Walnut Municipal Code Ch. 5.08 Stormwater and Urban Runoff Pollution Control

This chapter shall be known as the "City of Walnut Stormwater Management and Discharge Control Ordinance."

A. The Federal Clean Water Act (33 U.S.C. Section 1251 et seq.) provides for the regulation and reduction of pollutants discharged into the waters of the United States by extending National Pollutant Discharge Elimination System (hereinafter "NPDES") requirements to stormwater and urban runoff discharge into municipal storm drain systems.

B. Stormwater and urban runoff flows from individual properties onto streets, then through storm drains passing through the City.

C. The City of Walnut is a permittee under the "Waste Discharge Requirements for Municipal Separate Storm Sewer System (MS4) Discharges within the Coastal Watersheds of Los Angeles County, Except those Discharges Originating from the City of Long Beach MS4," issued by the California Regional Water Quality Control Board—Los Angeles Region," (Order No. R4-2012-0175) which also serves as an NPDES permit under the Federal Clean Water Act (NPDES No. CAS004001), as well as waste discharge requirements under California law (the "Municipal NPDES Permit").

D. Part 1, of the Municipal NPDES Permit requires the City to effectively prohibit non-stormwater discharges from within its boundaries, into that portion of the municipal separate storm sewer system ("MS4") which it owns or operates and into watercourses, except where such discharges:

1. Are covered by a separate individual or general NPDES permit for non-stormwater discharges; or

2. Fall within one of the categories below, and meet all conditions when specified by the Regional Board Executive Officer:

a. Category A—Natural flow:

i. Natural springs and rising groundwater;

ii. Flows from riparian habitats or wetlands;

iii. Stream diversions, permitted by the State Board; and

iv. Uncontaminated groundwater infiltration (as defined by 40 CFR 35.2005(20)).

b. Category B—Flows from emergency fire fighting activity.

c. Category C—Flows incidental to urban activities.

i. Reclaimed and potable landscape irrigation runoff;

ii. Potable drinking water supply and distribution system releases (consistent with American Water Works Association guidelines for dechlorination and suspended solids reduction practices);

iii. Drains from foundations, footings and crawl spaces;

iv. Air conditioning condensate;

v. Dechlorinated/debrominated swimming pool discharges;

vi. Dewatering of lakes and decorative fountains;

vii. Non-commercial car washing by residents or by non-profit organizations; and

viii. Sidewalk rinsing.

3. The regional board executive officer may add or remove categories of non-stormwater discharges above. Furthermore, in the event that any of the above categories of non-stormwater discharges are determined to be a source of pollutants by the regional board executive officer, the discharge will no longer be exempt from this prohibition unless the permittee implements conditions approved by the regional board executive officer to ensure that the discharge is not a source of pollutants. Notwithstanding the above, the regional board executive officer may impose additional prohibitions of non-stormwater discharge in consideration of antidegradation policies and TMDLs.

E. Part 3, Section G.4 of the Municipal NPDES Permit requires the City to demonstrate by February 3, 2003 that it possesses the legal authority necessary to control discharges to and from those portions of the MS4 over which it has jurisdiction, so as to comply with the Municipal NPDES Permit and to specifically prohibit certain discharges identified in the Municipal NPDES Permit.

F. The Municipal NPDES Permit has called for the development of a countrywide stormwater quality management program (SQMP) in which the City will participate, which will in turn require the development and the implementation of programs for, among other things, the elimination of illicit connections and illicit discharges, development planning, development construction, and public information and education requirements, and which may require the later adoption of additional legal authority to implement such programs as they are developed by the permittees and approved by the regional board.

G. Part 3, Section G.2 of the Municipal NPDES Permit requires the City to possess authority to enter sample, inspect, review and copy records, and require regular reports from industrial facilities (including construction sites) discharging polluted or with the potential to discharge polluted stormwater runoff into its MS4.

H. In order to control, in a cost-effective manner, the quantity and quality of stormwater and urban runoff to the maximum extent practicable, the adoption of reasonable regulations, as set forth herein, is essential.

