9.11.110 Stormwater Control Measures for New Development and Redevelopment Projects.
A. Pursuant to E.12 of the Phase II Stormwater Permit, the City has authority to regulate most new development and redevelopment projects that create and/or replace a minimum of two thousand five hundred (2,500) square feet of impervious surface. The selection and design of such controls shall be in accordance with criteria established or recommended by the City, federal, state, and local agencies, and the BASMAA Post-Construction Manual.
B. Projects that create and/or replace between two thousand five hundred (2,500) square feet and five thousand (5,000) square feet of impervious surface, including detached single-family homes that create and/or replace two thousand five hundred (2,500) square feet or more of impervious surface and are not part of larger plan of development, shall implement stormwater control measures to reduce stormwater runoff from the project site.
1. Such projects shall implement one or more of the following stormwater control measures:
a. Stream setbacks and buffers: a vegetated area including trees, shrubs, and herbaceous vegetation, that exists or is established to protect a stream system, lake reservoir, or coastal estuarine area;
b. Soil quality improvement and maintenance: improvement and maintenance of soil through soil amendments and creation of microbial community;
c. Tree planting and preservation: planting and preservation of healthy, established trees that include both evergreens and deciduous, as applicable;
d. Rooftop and impervious area disconnection: rerouting of rooftop drainage pipes to drain rainwater to rain barrels, cisterns, or permeable areas instead of the storm drain;
e. Porous pavement: pavement that allows runoff to pass through it, thereby reducing the runoff from a site and surrounding areas and filtering pollutants;
f. Green roofs: a vegetative layer grown on a roof (rooftop garden);
g. Vegetated swales: a vegetated, open-channel management practice designed specifically to treat and attenuate stormwater runoff;
h. Rain barrels and cisterns: system that collects and stores stormwater runoff from a roof or other impervious surface.
2. Project applicants subject to this subsection (B) shall use the State Water Board SMARTS Post-Construction Calculator or equivalent to quantify the runoff reduction resulting from implementation of site design measures. This subsection (B) does not apply to LUPs.
C. Projects that create and/or replace five thousand (5,000) square feet or more of impervious surface shall implement LID standards designed to reduce runoff, treat stormwater, and provide baseline hydromodification management to the extent feasible. Such LID standards include site design, source control, runoff reduction, stormwater treatment, and baseline hydromodification management and depend on the size and scope of the proposed project.
1. In designing the site, project applicants shall evaluate how site conditions, such as soils, vegetation, and flow paths, will influence the placement of buildings and paved surfaces. Project applicants shall consider optimizing the site layout through the following methods:
a. Define the development envelope and protected areas, identifying areas that are most suitable for development and areas to be left undisturbed.
b. Concentrate development on portions of the site with less permeable soils and preserve areas that can promote infiltration.
c. Limit overall impervious coverage of the site with paving and roofs.
d. Set back development from creeks, wetlands, and riparian habitats.
e. Preserve significant trees.
f. Conform the site layout along natural landforms.
g. Avoid excessive grading and disturbance of vegetation and soils.
h. Replicate the site’s natural drainage patterns.
i. Detain and retain runoff throughout the site.
2. Project applicants shall develop and submit for the City’s review and approval a Stormwater Control Plan (SCP) that follows the appropriate SCP template in the most recent version of the BASMAA Post-Construction Manual. The SCP is separate and distinct from the ESCP requirements described in Larkspur Municipal Code Section 9.11.100(D).
3. All stormwater management measures shall be designed in a manner to minimize the need for maintenance and reduce the chances of failure. Design guidelines are outlined in the BASMAA Post-Construction Manual.
4. As a condition precedent to the issuance of a building permit, the project applicant shall also submit a preliminary Stormwater Facilities Operation and Maintenance Plan (O&M Plan). The City’s approval of the O&M Plan is required prior to final inspection and approval of building permit closure.
a. All stormwater management measures shall be maintained according to the approved O&M Plan. The person(s) or organization(s) responsible for maintenance shall be designated in the plan. The O&M Plan shall require that stormwater management measures be inspected by those responsible for maintenance at least annually.
b. The O&M Plan shall also describe how the maintenance will be funded. Upon the failure of a property owner to maintain the stormwater management measures in accordance with the O&M Plan, the City may perform the maintenance and recover its costs from the property owner as provided in Larkspur Municipal Code Section 9.11.120.
5. All project proponents and their successors, or successors in fee title, in control of project that is located within the City and that is defined as a regulated project in Provision E.12.c of the Phase II Stormwater Permit, or where required by the City, shall submit one of the following as a condition prior to final inspection and approval of building permit closure:
a. The project proponent’s signed statement accepting responsibility for the operations and maintenance of stormwater management measures until such responsibility is legally transferred to another entity;
b. Written conditions in the sales or lease agreements or deed for the project that requires the buyer or lessee to assume responsibility for the operations and maintenance of the stormwater management measures until such responsibility is legally transferred to another entity;
c. Written text in project deeds, or conditions, covenants and restrictions for multi-unit residential projects that require the homeowners’ association or, if there is no association, each individual owner to assume responsibility for the operation and maintenance of the stormwater management measures until such responsibility is legally transferred to another entity; or
d. Any other legally enforceable agreement or mechanism, such as recordation in the property deed, that assigns the operation and maintenance of the stormwater management measures to the project owner(s) or the City.
D. Subsection (C) of this section does not apply to the following projects: detached single-family home projects that are not part of a larger plan of development; interior remodels; routine maintenance or repair such as pavement resurfacing within the existing footprint; and LUPs, unless the LUP has a discrete location with five thousand (5,000) square feet or more of newly constructed contiguous impervious surface, in which case only that specific discrete location is subject to this section.
E. Financial security may be required to ensure that stormwater management facilities operate and are maintained following construction for a period which may be determined by the City. Financial security shall consist of an irrevocable letter of credit, cash deposit, or performance bond as determined by the City.
F. The authorized enforcement official has a right to inspect the stormwater management measures in place to verify compliance with the requirements of this chapter. At the authorized enforcement official’s request, the property owner shall provide applicable legal agreements, recorded covenants or easements.
G. If the authorized enforcement official determines, in their reasonable discretion, that the new development or redevelopment project is not properly implementing the requirements of this chapter, the authorized enforcement official may take corrective or enforcement actions consistent with the City’s Enforcement Response Plan and the remedies available in the Larkspur Municipal Code. (Ord. 1062 § 14, 2022; Ord. 1030 § 2(7), 2018; Ord. 1005 § 2, 2015)