Chapter 15.78
DRAINAGE, EROSION CONTROL, AND STORMWATER MANAGEMENT
Sections:
15.78.010 Land alteration and surface water control chapter adopted by reference.
15.78.020 Natural drainage system utilized to extent feasible.
15.78.030 Developments must drain properly.
15.78.040 Stormwater management.
15.78.050 Erosion control and sedimentation.
15.78.060 Stormwater system design.
15.78.070 Illegal discharge of materials into the stormwater system.
15.78.010 Land alteration and surface water control chapter adopted by reference.
A. Chapter 13.30 SBMC, Land Alteration and Surface Water Control, as it now exists or will later be amended, is hereby adopted by this reference as part of this title.
B. Chapter 13.30 SBMC establishes development standards regulating land alteration activities and surface water control, establishes a permit process and fees, and provides penalties for violations of the chapter.
C. All development (unless exempted) must be in compliance with Chapter 13.30 SBMC, as well as the provisions of this title. (Ord. 1222 § 1, 1997).
15.78.020 Natural drainage system utilized to extent feasible.
A. To the extent practicable, all development must conform to the natural contours of the land and natural and pre-existing human-made drainage ways must remain undisturbed.
B. To the extent practicable, lot boundaries must coincide with natural and pre-existing human-made drainage ways within subdivisions to avoid the creation of lots that can be built upon only by altering such drainage ways. (Ord. 1222 § 1, 1997).
15.78.030 Developments must drain properly.
A. All developments must be provided with a drainage system that is adequate to prevent the undue detention or retention of surface water on the development site. Surface water will not be regarded as unduly detained or retained if:
1. The detention or retention results from a technique, practice or device deliberately installed as part of an approved sedimentation or stormwater runoff control plan; or
2. The detention or retention is not substantially different in location or degree than that experienced by the development site in its predevelopment state, unless such detention or retention presents a danger to health or safety.
B. No surface water may be channeled or directed into a sewer line.
C. Whenever practicable, the drainage system of a development must coordinate with and connect to the drainage systems or drainage ways on surrounding properties or streets.
D. Drainage swales must be constructed in accordance with the standards listed in SBMC 15.76.260. (Ord. 1222 § 1, 1997).
15.78.040 Stormwater management.
All developments must be constructed and maintained so that adjacent properties are not unreasonably burdened with surface waters as a result of the developments. More specifically:
A. No development may be constructed or maintained so that the development unreasonably impedes the natural flow of water from higher adjacent properties across the development, resulting in substantial damage to the higher adjacent properties; and
B. No development may be constructed or maintained so that surface waters from the development are unreasonably collected and channeled onto lower adjacent properties, resulting in a volume and/or rate that is substantially greater than the predevelopment volume and/or rate. (Ord. 1222 § 1, 1997).
15.78.050 Erosion control and sedimentation.
A. Erosion control and water quality control facilities for projects that disturb over five acres must apply to the State Department of Ecology for an NPDES permit.
B. Erosion control plans are required as a component of the site plan for all plats and all projects which require site plan review. Erosion control plans may include practices such as using straw bales, hydroseeding, etc.
C. Development of the land may not begin (and no building permits may be issued) until the city supervisor approves the erosion control plan.
D. For purposes of this section, “disturb” means any use of the land by any person in any development, and/or road construction and maintenance that results in a change in the natural cover or topography that may cause or contribute to sedimentation. Sedimentation occurs whenever solid particulate matter, mineral or organic, is transported by water, air, gravity, or ice from the site of its origin. (Ord. 1222 § 1, 1997).
15.78.060 Stormwater system design.
A. Storm sewers constructed within the street will be sized by the developer’s engineer and will consider all potential runoff requirements within the site and upstream of the site.
1. The storm sewer will be sized for a 100-year design recurrence criteria for storm drainage facilities.
2. The minimum size of storm sewers is eight inches in diameter.
3. Spacing of catch basins along the street must conform to published engineering recommendations, which consider profile of the street and street width.
B. On-site detention may be required for new development where downstream deficiencies exist or are anticipated to exist in the next five years. Development that will be less than 5,000 square feet of impervious surface is exempt from detention requirements. The square footage considers the total development of the property including the future potential impervious surface. Recommended design recurrence criteria for a commercial or residential storm drainage detention facility is a 10-year interval. (Ord. 1222 § 1, 1997).
15.78.070 Illegal discharge of materials into the stormwater system.
The discharge of any material other than stormwater into the stormwater system is prohibited. (Ord. 1222 § 1, 1997).