlife species. 

Because Project applications of herbicides would occur only once or (at most) twice a 

year, and compounds in the herbicide mixture are not expected to persist in significant 

concentrations for more than several hours, chronic exposure is not likely. In addition, 

since imazapyr is a newly registered herbicide in California as of 2005, there are few 

San Francisco Estuary Invasive Spartina Project 25. 2008 Aquatic Pesticide Application Plan 
PRIMARY 

SOURCE

RELEASE 

MECHANISM

SECONDARY 

SOURCE

RELEASE 

MECHANISM

EXPOSURE 

MEDIUM

Uptake/ Direct Contacta

Ingestion

Food-Web Exposure

Inhalation

Uptake/ Direct Contacta

Ingestion

Food-Web Exposure

Uptake/ Direct Contacta

Ingestion

Food-Web Exposure

EXPOSURE 

ROUTE

C IC IC IC C IC IC C IC IC

IC IC IC IC C C M C C M

IC IC IC IC M C M C C M

MCM N M C M M M M

MCM N M M M M M M

M M IC M M IC IC M IC IC

Legend:

C Potentially complete pathway (evaluated in a quantitative way)

N Not quantified because insufficient data available

M Minor or insignificant pathway 

IC Incomplete pathway 

a

 Direct contact refers to dermal exposure.

Herbicide Mixture in Tanks and 

Equipment

Partioning into Water/ 

Adsorbing to Sediment

Accidental Spills

Herbicide Mixture before 

adsorption/dilution occurs)

Application

Non-Target Aquatic Plants and 

Algae

Aquatic and Benthic 

Invertebrates

Fish

Humans (Applicators)

Potential Ecological Receptors

Herbicide Mixture (before 

adsorption/dilution occurs)

Mixing and Dispersion

Sediment Surface Water

Sediment Surface Water

Mammals

Birds

other sources for its introduction to the environment to add to those of the ISP. Therefore, 

this evaluation focuses on acute toxicity, which would occur when the compounds are 

present at relatively high concentrations during and immediately following application. 

Figure 3.3-2. Conceptual Model of Possible Exposure of Biological Organisms to Herbicide Mixture Used

by the Spartina Control Program

Figure 2. Conceptual Model of Possible Exposure of Biological Organisms to Herbicide Mixture Used by the

Spartina Control Program

Herbicide solutions have the potential to affect organisms that live in the water column, 

including algae, non-target plants, fish and aquatic invertebrates. While some other recepSan Francisco Estuary Invasive Spartina Project 26. 2008 Aquatic Pesticide Application Plan 
tors such as mammals and birds may spend a considerable portion of their time in the water, they are generally more likely to be affected by other exposure routes, primarily dermal contact during application and incidental ingestion of contaminated sediment during 

foraging. 

Non-Target Aquatic Plants and Algae 

Due to their engineered mechanisms of action, imazapyr and glyphosate are toxic to a 

wide variety of plants. Native salt marsh plants, aquatic macrophytes, and algae in the 

Estuary waters where the herbicides would be applied could be negatively affected. 

However, both imazapyr and glyphosate are ineffective for treating submerged aquatic 

vegetation. 

Imazapyr. The species most sensitive to technical grade imazapyr and an herbicide/surfactant mixture appear to be aquatic macrophytes with reported EC25 values for 

duckweed (Lemna gibba) of 0.013 mg/L for growth and for common water milfoil 

(Myriophyllum sibiricum) of 0.013 mg/L for shoot growth and 0.0079 mg/L for root 

growth. (Hughes 1987; Roshon et al. 1999; both in SERA 2004.) Aquatic algae appear to 

be substantially less sensitive. The most sensitive species of algae tested was a unicellular 

green algae (Chlorella emersonii) with an EC50 of about 0.2 mg/L for growth. Some algal 

species appear to be stimulated rather than inhibited by imazapyr concentrations of up to 

100 mg/L. (Hughes 1987 in SERA 2004.) Some species of plants, including aquatic 

plants, may develop resistance to imazapyr. Bioassays conducted on Chlorella emersonii

indicated that resistant strains may be less sensitive by a factor of 10. (Landstein et al.

1993 in SERA 2004.) Due to the infrequent application of imazapyr for control of 

Spartina, i.e. once per year, development of resistance to imazapyr is unlikely. 

Recent studies conducted in Washington State also document the potential for imazapyr 

to impact non-target vegetation. Effects of imazapyr application on non-native Japanese 

eelgrass were compared to glyphosate application. For both herbicides, the eelgrass canopy was killed if herbicide was applied on dry eelgrass at low tide with imazapyr being 

more toxic. Application onto an eelgrass bed with a thin overlying film of water did not 

result in toxic effects. Within 12 months, all treated eelgrass beds had recovered. Persistence was not recorded in the sediment underlying these eelgrass beds. (Patten 2003.) 

Glyphosate. In laboratory growth inhibition studies with submerged aquatic plants no adverse effects on the growth of elodea (Elodea canadensis), water milfoil (Myriophyllum 

spicatum), and wild celery (Valisneria americana) were found with glyphosate concentrations of up to 1 mg/L. (Forney & David 1981 in WS FEIS 1993.) These results are 

consistent with the findings of other investigators who report that submerged plants are 

either resistant or affected only by very high glyphosate concentrations. (Evans 1978; 

Peverly & Crawford 1975; both in WS FEIS 1993.) A large number of studies with a variety of green algae, blue-green algae, diatoms, and periphyton indicate that glyphosate is 

slightly toxic to practically non-toxic to most algae. Most algae tolerate concentrations of 

glyphosate greater than 1 mg/L. (WS FEIS 1993.) Species of algae vary in their sensitivity to glyphosate in terms of population growth (EXTOXNET, Giesy 2000). Field studies 

indicate the least toxicity to phytoplankton (microscopic floating algae), possibly because 

of dilution and adsorption in open water and flooded marshes. 

Few data are available on effects to marine algae, as most toxicity tests have been performed on freshwater species. Giesy et al. (2000) reviewed the data available on glySan Francisco Estuary Invasive Spartina Project 27. 2008 Aquatic Pesticide Application Plan 
phosate toxicity to micro-organisms, and found that acute toxicity EC50 values ranged 

from 2.1 to 189 mg/L. NOECs ranged from 0.73 to 33.6 mg/L. Giesy et al. (2000) also 

reviewed the data available on glyphosate toxicity to aquatic macrophytes, and found that 

acute toxicity EC50 values ranged from 3.9 to 15.1 mg/L. 

It should be noted that these studies included tests on the (non-aquatic) Roundup formulation as well as other forms of glyphosate. The formulated product known as Roundup, 

which includes the terrestrial surfactant polyethoxylated tallowamine (POEA) is known 

to be more toxic than the technical grade glyphosate found in aquatic formulations such 

as Aquamaster. For studies conducted on microorganisms using glyphosate tested as isopropylamine salt, EC50 values ranged from 72.9 to 412 mg/L, and NOEC values ranged 

from 7.9 to 26.5 mg/L (Giesy et al. 2000). The lowest of these NOEC values (0.73 mg/L) 

is well above the maximum concentration of 0.026 mg/L reported by Paveglio et al. 

(1996) and the immediate maximum geometric mean glyphosate concentration of 0.174 

mg/L reported by Patten (2002). Therefore, these data indicate that impacts to non-target 

submerged aquatic plants or algae are not likely. Impacts in estuarine conditions with 

high concentrations of suspended sediment, which interfere with glyphosate activity, 

would be even less likely. 

Aquatic and Benthic Invertebrates 

Imazapyr. Imazapyr has been found to have low toxicity to aquatic invertebrates. A study 

where Daphnia was exposed to an imazapyr formulation (~50%) produced a 48-hour 

EC50 concentration of 373 mg imazapyr a.e./L (Cyanamid 1997 in Entrix 2003.). Another 

study with Arsenal® (identical to Habitat®) with an unspecified surfactant determined a 

48-hour LC50 of 350 mg Arsenal/L (79.1 mg imazapyr a.e./L) and a NOEC of 180 mg 

Arsenal/L (40.7 mg imazapyr a.e./L) for the freshwater flea (Daphnia magna), highlighting the potential effects of surfactants on aquatic toxicity. Other studies also reported 24 

and 48-hour LC50 concentrations of greater than 100 mg/L, the highest dose tested 

(“HDT”), in static tests conducted with newly-hatched Daphnia. (Kintner & Forbis 1983 

in SERA 2004.) Chronic studies reported no adverse effects on survival, reproduction or 

growth of 1st generation Daphnia after 7, 14 and 21-days of exposure at concentrations 

up to 97.1 mg/L, the HDT. (Manning 1989 in SERA 2004.). Testing with other invertebrate species that exhibit alternative life cycles has been limited to survival of pink 

shrimp (Penaeus duorarum) and growth studies with the Eastern oyster (Crassostrea virginica). Acute toxicity to pink shrimp was determined at LC50 >132 mg imazapyr a.e. /L, 

the HDT, which was also the NOEC. The EC50 for growth inhibition of the Eastern oyster 

was established at a concentration greater than 132 mg imazapyr a.e./L, with the NOEC 

set at this concentration, the HDT. (Mangels & Ritter 2000 in SERA 2004.)

A recent microcosm study analyzing benthic macroinvertebrates in a logged pond confirmed the low toxicity of imazapyr to benthic freshwater macroinvertebrates. The study 

analyzed macroinvertebrate community composition, chironomid deformity rate, and chironomid biomass and concluded that imazapyr did not affect the macroinvertebrate 

community at the concentrations tested. The NOEC was determined to be greater than 

18.4 mg/L (Fowlkes et al. 2003.) 

Glyphosate. Glyphosate is only slightly toxic to practically non-toxic to marine and 

freshwater aquatic invertebrates. Acute toxicity for freshwater invertebrates varies from 

545 to 780 mg/L for water flea (Daphnia magna), to 673 mg/L for mosquito 4th instar 

(Anopheles quadrimaculatus), to 1,157 mg/L for a leech (Nephaelopsis obscura). Acute 

San Francisco Estuary Invasive Spartina Project 28. 2008 Aquatic Pesticide Application Plan 
toxicity for marine invertebrates was reported as greater than 10 mg/L for Atlantic oyster 

larvae (Crassostrea virginica), 281 mg/L for grass shrimp (Palaemonetes vulgaris), and 

934 mg/L for fiddler crab (Uca pugilator). (ExToxNet 2005; Henry 1992, Heydens 1991; 

both in SERA 2004.) The wide variation in the aquatic toxicity of glyphosate has been 

attributed to the dilution water, temperature, formulation, and the amount of suspended 

sediment in the water. Toxicity appears to increase with temperature, and decrease with 

elevated pH and suspended sediment. (Schuette 1998). 

Giesy et al. (2000) reviewed the data available on glyphosate toxicity to aquatic invertebrates. Few data were available for marine species, and those studies that did use marine 

species were conducted with glyphosate acid, not salt. Acute toxicity EC50 values for five 

marine species ranged from 281 mg/L to greater than 1000 mg/L, and NOEC values 

ranged from 10 to 1000 mg/L. Data compiled by Ebasco (1993) include mortality tests on 

two marine species, for which EC50 values were found to be 281 mg/L and greater than 

1,000 mg/L. 

Grue et al. (2002) conducted laboratory studies to evaluate reproductive effects of exposure to Rodeo mixed with four different surfactants, including R-11, LI 700, and Agridex, on Pacific oysters. The EC50 for glyphosate alone was 68.1 mg/L, the EC50 for the 

tank mix including Rodeo and R-11 surfactant was 29.9 mg/L, and the EC50 for the R-11 

surfactant alone was 1.0 mg/L. 

The lowest of these NOEC and LC50 values (10 mg/L) for glyphosate or glyphosate/surfactant mixtures is well above the maximum glyphosate concentration of 

0.026 mg/L reported by Paveglio et al. (1996) and the immediate maximum geometric 

mean glyphosate concentration of 0.174 mg/L reported by Patten (2002). Therefore, these 

data indicate that impacts to aquatic invertebrates due to post-application water concentrations of glyphosate are unlikely in experimental conditions. Impacts in estuarine conditions with high concentrations of suspended sediment, which interfere with glyphosate 

activity, would be even less likely. 

Kubena et al. (1997) conducted sediment and water toxicity studies on marine invertebrates (oysters and amphipods). The LC50 values for Rodeo and surfactant in water 

ranged from 200 to 400 mg/L, and the LC50 values in sediment ranged from 1000 to 6000 

mg/kg. These LC50 values are well above the highest measured geometric mean sediment 

concentrations of 2.3 mg/L reported by Kilbride et al. (2001) and Patten (2002). 

Field studies of glyphosate/surfactant applications to tidal mudflat invertebrate communities in Willapa Bay, Washington, agree with laboratory tests, which indicate low potential 

for adverse impacts to benthic invertebrates. Sampling of benthic invertebrates in mudflats up to 199 days after glyphosate/surfactant (X-77) applications revealed no shortterm or long-term effects. Short-term laboratory tests of amphipods exposed to glyphosate and surfactants did not affect survival even at high concentrations relative to 

post-spray field conditions (Kubena 1996). 

