(REVISION 1) 

Prepared in support of Coverage Under: 

Statewide General National Pollutant Discharge Elimination System (NPDES) Permit for Residual 

Aquatic Pesticide Discharges to Waters of the United States from Algae and Aquatic Weed Control 

Applications; Water Quality Order No. 2013-0002-DWQ; General Permit No. CAG990005 

(As amended by Orders 2014-0078-DWQ, 2015-0029-DWQ, and 2016-0073-EXEC) Submitted to: 

State Water Resources Control Board 

April 2021 

(Revised) 

Prepared on Behalf of: 

Citizens Development Corporation 

1105 La Bonita Drive 

San Marcos, California 92078 

CONTENTS 

1.0 INTRODUCTION................................................................................................................................... 1 

1.1 Lake Setting......................................................................................................................................... 1 

1.2 Overview of the Regulatory History.................................................................................................. 3 

2.0 Aquatic Plant Nuisance Conditions.................................................................................................. 4 

3.0 Treatment Areas at Lake San Marcos.............................................................................................. 5 

4.0 Algaecides and Aquatic Herbicides to  be used at Lake San Marcos........................................... 6 

5.0 Discussion of Factors Considered  when Selecting Management Options................................. 6 

6.0 Description of Lake Control  Structures and Their Operation....................................................... 8 

7.0 Section 5.3 Exception......................................................................................................................... 8 

8.0 Monitoring Program........................................................................................................................... 8 

8.1 Lake Assessment.................................................................................................................................. 9 

8.2 Data Collection...................................................................................................................................... 9 

8.3 Monitoring Approach........................................................................................................................... 9 

8.4 Monitoring – Visual............................................................................................................................ 11 

8.5 Monitoring – Physical Parameters................................................................................................... 11 

8.6 Monitoring Water Chemistry– Grab  Sample Collection, Handling, and Analysis..................... 11 

8.7 Grab Sample Collection and Physical  Monitoring Locations....................................................... 12 

8.8 Quality Assurance.............................................................................................................................. 12 

9.0 Record Keeping and Reporting........................................................................................................ 14 

9.1 Record Keeping Requirements......................................................................................................... 14 

9.2 Annual Reporting............................................................................................................................... 14 

9.3 Non-Compliance Reporting.............................................................................................................. 15 

10.0 Best Management Practices........................................................................................................... 15 

10.1 Spill Prevention and Containment................................................................................................. 15 

10.2 Application Rate Controls............................................................................................................... 15 

10.3 Education of Applicator Information............................................................................................. 15 

10.4 Planning and Coordination with  Stakeholders............................................................................ 16 

10.5 Measures to Prevent Fish Kills........................................................................................................ 16 

11.0 Examination of Alternative Approaches to Nuisance Condition Management........................ 16 

12.0 REFERENCES...................................................................................................................................... 18 

This Aquatic Pesticide Application Plan (APAP) has been prepared in compliance with the Statewide General National Pollutant Discharge Elimination System (NPDES) Permit for Residual Aquatic Pesticide Discharges to Waters of the United States from Algae and Aquatic Weed Control Applications (Permit) (State Water Resources Control Board [SWRCB] 2013). Amongst the provisions of the Permit is the submission of an APAP, and this document is a comprehensive plan that identifies the setting, approach, monitoring, and reporting for use of aquatic pesticides at Lake San Marcos (Lake), San Diego County, California. 

An immediate action in the planning stages is the application of algaecide in conjunction with alum. This proposed effort has been undertaken pursuant to remediation of the lake for nutrient impairments (see below), and is currently part of several pilot studies being undertaken at the Lake and in the Upper San Marcos Creek watershed. These pilot studies will be the basis of future corrective actions, which are being undertaken in close coordination with the Regional Board. 

From a more general perspective, the use of aquatic pesticides, herbicides, and dyes are considered herein as tools within a larger set of lake management practices. The Lake owner, Citizens Development Corporation (CDC), has undertaken to manage the Lake environment in order to promote and maintain the beneficial uses of the Lake. This Plan includes descriptions of the Lake environment, a description of nuisance conditions present at the Lake, important management of Lake resources, the decision process for how the uses of algaecides, herbicides and dyes will be selected and used, and the monitoring and reporting of the use of approved algaecides, herbicides, and dyes. 

An inherent part of the activities covered by this Plan will be establishing a balance between impairing natural resources and managing the Lake environment with products designed to treat vegetative nuisance conditions. CDC recognizes that the nuisance conditions are seasonal in nature and that the appropriate use of algaecides, herbicides and dyes will require ongoing assessment of parameters such as water temperature, clarity, seasonal progression (and senescence) of vegetation and/or phytoplankton. This Plan seeks to describe how CDC will establish a balanced approach and be a responsible steward of state water resources. 

