In September of 1994, Pinellas County entered into an agreement with Coastal Environmental, Inc. (subsequently purchased by PBS&J, Inc. in 1996) to prepare the Lake Tarpon Drainage Basin Management Plan (the Plan). Building upon the work of the diagnostic/feasibility study, the Plan is to be composed of management policies and best management practices - both structural and non-structural - aimed at restoring and/or maintaining the hydrological and ecological integrity of the lake and its immediate watershed. As such, the Plan should specifically include recommended management options and BMPs addressing priority lake and watershed management issues identified by the Lake Tarpon Management Committee (LTMC).
This document - The Lake Tarpon Drainage Basin Management Plan - represents the culmination of a decade of resource planning activity undertaken by numerous governmental agencies and key individuals. The management actions recommended herein are based on the extensive knowledge gained from the scientific/engineering studies and monitoring programs conducted to date, and represent the most cost-effective means of attaining the adopted goals of the LTMC.
The primary purpose of the Lake Tarpon Drainage Basin Management Plan is to provide implementation guidance for the Pinellas County Growth Management Plan with respect to lake, wetland, and upland management issues in the Lake Tarpon basin. As such, the Plan is to provide specific recommended management options addressing the following management objectives:
reduce pollutant and nutrient loadings from both internal and external sources;
improve lake water quality (e.g. reduce TSI; meet applicable state water quality standards);
control nuisance and exotic aquatic vegetation;
increase the quality and diversity of in-lake and watershed natural habitats;
sustain or enhance a balanced assemblage of endemic sport fisheries and wildlife;
provide for public flood protection;
maintain or enhance the aesthetic and recreational attributes of the lake;
maximize and balance recreational opportunities for all user groups; and
advance public knowledge and understanding of the lake ecosystem and its watershed.
Because concern over declining water quality was the original driving force behind the planning process, the primary focus of the Plan was the development and evaluation of various BMPs and other structural and non-structural remediative measures to reduce external and/or internal pollutant loadings to Lake Tarpon, while maintaining effective public flood protection. The reach of the Plan, however, extends well beyond water quality and flood control issues. Using the evolving "ecosystem management" approach, the Plan addresses the interactions between water quality and quantity, and dependent living resources such as fish, wildlife and natural habitats.
A total of seven priority lake and watershed management issues were identified by the LTMC. A brief summary of the problem statement associated with each priority issue is provided below.
Issue #1 - Water Quality: Excessive nutrients in surface waterbodies can lead to declining water quality and associated ecological degradation. The process of excessive nutrient enrichment is referred to as eutrophication. Available monitoring data indicate that water quality in Lake Tarpon, as measured by chlorophyll-a and nutrient concentrations, is declining. There is a justifiable concern that eutrophication is advancing to a level where other adverse ecological changes could soon follow. Conversely, no significant public health related water quality problems, such as high concentrations of toxics or pathogens, have been observed in Lake Tarpon.
Issue #2 - Aquatic Vegetation: Available assessment data indicate that the diversity of emergent aquatic vegetation has declined significantly in the last 25 years with the implementation of a water level control schedule, and the resulting proliferation of monotypic stands of cattails dominating the shoreline of the lake. Cattails obstruct waterfront views and shoreline access, and provide poorer fish and wildlife habitat than other more desirable vegetation. In addition, keeping the coverage of nuisance submerged aquatic vegetation such as hydrilla in check presents a continuous management challenge. Large scale chemical treatments of hydrilla in Lake Tarpon have been correlated with degraded water quality, probably due to the water column release of nutrients from the excessive plant tissue decomposition.
Issue #3 - Fisheries: Lake Tarpon is one of the foremost sport fishing lakes in Florida. The largemouth bass and panfish fisheries are considered to be healthy, however, more recent assessment data indicate that fish biomass in Lake Tarpon has increased substantially since 1992, indicating a trophic state shift. There is a justifiable concern that advancing eutrophication in Lake Tarpon could threaten the integrity of the sport fisheries.
Issue #4 - Wildlife and Associated Habitat: Land development in the Lake Tarpon watershed has resulted in the loss of hundreds of acres of natural habitats and their associated wildlife populations. Although existing wetlands in the basin are well protected under federal and state laws, measures to protect remaining upland habitats are needed. Furthermore, urban wildlife management programs and techniques such as golf course and residential habitat enhancement could improve wildlife utilization of the basin.
