CHAPTER FIVE INFRASTRUCTURE ELEMENT

Transcription

1 CHAPTER FIVE INFRASTRUCTURE ELEMENT DRAINAGE SUBELEMENT Updated: EAR BASED AMENDMENTS July 11, 2006, Ord. No A12 December 11, 2007, Ord. No A37 (Sanitary Sewer Sub-element) September 16, 2008, Ord. No A27 (Sanitary Sewer and Potable Water Sub-elements) November 10, 2009, Ord. No A24 (Sanitary Sewer and Potable Water Sub-elements)

2 February 14, 2012, Ord. No A02 (Drainage Sub-element) February 26, 2013, Ord. No A04 (Potable Water Sub-element) February 25, 2014, Ord. No A06 (Drainage Sub-element) February 28, 2017, Ord. No A09 (Sanitary Sewer, Potable Water, and Drainage Sub-elements

3 I. INTRODUCTION A. Purpose Proper stormwater drainage is essential for adequate protection of the County s water resources and public health and safety. The potential environmental and economic impacts of uncontrolled stormwater drainage have led to a management and regulatory framework established by local, state, and federal government. The purpose of this element is to establish the County s policy directives for managing stormwater drainage. The characteristics of drainage patterns and associated limitations within Citrus County are incorporated into the drainage plan. B. Terms and Concepts 1. Drainage Systems Water flowing overland during and immediately following a storm event is called stormwater runoff. Under the effect of gravity, water flows towards sea level through depressions and channels or by sheetflow over flat terrain. The drainage system may consist of natural features, manmade features, or a combination of both. Natural drainage systems are defined by the topography of an area. The largest feature is the drainage basin or watershed. The boundary of a basin is referred to as the basin divide. The basin divide is a line where the natural land elevation directs runoff within the basin toward a common major drainage feature. A major drainage feature is referred to as a receiving body and smaller features are tributaries. Manmade drainage facilities features are designed to detain, store, or convey stormwater runoff. Swales, ditches, canals, and storm sewers are typical conveyance structures, which collect stormwater runoff and direct it toward downstream receiving facilities. Stormwater storage structures are classified as either detention or retention facilities. Detention facilities are designed to temporarily impound runoff and release it gradually to downstream portions of the drainage system through an outlet structure. Retention facilities are impoundments, which release stormwater by evaporation and percolation, with no direct discharge. 2. Drainage and Stormwater Management Stormwater runoff is highly variable and dependent upon the amount of rainfall during each storm event and conditions of the drainage basin. Since most storm events are relatively moderate, natural drainage features typically evolve to accommodate moderate quantities of runoff. Periodically, severe storm events 5-120

4 create runoff volumes exceeding these drainage features holding capacities, resulting in temporary high water levels. This periodic high water level (flood) is a naturally occurring event and has many beneficial effects in the cycle of the basin s ecosystem. Flooding or high water levels are generally not perceived as a problem until development occurs in floodprone areas. Historically, the typical strategy adopted in response to stormwater flooding of developed areas was to modify the drainage system to convey runoff away from developed sites more rapidly. This strategy with increasing urbanization results in proportionately faster runoff during storm events. In addition to controlling flood problems, this strategy for coping with stormwater runoff has detrimental effects on water quality. Soil eroding from development sites and materials such as oil, grease, pesticides, and fertilizers from urban and rural land uses are washed off by runoff, increasing the pollutant loading on receiving waters. The term stormwater management refers to comprehensive strategies for addressing stormwater quantity and quality issues. The combined goal of stormwater management strategies is to ensure that the volume, rate, timing, and pollutant load of runoff after development is similar to that which occurred prior to development. To accomplish this, a combination of structural and nonstructural techniques is utilized. Structural techniques emphasize detention and retention of stormwater to reduce runoff rates and provide settling and filtration of pollution. Nonstructural techniques emphasize preservation or simulation of natural drainage features to promote infiltration, filtering, and reducing the rate of runoff. The objective of stormwater management is to utilize the combination of techniques, which provides adequate pollution removal and flood protection in the most economical manner. C. Regulatory Framework The U.S. Environmental Protection Agency has published rules to implement the National Pollutant Discharge Elimination System (NPDES) as mandated under Section 402(p) of the Clean Water Act. The State of Florida submitted a request to the EPA for delegation of NPDES permitting. A main component of this permitting process will be submittal of a Stormwater Pollution Prevention Plan (SWPPP) to identify and mitigate both stormwater and non-stormwater flows. In Florida, the DEP is responsible for regulating stormwater throughout Florida. This regulatory role has been delegated by the DEP through a formal agreement to the Southwest Water Management District (SWFWMD). Within Citrus County, the SWFWMD is responsible for stormwater drainage