Lake San Marcos lies within a developed unincorporated area of northern San Diego County. The Lake is a finger lake running north to south with several embayments on either side of the upper part of the Lake (FIGURE 1). The Lake is a recreational resource valued by boaters, the sport fishing community, and area residents. The Lake is used as a source of irrigation water for an adjacent golf course; withdrawal is balanced by replenishment with groundwater. 

The upper approximately two-thirds of the lake is developed, and the margins of the lake consist of landscaped grounds or armored shorelines. Many residences along the margin of the lake include boat docks (typically with pontoon or duffy boats), and the hotel complex on the eastern shoreline includes a boat marina. In contrast to the upper Lake, the lower two-thirds of the Lake lies in a steep canyon and is bounded by chaparral-vegetated slopes. 

The dam is located at the southern end of the Lake. When full, the Lake is 56 acres in area and holds approximately 509 acre-feet of water (DBSA 2016). The historical average sedimentation rate estimated based on available bathymetric surveys (e.g., Ball, 1974; Tierra Data 2013) is around 2 cm/year. 

The Lake is located at the southern boundary of the Richland Hydrologic Subarea within the San Marcos Hydrologic Area of the Carlsbad Hydrologic Unit in northern San Diego County, and is an impoundment of San Marcos Creek (Creek). The Creek drains a watershed of approximately 18,540 acres (DBSA 2016). The watershed area drains into the Lake at uneven rates throughout the year: during the summer the Creek can run dry for several months, while in the winter there is a base flow which increases significantly during storm events. As a result of this pattern, nutrient loading from the watershed is largely a result of winter stormwater flows (DBSA 2016).  

The Lake is subject to the Water Quality Control Plan for the San Diego Basin (Basin Plan) narrative objectives, which directs prevention of “plant nuisances” (Regional Water Quality Control Board [RB] 1994). The RB has issued two documents to encourage progress on finding a remedy. The first was the Investigative Order R9-2011-0033 (Investigative Order), which directed CDC to monitor the lake, evaluate the resulting data, and develop recommendations to address eutrophic conditions. These goals have been accomplished and documented in the Remedial Investigation/Feasibility Study Report, Upper San Marcos Creek Watershed and Lake San Marcos (RIFS) (DBSA 2016). 

In 2017, the RB adopted Resolution R9-2017-0038, “A Resolution Supporting a Path Forward for Nutrient Load Reductions in Lake San Marcos and the San Marcos Creek Watershed.” CDC continues to work with the upstream municipal parties (Cities of Escondido and San Marcos, County of San Diego, and Vallecitos Water District) on that path. 

The Lake is regulated by two state agencies. The SWRCB regulates water rights issues related to diversion of San Marcos Creek waters by the dam. The Regional Water Quality Control Board (RB) oversees issues related to water quality throughout the watershed, including the Lake. Water rights have been granted to CDC by the state and are the subject of an ongoing process to update CDC’s license. 

Several beneficial uses have been designated for Lake San Marcos including: Agricultural Supply (AGR) (i.e., irrigation), Human Health (Contact Water Recreation [REC-1]), Non-Contact Water Recreation (REC-2), Aquatic Dependent Wildlife (Support Warm Water Ecosystems (WARM), and Wildlife Habitat (WILD). The Richland hydrologic subarea (904.52), in which the Lake lies, has been exempted from municipal and domestic supply (MUN) uses, and is therefore not subject to drinking water standards. 

The RB is also responsible for determining how the beneficial uses are impaired by pollution under the CWA, and has recommended the Lake be listed for several impairments under CWA Section 303(d). Water quality standards used to determine impairment have been designated in the San Diego Region Basin Plan (Basin Plan, RB 1994). The Lake has been listed as impaired for ammonia as nitrogen and for nutrients (RB 2009), but the 2014 updates to the 303(d) list adopted by the RB also include phosphorus and copper (RB 2016) (Note: although the 2016 report has been approved by the RB, it has not been approved by either the SWRCB nor the U.S. Environmental Protection Agency [EPA], and the report therefore retains draft status). Impairments of the Lake are summarized in TABLE 1. 

The nutrient impairments listed in TABLE 1are consistent with the general eutrophic conditions observed at the Lake, and also contribute to nuisance vegetation issues in and around the Lake. Eutrophic conditions include elevated chlorophyll-aconcentrations (a surrogate measure of phytoplankton populations), infestations of aquatic plants (described below), and dense emergent vegetation. Water quality nutrient impairments at the Lake are being addressed through the RIFS process referenced above; several remedies have been identified at the Lake (and in the Watershed) and are in the planning and/or pilot stages. Alum (aluminum sulfate) treatment is amongst the pilot studies being conducted at the Lake. RIFS-remedies are designed to specifically address water quality conditions; measures included in this Plan will be tools to address excessive algae, aquatic nuisance plants, and emergent vegetation. 

