Hillside, septic and fire access in LA County.
I wanted to highlights several significant development constraints specific to hillside properties in Los Angeles County. Based on experiences with recent projects in the Altadena area, these issues can drastically alter a project's scope, building envelope, and programmatic possibilities. Early identification and assessment are paramount to project feasibility.
Many are now familiar with the LA County Department of Regional Planning (DRP) "like-for-like" policy, allowing a rebuild to 110% of the original building's height, floor area, and footprint. This allowance is not guaranteed on hazardous sites.
A superseding layer of review is conducted by the Geotechnical and Materials Engineering Division (GMED). During recent due diligence for a proposed rebuild and Accessory Dwelling Unit (ADU), the project was flagged for a mandatory GMED screening due to its location. This screening assesses factors such as: presence of ancient landslides; adverse soil conditions; and steep or unstable topography.
The determination from GMED can override the DRP's 110% allowance. In our case, this review threatened to restrict the project to a 100% rebuild of the original footprint and preclude the construction of the ADU entirely. This demonstrates that geotechnical hazards are a primary constraint that can supersede standard planning policies.
For properties not connected to a municipal sewer system due to remoteness or topography, a septic system is required. A septic system, consisting of a septic tank and one or more seepage pits, mandates strict clearances from structures, property lines, and water sources. Considerations for access, maintenance, and potential odors directly impact the location of the main residence and any ancillary structures. On a sloped site, the number of viable locations for a compliant septic field can be severely limited, impacting the viable locations for main residence.
Fire regulations for hillside homes are stringent, particularly concerning access on roads that do not meet modern standards. Any dead-end road extending more than 150 feet from the nearest intersection requires an approved fire truck turnaround. These turnarounds have substantial spatial footprints and must conform to one of several approved configurations (e.g., T-shape, Y-shape/Hammerhead, or a 64-foot radius Cul-de-Sac/O-shape). The need to accommodate such a large feature on a constrained hillside lot can dramatically reduce the usable area for development and landscaping.
Geotechnical overrides, septic system limitations, and fire access are issues that require a highly experienced team, including Architect, Civil Engineer, and Geotechnical Engineer, at the earliest possible stage of the project. A thorough feasibility study that addresses these specific points is a critical investment in ensuring the developable area of a hillside property is understood before significant commitments.