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 thereby reducing the level of contamination of stormwater and urban runoff into 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 thereby fully and timely comply with the terms of the Municipal NPDES Permit while the CSWMP and the WMAP are being developed by the permittees under the Municipal NPDES Permit, and in contemplation of the subsequent amendment of this article or adoption by the City of additional provisions of this article to implement the subsequently adopted CSWMP and WMAP, or other programs developed under the Municipal NPDES Permit.

Except as specifically provided herein, any term used in this section shall be defined as that term in the current Municipal NPDES Permit, or if it is not specifically defined in either the Municipal NPDES Permit, then as such term is defined in the Federal Clean Water Act, as amended, and/or the regulations promulgated thereunder. If the definition of any term contained in this chapter conflicts with the definition of the same term in the current 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:

"Automotive service facility"

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, 5541, 5511, provided that these facilities have no outside activities or materials that may be exposed to stormwater (Source: Order No. R4-2012-0175).

"Basin plan"

means the Water Quality Control Plan, Los Angeles Region, Basin Plan for the Coastal Watersheds of Los Angeles and Ventura Counties, adopted by the Regional Water Board on June 13, 1994 and subsequent amendments (Source: Order No. R4-2012-0175).

"Best management practice (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 (Source: Order No. R4-2012-0175).

"Biofiltration"

means a 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 (Modified from: Order No. R4-2012-0175).

"Bioretention"

means a 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 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 the Municipal NPDES Permit, 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 (Modified from: Order No. R4-2012-0175).

"Bioswale"

means a 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 (Source: Order No. R4-2012-0175).

"City"

means the City of Walnut.

"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 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: minimalls, strip malls, other retail complexes, and enclosed shopping malls or shopping centers (Source: Order No. R4-2012-0175).

"Construction activity"

means any construction or demolition activity, clearing, grading, grubbing, or excavation or any other activity that result 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 (Source: Order No. R4-2012-0175).

"Control"

means to minimize, reduce or eliminate by technological, legal, contractual, or other means, the discharge of pollutants from an activity or activities (Source: Order No. R4-2012-0175).

"Development"

means 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 (Source: Order No. R4-2012-0175).

"Directly adjacent"

means situated within 200 feet of the contiguous zone required for the continued maintenance, function, and structural stability of the environmentally sensitive area (Source: Order No. R4-2012-0175).

"Discharge"

means any release, spill, leak, pump, flow, escape, dumping, or disposal of any liquid, semi-solid, or solid substance.

"Disturbed area"

means an area that is altered as a result of clearing, grading, and/or excavation (Source: Order No. R4-2012-0175).

"Flow-through BMPs"

means modular, vault type "high flow biotreatment" devices contained within an impervious vault with an underdrain or designed with an impervious liner and an underdrain (Modified from: Order No. R4-2012-0175).

"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 a 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 (Source: Order No. R4-2012-0175).

"Hazardous material(s)"

means any material(s) defined as hazardous by Division 20, Chapter 6.95 of the California Health and Safety Code.

"Hillside"

means a property located in an area with known erosive soil conditions, where the development contemplates grading on any natural slope that is 25% or greater and where grading contemplates cut or fill slopes (Source: Order No. R4-2012-0175).

"Impervious surface"

means any man-made or modified surface that prevents or significantly reduces the entry of water into the underlying soil, resulting in runoff from the surface in greater quantities and/or at an increased rate, when compared to natural conditions prior to development. Examples of places that commonly exhibit impervious surfaces include parking lots, driveways, roadways, storage areas, and rooftops. The imperviousness of these areas commonly results from paving, compacted gravel, compacted earth, and oiled earth.

"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 modality coincides: highways, railroads, airports, and navigable rivers. It includes office parks, which have offices and light industry (Source: Order No. R4-2012-0175).

"Infiltration BMP"

means a 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 (Source: Order No. R4-2012-0175).

"LID"

means low impact development. LID consists of building and landscape features designed to retain or filter stormwater runoff (Source: Order No. R4-2012-0175).

"MS4"

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

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;

Designed or used for collecting or conveying stormwater;

Which is not a combined sewer; and

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

(40 CFR Section 122.26(b)(8)) (Source: Order No. R4-2012-0175).

