Chapter 12.54
BRIDGES AND DRAINAGE STRUCTURES
Sections:
12.54.040 Existing bridges and drainage structures.
12.54.010 Design standards.
A. All culvert pipe, box culverts, and bridges shall conform to the following:
1. AASHTO Standard Specifications for Highway Bridges, latest edition and applicable interim versions.
2. WSDOT, Standard Specifications for Road and Bridge Construction, latest edition.
3. WSDOT, Bridge Design Manual, latest edition.
4. WSDOT, Bridge Detailing Manual, latest edition.
B. A hydraulic analysis shall be performed for all culverts, open channels and box culverts in accordance with the WSDOT Hydraulics Manual. Such drainage structures shall be sized and located as per the analysis; provided, however, that no cross culvert shall be less than eighteen inches in diameter.
C. All bridges shall be constructed of reinforced concrete. Spans may be pre- or post-tensioned concrete girders or beams with a concrete deck. Steel or other metal bridges may be used only with the approval of the county engineer. Treated timber bridges may be used on private roads only.
D. Bridge clear width shall accommodate the full width of the traveled lanes, parking lanes and shoulders of approach roads. Bikeway and pedestrian walkways shall be provided where required.
E. All roadway structures must be designed in accordance with the minimum standards contained within the current edition of the WSDOT Bridge Design Manual. However, new bridges on private roads may be designed for HS20 loadings and a minimum width equal to the traveled way plus two feet. New bridges serving exempt private roads are exempt from county road standards, but shall require a building permit.
F. All box culverts and bridges shall have the year of construction permanently indentured on the downstream headwall face in legible numbers. The numbers shall be three inches high by one and one-half inches wide by approximately three-eighths inches deep in the headwall face.
G. All box culvert, pipe arch, structural plate culverts and bridge designs shall be done by a registered professional structural engineer licensed in the state of Washington. The complete design of the structure shall be submitted to the county engineer for approval.
H. Foundation designs shall be based upon the recommendations of a qualified geotechnical engineer and shall include a scour analysis for the protection of existing streambed and footing elevations. These recommendations shall be documented in the geotechnical report which shall accompany the bridge design documents.
I. A new structure shall not create a backwater elevation rise of more than one foot. The bottom of the superstructure of bridges shall be a minimum of three feet above the one-hundred-year flood elevation.
J. Various permits may be required and are the responsibility of the applicant. Such permits may include, but are not limited to, the following:
1. Bridges over navigable waters require U.S. Coast Guard permits.
2. Bridges involving deposition of material in waters of the United States or their adjacent wetlands require a U.S. Army Corps of Engineers permit.
3. Any work involving alteration of flow or bed materials below the ordinary high water line of any water body or watercourse requires a hydraulic project approval from the State Department of Fish and Wildlife.
4. Any project requiring a U.S. Army Corps of Engineers permit also requires a water quality certification from the State Department of Ecology.
5. Bridges across streams in state flood control zones require a permit from the State Department of Ecology.
6. Where bridge structures lie on or over submerged lands, a lease from the Washington State Department of Natural Resources may be necessary.
7. Structures located on shoreline zones as defined in the Douglas County Shoreline Master Program require a substantial development permit from Douglas County, subject to concurrence of the State Department of Ecology.
8. Structures in critical areas as defined in DCC Title 19 require critical area permits from Douglas County. (Ord. TLS 09-11-49E (Exh. B) (part): Ord. TLS 07-04-30B Exh. B (part): Ord. TLS 04-02-30B Exh. A (part))
12.54.020 Inspections.
The developer and his engineer are responsible for inspection, quality control and sufficiency of the completed structure subject to approval by the county engineer. All materials and testing thereof shall conform to the current edition of the WSDOT Standard Specifications. Prior to construction, the county engineer shall review with the developer’s engineer the required inspections and documentation required. (Ord. TLS 09-11-49E (Exh. B) (part): Ord. TLS 07-04-30B Exh. B (part): Ord. TLS 04-02-30B Exh. A (part))
12.54.030 As-built plans.
Upon completion and acceptance of any box culvert or bridge built under these standards, a complete set of as-built plans shall be furnished to the county engineer. See DCC Section 12.55.060 for further guidance. (Ord. TLS 09-11-49E (Exh. B) (part): Ord. TLS 07-04-30B Exh. B (part): Ord. TLS 04-02-30B Exh. A (part))
12.54.040 Existing bridges and drainage structures.
A. Prior to any land division approval and as directed by the county engineer, an inspection of existing bridges and drainage structures within the boundaries of the development shall be conducted by a licensed professional structural engineer knowledgeable of bridge design, construction and load ratings. The engineer shall submit a report indicating the condition of the existing bridge as to the requirements set forth in these standards in regards to load function, superstructure and abutments.
B. Existing bridges and drainage structures within the boundaries of the development that do not meet the standards of this section shall be replaced with new bridges and drainage structures or the existing bridges and drainage structures shall be modified as necessary.
C. Should the development review process identify off-site locations where the existing roads must be widened or realigned as a condition of development approval (see DCC Section 12.50.150), all affected bridges and drainage structures shall be evaluated in the same manner as for those within the boundaries of and fronting the development. All necessary widenings, extensions or replacements necessary to accommodate the new roadway width or alignment and meeting both the structural and hydraulic adequacy as set forth herein shall be designed as set forth in DCC Section 12.54.010. (Ord. TLS 09-11-49E (Exh. B) (part): Ord. TLS 07-04-30B Exh. B (part): Ord. TLS 04-02-30B Exh. A (part))