San Luis Obispo County Municipal Code Ch. 19.11 Stormwater Management

The requirements in this chapter are intended to reduce pollutant discharges to the maximum extent practicable and to prevent stormwater discharges from causing or contributing to a violation of receiving water quality standards. These requirements also incorporate the post-construction stormwater management requirements (PRC's) for development projects in the county. The PCRs mandate that development projects use low impact development (LID) to detain, retain, and treat runoff. LID incorporates and conserves on-site natural features, together with constructed hydrologic controls to more closely mimic pre-development hydrology and watershed process. Collectively, these requirements emphasize protecting and, where degraded, restoring key watershed processes to create and sustain linkages between hydrology, channel geomorphology, and biological health necessary for healthy watersheds. Maintenance and restoration of watershed processes impacted by stormwater management is necessary to protect water quality and the beneficial uses of surface and groundwater.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

(a) Where Applicable. The requirements of this section are applicable only where a project will drain to those areas designated by the State Water Resources Control Board (SWRCB) as traditional or non-traditional municipal separate storm sewer systems (MS4s). MS4s consist of areas designated as "urbanized" in the most recent decennial US Census, as well as other outlying areas with a population of ten thousand or more or a population density greater than one thousand people per square mile. The current San Luis Obispo County MS4 Area can be found on the department and planning and building website.

Designated MS4 areas include, but are not limited to, the following:

(1) All areas within an urban reserve line (URL), as designated in the county general plan.

(2) All areas within the following village reserve lines (VRLs), as designated in the county general plan.

(3) Any other areas identified as being subject to the stormwater standards, as indicated in Attachment A of the Central Coast Post-Construction Stormwater Requirements MS4 Phase II Permit.

(b) Limited Exemption. Projects which have received approval of a zoning clearance, land use permit, or land division prior to March 6, 2014 are exempt from the standards of this section, unless such approval has expired.

(c) Regulated Projects. Regulated projects include all new development or redevelopment projects, both discretionary and ministerial, that create and/or replace at least two thousand five hundred square feet of impervious surface (collectively over the entire project site) as defined by the central coast regional water quality control board under Order R3-2013-0032.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

Prior to acceptance of an application for a construction permit, grading permit, land use permit, or subdivision application associated with a regulated project, as defined in Section 19.11.030(c), of the Land Use Ordinance, the applicant shall submit a stormwater control plan that demonstrates compliance with the post-construction requirements for the Central Coast region, adopted by the central coast regional water quality control board under Order R3-2013-0032.

(1) Site Design Checklist. The SWCP for all projects subject to this section shall demonstrate that the following design strategies have been pursued in order to reduce runoff:

a. Limit disturbance of creeks and natural drainage features.

b. Minimize compaction of highly permeable soils.

c. Limit clearing and grading of native vegetation at the site to the minimum area needed to build the project, allow access, and provide fire protection.

d. Minimize impervious surfaces by concentrating improvements on the least-sensitive portions of the site, while leaving the remaining land in natural, undisturbed state.

e. Implement at least one of the following strategies:

1. Direct roof runoff into cisterns, rain barrels, underground storage, or a similar mechanism for reuse.

2. Direct roof runoff onto vegetated areas safely away from building foundations and footings, consistent with the California Building Code.

3. Direct roof runoff from sidewalks, walkways, and/or patios onto vegetated areas safely away from building foundations and footings, consistent with the California Building Code.

4. Direct runoff from driveways and/or uncovered parking lots onto vegetated areas safely away from building foundations and footings, consistent with the California Building Code and Title 19 of the County Code.

5. Construct bike lanes, driveways, uncovered parking lots, sidewalks, walkways, and patios with permeable surfaces.

(2) Plan Documents and Details. The SWCP for all regulated projects, as defined in Section 19.11.030(3), of the Land Use Ordinance, shall provide the following documents and details:

a. Project name, application/permit number, location, and assessor's parcel number.

b. Name of the applicant.

c. Identification of which project phase, if the project is being constructed in phases.

d. Project type (e.g. commercial, industrial, multi-unit residential, mixed use, public) and description.

e. Total project site area.

f. Total new impervious surface area, total replaced impervious surface area, total new pervious area, and calculation of net impervious area.

g. Identification and location of all structural and non-structural control measures (SCM's) proposed as part of the stormwater conveyance system.

h. A certification from a qualified professional (e.g. a registered civil engineer, licensed architect, or other individual deemed to be qualified by the director) that appropriate LID design have been incorporated into the plan to the maximum extent practicable to meet the County of San Luis Obispo Post Construction Requirements Handbook.

i. A preliminary drainage plan, consistent with of Section 22.52.110 of the Land Use Ordinance and Section 23.05.036 of the Coastal Zone Land Use Ordinance.