Fish 

Imazapyr. As detailed in both the 2003 Entrix and 2004 SERA reports, a number of standard bioassays submitted to the U.S. EPA in support of the registration of imazapyr indicate very low toxicity to fish with 96-hr LC50 values greater than 100 mg/L in most studies. According to U.S. EPA’s ecotoxicity classification for aquatic organisms (see Table 

A-6), these values classify imazapyr as practically non-toxic, the lowest category for adSan Francisco Estuary Invasive Spartina Project 29. 2008 Aquatic Pesticide Application Plan 
dressing acute risk to aquatic organisms from use of chemicals. (U.S. EPA 2005.) A recent study suggests that both Habitat® and Rodeo® have relatively low toxicity to juvenile 

rainbow trout. The LC50 determined for Arsenal® (a terrestrial formulation identical to 

Habitat® that did not contain any surfactants) was determined at 22,305 mg imazapyr 

a.e./L. (King et al. 2004.) 

One study reported much lower 96-hr LC50 values of 4.7 mg/L for Nile tilapia (Tilapia 

nilotica) and 2.7 mg/L for silver barb (Barbus genionotus). (Supamataya et al. 1981 in 

SERA 2004.) Although the herbicide used was not specified, it is likely that a formulation was used rather than the technical grade active ingredient. Historically imazapyr herbicides contained surfactants and a formulation that removed the surfactant was only developed in 1992. The use of an herbicide containing surfactants might explain the considerably lower LC50 values. The 2004 SERA report used the lowest LC50 value from this 

study, 2.7 mg/L, for their risk assessment despite some reservations about the study due 

to the fact that they only had access to its abstract and because the species studied were 

not native to the U.S. Nevertheless, the 2004 SERA report assumed that, even though the 

study was not well documented, the response of these apparently sensitive species may 

well encompass the response of other sensitive species native to the U.S. (SERA 2004, 

p. 4-22.) This conclusion is supported by a study that examined the comparative sensitivity of eight ESA-listed fish species to standard test organisms exposed to five different 

pesticides or metals in order to validate the use of surrogate species as a predictive tool 

in toxicological assessments. Based on their findings, the authors concluded that a 

safety factor of two would provide a conservative estimate in risk assessments for listed 

cold-water, warm-water and euryhaline fish species. (Sappington et al. 2000 in Entrix 

2003, p. 49.) 

Glyphosate. Acute toxicity studies with warm and cold water fish indicate that technical 

glyphosate is slightly to practically non-toxic. (U.S. EPA 1993.) Acute toxicity LC50 values were reported at 86 mg/L in rainbow trout, 120 mg/L in bluegill sunfish, and 168 

mg/L in harlequin. (ExToxNet 2005.) Chronic toxicity studies with a terrestrial formulation of glyphosate, Roundup®, found no significant adverse effects on growth, carcinogenicity, feeding, and agonistic behavior in rainbow trout fingerlings. The authors concluded that sublethal levels of the formulation are relatively non-toxic. (Morgan & Kiceniuk 1992 in WS FEIS 1993.) A recent study with the aquatic formulation Rodeo® determined the LC50 for juvenile rainbow trout at 782 mg glyphosate a.e./L. 

Giesy et al. (2000) reviewed the data available on glyphosate toxicity to fish. Although 

some data were available for anadromous species, it appears that all tests were conducted 

using freshwater test methods. Acute toxicity LC50 values for glyphosate tested as isopropylamine salt ranged from 97 to greater than 1,000 mg/L and NOEC values ranged 

from <97 to 1,000 mg/L. Data compiled by Ebasco (1993) on one-day acute toxicity tests 

indicate EC50 values ranging from 12.8 mg/L to 240 mg/L. 

The lowest of these NOEC and LC50 values (12.8 mg/L) for glyphosate or glyphosate/surfactant mixtures is well above the maximum glyphosate concentration of 

0.026 mg/L reported by Paveglio et al. (1996) and the immediate maximum geometric 

mean glyphosate concentration of 0.174 mg/L reported by Patten (2002). Therefore, these 

data indicate that impacts to fish due to maximum post-application water concentrations 

of glyphosate are unlikely in experimental conditions. Impacts in estuarine conditions 

San Francisco Estuary Invasive Spartina Project 30. 2008 Aquatic Pesticide Application Plan 
with high concentrations of suspended sediment, which interfere with glyphosate activity, 

would be even less likely. 

Birds 

Imazapyr. Only few toxicity studies exist for birds. No adverse effects were noted at 

imazapyr concentrations of up to 5,000 ppm in the diet. Based on the highest doses tested 

and the U.S. EPA ecotoxicity categories (see attached Table A-5), these results suggest 

that imazapyr is moderately or less toxic orally to birds. No data exist for the potential 

toxicity of imazapyr to shorebirds. (Fletcher 1983a,b,c,d in SERA 2004.) No studies exist 

on toxicity to raptors or on preening or inhalation exposure potentials. 

Glyphosate. Effects of glyphosate on birds have been tested on mallard ducks (dabbling 

ducks which ingest wetland sediment along with seeds, insects, and vegetation) and bobwhite quail. Glyphosate is no more than slightly toxic to birds. Several single-dose acute 

oral studies indicate that glyphosate is practically non-toxic to upland birds and only 

slightly toxic to waterfowl. (U.S. EPA 1993.) As with mammals, very high dietary concentrations of glyphosate (a 4,640 mg/kg dietary concentration) resulted in no adverse 

reactions such as weight loss or mortality (Ebasco 1993). Chronic exposure studies with 

glyphosate determined a no-observed-effect concentration (NOEC) of 1,000 ppm in the 

diet. (Heydens 1991 in WS FEIS 1993.) Little or no data are available on toxicity of surfactants to birds. 

Mammals 

Imazapyr. Based on U.S. EPA ecotoxicity criteria, imazapyr is considered practically 

non-toxic to mammals via oral or dermal administration based on acute and chronic studies conducted with a variety of mammalian species. For example, the reported acute oral 

LD50 for technical imazapyr in rats is greater than 5,000 mg/kg body weight (b.w.) Rats 

were observed to rapidly excrete imazapyr in urine and feces with no residues detected in 

their liver, kidney, muscle, fat, or blood. No observable effect was noted for any formulation of imazapyr administered dermally. Very few inhalatory studies were performed and 

none tested concentrations high enough to determine acute toxicity. Inhalatory effects at 

sublethal concentrations (<5 mg/L aerosol) were found with technical grade imazapyr 

resulting in slight nasal discharge and congested lungs. Technical grade imazapyr and 

imazapyr isopropylamine salt were both found to be moderately irritating to rabbit eyes 

with complete recovery within 7 days. Technical grade imazapyr is reported as mildly 

irritating to rabbit skin. Commercial formulations of imazapyr appear to be less toxic via 

dermal exposure. (Entrix 2003, p. 42-44.) Chronic and subchronic toxicity studies with 

imazapyr with dogs, mice, and rats did not suggest any systemic toxic or carcinogenic 

effects. (SERA 2004.) 

Glyphosate. Glyphosate has been determined to be practically non-toxic to mammals by 

ingestion with an acute oral LD50 of 5,600 mg/kg b.w. in rats. The no-observed-effect 

level (NOEL) for chronic toxicity to rats has been determined at 362 mg/kg b.w./day 

(8,000 ppm) and LOEL at 940 mg/kg b.w./day (20,000 ppm). (USDA 1981; Monsanto 

1983; both in WS FEIS 2003.) The reported acute LD50 values for dermal effects range 

from >5,000 to 7,940 mg/kg for rabbits. Subchronic oral toxicity studies of glyphosate 

with rats and dogs indicate that oral does of up to 2,000 ppm do not significantly affect 

behavior, survival, or body weight. Laboratory studies of the chronic effects of glyphosate show that it is slightly to practically non-irritating to rabbits’ eyes. No significant 

San Francisco Estuary Invasive Spartina Project 31. 2008 Aquatic Pesticide Application Plan 
reproductive, teratogenic, mutagenic, or carcinogenic effects from exposure to concentrations of up to 300 ppm were reported in 20-year laboratory studies with rats, dogs, rabbits, and mice. 

Little is known about potential interactive effects between applied imazapyr or glyphosate/surfactant solutions and cumulative loads of herbicides, insecticides, detergents, 

perfume agents, and many other organic contaminants in the San Francisco Estuary. It is 

reasonable to assume that cumulative, interactive effects occur in organisms of the Estuary, but the complexity of multiple interactions in uncontrolled field conditions makes 

definitive research difficult. 

In practice, total dosages of imazapyr or glyphosate/surfactant solutions applied in field 

conditions (amount of solution applied, and concentration, and the number of reapplications to eradicate survivors) depends on many factors which are independent of 

the physiology of imazapyr, glyphosate or the surfactants themselves. The physiological 

activity and health of the plant, interference with spray coverage by persistent dead leaves 

or sediment films, all can affect the percent kill of vegetation, and the ability of regenerative buds to survive and re-establish the population. Regeneration requires re-application 

of herbicide or other eradication methods. 

7. DESCRIPTION OF ALTERNATE, NON-CHEMICAL CONTROL METHODS 

The Spartina Control Program implements a number of non-chemical control methods in 

situations where environmental impacts can be reduced, sites are appropriate for volunteer efforts and educational opportunities, or where public demand dictates. These methods are especially appropriate for small, newly establishing infestations and/or for some of 

the final cleanup of sites after control efforts have reduced the infestation down to small 

remaining patches. Non-chemical control methods are also a great way to engage the community around a site because they foster volunteer stewardship efforts and public outreach. 

During the development of the Site-Specific Plans for control of invasive Spartina around 

the Bay, the Spartina Control Program evaluated every possible known control method 

that could be used. A number of criteria were used in the evaluation including efficacy at 

controlling the Spartina, human health and safety, damage to the marsh habitat and/or 

other aspects of the environment, impacts on water quality, feasibility of applying the 

method in the salt marsh, cost, etc. Several non-chemical methods (hand-pulling and manual excavation, covering/blanketing, and mechanical excavation or dredging) have been 

incorporated into the Site-Specific Plans for 2008-2010. The remainder of the methods that 

were evaluated were found to have significant limitations, and are not part of the Spartina

Control Program’s current plans. However, some of these methods may be used in conjunction with our selected control methods at a later date. The entire set of possible control 

methods that were evaluated are discussed below, starting with the methods that were selected and incorporated into the plans. 

ISP-selected Non-chemical Control Methods 

Hand-pulling and manual excavation 

Manual removal methods are the simplest technology for removal of cordgrass. Manual 

removal includes pulling cordgrass plants out of marsh sediments or using hand tools 

such as spades, mattocks, or similar tools to cut away as much cordgrass as possible 

within reach. Manual removal methods are effective primarily at removing aboveground 

San Francisco Estuary Invasive Spartina Project 32. 2008 Aquatic Pesticide Application Plan 
plant parts, but are less effective at removing belowground rhizomes (the horizontal underground stem that sends out roots and shoots from buds) that rapidly regenerate shoots. 

Unless digging removes the entire marsh soil profile containing viable rhizomes and 

buds, its effect is equivalent to pruning (see Mowing, burning, pruning, and flaming, below). The vigor with which remaining rhizomes resprout and regrow is often proportional 

with the severity of the disturbance. Frequent re-digging and maintenance is needed to 

exhaust rhizome reserves of energy and nutrition, and the population of buds capable of 

resprouting. 

Manual removal is most effective on isolated seedlings, or very young discrete clones 

(asexually reproduced colonies of cordgrass) or clumps, where they are infrequent. Manual excavation in tidal marshes is extremely labor-intensive. Most cordgrass colonies occur in soft mud, where footing needed for digging is impossible or hazardous, even for 

workers on platforms, mats, or snowshoe-like boots adapted for walking on mudflats. 

Dug plants with roots left in contact with moist soil may retain viability and regenerate in 

place or disperse on high tides to establish new populations. 

As the invasive Spartina populations are reduced around San Francisco Bay, the ISP has 

increased its use of manual removal methods as part of an Integrated Pest Management 

strategy and a way to reduce the need for herbicide where appropriate. Manual removal is 

particularly useful on Spartina densiflora, the secondary invasive cordgrass species in the 

Estuary which is a discretely-rooted bunchgrass as opposed to the deeply-rooted rhizomatous clones of the main problem species, hybrid Spartina alterniflora. The infestations of 

S. densiflora occur mainly in Marin County with the exception of a few outlier populations in Contra Costa and San Mateo Counties. Many tons of S. densiflora will be removed manually in 2008. 

Disposal of manually removed material, especially root/rhizome systems, is problematic. 

On-site disposal in marshes may cause additional marsh disturbance and may result in 

spread of invasive cordgrass by regeneration of viable roots. Where manual removal occurs next to levees, salt ponds, or other non-tidal environments, local disposal may be 

feasible. Disposal of manually removed materials may also be accomplished with specialized low-ground-pressure equipment (amphibious vehicles), but the number of passes 

needed to transport materials also increases marsh disturbance. 

Mechanical excavation and dredging 

Mechanical removal in marshes uses equipment specially designed for working in semiterrestrial, semi-aquatic wetland environments. Excavation and dredging are accomplished using (1) amphibious dredges fitted with excavators, clamshells, or "cutterhead" 

dredges, or (2) excavators working from mats (large wood pile supports placed flat on 

geotextile fabric placed over the marsh surface). Some locations allow use of conventional shallow-draft, barge-mounted dredging equipment working within reach of marsh 

from the margins of navigable channels, particularly at high tide. Where cordgrass colonies lie within the limited reach of track-mounted excavators working from levees, mechanical removal also can be performed without entry of equipment to aquatic or wetland 

environments. 

Another mechanical technique is maceration or pulverization of soil and plant remains on 

site using modified agricultural equipment, "chewing" them into particles too small to be 

viable or regenerate. Floating maceration equipment has been used in inland waterways 

San Francisco Estuary Invasive Spartina Project 33. 2008 Aquatic Pesticide Application Plan 
to control submerged aquatic vegetation. The Control Program may support research and 

development of this method for use in the baylands environment, and would utilize this 

method if it were shown to be effective and reliable with mitigable impacts. 