5 Sections 373 and 402, F.S., provide the SWFWMD specific authority to regulate stormwater drainage. Chapter 40D-4 and 40D-40, F.A.C., provide rules within SWFWMD for the management and storage of surface waters. Locally, stormwater management is regulated by the County. The Department of Public Works administers the requirements of the Stormwater Drainage Appendices of the LDC. II. INVENTORY A. Background The Southwest Florida Water Management District has identified watershed management as a major component for protection of water resources and the environment. State Water Policy defines a watershed management goal as an overall goal which provides the general strategies for the management of water resources within a watershed. The goal will be developed to be consistent with the Surface Water Improvement and Management (SWIM) program(s) and the NPDES program. The U.S. Geological Service has delineated watersheds at four levels of detail. Level One delineations show approximately 10 watersheds in the SWFWMD up to Level Four showing 1,000 watersheds. An interdisciplinary SWFWMD staff workgroup has chosen 23 delineated basins, comprised of watershed from Levels One and Two for development of preliminary watershed management goals. The District will prepare a comprehensive surface water approach that will encompass flood protection, water quality, natural systems management, and where appropriate, water supply considerations. The results of this initiative will be used for a variety of purposes including specific implementation strategies for each watershed in conjunction with federal, state, and local agencies. Intergovernmental coordination will then prioritize activities to provide maximum effective use of available funding. 1. Basins and Subbasins Citrus County is divided by a drainage divide, which forms the Coastal Rivers and Withlacoochee Basins. This drainage divide begins in the south central area of the County and gradually curves westward below the junction of the Withlacoochee River and the Gulf of Mexico (Figure 5-11). The Coastal Rivers Basin is drained by the Crystal, Homosassa, Halls, and Chassahowitzka Rivers. These river systems receive the majority of their volume from coastal springs and the seepage of groundwater, rather than surface runoff 5-122

6 from the surrounding watershed (Glace and Radcliffe, Inc., 1981). However, stormwater runoff is increasing due to urbanization of the lands within the respective watersheds. The Coastal River Basin consists of a large buffer area of saltwater marsh bordered by a land of freshwater swamp west of US-19. Traveling east from US- 19 the land elevations increase to a maximum at the eastern edge of the basin, which is located in the sand hills (Brooksville Ridge). Whereas the sand hill areas provide excellent infiltration and recharge for stormwater runoff, the areas bordering US-19 contain poorly drained soils that require appropriate stormwater management techniques to protect water quality. The Coastal Rivers Basin has been divided into 27 subbasins (Figure 5-11). The land area contained in each subbasin is shown in Table Since drainage basins do not conform to political boundaries, some of these subbasins consist of portions outside the County. Particular basins as noted were calculated to include only that portion which is in Citrus County. The Coastal River Basin contains the Crystal River/King s Bay area, which is a designated SWIM project. The County, in coordination with the City of Crystal River and SWFWMD, have implemented strategies developed under this program, as well as, utilized them in other areas within the Basin when applicable. The Withlacoochee River Basin covers the eastern half and northern edge of Citrus County (Figure 5-11). The Withlacoochee River, the major drainage feature of the Basin has its headwaters in the Green Swamp. The river meanders 157 miles northward to the Gulf of Mexico and forms the eastern and northern boundaries of Citrus County. This Basin is divided into 39 subbasins, which are listed in Table TABLE 5-12 COASTAL RIVERS BASIN Subbasin Area (acres) Subbasin Area (acres) C-1 40,967 C-15 1,690 C-2 13,594 C C-3 2,773 C-17 3,996 C-4 3,240 C C-5 3,140* C-19 6,575 C-6 1,631 C C-7 2,149 C-21 2,182 C-8 1,466 C-22 7,221 C C-23 5,781 C-10 1,051 C-24 6,465 C-11 1,153 C-25 1,785 C-12 10,626 C-26 88,760* C-13 13,407 C-27 1,377 C-14 1,690 Note: *Area of Basin within Citrus County Source: Glace and Radcliffe, Inc., 1981 Prepared by: Citrus County Community Development Division,

