Chapter 21.74


21.74.010    Development activity plan – When required.

21.74.020    Development activity plan standards.

21.74.010 Development activity plan – When required.

a. This chapter applies to a development activity plan (DAP) when required by another provision of the zoning code.

b. When a DAP is required, no person shall do or cause to be done any development activity on the site without first obtaining a DAP approved by the City. [Ord. 08-29, 2008].

21.74.020 Development activity plan standards.

The DAP shall provide for the control of stormwater discharges, the control of total suspended solids, and the control of other pollutants carried in runoff. The DAP shall address and satisfy each of the standards established in this section. These standards apply during construction and all other phases of development activity.

a. Stabilization and Sediment Trapping. All exposed or disturbed soils with grades exceeding 10 percent and soils exposed to concentrated surface runoff flows, including soil stockpiles, shall be stabilized in a way that protects soil from the erosive forces of weather and flowing water. Applicable practices include, but are not limited to, the installation of silt fences, vegetative establishment, mulching, plastic covering, and the early application of gravel base on areas to be paved. No soils shall remain unstabilized for more than three days. At all times of the year, the contractor shall have sufficient materials, equipment and labor on site to stabilize and prevent erosion from all disturbed areas before initiating or continuing work.

b. Delineation of Clearing and Easement Limits. Clearing limits, setbacks, buffers, and sensitive or critical areas such as steep slopes, wetlands and riparian corridors shall be clearly identified in the DAP, marked in the field, and inspected by the City prior to commencement of land clearing activities.

c. Protection of Adjacent Properties. Adjacent properties shall be protected from sediment deposition by appropriate use of vegetative buffer strips, sediment barriers or filters, dikes or mulching, or by a combination of these measures and other appropriate methods.

d. Timing and Stabilization of Sediment Trapping Measures. Sediment ponds and traps, perimeter dikes, sediment barriers and other approved methods intended to trap sediment on site shall be constructed as a first step. These methods shall be functional before additional land-disturbing activities take place. Earthen structures such as dams, dikes, and diversions shall not remain unstabilized for more than three days.

e. Slope Stabilization. Cut and fill slopes shall be constructed in a manner that will minimize erosion. Roughened soil surfaces are preferred to smooth surfaces. Interceptors should be constructed at the top of long, steep slopes that have significant areas above that contribute runoff. Concentrated runoff should not be allowed to flow down the face of a cut or fill slope unless contained within an adequate channel or pipe slope drain. Wherever a slope face crosses a water seepage plane, adequate drainage or other protection should be provided. In addition, slopes should be stabilized in accordance with subsection (a) of this section.

f. Controlling Off-Site Erosion. Properties and waterways downstream from development sites shall be protected from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the development site by the implementation of appropriate methods to minimize adverse downstream impacts.

g. Stabilization of Conveyance Channels and Outlets. All temporary and permanent on-site conveyance channels shall be designed, constructed and stabilized to prevent erosion from the expected flow velocity from a two-year, three-hour duration storm for the post-development condition. Stabilization adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream reaches shall be provided at the outlets of all conveyance systems.

h. Storm Drain Inlet Protection. All storm drain inlets made operable during construction shall be protected so that stormwater runoff shall not enter the conveyance system without first being filtered or otherwise treated to remove sediment. After proper written application, the requirement for inlet protection may be waived by the City on a site-specific basis when the conveyance system downstream of the inlet discharges to an appropriate on-site sediment control method, including but not limited to sediment ponds or traps. The conveyance system will be adequately cleaned following site stabilization.

i. Underground Utility Construction. The construction of underground utility lines shall be limited, where feasible, to no more than 500 feet of open trench at any one time. Where consistent with safety and space considerations, excavated material shall be placed on the uphill side of the trench. Dewatering devices shall discharge to an appropriate sediment trap or pond, preceded by adequate energy dissipation, prior to runoff leaving the site.

j. Constructed Access Routes. Wherever construction vehicle routes intersect paved roads, provisions must be made to minimize the transport of sediment (mud) and debris onto the paved road by use of approved methods. If sediment or debris is transported onto a road surface, the roads shall be cleaned thoroughly, as a minimum, at the end of each day. Sediment or debris shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Street washing shall be allowed only after sediment is removed in this manner.

k. Removal of Temporary Erosion and Sediment Control Methods. All temporary erosion and sediment control methods shall be removed within 30 days after final site stabilization is achieved or after the temporary methods are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil areas resulting from removal of temporary methods shall be permanently stabilized. The removal of temporary erosion and sediment control methods may not be required for those projects, such as single-family developments, that will be followed by additional construction under a different permit. In these circumstances, the need for removing or retaining the measures will be evaluated on a site-specific basis.

l. Dewatering Construction Sites. Dewatering devices shall discharge into an appropriate sediment trap or pond designed to accept such a discharge, preceded by adequate energy dissipation, prior to runoff leaving the site.

m. Control of Pollutants Other Than Sediment on Construction Sites. All pollutants other than sediment that occur on site during construction shall be handled and legally disposed of in a manner that does not cause contamination of ground or surface waters. Pollutants of concern include, but are not limited to, fuels, lubricants, solvents, concrete by-products and construction materials.

n. Maintenance. All temporary and permanent erosion and sediment control methods shall be maintained and repaired as needed to assure continued performance of their intended function. The owner shall be responsible for assuring that any such facilities damaged during floods, storms or other adverse weather conditions are immediately returned to normal operating condition.

o. Erosion Control. Erosion control design storm event facilities designed for the control of erosion and sedimentation shall be designed for the erosion and sedimentation control design storm event, defined as the two-year, three-hour duration storm.

p. Changes in Site Topography.

1. The maximum surface gradient on any artificially created slope shall be two feet of horizontal run to one foot of vertical fall (2:1). This gradient may be increased to a steeper slope, if, in the judgment of the Director of Public Works, it has been demonstrated by the developer through engineering calculations performed by a qualified professional engineer that surface erosion at such a gradient can be controlled to that erosion rate equal to a properly stabilized 2:1 slope under the same conditions.

2. The developer shall, at all times, protect adjacent properties and public rights-of-way and easements from damage occurring during, or resulting from, grading operations. The developer shall restore public improvements damaged by the developer’s operations.

q. Correction of Defective Maintenance. If the developer or owner, or both, refuse or fail to adequately maintain and keep the erosion and sediment control facilities functional at all times, and the owner of the property is given seven days’ notice to perform the work necessary to make the facility functional and fails to do so, the City may use public funds to complete maintenance of the facilities at the cost of the developer and the property owner, who shall be jointly and severally liable for such costs.

r. Progress of Work. All work required or approved under this section shall proceed continuously to completion in an expeditious manner unless otherwise authorized by the Director of Public Works, with the intent that work may be halted, for example, due to weather conditions or the need to coordinate other construction on the project site. [Ord. 08-29, 2008].