Erosion Control

Prior to permit issuance for building, grading, or land clearing, an erosion control plan indicating proposed methods to control of runoff, erosion, and sediment movement shall be submitted and approved to the appropriate Director. Erosion control plans may also be required for other types of applications where erosion can reasonably be expected to occur. The erosion control plan may be incorporated into other required plans, provided it is identified as such.

Erosion control plans shall include as a minimum the measures required under Sections 16.12.070, 16.12.090, and 16.12.110 of this Chapter. Additional measures or modification of proposed measures may be required prior to project approval. No grading or clearing may take place on the site prior to approval of an erosion control plan for that activity. Final certification of project completion may be delayed pending proper installation of measures identified in the approved erosion control plan.

Two sets of plans shall be required for each application; particular specifications may be required by the HCD Director. Plans shall be drawn to scale upon substantial material, minimum size eighteen (18) inches by twenty-four (24) inches, and shall be of sufficient clarity to indicate the nature and the extent of the work proposed and show in detail that it will conform to the provisions of this Chapter and all relevant laws and regulations. The minimum size for plans for land clearing permits shall be eight and one-half inches by eleven (11) inches. The plans shall include the following information in writing and/or diagrams:

• General location of the proposed site.
• Property lines and contours of the site including finish contours to be achieved by grading, details of terrain, and area drainage; proposed construction, proposed drainage channels, and other runoff control measures.
• Detailed plans of all surface and subsurface drainage devices, dams, and other erosion control measures to be constructed with, or as a part of, the proposed work. All measures required under this Chapter shall be shown. Function of erosion control measures shall be consistent with the provisions of this Chapter.
• Delineation of areas to be cleared during development activities.
• Revegetation proposal for all surfaces exposed or expected to be exposed during development activities, including cut and fill slopes.
• Name and address of the owner(s).
• Assessors parcel number(s) of the property on which the work is to be done.
• North arrow, scale, and name and location of nearest public road intersection.
• Name, address, and phone number of person who prepared the plan.

For minor development proposals, the erosion control plan is not required to be prepared by a registered professional, as listed below.

For major development proposals, the erosion control plan shall be prepared by a registered civil engineer, professional forester, landscape architect, registered geologist, certified engineering geologist, or approved erosion control specialist. For these major projects, runoff calculations and other calculations demonstrating adequacy of drainage structures shall be included. Inspection by the person preparing the plan and certification of proper installation of control measures may be required. Major proposals include:

• Subdivisions of more than four lots.
• Planned unit developments, major planned developments, and major use permits.
• Other projects of a similar nature determined by Planning Services to cause major land disturbance.

Applications for activities where no land disturbance is anticipated may be accompanied by a statement to that effect, which shall be approved by the HCD Director, in lieu of an erosion control plan.

• Soils:
  • Soil Survey of Monterey County
  • Caltrans Corrosion Guidelines

Runoff from activities subject to a development permit shall be properly controlled to prevent erosion. The following measures shall be used for runoff control, and shall be adequate to control runoff from a ten (10) year storm:

• On soils having high permeability (more than two inches/hour), all runoff in excess of predevelopment levels shall be retained on the site. This may be accomplished through the use of infiltration basins, percolation pits or trenches, or other suitable means. This requirement may be waived where the HCD Director upon recommendation of the Health Department determines that high groundwater, slope stability problems, or other conditions, would inhibit or be aggravated by onsite retention, or where retention will provide no benefits for ground water recharge or erosion control.
  
  
• On projects where onsite percolation is not feasible, all runoff must be detained or dispersed over non-erodible vegetated surfaces so that the runoff rate does not exceed the predevelopment level. Onsite detention may be required where excessive runoff would contribute to downstream erosion or flooding. Any policies and regulations for any drainage zones where the project is located will also apply.
  
