A. Objective. The provisions of this section establish requirements for construction activities and facility operations of development and redevelopment projects to comply with the MS4 permit, to lessen the water quality impacts of development by using smart growth practices, and to integrate LID practices and standards for storm water pollution mitigation through means of infiltration, evapotranspiration, biofiltration, and rainfall harvest and use. LID shall be inclusive of new development and/or redevelopment requirements.
B. Scope. This section contains requirements for storm water pollution control measures in development and redevelopment projects, and authorizes the City to further define and adopt storm water pollution control measures, and to develop LID principles and requirements, including but not limited to the objectives and specifications for integration of LID strategies. Except as otherwise provided herein, the City shall administer, implement and enforce the provisions of this section.
C. Applicability. This section applies to the following projects:
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 with 10,000 square feet or more of surface area.
3. Commercial malls with 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 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 with 10,000 square feet or more of impervious surface area. Street and road construction applies to standalone streets, roads, highways, and freeway projects, and also applies to streets within larger projects.
8. Automotive service facilities with 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, where the development will:
a. Discharge storm water 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 properties.
11. Redevelopment projects.
a. Construction 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 of one of the projects identified in this subsection.
b. Where redevelopment results in an alteration to more than fifty percent of impervious surfaces of a previously existing development, and the existing development was not subject to post-construction storm water quality control requirements, the entire project must be mitigated.
c. Where redevelopment results in an alteration to less than fifty percent of impervious surfaces of a previously existing development, and the existing development was not subject to post-construction storm water 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. Requirements. The site for every project identified in § 12.16.114(C) 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. The project applicant shall prepare a LID plan which implements set LID standards and practices for storm water pollution mitigation and provides documentation to demonstrate compliance with the MS4 Permit on the plans and permit application submitted to the city. Such a LID plan shall comply with the following:
1. A new single-family hillside property development shall prepare a LID plan to 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 US EPA guidance regarding managing wet weather with the city's most current Green Streets Manual to the maximum extent practicable.
3. The remainder of Projects identified in § 12.16.114(C) shall prepare a LID plan to comply with the following:
a. Retain storm water runoff onsite for the storm water 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.
E. Technical Infeasibility.
1. Full or partial waivers of compliance with the requirements of this section may be obtained where the project applicant shows by application in writing that the incorporation and design elements that address the objectives set forth in this section are impracticable and are non-economical or otherwise physically impossible due to the site characteristics or other characteristics unique to the project. Any waiver request shall be in writing to the director and may only be approved where permitted in accordance with the terms of the MS4 permit.
2. To demonstrate technical infeasibility, the project applicant must demonstrate that the project cannot reliably retain 100 percent 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:
a. 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 onsite.
b. Locations where seasonal high groundwater is within five to ten feet of surface grade;
c. Locations within 100 feet of a groundwater well used for drinking water;
d. Brownfield development sites or other locations where pollutant mobilization is a documented concern;
e. Locations with potential geotechnical hazards; and
f. Smart growth and infill or redevelopment locations where the density and/or nature of the project would create significant difficulty for compliance with the onsite volume retention requirement.
3. If partial or complete onsite retention is technically infeasible, the project site may biofiltrate 1.5 times the portion of the remaining SWQDv that is not reliably retained onsite. Biofiltration BMPs must adhere to the design specifications provided in the MS4 permit.
4. Additional alternative compliance options such as offsite infiltration and groundwater replenishment projects may be available to the project site. The applicant should contact the director to determine eligibility.
5. The remaining SWQDv that cannot be retained or biofiltered onsite must be treated onsite to reduce pollutant loading. BMPs must be selected and designed to meet pollutant-specific benchmarks as required by the MS4 permit. Flow-through BMPs may be used to treat the remaining SWQDv and must be sized based on a rainfall intensity of:
a. 0.2 inches per hour, or
b. The one year, one-hour rainfall intensity as determined from the most recent Los Angeles County isohyetal map, whichever is greater.
F. Exemptions from LID requirements. The provisions of this section do not apply to any of the following:
1. A development involving only emergency construction activity required to immediately protect public health and safety;
2. Infrastructure projects within the public right-of-way;
3. A development or redevelopment involving only activity related to gas, water, cable, or electricity services on private property;
4. A development involving only resurfacing and/or re-striping of permitted parking lots, where the original line and grade, hydraulic capacity, and original purpose of the facility is maintained;
5. A project involving only exterior movie or television production sets, or facades on an existing developed site;
6. A project not requiring a City building, grading, demolition or other permit for construction activity.
G. Any development that is exempted from LID requirements under division F. of this section has the option to voluntarily opt in and incorporate into the project the LID requirements set forth herein.
H. City review and approval.
1. Prior to the issuance of a permit for a new development or redevelopment project, the City shall evaluate the proposed project using the MS4 permit, and erosion and grading requirements of the City building official or director to determine (i) its potential to generate the flow of pollutants into the MS4 after construction; and (ii) how well the LID plan for the proposed project meets the goals of this chapter. Each plan will be evaluated on its own merits according to the particular characteristics of the project and the site to be developed. Based upon the review, the City may impose conditions upon the issuance of the building permit, in addition to any required by the State construction general permit for the project, in order to minimize the flow of pollutants into the MS4.
2. The director shall approve or disapprove of the LID plan within thirty (30) calendar days of submittal, or within thirty (30) days of approval of the development project by the planning commission, where planning commission approval is required. If the LID plan is disapproved, the reasons for disapproval shall be given in writing to the applicant. Any LID plan disapproved may be revised by the applicant and resubmitted for approval. A resubmitted plan will be approved or disapproved within thirty (30) days of submittal. No building or grading permit shall be issued until a LID plan has been approved by the director.
3. If no building permit has been issued or no construction has begun on a project within a period of one hundred eighty (180) days of approval of a LID plan, the LID plan for that project shall expire. The director may extend the time by written extension for action by the applicant for a period not to exceed one hundred eighty (180) days upon written request by the applicant showing that circumstances beyond the control of the applicant prevented the construction from commencing. In order to renew the LID plan, the applicant shall resubmit all necessary forms and other data and pay a new LID plan check fee.
I. Transfer of properties subject to the requirements of this section.
1. The transfer or lease of a property subject to maintenance requirements for LID BMPs shall include conditions requiring the transferee and its successors and assigns to either: (a) assume responsibility for maintenance of any existing LID BMP, or (b) replace an existing LID BMP with new control measures or BMPs meeting the then current standards of the City and MS4 permit. 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 LID BMPs at least once a year and retain proof of inspection.
2. For residential properties where the LID 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). Printed educational materials will be required to accompany the first deed transfer to highlight the existence of the requirement and to provide information on what LID BMPs are present, signs that maintenance is needed, and how the necessary maintenance can be performed. The transfer of this information shall also be required with any subsequent sale of the property.
3. If LID BMPs are located within an area proposed for dedication to a public agency, they will be the responsibility of the developer until the dedication is accepted.
(Ord. 2013-11-1462 § 1; Ord. 2013-06-1455 § 4)