Chapter 18.30 SITE GRADING AND EROSION CONTROL

Chapter 18.30
SITE GRADING AND EROSION CONTROL

Sections:

18.30.030 Grading and fill requirements.

18.30.050 Temporary erosion and sediment control policies and criteria.

18.30.010 Purpose.

(1) The purpose of this chapter is to protect existing public and private improvements against damage that may occur as a result of grading activities on private properties within the city of Coos Bay. In addition, minimum erosion control measures are identified which are intended to prevent or minimize sediment discharge from sites where grading is planned.

(2) Depending on the location and nature of the work, permits may also be required. This can include but is not limited to the Oregon Department of Environmental Quality (DEQ), Oregon Division of State Lands (DSL), the Army Corps of Engineers, the Oregon Department of Fish and Wildlife (ODFW), or U.S. Fish and Wildlife. If such permits are required, the applicant shall provide evidence to the city that a permit has been obtained prior to any clearing, grading, or excavation activities. [Ord. 479 § 1 (EDS § 6.1), 2016].

18.30.020 Site development permits.

(1)(a) Site development permit is required for all proposed grading (excavation or fill) activity within the city of Coos Bay, including but not limited to lot leveling, slope grading, site drainage, retaining wall excavation and fill, and other grading activities associated with site development.

(b) Site development permits are not required for sites on which excavation is limited to footing or foundation excavations and utility trenches. These items shall be covered under the building permit. This does not exempt these activities from installing the appropriate temporary sediment and erosion control measures during the construction activity.

(c) Site development permits, when required, shall be obtained from the city of Coos Bay public works department. The permit application form is available on the city’s website or from the public works department.

(d) A bond shall be required to ensure that the work is done to city standards. The bond will be forfeited if the work is not inspected and approved by public works.

(2) Grading Plan.

(a) Each application for a site development permit shall be accompanied by a plan which clearly shows the nature and extent of the work proposed.

(b) A geological study prepared by an Oregon licensed geotechnical engineer or (depending upon the nature of the project) a certified engineering geologist is required to be submitted to and approved by public works prior to grading and/or proposed new development on slopes exceeding 25 percent. The study shall address overall slope stability, before, during, and after disturbance and/or development. Geological recommendations shall include methods for maintaining slope stability and managing stormwater during construction. All geological recommendations shall be incorporated in the applicant or developer’s grading permit application, and approved by the engineer upon completion of construction. It is the responsibility of the owner to obtain all other necessary regulatory permits.

(c) Grading plans as described herein are intended for proposed grading, excavation, or fill projects on existing platted parcels within the city of Coos Bay. Grading plans for land division projects shall be included with plans submitted for development review as specified in Chapter 18.10 CBMC, General Requirements.

(d) The following items shall be included on each proposed grading plan:

(i) Name of the property owner and the person or firm that prepared the plan.

(ii) Site address and map parcel number.

(iii) Property lines and any easements on or across the property.

(iv) Limits of clearing.

(v) Extents of proposed grading, including depth of cut and fill.

(vi) Location of all existing and proposed buildings or structures and location of any buildings or structures within 15 feet of the proposed grading.

(vii) Location of any existing or proposed retaining walls (label wall height).

(viii) Location of any existing or proposed drainage courses or piping.

(ix) Configuration of all proposed cut and fill slopes (i.e., 2H:1V).

(x) Existing and proposed topography with two-foot contour intervals. [Ord. 479 § 1 (EDS § 6.2), 2016].

18.30.030 Grading and fill requirements.

(1) Fill slopes shall not exceed two feet horizontal to one foot vertical (2:1) unless approved by a qualified Oregon licensed geotechnical engineer or (depending upon the nature of the project) a certified engineering geologist. The toe of fill slopes shall be set back from property boundaries at least one-half the height of the fill with a minimum of two feet and a maximum of 20 feet. Where a fill slope is to be located near the property boundary, precautions shall be taken to protect the adjoining property from damage as a result of such grading. These precautions may include but are not limited to:

(a) Additional setbacks.

(b) Provision for retaining or slough walls.

(d) Provisions for the control of runoff.

(2) Cut slopes shall be no steeper than two feet horizontal to one foot vertical (2:1) unless a geological study prepared by an Oregon licensed geotechnical engineer or (depending upon the nature of the project) a certified engineering geologist is submitted which justifies that a steeper slope can be safely constructed and will not create a hazard to adjoining public or private property. The top of cut slopes shall not be made nearer to a site boundary line than one-fifth the height of cut, with a minimum of two feet and a maximum of 10 feet.

(3) Surface vegetation and topsoil must be grubbed to a depth of at least six inches prior to placement of fill material. All existing vegetation must be removed from areas designated to receive fill prior to placement.

(4) Fill material shall be free of all rubbish, organic material, and other deleterious substances which could be detrimental to the stability of the fill.

(5) Fill shall be compacted to at least 90 percent of maximum density as determined by the ASTM D1557 (Modified Proctor) test method. Fill material shall be placed in lifts not exceeding 12 inches compacted depth.

(6) A report prepared by an Oregon licensed geotechnical engineer, or (depending upon the nature of the project) a certified engineering geologist is required when fills in excess of 12 inches are planned within future building areas. The specified fill material shall be placed and compacted in accordance with the recommendations of the report. Any required testing shall be as recommended in the report.