TABLE 1. LAKE SAN MARCOS LISTINGS UNDER CWA 303(D) 

Constituent                           Criterion                              Listing Date                            Listing Type 

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Ammonia                              0.025 mg/L                               2006                           2014 Water Quality              

(as Nitrogen)            (as Nitrogen), unionized                                                           Limited Segment 

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Nutrients                            Narrative                                    2006                              2014 Water Quality

                                                                                                                                          Limited Segment

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Phosphorus                      0.025 mg/L 1                              2006                             2014 Water Quality

                                                                                                                                          Limited Segment

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Copper                             3.1ug/L (CCC) 2                            2014                          Proposed New Listing 

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Phosphorus                     0.025 mg/L 1                               2014                           Proposed New Listing 

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1 Concentration not to be exceeded more than 10 percent of the time. 

2 Criterion derived from the California Toxics Rule per Basin Plan (RB 2016); value presented is          not hardness-corrected; CCC - criterion continuous concentration. 

mg/L – milligrams per liter ug/L – micrograms per liter 

Excessive algae, aquatic nuisance plants, and emergent vegetation all exhibit unique seasonal patterns and ecologies, and therefore require separate management approaches. Each is described below. 

Excessive algae populations (including phytoplankton) have generally exhibited as elevated chlorophyll-aconcentrations and reduced water clarity. These conditions have historically persisted year-round, with some visual changes occurring during and immediately following wet weather events. Wet weather events typically disrupt the phytoplankton populations, but do not result in any long-term diminishment of eutrophic conditions. Over the past 5 years of monthly monitoring, chlorophyll–a concentrations typically peak in the summer. In the summer of 2017, peak algal populations were elevated to a degree that the state was notified of a potential harmful algal bloom at the Filamentous algae, and associated algae mats, are therefore also potential issues at the lake, but may not coincide with increased chlorophyll-ain the water column and reduced water quality. Lake. Amongst the management techniques during this bloom was manual removal of algal mats; this approach alone was not successful either in the short term (for the bloom event) or the long term (since the bloom coincided with thick beds of widgeongrass [Ruppia maritima] in region of the Lake with the highest impact [the northern lobe]). It is noteworthy that the magnitude of of algal bloom and widgeongrass extent was observed following a very wet winter (2016-2017); such intense ecological climax events were not observed during the prior 4 summers, which were all considered drought years. 

Aquatic vegetation issues, as stated above, are currently dominated by concerns that widgeongrass will return on an annual basis during the summer and fall. The extent of widgeongrass in 2017 was dramatic in extent: recreational uses in the upper basin were restricted due to propeller fouling, and extensive labor was used to remove the weed both using a harvester and by direct manual labor; these techniques were not successful. The widgeongrass was an issue for recreational Lake users until the mid-Fall when vegetative senescence occurred (as expected). However, widgeongrass is not the only concern: other aquatic plants have been observed in the past as well, and are potential issues which may require additional tools to manage appropriately. Other aquatic weeds observed historically include: pondweeds (Potamogeton spp.) and watermilfoil (Myriophyllum spicatum) (Note: this is not considered an exhaustive list). 

Emergent vegetation is present at the lake in two general forms: native species such as rushes, cattails, and willows; and non-native species, which primarily consist of water lilies. For native plants, maintenance of rushes and cattails are most of concern due to their propensity to dominate shallow shorelines (in both natural and urban parts of the lakeshore) or block infrastructure (e.g., golf course irrigation intake pipe). For the native species, removal by hand has been undertaken, but additional tools may be necessary to manage emergent vegetation issues proactively with minimal use of herbicide. For non-native species (water lily), the population has expanded significantly in some areas of the lake, and also have the capacity to interfere or block boat and/or dock access. In this case as well, strategic use of herbicides may be used in addition to manual removal for the preservation of recreational uses (e.g., boat access from docks to the open water). 

The treatment areas covered by this APAP differ according to several issues, and is described as follows: 

1. For water column algae, the area of concern covers the extent of the entire Lake; 

2. For aquatic plants, the treatment area extends from the shoreline to open water, and is dependent on site-specific recreational uses (i.e., boating and navigation); and 

3. For emergent vegetation, the treatment area is along the shoreline where vegetation may interfere with irrigation system infrastructure (at the northern end of the Lake), or in the vicinity of recreational uses (e.g., docks). 

TABLE 2 includes the proposed algaecides and herbicides to be used at Lake San Marcos. It is noted that the use of copper containing products are excluded from this list at the current time in consideration of the proposed Clean Water Act Section 303(d) listing of the Lake for copper. 