"National Pollutant Discharge Elimination System (NPDES)"

means the national program for issuing, modifying, revoking and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under CWA Sections 307, 402, 318, and 405. The term includes an "approved program" (Source: Order No. R4-2012-0175).

"Natural drainage system"

means a drainage system that has not been improved (e.g., channelized or armored). The clearing or dredging of a natural drainage system does not cause the system to be classified as an improved drainage system (Source: Order No. R4-2012-0175).

"New development"

means land disturbing activities; structural development, including construction or installation of a building or structure, creation of impervious surfaces; and land subdivision (Source: Order No. R4-2012-0175).

"Non-stormwater discharge"

means any discharge to a municipal storm drain system that is not composed entirely of stormwater (Source: Order No. R4-2012-0175).

"Parking lot"

means land area or facility for the parking or storage of motor vehicles used for businesses, commerce, industry, or personal use, with a lot size of 5,000 square feet or more of surface area, or with 25 or more parking spaces (Source: Order No. R4-2012-0175).

"Person"

means any individual, partnership, co-partnership, firm, company, corporation, association, joint stock company, trust, state, governmental entity or any other legal entity, or their legal representatives, agents or assigns. The masculine gender shall include the feminine and the singular shall include the plural where indicated by the context.

"Planning priority projects"

means development projects subject to permittee conditioning and approval for the design and implementation of post-construction controls to mitigate stormwater pollution, prior to completion of the project(s) (Modified from: Order No. R4-2012-0175).

"Pollutant"

means any "pollutant" defined in Section 502(6) of the Federal Clean Water Act or incorporated into the California Water Code Section 13373. Pollutants may include, but are not limited to, the following:

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

Metals (such as cadmium, lead, zinc, copper, silver, nickel, chromium, and non-metals such as phosphorus and arsenic).

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

Excessive eroded soil, sediment, and particulate materials in amounts that may adversely affect the beneficial use of the receiving waters, flora, or fauna of the State.

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

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

"Project"

means all development, redevelopment, and land disturbing activities. The term is not limited to "Project" as defined under CEQA (Public Resources Code Section 21065) (Source: Order No. R4-2012-0175).

"Rainfall harvest and use"

means a 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 non-potable 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 (Source: Order No. R4-2012-0175).

"Receiving water"

means "water of the United States" into which waste and/or pollutants are or may be discharged (Source: Order No. R4-2012-0175).

"Redevelopment"

means land-disturbing activity that results in the creation, addition, or replacement of 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 (Source: Order No. R4-2012-0175).

"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 (SIC Code 5812) (Source: Order No. R4-2012-0175).

"Retail gasoline outlet"

means any facility engaged in selling gasoline and lubricating oils (Source: Order No. R4-2012-0175).

"Routine maintenance"

projects include, but are not limited to:

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

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

Road shoulder work, regrading dirt or gravel roadways and shoulders and performing ditch cleanouts.

Updating existing lines [1] and facilities to comply with applicable codes, standards, and regulations regardless if such projects result in increased capacity.

Repairing leaks.

"Routine maintenance"

does not include construction of new [2] lines or facilities resulting from compliance with applicable codes, standards and regulations.

"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:

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

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.

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.

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

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.

Areas important as game species habitat or as fisheries.

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

Special areas (Source: Order No. R4-2012-0175).

"Site"

means 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: Order No. R4-2012-0175).

"Storm drain system"

means any facilities or any part of those facilities, 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 of Walnut.

"Stormwater" or "stormwater"

means water that originates from atmospheric moisture (rain or snow) and that falls onto land, water, or other surfaces. Without any change in its meaning, this term may be spelled or written as one word or two separate words.

"Stormwater runoff"

means that part of precipitation (rainfall or snowmelt) which travels across a surface to the storm drain system or receiving waters.

"SUSMP"

means the Los Angeles Countywide Standard Urban Stormwater Mitigation Plan. The SUSMP was required as part of the previous Municipal NPDES Permit (Order No. 01-182, NPDES No. CAS004001) and required plans that designate best management practices (BMPs) that must be used in specified categories of development projects.

