Clean Water Services (CWS) has been continually releasing information and updates to their Hydromodification Base Strategy, as part of their updates to the Design and Construction Standards revising stormwater requirements to address the effects of hydromodification. Hydromodification is the alteration of land that results in changes to the timing and volume of stormwater runoff. An internal HBA workgroup recently met to review the draft document, which addresses management of runoff volume. Following the meeting, CWS released additional information and tools on the updated standards. The draft document builds on the existing CWS Design and Construction Standards and includes a variety of approaches for management of runoff volume such as stream enhancement, detention and LIDA, along with a selection methodology based on landscape setting, historic and anticipated development patterns, and project size and stream condition. The document and accompanying tools are intended to help applicants and other stakeholders identify which storm water management approaches and tools are expected to apply under the Base Strategy. Most recently, CWS provided additional examples of how to use the Base Strategy Methodology previously released, as well as an updated Hydromodification Planning Map tool. The last update also included a trial version of the Hydrological Simulation Program – Fortran (HSPF) interface tool with instructions, used to size flow duration curve matching ponds. The third roll out of information is expected this week, and will include language on the design criteria for some of the proposed stormwater management approaches. A complete draft of the Base Strategy and Methodology is expected by mid-February. The HBA’s internal workgroup will continue to review the draft methodology as it is released and work with CWS to provide feedback on the methodology. CWS encourages interested stakeholders to review and comment on this draft Base Strategy and Methodology document (PDF, 1.6MB).