Hydrology calculations shall show points of concentration, area (sub-areas and cumulative area), soil type, time of concentration, rainfall zone/intensity. percent impervious, subarea runoff, total runoff, conveyance facility size, length, slope, flowline used in the calculations and other characteristics.
Additionally, detention, retarding and retention basin design calculations shall be submitted.
Plan of the proposed road system with grades and typical street cross-sections.
Hydrology calculations. Hydrology calculations will be stamped and signed by a registered civil engineer.
Two copies of the above will be submitted in the form of a report.
A preliminary drainage study shall be submitted to the City at the time of Tentative Map submittal. The submittal shall be in the form of a report, including drainage maps.
At this stage, runoff rates may be estimated using Figures V-5, V-6, and V-7. Retarding and detention basin volumes may be assumed as one acre foot for each 10 acres of single family residential land use and 1 acre-foot for each 5 acres of multi-family residential, commercial and industrial land uses. Retention basin volumes will be determined using Figure V-9.
It must be understood that the requirements for this stage may result in facilities sized smaller than those based on detailed hydrologic studies described in Sections V.B.1 through V.B.4. Approval of a Tentative Map based on the requirements of Section V.B.5 will in no way represent approval of the final drainage design. The final drainage facilities will be designed per the requirements of V.B.1 through V.B.4.
V-4