"Urban runoff"

means surface water flow produced by storm and non-storm events. Non-storm events include flow from residential, commercial, or industrial activities involving the use of potable and non-potable water.

[1]

Update existing lines includes replacing existing lines with new materials or pipes.

[2]

New lines are those that are not associated with existing facilities and are not part of a project to update or replace existing lines (Source: Order No. R4-2012-0175).

This chapter shall be construed to assure consistency with the requirements of the Federal Clean Water Act and acts amendatory thereof or supplementary thereto, applicable implementing regulations, and the Municipal NPDES Permit, and any amendment, revision or reissuance thereof.

A. Illicit Discharges and Connections. It is prohibited to commence, establish, use, maintain or continue any illicit connections to the municipal separate storm sewer system or any illicit discharges to the municipal separate storm sewer system. This prohibition against illicit connections applies to the use, maintenance, or continuation of any illicit connection, whether that connection was established prior to, or after the effective date of the ordinance codified in this chapter.

B. Littering. It is prohibited to throw, deposit, place, leave, maintain, keep, or permit to be thrown, deposited, placed, left, or maintained or kept, any refuse, rubbish, garbage, or any other discarded or abandoned objects, articles or accumulations, in or upon any street, alley, sidewalk, storm drain, inlet, catch basin conduit or drainage structure, business place, or upon any public or private plot of land in the City, so that the same might be or become a pollutant. No person shall throw or deposit litter in any fountain, pond, lake, creek, stream, or other body of water within the City. This subsection shall not apply to refuse, rubbish or garbage deposited in containers, bags or other appropriate receptacles which are placed in designated locations for regular solid waste pick up and disposal.

C. Disposal of Landscape Debris. It is prohibited to intentionally dispose of leaves, dirt, or other landscape debris into the municipal separate storm sewer system.

D. Non-Stormwater Discharges. The following non-stormwater discharges into the municipal stormwater system are prohibited unless in compliance with a separate NPDES permit or pursuant to a discharge exemption by the regional board, the regional board’s executive officer, or the State Water Resources Control Board:

1. The discharge of untreated wash waters to the MS4 when gas stations, auto repair garages, or other type of automotive service facilities are cleaned;

2. The discharge of untreated wastewater to the MS4 from mobile auto washing, steam cleaning, mobile carpet cleaning, and other such mobile commercial and industrial operations;

3. Discharges to the MS4 from areas where repair of machinery and equipment, including motor vehicles, which are visibly leaking oil, fluid or antifreeze, is undertaken;

4. Discharges of untreated runoff to the MS4 from storage areas of materials containing grease, oil, or other hazardous substances, and uncovered receptacles containing hazardous materials;

5. Discharges of chlorinated/brominated swimming pool filter backwash to the MS4;

6. Discharges of untreated runoff from the washing of toxic materials from paved or unpaved areas to the MS4; provided, however, that non-industrial and non-commercial activities which incidentally generate urban runoff, such as the hosing of sidewalks, and the non-commercial hand-washing of cars, shall be excluded from this prohibition;

7. Discharges to the MS4 from washing impervious surfaces in industrial/commercial areas which results in a discharge of untreated runoff to the MS4, unless specifically required by state’s, or the City’s, or Los Angeles County’s health and safety codes, or permitted under a separate NPDES permit;

8. Discharges from the washing out of concrete or cement laden wash water from concrete trucks, pumps, tools and equipment to the MS4;

9. Dumping or disposal of materials into the MS4 other than stormwater, such as:

a. Litter, landscape debris and construction debris;

b. Any state or federally banned or unregistered pesticides;

c. Food and food processing wastes; and

d. Fuel and chemical wastes, animal wastes, garbage, batteries and other materials that have the potential adverse impacts on water quality; or

10. The disposal of hazardous wastes into trash containers used for municipal trash disposal where such disposal causes or threatens to cause a direct or indirect discharge to the MS4.

E. Discharges in Violation of the Municipal NPDES Permit. Any discharge that would result in or contribute to a violation of the Municipal NPDES Permit, either separately or in combination with other discharges, is prohibited. Liability for any such discharge shall be the responsibility of the person(s) causing or responsible for the discharge, and such person(s) shall defend, indemnify and hold harmless the City from all losses, liabilities, claims, or causes of actions in any administrative or judicial action relating to such discharge.