TABLE 2. PROPOSED ALGAECIDES AND HERBICIDES AND MODE OF APPLICATION 

Pesticide                           Trade                                 EPA                             Method of                Adjuvant

Herbicide                  Product Name                Registration No.                Application  

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Glyphosate                Aquamaster,                     524-343,                              Spray                        NONE

                                         Aquapro                       62719-324-                   nozzle system 

                                                                                   67690 

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Diquat                            Reward                          100-1091                            Spray                         NONE

                                                                                                                      Nozzle System  

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Sodium                           Pak 27                            68660-9                        Broadcast                      NONE

Carbonate                                                               -67690                           System 

Peroxyhydrate 

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Sodium                          Lake Guard                     93647-2                        Spray Nozzle                 NONE

Percarbonate                     Oxy                                                                        System 

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Peracetic Acid               Green Clean                  70299-19                       Spray Nozzle                 NONE

(Hydrogen Peroxide      Liquid 5.0                                                                  System 

+ Peroxyacetic Acid) 

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Fluroridone                   Sonar Q,                        67690-54                      Broadcast and/               NONE  

                                      Sonar One                       67690-45                      or spray/nozzle

                                                                                                                             System

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Endotholl                     Aquatthol                        4581-204                         Broadcast                      NONE

                                                                                                                            System

Aquatic nuisance vegetation and/or algae arise out of many factors influencing Lake conditions. These factors include instantaneous conditions such as temperature, light, lake nutrient concentrations, and vegetative substrate as well as other factors with longer time-horizons including preceding wet season stormwater flows, extent and magnitude of stratification in the deep lake, recency of flow events. These factors will collectively be weighed to judge the degree to which beneficial uses are degraded, and the likelihood that the degradation will continue and/or become more severe if nuisance vegetation or algae are not addressed. 

For algae and cyanobacteria, the Lake is listed as impaired as a result of nutrients and ammonia as N. Loading sources include both lake sediments as well as sources from the watershed (DBSA 2016). Nutrients are typically generated during the wet-season, and transported to the Lake via stormwater inputs. These nutrients are then present in the water column and also in Lake sediments. Later in the season (i.e., summer/fall), the deep lake area is typically stratified and nutrients released from sediments to the water column. Destratification is important from a nutrient standpoint, since deeplake nutrients are typically distributed throughout the water column and Lake during a destratification event. This, or other primarily physical factors may result in excessive algal growth which threatens beneficial uses in a myriad of ways. Examples of degradation of beneficial uses may include decreased habitat for aquatic plants as a result of shading, reduced benthic invertebrate densities and as a result less robust fish populations, dissolved oxygen reduction (to below Basin Plan objective of 5 milligrams per Liter), and harmful algal blooms (HABs) along with their risks to human and animal health. 

Dense nuisance vegetation (aquatic and emergent) likewise has the potential to threaten beneficial uses if growth becomes so dense as to impede water circulation, serve as a substrate for cyanobacteria mats (i.e., HAB condition), fouling of irrigation conveyance systems, and limiting navigation. These conditions when present in excess may in turn produce aesthetic issues, odors, and changes that limit optimal ecological functioning. 

For these circumstances, the decision to use a algaecides, herbicides, or other control measures will be undertaken when other measures have been exhausted. With regard to the requirements of Section XIII.C.11 of the Permit, the following will be considered: 

1. No action. Without the presence of excessive algae or vegetation (i.e., including areas of the Lake where conditions are not present), no herbicide or algaecide application action will be taken (see Cultural Controls, below). 

2. Prevention. Management of Lake resources will be undertaken to prevent the promotion or exacerbation of excessive algae or vegetation issues. Such management will include measures outlined in the Lake Management Plan (currently in draft form) to use best management practices (BMPs) with regard to operational controls, and promote BMPs in the immediate vicinity of the lake to prevent pollution of the Lake. 

3. Mechanical Control. Mechanized algae and vegetation removal is familiar to LSM operations staff and will be used in the future to control nuisance conditions to the extent feasible. 

4. Cultural Controls. The Lake is currently in the process of remediation that will promote conditions less favorable to algae, and to cyanobacteria in particular. Control measures include proposed phosphorus inactivation in the Lake and Upper San Marcos Creek, the use of a Selective Withdrawal system to promote mixing, and watershed infiltration to reduce phosphorus loading to the Lake ecosystem. Such measures are expected to affect the Lake over the next several years, as implementation will be phased (pilot studies are underway). 

Emergent and aquatic vegetation is typically native vegetation (e.g., cattails, rushes, widgeongrass, pondweed) that either re-establishes from remnant vegetation on an annual basis (e.g., cattails or widgeongrass from rhizomes) or due to natural colonization (e.g., from the Upper San Marcos Creek or from other areas of the Lake). Such establishment would be managed under this plan with the use of a minimal amount of herbicide applied early in the growing season (as opposed to a larger amount of herbicide being used later in the season to treat a greater amount of biomass). For native aquatic vegetation and non-native species (e.g. water lilies), the extent of herbicide application be reviewed and limited to areas where growth threatens operation of Lake infrastructure (e.g., pump intake), conflicts with recreational beneficial uses (e.g., boating, fishing), or is a threat to other beneficial uses (e.g. native wildlife). 

