14-13
STORMWATER AND URBAN RUNOFF POLLUTION AND CONVEYANCE CONTROLS

14-13.1 Purpose And Intent:

a.    The purpose of this chapter is to ensure the future health, safety and general welfare of the citizens of the city and the water quality of the receiving waters of the county of Los Angeles and surrounding coastal areas by:

1.    Reducing pollutants in stormwater discharges to the maximum extent practicable;

2.    Regulating illicit connections and illicit discharges and reducing the level of contamination of stormwater and urban runoff in the municipal stormwater system; and

3.    Regulating non-stormwater discharges to the municipal stormwater system.

b.    The intent of this chapter is to protect and enhance the quality of watercourses, water bodies, and wetlands within the city in a manner consistent with the federal Clean Water Act, the California Porter-Cologne Water Quality Control Act and the municipal NPDES permit.

c.    This chapter is also intended to provide the city with the legal authority necessary to control discharges to and from those portions of the municipal stormwater system over which it has jurisdiction as required by the municipal NPDES permit, and fully and timely comply with the terms of the municipal NPDES permit while the watershed management program is being developed by the permittees under the municipal NPDES permit, and in contemplation of the subsequent amendment of this chapter or adoption by the city of additional provisions of this chapter to implement the subsequently adopted watershed management program, or other programs developed under the municipal NPDES permit.

d.    This chapter also sets forth requirements for the construction and operation of certain commercial development, new development and redevelopment and other projects (as further defined herein) which are intended to ensure compliance with the stormwater mitigation measures prescribed in the current MS4 permit. This chapter authorizes the director to define and adopt applicable best management practices and other stormwater pollution control measures, as provided herein, to carry out all inspections including entering entities discharging to the MS4, conduct surveillance, conduct monitoring, cite infractions and to impose fines pursuant to this chapter. Except as otherwise provided herein, the director shall administer, implement and enforce the provisions of this section.

e.    The city council shall approve and enter into interagency agreements as deemed necessary by the city council to control the contribution of pollutants of the shared MS4. (Ord. #1500, §1; Ord. #1671, §1)

14-13.2 Definitions:

Except as specifically provided herein, any term used in this chapter shall be defined as that term is defined in the municipal NPDES permit, or if it is not specifically defined in the municipal NPDES permit, then as such term is defined in the federal Clean Water Act, as amended, or the regulations promulgated thereunder. If the definition of any term contained in this section conflicts with the definition of the same term in the municipal NPDES permit, then the definition contained in the municipal NPDES permit shall govern. The following words and phrases shall have the following meanings when used in this chapter:

Area susceptible to runoff means any surface directly exposed to precipitation or in the path of runoff caused by precipitation, which path leads off the parcel on which the surface is located.

Automotive service facilities means a facility that is categorized in any one of the following Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS) codes. For inspection purposes, permittees need not inspect facilities with SIC codes 5013, 5014, 5511, 5541, 7532 through 7534, and 7536 through 7539; provided, that these facilities have no outside activities or materials that may be exposed to stormwater.

Best management practices (BMP) means practices or physical devices or systems designed to prevent or reduce pollutant loading from stormwater or non-stormwater discharges to receiving waters, or designed to reduce the volume of stormwater or non-stormwater discharged to the receiving water. Examples of BMPs may include public education and outreach, proper planning of development projects, proper cleaning of catch basin inlets, and proper sludge- or waste-handling and disposal, among others.

Biofiltration means an LID BMP that reduces stormwater pollutant discharges by intercepting rainfall on vegetative canopy, and through incidental infiltration and/or evapotranspiration, and filtration. Incidental infiltration is an important factor in achieving the required pollutant load reduction. Therefore, the term biofiltration as used in this chapter is defined to include only systems designed to facilitate incidental infiltration or achieve the equivalent pollutant reduction as biofiltration BMPs with an underdrain (subject to approval by the Regional Board’s Executive Officer). Biofiltration BMPs include bioretention systems with an underdrain and bioswales.