Mechanical excavation working to the full depth of the rhizome system (up to 1 foot) in 

tidal marshes has the potential to be significantly more effective than manual excavation. 

Similarly, maceration techniques that almost completely destroy both aboveground and 

belowground living mass of cordgrass have high potential effectiveness. Both techniques 

also have significant limitations in the San Francisco Estuary, however. Excavators working from levees have an inherent limitation of short reach or access distance, usually a 

working distance of less than 20 feet for the size equipment that typical levees could bear. 

Floating barges with clamshell or cutterhead dredges, in contrast, would need to work at 

high tides within about 70 feet of the leading edge of cordgrass vegetation. Excavators 

have sufficient reach to dispose of excavated marsh soil and biomass in non-wetland areas, on levees, or in aquatic habitats such as salt ponds, which lack vegetation. 

Heavy equipment often is used within the Estuary's tidal marshes for purposes other than 

eradication of cordgrass, including removal of large debris hazards and contaminated materials, and construction or maintenance of ditches or canals. Most of this work is done on 

mats, to distribute the weight of equipment and protect underlying vegetation. These actions are usually aimed at operations that are highly localized (points or narrow alignments) 

in the marsh, and usually on the relatively firm marsh plain. Even there, equipment may 

become mired in soft spots, and removal of mired equipment can damage the marsh. In 

contrast, to maintenance-type work, removal of invasive cordgrass involves a mosaic pattern for operations, and occurs most often in the low marsh and mudflats, which do not easily support mats and geotextile fabrics. Thus, control methods based on excavators working 

on mats would be most applicable to localized, large patches of invasive cordgrass on the 

marsh plain. Some tidal flats invaded by cordgrass occur on sandy deltas with intertidal 

sand bars (e.g., San Leandro, San Lorenzo Creek) where equipment could be staged, but 

this situation is unusual. The feasibility of using mechanical excavation or dredging methods at a particular location would be determined based on site-specific conditions. 

Covering/blanketing 

This is another technique that is aimed at exhausting the reserves of energy and nutrition in 

cordgrass roots and rhizomes and increasing environmental and disease stress. Covering 

typically involves securing opaque geotextile fabric completely over a patch of cordgrass. 

This excludes light essential to photosynthesis (transformation of solar energy to food energy), and "bakes" the covered grass in a tent of high temperature and humidity. 

This technique may be used for discrete colonies (clones) where the geotextile fabric can 

be fastened to the marsh surface securely with stakes for a sufficiently long period of 

time. High tides, high winds, and tide-transported debris common in tidal marshes often 

make this difficult or impossible in some situations. Care must be taken to cover the entire clone to a distance sufficient to cover all rhizomes. If rhizomes spread beyond the 

reach of the blanketing cover, rhizome connections to exposed, healthy stems can translocate (pipe) foods to the stressed, starving connected portions of the clone under the fabric, and increase overall survival. Staking geotextile tents on soft mudflats is very difficult, and may make this method infeasible in many situations. 

San Francisco Estuary Invasive Spartina Project 34. 2008 Aquatic Pesticide Application Plan 
Wrack (piles or lines of drifted debris and detritus from tidal sources) also is capable of 

smothering cordgrass and other salt marsh plants. Wrack can be created artificially by 

placing temporary debris piles on the marsh surface, but cannot be stabilized for long 

(usually no longer than the highest December-January or June tides or winter storm 

surges). Their duration at any position in the marsh depends on the frequency and height 

of tides. The lower in the intertidal zone, the less stable the position of a wrack pile is 

likely to be. This technique would be used only for small colonies, and would depend on 

locally available accumulations of organic tidal debris. 

Other Non-chemical Methods Evaluated 

Mowing, burning, pruning, and flaming 

Cordgrasses are well adapted to disturbances that "crop" or otherwise remove aboveground biomass. A single event that removes living or dead aboveground cordgrass biomass generally stimulates cordgrass growth, and as soon as a cordgrass stand refoliates, it 

begins to "recharge" its roots and rhizomes with new food reserves. If vegetation is removed with frequency, roots and rhizomes are prevented from regenerating reserves of 

energy and nutrition and cordgrass begins to die back as its organs of regeneration and 

storage become exhausted. If the cordgrass is mown close to the mud surface, it also severs the connections between leaves and roots that transport gases to roots growing in extremely anoxic (oxygen-deprived) waterlogged sediment and further stress the plant. 

Repeated close mowing may be used to increase physiological stress to a point that 

cordgrass cannot regenerate; frequent burning would have similar effects. The use of 

pruning, burning, and mowing for cordgrass eradication in open mudflats and marshes 

would require very frequent treatment of all aboveground growth until the cordgrass rhizome/root systems become exhausted. For robust stands of Atlantic smooth cordgrass, 

this may require weekly treatment for more than one growth season. 

Controlled burning may be used in some situations to remove vegetation prior to other 

treatments, or to prevent pollen and seed dispersal in founder colonies invading new sites. 

Burning would be used only in suitable locations, and only during periods of low-wind 

conditions (especially early morning), when fire hazards in succulent vegetation of tidal 

pickleweed marshes would be manageable. Ignition, however, may be difficult in 

cordgrass stands on mudflats. 

Selective pruning (partial mowing with "weed-whackers" or flaming with hand torches) 

may be used to remove flowerheads and seedheads of discrete colonies to prevent flow of 

pollen from contaminating seed production of native cordgrass, and to prevent seed production within founding colonies. However, pruning would have little or no effect on the 

clone's growth rate and must be followed up with other methods to control spread. 

Mown vegetation without viable seeds or propagules may be left in place or removed 

from the site. Vegetation containing viable seeds or propagules would require removal 

from the treatment site and disposal in a suitable area not conducive to cordgrass growth. 

Crushing and mechanical smothering 

This method uses amphibious track vehicles to trample new plant shoots and stems, and 

cover them with a layer of sediment. The objective is to smother the plant by preventing 

the use of stems to transport oxygen to its roots and rhizomes. The method would typically be used in the fall, and ideally a period of time after mowing, when young shoots 

San Francisco Estuary Invasive Spartina Project 35. 2008 Aquatic Pesticide Application Plan 
and stems have developed. This method has been used with some success in Washington 

State, but has not yet been used in the San Francisco Estuary. 

Flooding and draining 

Flooding and draining techniques entail constructing temporary dikes or other structures 

to impound standing water or remove water to kill emergent vegetation. Cordgrasses are 

intolerant of permanently flooded or stable, dry conditions, and are generally absent in 

the diked nontidal salt marshes of the Estuary. Salt evaporation ponds, managed waterfowl ponds, and completely diked pickleweed marsh exclude cordgrasses, native and 

non-native alike. Atlantic smooth cordgrass and English cordgrass are capable of invading tidal marsh pools (salt pans) subject to irregular tidal influence (Campbell et al. 1990, 

P. Baye, pers. observ.), but they are not likely to survive in typical diked wetlands. 

When tidal marshes are diked and drained rather than flooded, they undergo rapid physical and chemical changes. Organic matter decomposes when microbes are exposed to air; 

clays shrink when dewatered; and sulfides formed in oxygen-free mud transform to sulfates forming strong acids (Portnoy, 1999). Therefore, diking and draining, although conceivably effective for killing cordgrass, would adversely impact marsh soils and restoration, and the longer salt marsh soils are diked and drained the more difficult these adverse 

soil changes are to reverse. For these reasons, diking and draining only would be used in 

critical situations where no other method is feasible, and only after careful evaluation and 

planned mitigation. Diked salt marsh soils that remain permanently flooded undergo relatively slower and less significant changes. Diked flooded salt marshes would eliminate 

existing standing vegetation, but are readily re-colonized by youthful salt marsh vegetation if the diking is brief. 

Isolating the treatment area for flooding or draining may be accomplished by constructing 

temporary dikes or by closing openings in existing dikes. Temporary constructed dikes 

need not be large to accomplish treatment. Low earthen berms (about one foot above 

marsh plain elevation), constructed using low-ground pressure amphibious excavators, 

could be built around large colonies of cordgrass within open marsh plains. Alternatively, 

water-filled geotextile tubes ("inflatable dams"), analogous with inflatable cofferdams 

used in aquatic construction/dewatering operations, may be used. Upon completion of 

treatment, berms would be graded down to marsh surface elevation, and inflatable dams 

removed. Temporary dike structures may be difficult to construct in tidal mudflats. Mudflat sediments are usually too soft to "stack" into berms, and firmer material placed on 

fluid or plastic muds simply subsides into the flats. Similarly, inflatable dams may not be 

feasible for softer tidal flats. 

Many populations of non-native cordgrasses have invaded marshes restored by breaching 

dikes within former diked baylands, where most of the original dikes remain. In these 

situations, a dike-enclosed tidal marsh could be temporarily re-closed ("choked") by placing a sheetpile barrier in the existing breach, thus creating a temporary lagoon and effecting mass cordgrass eradication. Water control structures (adjustable tidegates) may be 

installed to enable marsh managers to maintain water depths lethal to cordgrass, suitable 

diving duck habitat, and adequate water quality. Marsh recolonization is expected to proceed rapidly following restoration of tidal flows. 

An alternative form of treatment, intermediate between flooding and draining, would be 

to combine impoundment of water with deliberate solar evaporation, creating hypersaline 

San Francisco Estuary Invasive Spartina Project 36. 2008 Aquatic Pesticide Application Plan 
lagoons. Hypersaline conditions would make the habitat transformation even more rapidly lethal for invasive cordgrass. Restoring tidal flows to temporary salt ponds, however, 

may require dilution of brines, which could increase cost. 

8. HERBICIDE APPLICATION AREAS FOR 2008-2010 

Twenty-five sites, comprising 166 sub-areas and approximately 300 acres of non-native 

Spartina, are slated for control during the 2008 Spartina Treatment Season (Figure 3), and 

150 of these infestation sites will potentially be treated with herbicide for at least a portion 

of their control work. Most of these sites are being re-treated for the second or third year, 

hence the significant reduction in treatment area from 2,000 acres in 2006. Aquatic herbicide was determined to be the most efficacious, feasible, and least impactful method for 

Spartina control following a thorough evaluation of the available control methods described above. Each site has been evaluated taking into account many factors including site 

access, endangered species issues, habitat sensitivity, the infestation’s susceptibility to nonchemical control methods, partner involvement, public comment, and other factors. A brief 

description of each site follows including the herbicide delivery systems(s) to be used and 

an identification of the ISP Partner involved in treatment work on the site. Detailed maps of 

the each site can be found in Appendix 2. 

Site 01 – Alameda Flood Control Channel, Alameda County 

The Alameda County Flood Control Channel (ACFCC) is a large, unlined, trapezoidal 

channel that runs from east to west through Hayward, Alameda County, draining a nearly 

800 square mile watershed into the San Francisco Bay. The levees on both sides of the 

ACFCC are topped with multi-use public trails that are part of the San Francisco Bay 

Trail and Coyote Hills Regional Park. Downstream from Ardenwood Blvd., beyond the 

levees to the north, are both active and inactive commercial salt ponds, with an industrial 

facility and parking lot along the furthest upstream levee. To the south are active salt 

ponds, seasonal wetlands, and Coyote Hills Regional Park. There are currently no housing units, schools or other similar facilities within this lower reach. 

The combined infestation of the six sub-areas of the Alameda Flood Control Channel 

comprised one of the largest Spartina alterniflora hybrid infestations in San Francisco 

Bay. The ISP's 2004 mapping effort estimated a total of roughly 200 contiguous acres of 

S. alterniflora/ hybrids on this site spread over approximately 470 acres (43%) of salt 

marsh and tidal mudflats. The treatments from 2005 -2007 have reduced the infestation 

by at least 85%. The primary treatment method at this site is aquatic herbicide, which will 

be applied by helicopter, conventional spray truck, and tracked amphibious vehicle. Partners on this site include the Alameda County Flood Control District and the California 

Wildlife Foundation. Note that this is a complex site composed of multiple sub-areas. 

Please refer to the Site Specific Plan for detailed descriptions of the sub-areas and the associated treatment methods. 

Site 02 – Bair & Greco Island Complex, San Mateo County 

The Bair & Greco Island complex encompassed by this plan is located in the southwest 

portion of the San Francisco Bay Estuary. The northern edge of the complex is at Belmont Slough on the border of Foster City and Redwood City, including the marshes of 

Brewer Island just south of the San Mateo Bridge. The southern border of the complex is 

the Union Pacific railroad line just south of the Dumbarton Bridge. The site includes 

San Francisco Estuary Invasive Spartina Project 37. 2008 Aquatic Pesticide Application Plan 
Figure 3. Location of 2008-2010 Spartina Treatment Sites within the San Francisco Estuary and adjacent 

Outer Coast marshes. Each treatment site is comprised of one to 23 sub sites, which are identified by 

letters (a through z) in project plans and documents 

marsh islands, active and inactive commercial salt ponds, six large sloughs with numerous smaller channels, and other bay front marsh that is part of the San Francisco Don 

Edwards National Wildlife Refuge (DENWR). 