5. Biological Controls. With regard to biomanipulation, the fish populations of Lake San Marcos 

are currently managed as catch-and-release fishing only, and as such are managed to promote a self-regulating ecological system. Fishery management will continue in concert with remediation measures referenced above, and is anticipated to promote a healthy ecological system. 

The Lake is an impoundment of San Marcos Creek, and Lake level is primarily controlled by the presence of the Lake San Marcos Dam (Dam). The dam is designed to allow overtopping of high flows associated with the wet weather season. 

The dam was originally engineered to include a valve at the bottom of the Dam. The valve is operated manually at the discretion of the Lake management team. The valve has historically been operated to be open during wet-weather events and closed for the remainder of the season. The exception to this generalization is when the valve is opened as part of an annual safety inspection conducted by the state’s Division of Safety of Dams, typically in summer. Inspection of the valve is also undertaken prior to opening and following closure of the valve to ensure proper operation; the schedule of these inspections by Lake operations staff varies depending on the timing of rainfall events. 

With respect to dam overtopping or valve release, control of herbicide or algaecide migration downstream will be managed such that application will be undertaken under the following conditions (in addition to label instructions): (1) when the Dam is not overtopping and the valve is closed, and is anticipated to remain in that condition for 1 week; OR (2) such that application of herbicides and algaecides will be undertaken only on the upper portion of the lake length such that the Lake area within 1000 feet of the Dam will serve as a buffer to potential downstream transport. It is noted that excessive algae and vegetation conditions typically arise in the late spring through early fall when release of water downstream is minimal. In addition to the above constraints, the Lake management team will consider any other conditions present and avoid, minimize, or exclude the potential for downstream herbicide or algaecide migration, when feasible. 

The lake level is also managed through the use of a complex system of irrigation and groundwater replenishment. Irrigation water is removed from the Lake near the mouth of San Marcos Creek and used to irrigate the St. Mark Golf Course (SMGC). During summer months (when surface flow is minimized and irrigation need is greatest), the Lake water is replenished with groundwater to maintain the recreational use of the Lake. Although there is no indication that herbicide and/or algaecide applications would affect irrigation uses, the Lake manager will be tasked with coordinating with SMGC managers to ensure that herbicide applications do not negatively impact golf course greens. 

CDC has not been granted an exception to Section 5.3 of the SWRCB’s Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays. 

The Permit describes the minimal monitoring requirements of this APAP and are included by reference. The Permit is included as APPENDIX A. The monitoring program is designed to result in data-based documentation that the following questions are addressed: 

1. Does the residual algaecides and aquatic herbicides discharge cause an exceedance of the receiving water limitations? 

2. Does the discharge of residual algaecides and aquatic herbicides, including active ingredients, inert ingredients, and degradation byproducts, in any combination cause or contribute to an exceedance of the "no toxics in toxic amount" narrative toxicity objective? 

A summary of the monitoring program for Lake San Marcos follows. 

The first consideration in the algaecide or herbicide application process will be to assess the nature and extent of algae or vegetation issue. The assessment will include consideration of the spatial extent of the issue(s), vegetative species responsible for impairment, the dam overtopping status, anticipated/forecast wet weather, and other site-specific circumstances. This assessment will be conducted by Lake management staff and need communicated to the licensed applicator. Following evaluation of alternatives outlined in SECTION 5, the lake management team, in consultation with the applicator, will develop a algaecide/herbicide treatment approach. 

The Richland hydrologic subarea (904.52), in which the Lake lies, has been exempted from municipal and domestic supply (MUN) uses, and is therefore not subject to drinking water standards. As a result, the algaecides and herbicides listed in TABLE 1 do not have the potential to conflict with any of the Permit-referenced receiving water limitations (Permit, Table 3) with the exception of the toxicity narrative. This monitoring program addresses the toxicity narrative by documenting, among other provisions, that algaecides and herbicides are applied according to label instructions (see below). 

The monitoring program includes provisions to document of how this plan is implemented with regard to specific requirements outlined in the Permit. TABLE 3 includes monitoring provisions directly from the Permit. Sodium carbonate peroxyhydrate and peracetic acid (one of the algicides listed in TABLE 2) do not require monitoring as active ingredients under the Permit. Breakdown products of sodium carbonate peroxyhydrate (sodium carbonate, water, and oxygen) are non-toxic and do not persist in the environment for more than a few days (Solvay 2013). Breakdown products of peracetic acid include water, oxygen and carbon dioxide, which are non-toxic (Lenntech 2021). 

Conditions at the Lake are such that the time window of algaecide and herbicide application will be limited to conditions when water passing through the Lake system is either not flowing downstream or, if the dam is overtopping, a substantial buffer is in place (i.e., the exclusion of application within 1000 feet of the Dam; see SECTION 6.0). 

