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SUBDIVISION <br /> - <br /> !� � R, <br /> 4. Detention pond bottoms must be vegetated. J. Permit Required.No person, individual, partnership,firm or <br /> corporation shall deepen,widen,fill, reclaim, reroute or change <br /> G. Waiver of Detention/Retention. the course or location of any existing ditch, channel, stream or <br /> 1. Detention/retention may be waived for the following if drainage without first obtaining a site permit and permits from <br /> no adverse impacts are demonstrated through drainage applicable agencies (such as FEMA or the U.S.Army Corps of <br /> analysis and a payment-in-lieu is made into the Engineers) having jurisdiction.The Responsible Official may, <br /> stormwater management fund in accordance with Section at his or her discretion, require preparation and submission of <br /> 6.1.1.3. a FEMA or flood study for a proposed development if there are <br /> concerns regarding storm drainage on the subject property or <br /> a. Non-residential small site permits, upstream or downstream from the subject property.The costs <br /> b. Developments within High Intensity Zones,and of such study, if required, shall be borne by the developer. <br /> K. Conformance with the City's Stormwater Technical <br /> c. Plats of four(4) lots or less where the lots subdivided Manual.All stormwater facilities, including those for low <br /> from the parent parcel do not exceed 0.5 acres each, impact development,detention, retention or water quality, <br /> are restricted by zoning or deed to 60%impervious shall be designed by a licensed professional engineer in <br /> cover or less, and are served by an existing street.An accordance with the City's stormwater Technical Manual, <br /> exemption is not allowed for the submittal of a series including requirements for location, screening and fencing <br /> of plats of four(4) lots or less with the intention of not inconsistent with this Chapter and applicable ordinances. <br /> producing a tract that is greater than four(4) lots. All plans submitted to the Responsible Official for approval <br /> 2. Detention/Retention may be waived in High Intensity shall include a layout of the stormwater management system <br /> Zones if no adverse impacts are demonstrated through together with supporting calculations for the design of the <br /> drainage analysis and a payment-in-lieu is made into the system. <br /> stormwater management fund in accordance with Section Section 3.9.1.2Velocity Attenuation and Surface Drainage <br /> 6.1.1.3. Channels <br /> (Ord. No. 2020-60,9-1-2020) A. Surface Drainage Channels.Surface drainage channels <br /> H. Street Drainage.Except for inverted crown thoroughfares, no constructed or altered for drainage purposes shall be designed <br /> lowering of the standard height of street crown shall be allowed to minimize potential erosion and to increase the bottom width <br /> for the purposes of obtaining additional hydraulic capacity. to flow depth ratio as follows: <br /> Bridges and culverts in residential streets, shall be designed 1. Channel cross sections shall be trapezoidal in <br /> for the runoff from the one hundred (100)year frequency configuration; <br /> flow based on a fully developed watershed.shall not produce <br /> a headwater depth at the roadway greater than either twelve 2. Side slopes of channels shall be no steeper than four <br /> (12) inches above the roadway crown or any top of upstream horizontal to one vertical; and <br /> curb elevation,whichever is lower. For bridges and culverts <br /> in streets other than residential areas,the one hundred (100) 3. All constructed and altered drainage channels shall be <br /> year headwater depth is limited to six(6) inches. Storm drain stabilized and vegetated as soon as practicable after final <br /> system shall be designed to meet the criteria listed in the grading. <br /> Stormwater Technical Manual. 4. Channel velocities shall be non-erosive. <br /> I. Minimize Cut and Fill.The layout of the street network, lots B. Additional runoff velocity attenuation strategies and techniques <br /> and building sites shall minimize the amount of cut and fill on detailed in the City of San Marcos Stormwater Technical <br /> slopes in accordance with the standards for cut and fill set Manual shall be utilized. <br /> forth in Section 6.1.2.2. <br /> Amended: September 1, 2020 San Marcos Development Code 3:59 <br />