The Encinitas Ranch Specific Plan proposes a comprehensive system of water detention basins and conveyance systems which are intended to improve the quality of water runoff prior to being discharged off-site, to provide adequate measures against exceeding the capacities of existing storm drain facilities, and to ensure that urban runoff does not flow over agricultural land. The drainage concepts for Encinitas Ranch call for the development of an integrated system of detention ponds, grassed swales, and catchment basins which filter storm water runoff before discharging it into the City's storm drainage system (see Figure 23, Drainage Plan). Urban runoff in the Green Valley area will be filtered before flowing into Encinitas Creek.
Drainage from the Encinitas Ranch Specific Plan Area will not adversely impact downstream drainage facilities. The actual sizing of open space areas to detain storm water runoff will be determined by a hydrologic analysis acceptable to the City engineer. The results of this hydrologic analysis may reduce the size of developable areas adjacent to the drainage open space.
The primary goal of this storm water management plan is to prevent flooding and protect property by providing safe, effective site drainage. This plan has been developed to do so, while also addressing the potential impacts that the proposed land uses may have on the environmental quality of the water.
To mitigate these potential impacts, this plan relies on a variety of facilities, each specifically located within the system to provide incremental removal of urban pollutants. The applicant shall comply with the requirements of the National Pollutant Discharge Elimination System (NPDES) permit. The applicant shall provide Best Management Practices to control discharges of pollutants into waters of the United States to the maximum extent practical. Plans for such improvements shall be approved by the City Engineer prior to, or concurrent with, approval of the final map or issuance of the grading or building permit, whichever occurs first, in the affected area.
The potential for the degradation of water quality at storm water runoff discharge points is largely determined by land use. Moreover, the characteristics of pollutants contributed by different land uses determine different facilities that are best suited to specific pollutant removal. To best address water quality degradation that may be associated with specific land uses, this storm water management plan segregates runoff based on land use. By doing so, different facilities that target particular pollutants can be most efficiently located in the system.
Distinctions have been made between three land use types: urbanized development, natural and landscaped open space/golf course, and agricultural land. The urbanized areas with increased impervious cover (e.g., streets, parking lots, rooftops, etc.) will contribute the highest increase in storm runoff compared to predevelopment conditions. The increase in runoff rate can be mitigated by providing permanent ponds that have sufficient added capacity to detain or hold back additional storm water, while only releasing water at pre-development rates or some other rate determined to be appropriate for the downstream system. Pollutants that may potentially be introduced are primarily associated with streets and parking areas that collect oil-related and other automotive by-products on their hard surfaces in storm water runoff. Urban landscape areas have the potential for contributing nutrients and pesticides to runoff from fertilizers, soil amendments and spraying. Similarly, landscaped open space and the golf course areas are potential sources for the introduction of increased nutrients and pesticides in storm water. Agricultural areas, due to their cultivated state, are known to be potential sources for suspended silts and sediment loads in storm water. Agricultural fertilizers and pesticides also present the potential for additional nutrient loads and pesticide-related tainting of storm runoff.
The Encinitas Ranch project contributes storm runoff to three watersheds: the Encinitas Creek Watershed which discharges into Batiquitos Lagoon to the north; the Encinitas Boulevard Watershed, discharging into the Pacific Ocean; and the Saxony Road Watershed which discharges into Batiquitos Lagoon.
5.4.1 MAINTENANCE OF DRAINAGE FACILITIES
The ongoing maintenance of facilities in the system and the surface areas that contribute runoff will be essential to the storm water system's success. In discussions between the City, project proponent, and the State Department of Fish and Game, the State has indicated interest in a maintenance program for desiltation basins on a three-year rotation basis. The project developer/applicant and/or the City shall be responsible for the maintenance of drainage facilities and parking area surfaces. Any maintenance program for desiltation basins must be approved by the City Engineer and the State Department of Fish and Game.
In urban areas, regular street and parking lot sweeping are important to prevent unnecessary loading of the system with dust and debris. Landscape and open space areas, including the golf course shall institute integrated maintenance and pest control policies to avoid unnecessary application of fertilizers and pesticides. Soil conservation practices to minimize soil erosion and silt loading in runoff will contribute to the efficiency of the system.
Since the facilities of the system are intended to remove silt and other contaminants from storm water, they will require periodic cleaning to remove accumulations that could eventually render them ineffective. Vegetated filter strips, sediment basins and detention ponds will require periodic dredging, regrading, and replanting as the sediments that they trap eventually reduce flow and storage capacities. Water quality inlets will also require periodic removal of the accumulated petroleum-based products that they capture. The final design of these facilities will need to consider these requirements, providing reasonable maintenance access. The property owner, or the City of Encinitas Landscape and Lighting District if the facilities are accepted by the City, shall be responsible for the maintenance of drainage facilities.
With the storm water management system relying on overland flow courses, its appearance must be carefully integrated into the overall landscape of the Encinitas Ranch Specific Plan Area. The coarse grasses and riparian plants that are best suited to nutrient uptake and variable wet conditions will offer a natural appearance that is desired as part of the landscape identity for the golf course. The color, texture and variety of form, contrasted with the greens of the golf course, is intended to create a rich landscape tapestry.
5.4.2 STORM DRAIN FACILITIES
In the past, the major concern when designing storm drainage systems was flooding. Today, with the growth of urban areas and concerns over the protection of wetlands and habitat areas, the need for the removal of urban pollutants from urban drainage has increased. Storm drainage facilities required to prevent flooding will be constructed concurrent with development. Currently, there are no major storm drainage facilities located within the Specific Plan Area.
The primary components of the storm drainage system are the subsurface pipes, overland drainage swales and detention basins. As for storm water management, the basins serve three purposes: flood prevention, detention and desiltation, and removal of urban pollutants. Detention requirements have been imposed to regulate the volumes of water being discharged into the downstream wetland areas of the watershed.
The desiltation and removal of urban pollutants will also be factors of the storm drainage systems. Water quality control guidelines have recently been adopted by the State Water Quality Control Board and Environmental Protection Agency. These guidelines will be implemented in the proposed system. The applicant shall comply with the requirements of the National Pollutant Discharge Elimination System (NPDES) permit. The applicant shall provide Best Management Practices to control discharges of pollutants to the maximum extent practical into waters of the United States. Plans for such improvements shall be approved by the City Engineer prior to, or concurrent with, approval of the final map or issuance of the grading or building permit, whichever occurs first, in the affected area.
Paragraph amended 3/18/98 (Reso. 98-17)
