Jared Ervin, PhD, Brandon Steets, PE, and Aaron Poresky, PE, coauthored “Municipal Separate Storm Sewer System (MS4) Dry Weather Flows and Potential Flow Sources as Assessed by Conventional and Advanced Bacterial Analyses” in the Journal Environmental Pollution, Volume 337, on November 15, 2023.

Jared was the study lead for Geosyntec, and Brandon and Aaron were coauthors. Their collaborators and coauthors were Dong Li, Laurie C. Van De Werfhorst, Jen Smith, and Patricia A. Holden from the University of California, Santa Barbara, along with Cindy Rivers and Grant Sharp from Orange County Public Works. This organization also provided funding for the study.

Jared is a Senior Professional based in California with more than 12 years of experience in pollutant source tracking and the use of advanced forensic tools to support TMDL compliance and improve water quality in stormwater and surface water nationwide.

Brandon is a Senior Principal based in California with more than 22 years of experience focused on NPDES and TMDL regulations, pollutant source investigation, watershed water quality modeling, and green infrastructure design.

Aaron is a Principal based in Oregon with more than 17 years of professional experience focused on water resource planning and analysis; stormwater BMP selection and design; hydrologic, hydraulic, and water quality modeling; and stormwater asset management.

Environmental Pollution is an international, peer-reviewed journal that publishes high-quality research papers and review articles about all aspects of environmental pollution and its effects on ecosystems and human health. The journal welcomes process-oriented and hypothesis-based submissions that report results from original and novel research and contribute new knowledge to help address problems related to environmental pollution at regional and global scales.

Municipal separate storm sewer systems (MS4s) function in urbanized areas to convey flows during both wet weather (i.e., stormwater) and dry weather (i.e., urban runoff as well as subsurface sources of flow) to receiving waters. While urban stormwater is known to contain microbial and chemical pollutants, MS4 dry weather flows, or non-stormwater discharges (NSWDs), are much less studied, although they are also known to contain pollutants, especially when these flows include raw sewage. In addition, some natural NSWDs (e.g., from groundwater infiltrating MS4 pipes) are critical for aquatic habitat protection. Thus, it is important to distinguish NSWD sources to prevent non-natural flows while retaining natural waters (i.e., groundwater). Here, MS4 dry weather flows were assessed by analyzing water samples from MS4 outfalls across multiple watersheds and water provider service areas in south Orange County, California; potential NSWD sources including sewage, recycled water, potable water, and groundwater were sampled and analyzed for their likely contributions to overall NSWDs. Geochemical and microbiological water quality indicators, as well as bacterial communities, differed across NSWDs, yet water quality within most locations did not vary significantly diurnally or by sampling date. Meanwhile, NSWD source waters had distinctly different bacterial taxa abundances and specific bacterial genera. Shared geochemical and microbial characteristics of certain sources and outfall flows suggested the contributions of sources to outfall flows. The average proportions by sources contributing to MS4 outfalls were further estimated by SourceTracker and FEAST, respectively. The results of this study highlight the use of multiple tools when assessing chemical and microbiological water quality to predict sources of NSWDs contributing to urban MS4 flows during dry weather. This information can be used to support management actions to reduce unnatural and high risk sources of dry weather drainage while preserving natural sources important to environmental health in downstream receiving waters.

More Information

Download the full article here: Municipal separate storm sewer system (MS4) dry weather flows and potential flow sources as assessed by conventional and advanced bacterial analyses – ScienceDirect
Learn more about the organization: Environmental Pollution | Journal | ScienceDirect.com by Elsevier
For consultation regarding bacterial analyses in MS4s, contact Brandon at bsteets@geosyntec.com or Jared at jervin@geosyntec.com
Learn more about Jared at Jared Ervin | LinkedIn
Learn more about Brandon at Brandon Steets | LinkedIn
Learn more about Aaron at Aaron Poresky | LinkedIn