j. A preliminary erosion and sediment control plan, consistent with Section 22.52.120 of the Land Use Ordinance and Section 23.05.040 of the Coastal Zone Land Use Ordinance. The plan shall conform to the California Construction General Permit Order 2009-0009-DWQ as applicable.

k. If needed to demonstrate compliance with the stormwater quality standards in Section 19.11.050 of Land Use Ordinance, drainage calculations prepared by a registered civil engineer.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

Stormwater control plans shall be reviewed for consistency with the post-construction stormwater control standards identified in Central Coast Regional Water Quality Control Board Order R3-2013-0032 and County of San Luis Obispo Post Construction Requirements Handbook. Performance standards contained in this order include, but are not limited to, the following:

(1) Site Design Measures. (Performance Requirement 1.) All Regulated Projects, as defined in Section 19.11.030.c, are subject to this standard. All projects resulting in at least two thousand five hundred square feet of net impervious area.

(2) Water Quality Treatment. (Performance Requirement 2.) All projects resulting in at least five thousand square feet of net impervious area, other than single-family residences, shall comply with this standard. Single-family residence projects shall comply with this standard if they involve at least fifteen thousand square feet of net impervious area. A single-family residence project is defined for the purposes of Chapter 19.11, as the building of one single new house or addition and/or replacement of net impervious surface associate with one single existing house, which is not part of a larger plan of development.

(3) Runoff Retention. (Performance Requirement 3.) All projects resulting in at least fifteen thousand square feet of net impervious area shall comply with this standard.

(4) Peak Management. (Performance Requirement 4.) All projects resulting in at least twenty two thousand five hundred square feet of net impervious area shall comply with this standard.

(5) Special Circumstances. (Performance Requirement 5.) Projects subject to the performance standards identified in Subsections (3) and (4), but discharging to watercourses with special circumstances.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

The stormwater control plan must address source control of any applicable pollutants associated with the proposed use that could enter the stormwater conveyance system. The following source control best management practices (BMPs) are required for projects that propose any of the following features:

(1) Outdoor Material Storage. Where proposed projects include outdoor storage areas for storage of materials that may contribute pollutants of concern to the stormwater conveyance system, the following structural or treatment BMPs are required:

a. Materials with the potential to contaminate stormwater must be:

1. Placed in an enclosure such as, but not limited to, a cabinet, shed, or similar structure that prevents contact with runoff or spillage to the stormwater system; or

2. Protected by secondary containment structures, such as berms, dikes, or curbs.

b. The material storage area shall be sufficiently impervious to contain leaks and spills.

c. Where secondary containment is necessary, storage areas shall have a roof or awning to minimize collection of stormwater, or another approved method.

d. For storage areas involving the storage of motor vehicles, site design shall comply with Section 19.11.030.

(2) Loading and Unloading Dock Areas. To minimize the potential for material spills to be transported to the stormwater conveyance system, the following is required:

a. Loading dock areas shall be covered, or drainage shall be designed to minimize run-on or runoff of stormwater; and

b. Connections to storm drains from depressed loading docks (truck wells) are prohibited. An approved structural source control measure and/or treatment control measure shall be used to prevent stormwater pollution.

(3) Repair and Maintenance Bays. To minimize the potential for oil/grease, car battery acid, coolant, and gasoline to be transported to the stormwater conveyance system, design plans for repair/maintenance bays shall include the following:

a. Repair/maintenance bays shall be indoors or designed in such a way that does not allow stormwater run-on or runoff; and

b. The drainage system for the repair/maintenance bays shall be designed to capture all wash water, leaks, and spills. Drains shall be connected to a sump for collection and disposal. Direct connection to the storm drain system is prohibited. If required by the regional water quality control board, an industrial waste discharge permit shall be obtained.

(4) Vehicle and Equipment Wash Areas. To minimize the potential for metals, oil/grease, solvents, phosphates, and suspended solids to be transported to the stormwater conveyance system, the area for washing/steam cleaning of vehicles and equipment shall be designed to the following specifications:

a. Self-contained and/or covered, equipped with a clarifier, or other pre-treatment facility; and

b. Properly connected to a sanitary sewer or other appropriately permitted disposal facility.

(5) Restaurants. An area for washing/steam cleaning of equipment and accessories shall be included on the plans. To minimize the potential for metals, oil and grease, solvents, phosphates, and suspended solids to be transported to the stormwater conveyance system, the area for washing/steam cleaning of equipment and accessories shall be designed to the following specifications:

a. Self-contained, equipped with a grease trap, and properly connected to the sanitary sewer; and

b. If the wash area is to be located outdoors, it must be covered, paved, have secondary containment, and be connected to the sanitary sewer or other appropriately permitted disposal facility.