  
• Any concentrated runoff which cannot be effectively detained or dispersed without causing erosion, shall be carried in non-erodible channels or conduits to the nearest drainage course designated for such purpose or to onsite percolation devices. Where water will be discharged to natural ground or channels, appropriate energy dissipaters shall be installed to prevent erosion at the point of discharge.
  
  
• Runoff from disturbed areas shall be detained or filtered by berms, vegetated filter strips, catch basins, or other means as necessary to prevent the escape of sediment from the disturbed area.
  
  
• No earth or organic material shall be deposited or placed where it may be directly carried into a stream, marsh, slough, lagoon, or body of standing water.

Land clearing shall be kept to a minimum. Vegetation removal shall be limited to that amount necessary for building, access, and construction as shown on the approved erosion control plan. The following provisions shall apply:

• No land clearing shall take place prior to approval of the erosion control plan. Vegetation removal between October 15th and April 15th shall not precede subsequent grading or construction activities by more than fifteen (15) days. During this period, erosion and sediment control measures shall be in place.
  
  
• All disturbed surfaces shall be prepared and maintained to control erosion and to establish native or naturalized vegetative growth compatible with the area. This control shall consist of:
  • Effect temporary planting such as rye grass, some other fast-germinating seed, and mulching with straw and/or other slope stabilization material;
  • Permanent planting of native or naturalized drought resistant species of shrubs, trees, or other vegetation, pursuant to the County's Landscape Criteria, when the project is completed;
  • Mulching, fertilizing, watering or other methods may be required to establish new vegetation. On slopes less than twenty (20) percent, topsoil should be stockpiled and reapplied. 
    The protection required by this Section shall be installed prior to calling for final approval of the project and at all times between October 15th and April 15th. Such protection shall be maintained for at least one winter until permanent protection is established.
    
    
• A land-clearing permit shall be required for any land clearing of more than two and one-half acres per year per site in excess of that shown on an approved development plan; except in water supply watersheds, or high erosion hazard areas, where a permit shall be required for any clearing in excess of one acre per year per site in excess of that shown on an approved development plan. Application for a permit shall be made on forms for that purpose and shall include submittal of an erosion control plan. A permit may be approved, conditioned, or denied pursuant to procedures established by the Board of Supervisors.
  
  
• Land clearing that is not a part of a permitted activity shall not take place on slopes greater than thirty (30) percent (twenty-five (25) percent for North County LUP). Exceptions may be made for special circumstances. Ref. Section 16.08.060B Monterey County Code. The process includes submitting an application for an exception and a noticed public hearing to determine if the exception is valid. 

• No land clearing operations greater than one acre per year per site or grading operations greater than one hundred (100) cubic yards may take place between October 15th and April 15th, in water supply watersheds, and high erosion hazard areas, unless authorized by the HCD Director and found to be consistent with the purposes of this Chapter. Winter operations for other projects may be disallowed if a high potential for erosion exists due to slope, rock or soil type, proximity to a stream or drainage course, magnitude or duration of disturbance, or other characteristics of the project and the site. When construction will be delayed due to the limitation on winter operations, the date for expiration of the permit shall be extended by that amount of time that work is delayed by this Chapter.
  
  
• When winter operations do take place, the following measures must be taken to prevent accelerated erosion. Additional measures may be required.
  • Between October 15th and April 15th, disturbed surfaces not involved in the immediate operations must be protected by mulching and/or other effective means of soil protection.
  • All roads and driveways shall have drainage facilities sufficient to prevent erosion on or adjacent to the roadway or on downhill properties. Erosion-proof surfacing may be required in areas of high erosion hazard.
  • Runoff from a site shall be detained or filtered by berms, vegetated filter strips, and/or catch basins to prevent the escape of sediment from the site. These drainage controls must be maintained by the permittee and/or property owner as necessary to achieve their purpose throughout the life of the project.
  • Erosion control measures shall be in place at the end of each days work.
  • The HCD Director shall stop operations during periods of inclement weather if he or she determines that erosion problems are not being controlled adequately.