A. All tentative plats and development plans shall show proposed grading and improvements for areas that are subject to flooding or which have drainage problems, and shall also show a description and location of all facilities proposed to alleviate flooding or drainage problems within or outside the boundaries of the subdivision or development.
B. All development plans and tentative plats shall be accompanied by conceptual grading plans and conceptual drainage improvement plans, as needed, to demonstrate:
1. The methods for flood proofing and/or drainage control for the development, including sufficient lot grading information to demonstrate adequate finished pad elevations and/or drainage slopes and paths to guide water away from structures and protect building foundations including all structures within zones A, AE, AO, AH and Shaded X;
2. That improvements are compatible with the existing upstream and downstream drainage conditions and that any proposed grading and/or grade change will not have an adverse impact on surrounding properties;
3. When development is proposed to encroach into a regulatory floodplain or is completely surrounded by floodwaters, maximum encroachment limits shall be shown;
4. The methods of erosion and sediment control during construction and post construction; and
5. The methods of mitigating increased urban peak and volumetric flood water runoff or discharge on downstream properties created as a result of the development.
C. A floodplain use permit is required prior to commencement of any site improvements or grading associated with a subdivision development as a whole or for individual lot(s) within the subdivision. A grading plan must be submitted to the district for review and approval. Detailed improvement plans for storm drains or channel improvements must also be submitted to the same department for review and approval. Where a grading plan or detailed drainage improvement plans are not provided, the Chief Engineer may require additional information and engineering plans prior to issuing a floodplain use permit. Certifications of elevation shall be required pursuant to 16.20.070, until the LOMR is approved by FEMA.
D. Drainage and grading improvements that are required to mitigate off-site adverse impacts of the proposed development shall be constructed, and as-built plans prepared and submitted to the district. The as-built plans require the district's approval prior to the issuance of any building permits, except for model home permits and any permits necessary to build the drainage infrastructure.
E. Drainage and grading improvements that are required to mitigate on-site impacts shall be constructed, and as-built plans prepared and submitted to the district. The as-built plans require the district's approval prior to the final release of assurances for subdivisions, and prior to the issuance of the certificate of occupancy for development plans.
F. All on-site and off-site grading and construction shall comply with the federal Clean Water Act including providing construction and post-construction controls for storm water quality.
(Ord. 2010-FC5 § 1 (part), 2010; Ord. 2005 FC-2 § 2 (part), 2005, Ord. 1999 FC-1 § 1 (part), 1999; Ord. 1988 FC-2 Art. 11 (B) (2), (3), (4), 1988)