Issue #5 - Flood Control: The construction of the Lake Tarpon outfall canal and water level control structure in the 1970s effectively addressed the severe flooding problems that existed in the basin prior to these actions. The primary concern with regard to the flood control issue in the Lake Tarpon basin is that the level of flood protection currently provided by the outfall canal and structure not be significantly compromised to accommodate the attainment of other lake management goals.
Issue #6 - Recreation and Aesthetics: Lake Tarpon is an important economic resource to Pinellas County and the City of Tarpon Springs due to the recreational aesthetic benefits it provides. Recreational benefits include sport fishing, boating (including personal watercraft), water skiing, and more passive uses such as canoeing and bird watching. Lake user surveys indicate that a high proportion of recreational boaters and skiers are attracted from neighboring counties, whereas sport fishermen are attracted from all of Florida and neighboring states. These surveys also indicate that conflicts exist between certain user groups, primarily water skiers and fishermen, who often pursue incompatible recreational activities in the same areas at the same time. As a result, the quality of the recreation experience, and possibly public safety, has been compromised. In addition, the highly attractive aesthetic environment provided by the lake adds considerable value to waterfront and nearby residential properties. There is a justifiable concern that unresolved user conflicts and degrading ecological conditions could adversely impact the socioeconomic benefits provided by Lake Tarpon.
Issue #7 - Public Education: Residential surveys of people living in the Lake Tarpon basin indicate that the general population is generally not knowledgeable regarding lake and watershed management issues. However, these same surveys indicate that many residents are interested in helping to monitor and improve environmental conditions in the lake and watershed. A need exists to better inform the public of issues facing Lake Tarpon and to solicit public support and volunteerism in the implementation of the Plan.
In addressing the above listed management issues, the Plan presents the development and prioritization of a wide range of recommended management options in an integrated manner. In addition to the evaluation of structural BMPs in the watershed, and in-lake remediative measures, the Plan further addresses the project objectives through a variety of regulatory, management, and policy components. The Plan is broken down into the following nine primary components.
1. Structural Components.
2. Management Components.
3. Legal Components.
4. Compliance and Enforcement Components.
5. Policy Components.
6. Social Components.
7. Public Education Components.
8. Operation and Maintenance (O&M) Components.
9. Monitoring Components.
A total of 22 specific management actions or components are recommended in the Plan. They include the following:
Structural Components (5)
Structural Component 1 - Convert All On-site Wastewater Treatment Systems (Septic Tanks) in the Lake Tarpon Basin to Central Sewer Systems.
Structural Component 2 - Construct and Maintain Enhanced Stormwater Treatment Facilities in the Priority MHUs and Individual Sub-basins.
Structural Component 3 - Construct Wildlife Crossing Structures at Strategic Locations Within the Lake Tarpon Basin.
Structural Component 4 - Install Stage and Flow Measurement Devices at the Lake Tarpon Outfall Canal Control Structure.
Structural Component 5 - Construct Pump Stations and Distribution Lines for the Storage and Beneficial Reuse of Lake Discharge Water.
Management Components (5)
Management Component 1 - Implement an Enhanced Lake Level Fluctuation Schedule.
Management Component 2 - Increase Lake Flushing and Dilution.
Management Component 3 - Implement a Mechanical Harvesting Program for Nuisance Aquatic Vegetation.
Management Component 4 - Inventory Permitted MSSW Facilities in the Lake Tarpon Basin and Develop Facility Improvement Plans.
Management Component 5 - Develop and Implement a Comprehensive Lake Tarpon Habitat Improvement Program (LT/HIP).
Legal Components (3)
Legal Component 1 - Amend the Florida Statutes to Specifically Define the Limits of the Lake Tarpon Outstanding Florida Waters (OFW) to Include "All Tributaries Thereto."
Legal Component 2 - Adopt a Resolution Designating the Lake Tarpon Basin as a "Nutrient Sensitive Watershed."
Legal Component 3 - Strengthen and Standardize Local Ordinances for Regulating Stormwater Treatment for Redevelopment in the Lake Tarpon Basin.