The Bair & Greco Island complex contains many different marsh systems, all of which 

are impacted to varying degrees by Spartina alterniflora hybrids. Of the roughly 3,060 

acres of Baylands within the complex, there were approximately 216 acres (7%) infested 

with non-native Spartina in 2005. Three years of effective herbicide treatments in this 

complex leave less than 50 acres to treat/retreat in 2008. Three sub-areas were added to 

this complex for the 2008-2010 Site-Specific Plans, one along Redwood Creek and the 

San Francisco Estuary Invasive Spartina Project 38. 2008 Aquatic Pesticide Application Plan 
Deepwater Slough with a few acres of hybrid Spartina, and two areas that are soon to be 

opened to tidal inundation but are not yet infested. The primary treatment method at this 

site is aquatic herbicide, which will be applied by helicopter, conventional spray truck, 

backpack sprayer, tracked amphibious vehicle, and boat. Partners on this site include the 

U.S. Fish and Wildlife Service, Don Edwards National Wildlife Refuge and the San 

Mateo County Mosquito Abatement District. Note that this is a complex site composed of 

multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the 

sub-areas and the associated treatment methods. 

Site 03 – Blackie’s Pasture, Marin County

Blackie’s Pasture is a small City of Tiburon park located along the shoreline of Richardson Bay, adjacent to Tiburon Boulevard. With the ample parking provided at the park, it 

is heavily used by the public for passive recreation. The park is comprised of a 0.7-acre 

pasture, a small creek channel (“Blackie’s Creek”) along the eastern edge of the pasture, 

and a shoreline area that includes the channel mouth, a small open mudflat (fed by sediment delivered by the creek), and landscaped pathways and picnic areas. The total area of 

non-native Spartina at the Blackie’s Pasture site was around 0.8 acre in 2005, divided 

between two sub-areas. This has been reduced to several hundred square feet that will be 

treated in 2008. The upper portion of this site is represented by the Blackie’s Creek Channel (Sub-Area 3a), wherein Spartina alterniflora hybrids dominated what was previously 

an open channel. Spartina densiflora and Spartina alterniflora hybrids dominated the 

mouth of Blackie’s Creek (Sub-Area 3b), readily hybridizing with the native Spartina 

foliosa stand there. Some excavation of the upper channel occurred in 2005 as part of a 

restoration project, but only the invasive Spartina in the center of the creek was actually 

removed; the remainder was treated in 2006. The primary treatment method at this site is 

aquatic herbicide, which will be applied by backpack sprayer. Removal of young S. densiflora plants will be done manually with the plants taken off site for disposal. Partners on 

this site include the City of Tiburon Public Works and the Tiburon Audubon Society. 

Site 04 – Corte Madera Creek Complex, Marin County 

The Corte Madera Creek complex is located on the west side of the North San Francisco 

Bay in Marin County, south of the San Quentin peninsula and San Rafael Bay. The complex consists of a wide corridor stretching upstream from the mouth of Corte Madera Creek 

to the uppermost point of non-native Spartina growth in this watershed at about 2.2 miles 

from the mouth. The entire Corte Madera Creek corridor is heavily developed with upscale 

residential and commercial facilities. The Corte Madera Creek complex is comprised of 11 

distinct sub-areas that occur on both public and private lands, each of which will require 

different treatment and public outreach approaches. 

The infestation at the Corte Madera Creek complex was still in a relatively early stage of 

establishment, with approximately 12 acres scattered over 318 acres, or 4% of the total 

marsh area. The infestation at this complex contains some unique features, including the 

only infestation of Spartina anglica in the Bay, as well as the first documented case of 

Spartina densiflora hybridizing with the native Spartina foliosa. Most of the sub-areas 

have small S. densiflora infestations (less than 0.5 acre), enabling manual control to be 

used in conjunction with spot herbicide treatments. One sub-area also has Spartina alterniflora hybrids, bringing the overall site total to three of the four invasive cordgrass 

species currently found in the Bay. 

San Francisco Estuary Invasive Spartina Project 39. 2008 Aquatic Pesticide Application Plan 
The Marin Conservation Corps conducted a great deal of manual removal throughout the 

winters from of 2005-2008, and this method was highly effective. A few of the sites that 

were controlled by herbicide in 2007 will be revisited this season to manually pull/dig the 

few plants that have resprouted or emerged from the seedbank, while any healthy 

Spartina densiflora plants will be treated with imazapyr. Partners on this site include the 

Friends of the Corte Madera Creek Watershed, California Department of Fish and Game, 

California State Lands Commission, College of Marin, City of Larkspur, Golden Gate 

Bridge Highway and Transportation District, Marin County Parks and Open Space District, and the Marin County Flood Control and Water Conservation District. Note that this 

is a complex site composed of multiple sub-areas. Please refer to the Site Specific Plan 

for detailed descriptions of the sub-areas and the associated treatment methods. 

Site 05 – Coyote Creek & Mowry Slough Area, Santa Clara County 

The area encompassed by this Site-Specific Plan includes approximately 3,652 acres of 

marshland within the San Francisco Don Edwards National Wildlife Refuge that lie between Coyote Creek to the south and the Dumbarton Bridge to the north. The site is surrounded entirely by marsh and salt ponds, and there is very little public access, except for 

a portion of the Bay Trail along part of Newark Slough (Sub-Area 5c). Within this area, 

the sub-areas include recently restored tidal marshes, freshwater ponds and upland islands, highly complex and diverse historic marsh habitats that include channels, high 

marsh, mudflats and pans, thin strip marshes, open mudflats, creek channels and mouths, 

and sandy beach areas. 

The pioneering infestation of Spartina alterniflora hybrids in the Coyote Creek and Mowry 

Slough complex is still very limited in its distribution. However, though the acreage is still 

relatively small, the clones are distributed throughout the habitat types described above. In 

sum, these infestations covered approximately 15.3 acres in 2005 scattered over this very 

large marshland complex, which is equal to just 0.4% of the area. Much of this area was 

treated for the first time in 2006 using a directed herbicide application tool (spray ball) that 

the ISP developed with PJ Helicopters of Red Bluff, CA. The results from 2007 treatment 

were less efficacious and several of these areas need to be treated by broadcast aerial application in 2008. The primary treatment method at this site is aquatic herbicide, which will be 

applied by broadcast from helicopter, conventional spray truck, backpack sprayer and 

tracked amphibious vehicle. The partner on this site is the U.S. Fish and Wildlife Service, 

Don Edwards National Wildlife Refuge. Note that this is a complex site composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the subareas and the associated treatment methods. 

Site 06 – Emeryville Crescent, Alameda County 

The Emeryville Crescent marsh is a 103.5-acre, fringing mixed pickleweed (Salicornia 

virginica) marsh shoreline between Powell Street in Emeryville and the eastern landfall 

of the Oakland Bay Bridge. Two sub-areas, Emeryville Crescent East (6a) and Emeryville Crescent West (6b), have been delineated due to the historical ownership and maintenance of the site. The site abuts an extremely heavily developed area on the east side of 

the Bay, with Interstate 80/580 directly adjacent to the east, and the approach to the San 

Francisco Bay Bridge adjacent to the south. Local anglers, dog-walkers, and other recreational groups frequently use the marshlands included in this site. Illegal activities such as 

dumping and littering, unauthorized camping, and public inebriation also occur along the 

edges of, and sometimes within, the marshlands of this site. 

San Francisco Estuary Invasive Spartina Project 40. 2008 Aquatic Pesticide Application Plan 
The non-native Spartina infestations at Emeryville Crescent were in the early stages of 

establishment on the site. The individual locations of these plants were scattered across 

both of the sub-areas, but their overall acreage was small in 2005, at less than 2.6 acres or 

2.5% of the combined marsh acreage. The infestation is located mainly along the bay 

edge of the marsh, adjacent to the open mudflats on the outer edge of the site, with a few 

scattered clones establishing on the interior portions of the marsh within Sub-Area 6b. 

Treatment in 2008 will be needed on less than 1000 square feet after three years of successful applications. The primary treatment method at this site is aquatic herbicide, which 

will be applied by conventional spray truck, backpack sprayer, and tracked amphibious 

vehicle. Partners on this site include the California Department of Parks and Recreation 

and the East Bay Regional Parks District. 

Site 07 – Oro Loma Marsh, Alameda County 

Oro Loma Marsh is a large, 324-acre, recently restored salt pond located on the eastern 

shore of the San Francisco Bay Estuary adjacent to the town of San Lorenzo, about 1.5 

miles south of the Metropolitan Oakland International Airport. The marsh is surrounded 

by levees, with Bockmann Channel and Sulfur Creek bordering the marsh to the north 

and south respectively. The San Francisco Bay Trail, a multi-use public recreational 

pathway, utilizes the levee to the west of Oro Loma, and the Southern Pacific Railroad 

borders the marsh to the east. The surrounding area includes various industrial and commercial developments to the north and south including a sewage treatment plant, electrical substation, and capped landfill. Beyond the railroad to the east are residential developments, the Skywest Golf Course, and Hayward Municipal Airport, with I-880 approximately 0.5 mile from the marsh edge. 

The entirety of the Oro Loma Marsh site was infested with Spartina alterniflora hybrids 

across both Sub-Areas prior to the very successful helicopter treatment in 2005, totaling 

approximately 100 acres (31% of the marsh). This was one of the largest infestations of 

S. alterniflora hybrids in the eastern Central Bay, and was adjacent to several other large 

infestations including sites along the San Leandro/ Hayward shoreline. Successful helicopter treatments occurred in 2006 & 2007, but there are still scattered clusters of 

Spartina throughout that will be treated in 2008. The primary treatment method at this 

site is aquatic herbicide, which will be applied by helicopter on the remaining stands. The 

partner on this site is the East Bay Regional Parks District. 

Site 08 – Palo Alto Baylands, Santa Clara County 

The Palo Alto Baylands is a 1,030-acre nature preserve and park complex owned by the 

City of Palo Alto and located on the bayfront south of the Dumbarton Bridge. The site 

includes those areas to the north and south of Charleston Slough, and may extend to the 

northernmost tip of marshland on the southeast portion of the outlet of Charleston Slough 

– that land within the city limits of Palo Alto. The site is part of a large expanse of intact 

native Spartina foliosa and pickleweed (Salicornia virginica)/gumplant (Grindelia sp.) 

marsh habitat. The park has high visitation on the established pathways through the 

marsh, and serves as an educational center for birdwatchers, naturalists, local schools, 

and the public. Other recreational users of the preserve include hikers, kayakers, anglers, 

bikers, joggers and many others. 

The pioneering infestation of S. alterniflora hybrids on this site covered approximately 

one acre in 2005, scattered along the bayfront, mostly south of the Baylands Nature InSan Francisco Estuary Invasive Spartina Project 41. 2008 Aquatic Pesticide Application Plan 
terpretive Center. Treatment from 2005-2007 has reduced this infestation by approximately 90%. There are several main areas of infestation: the southeast side of the "Yacht 

Club Bay" near Mayfield Slough, clones near Hooks Point and Hooks Island, and scattered plants along the bayfront from Mayfield Slough to Charleston Slough. The primary 

treatment method at this site is aquatic herbicide, which will be applied by conventional 

spray truck, backpack sprayer, and boat. Partners on this site include the City of Palo Alto 

and Palo Alto High School. 

Site 09 – Pickleweed Park, Marin County 

Pickleweed Park is an 18-acre City of San Rafael Park located on the edge of San Rafael 

Bay in the northwestern San Francisco Bay Estuary. It is bounded to the north by San 

Rafael Creek and to the south by East Canal Street. Bordering the park on the east side is 

the 10-acre Tiscornia Marsh, a thin band of high marsh pickleweed/gumplant habitat, 

which grades abruptly from a 2 to 3 foot-high escarpment to an extensive mudflat extending bayward. This band of marshland tapers as it extends southward along the park 

boundary, and becomes very thin as it curves eastward along the riprap of a levee surrounding an area filled for development. There is an east/west wooden service walkway 

through the marsh that provides access to the Pacific Gas and Electric (PG&E) power line 

tower adjacent to the site. 

There is an establishing population of Spartina densiflora within the fringing marshlands 

of the park. These plants are at their greatest density in the marsh near the outlet of San 

Rafael Creek. The plants form a dense stand on the Bay edge surrounding the escarpment, near an electrical tower. Scattered plants extend southward from this main area 

along the Bay edge, and then east and southeast to Shoreline Park. The total infestation 

size of S. densiflora on the site was approximately 0.05 acres (2200 ft2). In spring 2005, a 

pioneering infestation of S. alterniflora/ hybrid was also discovered just south of the 

PG&E walkway. Treatment from 2005-2007 has been highly effective and just a handful 

of plants will need to be treated in 2008. The primary treatment method at this site is 

manual removal of all S. densiflora, with very limited aquatic herbicide application by 

backpack sprayer to an established patch of hybrid S. alterniflora in one of the channels. 

Partners on this site include the Tiscornia Estate Company and City of San Rafael. 

Site 10 – Point Pinole Regional Shoreline, Contra Costa County 

Point Pinole Regional Shoreline is a 2,315-acre park owned by the East Bay Regional 

Parks District. It is located to the west of the city of Richmond, in Contra Costa County. 

Point Pinole opened to the public in 1973 after the property was acquired from Bethlehem Steel. Bethlehem had acquired the land in the early 1960s from Atlas Powder Co., 

one of several firms that had manufactured gunpowder and dynamite there for almost 100 

years. The park occupies a short peninsula composed of a main upland core with open, 

grassy parklands interspersed with predominantly eucalyptus woodlands. Along the 

northern portion of the park, a wide border of high marsh pickleweed characterizes Whittell Marsh, Sub-Area 10a. The southern portion of the park, Sub-Area 10b is a narrow 

band of tidal marsh grading quickly over a 10-20 meter span from high marsh pickleweed 

to sandy mudflat. A new Sub-Area 10c was added this year with EBRPD’s acquisition of 

Giant Marsh. 

