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Permit Sonoma › Instructions and Forms › GRD-010 Grading and Drainage Notes
Instructions & Forms

GRD-010 Grading & Drainage Notes

Permit and Resource Management Department Banner 750

These notes provide information on the County’s requirements for performance of work related to grading and drainage activities.

Version: December 16, 2020

  1. Perform grading and drainage improvements in accordance with Chapter 11 and 11A of the Sonoma County code (SCC), applicable Sonoma County regulations and, if applicable, to the recommendations of the soils report prepared by ___________________________________ and dated ____/____/______.
  2. All work shall be done in compliance with the approved plans and specifications. The approved plans and specifications shall not be changed without the written approval of the Sonoma County Permit and Resource Management Department (Permit Sonoma). Proposed modifications to the approved plans and specifications shall be submitted to Permit Sonoma in writing, together with all necessary technical information and design details. The contractor shall immediately notify the property owner and engineer of record, if applicable, upon discovering discrepancies, errors, or omissions in the approved plans. Prior to proceeding, the property owner shall have the approved plans revised to clarify identified discrepancies, errors, or omissions. Permit Sonoma may require unauthorized work to be redone or removed to verify compliance with SCC. Permit Sonoma may initiate enforcement action and seek the imposition of civil penalties for violations of SCC.
  3. The grading or drainage permit and a copy of the approved plans shall be maintained on the project site throughout the duration of.
  4. Permit Sonoma may order that any work stop immediately if it is performed contrary to Chapter 11 and 11A of the SCC, the approved plans and specifications, permit conditions, or any work that has become hazardous to property or the public. A grading or drainage permit may be suspended, revoked, or modified by Permit Sonoma in accordance with SCC 11.24.080.
  5. Issuance of a grading or drainage permit by Permit Sonoma does not eliminate the responsibility of the property owner to secure permits from other agencies with regulatory responsibilities for the uses and construction activities associated with the work shown on the approved plans. Failure to obtain all required permits may result in fines from other agencies.
  6. Existing drainage courses receiving waters from the project site and located throughout the project site shall remain open and clear of debris to properly convey storm water. If existing drainage courses receiving waters from the project site are located in the County right-of-way and need maintenance, contact the Department of Transportation and Public Works at (707) 565-2231 for further assistance. In any event, the property owner and/or contractor shall be held liable for any damage due to obstructing natural drainage patterns.
  7. The contractor shall contact the underground service alert (USA), at 811, at least two working days, but not more than 14 calendar days, prior to excavation. The contractor shall uncover relevant utilities to verify their location and elevation. If unexpected or conflicting utilities are encountered during excavation, notify USA, the utility owner, and/or the engineer of record, if applicable, immediately. Utilities include but are not limited to water, sewer, electrical, gas, telephone, and cable/tv. The excavator shall delineate with paint or other suitable markings the area to be excavated.
  8. In the event cultural resources (such as historical, archaeological, and paleontological resources, and human remains) are discovered during grading or other construction activities, work shall immediately be halted within the vicinity of the find. The Northwest Information Center shall be notified at (707) 588-8455. A qualified archeologist shall be consulted for an on-site evaluation. Additional mitigation may be required by the County per the archeologist’s recommendations and SCC 11.16.050. If human burials or human remains are encountered, the contractor shall also notify the County Coroner at (707) 565-5070.
  9. Should grading operations encounter hazardous materials, or what appear to be hazardous materials, stop work immediately in the contaminated area and contact 911 or the appropriate agency for further instruction?
  10. Retaining walls, unless exempted per SCC 7.13(A)(3)4, are not approved under a grading permit. A separate building permit is required.
  11. Equipment shall not cross or disturb channels of actively flowing streams without a Permit Sonoma approved roiling permit and best management practices (SCC 23.1 and 11.16.060.D).
  12. Grading and drainage improvements shall be set back from lakes, ponds, streams, and wetlands in compliance with the requirements of SCC 11.16.100, 11.16.120, and 11.16.130. Existing vegetation shall be retained in stream setback areas to filter soil and other pollutants carried in storm water.
  13. Excess soil shall be removed from the project site unless depicted to remain on site per the approved plan. The site receiving soil may require a grading permit unless exempted by SCC 11.04.010.C.
  14. Contours, elevations, and shapes of finished surfaces shall be blended with adjacent natural terrain to achieve a consistent grade and natural appearance. Borders of cut slopes and fills shall be rounded off to a minimum radius of five feet to blend with the natural terrain.
  15. Fill material shall not include organic, frozen, or other deleterious materials. No rock or similar irreducible material greater than six inches in any dimension shall be included in fills except where approved by the soils engineer. Fills shall be constructed in lifts not exceeding eight inches in depth. Completed fills shall be stable, well-integrated, and bonded to adjacent materials and the materials on which they rest. Fills shall be competent to support anticipated loads and be stable at the design slopes shown on the approved plans and specifications or as directed by the soils engineer.
  16. Ground surfaces shall be prepared to receive fill by removing vegetation, topsoil, and other unsuitable materials, and scarifying the ground to provide a bond with the fill material.
  17. Fill shall not be placed on natural slopes steeper than 2H:1V (50 percent).
  18. Fills intended to support structures or surcharges shall be compacted to a minimum of 90 percent of maximum dry density, as determined by ASTM D 1557, modified proctor. A higher compaction percentage may be required by the soils engineer.
  19. Fills not intended to support structures or surcharges shall be compacted as follows:
    1. Fill greater than three feet in depth shall be compacted to the density specified by the soils engineer.
    2. Fills no greater than three feet in depth shall be compacted to the density necessary for the intended use or as directed by the soils engineer.