Grading and Drainage Standards in Concord
Development projects in the City of Concord must adhere to specific requirements to ensure proper site drainage, sediment control, and protection of natural features. All grading and improvement plans must be submitted to the planning division for review and approval, and must comply with the Contra Costa Clean Water Program standards and the city’s National Pollutant Discharge Elimination System (NPDES) permit requirements.
General Grading and Drainage Requirements
The City of Concord requires that all grading and drainage improvements be designed to minimize impacts on water quality and prevent erosion.
- Stormwater Management: Every development project that meets or exceeds the stormwater treatment threshold established by the applicable NPDES permit must be accompanied by a stormwater control plan [Section 18.175.010].
- Drainage Design: All drainage must be discharged to natural or engineered off-site facilities and shall not drain across public or private pedestrian sidewalks, walkways, or areas not designated as drainage facilities [Section 18.160.100].
- Permeable Surfaces: Projects are encouraged to incorporate permeable surfaces, such as wood plank decks or sand-joined bricks, to facilitate ground absorption and minimize off-site water flow [Section 18.150.150].
- Creek and Riparian Areas: For properties adjacent to or crossed by a watercourse, development must comply with specific structural setbacks based on the height of the top of the bank [Section 18.305.040]. No grading, filling, or removal of native vegetation is permitted within these structure setback areas without appropriate permits from the California State Department of Fish and Game [Section 18.305.040].
Exceptions to Grading Review
Design and site development review for grading is not required under the following conditions:
| Exception Category | Description |
|---|---|
| Minor Movement | Movement of less than 200 cubic yards of material not related to previous grading, provided it does not occur in a hillside protection area or affect a wetland, creek, or drainage channel. |
| Approved Plans | Grading plans previously approved as part of a building permit, planning permit, or tentative map. |
| Minor Impact | Grading determined by the planning division to be minor with no adverse environmental or visual impacts. |
| Emergency | Grading necessary to protect public health, safety, and welfare during an emergency or disaster. |
Hillside Grading Standards
For hillside parcels (average slope of 15% or greater), additional standards apply to minimize erosion and protect natural topography:
- Undisturbed Areas: All areas with an existing average slope of 30% or greater must remain undisturbed [Section 18.300.050].
- Slope Limits: Slopes created or altered by grading shall not exceed 30% [Section 18.300.050].
- Impervious Surfaces: On slopes up to 15%, impervious surfaces shall not exceed 40% of the gross land area; on slopes exceeding 15%, impervious surfaces shall not exceed 30% [Section 18.300.050].
- Drainage for Hillside Lots: Drainage must be accommodated with swales and catch basins rather than V-ditches, and lot-to-lot drainage at the top of slope areas is prohibited [Section 18.300.080].
Performance Standards for Liquid and Solid Wastes
All development must ensure that liquids and solids of any kind are not discharged into any public or private body of water, sewage system, or onto the ground, except as permitted by the California Regional Water Quality Control Board [Section 18.150.130]. Solid waste and recycling must be handled and stored to prevent nuisances, and there shall be no outdoor accumulation of waste conducive to the breeding of rodents or insects [Section 18.150.130].
Sections Cited
- Section 18.150.130: Performance standards
- Section 18.150.150: Solid waste and recycling storage
- Section 18.160.100: Additional standards for driveways, access easements, curb cuts, parking lots, and structures
- Section 18.175.010: Stormwater management
- Section 18.300.050: Development standards (Hillside)
- Section 18.300.080: Application, review authority, review, and hearing
- Section 18.305.040: Development standards (Creek/Riparian)