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As of November December 84, 2019 2025 <br /> Page 1 of 3 <br /> <br />Drainage Guidelines for Residential Developments <br />Small Projects <br />Stormwater Detention <br /> <br />City of Redwood City <br />Engineering Divisionand Transportation Department <br /> <br />General Requirements <br />A. A Grading and Drainage Plan must be submitted with Building Permit applications for all new single <br />family residencesResidential Small Projects and additions associated with single Residential Small <br />Projectsfamily residences. Residential Small Projects are Residential Developments with less than 4 <br />units and less than 10,000 square feet of impervious surface. This plan shall be a separate sheet <br />included with the Building Permit submittal and must be prepared by a qualified licensed engineer (or <br />architect when allowed by City Engineer) and be signed by the same. <br /> <br />B. New Residential Small Projects with less than 4 units and less than 10,000 square feetsingle family <br />residences are required to implement permanent stormwater quality control measures per the GI <br />Development Guidelines. All projects shall provide site design measures where practical. Acceptable <br />site design measures include measures a-f on Attachment R2. <br /> <br />C. The goal of the drainage design is to maintain post-development storm water runoff to pre-development <br />runoff conditions, especially when existing drainage flows onto neighboring properties. (Roof Drains to <br />pervious areas, vegetative filters, grassed swales and infiltrative landscaping) <br /> <br />D. Use Post-Construction, Best Management Practices (BMP’s) with the best technology available as <br />appropriate to control runoff. (See “Blueprint for a Clean Bay”) <br /> <br />E. Designers are encouraged to use porous paving systems for driveways , walkways, and patios to reduce <br />the effect of contaminant runoff. <br /> <br />F. The use of dry wells is not allowed in the City of Redwood City. <br /> <br />G. The use of curb drains is not allowed in the design of grading and drainage plan. <br /> <br /> Design Criteria <br />A. Refer to Part II of the Engineering Standards Design Criteria for requirements of a grading and drainage <br />plan. <br /> <br />B. If fill is to be added adjacent to the property lines, grades on neighboring properties will need to be <br />obtained to document any potential impacts to these properties. Site grading shall not impede existing <br />drainage from adjacent properties. <br /> <br />C. Design the drainage for sheet flow to lawn or pervious landscaped areas of the site, in lieu of area drains <br />and pipe collection systems, wherever possible without creating unintended ponding and erosion. <br /> <br />D. Show where the roof downspouts are located. These downspouts should direct to approved splash <br />blocks (minimum 2 feet long) that deflect the water away from the building. Show (with arrows) how the <br />water is proposed to move away from the splash blocks. <br /> <br />E. If a basement is proposed for the project, a drainage plan for a separate subgrade drainage system must <br />be included in this plan. This should also include the method of outlet, and is not to connect sub drain to <br />surface storm drain piping. <br /> <br />7.A. - Page 43 of 121 <br />49