Res 2017-126/approving an Agreement between Tetra Tech, Inc. of San Antonio, Texas and the City of San Marcos for Professional Engineering Services to update the City’s Storm Water Technical Manual and Low Impact Development Technical Appendix

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Attachment A Scope of Services 1.0 Introduction The following is a proposed approach for Tetra Tech to support the City of San Marcos (City) in the update of the Stormwater Technical Manual (STM) and first steps to development of a comprehensive Low Impact Development(LID) Technical Appendix. The LID Technical Appendix will incorporate relevant information from the San Marcos Green Infrastructure—LID Practices document but also expand the information to create a planning and design tool for three commonly used Stormwater Control Measures (SCM). The STM will incorporate guidance from TxDOT, Austin, and San Antonio's latest hydraulic and hydrology design procedures to clarify technical approaches that designers should use to properly analyze and design stormwater infrastructure and control measures. The integrated stormwater management guidance will instruct users on the proper selection, design, and maintenance of low impact development SCMs. The manual will identify SCMs that are best suited for San Marcos and will incorporate performance criteria proposed in revisions to CodeSMTX Chapter 6— Environmental Regulations. The performance criteria are intended to meet water quality targets and planning goals, including existing or future Total Maximum Daily Loads (TMDLs). Without the specific regulatory drivers for LID in San Marcos, quality of life benefits are vitally important for LID implementation. Therefore, the LID guidance will make every effort to highlight the multiple benefits of LID to promote implementation, as well as provide placeholders for future efforts for potential quantification of these benefits based on Triple Bottom Line procedures. The City has promoted the implementation and use of LID stormwater management techniques through many different initiatives. The City recognizes the important role that LID will play in stormwater program management and implementation of the Comprehensive Plan to meet program objectives and regulatory requirements. In order to adequately contribute to the protection of local water resources, structural SCMs must be designed and maintained to a manageable and effective standard. Thus the LID guidance will need to accomplish three key objectives: 1. Provide relevant examples of the SCM design process 2. Create a SCM selection matrix to guide decision making on choosing the appropriate SCMs for projects. 3. Provide technical design guidance for multiple SCM types. 2.0 Technical Approach The following tasks summarize the Tetra Tech approach to completing the work outlined in the introduction. 12