Bioretention means an LID BMP that reduces stormwater runoff by intercepting rainfall on vegetative canopy, and through evapotranspiration and infiltration. The bioretention system typically includes a minimum two-foot (2') top layer of a specified soil and compost mixture underlain by a gravel-filled temporary storage pit dug into the in situ soil. As defined in this subsection 14-13.2, a bioretention BMP may be designed with an overflow drain, but may not include an underdrain. When a bioretention BMP is designed or constructed with an underdrain, it is regulated by the municipal NPDES permit as biofiltration.

Bioswale means an LID BMP consisting of a shallow channel lined with grass or other dense, low-growing vegetation. Bioswales are designed to collect stormwater runoff and to achieve a uniform sheet flow through the dense vegetation for a period of several minutes.

City means the city of Lynwood, California.

Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted in 1972, by Public Law 92-500, and amended by the Water Quality Act of 1987. The Clean Water Act prohibits the discharge of pollutants to waters of the United States unless the discharge is in accordance with an NPDES permit.

Commercial development means any development on private land that is not heavy industrial or residential. The category includes, but is not limited to: hospitals, laboratories and other medical facilities, educational institutions, recreational facilities, plant nurseries, car wash facilities, mini-malls and other business complexes, shopping malls, hotels, office buildings, public warehouses and other light industrial complexes.

Commercial malls means any development on private land comprised of one or more buildings forming a complex of stores which sells various merchandise, with interconnecting walkways enabling visitors to easily walk from store to store, along with parking area(s). A commercial mall includes, but is not limited to: mini-malls, strip malls, other retail complexes, and enclosed shopping malls or shopping centers.

Construction means any construction or demolition activity, clearing, grading, grubbing, or excavation or any other activity that results in land disturbance. Construction does not include emergency construction activities required to immediately protect public health and safety or routine maintenance activities required to maintain the integrity of structures by performing minor repair and restoration work, maintain the original line and grade, hydraulic capacity, or original purposes of the facility. See “Routine maintenance” definition for further explanation. Where clearing, grading or excavating of underlying soil takes place during a repaving operation, state general construction permit coverage by the state of California general permit for stormwater discharges associated with industrial activities or for stormwater discharges associated with construction activities is required if more than one acre is disturbed or the activities are part of a larger plan.

Control means to minimize, reduce, eliminate, or prohibit, by technological, legal, contractual or other means, the discharge of pollutants from an activity or activities.

Development means any construction, rehabilitation, redevelopment or reconstruction of any public or private residential project (whether single-family, multi-unit or planned unit development); industrial, commercial, retail and other nonresidential projects, including public agency projects; or mass grading for future construction. It does not include routine maintenance to maintain original line and grade, hydraulic capacity, or original purpose of facility, nor does it include emergency construction activities required to immediately protect public health and safety.

Directly adjacent means situated within two hundred feet (200') of the contiguous zone required for the continued maintenance, function, and structural stability of the environmentally sensitive area.

Director means the city’s director of public works or his or her designee.

Discharge means, when used without qualification, the discharge of a pollutant.

Discharge of a pollutant means any addition of any pollutant or combination of pollutants to waters of the United States from any point source, or any addition of any pollutant or combination of pollutants to the waters of the contiguous zone or the ocean from any point source other than a vessel or other floating craft which is being used as a means of transportation. The term discharge includes additions of pollutants into waters of the United States from surface runoff which is collected or channeled by a state, municipality, or other person which does not lead to treatment works; and discharges through pipes, sewers, or other conveyances, leading into privately owned treatment works.

Discharging directly means outflow from a drainage conveyance system that is composed entirely or predominantly of flows from the subject, property, development, subdivision, or industrial facility, and not commingled with the flows from adjacent lands.

Discretionary project is defined in the same manner as Section 15357 of the Guidelines for Implementation of the California Environmental Quality Act contained in Title 14 of the California Code of Regulations, as amended, and means a project which requires the exercise of judgment or deliberation when the city decides to approve or disapprove a particular activity, as distinguished from situations where the city merely has to determine whether there has been conformity with applicable statutes, ordinances or regulations.

