§ 12.84

The purposes of this chapter are as follows:

A.

Lessen the adverse impacts of stormwater and non-stormwater runoff from development on natural drainage systems, receiving waters and other water bodies.

B.

Minimize pollutant loadings from impervious surfaces by requiring development projects to incorporate properly designed, technically appropriate BMPs and other Low Impact Development strategies.

C.

Minimize erosion and other hydrologic impacts on natural drainage systems by requiring development projects to incorporate properly designed, technically appropriate hydromodification control development principles and technologies.

D.

The provisions in this Chapter 12.84 shall be construed to augment any county, state, or federal ordinance, statute, regulation, or other requirement governing the same or related matter, and where a conflict exists between a provision in this Chapter 12.84 and such other ordinance, statute, regulation, or requirement, the stricter provision shall apply to the extent permitted by law.

(Ord. 2025-0058 § 1, 2025; Ord. 2013-0044 § 1, 2013; Ord. 2008-0063 § 1 (part), 2008.)

The following terms, which may appear either as upper case or lower case terms throughout this chapter, shall be defined as follows:

A.

"Basin Plan" means the Water Quality Control Plan, Los Angeles Region, Basin Plan for Coastal Watersheds of Los Angeles and Ventura Counties, adopted by the Regional Water Board on June 13, 1994 and subsequent amendments.

B.

"Beneficial Use" means the existing or potential use of receiving waters as designated by the Los Angeles or Lahontan Regional Water Quality Control Boards in their respective basin plans for the County.

C.

"Best Management Practices (BMPs)" are practices or physical devices or systems designed to prevent or reduce pollutant loading from stormwater or non-stormwater discharges to receiving waters.

D.

"Biofiltration" means a Low Impact Development BMP that reduces stormwater pollutant discharges by using methods, including, but not limited to, intercepting rainfall on vegetative canopy, incidental infiltration, evapotranspiration, and filtration. It is a system designed to facilitate incidental infiltration or achieve the equivalent pollutant reduction as biofiltration BMPs with an underdrain. Biofiltration BMPs include bioretention systems with an underdrain and bioswales.

E.

"Bioretention" means a Low Impact Development BMP that reduces stormwater runoff by intercepting rainfall on vegetative canopy and through evapotranspiration and infiltration. Bioretention systems typically include a minimum 2-foot top layer of a specified soil and compost mixture underlain by a gravel-filled

temporary storage pit dug into the in-situ soil. A bioretention BMP may be designed with an overflow drain but may not include an underdrain.

F.

"Capital Flood" means the runoff produced by a fifty (50)-year frequency design storm falling on a saturated watershed (soil moisture at field capacity). A fifty (50)-year frequency design storm has a probability of 1/50 of being equaled or exceeded in any year.

G.

"County" means the County of Los Angeles.

H.

"Development" means projects requiring discretionary or non-discretionary land use or construction approval from the County that results in the creation, addition, modification, or replacement of impervious surface area, which replacement is not part of routine maintenance activities. Development includes, but is not limited to, land subdivisions; the construction, installation, addition, or replacement of a building or structure; expansion of a building footprint; and land-disturbing activities related to structural or impervious surfaces or grading for future construction. Development does not include: 1) routine maintenance of original lines and grades and/or hydraulic capacity; or 2) emergency redevelopment activity required to protect public health and safety.

I.

"Director" means the Director of Public Works.

J.

"Effective impervious area" means the portion of the surface area that is hydrologically connected to a drainage system via a hardened conveyance or impervious surface without any intervening pervious area to mitigate the runoff volume.

K.

"Flow-through treatment BMP" 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.

L.

"Hydromodification" means the alteration of a natural drainage system through a change in the system's flow characteristics, which results in hydrogeomorphic changes.

M.

"Impervious area" means a hard surface area that can impede the natural infiltration of runoff.

N.

"Low Impact Development (LID)" means a stormwater management approach to reduce runoff and pollutant loadings by utilizing land management strategies and BMPs.

O.

"Natural Drainage System" means a drainage system that has not been modified using engineering controls (e.g., channelized or armored).

P.

"Non-Priority Project" means any development project that is not included in subsection A of Section 12.84.430.

Q.

"Non-Stormwater" means any discharge into the municipal separate storm sewer system (MS4) that is not composed entirely of stormwater.

R.

"Pollutants of Concern" means chemical, physical, or biological components of stormwater that impair the beneficial uses of receiving waters, including those defined in the Federal Clean Water Act section 502(6) (33 United States Code section 1362(6)), and incorporated by reference into California Water Code section 13373.

