Soil stability and erosion control measures shall be required in areas where it is determined that exposed soils or other conditions have the potential to create water quality impacts, damage to Clear Lake and tributary streams, damage to public or private property, damage to fish and wildlife areas, create flooding hazards, decrease productivity of agricultural lands, or lead to unwanted soil deposits.
(Ord. 796 Att. A(part), 1999)
The responsibility for implementation of slope stability or erosion control measures shall be the owner(s) of private property on which it is observed and determined by the city that soil degradation is occurring or has the potential to occur.
(Ord. 796 Att. A(part), 1999)
The determination of the need to perform slope stabilization or to implement erosion control measures shall be made by the community development director in consultation with other city, county, state or federal agencies. Evidence of erosion occurring on land including, but not limited to, gullying, slippage, turbid runoff during storm periods, build-up of soils, and other similar situations shall be considered in making a determination that slope stabilization or erosion control measures are necessary. Construction projects involving the movement of soils and/or clearing and grubbing of sites that expose soils to the elements shall also complete erosion control measures.
(Ord. 796 Att. A(part), 1999)
After a determination is made that erosion control is needed, the property owner shall be required to complete some or all of the following measures to stop, reduce, or minimize the erosion problem. The specific extent of erosion control measures shall be determined by the community development director and implemented within a specific time frame as set forth in a written notice to said owner.
A. 
General Erosion Control. All property owners within the city shall generally use the following measures to minimize erosion within the city:
1. 
Keep soil disturbance to a minimum land area for a minimum length of time.
2. 
Maintain low slope angles and short slope lengths.
3. 
Revegetate disturbed soil areas with grass seeds and/or plants.
4. 
Fertilize and irrigate revegetation areas.
5. 
Perform slope stabilization and erosion control measures in areas adjacent to streams, creeks, ponds, and Clear Lake.
6. 
Where necessary, use mechanical stabilization techniques to control erosion and sedimentation.
7. 
Check erosion control measures periodically to monitor their effectiveness.
8. 
Complete grading and erosion control only during the dry season.
9. 
Comply with the grading requirements of the currently adopted California Building Standards Code as referenced in Section 15.04.010.
B. 
Erosion Control on Slopes Less Than 4:1. Property owners shall mulch the erosion areas with soil and place loose straw in a thin layer (one to two inches). The straw shall be pushed in with a shovel or a ring roller. Seeding with a mechanical drill or hand spreader may also be permitted. In certain situations, the planting of trees and shrubs may be required. Slope length should be limited to thirty-three feet by the use of barriers, including straw bales fixed with stakes or rebar; berms; fences; and wattling. In addition, infiltration trenches and channels may be required.
C. 
Erosion Control on Moderate Slopes 4:1 to 2:1. Property owners shall mulch erosion areas with soil and loose straw spread in a thin layer (one to two inches). The straw shall be pushed in with a shovel or ring roller. On steeper slopes, the straw shall be required to be held down with chemical tackifiers overlying the straw or with netting made of woven paper, excelsior, or jute. The netting must be close to the surface so that water does not erode underneath. Hydroseeding, hydromulching, or hand broadcasting of seeds shall be employed. Planting of native grasses, shrubbery, and trees shall be required to maintain long-term stability.
For long, steep slopes, the construction of barriers such as straw bales fixed with stakes, rock and soil berms, fences, wattling, infiltration trenches, and cutting horizontal ledges into steep slopes (steeping or serration) shall be required. Additional top soil, seed, and fertilization may be required. The slope length will be a maximum of eighteen feet.
D. 
Erosion Control on Steep Slopes Greater Than 2:1. Property owners shall mulch erosion areas with soil and loose straw spread in a thin layer. In these areas, revegetation success may be poor due to slope instability and rapid water runoff. In addition to shortening the slopes as set forth in subsection C of this section, concrete block revetment, piled rock, gabion baskets, or retaining walls may be required. Hydroseeding, hydromulching, and hand broadcasting of seed will be required on the slope above these structures. The addition of topsoil and fertilizer may also be necessary. The revegetation areas may be required to be provided with irrigation facilities and repaired as necessary. The planting of native grasses, shrubbery, and trees to maintain the long-term stability will be required.
E. 
Erosion Control Adjacent to Water Bodies. In addition to all of the measures described above, additional measures shall be required for those properties near Clear Lake, creeks, and seasonal streams. For those areas within one hundred feet of a water body, no unprotected fill or stockpiled soil materials shall be allowed. Disturbance of vegetation cover must be kept to a minimum amount. Drainage control and sediment control with appropriate devices such as barriers, channels, infiltration trenches, water energy absorbing devices, and sediment traps may also be required.
For those areas within thirty feet of Clear Lake, creeks, or seasonal streams, the removal of stable mature trees or other vegetation down to bare soil or the grading and constructing of roads, unless required for health and safety purposes, shall be avoided. Extra protection for drainage and sediment control with appropriate devices such as barriers, channels, infiltration trenches, water energy absorbing devices, and sediment traps will also be necessary.
(Ord. 796 Att. A(part), 1999; Ord. 821 § 1(part), 2003; Ord. 924 § 24, 2020)
Development projects constructed in areas with slopes, or that involve significant exposure of bare soils, may be required to prepare and submit an engineered erosion control plan as part of the development review process or prior to the issuance of a building permit for the project. Where cuts and fills exceed fifteen feet in height; where there is a possibility of land slides; where soil erodibility factors are high, such as those with loose, sandy, or silty soils; or where the proposed project is within one hundred feet of Clear Lake, creeks, or seasonal streams, a professionally prepared engineering plan may be required. A determination of the specific type of plan shall be made as part of the environmental review process associated with the development project.
(Ord. 796 Att. A(part), 1999)