Disturbed area means an area that is altered as a result of clearing, grading, and/or excavation.

Environmentally sensitive area (ESA) means an area in which plant or animal life or their habitats are either rare or especially valuable because of their special nature or role in an ecosystem and which would be easily disturbed or degraded by human activities and developments (California Public Resources Code Section 30107.5). Areas subject to stormwater mitigation requirements are areas designated as significant ecological areas by the county of Los Angeles (Los Angeles County Significant Areas Study, Los Angeles County Department of Regional Planning (1976) and amendments); an area designated as a significant natural area by the California Department of Fish and Games Significant Natural Areas Program, provided that area has been field verified by the Department of Fish and Game; an area listed in the Basin Plan as supporting the rare, threatened, or endangered species (RARE) beneficial use; and an area identified by the city as environmentally sensitive.

Flow-through treatment BMPs means modular, vault type “high flow mistreatment” devices contained within an impervious vault with an underdrain or designed with an impervious liner and an underdrain.

Full capture system means any single device or series of devices, certified by the Executive Officer, that traps all particles retained by a five-millimeter (5 mm) mesh screen and has a design treatment capacity of not less than the peak flow rate Q resulting from a one-year, one-hour storm in the sub-drainage area.

Good housekeeping practices means common practices related to the storage, use or cleanup of materials, performed in a manner that minimizes the discharge of pollutants. Examples include, but are not limited to, purchasing only the quantity of materials to be used at a given time, use of alternative and less environmentally harmful products, cleaning up spills and leaks, and storing materials in a manner that will contain any leaks or spills.

General construction activities stormwater permit (GCASP) means the general NPDES permit adopted by the state board which authorizes the discharge of stormwater from construction activities under certain conditions.

General industrial activities stormwater permit (GIASP) means the general NPDES permit adopted by the state board which authorizes the discharge of stormwater from certain industrial activities under certain conditions.

Green roof means an LID BMP using planter boxes and vegetation to intercept rainfall on the roof surface. Rainfall is intercepted by vegetation leaves and through evapotranspiration. Green roofs may be designed as either a bioretention BMP or as a biofiltration BMP. To receive credit as a bioretention BMP, the green roof system planting medium shall be of sufficient depth to provide capacity within the pore space volume to contain the design storm depth and may not be designed or constructed with an underdrain.

Hillside means property located in an area with known erosive soil conditions, where the development contemplates grading on any natural slope that is twenty-five percent (25%) or greater and where grading contemplates cut or fill slopes.

Illicit connection means any human-made conveyance that is connected to the storm drain system without a permit, excluding gutters, roof-drains and other similar connections. Examples include channels, pipelines, conduits, inlets or outlets that are connected directly to the storm drain system.

Illicit discharge means any discharge to the storm drain system that is prohibited under local, state or federal statutes, ordinances, codes or regulations. This includes all non-stormwater discharges except discharges pursuant to a separate NPDES permit and discharges that are exempted or conditionally exempted in accordance with Part III of the municipal NPDES permit.

Industrial/commercial facility means any facility involved and/or used in the production, manufacture, storage, transportation, distribution, exchange or sale of goods and/or commodities, and any facility involved and/or used in providing professional and nonprofessional services. This category of facilities includes, but is not limited to, any facility defined by either the Standard Industrial Classifications (SIC) or the North American Industry Classification System (NAICS). Facility ownership (federal, state, municipal, private) and profit motive of the facility are not factors in this definition.

Industrial park means land development that is set aside for industrial development. Industrial parks are usually located close to transport facilities, especially where more than one transport modalities coincide: highways, railroads, airports, and navigable rivers. It includes office parks, which have offices and light industry.

Infiltration BMP means an LID BMP that reduces stormwater runoff by capturing and infiltrating the runoff into in situ soils or amended on-site soils. Examples of infiltration BMPs include infiltration basins, dry wells, and pervious pavement.

Infiltration means the downward entry of water into the surface of the soil.

Low impact development (LID) consists of building and landscape features designed to retain or filter stormwater runoff.