Discharges from those activities specifically identified in, or pursuant to Part 2, Section II.C of the Municipal NPDES Permit as being exempted discharges, conditionally exempted discharges, or designated discharges shall not be considered a violation of this chapter, provided that any applicable BMPs developed pursuant to the Municipal NPDES Permit are implemented to minimize any adverse impacts from such identified sources.

Owners and occupants of property within the City shall comply with the following requirements:

A. Septic Waste. No person shall leave, deposit, discharge, dump, or otherwise expose any chemical or septic waste to precipitation in an area where a discharge to City streets or the MS4 may or does occur.

B. Use of Water. Runoff of water used for irrigation purposes shall be minimized to the maximum extent practicable. Runoff of water from the permitted washing down of paved areas shall be minimized to the maximum extent practicable.

C. Storage of Materials, Machinery, and Equipment. Machinery or equipment that is to be repaired or maintained in areas susceptible to or exposed to stormwater, shall be placed in a manner so that leaks, spills and other maintenance-related pollutants are not discharged to the MS4.

D. Removal and Disposal of Debris from Industrial/Commercial Motor Vehicle Parking Lots. Industrial/commercial motor vehicle parking lots with more than 25 parking spaces that are located in areas potentially exposed to stormwater shall be swept regularly or other equally effective measures shall be utilized to remove debris from such parking lots.

E. Food Wastes. Food wastes generated by nonresidential food service and food distribution sources shall be properly disposed of and in a manner so such wastes are not discharged to the municipal separate storm sewer system.

F. Best Management Practices. Best management practices shall be used in areas exposed to stormwater for the removal and lawful disposal of all fuels, chemicals, fuel land chemical wastes, animal wastes, garbage, batteries, or other materials which have potential adverse impacts on water quality.

A. Each industrial discharger, discharger associated with construction activity, or other discharger described in any general stormwater permit addressing such discharges, as may be issued by the U.S. Environmental Protection Agency, the State Water Resources Control Board, or the regional board shall comply with all requirements of such permit. Each discharger identified in an individual NPDES permit shall comply with and undertake all activities required by such permit. Proof of compliance with any such permit may be required in a form acceptable to the City Engineer, or his or her designated representative, prior to the issuance of any grading, building or occupancy permits, or any other type of permit or license issued by the City.

B. Any person or company engaging in construction activity that requires an NPDES construction permit must demonstrate possession of such permit before grading and/or building permits can be issued. The NPDES permit shall be retained on site and shall be shown to City officers or inspectors at their request.

C. The following best management practices shall apply to all construction sites.

1. Runoff, sediment and construction waste from construction sites and parking areas shall not leave the site.

2. Any sediments or other materials which are tracked off the site shall be removed the same day as they are tracked off the site. Where determined necessary by the building official or designated representative, a sediment barrier shall be installed.

3. Excavated soil shall be located on the site in a manner that eliminates the possibility of sediments running into the street or adjoining properties. Soil piles shall be covered until the soil is either used or removed.

4. No washing or construction or other industrial vehicles shall be allowed adjacent to a construction site. No runoff from washing vehicles on a construction site is allowed to leave the site.

5. Any other best management practice for construction sites the City may adopt.

D. All persons or companies engaged in industrial activity in the City shall acquire an NPDES industrial permit before discharging any non-stormwater runoff into the storm drain system. The NPDES permit shall be retained on site and shall be shown to City officers or inspectors at their request.

E. The following best management practices shall apply to all industrial activity sites.

1. Any best management practice for industrial activity sites the City may adopt.

2. Treatment control BMPs.

A. Violations Deemed a Public Nuisance.

1. Any condition caused or permitted to exist in violation of any of the provisions of this chapter is hereby determined to be a threat to the public health, safety and welfare, is declared and deemed a public nuisance, and may be abated by any authorized enforcement officer, and a civil or criminal action to abate, enjoin or otherwise compel the cessation of such nuisance may be brought by the City Attorney.