The non-native Spartina infestations at Point Pinole were in the early stages of establishment. The individual locations of these plants are scattered within the Sub-Areas, but 

San Francisco Estuary Invasive Spartina Project 42. 2008 Aquatic Pesticide Application Plan 
their overall acreage is small. The addition of Giant Marsh added infestation areas that 

have not yet been treated until 2008. The primary treatment method at this site is aquatic 

herbicide, which will be applied by backpack sprayer. The partner on this site is the East 

Bay Regional Parks District. 

Site 11 – Southampton Marsh, Solano County 

Southampton Marsh is the largest extant marsh within the Carquinez Strait. Its roughly 

175 acres are located within the 720-acre Benicia State Recreation Area, Solano County. 

Highway 780 borders the park on the north and east, Southampton Bay on the south, and 

on the west stands the residential development of Vallejo. Cyclists, runners, walkers and 

roller skaters use the park’s 2.5 miles of road and bike paths, which circle the perimeter 

of the park. The Marsh lies in the central portion of the park, and consists mostly of high 

marsh pickleweed/gumplant habitat, with a deep main channel and several smaller channels throughout. Cordylanthus mollis ssp. mollis (soft bird’s-beak), an endangered plant 

species, can be found in some of the high marsh areas of the site. Access to the marsh is 

restricted to park personnel and researchers to protect the C. m. mollis populations from 

potential damage caused by trampling. 

Southampton Marsh contains the only known population of Spartina patens in the San 

Francisco Estuary. Several large clones are scattered throughout the southern and western 

portions of the marsh, and multiple smaller clones are peppered throughout the area. A 

number of S. patens clones are adjacent to the main channel draining the marsh. There 

was a total of roughly 0.5 acre of S. patens at this site in 2005, which has reduced by herbicide applications in the areas that are not contiguous with Cordylanthus.. Some of the 

areas occupied by S. patens are directly adjacent to, or interspersed with individuals or 

patches of Cordylanthus. These areas are highly sensitive, and any S. patens eradication 

effort here will require diligent protection efforts for the C. m. mollis. For 2008, treatment 

will occur on only a few hundred square feet, mostly composed of S. patens seedlings. 

The primary treatment method at this site is aquatic herbicide, which will be applied by 

backpack sprayer. The partner on this site is the California Department of Parks and Recreation. 

Site 12 – Southeast San Francisco, San Francisco County 

The Southeast San Francisco complex includes a scattered group of remnant marshlands 

totaling 56.7 acres within a heavily industrialized landscape on the western shores of the 

San Francisco Bay Estuary. The complex is bounded by the Islais Creek Channel and 

Pier 94 on the north, and the San Francisco County and City boundaries to the south. The 

Southeast San Francisco complex is adjacent to an inactive naval shipyard, shipping container facilities, and 3Com Park stadium (formerly Candlestick Park), as well as the Bayview residential neighborhood of San Francisco. Within this area there are a number of 

marshland habitats including intertidal mudflats, native Spartina foliosa stands, riprap 

shoreline, marshland fill, and pickleweed-dominated tidal marsh plain. 

The six sub-areas of the Southeast San Francisco complex contained approximately 8.2 

acres of Spartina alterniflora hybrids in 2005. This represents 14.5% of the area of these 

fragmented remnant marshlands. The rapid hybridization of this population, and conversion of these last pieces of remnant marsh in the area, lends a sense of urgency to the control efforts outlined in this plan. The individual patches of non-native Spartina within this 

area represent localized ‘stepping stones’ in the available marsh habitat of the area to the 

San Francisco Estuary Invasive Spartina Project 43. 2008 Aquatic Pesticide Application Plan 
open waters of the North Bay, and the outer coast. Two sub-areas were added to this 

complex following the discovery of these small infestations. Treatment occurred at most 

of these sites in 2006 & 2007, reducing the area to approximately 3 acres needing treatment in 2008. The treatment methods at this site include a combination of manual digging, covering with geotextile fabric, and application of aquatic herbicide by conventional spray truck or backpack. Partners on this site include the California Department of 

Parks and Recreation, Literacy for Environmental Justice (LEJ), Port of San Francisco, 

Golden Gate Audubon, City of San Francisco Recreation & Parks, and the U. S. Navy. 

Note that this is a complex site composed of multiple sub-areas. Please refer to the Site 

Specific Plan for detailed descriptions of the sub-areas and the associated treatment 

methods. 

Site 13 – Whale’s Tail / Old Alameda Creek Complex, Alameda County 

The Whale’s Tail and Old Alameda Creek Complex is a 564-acre site on the eastern 

shores of the San Francisco Bay Estuary, south of the San Mateo Bridge and bordered to 

the east by Union City. This area includes remnant marshland patches that predate alterations to the site for salt production, channelized flood control structures, restored salt 

pond marshland, small sinuous channels, high marsh flats, mudflats, eroding scarp, 

sand/shell beach, small depositional deltas, and other habitats. The areas included within 

this complex are entirely restricted from public access and are either managed by California Department of Fish and Game (CDFG) as wildlife habitat (Sub-Areas 13d, 13e, 

13f), or by Alameda County Flood Control District for flood control purposes (Sub-Areas 

13a, 13b, 13c, 13g). On the northern side of the main channel, formerly diked salt ponds 

are undergoing restoration activities to convert them to tidally influenced marshlands. To 

the south of the main channel, Cargill Corporation maintains active salt-producing evaporator ponds. 

The invasive Spartina at the Whale’s Tail and Old Alameda Creek Complex is one of the 

oldest infestations of non-native cordgrass in the San Francisco Estuary. The marshlands 

of this site contained a total of 82 acres of Spartina alterniflora hybrids representing 

14.5% of the area. Applications from 2005 -2007 were very effective, reducing the area 

to be treated in 2008 to less than 10 scattered acres, mostly in channels and other low elevation areas. The infestations are establishing in a wide variety of marsh habitats including high marsh pickleweed (Sarcocornia virginica)/saltgrass (Distichlis spicata), lower 

marsh Spartina foliosa/mudflat areas, channel banks, edges of salt pans, and bayfront 

scarps and mudflats. 

Since the Cargill Mitigation Marsh was a former salt evaporator pond, it was largely unvegetated with native salt marsh species when tidal action was partially restored in 1995. 

Without any biotic resistance to invasion, the marsh has become infested with large, coalescing clones of invasive Spartina. On the eastern portion of the site, these clones have 

coalesced into meadows. The Cargill Mitigation Marsh sub-area contained approximately 

19.0 acres of S. alterniflora hybrids, representing 38.8% of this restoration site in 2005. 

Treatment over the past three years has reduced the infestation substantially, with only a 

couple acres near the breach left to treat in 2008 because of low efficacy from 2007. 

The primary treatment method at this site is aquatic herbicide, which will be applied by 

helicopter, with some follow up with tracked amphibious vehicle if necessary. Partners 

on this site include the Alameda County Flood Control District, California Department of 

Fish and Game, and the California Wildlife Foundation. Note that this is a complex site 

San Francisco Estuary Invasive Spartina Project 44. 2008 Aquatic Pesticide Application Plan 
composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the sub-areas and the associated treatment methods. 

Site 15 – South San Francisco Bay Marshes, Santa Clara County 

The South Bay Marshes are located at the extreme southern tip of the San Francisco Bay, 

with both San Mateo and Alameda Counties bordering to the northwest and northeast, 

respectively. The area includes over 100 miles of shoreline, and encompasses some 1,750 

acres of marshland. This highly diverse area includes extensive current and former salt 

ponds, restoration marshes, creek channels and sloughs, bay fill, large intact salt marshes, 

brackish marsh areas, slough edge marshes, pans, islands, mudflats, sand/shell beaches 

and other marsh habitats. Included within this area are Guadalupe Slough, Coyote Creek, 

Alviso Slough, Mountain View Slough and San Francisquito Creek. There is a high degree of complexity in the South Bay Marshes that will be enhanced significantly by the 

work of the South Bay Salt Ponds Restoration Project, which will convert sizable portions of former salt-making ponds to various types of marsh habitat. 

The infestation was approximately 8 acres in 2005, but it had expanded rapidly over the 

past several years despite the effectiveness of imazapyr, largely due to the cryptic hybrids 

and post-September 1 treatment. The majority of the infestation occurs in the area of 

Knapp Tract, on Alviso and Guadalupe Sloughs, and along the bayfront adjacent to the 

DENWR newly acquired ‘salt ponds’ A1 and A2W. Both Pond A1 and A2W marshes are 

composed of large expanses of intact native Spartina foliosa (California cordgrass) and 

pickleweed (Sarcocornia virginica), interspersed with gumplant (Grindelia stricta) and 

tule (Scirpus sp.) Both marshes lie adjacent to compacted earthen levee roads, which are 

gated, locked, and require DENWR permission to access. The other sites are patchy and 

scattered throughout the South Bay extending from San Francisquito Creek in the northwest to the Coyote Slough tidelands in the northeast. The primary treatment method at 

this site is aquatic herbicide, which will be applied by helicopter broadcast in the case of 

the newly discovered areas, or by conventional spray truck and backpack sprayer. Partners on this site include the Santa Clara Valley Water District and the U.S. Fish and 

Wildlife Service, Don Edwards National Wildlife Refuge. 

Site 16 – Cooley Landing, San Mateo County 

Cooley Landing is a 165-acre salt marsh restoration site located at the northwestern point 

of the South San Francisco Bay Estuary, south of the Dumbarton Bridge and adjacent to 

the point where the Hetch-Hetchy Aqueduct makes landfall on the western shore at 

Menlo Park. The site is a former salt production evaporator pond that is undergoing restoration to tidal marsh. Initial restoration activities were completed between September and 

December of 2000, and included the excavation of two breaches through the east levee at 

locations of historic tidal channels. Re-vegetation of the former salt pond is expected to 

occur through natural colonization. Performance criteria for the restoration of Cooley 

Landing requires 70 percent cover of salt marsh vegetation and less than five percent 

cover of non-native vegetation by the tenth year following restoration. Cooley Landing is 

part of the Ravenswood Open Space Preserve. 

Prior to opening Cooley Landing to tidal action in 2000, just five adult clones of invasive

Spartina covering a total of 0.1 acre were present along the levees outboard of the restoration area. However, since S. alterniflora hybrids are known to occur on the adjacent 

properties north and south of the restoration area, and restored salt ponds lack the biotic 

San Francisco Estuary Invasive Spartina Project 45. 2008 Aquatic Pesticide Application Plan 
resistance in the form of an established native plant community, the infestation spread 

rapidly and already covered 20.0 acres of the restoration site or 13 % of this large area by 

2005. Treatment in 2006 & 2007 over a portion of the site has reduced the infestation by 

50%, but a significant amount of hybrid Spartina will be treated in 2008. The primary 

treatment method at this site is aquatic herbicide, which will be applied by helicopter 

with some follow-up with backpacks, Argos, or conventional spray truck. Partners on this 

site include S.S. Papadopoulos Associates and the Midpeninsula Regional Open Space District, as well as San Mateo County Mosquito Abatement District. 

Site 17 – Alameda Island / San Leandro Bay Complex, Alameda County 

The area encompassed by this Site-Specific Plan includes all marshlands of the Alameda 

and San Leandro Bay Area extending from the western tip of Bayfarm Island and San 

Leandro Channel in the west, to east of Interstate 880 and the Oakland Coliseum in the 

east. The northern boundary of the site is the Port of Oakland shipping terminals, and the 

southern edge is 98th Ave on San Leandro Creek. This area supports many diverse habitat types despite the fact that it is directly adjacent to some of the most highly developed 

land on the west coast. Within this area there are recently restored tidal marshes, freshwater ponds and upland islands, highly complex and diverse historic marsh habitats that include channels, high marsh, mudflats and pans, thin strip marshes along rip-rapped shoreline, public parks and trails, open mudflats, creek channels and mouths, sandy beach areas, marinas, private residences, commercial areas, industrial manufacturing facilities, 

shipping, and many other land use types. 

The Spartina infestations within this site are distributed throughout the habitat types described above. Most notably, Arrowhead Marsh, Fan Marsh and the Elsie Roemer Bird 

Sanctuary support the largest infestations of Spartina in the Alameda and San Leandro 

Bay Complex. In sum, the shoreline of this site contained 88.5 acres of non-native 

Spartina in 2005 targeted for control. This infestation was rapidly expanding into new 

areas, including the restored marshlands of the Martin Luther King Jr. Wetlands Project. 

Treatment from 2005 -2007 has reduced this infestation to approximately 35 acres. The 

primary treatment method at this site complex is aquatic herbicide, which will be applied 

by conventional spray truck, backpack sprayer, amphibious tracked vehicle, boat, and 

helicopter. EBRPD will conduct some “chemical mowing” at Arrowhead, using a low, 

sub-lethal rate of imazapyr applied by helicopter to stop the plants from setting seed but 

preserve them as refugia for the large California clapper rail population at this site. Partners on this site include the Alameda County Flood Control District, East Bay Regional 

Parks District, City of Alameda, City of Oakland, Port of Oakland, U.S. Coast Guard, 

Save the Bay, and Golden Gate Audubon. Note that this is a complex site composed of 

multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the 

sub-areas and the associated treatment methods. 