Material means any substance including, but not limited to: garbage and debris; lawn clippings, leaves, and other vegetation; biological and fecal waste; sediment and sludge; oil and grease; gasoline; paints, solvents, cleaners, and any fluid or solid containing chemicals.

Municipal NPDES permit means the Waste Discharge Requirements for Municipal Storm Water and Urban Runoff Discharges within the County of Los Angeles, and the Incorporated Cities Therein, Except the City of Long Beach (Order No. R4-2012-0175), NPDES Permit No. CAS00401, issued by the California Regional Water Quality Control Board, Los Angeles Region, and any successor permit to that permit.

Municipal separate storm sewer system (MS4) means a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains):

1.    Owned or operated by a state, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to state law) having jurisdiction over disposal of sewage, industrial wastes, stormwater, or other wastes, including special districts under state law such as a sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or a designated and approved management agency under Section 208 of the CWA that discharges to waters of the United States;

2.    Designed or used for collecting or conveying stormwater;

3.    Which is not a combined sewer; and

4.    Which is not part of a publicly owned treatment works (POTW) as defined at 40 CFR 122.2.

New development means land disturbing activities; structural development, including construction or installation of a building or structure, creation of impervious surfaces; and land subdivision.

Non-stormwater discharge means any discharge to a municipal stormwater system that is not composed entirely of stormwater.

NPDES permit means any waste discharge requirements issued by the Regional Board or the State Water Resources Control Board in the form of an NPDES permit pursuant to Water Code Section 13370 (other than the municipal NPDES permit).

Outfall means a point source as defined by 40 CFR 122.2 at the point where a municipal separate storm sewer discharges to waters of the United States and does not include open conveyances connecting two (2) municipal separate storm sewers, or pipes, tunnels or other conveyances which connect segments of the same stream or other waters of the United States and are used to convey waters of the United States (40 CFR 122.26(b)(9)).

Parking lot means land area or a facility for the parking or storage of motor vehicles used for businesses, commerce, industry or personal use with a lot size of five thousand (5,000) square feet or more of surface area, or with twenty-five (25) or more parking spaces.

Planning priority projects means those projects specified in subsection 14-13.3(c) that are required to incorporate appropriate stormwater mitigation measures into the design plan for their respective projects.

Pollutant means those pollutants defined in Section 502(6) of the federal Clean Water Act (33 U.S.C. Section 1362(6)), or incorporated into California Water Code Section 13373. Examples of pollutants include, but are not limited to, the following:

1.    Commercial and industrial waste (such as fuels, solvents, detergents, plastic pellets, hazardous substances, fertilizers, pesticides, slag, ash and sludge);

2.    Metals such as cadmium, lead, zinc, copper, silver, nickel, chromium, and nonmetals such as phosphorus and arsenic;

3.    Petroleum hydrocarbons (such as fuels, lubricants, surfactants, waste oils, solvents, coolants and grease);

4.    Excessive eroded soils, sediment and particulate materials in amounts which may adversely affect the beneficial use of the receiving waters, flora or fauna of the state;

5.    Animal wastes (such as discharge from confinement facilities, kennels, pens, recreational facilities, stables and show facilities);

6.    Substances having characteristics such as pH less than six (6) or greater than nine (9), or unusual coloration or turbidity, or excessive levels of fecal coliform, or fecal streptococcus, or enterococcus;

The term pollutant shall not include uncontaminated stormwater, potable water or reclaimed water generated by a lawfully permitted water treatment facility.

Project means all development, redevelopment, and land disturbing activities. The term is not limited to “project” as defined under CEQA (California Public Resources Code Section 21065).

Rainfall harvest and use means an LID BMP system designed to capture runoff, typically from a roof but can also include runoff capture from elsewhere within the site, and to provide for temporary storage until the harvested water can be used for irrigation or nonpotable uses. The harvested water may also be used for potable water uses if the system includes disinfection treatment and is approved for such use by the local building department.

Receiving water means “water of the United States” into which waste and/or pollutants are or may be discharged.

