Federal and State Mandates
As part of its operating permit, the Point Loma Wastewater Treatment Plant is required by the state Regional Water Quality Control Board and the Environmental Protection Agency (EPA) to monitor offshore waters year-round to assure compliance with the federal and state water plans, and to determine the effects of the outfall on the ocean environment. The studies are conducted under the wastewater department's Ocean Monitoring Program by chemists, toxicologists, marine biologists, and microbiologists. Two vessels provide platforms for studying water quality, sediment, fish and organisms living on the ocean floor. The activities are carried out at designated stations around the outfall and throughout the department's 85-square-mile study area.
Since 1996, GIS has become an important tool for organizing, analyzing and translating immense amounts of data generated by these studies into understandable displays and presentations, benefiting scientists and regulators alike. How the GIS technology is being used, however, is better understood from an overview of the Ocean Monitoring Program.
Regulatory agencies normally require incoming wastewater to go through both primary and secondary treatment before it is discharged into the ocean. Lori Vereker, the program's marine biologist and data systems manager, said Point Loma operates under a waiver from full secondary treatment requirements. This allows the plant to discharge effluent after "advanced primary" treatment. According to Vereker, the process removes 85 percent of all solids.
"It's not quite a full secondary treatment, but it is within a few percentage points of complete solids removable, which is our primary concern," she said. "When we went through a legal battle with EPA over this several years ago, the court decided in the city's favor, because going to secondary treatment would have cost $4.2 billion. There was no scientific evidence to support doing that."
GIS Applications
Operation under the waiver, however, imposes strict guidelines on reporting; regulatory agencies require the massive amounts of data generated by the monitoring program to be reported on a regular basis. In addition, the program provides information to numerous other agencies and public officials.
"At various times, different organizations ask us for data interpretation and analysis," Vereker said. "Maybe our management is going to present the data to Mexico, or to someone in Congress, in relation to legislation. It is widely used to help the decision-making process."
Prior to 1996, such reports were mostly in tabular form, line plots and 2-D contour graphics. Vereker said that, although helpful to a trained eye, data in these forms made it difficult for managers and decision-makers who were not marine scientists to see trends suggestive of long-term changes.
Acquisition of Intergraph's MGE (Modular GIS Environment) and related software in 1996 provided tools that enabled both scientists and regulators to more clearly see effects, relationships, and long-term trends in the ocean environment, particularly through 2-D and 3-D analysis and modeling. Two types of data collection and processing illustrate the applications.
Water quality parameters at a particular station are captured by an instrument that records temperature, dissolved oxygen, salinity, clarity, transmissivity, pH and barometry, etc., from surface to sea floor. The instrument makes 24 scans per second and internally averages them to one reading per meter of depth, profiling an entire column of water. Collected data is transferred to disk at the monitoring
Courtesy of San Diego Metropolitan Wastewater Dept.2-D and 3-D renderings were made using Intergraph's Environmental Resource Management Application Data Manager, MGE Terrain
Analyst and Voxel Analyst.
program lab and loaded into an Oracle database management system, along with bathymetry data purchased from the National Oceanographic and Atmospheric Administration. Bathymetry indicates depths of the ocean and related factors at the stations under study. After tables are created in Oracle,monitor-program systems analyst Bin-Bin Shang uses the Environmental Resource Management Application Data Manager,MGE TerrainAnalyst and Voxel Analyst, respectively, to generate 2-D and 3-D presentations of the data.
The database in Oracle is accessed via RIS (Relational Interface System),an interface software that makes a remote or network database availableasa local database. Shang then use the data manager to produce 2-Danalysis and graphics, or to create ASCII files to be used in Voxel Analyst.
The options for presenting 2-D sample data include pie charts to represent the size of different fish communities, bubble charts to show different ranges of coliform bacteria and their locations, bar charts to indicate concentrations of pathogens in fish liver tissue at different locations within a grid, and maps to identify levels and locations of bacterial concentrations along the shoreline.
Shang uses MGE Terrain Analyst to translate latitude, longitude and depth from each sampling station into a 3-D grid map of the ocean floor. Starting with the grid map as a base structure, she uses Voxel Analyst, Intergraph's 3-D analysis and visualization software, to generate 3-D water-quality data columns at 30-40 stations around the outfall, or throughout the entire grid. Queries and analysis are then used to present the data in the most understandable displays.
Vereker said the range of displays for data interpretation are extensive. "We can get a volumetric model of what the water column looks like out there and see cross sections," she said. "We can look at all of the stations at the same time and make a picture of all the data, rather than just data at one point at a time. We can analyze the volume of the entire area."
All those graphs and models help turn data into information that is incorporated into the program's analysis, reports and presentations, she said.
"The GIS system that we adopted is a big leap from the tables of the past," Vereker said. "Before GIS, we had a clear understanding of our data. GIS confirms that our understanding and interpretation of data are correct."
EPA Review
At the end of each five-year period, when the waiver permit for the municipal wastewater department comes up for renewal, all the data collected during that period goes into a report to EPA environmental scientist Terry Fleming, whose job is to review and interpret the immense amount of data.
"With the GIS, it is much easier to look at a picture and immediately see a pattern than it is to look at tables and see a pattern," he said. "I can go to our managers and say, 'Here's a bunch of tables that indicate the plume tends to be offshore.' Or I can show them a map for each month of the last year, and they can see that the red thing is the plume, and say, 'OK, I understand; it's always offshore.'"
A Sharper Image
"GIS gives us a way of looking at patterns to see if there are potential problems. But my analysis goes beyond just looking at the pictures; I have to look at the data itself," Fleming said. "We can't really use a display to say there is something definitely wrong here, but it does allow us to take the next step and say, 'There might be a problem, let's look a little more at the detail here.'"
Vereker agrees. "If nothing else, the GIS makes a much clearer picture, especially for non-scientists, managers, regulators; people who are not necessarily up on all the current scientific thought they need to understand what you are trying to show them."
GLOSSARY
Bathymetry -- measurement of depth at a specific location.
Grid -- a geographically defined area within the Ocean Monitoring Program's study area.
Plume -- space in air, water of soil containing pollutants released from a point source.
Primary treatment -- wastewater treatment designed to remove 50 percent to 70 percent of suspended solids; 25 percent to 40 percent of biological oxygen demand (BOD), and 50 percent of pathogens.
Secondary treatment -- wastewater treatment designed to remove approximately 90 percent of suspended solids and 80 percent to 90 percent of BOD.
Stations -- geographic points within a grid, each identified by latitude, longitude and depth.
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