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SITE I&ROVEMENT PLAN DRAINAGE REQUIREMENTS • New development shall provide for all of the storm water runoff that is generated. The use of roadside ditches or gutters are not allowed. • All existing development shall provide for the additional storm water runoff that is generated in accordance with current design standards. • The Improvement Plan shall show the location of existing and proposed storm drainage facilities (check with Engineering staff regarding design criteria). If subject to flooding, the 100-year flood elevations must be shown. Indicate any unusual topographic features of the site (e. g. contours, steep slopes, or drainage courses). • All developments shall provide terminal drainage where the development is within close proximity (see chapter 9-1135 of the County Development Title)to terminal drainage facilities. "Terminal drainage" means a storm drainage system which by gravity carries storm water ultimately to the ocean. • When terminal drainage is not readily available, storm drainage/additional run-off shall be retained on-site, and provisions shall be shown on the Improvement Plan. • Retention ponds are drainage ponds with no outlet facilities for terminal drainage. They must be designed to be capable of storing the required volume and of emptying through percolation and evaporation over a specified time. If applicable, pond capacity calculations shall be submitted for approval (see attached calculation form for retention ponds). • If retention ponds are to be used in combination with other uses in addition to storm water runoff(e.g. dairy farms), then calculations shall be provided to show that the ponds are sufficiently sized for both uses (Refer to handout entitled "Drainage Requirements- Dairy Farms"). F:\DEVSVC\Planning Application Forms\Site Improvement Plan. Page 5 of 9 (Revised 5-11-09)