Curbing Water Pollution with Mobile GIS

April 1, 2006 By: Kevin P. Corbley, Randy Stauffer

Mobile data collection with handheld GPS units facilitates a San Francisco utility's quest for cleaner water, enabling a two-pronged effort to build a storm drain GIS layer and educate citizens about pollution.

In 1972, the United States declared war on water pollution with the passage of the Clean Water Act. As the primary water/wastewater utility for a city flanked by water on three sides, the San Francisco Public Utilities Commission (SFPUC) played an aggressive role in the battle to eradicate industrial contaminants that were fouling both San Francisco Bay and the Pacific Ocean. And in 2005, SFPUC deployed mobile GIS to take the water pollution fight directly to the public.

Today, SFPUC wastewater control inspectors map the city's storm drains with handheld, GPS-based data collection devices that capture the drains' precise locations and record digital notes on their condition (see Figure 1). Although this information is helping to build a key layer in the utility's new enterprise GIS, the data collection program is also the critical first step in a massive public education initiative titled "Only Rain Down the Drain."

Figure 1. Handheld data collection units capture the precise locations of storm drains and allow technicians in the field to record notes on their state of repair. Here, the navigational toolbar is displayed above a street map.

Cleaning Up Industrial Effluent

Implementation of the Clean Water Act in the 1970s and 1980s focused on eliminating "point-source" pollution, which is related to the industrial discharge of chemicals, debris, and toxins into the wastewater system. These contaminants can flow directly into local bodies of water — with disastrous ecological results — or into wastewater treatment plants not designed to handle toxic pollutants.

Under the 1972 law, this type of pollution was dealt with at its source. Regulations required businesses to eliminate harmful sewage (or at least reduce it to acceptable levels) by pretreating the discharge stream before it flowed from their premises. Officials usually tailored pretreatment programs so that the pollutant concentrations permitted in the discharge were dictated by the capabilities of the downstream wastewater treatment plants that would receive the flow.

By the late 1980s, better-controlled point-source pollution posed a smaller threat to public waters, and the water pollution battle shifted to a new front. Studies conducted at the time showed that storm-water (the runoff that occurs after rain or snow) had emerged as the new primary source of water pollution. In many ways, stormwater presents an even greater challenge because it flows from innumerable sources and carries a broad range of contaminants.

"Rainwater washes the streets and picks up all of the droplets of oil, gasoline, and other wear debris related to vehicle operations and channels them into the stormwater system," said Lewis Harrison, Water Pollution Prevention Program manager in the SFPUC Wastewater Enterprise. "Left unchecked, these contaminants end up in our treatment plants."

Among the worst sources of runoff pollution are construction sites where exposed soil is eroded by rainwater, Harrison explained. Sediment buildup from such sites reduces the hydraulic capacity of the sewer system, and sediment-laden runoff picks up contaminants on its way to the sewer. If erosion can be controlled, these pollutants can also be kept out of the sewer system.

Adding to the problem are citizens who use storm drains and catch basins to dispose of pet waste, household chemicals, grass, leaves, and trash. When dumped down the sewer, these pollutants place additional stress on the treatment system because they must be removed or remediated, increasing the operating expense of the utility.

Many utilities have found that the most cost-effective approach is to prevent contaminants and debris from ever reaching the treatment plants. SFPUC believes its mobile GIS and public education programs are helping to achieve this goal.