(6) Fueling Areas. To minimize the potential for oil/grease, solvents, car battery acid, coolant, and gasoline to be transported to the stormwater conveyance system, the project plans shall include all of the following BMPs:

a. The fuel dispensing area shall be covered with an overhanging roof structure or canopy. Provide containment limits on the plans (i.e. grade break, berm, etc.). The canopy's minimum dimensions shall be equal to or greater than the containment limits. The canopy shall not drain onto the fuel dispensing area, and the canopy downspouts shall be routed to prevent drainage across the fueling area.

b. The fuel dispensing area must be paved with Portland cement concrete (or equivalent smooth impervious surface), and the use of asphalt concrete shall be prohibited.

c. The fuel dispensing area must have a two percent minimum slope to prevent ponding, and must be separated from the rest of the site by a grade break that prevents run-on of stormwater to the maximum extent practicable.

d. At a minimum, the concrete fuel dispensing area must extend 6.5 feet from the corner of each fuel dispenser, or the length at which the hose and nozzle assembly may be operated plus one foot, whichever is less.

(7) Parking Lots. Parking lots with an area of five thousand square feet or more, or twenty-five parking spaces or more, shall minimize potential for oil, grease, and other water insoluble hydrocarbons from vehicle drippings and leaks from entering the stormwater conveyance system. Plans shall provide for the following:

a. Treat to remove oil and petroleum hydrocarbons; and

b. Ensure adequate operation and maintenance of treatment systems, particularly sludge and oil removal and system fouling and plugging prevention control. At a minimum, this shall include a maintenance program which is funded and carried out by the property owner.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

Long-term maintenance of structural control measures installed to meet applicable performance requirements shall be documented through the establishment of a condition compliance monitoring (CCM) permit which includes recordation of an authorized written operations and maintenance agreement and/or covenants, conditions, and restriction (CC&Rs), unless the project does not include structural stormwater control measures. This agreement shall be recorded prior to or concurrent with issuance of building or grading an occupancy permit. However, final SCM's will be verified to match approved design, as after issuance or as-built grading permit may be required and would result in revision of O&A agreement or CC&R's prior to issuance of occupancy. In order to verify that structural control measures will be continually operated and maintained, the agreement shall do the following:

(1) Designate and Accept Responsibility. Identify the party who is responsible for long-term operation and maintenance of stormwater control measures. The responsible party will provide a signed statement accepting responsibility until such responsibility is legally transferred to another entity.

(2) Address Transfer of Responsibility. Address how structural control measures will be maintained once property has been transferred to private landowners, a homeowner's association, or a public entity.

(3) Reference Materials. Reference materials shall include:

a. A site map identifying all structural control measures requiring maintenance.

b. Legal parcel description of the parcel(s) where stormwater SCM's will be installed.

c. Short and long-term maintenance requirements for each stormwater control measure.

d. Procedures for conducting necessary maintenance including recommended frequency of maintenance, anticipated costs, and manufactures manuals or specifications.

Reference materials shall be required to accompany the first deed transfer. The transfer of this information shall also be required with any subsequent sale of the property.

(4) Address Operations and Maintenance Monitoring/Reporting. Address the requirement that the responsible party will provide an annual monitoring report to the county verifying that structural control measures have been inspected, operated, and maintained as required. This annual monitoring report is to be submitted by June 15 of each year. Failure to provide the required annual inspection reports may be referred to code enforcement.

(5) Failure to Clean and Maintain Stormwater System. Failure to maintain, monitor, inspect, clean, repair, or document and report as required shall constitute a public nuisance. The county may remedy such public nuisance through any of the applicable procedures as set forth in Section 22.74.150 of the Land Use Ordinance for nuisance abatement process and/or may pursue any other legal or equitable remedies to abate such public nuisance.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)

The alternative compliance process specified in Central Coast Regional Water Quality Control Board Order R3-2013-0032 may be followed at the discretion of the Director. Such a process may be available in the following circumstances:

(1) Special Circumstances. Where the project discharges to receiving waters with special circumstances (e.g. highly altered channels, intermediate flow control facilities, and historic lakes and wetlands). In these cases, projects may follow the performance standard identified in Section 19.11.050(5), rather than the performance standards in Section 19.11.050(3) and (4) of the Land Use Ordinance.

(2) Technical Infeasibility. Where technical infeasibility limits or prevents the use of structural control measures.

(3) Approved Watershed or Regional Plan. Where the project falls under a watershed or regional plan that has received approval from the executive director of the Central Coast Regional Water Quality Control Board.

(4) Approved Urban Sustainability Area. Urban infill redevelopment projects located within an urban sustainability area that has been approved by the executive director of the Central Coast Regional Water Quality Control Board.

(5) Other Circumstances. In other circumstances as approved by the executive director of the Central Coast Regional Water Quality Control Board.

(Ord. No. 3343, § 1, 12-6-16; Ord. No. 3400, § 1, 11-19-19)