altaStation: Assessing Urban Drainage Systems with Sight and Sound

Introduction The development of an innovative, conveyance system flow monitoring technology is changing the established paradigm for the assessment and control of urban drainage and wastewater collection infrastructure. The 'altaStation' uses listening and imaging to assess the capacity and condition of stormwater and wastewater conveyance systems using a synchronized, wide-area approach that allows for long-term, affordable, system monitoring. By deploying altaStations throughout a system, sub-system or neighborhood, any significant rainfall event can be used as a 'drainage infrastructure system stress test' to assess the health of the system and isolate problem areas for further investigation and remediation. Urbanalta/U.S. EPA Collaboration In March 2013, the U.S. Environmental Protection Agency (U.S. EPA) published it's 'Blueprint for Integrating Technology Innovation into the National Water Program (U.S. EPA, 2013).' In this document, U.S. EPA established a goal to partner with stakeholders to speed the design, development and deployment of the next generation for environmental technologies, including sensor-based systems. In early 2014, the U.S. EPA's Office of Research and Development and a Cincinnati, Ohio based technology development company, Urbanalta, executed a cooperative research and development agreement to work together to develop an innovative flow monitoring device. This collaborative effort resulted in the creation of the 'altaStation,' a digital sound measurement and imaging system for area-wide drainage monitoring, assessment and control. To support the needs of this U.S. EPA-Urbanalta research and technology development project, a unique stormwater and wastewater infrastructure monitoring (SWIM) simulation system, referred to as the 'SWIM Test Bed,' was designed and constructed in the U.S. EPA's Test and Evaluation Facility in Cincinnati, OH (Figure 1). altaStation The altaStation applies it's 'Sight&Sound' technology to conduct monitoring, assessment and control of water conveyance networks, including separate and combined wastewater collection systems, and stormwater drainage systems. The core of the altaStation is the always attentive, custom designed, acoustic pickup (Figure 2). The acoustic pickup continuously 'listens' to the voice of the flowing water. Sound patterns captured by the acoustic pickup can tell a story about what is going on with the water flow in a conveyance system. The acoustic pickup is trained to use the site-specific measured sound pressure (hPa) and concurrent water flow depth (mm) to determine its proportional sensitivity expressed in mm/hPa. Once deployed, the altaStation continuously collects sound pressure measurements which can be translated into simultaneous flow depths. Under normal or expected flow conditions, altaStation is tuned into the sound of the water flow, waiting for a disruption of the white noise characteristic of normal flow depth patterns in the conveyance system and its inherent cautionary message about improper drainage. Upon receiving a sound-based warning from the altaStation acoustic pickup, digital images of the flow conditions can be obtained to provide 'eyewitness' evidence. The altaStation 'Urbanite' camera is an option that cross checks sound-based flow conditions and can assist in the acquisition of additional flow parameters. The installation and deployment of strategically located altaStation units is a time efficient and safe process. At each location in a wastewater or stormwater conveyance system, an altaStation unit is installed under the cover of a standard manhole (eccentric or concentric) without confined space entry. Once the altaStation unit is deployed, system monitoring, data acquisition and operational oversight are conducted without removing the manhole cover. A schematic (Figure 3) illustrates the position of the altaStation components in a sewer manhole. altaStation Deployment An altaStation unit was deployed into a separate sanitary sewer manhole (Sanitary Manhole MH-1) in a medium-sized city in southwest Ohio (Figure 4A). Historically, this site has experienced high, rainfall induced flows that often resulted in sanitary sewer overflows (SSO) at a downstream manhole. As a mitigation measure, this site was redesigned and rehabilitated to provide an 8-inch, flow relief connection sewer to divert flow to a less vulnerable sub-sewershed during normal, dry weather flow conditions. During significant rainfall events, flows with depths that exceed the level of the relief connection sewer channel at an elevation of 814.27 feet, are redirected into the original 8-inch sewer (Figure 4B). The selection of this site was intended to characterize the flow conditions in this manhole and the frequency of these rainfall induced flow diversions. The altaStation acoustic pickup continuously measured and stored infrasonic sound data to listen to and characterize the flow conditions in MH-1. Consecutive, ten-day 'sound clips' were collected from the site. A 3-day sound clip from September 4-6, 2022, was assessed to evaluate the pronounced rise in sound pressure measurements during a significant rainfall event. The rainfall induced infiltration and inflow (RDII) that entered the sub-sewershed upstream of the site was clearly responsible for this measured sound response. The proportional sensitivity of the acoustic pickup at this site was known to be 12 mm/hPa. The sound pressure (hPa) and corresponding flow depth (mm) leading up to and beyond the rainfall event on September 5th, reveals a steep increase in sound/flow depth in response to the RDII initiated by the rainfall (Figure 5 and Table 1). The abrupt increase in flow depth as indicated by the sound pressure measurements caused a rainfall induced flow diversion, as designed. This flow diversion was independently confirmed by the altaStation's Urbanite camera (Figure 6A). Interestingly, at another time during the deployment for this altaStation at MH-1, the Urbanite camera documented an abnormal water quality event that likely warranted an investigation to identify this potentially harmful discharge to the sewer. References U.S. Environmental Protection Agency; Blueprint for Integrating Technology Innovation into the National Water Program; Office of Water, Office of Science and Technology; 1200 Pennsylvania Avenue, Washington, DC, 20460; March 27, 2013.