S.

"Priority Development Project" means any new development and/or redevelopment project described in subsection A of Section 12.84.430.

T.

"Public Works" means the Los Angeles County Department of Public Works.

U.

"Receiving Water" means a "water of the United States" into which waste and/or pollutants are or may be discharged.

V.

"Redevelopment" means projects that expand a building footprint, add or replace a structure, or replace impervious surface area that is not part of a routine maintenance activity and land disturbing activities related to structural or impervious surfaces. It does not include routine maintenance to maintain original line and grade, hydraulic capacity, or original purpose of the facility, nor does it include emergency construction activities required to immediately protect public health and safety.

W.

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

X.

"Routine maintenance" means projects that include, but are not limited to, activities 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) Perform road shoulder work, regrading dirt or gravel roadways and shoulders, and performing ditch cleanouts (activities that do not change the original grade after road work); (4) Update existing lines and facilities to comply with applicable codes, standards, and regulations regardless if such projects result in increased capacity; and (5) Repair leaks. Routine maintenance does not include construction of new lines or facilities resulting from compliance with applicable codes, standards, and regulations.

Y.

"Runoff" means any runoff, including stormwater and non-stormwater, from a drainage area that reaches a receiving water body.

Z.

"Standard Industrial Classification (SIC)" means a classification pursuant to the current edition of the Standard Industrial Classification Manual issued by the Executive Office of the President of the United States, Office of Management and Budget, and as the same may be periodically revised.

AA.

"Stormwater" means runoff that occurs as the result of rainfall, snow melt, and surface runoff and drainage related to precipitation events (pursuant to 40 CFR § 122.26(b)(13); 55 Fed. Reg. 47990, 47995 (Nov. 16, 1990)).

BB.

"Stormwater Quality Design Volume (SWQDv)" means the greater of the following: (1) the runoff from the 0.75 inch, 24-hour rain event; or (2) the runoff from the 85th percentile, 24-hour rain event.

(Ord. 2025-0058 § 2, 2025; Ord. 2013-0044 § 2, 2013; Ord. 2008-0063 § 1 (part), 2008.)

12.84.430 - Applicability.

A.

Priority Development Projects. The following types of projects shall comply with the provisions of Subsection C of Section 12.84.440, below:

1.

All new development projects involving one (1) acre or greater of disturbed area and adding more than ten thousand (10,000) square feet of impervious surface area (collectively over the entire project site);

New industrial parks with ten thousand (10,000) square feet or more of surface area;

3.

New commercial malls with ten thousand (10,000) square feet or more of surface area;

4.

New development and redevelopment projects that create and/or replace five thousand (5,000) square feet or more of impervious surface (collectively over the entire project site) and support one or more of the following uses:

a.

Restaurants (SIC 5812);

b.

Parking lots;

c.

Automotive service facilities (SIC 5013, 5014, 5511, 5541, 7532-7534, and 7536-7539); or

d.

Retail gasoline outlets.

5.

New development and redevelopment projects that create and/or replace two thousand five hundred (2,500) square feet or more of impervious area; discharge stormwater that is likely to impact a sensitive biological species or habitat; and are located in or directly adjacent to or are discharging directly to (1) a Significant Ecological Area (SEA), as defined in Title 22, Division 2, Chapter 22.14.190, or (2) an Area of Special Biological Significance (ASBS), as defined by the State; and

6.

All redevelopment projects that create and/or replace five thousand (5,000) square feet or more of impervious surface (collectively over the entire project site) on any of the following:

a.

Existing sites of ten thousand (10,000) square feet or more of impervious surface area;

b.

Industrial parks of ten thousand (10,000) square feet or more of surface area; or

c.

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

B.

Considerations for Redevelopment Projects.

1.

For all redevelopment projects, which are Priority Development Projects, as defined in subsection A of Section 12.84.430, above, where fifty percent (50%) or more of impervious surfaces of a previously developed site is proposed to be altered, the entire development site (i.e., both the existing development and the proposed alteration) shall comply with the provisions of subsection C of Section 12.84.440, below.

2.

For all redevelopment projects that are Priority Development Projects, as defined in subsection A of Section 12.84.430, above, where less than fifty percent (50%) of impervious surfaces of a previously developed site is proposed to be altered, only the proposed alteration shall comply with the provisions of subsection C of Section 12.84.440, and not the entire development site.

3.

Redevelopment does not include routine maintenance projects.

C.

Non-Priority Projects. Any new development and redevelopment project that is not included in subsection A shall comply with the provisions of subsection D of Section 12.84.440, as follows:

1.