7 TABLE 5-13 WITHLACOOCHEE RIVER BASIN Subbasin Area (acres) Subbasin Area (acres) W-1 2,094 W-21 1,381 W-2 5,748 W-22 2,773 W-3 1,093 W-23 8,230 W-4 13,028* W W-5 1,387 W-25 4,885 W-6 3,636 W-26 1,965 W-7 10,257* W-27 6,511 W-8 1,644 W-28 1,230 W-9 2,747 W-29 2,571 W-10 1,230 W-30 3,453 W-11 2,213 W-31 3,398 W W-32 1,253 W-13 2,130 W-33 2,002 W-14 2,610 W-34 1,702 W-15 2,525 W-35 5,811* W-16 1,286 W-36 7,686 W-17 4,623 W-37 16,621 W-18 9,972 W-38 4,011 W-19 1,747 W-39 12,635 W-20 3,737 Note: *Area of Basin within Citrus County Source: Glace and Radcliffe, Inc., 1981 Prepared by: Citrus County Division of Planning, Environmental Factors There are many factors, which affect the surface water drainage of a basin or watershed. These factors include climate, topography, geology, hydrology, and soils. The following discussion summarizes these factors by characterizing drainage within Citrus County. A more detailed discussion is contained within the Conservation Element. The climate of Citrus County is typical of a low-lying subtropical area. The summers are warm and relatively humid, while winters are mild and relatively dry. Citrus County receives 55 inches of rainfall annually. More than one-half of the annual rainfall occurs during the months of June through September

8 5-125 Infrastructure Element

9 Topography of the County is characterized by low-lying, flat terrain, karst geology, a thin soil profile and extensive salt and freshwater wetlands along the coastal lowlands. The topography gradually rises in elevation and varies in landscape traveling eastward from the coast. Paralleling US-19 on the east is a nearly level sand terrace with elevation from 10 to 20 feet above mean sea level. East of this terrace a sand ridge is encountered where the land rises as high as 237 feet above mean sea level and 180 feet along the ridge crest. East of the sandhills the land elevations decrease towards Lake Tsala Apopka and the Withlacoochee River. Surficial geology of the County consists of sand with a scattered distribution of clays in the Central Ridge Area and karst geology along both the east and west portions of the County. Due to topographic and geologic features runoff is generally greater in the Coastal, Lakes, and River Areas of the County, rather than the Central Ridge. Stormwater in the Central Ridge permeates through the sand layers, whereas in the lake and coastal areas, stormwater permeability is inhibited by water table and soil characteristics. Soil associations within the County are categorized based on limitations to drainage. These soil groups with limitations on permeability should be considered during the review of proposed impacts to water quality relating to various stormwater management alternatives. Soil types have direct relationships with stormwater management parameters such as: permeability, erosion potential, infiltration, and filtration. These parameters control both the quantity and quality of water, which recharges the aquifer or becomes runoff. The hydrology of the County is characterized by the surface waters of the Withlacoochee River and the Tsala Apopka Plain, the Coastal Rivers, and the high recharge area of the Central Ridge. The hydrologic characteristics of the major surface water features demonstrate that the Withlacoochee River receives a significant portion of its flow outside of Citrus County (Green Swamp and related watersheds) and the coastal rivers are primarily fed by groundwater discharge. A significant portion of rainfall in the County percolates to the Floridan aquifer or a surficial aquifer, providing a regeneration of groundwater necessary for water consumption, protection against increased sinkhole activity, and the maintenance of hydrologic levels in wetlands, springs, and waterbodies. It is important to retain historical aquifer recharge rates in order to maintain aquifer levels. Runoff from storm events can cause significant detriment to water quality and the safety of the residents. Appropriate measures for controlling and treating runoff are necessary for protection of the public health, safety, and welfare

