Cudahy City Zoning Code
20.68 Low
Impact Development Measures
20.68.010 Purpose and intent.
A. Purpose. The provisions of this chapter establish requirements for construction activities and facility operations of development and redevelopment projects to comply with the current municipal National Pollutant Discharge Elimination System (NPDES) permit, lessen the water quality impacts of development by using smart growth practices, and integrate Low Impact Development (LID) practices and standards for stormwater 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 chapter 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, to grant waivers from the LID requirements, and to collect funds for projects that are granted waivers. Except as otherwise provided herein, the city shall administer, implement, and enforce the provisions of this chapter. Guidance documents supporting implementation of requirements in this chapter are hereby incorporated by reference, including Standard Urban Storm Water Mitigation Plan and LID guidelines (city of Cudahy Low Impact Development (LID) guidelines) available from the city clerk. Definitions in Chapter 20.88 CMC shall apply. (Ord. 690 § 4 (Exh. A), 2018).
20.68.020 Applicability.
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), are:
A. Greater than One Acre. All development projects equal to one acre or greater of disturbed area that add more than 10,000 square feet of impervious surface area.
B. Industrial Parks. Industrial parks 10,000 square feet or more of surface area.
C. Commercial Malls. Commercial malls 10,000 square feet or more of surface area.
D. Retail Gasoline Outlets. Retail gasoline outlets with 5,000 square feet or more of surface area.
E. Restaurants. Restaurants (Standard Industrial Classification (SIC) of 5812) with 5,000 square feet or more of surface area.
F. Parking Lots. Parking lots with 5,000 square feet or more of impervious surface area or with 25 or more parking spaces.
G. Streets and Roads. Street and road construction of 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. Automotive service facilities (SIC of 5013, 5014, 5511, 5541, 7532 through 7534, and 7536 through 7539) with 5,000 square feet or more of surface area.
I. Sensitive Areas. Projects located in or directly adjacent to, or discharging directly to, an environmentally sensitive area (ESA), where the development will:
1. Discharge stormwater runoff that is likely to impact a sensitive biological species or habitat; and
2. Create 2,500 square feet or more of impervious surface area.
J. Redevelopment Projects.
1. 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 on planning priority project categories.
2. Where redevelopment results in an alteration to more than 50 percent 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.
3. Where redevelopment results in an alteration of less than 50 percent 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.
4. 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.
5. Existing single-family dwellings and accessory structures are exempt from the redevelopment requirements unless such projects create, add, or replace 10,000 square feet of impervious surface area.
K. Other Projects. Any other project as deemed appropriate by the director of community development based on finding that characteristics of either the project or the site may result in environmental effects that can be mitigated by application of this chapter. (Ord. 690 § 4 (Exh. A), 2018).
20.68.030 Effective date.
The planning and land development requirements contained in this chapter shall become effective 30 days from the adoption of the ordinance codified in this zoning code. 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 ordinance codified in this zoning code. Project applications that have been deemed complete within 90 days of adoption of the ordinance codified in this zoning code are not subject to the requirements of this chapter. (Ord. 690 § 4 (Exh. A), 2018).
20.68.040 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.
A. Street and Road Projects. Street and road construction projects with construction costs greater than $500,000 and add at least 10,000 square feet of impervious surface shall follow the city of Cudahy’s green streets policy manual (available from the city clerk).
B. Planning Priority Projects. The remainder of planning priority projects shall prepare a LID plan to comply with the following:
1. Retain stormwater runoff on site for the stormwater quality design volume (SWQDV) defined as the runoff from:
a. The eighty-fifth percentile 24-hour runoff event as determined from the Los Angeles County eighty-fifth percentile precipitation isohyetal map; or
b. The volume of runoff produced from a three-quarter-inch, 24-hour rain event, whichever is greater.
2. Minimize hydromodification impacts to natural drainage systems as defined in the municipal NPDES permit.
3. 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 three-tenths 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 best management practices (BMPs) in retaining the SWQDV on site.
b. Locations where seasonal high groundwater is within five to 10 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.
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 on-site volume retention requirement.
4. 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.
a. 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 approving agency to determine eligibility.
5. 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:
a. One-fifth inch 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. (Ord. 690 § 4 (Exh. A), 2018).
20.68.050 Additional requirements.
The site for projects not classified with general applicability listed in CMC 20.68.030 but resulting in the creation, addition, or replacement of 500 square feet or more of impervious surface area shall be designed to control pollutants, pollutant loads, and runoff volume per the city of Cudahy LID guidelines (available from the city clerk). (Ord. 690 § 4 (Exh. A), 2018).