(7) Disturbed areas not scheduled for construction of buildings or other improvements shall be stabilized with permanent erosion control to prevent erosion once grading is complete. Stabilization shall be completed within 30 days of the date all grading is finished. Temporary stabilization measures may also be required prior to completion of the project if the city determines it is necessary due to windblown dust or erosion at the site. [Ord. 479 § 1 (EDS § 6.3), 2016].

18.30.040 Other requirements.

(1) For sites located partially or entirely within a special flood hazard area as identified on the FEMA Flood Insurance Rate Maps, the project must meet the requirements of Chapter 17.318 CBDC, Flood Damage Prevention. An engineering evaluation to determine the impact of fill on floodwater elevation may be required.

(2) A biological evaluation may also be required to determine impact to endangered species and/or their habitat.

(3) The disturbance of one or more acres requires application for a National Pollutant Discharge Elimination System (NPDES) General Permit 1200-C as administered by the Oregon Department of Environmental Quality (DEQ). The application form is available online or can be obtained from the local DEQ office. Issuance of a site development permit from the city of Coos Bay does not meet or negate the requirement to obtain an NPDES General Permit 1200-C.

(4) Excavations exceeding 5,000 cubic yards within a 12-month period require an operating permit from the Oregon Department of Geology and Mineral Industries (DOGAMI). Application forms are available online or by contacting DOGAMI at (971) 673-1555.

(5) If the proposed grading includes import or export of materials, a heavy hauling permit may be required by the city of Coos Bay. Heavy hauling permits require bonding to insure against damage to existing infrastructure within the right-of-way (see Chapter 12.05 CBMC). The amount of bonding required is based on the volume of import/export and will be determined by public works. [Ord. 479 § 1 (EDS § 6.4), 2016].

18.30.050 Temporary erosion and sediment control policies and criteria.

(1) General. Submission of an erosion and sediment control plan is required in conjunction with each site development permit application. The best management practices (BMPs) listed in subsection (3) of this section are the required minimum measures but may not be appropriate for every site. The city will review erosion and sediment control plans for completeness and compliance with requirements. However, it is the responsibility of the applicant to install proper and adequate sediment and erosion control measures such that the site is adequately stabilized and the downstream properties and receiving waters are protected for the duration of the construction.

(2) Referenced Standards. For erosion control best management practices (BMPs) refer to the Oregon Department of Environmental Quality Erosion and Sediment Control Manual.

(3) Required Best Management Practices (BMPs). The BMPs listed below are required, where applicable, for grading projects within the city of Coos Bay. Additional measures may be required depending on project scope or as a condition of other required permits such as the NPDES General Permit 1200-C.

(a) Mark Clearing Limits. Clearing and grading of the site should be planned properly. It is important to clear only the areas needed, thus keeping exposed areas to a minimum. Clearing should be phased so that only those areas that are actively being worked are uncovered. Clearing limits shall be flagged prior to the initiation of clearing.

(b) Stabilized Construction Entrance. A stabilized construction entrance must be constructed prior to initiating grading. The stabilized construction entrance shall be the sole entrance or egress from the site. Do not install gravel on paved surfaces. Stabilized construction entrances shall be installed and maintained in accordance with the requirements of Appendix F – Part SC-10 of the DEQ Erosion and Sediment Control Manual.

(c) Protect Stockpiles and Staging Areas. Soil and material stockpiles shall be situated so that the material does not erode into the street or adjoining properties. Excavated soil and material stockpiles should be located at least 10 feet behind the curb, such as in the backyard or side yard area. This practice will increase the distance eroded soil and stockpiled material must travel to reach the stormwater conveyance system. If applicable to the site, concentrated flows shall be diverted away from staging areas and stockpiles using BMPs from the DEQ Erosion and Sediment Control Manual. Soil and material stockpiles shall be covered when not in use (e.g., when not accessed for 48 hours or more) during the period of October 1st to May 31st. This requirement may be waived for soil and gravel stockpiles on flat (less than five percent) slopes if, in the opinion of the city inspector, the risk of erosion is minimal.

(d) Sediment Fence. Install sediment fence along a level contour, with the last six feet of fence turned up slope. Except for the ends, the difference in elevation between the highest and lowest points along the top of the sediment fence shall not exceed one-third the fence height. Sediment fence shall be installed and maintained in accordance with the requirements of Appendix F – Part SC-1 of the DEQ Erosion and Sediment Control Manual.

(e) Storm Drain Inlet Protection. Protect storm drain inlets immediately downstream from the site using BMPs from Appendix F – Part SC-8 of the DEQ Erosion and Sediment Control Manual.

(f) Slope Protection and Temporary Cover. Slope stabilization measures (for slopes 3:1 and steeper) must be initiated within 14 calendar days between June 1st and September 30th and within seven days between October 1st and May 31st in portions of the site where grading activities have temporarily or permanently ceased. Slopes shall be stabilized using mulch, erosion control matting, or other methods as approved. Methods for slope protection shall be as recommended in Appendices E and F of the DEQ Erosion and Sediment Control Manual.

(g) Establish Permanent Cover. Prior to removal of erosion control and temporary slope protection measures, permanent cover must be established on the site. Permanent cover shall be installed within 30 days of the date all grading and other site work is finished. Permanent cover shall include seeding, vegetative plantings, and other methods as approved. Refer to Appendices E and F of the DEQ Erosion and Sediment Control Manual.

(4) Inspection – Final Inspection. Final inspection of permanent cover is required for closeout of each site development permit. A final inspection should be scheduled when the site is 75 percent stabilized. [Ord. 479 § 1 (EDS § 6.5), 2016].