10 3. Development Pressures Land development impacts the natural drainage patterns and function of land areas. Development or urbanization increases the amount of impervious surfaces, thus, increases the amount and rate of stormwater runoff. Rainfall, which contacts impervious surfaces, washes oil, grease, sediments, residuals, and other pollutants into the receiving bodies. Runoff also transports sediments, fertilizers, pesticides, herbicides, and increases the leachate from agricultural, landscaped, residential, and other similar land areas. Stormwater runoff conveys many pollutants including suspended solids, heavy metals, nitrogen, phosphorus, pesticides, herbicides, fertilizers, and organic materials. These pollutants have degrading effects on water quality. The addition of pollutants of this nature reduces dissolved oxygen concentrations, increase eutrophication, increase public health risks, increase siltation, and reduce aesthetic values. Increasing volumes and runoff rates from an urbanizing landscape can lead to the flooding of low-lying areas and areas, which previously had no flooding problems. As development continues, runoff rates and volumes increase. B. Stormwater Drainage Plans and Studies 1. Citrus County: Stormwater Drainage Study Glace and Radcliffe, Inc., completed a stormwater drainage study in July 1981 for Citrus County. This study delineates subbasin boundaries, identified existing control structures, identified wetland and recharge areas, and recommended stormwater management practices. Conclusions from the stormwater drainage study are listed below: Citrus County has many well-defined drainage basins and adequately sized drainage structures. The growth and urbanization, which is occurring in Citrus County, could have deleterious effects on water quality. As growth continues, the County will become more urbanized and the rate of delivery of stormwater in the respective basins and subbasins will increase. The County should take action to protect area water quality and preserve its vital natural resources. The County should implement regulations as required to enhance stormwater management contribution to life and environmental quality. The County should be cognizant that the implementation of both structural and nonstructural alternatives for stormwater management may be 5-127

11 required in the future and that the appropriation of funds to accomplish these stormwater objectives will be necessary. Specific recommendations from the stormwater drainage study are: The County Commission accepted this report as the basis for making future decisions on stormwater management practices and implementing future improvements to the County s primary drainage system. The County proceed with the adoption of stormwater management regulations. The County perform site specific, stormwater management evaluations using this study as a database. The County administer proper land use and water conservation regulations and prohibit development in these flood prone areas where it would be detrimental and not in the best interest of Citrus County. 2. Five Year Plan: Drainage Improvements The Drainage Improvements Plan prepared by the Department of Technical Services in October 1986 provided a prioritized list of improvements through the year These improvements were estimated to cost approximately $582,000 to the year Additional projects are added each year as older projects are completed. A current listing of projects is contained within the Capital Improvements Element. Each project within the drainage improvement plan was evaluated based on seven factors, which include: Residential Units Affected Commercial Units Affected County Roads Affected Frequency of Flooding Length of Time-Standing Water Average Daily Traffic/Affected Roadways Flooding Area (acreage) These factors were inventoried and a score was calculated. The point score was then divided by the estimated cost to rank the project in priority order. These improvements were generally site specific in areas experiencing flooding conditions during various storm events. The Department of Technical Services was responsible for the planning and design of such improvements and the Department of Public Works was responsible for the construction and maintenance of the facilities. In many cases the improvements were remedial and may be of emergency nature. Since the improvements are not the portion of a comprehensive drainage plan for the subdivision or a portion of a stormwater 5-128

