3_Exhibit B - Laserfiche WebLink

City of Pleasanton (0012384.00) 1 Woodard & Curran, Inc. Stoneridge Residential Sewer Impact Study December 9, 2022 TECHNICAL MEMORANDUM TO: Michael Stella, City of Pleasanton PREPARED BY: Chris van Lienden, CA PE No. 75034 REVIEWED BY: Gisa Ju, CA PE No. C31823 DATE: December 9, 2022 RE: Stoneridge Residential Sewer Impact Study 1. INTRODUCTION The purpose of this Technical Memorandum is to analyze the capacity of sewers impacted by a proposed development of a 6.0 acre property at 1008 Stoneridge Mall Road, which currently has parking for the Stoneridge Mall at the proposed development location. The proposed development would include approximately 360 multi-family residential units. The City of Petaluma (City) has requested that Woodard & Curran perform a review of potential impacts of the proposed development on the City’s sewer syst em. A description of the proposed development and the preliminary utility plan has been included in Appendix A. The City has requested that Woodard & Curran perform a review of potential impacts of the proposed development on the City’s sewer system. A description of the proposed development and the preliminary utility plan has been included in Appendix A. The City’s current sewer system model was developed in H2Omap Sewer as part of the City’s 2007 Wastewater Master Plan. Existing flows for this model were based on water consumption data from billing records in 2002 and 2003, and calibrated to flow monitoring data collected in February 2004. Future loads were estimated based on an inventory of vacant and future annexation parcels with future la nd use designations as provided by the City, and associated flow factors based on average data. The report documents a dwelling unit equivalent flowrate of 220 gpd/unit. Alternative rates for multi-family parcels were not identified. Based on review of the specific future developments identified in the 2007 Wastewater Master Plan, parcels with a commercial land use had an assumed average flow factor of approximately 0.11 gpd per square foot. While the report does include a list of proposed developments, clear documentation of existing and future flows allocated to each parcel is not available. In 2013, the model was converted to InfoSWMM, and the portion of the system tributary to East Amador Trunk Sewer was recalibrated using dry weather flow monitoring data collected over a 2 week period from April 25 to May 13, 2012, though the effort did not include updating the source loading data. The City is currently in the process of developing an updated sewer model based on current water usage data and land use projections. However, the model is still in development and not expected to be completed until mid-2023. Therefore, the City’s current model (2013 model) was used for this evaluation, along with the design storm and capacity criteria identified in that repor t.