Site 18 – Colma Creek / San Bruno Marsh Complex, San Mateo County 

The area encompassed within this Site-Specific plan includes all of the marshlands north 

of the San Francisco International Airport, up to the northern tip of the outlet of San 

Bruno Canal or Colma Creek. Within this area there are broad marshlands fringing the 

industrial fill of South San Francisco, channel bank marshland habitat, open mudflats, 

pickleweed and gumplant marshes, upland marsh edges, brackish creek channels and 

other tidal marsh systems. Much of this area is highly developed with light industrial, 

commercial, and business facilities, and a portion of the Bay Trail runs through the northSan Francisco Estuary Invasive Spartina Project 46. 2008 Aquatic Pesticide Application Plan 
ern portion of the site. For the purposes of this plan, there were an estimated 100.3 acres 

of marshland within this site in 2005. 

The Spartina infestations within this site are distributed throughout the habitat types described above. In sum, the marshes of this site contain 60.0 acres of non-native Spartina

targeted for control, representing 60% of the surrounding marsh. This infestation has rapidly expanded onto the open mudflats on the western portion of this site, as well as constricting the channels on the northern and southern portions. Non-native Spartina has 

dominated most of the available marshland habitat, with only scattered populations of 

native tidal marsh plant species remaining in the area. Because of the unusually large and 

high density population of clapper rail in this site complex, treatment has been phased 

over several years, with only the upper channels receiving applications in 2006. The entire site was treated in 2007, with approximately 60% just “chemically mowed” with a 

low, sub-lethal concentration of imazapyr to stop seed production while maintaining the 

above-ground biomass for rail refugia. In 2008, all remaining hybrid Spartina will be 

treated with the full concentration of imazapyr, which will be applied by conventional 

spray truck, backpack sprayer, amphibious tracked vehicle, and helicopter. Partners on 

this site include the San Mateo County Mosquito Abatement District, San Mateo Flood 

Control District, City of South San Francisco, and the San Mateo County Transit District 

(Sam Trans). Note that this is a complex site composed of multiple sub-areas. Please refer 

to the Site Specific Plan for detailed descriptions of the sub-areas and the associated 

treatment methods. 

Site 19 – West San Francisco Bay, San Mateo County 

The area encompassed by this Site Specific Plan includes all marshlands of San Mateo 

County extending south from the San Francisco/San Mateo County line in the north to the 

San Mateo-Hayward Bridge in the South. A separate Site-Specific Plan for the Colma 

Creek/San Bruno Marsh Complex (TSN:ISP-2005-18) has been developed to specifically 

address the Spartina treatment approaches for that area, and is therefore not included in 

this plan. Many of the Sub-Areas for this site are small marshes or mudflat areas bordered 

by light or heavy industrial development, riprap shoreline, Highway 101, the San Francisco International Airport, or other intensive uses. Several are partially restored marshes. 

Few of these Sub-Areas support diverse, intact native marsh conditions, and non-native 

Spartina has come to dominate each one. 

The infestations of non-native Spartina that constitute the West San Francisco Bay Complex are scattered along the shoreline in many types of habitats. Spartina can be found 

along the rip-rap of shoreline development, in remnant or newly formed pickleweed 

marsh, along channels emptying into the bay, amongst sand/shell beaches, within large 

established marsh, in wide lagoons, on shallow mudflats, and in small coves and sheltered crannies all along the Bay edge. In all Sub-Areas, non-native Spartina was rapidly 

expanding into the existing available habitat. Out of an estimated 350 acres of marsh 

habitat covered by this Site-Specific Plan, there were 85 net acres (24%) of non-native 

Spartina requiring control in 2005. Three years of successful treatment by SMCMAD has 

reduced this site complex to less than 10 widely scattered acres to be treated in 2008. The 

primary treatment method at this site is aquatic herbicide, which will be applied by conventional spray truck, backpack sprayer, amphibious tracked vehicle, boat, and helicopter. Partners on this site include the San Mateo County Mosquito Abatement District, San 

Francisco International Airport, Oyster Point Marina, City of Brisbane, City of BurlinSan Francisco Estuary Invasive Spartina Project 47. 2008 Aquatic Pesticide Application Plan 
game, City of San Mateo, County of San Mateo, City of Foster City, California State 

Lands Commission, City of South San Francisco, U.S. Coast Guard Reservation, and a 

number of individual commercial property owners. Note that this is a complex site composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions 

of the sub-areas and the associated treatment methods. 

Site 20 – San Leandro / Hayward Shoreline Complex, Alameda County 

The area encompassed by this Site-Specific Plan includes the marshlands of the San 

Leandro and Hayward shoreline, Alameda County, extending south from the Metropolitan Golf Course and Oakland International Airport in the north to the San MateoHayward Bridge in the south. A separate Site-Specific Plan for Oro Loma Marsh 

(TSN:ISP-2004-07) has been developed to specifically address the Spartina treatment 

approaches for that area, and is therefore not included in this Plan. The marshland areas 

in this site complex range from large, complex restored marsh systems to channel-bank 

fringe marsh areas. They line the east shore of the Bay, providing a natural border between the highly urbanized and developed areas of the cities of San Leandro, San 

Lorenzo, and Hayward and the open waters of the Bay. Much of this area is regularly 

used for passive recreational activities along portions of the Bay trail, within EBRPD 

lands, and other trails throughout the area. 

The infestations of non-native Spartina that constitute the San Leandro and Hayward 

Shoreline Complex are located along the shoreline in many types of habitats. Invasive 

Spartina can be found along the rip-rap of shoreline fill and levees, in remnant or newly 

formed pickleweed marsh, along channels emptying into the bay, amongst sand/shell 

beaches, within large established marsh restoration sites, on shallow Bay-edge mudflats, 

and in small coves and sheltered marsh areas along the Bay edge. In all sub-areas, nonnative Spartina was rapidly expanding into the existing available habitat. Out of an estimated 580 acres of marsh habitat covered by the Site-Specific Plan, there were an estimated 204 net acres of non-native Spartina requiring control in 2005, representing 35.2% 

of the area. Treatment from 2005 -2007 has reduced this infestation by 70-80%, leaving 

approximately 45 acres to treat in 2008. Eight new sub-areas were added for the 2008-

2010 Site-Specific Plans comprised of small newly-discovered infestations within the 

geographic boundaries of the overall site. The primary treatment method at this site is 

aquatic herbicide, which will be applied by helicopter, conventional spray truck, backpack sprayer, and amphibious tracked vehicle. Partners on this site include the Alameda 

County Flood Control District, East Bay Regional Parks District, City of San Leandro, 

City of Oakland, and the Oro Loma Sanitary District. Note that this is a complex site 

composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the sub-areas and the associated treatment methods. 

Site 21 – Ideal Marsh, Alameda County 

Ideal Marsh is a 178.8-acre wetland restoration site located on the eastern shore of the 

San Francisco Bay Estuary that was allowed to naturally restore to unrestricted daily tidal 

exchange. The site is bordered to the north by the mouth of the Alameda Flood Control 

Channel (TSN:ISP-2004-1); the shoreline marshes of this site run for approximately 2.5 

miles south of the channel to a point about a mile north of the Dumbarton Bridge where a 

levee cuts back to the shoreline. Levees along the eastern edge of this site separate it from 

current salt evaporator ponds, with the Coyote Hills, and the Regional Park of the same 

name, located just over one mile to the east. 

San Francisco Estuary Invasive Spartina Project 48. 2008 Aquatic Pesticide Application Plan 
The two Sub-Areas of Ideal Marsh (North and South) were being rapidly colonized with 

an expanding infestation of Spartina alterniflora hybrids, with a total of 98 acres of invasive Spartina or 54% of the marshlands at Ideal Marsh in 2006. These plants occupied all 

habitat types present in these marshes, including open mudflats, sand/shell beaches, eroding marsh edge, pickleweed plain, levee edge and other areas. Helicopter treatment from 

2005 -2007 reduced the infestation by 95% or more. The area to be treated in 2008 contains patches and individual hybrid S. alterniflora plants scattered across the marsh plain 

and in a few of the channels. The primary treatment method at this site is aquatic herbicide, which will be applied by backpack or truck. The partner on this site is the U.S. Fish 

and Wildlife Service, Don Edwards National Wildlife Refuge. 

Site 22 – Two Points Complex, Alameda County 

The Two Points Complex is located on the east side of north San Francisco Bay and southeast San Pablo Bay in Contra Costa County, along the shoreline of the City of Richmond, 

and includes areas both north and south of the Point Richmond peninsula and the Richmond-San Rafael Bridge. The shoreline adjacent to these sites is heavily developed with 

land use including commercial, industrial, residential, and park or marina areas. The Bay 

Trail provides recreational access along the upland edge of the southern marshes in the 

complex, but only provides distant viewing of the north marshes because the trail is located 

further inland at this point. The marshes of this area are wide fringing marshes with mixed 

pickleweed/Spartina vegetation assemblages. These marshes contain large and small channels, mudflats, wide mid-marsh plains and other areas. 

The infestations at the Two Points Complex are still in the early stages of establishment, 

with approximately 5 acres scattered over the 598 acres of the five sub-areas, or less than 

1% of the total marsh area. The establishing clonal patches within this area are located 

mostly along the bay front amongst native Spartina stands or along the banks of small 

channels within the marshes, and are beginning to coalesce. The channels and marsh 

plain of San Pablo Marsh was being rapidly invaded until treatment began in 2005 on the 

western portion and 2007 for the eastern. The easternmost portion of San Pablo Marsh 

will be treated for the first time in 2008 because the plants senesced early in both 2006 & 

2007. The primary treatment method at this site is aquatic herbicide, applied by airboat, 

backpack sprayers, and conventional spray truck. Partners on this site include the State of 

California Lands Commission, Republic Services, Chevron/Texaco, Richmond Rod and 

Gun Club Inc., and East Bay Regional Parks District. Note that this is a complex site 

composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions of the sub-areas and the associated treatment methods. 

Site 23 – Marin Outliers, Marin County

The area encompassed by this Site Specific Plan includes selected marshlands of Marin 

County extending south from the Point San Pedro in the north to Sausalito in the South. 

Separate Site-Specific Plans for the Corte Madera Creek Complex (TSN:ISP-2005-04), 

Blackie’s Pasture (TSN: ISP-2004-03) and Pickleweed Park (TSN:ISP-2004-09) have 

been developed to specifically address the Spartina treatment approaches for each of 

those areas. Many of the Sub Areas are small marshes or mudflat areas bordered by light 

or heavy industrial development, rip-rap shoreline, or other uses. Several are partially restored marshes. In sum, these areas represent an important patchwork of small marsh areas within Marin County. 

San Francisco Estuary Invasive Spartina Project 49. 2008 Aquatic Pesticide Application Plan 
The infestations of non-native Spartina that constitute the Marin Outliers complex are 

scattered along the shoreline in many types of habitats. Spartina can be found along the 

rip-rap of shoreline development, in remnant or newly formed pickleweed marsh, along 

channels emptying into the bay, within large established marsh, on shallow mudflats, and 

in small coves and sheltered crannies along the Bay edge. In all Sub-Areas, non-native 

Spartina was in the initial stages of expansion into the existing habitat. Out of an estimated 130 acres of marsh habitat covered by this Site-Specific Plan, there were 2.6 net 

acres of non-native Spartina requiring control in 2005, representing 2% of the marsh 

area. Most of these sites are down to only several hundred square feet or less after effective treatments from 2005 -2007. The primary treatment method at a number of sites in 

this complex is manual removal after the reductions of the past several control seasons. 

Other sites will still depend on aquatic herbicide treatment, which will be applied by 

backpack sprayer & conventional spray truck. Partners on this site include Marin Audubon, County of Marin, CDFG, Loch Lomond Marina, Strawberry Recreation District, 

City of San Rafael, City of Mill Valley, City of Novato, California State Lands Commission, McNear Brick and Block, Paradise Cay Yacht Club, City of Sausalito, and a number 

of smaller residential and commercial landowners. Note that this is a complex site composed of multiple sub-areas. Please refer to the Site Specific Plan for detailed descriptions 

of the sub-areas and the associated treatment methods. 

Site 24 – Petaluma River, Sonoma County 

This area includes approximately 4,500 acres of marshland and riparian habitat within the 

Petaluma River Watershed stretching from the City of Petaluma, at the confluence of the 

Petaluma River and Lynch Creek in the north to San Pablo Bay in the south. This site 

consists of a complex mosaic of historic tidal marsh habitat, developed shoreline, brackish tidal riparian edge zones, maintained pastureland, restoration sites, light industrial facilities and urban development. 

The pioneering infestation of Spartina alterniflora hybrids in the Petaluma River complex was discovered in November 2006, and is still very limited in its distribution. The 

majority of the infestation is located along the banks of the river adjacent to a dredging 

and barge dock facility just downstream of the Highway 101 crossing south of Petaluma, 

with scattered infestations located upstream and downstream this central core. In sum, 

these infestations cover approximately 0.2 acres scattered over this very large marshland 

complex, which is equal to less than 0.01% of the area. The first treatment at this site occurred in 2007 and reduced this pioneering infestation significantly. The primary treatment method at this site is aquatic herbicide, which will be applied by boat, backpack 

and/or conventional spray truck. The primary ISP partner on this site is the Friends of 

Petaluma River, a group that has existing relationships with the community of the watershed and the landowners along the river. 

Site 26 – North San Pablo Bay, Solano County 

There are two main portions of this sub area: the restoration site on the east side of the 

Napa River called White Slough, in Vallejo, and the marshes along the shorelines of the 

Northeastern San Pablo Bay. 