12 master plan for a subbasin, the pollutant and filtering functions were not always met. 3. Beverly Hills Stormwater Study and Plan This study was prepared for Citrus County in December The Beverly Hills Development was platted prior to stormwater drainage design requirements in the County. Numerous drainage problems occurred within the subdivision. The County authorized the preparation of this study to develop an overall stormwater master plan for Beverly Hills, Units One through Five. The initial design was intended to comprehensively address and effectively manage stormwater drainage. Based on this study, the County has addressed problem drainage areas in many areas of Beverly Hills. This program is ongoing. 4. Highlands Stormwater Study The Highlands Stormwater Study was commissioned by the County to address drainage problems within a portion of the Inverness Highlands Subdivision. This study covers a land area of approximately 1,110 acres. The study identified drainage patterns and problems. Strategically located properties were acquired through an assessment program and some drainage facilities have been constructed. This project is ongoing and is revisited periodically as development and infill occur. III. NEEDS ASSESSMENT A. Stormwater Drainage Regulation 1. Citrus County Citrus County s stormwater drainage regulations are embodied in the Citrus County Land Development Code and Appendices C.O These regulations contain level of service standards for drainage facilities and specific design standards. The Department of Public Works is responsible for enforcement of this ordinance. Their main role in administering these ordinances lies within the subdivision (plat) review procedures. The construction of a single family residence is conditionally exempt from requirements of this ordinance. The conditional exemption does not include requirements of Section 3, Subsections (4) and (5), which state: 5-129

13 (4) Special Cases Single family dwellings, including duplexes, shall be constructed in such a manner as to prevent flooding from stormwater entering the site from adjacent properties, including roadways. Residential sites within a Master Drainage Area shall provide approved drainage methods, as to prevent direct runoff onto adjacent properties. All other residential sites shall be graded in such a manner as to provide on-site retention of the first one (1) inch of stormwater runoff for the developed area of the lot and to prevent direct runoff onto adjacent properties. (5) All Systems (including Special Cases) Whenever stormwater runoff is designed to enter any body of water, including roadside ditches and swales, special engineering features designed to remove, oils, suspended soils, and other objectionable materials shall be required. To the maximum extent possible, designs shall include methods to retain stormwater in natural recharge areas. The Department of Public Works is responsible for planning engineering and for the construction and maintenance of drainage facilities for the County operated facilities. The Land Development Code contains requirements that drainage facilities and conveyance systems be constructed to meet specific storm duration events. These specific standards are located in Appendix A and B of the Land Development Code. A summary of requirements for stormwater management include: Calculations for runoff shall consider the entire contributory watershed including area outside of the subdivision Natural collection facilities which direct runoff from the subdivision on to adjacent properties must be perpetuated to the extent of protecting the upland owners interest; however, such facilities must not be incorporated into the drainage design for the subdivision The collection of stormwater runoff shall be by positive gravity means without the use of siphons, pumps, or similar devices Calculations shall be based on commonly accepted engineering procedures such as S.C.S, TR-55 or the rational method (Q=CIA). All developers must retain or detain only the additional runoff caused by their development If, prior to development, stormwater flows either from or through the site under review to an adjacent property, that predevelopment peak runoff 5-130

14 rate shall be calculated and, with either detention or retention facilities incorporated in the drainage design, post development drainage shall be performed which demonstrate that the peak runoff rates onto adjacent properties will not be increased during a 25-year, 24-hour storm event (open basin) or a 100-year, 24-hour storm event (closed basin) It shall also be demonstrated that for the same design storm, there will be no increase in backwater onto an upstream property and that any increase in volume of runoff will have been detained and released at a time which will not cause any increased flooding downstream It shall be demonstrated that the design of all site drainage facilities shall not cause flooding of public streets or buildings during a 25-year, 24-hour storm event (open drainage system). 3-year, 24-hour storm event for closed drainage system (curb and gutter) Culverts within an open drainage system shall be designed to discharge a 10-year frequency storm without static head at the entrance and a 25-year frequency storm utilizing available head at the entrance 2. Southwest Florida Water Management District (SWFWMD) The SWFWMD surface water management rules (Chapter 40D-4 and 40D-40, F.A.C.) provide regulations for the construction and operation of any new surface water management system or the alteration of any surface water management system. Exemptions from the surface water management rules included specified agricultural and mining lands, permitted development prior to October 1, 1984, and the construction of single-family residences (refer to Chapters 40D-4 and 40D-40 for specific list of exemptions). B. Capacity and Performance of Facilities The capacity and performance of drainage facilities refers to the capacity of conveyance channels, and the relation to water quantity and quality, respectively. A comprehensive study of drainage facilities was conducted in the Stormwater Drainage Study, (Glace and Radcliffe, Inc., 1981). This study stated that Citrus County has many well defined drainage basins and adequately sized drainage structures. Areas of the County without stormwater drainage facilities or adequately designed facilities are numerous. These areas have a mixture of drainage problems relating to lack of facilities, soils with low infiltration rates, and poor subdivision designs. These areas are found in the Coastal, Lakes, and River and Central Ridge Areas of the County. Existing drainage facilities have not been analyzed for either capacity or performance. In many cases, the post-development peak has not been reached and facilities appear to be designed and constructed over capacity, due to the lack of standing water