Redevelopment means land disturbing activity that results in the creation, addition, or replacement of five thousand (5,000) square feet or more of impervious surface area on an already developed site. Redevelopment includes, but is not limited to: the expansion of a building footprint; addition or replacement of a structure; replacement of impervious surface area that is not part of routine maintenance activity; and land disturbing activity related to structural or impervious surfaces. It does not include routine maintenance to maintain original line and grade, hydraulic capacity, or original purpose of facility, nor does it include emergency construction activities required to immediately protect public health and safety.

Regional Board means the California Regional Water Quality Control Board, Los Angeles Region.

Restaurant means a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption (Standard Industrial Classification Code 5812).

Retail gasoline outlet means any facility engaged in selling gasoline and lubricating oils.

Routine maintenance includes, but is not limited to, projects conducted to:

1.    Maintain the original line and grade, hydraulic capacity, or original purpose of the facility.

2.    Perform as needed restoration work to preserve the original design grade, integrity and hydraulic capacity of flood control facilities.

3.    Includes road shoulder work, regrading dirt or gravel roadways and shoulders and performing ditch cleanouts.

4.    Update existing lines and facilities, which includes replacing existing lines with new materials or pipes, to comply with applicable codes, standards, and regulations regardless of if such projects result in increased capacity.

5.    Repair leaks.

Routine maintenance does not include construction of new lines or facilities resulting from compliance with applicable codes, standards and regulations.

Runoff means any runoff including stormwater and dry weather flows from a drainage area that reaches a receiving water body or subsurface. During dry weather it is typically comprised of base flow either contaminated with pollutants or uncontaminated, and nuisance flows.

Significant ecological areas (SEAs) means an area that is determined to possess an example of biotic resources that cumulatively represent biological diversity, for the purposes of protecting biotic diversity, as part of the Los Angeles County general plan. Areas are designated as SEAs if they possess one or more of the following criteria:

1.    The habitat of rare, endangered, and threatened plant and animal species.

2.    Biotic communities, vegetative associations, and habitat of plant and animal species that are either one of a kind, or are restricted in distribution on a regional basis.

3.    Biotic communities, vegetative associations, and habitat of plant and animal species that are either one of a kind or are restricted in distribution in Los Angeles County.

4.    Habitat that at some point in the life cycle of a species or group of species serves as concentrated breeding, feeding, resting, or migrating grounds and is limited in availability either regionally or within Los Angeles County.

5.    Biotic resources that are of scientific interest because they are either an extreme in physical/geographical limitations, or represent an unusual variation in a population or community.

6.    Areas important as game species habitat or as fisheries.

7.    Areas that would provide for the preservation of relatively undisturbed examples of natural biotic communities in Los Angeles County.

8.    Special areas.

Site means the land or water area where any facility or activity is physically located or conducted, including adjacent land used in connection with the facility or activity.

Source control BMP means any schedule of activities, prohibition of practices, maintenance procedures, managerial practices or operational practices that aim to prevent stormwater pollution by reducing the potential for contamination at the source of pollution.

Standard urban stormwater mitigation plan (SUSMP) means a report submitted by an applicant for approval by the director prior to issuance of a building, grading, planning or similar permit outlining the necessary LID requirements and BMPs which must be incorporated into design plans for development or redevelopment projects.

Storm drain system means any facility or any parts of the facility, including streets, gutters, conduits, natural or artificial drains, channels and watercourses that are used for the purpose of collecting, storing, transporting or disposing of stormwater and are located within the city.

Stormwater runoff means that part of precipitation (rainfall) which travels via flow across a surface to the MS4 or receiving waters from impervious, semi-pervious or pervious surfaces. When all other factors are equal, runoff increases as the perviousness of a surface decreases.

Structural BMP means any structural facility designed and constructed to mitigate the adverse impacts of stormwater and urban runoff pollution (e.g., canopy, structural enclosure). Structural BMPs may include both treatment control BMPs and source control BMPs.