White Slough marsh is a roughly 135-acre restored tidal marsh that lies to the east of 

Highway 37 and west of Sonoma Boulevard in the City of Vallejo. The marsh is a 

sparsely vegetated tidal marsh in the initial stages of colonization. The majority of the 

San Francisco Estuary Invasive Spartina Project 50. 2008 Aquatic Pesticide Application Plan 
area is open mudflat with tidally inundated low sections. The periphery of the marsh is 

composed of scattered pickleweed (Sarcocornia pacifica), non-native Spartina, and alkali 

bulrush (Bolboschoenus maritimus). 

The other marsh areas included in this sub-area is the massive mudflat and shoreline area 

of San Pablo Bay NWR west of Mare Island. This large area of restored and historic tidal 

marsh, developed shoreline, industrial and military facilities is only lightly infested with 

non-native Spartina, including both S. densiflora and hybrid S. alterniflora. 

The infestation at White Slough east of Hwy. 37 is in the very early stages of colonization, and is located along the western, northern and eastern edges of the marsh in scattered small patches. The clonal individuals have not coalesced to any real extent, and 

there is very little marsh vegetation in some portions of this marsh. Aquatic herbicide will 

be applied by backpack sprayer. 

9. WATER QUALITY MONITORING PLAN 

Objective 

Conduct water quality monitoring sufficient to achieve compliance with NPDES Statewide General Permit requirements. 

Monitoring Site Selection 

Approximately 150 sites (sub-areas) of invasive Spartina throughout the San Francisco 

Bay region are slated for treatment with aquatic herbicide during the 2008 control season. 

According to current NPDES permit requirements, ten percent (10%), or 15 of the 150 

sites, must be monitored for water quality. These sites are to be selected at representative 

locations, and are to include all of the herbicides being applied. To assist with sampling 

site selection, the ISP identified four different treatment site types, as follows: 

I. Tidal Marsh, Microtidal Marsh, Former Diked Bayland, Backbarrier Marsh 

II. Fringing Tidal Marsh, Mudflats, and Estuarine Beaches 

III. Major Tidal Slough, Creek or Flood Control Channel 

IV. Urbanized Rock, Rip-Rap, Docks, Ramps, etc. 

The ISP has selected representative sites of each of these marsh site types to be sampled 

for water quality. Since Type IV infestation sites are usually very small, sparse, and adjacent to large bodies of water with constant flushing that will serve to quickly dilute any 

herbicide incidentally entering the water column; fewer sites within this type will be 

monitored for 2008. Site Types I and II are considered to be the sites most likely to develop detectible levels of herbicide in the water column, although the results of ISP’s 2006 

WQMP revealed that the highest one-week post-treatment samples actually came from two 

Type III sites. For 2008, the final sampling plan list includes six Type I sites, five Type II 

sites, three Type III sites, and one Type IV site chosen to represent the range of herbicide 

delivery systems and marsh dynamics present in our work program. Imazapyr is the primary herbicide with glyphosate applied to just one of the 150 sub-areas; consequently 

just one glyphosate site will be monitored for water quality as a representative. Table 5 

provides a summary of the sites. 

San Francisco Estuary Invasive Spartina Project 51. 2008 Aquatic Pesticide Application Plan 
Table 5. Summary of Water Quality Monitoring Sites for the 2008 Season 

Sites Site 

Number Marsh Type Treatment 

Date Application 

Upper Corte Madera 

Creek 4h III 7/8/08 Imazapyr – Backpack, 

Truck 

Loch Lomond Marina 23c IV 7/17/08 Imazapyr – Backpack 

Imazapyr – Backpack, 

Truck Beach Drive 23b 7/17/08 II 

7/18/08 Imazapyr – Backpack; 

Manual for seedlings Blackie’s Pasture 3b III 

22b I 7/21/08 Imazapyr – Backpack, 

Airboat, Truck San Pablo Marsh 

Creekside Park 4g I 7/31/08 Imazapyr – Backpack 

Alameda Flood Control Channel Mouth 1a III 7/31/08 Imazapyr – Helicopter 

Cargill Mitigation 

Marsh 13c I 7/31/08 Imazapyr – Helicopter 

Inner Harbor 18d II 8/18/08 Imazapyr – Helicopter 

Sam Trans Peninsula 18e II 8/18/08 Imazapyr – Helicopter 

Elsie Roemer Bird 

Sanctuary 17a II 8/18/08 Imazapyr – MarshMog, 

Backpack 

Fan Marsh 17j I 8/21/08 Imazapyr – Truck 

Stevens Creek Tidal 

Marsh 15c I 9/2/08 Imazapyr – Truck 

Southampton Marsh 11 I 9/3/08 Glyphosate – Backpack 

Giant Marsh 10c II 9/4/08 Imazapyr - Backpack 

Monitoring Site Descriptions 

Following are brief descriptions for each of the monitoring sites. Additional site information was included previously in Section 8 of this plan. 

Alameda Flood Control Channel. The Alameda County Flood Control Channel 

(ACFCC) is a large, unlined trapezoidal channel that runs from east to west through 

Hayward, Alameda County, draining a nearly 880 square mile watershed into the San 

Francisco Bay. The levees on both sides of the ACFCC are topped with multi-use public 

park trails that are part of the San Francisco Bay Trail and Coyote Hills Regional Park. 

The flood control channel will be sampled right upstream of its mouth to the San Francisco Bay, a Type I site. Efficacy from 2006 & 2007 imazapyr applications was high, and 

the site will be retreated where necessary in 2008. 

Cargill Mitigation Marsh. This sub-area, a Type I site, is a 49-acre former solar salt production evaporator pond that was restored by opening the site to muted tidal action in 

1995, and full tidal action in 1998. It is bounded on the north by the levees of the Old 

Alameda Creek Channel, on the west by the Southern Whale’s Tail Marsh Site, and to the 

east and south by inactive salt ponds. The entirety of the site is surrounded by levees, 

San Francisco Estuary Invasive Spartina Project 52. 2008 Aquatic Pesticide Application Plan 
with two breach points on the western levee that drain the site into the Whale’s Tail 

South Fluke. Efficacy from 2006 & 2007 imazapyr applications was high, and the site 

will be retreated where necessary in 2008. 

Corte Madera Creek Complex. Two sites in the Corte Madera Creek Complex will be 

monitored, the banks of Upper Corte Madera Creek and Creekside Park. 

Upper Corte Madera Creek. This Type III site represents the upper reach from 

the College of Marin downstream to the Bon Air Road bridge, and includes the 

short section of an unnamed tributary that drains marshes near Lot 13 (College of 

Marin parking). Much of this stretch has narrow strips of marsh vegetation below 

the rip-rap, mostly pickleweed and S. foliosa, and a mudflat component. Much of 

the upper reach has an open space character, with Creekside Park and the College 

of Marin Ecology Study Area along the north bank, a small marsh to the south 

downstream of the confluence with the Lot 13 drainage, and the backyards of the 

houses on the south bank set back from the creek on the other side of the Marin 

County Flood Control District’s gravel maintenance road above the rip-rap. Efficacy from 2006 & 2007 imazapyr applications controlled the infestation but has 

not succeeded in full mortality on many of the plants. Any green, healthy S. densiflora will be retreated with imazapyr in 2008, while plants not healthy enough to 

translocate the herbicide will be removed manually.

Creekside Park. This Type I site is estimated to contain 20.6 acres of marshland 

habitat adjacent to the upper portion of Corte Madera Creek just upstream of Bon 

Air Road. The park was restored to marshland habitat in 1976, when a new channel system was excavated, upland areas were graded to intertidal elevations, and 

central islands were constructed from the channel dredge spoils as upland refugia. 

As part of this initial restoration effort, both Spartina densiflora and Spartina anglica were planted, as native marsh plants failed to establish within the first year 

of restoration. These plants were imported from Humboldt Bay and England respectively. Efficacy from 2006 & 2007 imazapyr applications controlled the infestation but has not succeeded in full mortality on many of the plants. Any green, 

healthy S. densiflora will be retreated with imazapyr in 2008, while plants not 

healthy enough to translocate the herbicide will be removed manually.

Colma Creek Complex. Two sites in the Colma Creek Complex will be monitored, the 

shoreline of Sam Trans Peninsula and the entirety of Inner Harbor. 

Sam Trans Peninsula. The Sam Trans Peninsula is a reclaimed peninsula constructed of fill to the north of the San Francisco International Airport. This site 

contains the fringing marsh areas on the east side of the peninsula proper, from 

the North Access Road north, to just west of the tip of the peninsula. Within this 

area there is an estimated 14.1 acres of marshland habitat with an estimated 8 

acres of non-native Spartina prior to treatment. The Spartina is growing on previously open mudflats in mostly uniform monocultural stands, and advancing eastward into the Bay. This Type II site was treated for the first time in 2007, with 

some areas receiving a sub-lethal dose as a chemical mow. In 2008 the entire subarea will be treated with the full concentration of imazapyr used by ISP partners. 

Inner Harbor. The invasive Spartina has caused this marsh to establish through 

the accretion of sediment on the open mudflats west of the Sam Trans Peninsula. 

San Francisco Estuary Invasive Spartina Project 53. 2008 Aquatic Pesticide Application Plan 
San Bruno Creek feeds this area of the complex from its mouth in the southwest 

corner of Inner Harbor. This sub-area encompasses some 14.6 total acres of 

marshland, mudflat, and channel. The Spartina here consists of a coalesced 

meadow in the south and expanding individual pioneer clones scattered through 

the northern area. In sum, the infestation at this site is estimated at 8.5 acres. This 

Type II site was treated for the first time in 2007, with some areas receiving a 

sub-lethal dose as a chemical mow. In 2008 the entire sub-area will be treated 

with the full concentration of imazapyr used by ISP partners. 

Alameda-San Leandro Bay. Two sites in the Alameda-San Leandro Bay complex will be 

monitored, Elsie Roemer Bird Sanctuary and Fan Marsh. 

Elsie Roemer Bird Sanctuary. This Type II site includes an area along a stretch 

of southern Alameda Island, which runs from the jetty off Shoreline Dr. in the 

west to the Bayfarm Island Bridge in the east. Within the estimated 17.3 acres of 

marsh at this site, there were approximately 7 acres of non-native Spartina alterniflora hybrids, including several large clones coalescing on the open mudflats 

south of the main infestation. Efficacy from the 2007 imazapyr application was 

much more significant than in 2005 or 2006, and the site will be retreated where 

necessary in 2008. 

Fan Marsh. Fan Marsh is a roughly 11-acre marsh located along on the interior 

of Doolittle Drive at Earhart Road in Alameda. The property is owned by the Port 

of Oakland and consists of high marsh pickleweed/Spartina interspersed with 

several small channels draining to the Bay to the east of Doolittle Pond. The 

Spartina infestation within Fan Marsh is fairly uniform over the entirety of the 

marsh area. Prior to treatment, roughly 5 acres of Spartina were spread over 11 

acres of channels and high marsh plain at this site. This Type I site was treated for 

the first time in 2007, with very high efficacy at the mid-marsh elevation but poor 

results in the channels at low elevation. The site will be retreated where necessary 

in 2008. 

Marin Outliers. Two sites in the Marin Outliers complex will be monitored, Loch Lomond Marina and Beach Drive. 

Loch Lomond Marina. The Loch Lomond Marina is a Type IV site located off 

Point San Pedro Road in San Rafael, with Beach Drive immediately to the east. 

This site consists of a narrow fringe of marsh vegetation along the shoreline of a 

cove to the west of the marina, and the rip-rap along the inside of the protective 

marina levee on the western, southern and eastern edges. The site is lightly infested in scattered patches around the inner marina levees, with a few areas persisting in the small cove to the west. The site will be retreated where necessary in 

2008. 

Beach Drive. This sub-area actually consists of two very different marsh systems 

on either side of Beach Drive, which is a small residential street to the south of 

Point San Pedro Road in eastern San Rafael. To the west is a narrow, 100 m-wide 

cove which extends about 450 m to the northwest behind a row of residential 

properties on Beach Drive and Point San Pedro Road. This cove, a Type II site, 

has a significant and expanding presence of native Spartina foliosa with the associated increase in the accretion of sediment in recent years. Across the road to the 

San Francisco Estuary Invasive Spartina Project 54. 2008 Aquatic Pesticide Application Plan 
east is a 3-acre muted tidal marsh composed of pickleweed (Sarcocornia 

pacifica), gumplant (Grindelia stricta) and native Spartina in some of the small 

channels. Efficacy has been excellent in the muted marsh, but much more challenging in the mudflats of the cove even after several applications. The site will 

be retreated where necessary in 2008. 

Blackie’s Pasture. Blackie’s Pasture is a small City of Tiburon park co-managed by the 

City of Tiburon and Tiburon Audubon. The park is located along the shoreline of 

Richardson Bay, adjacent to Tiburon Boulevard. The park is heavily used by the public 

for passive recreation, and is comprised of a 0.7-acre pasture, a small creek channel 

(“Blackie’s Creek”) along the eastern edge of the pasture, and a shoreline area that includes the channel mouth, open mudflat (fed by sediment delivered by the creek), landscaped pathways and picnic areas, and rip-rap fill to the east along the Tiburon Peninsula. 