2. The cost of such abatement and restoration shall be borne by the owner of the property and the cost thereof shall be invoiced to the owner of the property, as provided by law or ordinance for the recovery of nuisance abatement costs.

3. If any violation of this chapter constitutes a seasonal and recurrent nuisance, the City Engineer shall so declare. The failure of any person to take appropriate annual precautions to prevent stormwater pollution after written notice of a determination under this paragraph shall constitute a public nuisance and a violation of this chapter.

B. Concealment. Causing, permitting, aiding, abetting, or concealing a violation of any provision of this chapter shall constitute a violation of such provision.

C. Civil Actions. In addition to any other remedies provided in this section, any violation of this section may be enforced by civil action brought by the City. In any such action, the City may seek, as appropriate, any or all of the following remedies:

1. A temporary and/or permanent injunction;

2. Assessment of the violator for the costs of any investigation, inspection, or monitoring survey which led to the establishment of the violation, and for the reasonable costs of preparing and bringing legal action under this subsection;

3. Costs incurred in removing, correcting, or terminating the adverse effects resulting from violation;

4. Compensatory damages for loss or destruction to water quality, wildlife, fish and aquatic life.

D. Administrative Enforcement Powers. In addition to the other enforcement powers and remedies established by this chapter, any authorized enforcement officer has the authority to utilize the following administrative remedies:

1. Cease and Desist Orders. When an authorized enforcement officer finds that a discharge has taken place or is likely to take place in violation of this chapter, the officer may issue an order to cease and desist such discharge, or practice, or operation likely to cause such discharge and direct that those persons not complying shall: (a) comply with the requirement, (b) comply with a time schedule for compliance, and (c) take appropriate remedial or preventive action to prevent the violation from recurring.

2. Notice to Clean. Whenever an authorized enforcement officer finds any oil, earth, debris, grass, weeds, dead trees, tin cans, rubbish, refuse, waste or any other material of any kind, in or upon the sidewalk abutting or adjoining any parcel of land, or upon any parcel of land or grounds, which may result in pollutants entering the municipal separate storm sewer system or a non-stormwater discharge to the MS4, he or she may give notice to the owner or occupant of the adjacent property to remove such oil, earth, debris, grass, weeds, dead trees, tin cans, rubbish, refuse, waste or other material, in any manner that he or she may reasonably provide. The recipient of such notice shall undertake the activities as described in the notice.

E. Penalties. Any person who violates any provision of this chapter or fails to comply with any of the requirements of this chapter shall be guilty of a misdemeanor. Each and every day, or any part thereof, during which any such violation is committed, continued or allowed, shall constitute a separate offense.

F. Permit Revocation. To the extent the City makes a provision of this chapter or any identified BMP a condition of approval to the issuance of a permit or license, any person in violation of such condition is subject to the permit revocation procedures set forth in this code.

G. Remedies. Remedies under this chapter are in addition to and do not supersede or limit any and all other remedies, civil or criminal. The remedies provided for herein shall be cumulative and not exclusive.

The provisions of this chapter shall not be construed or operate to deprive any property owner of substantially all of the market value of such owner’s property or otherwise constitute an unconstitutional taking without compensation.

Fees to be charged for plan checking, monitoring and any other activities carried out by the City under this chapter shall be set by resolution of the City Council.

A. Objective. The provisions of this section contain requirements for construction activities and facility operations of development and redevelopment projects to comply with the current "Municipal NPDES Permit," lessen the water quality impacts of development by using smart growth practices, and integrate LID design principles to mimic predevelopment hydrology through infiltration, evapotranspiration and rainfall harvest and use. LID shall be inclusive of SUSMP requirements.

B. Scope. This section contains requirements for stormwater pollution control measures in development and redevelopment projects and authorizes the City of Walnut to further define and adopt stormwater pollution control measures, develop LID principles and requirements, including, but not limited to, the objectives and specifications for integration of LID strategies, grant waivers from the requirements of the Standard Urban Stormwater Mitigation Plan, and collect funds for projects that are granted waivers. Except as otherwise provided herein, the City of Walnut shall administer, implement and enforce the provisions of this section.

C. Applicability. The following development and redevelopment projects, termed "planning priority projects," shall comply with the requirements of this section.

