Chapter 19.04
DESIGN AND CONSTRUCTION STANDARDS FOR STORM SEWERS1
Sections:
19.04.010 Standards.
19.04.020 General requirements.
19.04.030 Minimum planning/design standards.
19.04.040 Materials.
19.04.050 Methods of construction.
19.04.060 Standard details.
19.04.070 Approval of materials.
19.04.010 Standards.
Per NBMC 14.16.060, the current edition of the King County Surface Water Design Manual as now in effect or subsequently amended is adopted for the design and construction standards for storm sewers. (Ord. 1305 § 1, Exh. A (part), 2008: Ord. 843 § 42, 1991).
19.04.020 General requirements.
A. The public works director and/or city engineer have sole discretion to modify minimum standards listed in this chapter.
B. Use of infiltration facilities shall be used where sufficient permeable soil exists to allow construction of a properly functioning infiltration facility, unless otherwise determined by a hydrogeological report from a professional engineer licensed in the state of Washington.
C. Maintenance requirements for private and public stormwater facilities are found in Appendix A of the King County Surface Water Design Manual.
D. See Chapter 14.16 NBMC for additional stormwater management regulations.
E. The city encourages the use of low impact design for the purpose of reducing stormwater quantity and quality impacts through low impact design techniques. Some of these techniques may include:
1. Maximizing retention of native forest cover and restoring disturbed vegetation to intercept, evaporate, and transpire precipitation.
2. Preserve permeable, native soil and enhance disturbed soils to store and infiltrate storm flows.
3. Retain and incorporate topographic features that slow, store, and infiltrate stormwater.
4. Retain and incorporate natural drainage features and patterns.
5. Locate buildings and roads away from critical areas and soils that provide effective infiltration.
6. Minimize total impervious area and eliminate effective impervious surfaces.
7. Manage stormwater as close to its origin as possible to utilize small scale, distributed hydrologic controls.
8. Create a hydrologically rough landscape that slows storm flows and increases the time of concentration. Increase reliability of the stormwater management system by providing multiple or redundant points of control.
9. Integrate stormwater controls into the development design and utilize the controls as amenities; create a multifunctional landscape. (Ord. 1305 § 1, Exh. A (part), 2008).
19.04.030 Minimum planning/design standards.
See King County Surface Water Design Manual for:
A. Drainage review and requirements;
B. Drainage plan submittals (make consistent with NBMC 19.01.800);
C. Hydrologic analysis and design;
D. Conveyance system analysis and design;
E. Flow control design;
F. Water quality design. (Ord. 1305 § 1, Exh. A (part), 2008).
19.04.040 Materials.
Materials shall meet requirements of Division 9 of the materials section of the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction, except as specifically noted in this chapter. (Ord. 1305 § 1, Exh. A (part), 2008).
19.04.050 Methods of construction.
Follow WSDOT Construction Manual and Construction Requirements set forth in WSDOT Standard Specifications for Road, Bridge, and Municipal Construction. (Ord. 1305 § 1, Exh. A (part), 2008).
19.04.060 Standard details.
See the King County Surface Water Design Manual for standard plans and details; where plans do not exist see WSDOT Standard Plans Section B: Drainage Structures and Hydraulics. (Ord. 1305 § 1, Exh. A (part), 2008).
19.04.070 Approval of materials.
Approval shall be obtained from the city engineer for the use of materials specified in NBMC 19.04.040. Such approval shall be obtained through the submission of record of material (ROM) and request for approval of material (RAM) forms available from the public works department or the Washington State Department of Transportation. Approval shall be obtained prior to installation of the materials. (Ord. 1305 § 1, Exh. A (part), 2008).
Prior legislation: Ord. 720 §§ 37–48.