Monitoring will include collection of three types of samples: background (pre-event), during-event (immediately after treatment), and post-event (one week following treatment). The approach to monitoring will focus on collection of chemistry grab samples that are representative of conditions in time, and visual and physical parameter monitoring will be undertaken contemporaneously so as to generate a complete record of conditions. This APAP is applicable to both large-scale and small targeted applications; monitoring approaches differ for these event types and are described below. 

The background sample is intended to document general pre-treatment conditions. If treatment is generalized across a large area of the Lake (e.g., algaecide application) and it overlaps with a lake monitoring station (Station) see SECTION 8.7), the background samples should be collected at the closest Station to the application site. If treatment is targeted on a small area of the lake (e.g., water lily treatment for a length of shoreline), the specific application target area should be monitored. 

Background samples are to be collected within a 24-hour period preceding application.   

The during-event sample is intended to assess whether or not the algaecide or herbicide is migrating outside the treatment area within a relatively short duration of time, or is otherwise impacting an area outside the target treatment area. As the Lake generally conforms to conditions of a standing body of water (as opposed to flowing), the during-event monitoring will take place within a time window of no less than 2 but not greater than 20 hours following application at the station adjacent to the respective application area. 

The post-event sample will be collected from the area of application one week following completion of the application. Ideally, the post-event sample should be collected from both the same location as the background area sample AND from within the treatment area. Furthermore, if the treatment area overlaps with a Station, that location should be prioritized (but not at the expense of sampling the treatment area). 

Conditions at the algaecide or herbicide application point will be monitored and logged to document background and post-event conditions. Monitoring will include logging a description of the area, a qualitative description of the receiving water condition, and weather observations. Logs will include the presence of floating or suspended matter, color, visible bottom deposits, a general description of aquatic life, visible films/sheens/coatings, notes of fungi/slime/objectionable growths, and note of potential nuisance conditions. An example log is included in APPENDIX B. 

Physical monitoring will, like the visual characterization, be undertaken to document background and post-event conditions. Physical parameters will be measured using calibrated instrumentation such as a Hydrolab or YSI sonde. Real-time data will be recorded on log sheets and include temperature, pH, and conductivity as noted in TABLE 3. Turbidity may be recorded using instrumentation or, alternatively, may be included as a laboratory analysis conducted as part of the chemical monitoring. An example data log is included in APPENDIX B. 

Grab samples will be collected during background, during-event, and post application monitoring events. Grabs will be collected at a depth of 3 feet if the water depth is greater than 6 feet, or at middepth if water is shallower. Grab samples will be collected using water sampling equipment (e.g. a van Dorn sampler) and distributed to clean containers supplied by the laboratory. Equipment will be maintained in a clean condition, thoroughly rinsed before and after use, and surfaces coming in contact with sample media rinsed using site-water prior to each deployment. Alternatively, sample containers may be used to collect samples directly or with a pole equipped with a container mount system. 

Prior to sample collection, clean sample containers provided by the analytical laboratory will be affixed with labels including the entity collecting the sample, the site name (LSM), the date, and a sample identifier. The sample identifier may use a standardized code, for example, one denoting the date of the sample, the station location (“A” through “E”, see below) and event (e.g., “BG” for background, “ME” for during-event, or “MP” for post event). Filled sample containers will immediately be placed in iced coolers and retained within the custody of the field team. A courier will transport samples to the analytical laboratory no later than 24 hours following sample collection. Temperature blanks will be utilized to document handling conditions during transit, and chain-of-custody documentation will be used to document sample transfers as well as requested analyses. 

Monitoring Stations have been established at the lake for 6 areas coinciding with the deep lake near the dam (Station A and AB), moderate depth within the lower Lake (Station B), shallow central Lake (Station C), shallow upper central Lake (Station D), and shallow upper basin (Station E) (FIGURE 2). These stations have been monitored on a monthly basis for approximately 5 years, and have served as representative stations per CDC’s Lake Investigation Workplan (CDC 2012). These stations will continue to serve as representative stations under this APAP for broad-distribution algaecide and herbicide applications undertaken within respective areas. Prior to broad application of an algaecide or herbicide, the extent of the treatment area will be assessed in the context of monitoring requirements and whether the treatment area(s) overlap with established monitoring stations. 

Alternatively, if targeted applications are undertaken and application areas do not overlap with the established monitoring location (e.g., for water lily treatment along the shoreline), the specific treatment areas will be used as sampling locations for the background and post-event monitoring. In this case, the closest available established monitoring station (A through E) will be used for the duringevent monitoring. 

Alternatively, if targeted applications are undertaken and application areas do not overlap with the established monitoring location (e.g., for water lily treatment along the shoreline), the specific treatment areas will be used as sampling locations for the background and post-event monitoring. In this case, the closest available established monitoring station (A through E) will be used for the during event monitoring.  A, B, and C. As an alternative example, if  algaecides are applied in all areas of the lake with the exception of the dam exclusion zone, background and post-event samples would be collected at Stations AB, B, C, D, and E, and during-event sample(s) would be collected at Station A. 