15 IV. DRAINGE PLAN A. Level of Service The County s regulations shall utilize the 25-year, 24-hour storm event (open basin) and a 100-year, 24-hour storm event (closed basin) for the construction of drainage facilities and require the water quality treatment of the first one-half inch of runoff. This storm event is utilized as a level of service for predevelopment and postdevelopment stormwater requirements. The SWFWMD was delegated responsibility to regulate stormwater from the DEP in accordance with Chapter 62-25, F.A.C. The SWFWMD utilizes the 100-year, 24-hour storm event in their stormwater design requirements. The County also uses the 100-year, 24-hour storm event and the retention of the first one-half inch of runoff for the drainage level of service for all new subdivisions or planned developments. The SWFWMD requires retention of the first one-half inch up to one and a half inches of runoff depending on the basin type, location, and physical characteristics of the development. Existing regulations and programs, which govern land use and development of natural drainage features, are contained within the LDC. They include regulations that address the protection of natural drainage inclusion of protective measures for natural drainage features. The level of service for drainage plans and facilities for all new subdivision or planned development is as follows: 1. For open basins - the retention of the first one-half inch of runoff or a volume of 50 percent more for discharge into Outstanding Florida Waters (OFW) (water quality/pollution) and the 25-year, 24-hour storm event (water quantity/flooding); 2. For closed basins - the retention of the first one-half inch of runoff or a volume of 50 percent more for discharge into (OFW) (water quality/pollution) and the 100-year, 24-hour storm event (water quantity/flooding). The County regulations require that the first one-half inch of runoff is retained on-site for single-family residences (except when a Master Drainage Plan is in place). The County s adopted level of service has been adjusted to match the SWFWMD water quality and water quantity criteria

16 B. Natural Features and Drainage Natural features and drainage are important to preserve. These features include high recharge areas and natural drainage patterns. Protection of these functions and resources is beneficial in multiple areas: 1) filtering and recharging our potable water supply aquifers, 2) reducing the potential of increased sinkhole activity, 3) maintenance of flows to streams and springs, 4) providing natural filtering prior to discharge into surface waters, and 5) reducing the costs of developing drainage systems in areas where natural features are utilized in conjunction with manmade drainage facilities. Development standards in areas of high recharge are necessary to preserve the functions of such lands. Drainage facilities in recharge areas shall utilize facilities which maintain the volume of historical recharge and provide adequate filtering and water quality treatment to prevent nutrients and contaminants from entering the potable aquifer. In all cases, no drainage is allowed to discharge into sinkholes or direct openings to aquifers providing potable water (refer to the Conservation Element for groundwater protection measures). Where the likelihood of sinkholes exists, all proposed drainage retention and water quality treatment areas should be inspected through geotechnical testing for the presence of cavities and voids beneath the proposed location. Natural drainage patterns are important to preserve, as they are the lands existing drainage facilities. If development of the watershed does not include a comprehensive analysis of such drainage, the result is a basin, which will have potentially expensive and hazardous conditions. C. Stormwater Drainage Plans Currently, there are limited (Homosassa Southfork) stormwater drainage plans for establishing a unified effort to adequately facilitate stormwater drainage, although the County currently is entering into a Memorandum of Understanding (MOU) with the SWFWMD. The MOU will provide for detailed aerial photography and mapping, watershed analysis, watershed development impact modeling, and identification of needed projects, among other things. Many efforts and expenditures are being made to correct drainage problems throughout the County. The development of master drainage plans for subbasins or small groups of subbasins can establish the desired goal for meeting stormwater needs within affected subbasins. These plans can coordinate the individual improvements within a subbasin to meet the overall stormwater drainage needs and requirements