Treatment means the application of engineered systems that use physical, chemical or biological processes to remove pollutants. Such processes include, but are not limited to, filtration, gravity settling, media adsorption, biodegradation, biological uptake, chemical oxidation and UV radiation.

Treatment control BMP means any engineered system designed to remove pollutants by simple gravity settling of particulate pollutants, filtration, biological uptake, media adsorption or any other physical, biological or chemical process.

Urban runoff means surface water flow produced by non-stormwater resulting from residential, commercial and industrial activities involving the use of potable and nonpotable water. (Ord. #1671, §1)

14-13.3 Standard Urban Stormwater Mitigation Plan (SUSMP) And Low Impact Development (LID) Requirements For New Development And Redevelopment Projects.

a.    Objective: Pursuant to Part VI.D.7.b of the municipal NPDES permit, the provisions of this section establish requirements for construction activities and facility operations of development and redevelopment projects to comply with the current municipal NPDES permit to lessen the water quality impacts of development by using smart growth practices and integrate LID practices and standards for stormwater pollution mitigation through means of infiltration, evapotranspiration, biofiltration, and rainfall harvest and use. Except as otherwise provided herein, the city shall administer, implement and enforce the provisions of this section.

b.    Scope: This section contains requirements for stormwater pollution control measures in development and redevelopment projects and authorizes the city to further define and adopt stormwater pollution control measures, and to develop LID principles and requirements, including but not limited to the objectives and specifications for integration of LID strategies. As specified in this section, certain planning priority projects shall meet the requirements of this section through the preparation and submittal of a standard urban stormwater mitigation plan (SUSMP), which shall include the applicable LID requirements set forth in this section as an element of the SUSMP.

c.    Applicability – Planning Priority Projects: The following development and redevelopment projects shall be designated as planning priority projects, which are subject to city conditioning and approval for the design and implementation of post-construction controls to mitigate stormwater pollution prior to completion of the projects, and shall meet the requirements of this section:

1.    New Development Projects:

(a)    All development projects equal to one acre or greater of disturbed area that adds more than ten thousand (10,000) square feet of impervious surface area.

(b)    Industrial parks ten thousand (10,000) square feet or more in surface area.

(c)    Commercial malls ten thousand (10,000) square feet or more in surface area.

(d)    Retail gasoline outlets with five thousand (5,000) square feet or more of surface area.

(e)    Restaurants (Standard Industrial Classification (SIC) of 5812) with five thousand (5,000) square feet or more of surface area.

(f)    Parking lots with five thousand (5,000) square feet or more of impervious surface area, or with twenty-five (25) or more parking spaces.

(g)    Streets and roads construction of ten thousand (10,000) square feet or more of impervious surface area. Street and road construction applies to stand-alone streets, roads, highways, and freeway projects, and also applies to streets within larger projects.

(h)    Automotive service facilities (Standard Industrial Classification (SIC) of 5013, 5014, 5511, 5541, 7532 through 7534 and 7536 through 7539) five thousand (5,000) square feet or more in surface area.

(i)    Projects located in or directly adjacent to, or discharging directly to a significant ecological area (SEA), where the development will:

(1)    Discharge stormwater runoff that is likely to impact a sensitive biological species or habitat; and

(2)    Create two thousand five hundred (2,500) square feet or more of impervious surface area.

(3)    Single-family hillside homes.

2.    Redevelopment Projects:

(a)    Land disturbing activity that results in the creation or addition or replacement of five thousand (5,000) square feet or more of impervious surface area on an already developed site on planning priority project categories.

(b)    Where redevelopment results in an alteration to more than fifty percent (50%) of impervious surfaces of a previously existing development, and the existing development was not subject to post-construction stormwater quality control requirements, the entire project must be mitigated.

(c)    Where redevelopment results in an alteration of less than fifty percent (50%) of impervious surfaces of a previously existing development, and the existing development was not subject to post-construction stormwater quality control requirements, only the alteration must be mitigated, and not the entire development.