Laboratory analyses will be undertaken by laboratories certified for such analyses by the California Department of Public Health in accordance with California Water Code section 13176. The precision and accuracy of the data will be assessed using data generated from analysis of laboratory duplicates, matrix spikes, surrogates, and laboratory control samples conducted according to laboratory standard operating procedures and in compliance with both EPA-approved methods and laboratory certifications. Field-generated quality control samples will not be collected under this plan. Laboratory data reports will be reviewed to assess the results with the context of laboratory quality assurance analyses, and a data validity assessment included in the annual report. 

Record retention is required under this APAP for all monitoring information, including calibration and maintenance records, copies of all reports, original laboratory reports. Records shall include the date place, and time of sampling or measurements; records of individuals who performed the sampling or measurements, the dates, types, and specific techniques of analyses performed, records of individuals who performed such analyses, and the results of such analyses. Records must be retained for a minimum of three years from the date of sampling, measurement, or report, and may be extended when requested by the Regional Board Executive Officer.

Reporting shall be undertaken annually and submitted by March 30 of each year for the preceding calendar year in compliance with provisions stated in Attachment D of the Permit. If no discharge of algaecides or herbicides were made, a certification will be made in compliance with the Permit (Attachment C, Section C.IV.c). If application was undertaken, the monitoring report will include: 

1. An Executive Summary including an indication of compliance or violation of the Permit and provisions in this APAP, and a summary of monitoring results which assess an improvement or degradation of water quality as a result of algaecide or herbicide application; 

2. A summary of monitoring data and results presented in comparison to applicable receiving water limitations, and including, if applicable, recommendations on how this APAP may be improved; 

3. A discussion of BMP effectiveness, and if applicable modifications to this APAP to address any violations; 

4. Maps showing the locations of treatment areas; 

5. Types and amounts of algaecides and herbicides used during each application event; 

6. Information on surface area and/or volume of treatment area and any other information used to calculate dosage, concentration and quantity for each application; 

7. Reporting information concerning information generated in the report including: organizations and individuals responsible for application and monitoring, information and sample collection dates, location information, parameters tested along with quality assurance data, and including summary tables with tabulated results; and 

8. Summaries of the application logs. 

These reports will be prepared in a manner such that information is clear, concise and readily discernable and submitted to the Executive Officer of the California Regional Water Quality Control Board, San Diego Region as specified in the Permit. 

Non-compliance, including any unexpected or unintended effect of the use of an algaecide or herbicide that may pose a threat to health or the environment, will be reported orally within 24 hours of the incident. A written report of the non-compliance incident will be reported within 5 days. Reports will include information described in Attachment C of the Permit. 

A variety of approaches will be used to carry out algaecide and herbicide treatments responsibly, effectively, and in a manner which minimizes impacts. 

Algaecides and herbicides are by nature biologically active substances, and care must be taken to release these chemicals in a manner consistent with instructions. Spill prevention is an important consideration from before the time of procurement or delivery of the algaecide/herbicide, and will be undertaken such that transport, handling, and storage is undertaken by qualified individuals who will follow spill control procedures recommended by the California Department of Pesticide Regulation and Environmental Protection Agency. 

At the time of application, reliable equipment which has been maintained in a clean and calibrated manner will be used to ensure that the intended dose is delivered and that treatment is not in excess of product manufacturer directions for use. 

The timing and manner of treatment will also be considered in advance of application such that: 

1. Alternative control methods have been exhausted; 

2. Pre-treatment surveys have been conducted to identify the minimum area of treatment; 

3. Site- or time-specific conditions are reviewed to ensure that conditions are appropriate for the intended application; 

4. Downstream transport potential is minimized or eliminated through timing of application during dry conditions and/or incorporation of the dam-buffer zone; 

5. Pesticides are chosen to best address the condition requiring treatment; and 

6. Dosage rates are limited to ensure that receiving water limitations are not exceeded and pesticide label instructions are followed. 

Pesticide applications will be undertaken by California-licensed or –certified applicators; applicators will have completed required initial and continuing education requirements. This plan, with this provision, will be provided to the applicator to ensure compliance with provisions of this APAP. 

Public agencies will be informed of plans to apply algaecides or herbicides in compliance with provisions outlined in the Permit (Section VIII.B). Notice will be provided at least 15 days in advance of application to the Regional Board, the County of San Diego, and the City of San Marcos at minimum. 

Advance coordination with SMGC will be necessary to ensure that irrigation uses are compatible with selected treatments. The SMGC operations staff will be included on communications with public agencies and informed of application plans. 

In addition, when the application schedule is developed, information shall be made available to the public via community groups and/or physical postings. Per the provisions of the Permit, the phone number of the Discharger will be made available to respond to questions regarding the application schedule, nature and purpose of application, and water use restrictions. 

