POWAY -- Flood control basins built early in the South Poway Business Park's life are proving to be an unexpected asset in the city's effort to clean up the water that flows into storm drains.

The California Regional Water Quality Control Board recently approved a plan that will see five of the basins modified to double as collection sites for storm water at the business park. Announced this week by city officials, the move means Poway is the first government entity in the county to get the go-ahead to collect and treat the water, also known as urban runoff, on a mass scale.

The distinction will have multiple benefits for the city, new companies looking to build in the business park and the overall stormwater cleanup effort, city officials said.

The benefits include lower development costs for new projects -- an edge when it comes to enticing companies to Poway; increased property tax revenue; and cleaning up storm water that would otherwise go untreated as it washed into storm drains and eventually into creeks and other waterways that lead to the ocean.

"As we talk to developers and the business people, we'll make this known," said Poway economic development manager Ingrid Alverde. "It's truly a win-win situation."

Urban runoff is water from rain, irrigation systems and other sources that runs along the ground and into storm drains. The water picks up silt, automobile oil, pesticides, soap and other contaminants along the way.

By the time the polluted runoff reaches the ocean, it is full of bacteria. The problem has resulted in numerous local beach closures in recent years.

A new, statewide stormwater program that went into effect in 2001 aims to change that. One of its requirements is that all new commercial developments include on-site stormwater treatment facilities.

The requirement can be met by the construction of a large basin or hole that can hold runoff for 72 hours, deemed long enough for pollutants to settle to the bottom. The water on top is then released.

The requirement adds to the cost of construction projects and forces developers to set aside part of their properties for the basins.

The Poway proposal allows new companies in the business park to use the existing basins, rather than spending the money to install individual storm water runoff control systems.

The builders of new projects in the South Poway Business Park will only pay to have perforated discharge pipes in the flood control basins replaced with pipes that will not allow the water to filter out until the holding time is up.

The cost of doing so is a fraction of what it would take to build a new basin, said Poway development services Director Niall Fritz. He cited a new Kohl's department store to be built on Scripps Poway Parkway as an example.

"Kohl's is going to have to spend maybe $15,000 or $20,000 (on modifications) instead of $300,000," Fritz said. "There's an improvement cost that you don't have that you'd have elsewhere.

That in turn will make property values in the park go up, he and Alverde said. For Poway, that means more revenue from property taxes, which are based on property values, they added.

Runoff from existing businesses in the park -- which are not obligated to meet the storm water regulations -- will also be collected and treated in the modified basins, thereby helping the environment and boosting Poway's overall storm water cleanup performance, they said.

Developer Larry Langohr, whose Wisconsin-based firm is preparing to build the Kohl's store, said he welcomed the cost savings he will see as a result of the new option.

"And it is something that ends up making some sense because there would have been a duplication of (collection) efforts," he said.

While there may be other cities that have flood control basins that could be modified to accommodate stormwater, Poway was the first to propose the idea, said Phil Hammer, a Regional Water Quality Control Board environmental scientist who reviewed the plan.

The agency will review the results of water quality tests to ensure the goal of reducing the amount of pollutants reaching natural waterways is met, he said.

Contact staff writer Andrea Moss at (760) 739-6654 or amoss@nctimes.com.