(d)    Redevelopment does not include routine maintenance activities that are conducted to maintain original line and grade, hydraulic capacity, original purpose of facility or emergency redevelopment activity required to protect public health and safety. Impervious surface replacement, such as the reconstruction of parking lots and roadways which does not disturb additional area and maintains the original grade and alignment, is considered a routine maintenance activity. Redevelopment does not include the repaving of existing roads to maintain original line and grade.

(e)    Existing single-family dwelling and accessory structures are exempt from the redevelopment requirements unless such projects create, add, or replace ten thousand (10,000) square feet of impervious surface area.

d.    Specific Requirements: The site for every planning priority project shall be designed to control pollutants, pollutant loads, and runoff volume to the maximum extent feasible by minimizing impervious surface area and controlling runoff from impervious surfaces through infiltration, evapotranspiration, bioretention and/or rainfall harvest and use. In addition, the following specific requirements apply:

1.    New Single-Family Hillside Homes: A new single-family hillside home development project shall include mitigation measures to:

(a)    Conserve natural areas;

(b)    Protect slopes and channels;

(c)    Provide storm drain system stenciling and signage;

(d)    Divert roof runoff to vegetated areas before discharge unless the diversion would result in slope instability; and

(e)    Direct surface flow to vegetated areas before discharge, unless the diversion would result in slope instability.

2.    Street and Road Construction of Ten Thousand (10,000) Square Feet or More: Street and road construction of ten thousand (10,000) square feet or more of impervious surface shall follow the city’s Green Street Manual developed by the director and approved by city council resolution. The city’s Green Street Manual shall be based on the city of Lynwood’s Green Streets Manual.

3.    The remainder of planning priority projects shall prepare an SUSMP to comply with the following:

(a)    Retain stormwater runoff on site for the stormwater quality design volume (SWQDV), defined as the runoff from:

(1)    The 85th percentile twenty-four (24) hour runoff event as determined from the Los Angeles County 85th percentile precipitation isohyetal map; or

(2)    The volume of runoff produced from a three-quarter inch (0.75"), twenty-four (24) hour rain event, whichever is greater.

(b)    Minimize hydromodification impacts to natural drainage systems as defined in the municipal NPDES permit.

(c)    To demonstrate technical infeasibility, the project applicant must demonstrate that the project cannot reliably retain one hundred percent (100%) of the SWQDV on site, even with the maximum application of green roofs and rainwater harvest and use, and that compliance with the applicable post-construction requirements would be technically infeasible by submitting a site-specific hydrologic and/or design analysis conducted and endorsed by a registered professional engineer, geologist, architect, and/or landscape architect. Technical infeasibility may result from conditions including the following:

(1)    The infiltration rate of saturated in situ soils is less than three-tenths inch (0.3") per hour and it is not technically feasible to amend the in situ soils to attain an infiltration rate necessary to achieve reliable performance of infiltration or bioretention BMPs in retaining the SWQDV on site;

(2)    Locations where seasonal high groundwater is within five feet (5') to ten feet (10') of surface grade;

(3)    Locations within one hundred feet (100') of a groundwater well used for drinking water;

(4)    Brownfield development sites or other locations where pollutant mobilization is a documented concern;

(5)    Locations with potential geotechnical hazards;

(6)    Smart growth and infill or redevelopment locations where the density and/or nature of the project would create significant difficulty for compliance with the on-site volume retention requirement.

(d)    If partial or complete on-site retention is technically infeasible, the project site may biofiltrate one and one-half (1 1/2) times the portion of the remaining SWQDV that is not reliably retained on site. Biofiltration BMPs must adhere to the design specifications provided in municipal NPDES permit.

(1)    Additional alternative compliance options such as off-site infiltration and groundwater replenishment projects may be available to the project site. The project site should contact the department of public works to determine eligibility.