Algaecide and herbicide product labels includes dosage rates and treatment information which lists recommended treatments and precautionary information which may prevent unintended effects such as fish kills. Fish kills in the context of this program may be caused if treatment at a high dose results in excess algae or vegetation biomass death. Excessive decay of dead algae or vegetation can deplete dissolved oxygen and cause fish kills. For this reason, the dosage of algaecides and herbicides will be undertaken in compliance with product directions for use, and preventative best management practices undertaken. These measures include: 

1. Consideration of the range of recommended dosing and restricting dosages to the lowest practical rate to target the minimum desired effect; 

2. Limiting application of algaecides and herbicides to a portion of the Lake when treating heavy bloom conditions so that fish have refuge areas during treatment; 

3. Allowing for a delay between treatments to reduce likelihood of impacts to fish; and 

4. Apply early in the day to allow for equilibration of oxygen levels during daylight hours. 

Application by Qualified Applicator Certificate or License holders have knowledge of the proper equipment operations such that spills scenarios are minimized, applications rates are made according to the product labels, target algae or vegetation is treated effectively, and that the application systems are properly calibrated. These factors all contribute to a minimization of fish kill event likelihood. 

SECTION 5 includes a discussion of management options available at Lake San Marcos including no action, prevention, mechanical or physical methods of removal, cultural and biological methods to address excessive algae or vegetation, and the use of algaecides and herbicides. These factors are all weighed during the assessment phase of the planning process prior to a decision to treat with algaecides or herbicides. 

With regard to the current impairments of the Lake, several efforts are underway at the Lake and in the watershed which will significantly decrease nutrient inputs to the Lake system (SECTION 2.1and DBSA 2016). Final corrective actions are expected to dramatically improve Lake water quality such that impairment conditions are addressed and algaecide and herbicide use is either limited or eliminated. 

Key to this evaluation and planning process is an understanding of the extent and magnitude of the impairments, factors contributing to exacerbation of the impairments, and an assessment of how treatment may affect the environment. When feasible and conditions are suitable, alternative control strategies will be implemented. However, when necessary to control nuisance conditions, provisions of this APAP will guide treatment with algaecides or herbicides in compliance with the Permit. The careful evaluation of alternative modes of addressing nuisance conditions will lead to a suite of control measures that have the least impact and simultaneously preserve and enhance beneficial uses.
 

Citizens Development Corporation. 2012. Lake San Marcos Nutrient Impairments Investigation Workplan. June 2012. 

D. B. Stephens & Associates (DBSA), 2016. Remedial Investigation/Feasibility Study Report, Upper San Marcos Creek Watershed and Lake San Marcos. Prepared for Citizens Development Corporation and Public Agency Defendants. September 30. 

Lenntech. 2021. Disinfectants Peracetic Acid. Available at : https://www.lenntech.com/. Accessed April 14, 2021. 

Regional Water Quality Control Board, San Diego Region. 2011. Investigative Order No. R9-20110033, For the Investigation of Nutrient Impairment in Lake San Marcos San Diego County. September 14. 

Regional Water Quality Control Board, San Diego Region. 2013a. Order No. R9-2013-0001 NPDES No. CAS0109266. National Pollutant Discharge Elimination System (NPDES) Permit And Waste Discharge Requirements For Discharges From The Municipal Separate Storm Sewer Systems (MS4s) Draining The Watersheds Within The San Diego Region. May 23. 

Regional Water Quality Control Board, San Diego Region. 2017. Resolution No. R9-2017-0038, A Resolution Supporting The Path Forward For Nutrient Load Reductions In Lake San Marcos And The San Marcos Creek Watershed. March 15. 

Solvay America, Inc. 2013. Product Safety Summary, Sodium Percarbonate (Sodium Carbonate Peroxyhydrate), CAS No. 15630-89-4. 

State Water Resources Control Board. 2013. Statewide General National Pollutant Discharge Elimination System (NPDES) Permit for Residual Aquatic Pesticide Discharges to Waters of the United States from Algae and Aquatic Weed Control Applications. Water Quality Order No. 2013-0002-DWQ General Permit No. CAG990005 (As amended by Orders 2014-0078-DWQ, 2015-0029-DWQ, and 2016-0073-EXEC). Adopted March 5. 

APPENDIX A: 

STATEWIDE GENERAL NATIONAL POLLUTANT DISCHARGE ELIMINATION 

SYSTEM (NPDES) PERMIT FOR RESIDUAL AQUATIC PESTICIDE 

DISCHARGES TO WATERS OF THE UNITED STATES FROM ALGAE AND 

AQUATIC WEED CONTROL APPLICATIONS; 

WATER QUALITY ORDER NO. 2013-0002-DWQ; GENERAL PERMIT NO. CAG990005 

[INCLUDE IN FINAL VERSION] 

APPENDIX B: 

FIELD APPLICATION LOG AND 

FIELD OBSERVATIONS LOG 

  
See File here