Where the new development or redevelopment project involves a previously undeveloped site or results in an addition or alteration of at least fifty percent (50%) of the impervious surfaces of an existing developed site, the entire site shall be brought into compliance with the provisions of subsection D of Section 12.84.440; and

2.

Where the new development and redevelopment project results in an addition or alteration of less than fifty percent (50%) of the impervious surfaces of an existing developed site, only such incremental development shall comply with the provisions of subsection D of Section 12.84.440.

D.

Street and road construction of ten thousand (10,000) square feet or more of impervious surface area 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. This subsection applies to standalone streets, roads, highways, and freeway projects, and also applies to streets within larger projects. Temporary access roads are not subject to this requirement. Projects under this category are exempt from the Provisions of Section 12.84.440.

(Ord. 2025-0058 § 3, 2025; Ord. 2022-0029 § 7, 2022; Ord. 2013-0044 § 3, 2013; Ord. 2008-0063 § 1 (part), 2008.)

12.84.440 - Low Impact Development Standards.

A.

The LID standards of this chapter:

1.

Mimic undeveloped stormwater runoff rates and volumes in any storm event up to and including the Capital Flood;

2.

Prevent pollutants of concern from leaving the development site in stormwater runoff through retention or treatment of the SWQDv or applicable flow rate to the maximum extent practicable; and

3.

Minimize hydromodification impacts to natural drainage systems.

B.

The Director shall prepare, maintain, and update, as deemed necessary and appropriate, a manual (LID Standards Manual), which shall include runoff quantity and quality control development principles and technologies for achieving compliance with the provisions of this section. The LID Standards Manual shall also include technical feasibility and implementation parameters, as well as other rules, requirements, and procedures as the Director deems necessary, for implementing the provisions of this Chapter 12.84.

C.

Priority Development Projects. To meet the standards described in subsection A of this section, new development and redevelopment projects described in subsection A of Section 12.84.430 shall comply with the following requirements:

1.

The project shall retain one hundred percent (100%) of the SWQDv on-site, through infiltration, bioretention, rainfall harvest and use, or a combination thereof;

2.

If the Director determines that it would be technically infeasible to retain one hundred percent (100%) of the SWQDv on-site, the project shall comply with one of the following alternative compliance measures:

a.

The project shall provide for on-site biofiltration of one and one-half (1.5) times the portion of the SWQDv that is not retained on-site;

b.

The project shall include infiltration or bioretention BMPs to intercept the portion of the SWQDv that is not retained on-site at an offsite location, as approved by the Director. The project shall also provide for treatment of the portion of the SWQDv discharged from the project site in accordance with the LID Standards Manual, as approved by the Director;

c.

The project shall provide for the replenishment of groundwater supplies that have a designated beneficial use in the Basin Plan;

(i)

Groundwater replenishment projects shall include infiltration, groundwater replenishment, or bioretention BMPs to intercept a volume of stormwater runoff equal to the SWQDv at an offsite location, as approved by the Director;

(ii)

Where off-site groundwater replenishment projects are implemented, treatment must be provided for the SWQDv discharged from the new development or redevelopment project site in accordance with the LID Standards Manual, as approved by the Director;

d.

The project shall include infiltration, bioretention, or rainfall harvest and use and/or biofiltration BMPs to retrofit an existing development, with similar land uses as the project, to intercept the portion of the SWQDv that is not retained on-site. The project shall also provide for treatment of the SWQDv discharged from the project site in accordance with the LID Standards Manual, as approved by the Director; or

e.

The County, independently or in conjunction with one (1) or more cities, may apply to the Regional Water Board for approval of a regional or sub-regional stormwater mitigation program to substitute in part or wholly for the provisions of this chapter for the area covered by the regional or sub-regional stormwater mitigation program. If the Regional Water Board approves the program, the provisions of the program shall apply in lieu of any conflicting provisions of this chapter. If the new development or redevelopment project is located within the same watershed of an existing or proposed regional Public Works stormwater project, it may opt to pay a fee-in-lieu of the above-mentioned option as defined by and meeting the terms of the Public Works Fee-In-Lieu Program described in Section 12.84.470. Implementation of an alternative, fee-inlieu compliance program shall meet all the following requirements:

(i)

Retains the runoff from the 85th percentile, 24-hour rain event, or the 0.75-inch, 24-hour rain event, whichever is greater;

(ii)

Results in improved stormwater quality;

(iii)

Meets the hydromodification management requirements in the MS4 Permit, if applicable;

(iv)

Is fiscally sustainable and has secure funding; and

(v)

Is completed in five (5) years, including the construction and start-up of treatment facilities.

