San Marcos Development Code 9.1.2020

3 C H A P T E R

Subdivisions

Section 3.9.1.3Impervious Cover Calculation and Limitations Paved roads, sidewalks, parking areas, parking lots, buildings and other impermeable construction covering the natural land surface shall be considered impervious cover. The methods to be used to calculate the percent of impervious cover created by the development of a parcel or tract of land are described in the City Stormwater Technical Manual. Note that the area of impervious cover for a surface may be reduced based on data acceptable to the Responsible Official showing that the surface has a significant degree of permeability. Section 3.9.1.4Erosion Prevention and Highly Erodible Soils. Erosion prevention and restoration measures detailed in the City Stormwater Technical Manual shall be utilized to attain nature mimicking drainage objectives. Refer to the Technical Manual for a list of local soils that have a high potential for erosion based on Soil Conservation Service data. Section 3.9.1.5Drainage Requirements During Construction During construction, on-site drainage shall be maintained so that water surfaces are not increased upstream or downstream of the site when compared to pre-project conditions unless fully contained within a drainage easement or designated right-of-way. Section 3.9.1.6Drainage Improvement Responsibility A. Drainage improvements required by this Article shall be provided at the sole expense of the owner of the property to be developed, unless otherwise expressly provided to the contrary in a subdivision improvements agreement. B. Drainage easements shall be provided to the public by the owner of property to be developed for the purposes of drainage master planning of all drainage improvements, open or enclosed, and all storm water flows to the limits of the one hundred (100) year floodplain as determined in accordance with anticipated fully-developed contributing area land use conditions and allowing continuous access for inspection, operation, maintenance and rehabilitation of all drainage improvements.

C. At the discretion of the Responsible Official, the owner of the property to be developed shall dedicate drainage improvements to the public in a right-of-way rather than a drainage easement. D. In determining whether drainage improvements should be dedicated to the public, the Responsible Official shall take the following factors into consideration: 1. Drainage improvements associated with a single development shall remain private; and 2. Drainage improvements that serve streets or other public property or may serve multiple developments or provide regional detention/treatment shall be dedicated to the public. E. Drainage easement and right-of-way widths shall be specified by the City as necessary for inspection and maintenance of facilities as well as to accommodate areas anticipated to be inundated by stormwater. F. Full detention basin design may be deferred until the site development permit stage if the property owner submits a “request for detention deferral” demonstrating an understanding of the implications of such design deferral AND the following notes are placed on the subdivision plat AND supporting documentation is provided. 1. “Stormwater detention is required for this property. The engineer of record for this subdivision plat has estimated that an area of approximately ____________ acres and a volume of approximately ____________ acre feet will be required for this use. This is an estimate only and detailed analysis may reveal different requirements.” 2. “No building permit shall be issued for this platted property until a stormwater detention system design has been approved by the City of San Marcos or applicable county if in the ETJ.”

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San Marcos Development Code Amended: September 1, 2020