17 D. Regional Stormwater Drainage Plans A regional stormwater drainage plan is proposed for the County Road 491 roadway improvements from W. Laurel Street to south of W. Audubon Park Path. Currently, stormwater management facilities within the county are provided individually by each development, whether it is through a single site or as part of an overall master planned development or a subdivision. These systems, especially the stormwater ponds, typically require a large amount of land to assure that the requirements for collecting and treating the stormwater from any rain event are met. These systems can also be costly to design, permit and construct. Citrus County has a number of commercial sites that have already been developed utilizing the concept of regional drainage. For many of these a regional drainage retention pond accepts the stormwater for all of the projects parcels, especially the out parcels, allowing them to be developed along the valuable highway frontage without the need for their own onsite drainage pond. In addition, regional stormwater management system can be utilized for roadway projects with an adjacent commercial developments. The development of regional stormwater ponds benefits both the County and the development community by reducing the amount of land area required for a stormwater system and releasing a larger portion back to the overall project area for future development

18 V. GOALS, OBJECTIVES, AND POLICIES Goal #9 - To develop a comprehensive stormwater drainage program including design requirements, unified drainage plans, and protection of natural drainage features and functions. Level of Service Objective 9.1 Policy The Land Development Code shall contain requirements for stormwater facility design and Level of Service. The level of service for drainage plans and facilities for all new nonresidential development, subdivision or planned development is as follows: 1. For open basins - the retention of the first one-half inch of runoff or a volume of 50 percent more for discharge into OFW (water quality/pollution) and the 25-year, 24-hour storm event (water quantity/flooding); Stormwater discharges from any site shall conform to the water quality standards used by SWFWMD, DEP and the rules and regulations adopted or implemented by the Citrus County Board of County Commissioners. 2. For closed basins - the retention of the first one-half inch of runoff or a volume of 50 percent more for discharge into OFW (water quality/pollution) and the 100-year, 24-hour storm event (water quantity/flooding). No stormwater runoff shall be allowed to drain directly through any sinkhole or other karst feature. Stormwater discharges from any site shall conform to the water quality standards used by SWFWMD, DEP and the rules and regulations adopted or implemented by the Citrus County Board of County Commissioners. 3. For all spring and spring run basins all stormwater discharges from any site shall conform to water quality standards used by SWFWMD, DEP and the rules and regulations adopted or implemented by the Citrus County Board of County Commissioners. If and when an interlocal agreement is enacted, the agreement will supersede this policy. Policy The County shall ameliorate the future discharge of inadequately treated stormwater runoff into waters and wetlands of the state by requiring the following: 5-135

19 a. Redevelopment projects shall include water quality treatment to the greatest degree possible to not exceed that required for new development. b. All other projects shall ensure that water quality treatment for the first one-half inch of runoff be retained on-site, or in the case of runoff entering any body of water designated an Outstanding Florida Water (OFW), a volume of 50 percent more shall be required. Stormwater discharge shall conform to the standards used by SWFWMD, DEP and the rules and regulations adopted or implemented by the Citrus County Board of County Commissioners. Policy Policy Policy Policy The County shall coordinate with the SWFWMD and FDEP to create a single permitting procedure for addressing stormwater/drainage requirements of new developments. All stormwater management and drainage systems proposed to be constructed in karst sensitive areas, areas with known sinkholes, and areas with shallow depth to limestone bedrock, shall be evaluated for the presence of sinkholes through appropriate geotechnical testing. All proposed Drainage Retention Areas (DRAs) shall be tested for the presence of cavities and voids beneath them. DRAs and other stormwater storage and treatment facilities, but not conveyance facilities, shall not be located over unfilled voids. If there is an existing or historic sinkhole on the proposed development, or indication that a sinkhole may develop in the future, then a detailed geological/geotechnical investigation shall be required. This investigation must be conducted by a certified geologist or professional engineer experienced in hydrogeology and a report submitted to the County for consideration. The geologic investigation shall be comprehensive enough that recommendations for site planning, engineering design and construction techniques may be made. The County shall approve or deny development proposals based upon the scale of the development and the hazards revealed within the investigation. No stormwater structure or facility, other than stormwater swales, shall be located over or adjacent to an existing sinkhole unless it is determined by a certified geologist or professional engineer experienced in hydrogeology that the area is safe and that there is no subsurface connection that may cause contamination or damage to the groundwater