D.

Non-Priority Projects. To meet the standards described in subsection A of this section, any new development or redevelopment project described in subsection C of Section 12.84.430, above, shall comply with the following requirements:

1.

A new development or redevelopment project consisting of four (4) or fewer residential units shall implement at least two (2) LID BMP alternatives listed in the LID Standards Manual, which alternatives include, but are not limited to, disconnecting impervious surfaces, using porous pavement, downspout routing, a dry well, landscaping and irrigation requirements, and a green roof;

2.

A new development or redevelopment project consisting of five (5) or more residential units, or a nonresidential new development or redevelopment project, shall comply with the following requirements:

a.

The required volume from each lot upon which such new development or redevelopment is occurring shall be infiltrated at the lot level, or in the alternative, the required volume from the entire development site, including streets and public right-of-way, shall be infiltrated in sub-regional facilities. The tributary area of a sub-regional facility shall be limited to five (5) acres but may be exceeded with approval of the Director. When the Director determines that infiltration of all required volume is not technically feasible, on-site storage, reuse, or other water conservation uses of the required volume shall be implemented as authorized by the Director in accordance with the requirements and provisions specified in the LID Standards Manual. Alternatively, projects found within the same sub watershed (Hydrologic Unit Code 12) of an existing or

proposed regional Public Works stormwater project may opt to pay a fee-in-lieu of the above-mentioned options as defined by and meeting the terms of the Alternative Compliance Program described in Section 12.84.470; and

b.

The runoff from the new development or redevelopment project must be treated to the satisfaction of the Director before discharge.

(Ord. 2025-0058 § 4, 2025; Ord. 2013-0044 § 4, 2013; Ord. 2008-0063 § 1 (part), 2008.)

A.

Exemptions. The Director may grant exemptions from the provisions of this Section 12.84.445 for the following types of development projects where the Director determines that downstream channel conditions and proposed discharge hydrology indicate that adverse hydromodification effects to beneficial uses of natural drainage systems are unlikely:

1.

The replacement, maintenance or repair of existing, publicly-maintained flood control facilities, storm drains, or transportation networks;

2.

Redevelopment of a previously developed site in an urbanized area that does not increase the effective impervious area or decrease the infiltration capacity of pervious areas compared to the pre-project conditions;

3.

Projects that have any increased discharge directly or through a storm drain to a sump, lake, area under tidal influence, into a waterway that has an estimated hundred (100)-year peak flow of twenty-five thousand (25,000) cubic feet per second (c.f.s.) or more, or other receiving water that is not susceptible to hydromodification impacts;

4.

Projects that discharge directly or through a storm drain into concrete or other engineered channels (e.g., channelized or armored with rip rap, shotcrete, etc.), which, in turn, discharge into receiving water that is not susceptible to hydromodification impacts; or

5.

Single family homes that incorporate LID BMPs in accordance with the LID Standards Manual.

B.

The LID Standards Manual shall include hydromodification control development principles and technologies for achieving compliance with the provisions of this Section 12.84.445 as well as other rules, requirements and procedures as the Director deems necessary, for implementing the provisions of this section.

C.

Unless excluded by subsection A, above, or meeting the requirements of subsection D, below, new development and redevelopment projects must fully mitigate off-site drainage impacts caused by

hydromodification and changes in flow rate, velocity, volume, and duration of flow, as determined by the Director, in accordance with the requirements and provisions specified in the LID Standards Manual.

1.

Sediment transport analysis shall be required when the project is tributary to any natural drainage system with a Capital Flood flow rate greater than five thousand (5,000) c.f.s.

D.

If the Director determines that it would be infeasible for a development project to comply with the provisions of subsection C of this section, and the project disturbs an area greater than one (1) acre, but less than fifty (50) acres, written consent to the unmitigated impacts shall be obtained from the owner of every impacted downstream property. In addition, the development project shall comply with one of the following alternative requirements:

1.

The project shall retain on-site, one hundred percent (100%) of the stormwater runoff volume from the ninety-fifth (95th) percentile, twenty-four (24)-hour rainfall event, through infiltration, bioretention, and/or harvest and use;

2.

The runoff flow rate, volume, velocity, and duration for the project's post-development condition shall not exceed the pre-development condition for the two (2)-year, twenty-four (24)-hour rainfall event; or

3.

The Erosion Potential (Ep) in the receiving water shall approximate one (1), as demonstrated by a hydromodification analysis study approved by the Director.