The Blackie’s Creek channel, a Type III site, was heavily infested with hybrid S. alterniflora, as was the small marsh component at the mouth. The mouth area downstream 

of the footbridge was also heavily infested with S. densiflora. After several years of manual and chemical control work, the infestation in the creek contains just minimal patches, 

and the marsh at the mouth has few mature plants remaining. Much of the treatment in 

2008 will involve manual removal of seedlings of S. densiflora, and retreatment of hybrid 

S. alterniflora from backpack sprayers. 

San Pablo Marsh. This Type I site is a 165-acre marsh at the mouth of San Pablo Creek 

on the City of Richmond shoreline in southeastern San Pablo Bay. San Pablo Marsh is 

predominantly pickleweed with S. foliosa on the bayfront and in the channels. The marsh 

stretches east to an 11-acre pickleweed, S. foliosa and alkali bulrush (Bolboschoenus 

maritimus) cove bordered by levees on either side, located behind the Richmond Rod and 

Gun Club rifle range. The western portion of this site has been treated since 2005, but the 

larger infestation in the eastern marsh and out onto the mudflats has evaded treatment due 

to early senescence. These expanding mudflat clones, as well as the infestation encroaching up the channels, will be treated by airboat and backpack in 2008, along with any necessary retreatment in the western areas. 

Southampton Marsh. Southampton Marsh is the largest extant marsh within the Carquinez Strait. Its roughly 175 acres are located within the 720-acre Benicia State Recreation Area, Solano County. The marsh lies in the central portion of the park, and consists 

mostly of high marsh pickleweed/gumplant habitat, with a deep main channel and several 

smaller channels throughout. Cordylanthus mollis ssp. mollis (soft bird’s-beak), an endangered plant species, can be found in some of the high marsh areas of the site. Access 

to the marsh is restricted to park personnel and researchers to protect the C. m. mollis

populations from potential damage caused by trampling. Southampton Marsh contains 

the only known population of Spartina patens in the San Francisco Estuary. Several large 

clones were scattered throughout the southern and western portions of the marsh, and 

multiple smaller clones are peppered throughout the area. A number of S. patens clones 

are adjacent to the main channel draining the marsh. This is a Type I site and will be the 

only site treated with glyphosate in 2008. 

Stevens Creek Tidal Marsh. The City of Mountain View’s Shoreline Regional Wildlife 

and Recreation Area includes several tidal sloughs, Bay-front tidal marsh habitat and restored tidal marsh areas. Two of the main marshes within this area are the Charleston 

Slough marsh and the Stevens Creek Marsh, both of which have infestations of nonSan Francisco Estuary Invasive Spartina Project 55. 2008 Aquatic Pesticide Application Plan 
native Spartina. Stevens Creek Marsh, a smaller marsh at roughly 30 acres, is also a restored formerly diked salt pond, but Stevens Creek is highly vegetated. The marsh is located on the eastern end of the Recreation Area, at the Bayward end of the Stevens Creek 

Trail. The marsh has well-established populations of native tidal marsh plant species including broad meadows of native Spartina foliosa. Within this native matrix however, a 

sizeable population of non-native Spartina hybrids has been expanding over the last 3-5 

years. This Type I site was treated for the first time in 2007, and retreatment will be necessary on a portion of the marsh in 2008. 

Giant Marsh. Giant Marsh is a 30-acre pickleweed marsh in the far southwestern corner 

of Point Pinole Regional Shoreline on San Pablo Bay. This is a newly added sub-area that 

has not yet been treated. The infestation at Giant Marsh is composed of scattered clones 

of hybrid Spartina alterniflora along the bayfront edge of the marsh and out onto the 

mudflats. This infestation is in the very early stages of establishment, with less than 500 

ft2

 of hybrid Spartina that has been identified. The invasive cordgrass has not yet colonized the interior of the marsh or established along the channels. This Type II site will be 

treated with imazapyr by backpack sprayer in 2008. 

Sampling Frequency and Sampling Design 

The sampling events are designed to characterize the potential risk involved with imazapyr and glyphosate applications relative to adjacent surface waters. Consistent with 

permit requirements, the monitoring program will include background/pre-treatment 

sampling up to 24 hours prior to the application, application event monitoring immediately post-treatment, and one-week post-application event monitoring. During background sample collection, the point will be recorded using GPS and marked with a 

flagged PVC pipe to aid ISP staff in locating the point for future sampling events. The 

application event samples will be collected immediately adjacent to the treatment area 

after sufficient time has elapsed such that treated water will have entered the adjacent 

area. Since it is standard protocol for the ISP partners to treat Spartina on a low or receding tide when possible, application event samples will often be taken 2-5 hours posttreatment when the tide has again flooded the site. Finally, the one-week post-treatment 

monitoring will be conducted when sufficient water is present at the site on the seventh 

day after the application. The CDFG Water Pollution Control Laboratory recommends 

the submission of one duplicate for every 20 samples collected, so the ISP will be submitting three duplicates for the 45 total base samples taken to enhance quality assurance. 

These will be added to either the treatment event or one-week post-treatment event since 

the herbicide levels in the pre-treatment samples are usually 0. It is standard for the lab to 

include blanks itself as part of their quality control, so the ISP will only occasionally send 

additional blanks. 

Sampling Procedures 

The Spartina Project will be conducting its own water quality monitoring program for 

2008 following the procedures developed for the State Water Resources Control Board 

Aquatic Pesticide Monitoring Program (APMP) by the San Francisco Estuary Institute 

(SFEI). These procedures are outlined in the APMP Quality Assurance Program Plan 

(2004), available at www.sfei.org. Water samples will be collected using a sampling rod 

and pre-cleaned amber glass 1-liter bottles. Temperature, electrical conductivity, salinity, 

and dissolved oxygen will be measured in the field with a portable YSI Model 85 (Yellow 

Springs Instruments Inc., Ohio, USA), while pH will be measured with an Oakton waterSan Francisco Estuary Invasive Spartina Project 56. 2008 Aquatic Pesticide Application Plan 
proof pHTestr1 (Oakton Instruments, Illinois, USA). Turbidity will be measured by the lab 

from the water samples submitted by ISP, as allowed for in the NPDES Statewide General 

Permit. 

Sample Analysis 

Following collection, water samples will be stored on ice packs and shipped for priority 

overnight delivery to the California Department of Fish and Game’s Water Pollution 

Control Laboratory in Rancho Cordova, CA. The samples will be analyzed within the 

appropriate holding times for imazapyr or glyphosate concentrations. The analytical lab 

will adhere to all QA requirements outlined in the APMP QA plan. 

Data Analysis 

The results of the conventional water quality parameters (turbidity, water temperature, 

dissolved oxygen, pH, conductivity, and salinity) will be tested for normality and then 

analyzed with paired t-tests to determine if the values of the parameters change significantly over the three sampling events at each site. This test is used for matched pairs 

when two responses form a pair of measurements coming from the same experimental 

subject, such as measurement of dissolved oxygen before and after herbicide treatment in 

the adjacent marsh. The t-test will be run three times on each parameter, first comparing 

the pre-treatment value to the treatment value, then the pre-treatment to the posttreatment, and finally the treatment to post-treatment. Results will be submitted to the 

San Francisco Bay Regional Water Quality Control Board and placed on the ISP’s website for public viewing. 

10. APPLICABLE WATER QUALITY BMPS 

The following mitigations were identified in the Spartina Control Program’s Programmatic Environmental Impact Report/Statement (PEIR/S). These mitigations will be implemented at all herbicide treatment sites and verified by the Field Operations Staff. 

IMPACT WQ-1: Degradation of Water Quality Due to Herbicide Application 

MITIGATION WQ-1: Herbicides shall be applied directly to plants and at low or receding tide to minimize the potential application of herbicide directly on the water surface, 

as well as to ensure proper dry times before tidal inundation. Herbicides shall be applied 

by a certified applicator and in accordance with application guidelines and the manufacturer label. 

The Control Program shall obtain coverage under the State NPDES Permit for the Use of 

Aquatic Herbicides and any necessary local permits. A monitoring program shall be implemented as part of the NPDES permit, and shall include appropriate toxicological studies to determine toxicity levels of the herbicide solutions being used. The Control Program shall use adaptive management strategies to refine herbicide application methods to 

increase control effectiveness and reduce impacts. 

IMPACT WQ-2: Herbicide Spills 

MITIGATION WQ-2: Herbicides shall be applied by or under the direct supervision of 

trained, certified or licensed applicators. Storage of herbicides and adjuvants/surfactants 

on-site shall be allowed only in accordance with an approved spill prevention and containment plan; on-site mixing and filling operations shall be confined to areas appropriSan Francisco Estuary Invasive Spartina Project 57. 2008 Aquatic Pesticide Application Plan 
ately bermed or otherwise protected to minimize spread or dispersion of spilled herbicide 

or surfactants into surface waters. 

When containers of herbicide larger than the standard 2.5 gallon are used (such as the 15 

gallon containers that are used by the helicopter contractors for aerial application), these 

containers must remain in the staging area(s) on a levee or other appropriate upland site. 

These larger containers will not be allowed into the marsh, and a spill response plan must 

be in place in the event of an accidental discharge, to ensure that herbicide does not reach 

the marsh or surface waters. 

IMPACT WQ-3: Fuel or Petroleum Spills 

MITIGATION WQ-3: Fueling operations or storage of petroleum products shall be 

maintained off-site, and a spill prevention and management plan shall be developed and 

implemented to contain and clean up spills. Transport vessels and vehicles, and other 

equipment (e.g., mowers, pumps, etc.) shall not be serviced or fueled in the field except 

under emergency conditions; hand-held gas-powered equipment shall be fueled in the 

field using precautions to minimize or avoid fuel spills within the marsh. Other, specific 

best management practices shall be specified as appropriate in project-specific Waste 

Discharge Requirements. 

In addition to these water quality mitigation measures, each partner agency and its contractors are required to have an acceptable Site Safety and Materials Handling Plan (Appendix 3). 

Applicator Calibration Training 

During the first year of operation, ISP recognized that, even when partners exercised 

great care during herbicide application, there was still considerable variability in application rates. Because the rate of herbicide application is critical for protecting water quality 

and staying within the project budget, the ISP began providing annual “Applicator Calibration Training” for contractors and agency personnel in 2006. The training, which is 

authorized by California Department of Pesticide Regulation Continuing Education, provides partners with a hands-on opportunity to practice and fine tune application techniques. At each training, ISP staff discusses the importance of correct application, and a 

representative of the herbicide manufacturer, BASF, presents the manufacturer’s recommendations of how to apply imazapyr (Habitat®) properly. The presentations are followed by field exercises where partners compete to be the most accurate applicator. 

A major motivation for these annual trainings came from a study in Cornish and Burgin 

(2005) showing that applicators applying herbicide to a given plot size could vary by as 

much as ten times in the amount of product used and the time it took to spray the plot. In 

their first experiment, applicators treated a 20 X 0.5m strip (10m2

). Application times 

ranged from 24.3 to 112.7 seconds, equivalent to 2.7 – 12.6 hours for them to complete 

one acre. They used the equivalent of 34.2 – 160 gallons/acre of tank mix, or 0.34 – 1.6 

gallons of product per acre. For our expensive imazapyr herbicide (about $275 per gallon) the range would be $92 – $432 per acre, and more than twice the maximum label 

rate of 0.75 gallons per acre. 

Their second experiment showed even more alarming results. Using a smaller 1m2

 test 

area for the applications, treatment times ranged from 4.5 – 45 seconds, the equivalent of 

spending 5 – 50.6 hours on each acre. They used the equivalent of 21.4 – 684 galSan Francisco Estuary Invasive Spartina Project 58. 2008 Aquatic Pesticide Application Plan 
lons/acre of tank mix, or 0.21 – 6.84 gallons of product per acre. If this were imazapyr, 

the cost range would be $57 - $1847 per acre for the herbicide alone (up to nine times the 

max label rate), and labor costs would be extremely high for those on the upper end of the 

time spectrum. 

In addition to off-label applications, lack of FIFRA compliance, and higher costs, there 

are other problems with this variation between applicators. As the BASF representative 

noted, over-applications can actually reduce efficacy by washing the product off the 

plants, which emphasizes the importance of getting the application rates right. This may 

be especially true when using surfactants made from oils. 

The hands-on portion of the ISP field training is an attempt to directly address some of 

these obvious problems, achieve some consistency across the many applicators working 

around the Estuary on this project, and reduce the amount of herbicide entering the environment while still eliminating the Spartina threat efficiently. We established 340ft2

 plots 

in the marsh (equivalent to 1/128 of an acre) and had the attendees spray the plots (with 

just water, no herbicide) utilizing a variety of equipment including backpack sprayers, 

conventional spray truck, and amphibious vehicle. Applicators were timed and then were 

asked to spray into a bucket for the same length of time at the same pressure as the application. The amount of water in the bucket was measured and recorded for each participant. Because the area of the plots was 1/128 of an acre, and there are 128 ounces in a 

gallon, the number of ounces sprayed into each bucket was equivalent to the number of 

gallons per acre they would have applied. The beauty of this exercise is that once the 

plots are set up, it requires no math to achieve your calibration, just a timer and a bucket. 

BASF distributes these simple calibration kits for free to ISP partners. The training attendees were able to get direct feedback on their application rates and to see how easy and 

beneficial calibration can be, and left the training with a simple kit and protocol to do so. 

And managers in attendance were able to see how the correct rates will affect the bottom 

line and help to manage the budget for Spartina control. 

San Francisco Estuary Invasive Spartina Project 59. 2008 Aquatic Pesticide Application Plan 
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Personal Communications 

John Smith, BASF, Salem, OR 

Mark Taylor, East Bay Regional Park District, Hayward, CA 

Katy Zaremba, Invasive Spartina Project, Stinson Beach, CA 

San Francisco Estuary Invasive Spartina Project 63. 2008 Aquatic Pesticide Application Plan