(e)    The remaining SWQDV that cannot be retained or biofiltered on site must be treated on site to reduce pollutant loading. BMPs must be selected and designed to meet pollutant-specific benchmarks as required per the municipal NPDES permit. Flow-through BMPs may be used to treat the remaining SWQDV and must be sized based on a rainfall intensity of:

(1)    Two-tenths inch (0.2") per hour; or

(2)    The one-year, one-hour rainfall intensity as determined from the most recent Los Angeles County isohyetal map, whichever is greater.

e.    Verify Maintenance of BMPs: If a project applicant has included or is required to include structural or treatment control BMPs in project plans, the applicant shall provide verification of maintenance provisions. The verification shall include the applicant’s signed statement, as part of its project application, accepting responsibility for all structural and treatment control BMP maintenance until such time, if any, the property is transferred.

f.    Issuance of Certificates of Occupancy: As a condition for issuing a certificate of occupancy for a planning priority project identified in this section, the director shall require facility operators and/or owners to build all the stormwater pollution control BMPs and structural or treatment control BMPs that are shown on the approved project plans and to submit a signed certification statement stating that the site and all structural or treatment control BMPs will be maintained in compliance with the SUSMP and other applicable regulatory requirements.

g.    Transfer of Properties Subject to Requirement for Maintenance of Structural and Treatment Control BMPs:

1.    The transfer or lease of a property subject to a requirement for maintenance of structural and treatment control BMPs shall include conditions requiring the transferee and its successors and assigns to either (a) assume responsibility for maintenance of any existing structural or treatment control BMP or (b) to replace an existing structural or treatment control BMP with new control measures or BMPs meeting the then current standards of the city and the SUSMP. Such requirement shall be included in any sale or lease agreement or deed for such property. The condition of transfer shall include a provision that the successor property owner or lessee conduct maintenance inspections of all structural or treatment control BMPs at least once a year and retain proof of inspection.

2.    For residential properties where the structural or treatment control BMPs are located within a common area which will be maintained by a homeowners association, language regarding the responsibility for maintenance shall be included in the project’s conditions, covenants and restrictions (CC&Rs). The transfer of this information shall also be required with any subsequent sale of the property.

3.    If structural or treatment control BMPs are located within an area proposed for dedication to a public agency, said BMPs shall be the responsibility of the developer until the dedication is accepted by the public agency. (Ord. #1671, §1)

14-13.4 Authority:

a.    Define And Adopt: The public works director/city engineer shall have the authority to define and adopt a standard urban stormwater mitigation plan and development best management practices necessary to control stormwater pollution from new developments and facility operations to the maximum extent practicable pursuant to the municipal NPDES permit.

b.    Requirements: The public works director/city engineer shall have the authority to withhold grading and/or building permits for developments until:

1.    The applicant incorporates into the development best management practices necessary to control stormwater pollution in accordance with the municipal NPDES permit.

2.    The city of Lynwood receives a covenant and agreement, signed by the owner(s) of the property and recorded by the Los Angeles County recorder, declaring that the best management practices necessary to control stormwater pollution shall be installed and/or constructed and maintained in proper working conditions at all times.

3.    The city of Lynwood receives from a certified and registered civil engineer plans that depict specific best management practices incorporated into a project that identify stormwater pollution prevention measures, during and after construction. (Ord. #1500, §1; Ord. #1671, §1. Formerly 14-13.2)

14-13.5 Supplemental Provisions:

Provisions of this section shall be complementary to, not replaced by, any requirements for stormwater mitigation existing under the California Environmental Quality Act. (Ord. #1500, §1; Ord. #1671, §1. Formerly 14-13.3)

14-13.6 Authority To Inspect And Enforce Stormwater Pollution Control Measures:

a.    Notwithstanding the provisions of the grading or building permit, noncompliance with any provisions of this section or the required covenant and agreement shall be considered an infraction. Each day of noncompliance may be considered a separate violation. Such infraction penalties are set forth by city council resolution, as amended from time to time.

b.    Whenever it is necessary to make an inspection to enforce or verify compliance with any stormwater control provisions, as imposed by this section, the public works director/city engineer and/or his authorized representatives are hereby authorized to enter such property at any reasonable time to inspect for compliance with best management practices and perform any duty imposed by this section or other applicable law. (Ord. #1500, §1; Ord. #1671, §1. Formerly 14-13.4)