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b) <br /> <br />*'C" j.:, t:l.', .... cot::,i::ficle~'~: of runoff and shall have the follow- <br />~_ng values: <br /> <br />2o <br />3. <br />4. <br />5. <br />6. <br />7. <br /> <br />Agricultual and park areas (no residential use) 0.20 <br />Single Family Residential 0.40' <br />Duplex and RG-25 Apartments 0.50 <br />RG-15 Apartments and Schools 0.60 <br />Commercial (light, prof. offices, etc.) 0.70 <br /> <br />Commercial (heavy, shopping centers) 0.80. <br />Industrial--these will be individually assigned to <br />each area depending on type and density of use. <br /> <br />c) <br /> <br />d) <br /> <br />!'I" is the intensity of rainfall in inches per hour and <br />shall be determined, for the yearly frequency specified <br />above, from the mean annual precipitation and unit <br />frequency/duration curves developed by ACFC and WCD <br />(curve attached and Appendix "A-i") corrected to the <br />proper mean annual precipitation value for Pleasanton <br />using the most recent Rainfall Distribution map of mean <br />seasonal rainfall in Alameda County prepared by ACFC and <br />WCD. The time of concentration shall be determined using <br />a 10 minute roof to gutter time plus that calculated for <br />flow in the system; or that calculated for overland flow <br />from the Overland Flow Chart shown in Appendix B plus that <br />calculated for flow in the system. <br /> <br />"A" is the area in acres contributing to the system. All <br />upstream tributary areas are to be considered as though <br />fully developed. <br /> <br />e) <br /> <br />Drainage calculation sheet marked Appendix A-2 shall be <br />used for all projects. <br /> <br />1-04 Pipe_Size.: <br /> <br />a) <br /> <br />Pipe sizes in integrated underground systems will normally be <br />determined in accordance wi~h Manning's Formula, <br />V = 1.5r 2/3s 1/2. The value of "n" shall be 0.013 for con- <br /> n <br />crete pipe and 0.024 for' corrugated metal pipe. Except <br />that for slopes above critical pipe size will be determined <br />by "entrance control." The value of "n" may be increased <br />at the discretion of the City Engineer for larger pipe sizes <br />(above 36"). <br /> <br />b) <br /> <br />Short culverts shall be designed in accordance with criteria <br />established in "California Culvert Practice" By State of <br />California, Division of Highways. <br /> <br />c) <br /> <br />The minimum size of pipe in the public right-of-way shall <br />be. twelve inches. <br /> <br />1-05 Velocity: All new storm drain mains shall be designed to maintain <br /> a minimum velocity of flow of two feet per second and a maximum <br /> velocity of 15 feet per second, when flowing full. <br /> <br /> <br />