20 Objective 9.2 Policy Citrus County will establish a program to ensure that drainage facilities meet existing and projected demand throughout the planning period, maximize the use of existing facilities, and discourage urban sprawl by using drainage levels of service and requiring development to retain stormwater on site and connect to existing drainage facilities. All development is required to connect to existing facilities, meet drainage levels of service, and retain stormwater on site. Natural Features and Drainage High Recharge Objective 9.3 Policy Policy Policy Policy The development of drainage facilities in areas of high recharge shall incorporate pollutant and filter functions into site drainage plans. Basins, swales, and culverts shall be designed to protect groundwater and surface water quality and quantity in all new developments. The Land Development Code shall contain minimum standards for recharge of stormwater in areas of high recharge. Postdevelopment recharge volumes and water quality shall equal or improve historical pre-development conditions as provided by the standards used by the SWFWMD, DEP and the rules and regulations adopted or implemented by the Citrus County Board of County Commissioners. The County is exempt from pollutant and filtering functions in cases of emergency actions. The County will adopt and require stormwater Best Management Practices (BMPs) for all stormwater management systems located in all areas of the County. Natural Drainage Objective 9.4 Policy Natural drainage features shall be protected and included in Master Stormwater Drainage Plans. Natural drainage features shall be analyzed in all development plans and measures to protect the natural drainage features will be incorporated into the County Land Development Code

21 Policy A public or private stormwater utility, MSTU or other applicable mechanism shall be adopted by 2007 to provide the financial basis for stormwater master planning and retrofitting projects. Stormwater Drainage Plans Objective 9.5 Policy The County shall implement stormwater master plans, emphasizing facility capacity of drainage systems as the basis for a watershed based approach to stormwater management. The County shall utilize the report to Plan Oversight Committee from the Stormwater Level of Service Convention Committee in development of the master plans. The County will coordinate and work with the SWFWMD to develop comprehensive watershed master plans through the mechanism of a Memorandum of Understanding (MOU). The MOU will assist with the development and implementation of a variety of flood prevention and control projects, water quality projects, detailed flood plain analysis, and watershed modeling. Existing Deficiencies and Coordination Objective 9.6 Policy Policy Policy The County shall correct existing drainage deficiencies identified in the Five-year Drainage Improvements Plan, prevent future discharge of inadequately treated runoff, and implement a program to identify, prioritize, and correct drainage deficiencies. The program to identify, prioritize, and correct drainage deficiencies shall be coordinated with the preparation of Master Stormwater Drainage Plans and shall include measures to correct system capacity, pollution loading, and recharge functions of drainage systems. The program to implement the correction of existing facilities shall follow the schedule in the Capital Improvements Element. Proposed capital improvement projects will be evaluated and ranked according to the following level guidelines: Level One - whether the project is needed to protect public health and safety, to fulfill the County s legal commitment to provide facilities and services, to preserve or achieve full use of existing facilities, or if permitted capacity has been reached

22 Level Two - whether the project increases efficiency of use of existing facilitates, prevents or reduces future improvement costs, provides service to developed areas lacking full service, or promotes infill development. Level Three - where the project represents a logical extension of facilities and services within a designated service area. Policy The County will continue a program to coordinate the expansion or extension of drainage facilities with other local governments to meet future needs