E.

If the Director determines that it would be infeasible for a development project to comply with the provisions of subsection C of this section, and the project disturbs an area fifty (50) acres or more, written consent to the unmitigated impacts shall be obtained from the owner of every impacted downstream property. In addition, the development project shall comply with one of the following alternative requirements:

1.

The project shall infiltrate on-site at least the runoff from a two (2)-year, twenty-four (24)-hour rainfall event;

2.

The runoff flow rate, volume, velocity, and duration for the project's post-development condition shall not exceed the pre-development condition for the two (2)-year, twenty-four (24)-hour rainfall events; or

The Ep in the receiving water shall approximate one (1), as demonstrated by a hydromodification analysis study approved by the Director.

(Ord. 2025-0058 § 5, 2025; Ord. 2013-0044 § 5, 2013.)

A.

Compliance with the LID and hydromodification control standards of this Chapter 12.84 shall be shown through an LID plan review described in subsection B, below.

B.

The applicant for any new development or redevelopment project shall submit an LID plan to the Director for review and approval that provides a comprehensive, technical discussion of how the development project will comply with this Chapter 12.84 and the applicable provisions specified in the LID Standards Manual. A deposit and fee to recover the costs associated with LID plan review shall be required. The time for obtaining LID plan approval shall be as follows:

1.

For subdivisions, the LID plan shall be approved prior to the tentative map approval;

2.

For any new development and redevelopment project requiring a conditional use permit (CUP) or other discretionary entitlement required under Title 22 of the Los Angeles County Code, the LID plan shall be approved prior to the issuance of any such CUP or other discretionary entitlement; and

3.

For all other new development and redevelopment projects, the LID plan shall be approved prior to issuance of a grading permit for such new development or redevelopment project, or when no grading permit is required, prior to the issuance of a building permit for such new development or redevelopment project, or when no grading or building permit is required, prior to the commencement of any development activity or as otherwise indicated in the non-discretionary land use approval.

(Ord. 2025-0058 § 6, 2025; Ord. 2013-0044 § 6, 2013; Ord. 2008-0063 § 1 (part), 2008.)

Compliance with this Chapter 12.84 shall also require new development and redevelopment projects to satisfy the following:

A.

All grading and/or site drainage plans for the new development or redevelopment shall incorporate the features of the approved LID plan described in subsection B of Section 12.84.450;

B.

Ongoing Maintenance.

1.

The development project's LID and hydromodification control features shall be maintained and shall remain operable at all times and shall not be removed from the project site unless and until such features have been replaced with other LID or hydromodification control features in accordance with this Chapter 12.84.

2.

Unless excused by the Director in his or her discretion, the owner of the subject new development or redevelopment project site shall prepare and obtain the Director's approval of an operation and maintenance plan and monitoring plan for all LID practices and LID and hydromodification control features incorporated into the project.

3.

The owner of the subject development project site shall record a covenant or agreement, approved as to form and content by the Director, in the office of the Los Angeles County Registrar-Recorder/County Clerk indicating that the owner of the subject development project site is aware of and agrees to the requirements in this subsection B. The covenant or agreement shall also include a diagram of the development project site indicating the location and type of each LID and hydromodification control feature incorporated into the development project. The time to record such covenant or agreement shall be as follows:

a.

For any subdivision, prior to final map approval; and

b.

For any other development project, prior to issuance of a grading plan approval for the development project, and when no grading plan approval is required, prior to the issuance of building plan approval for the development project.

(Ord. 2025-0058 § 7, 2025; Ord. 2013-0044 § 7, 2013; Ord. 2008-0063 § 1 (part), 2008.)

12.84.470 - Fee-in-Lieu of Alternative Compliance.

A.

The Director is granted the authority to establish, maintain, and update an alternative compliance program for the payment of a fee in lieu of complying with the LID standards of subsection A of Section 12.84.440. The alternative compliance program shall be consistent with the MS4 Permit and the Los Angeles County Code.

The alternative compliance program shall establish an in-lieu fee available to eligible new development and redevelopment projects.

2.

The in-lieu fees collected by the County shall be used for the construction and maintenance of regional stormwater projects and the operation of the alternative compliance program.

3.

The alternative compliance program shall establish a fee schedule, eligibility requirements, and standards for participation in the program pursuant to the MS4 Permit, which may be updated from time to time.

4.

The alternative compliance program shall establish an accounting system to track and monitor the implementation of the alternative compliance program.

(Ord. 2025-0058 § 8, 2025.)

Chapter 12.85 - CARRYOUT BAGS