Beginning in 2015, the United States Environmental Protection Agency’s (EPA’s) National Estuary Program (NEP) started a collaboration with partners in seven estuaries along the East Coast (Barnegat Bay; Casco Bay), West Coast (Santa Monica Bay; San Francisco Bay; Tillamook Bay), and the Gulf of Mexico (GOM) Coast (Tampa Bay; Mission-Aransas Estuary) of the United States to expand the use of autonomous monitoring of partial pressure of carbon dioxide (pCO2) and pH. Analysis of high-frequency (hourly to sub-hourly) coastal acidification data including pCO2, pH, temperature, salinity, and dissolved oxygen (DO) indicate that the sensors effectively captured key parameter measurements under challenging environmental conditions, allowing for an initial characterization of daily to seasonal trends in carbonate chemistry across a range of estuarine settings. Multi-year monitoring showed that across all water bodies temperature and pCO2 covaried, suggesting that pCO2 variability was governed, in part, by seasonal temperature changes with average pCO2 being lower in cooler, winter months and higher in warmer, summer months. Furthermore, the timing of seasonal shifts towards increasing (or decreasing) pCO2 varied by location and appears to be related to regional climate conditions. Specifically, pCO2 increases began earlier in the year in warmer water, lower latitude water bodies in the GOM (Tampa Bay; Mission-Aransas Estuary) as compared with cooler water, higher latitude water bodies in the northeast (Barnegat Bay; Casco Bay), and upwelling-influenced West Coast water bodies (Tillamook Bay; Santa Monica Bay; San Francisco Bay). Results suggest that both thermal and non-thermal influences are important drivers of pCO2 in Tampa Bay and Mission-Aransas Estuary. Conversely, non-thermal processes, most notably the biogeochemical structure of coastal upwelling, appear to be largely responsible for the observed pCO2 values in West Coast water bodies. The co-occurrence of high salinity, high pCO2, low DO, and low temperature water in Santa Monica Bay and San Francisco Bay characterize the coastal upwelling paradigm that is also evident in Tillamook Bay when upwelling dominates freshwater runoff and local processes. These data demonstrate that high-quality carbonate chemistry observations can be recorded from estuarine environments using autonomous sensors originally designed for open-ocean settings.

In fall 2010, the Environmental Protection Agency (EPA) sent information collection request (ICR) questionnaires to more than 600 regulated municipal separate storm sewer systems (MS4s) to help EPA collect information on MS4 program implementation. This ICR represents a comprehensive national data collection on implementation of the MS4 program. A total of 471 regulated MS4s responded to the questionnaires. This paper summarizes the MS4 ICR data, and discusses the results with key differences between Phase I (medium and large) MS4s and Phase II (small) MS4s. The ICR questionnaires primarily focused on post-construction standards and programs in order to collect data to support a potential EPA rulemaking that would address stormwater discharges from newly developed and redeveloped sites. The ICR also asked for information about other aspects of the MS4 program, including public education and involvement, illicit discharges, good housekeeping, retrofits, industrial sources and monitoring. The questionnaires results generally found a high level of implementation in many of the MS4 program areas.

In December 2003, the U.S. Environmental Protection Agency (EPA) published its WatershedBased National Pollutant Discharge Elimination System (NPDES) Permitting Implementation Guidance [EPA 833-B-03-004] and followed up with the Watershed-Based National Pollutant Discharge Elimination System (NPDES) Permitting Technical Guidance [EPA 833-B-07-004] in August 2007.These guidance documents consider a process for integrating the NPDES permitting program into a larger watershed management approach and coordinating NPDES activities with other water quality activities in the watershed. They describe a process of data collection and analysis conducted to support the development and issuance of NPDES permits that consider the diverse pollutant sources and stressors located within a defined geographic area (i.e., watershed boundaries). The conclusions reached through this watershed-based analytical approach lead to a broad range of possible NPDES or other program implementation options to achieve watershed goals. These options might extend beyond the traditional approach of developing and issuing a single NPDES permit to an individual point source discharger. The specific options and tools selected for the resulting NPDES watershed framework will depend on the characteristics of the watershed, the pollutants of concern, the sources of those pollutants, and the permitting context. One such tool is a watershed-based permit. Several permitting authorities have developed or considered a type of watershed-based permit, a multisource watershed-based permit, to address nutrient discharges within one or more watershed. This paper and presentation review the concepts of a watershed permitting analytical approach and an NPDES watershed framework as presented in EPA guidance. The presentation will highlight where Stakeholders are pursuing Watershed-based Permitting Approaches to control Nutrient Pollution and Storm water discharges.

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