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

2. Industrial parks 10,000 square feet or more of surface area.

3. Commercial malls 10,000 square feet or more of surface area.

4. Retail gasoline outlets with 5,000 square feet or more of surface area.

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

6. Parking lots with 5,000 square feet or more of impervious surface area, or with 25 or more parking spaces.

7. Streets and roads construction of 10,000 square feet or more of impervious surface area.

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

9. Projects located in or directly adjacent to, or discharging directly to an Environmentally Sensitive Area (ESA), where the development will:

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

b. Create 2,500 square feet or more of impervious surface area.

10. Single-family hillside homes.

11. Redevelopment Projects.

a. Land disturbing activity that results in the creation or addition or replacement of 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 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 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 10,000 square feet of impervious surface area.

D. Effective Date. The planning and land development requirements contained in Section 7 of Order No. R4-2012-0175 shall become effective 90 days from the adoption of the Order (February 6, 2013). This includes planning priority projects that are discretionary permit projects or project phases that have not been deemed complete for processing, or discretionary permit projects without vesting tentative maps that have not requested and received an extension of previously granted approvals within 90 days of adoption of the Order. Projects that have been deemed complete within 90 days of adoption of the Order are not subject to the requirements of Section 7.

E. Stormwater Pollution Control 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.

1. A new single-family hillside home development 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 10,000 square feet or more of impervious surface shall follow USEPA guidance regarding Managing Wet Weather with Green Infrastructure: Green Streets (December 2008 EPA-833-F-08-009) to the maximum extent practicable.

3. The remainder of planning priority projects shall prepare a LID plan to comply with the following:

a. Retain stormwater runoff on-site for the Stormwater Quality Design Volume (SWQDv) defined as the runoff from:

i. The 85th percentile 24-hour runoff event as determined from the Los Angeles County 85th percentile precipitation isohyetal map; or

ii. The volume of runoff produced from a 0.75 inch, 24-hour rain event, whichever is greater.

b. Minimize hydromodification impacts to natural drainage systems as defined in the Municipal NPDES Permit. Hydromodification requirements are further specified in County of Los Angeles Department of Public Works Storm Water Best Management Practices Design and Maintenance Manual.

c. When, as determined by the City of Walnut, 100% on-site retention of the SWQDv is technically infeasible, partially or fully, the infeasibility shall be demonstrated in the submitted LID plan. The technical infeasibility may result from conditions that may include, but are not limited to:

i. The infiltration rate of saturated in-situ soils is less than 0.3 inch 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;

ii. Locations where seasonal high groundwater is within five to 10 feet of surface grade;

iii. Locations within 100 feet of a groundwater well used for drinking water;

iv. Brownfield development sites or other locations where pollutant mobilization is a documented concern;

v. Locations with potential geotechnical hazards;

vi. 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 times the portion of the remaining SWQDv that is not reliably retained on-site. Biofiltration BMPs must adhere to the design specifications provided in the Municipal NPDES Permit.

Additional alternative compliance options such as off-site infiltration may be available to the project site. The project site should contact the City of Walnut to determine eligibility. Alternative compliance options are further specified in County of Los Angeles Department of Public Works Storm Water Best Management Practices Design and Maintenance Manual.

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:

i. 0.2 inches per hour; or

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

f. A multi-phased project may comply with the standards and requirements of this section for all of its phases by: (i) designing a system acceptable to the City of Walnut to satisfy these standards and requirements for the entire site during the first phase; and (ii) implementing these standards and requirements for each phase of development or redevelopment of the site during the first phase or prior to commencement of construction of a later phase, to the extent necessary to treat the stormwater from such later phase. For purposes of this section, "multi-phased project" shall mean any planning priority project implemented over more than one phase and the site of a multi-phased project shall include any land and water area designed and used to store, treat or manage stormwater runoff in connection with the development or redevelopment, including any tracts, lots, or parcels of real property, whether developed or not, associated with, functionally connected to, or under common ownership or control with such development or redevelopment.

The enforcement provisions of Walnut City Code Sections 5.08.100 through 5.08.120 shall apply to Sections 5.08.130 and 5.08.140.