Policy Components (1)
Policy Component 1 - Establish a Lake Tarpon Watershed Management Area (WMA) via Amendments to the Pinellas County and City of Tarpon Springs Comprehensive Plans.
Compliance and Enforcement Components (2)
Compliance and Enforcement Component 1 - Assign a Full-time Pinellas County Marine Unit Sheriff to Enforce Restricted Speed Zones on Lake Tarpon.
Compliance and Enforcement Component 2 - Install Additional Buoy Markers For, and Post the Allowable Activities Within, the 200' Perimeter Restricted Speed Zone.
Social and Recreational Components (3)
Social and Recreational Component 1 - Investigate the Establishment of a Spatially Segmented Management Scheme for Recreational Uses of Lake Tarpon as a Means of Reducing User Conflicts.
Social and Recreational Component 2 - Establish a Public Pedestrian Fishing Trail along the West Side of the Lake Tarpon Outfall Canal.
Social and Recreational Component 3 - Provide for Night Access to Public Boat Ramps at Anderson Park.
Public Education Components (2)
Public Education Component 1 - Develop and Implement a Comprehensive Public Involvement Program for the Lake Tarpon Watershed.
Public Education Component 2 - Develop and Implement a Local Citizens LakeWatch Program on Lake Tarpon.
Operation and Maintenance Components (1)
Operation and Maintenance Component 1 - Perform Ongoing Operation and Maintenance Activities for Recommended Structural and Management Components of the Plan.
In addition to the 22 components listed above, the Plan includes a comprehensive monitoring program to evaluate the long-term success of Plan implementation.
The cost of implementing the Plan over a 10-year period has been estimated at $19,380,000. It should, however, be noted that design plans and specification have not been prepared for the major structural components of the Plan, and market-driven unit costs can vary significantly due to many factors. Nonetheless, the estimate of the total cost to implement the Plan was prepared with the best information available to date. Estimated costs can be broken down as follows:
Total Construction Cost
Total Annual Operation and Maintenance (O&M) Cost $948,000
Total Annual Administrative Cost $292,000
Total Cost through Year 2008 $19,087,000
The single largest construction cost item in the Plan involves the provision of sewage collection facilities to the existing 1,078 residences currently on septic tanks (Structural Component #1). It is estimated that approximately 915 of the 1,076 residences currently on septic tanks fall within the City of Tarpon Springs sewer district, with the remaining 161 residences falling within the Pinellas County sewer district. Based on this information, and an estimated construction cost of $8,610 per residence, the City of Tarpon Springs share of this project would be approximately $7,878,200; whereas the Pinellas County share is estimated to be $1,386,200.Because this management action is very costly, and is based on modeling data with little empirical data to verify actual loadings, it is recommended a site-specific field investigation be conducted to confirm the magnitude of the loadings before proceeding with construction. Furthermore, if it is determined from empirical field data that septic tanks in the basin are generating substantial TN and TP loadings (e.g., of the order of magnitude predicted by modeling) then it is recommended that the construction of central sewer collection facilities and the hookup of the 1,076 residences be completed in phases over a period of eight years (e.g., initiate construction in 2000, complete by 2008).
In addition, the above total annual O&M and administrative costs represent estimates for annual recurring costs for these activities associated with the entire suite of projects and programs recommended in the Plan. Therefore, for the estimated total cost through year 2008, it was assumed that all recommended construction projects would be completed by the year end 2003, and that all facilities and recommended programs would be fully operational for a period of five years (from 2004 through 2008).It should, however, be noted that many matching fund grant programs, and other public funding sources, exist to defray local government costs of Plan implementation.
In conclusion, the trophic state index target of 55 for Lake Tarpon is attainable, but achieving this target will require the full implementation of the major internal and external load reduction strategies of the Plan, including:
stormwater treatment in priority MHUs;
septic tank conversion;
macrophyte harvesting; and
enhanced lake level fluctuation with increased lake flushing and dilution.
It should be noted that the predicted attainment of the TSI target assumes that current conditions will prevail, and that no major hydrologic alterations or additional loadings will occur within the basin. Implementation of other non-structural components of the recommended Plan will likely lead to further load reduction which should provide a small safety factor to accomodate future growth. This point, however, underscores the importance of implementing the full Plan as proposed such that future growth and development in the basin will not lead to further degradation of water quality and associated living resources in Lake Tarpon.