Almost every time the City of Los Angeles solves one challenge, it seems to unlock Pandora’s box. For example, converting more than 1,200 miles of streams and rivers into concrete channels years ago to help control floods escalated every form of pollution.

 

Today, this city of four million has more than 60 total maximum daily loads (TMDL) requirements covering the Santa Monica Bay, Los Angeles River, Dominguez Channel and Ballona Creek watersheds. About 100 million gallons of water flow through the storm drains on an average dry day. When it rains, flows can increase to 10 billion gallons, reaching speeds of 35 mph and depths of 25 feet.

The Watershed Protection Divi-sion, under the Bureau of Sanitation, manages the stormwater program. It deals with a population that changes by 50 percent every 10 years, the logistics of managing projects spread over 465 square miles, and the need to establish protocol for every procedure.

 

Nevertheless, the division, founded in 1990, has enjoyed some impressive wins. After introducing low-flow diversion facilities to intercept dry-weather runoff at the largest beach outfalls and sending it to wastewater treatment plants, the grade for the beaches in summer rose from an F to an A. The volume of trash on Long Beach alone dropped from 9,000 to 3,000 tons during years with more than 14.5 inches of rain. Overall, the city’s water quality is improving.

 

Under the leadership of storm-water program manager Shahram Kharaghani, Ph.D., P.E., BCEE, the team’s first line of attack was controlling trash — sediment, debris, vegetation and litter.

“It’s a technology-based operation,” he says. “We figured that some bacteria, metals, and other components attached to the trash would be removed with it.” What the team did not count on was having to reinvent the wheel against the ticking time clock of the U.S. EPA.

 

100 percent in 10 years

The city’s trash TMDL requires a 10 percent reduction per year for 10 years ending in September 2015. To identify the geospatial distribution of trash and establish an accurate sample size, Kharaghani’s staff conducted a survey from 1999 through 2003.

 

“Within a city this large, we always rely on other divisions,” he says. “In this case, Operations and Maintenance supplied data each time they cleaned one of our 54,000 catch basins.”

Analysis of the data revealed high-, medium-, and low-trash-generating areas. The high area was concentrated in the civic center of Los Angeles and radiated out for about two miles. The analysis showed that land use was not a pivotal factor in trash volume.

 

Simultaneously, the city had to develop a plan to reduce the trash entering the storm drain system through catch basin openings. Kharaghani’s team studied trash control devices, but all were too new to have track records. “The number of challenges we faced continues to this day, and the technology continues to evolve,” he says. “We test and usually redesign all the devices.”

 

The city’s first generation of screens clogged with trash during winter wet weather. Bureau of Sanitation crews removed them to reduce the potential of flooding.

 

Watershed Protection engineers partnered with engineers from a local company to design the second generation of screens. Two magnetic anchors at each end kept them closed. When runoff reached 60 percent of the curb height, hydrostatic pressure sprung the anchors, and the covers swung inward and upward. Once the runoff subsided, the covers closed.

 

This time, the team installed 1,000 screens and observed their performance. “The screens snared plastic bottles and other large material as they closed,” says Kharaghani. “Without sufficient hydrostatic pressure, the anchors wouldn’t release, and that caused some street ponding. Also, the large wheel lug nuts on buses and heavy-duty trucks damaged the screens.”

 

Flow-activated third-generation screens open when flows disengage the locking mechanism at the back and swing inward with hydrostatic pressure. The locking mechanism cycles repeatedly during storms, returning to the closed position once the flow subsides. Catch basins in trash-generating areas will have screens wherever feasible by September 2015.

 

Growing pains

Catch basins in high trash areas also received inserts in the form of wall-to-wall containers with 5-mm mesh openings. The first-generation insert clogged with minimal debris and decreased volume in shallow basins. The bottom screens needed cross-bracing or they sheared at the anchoring points. They also had no access to the outlet pipe. The engineering teams went to work again.

 

The redesigned inserts are semicircular cylinders of 5-mm stainless steel mesh installed in front of the outlet pipe and extended upward to just below the curb opening’s bottom lip. The Los Angeles Regional Water Quality Control Board recognized all inserts as full-capture devices, meeting the trash TMDL requirements.

 

“Our strategy called for a BMP train of inserts and screens in the high-trash-generation areas to achieve the best performance and maintain current maintenance practices,” says Kharaghani. “Medium- and low-trash-generation areas received only screens, making the best use of limited funds.”

 

During the insert pilot study, operation and maintenance crews collected trash data and measurements for storms occurring 10 or more days apart and accumulating at least 0.25 inches of rain. A report published in 2006 concluded that the inserts retained 100 percent of the trash, while screens deflected 86 percent of the trash that would have entered the catch basin.

 

While the city worked on meeting the trash TMDL, vendors offered various large devices to capture trash downstream from hundreds of catch basins. “Cleaning one inline device is easier than cleaning 1,000 screens, so the concept challenged our minds,” says Kharaghani. Grants enabled the engineers to test netting systems (of which the city now uses 15) and hydrodynamic separation devices (six are in operation).

 

“We established several sub-watersheds within the city for installing separation units,” says Kharaghani. “That way we could control the area like a laboratory, monitoring how much trash each unit collected. All units were installed on smaller lines to help manage headloss.”

 

The systems worked, but it created new challenges. Once installed, the devices acted like barriers, increasing the potential for backups. Maintenance required closing of traffic lanes and using heavy cranes to lift a unit’s concrete lid. Removing the debris took multiple sewer cleaning machines and dump trucks.

 

Human behavior

The other prongs of the department’s trash reduction approach are enforcement and public outreach. Since 2004, teams have developed four outreach programs in multiple languages. A 45-minute assembly program for elementary and junior high school students presents the impact humans can have on stormwater.

 

It culminates with Ocean Day. “Last June, we bussed more than 7,000 kids to Santa Monica Bay to screen and clean up the beach,” says Kharaghani. “Afterward, they lined up to form the outline of a marine animal and the words, ‘Save Our Ocean.’” A photographer in a helicopter photographed the aerial art (www.oceanday.net).

 

Division staff partnered with home improvement and hardware stores, paint stores, and garden centers to place pollution prevention materials on shelves next to paints, pesticides, fertilizers, and other household hazardous wastes. They conducted 11 employee training sessions at stores to familiarize personnel with the materials and with proper disposal methods.

 

Kharaghani’s staff also worked with auto parts stores, laundromats, car clubs, swap meets, and high school auto shops to persuade do-it-yourselfers to dispose of used oil and filters properly. In 2004, the division saw a 42 percent increase in oil collected at more than 300 centers citywide.

 

“Quantifying our outreach efforts is difficult because we implement multiple strategies,” says Kharaghani. “Furthermore, we don’t know what percentage of today’s increase in collected used oil is due to the program, and what percentage is due to the bad economy and more people coping by changing their own oil.” He usually gives the programs 5 to 10 percent credit in reports for reducing specific pollutants.

 

The city has a $1,000 fine for littering but has too few police or authorized inspectors to enforce the law. “We make a lesson out of any person caught red handed, but zero to a handful of tickets are issued per year,” says Kharaghani. “It’s similar to the 1970s ‘crying Indian’ Keep America Beautiful public service announcements. The message was quickly forgotten, and life continued unchanged.”

 

Uncharted waters

To gather data to support re-evaluations of the city’s Bacteria TMDL in April 2011, chemists and biologists in the Pollution Assessment Section (PAS) monitor the Los Angeles River, Dominguez Channel, and Ballona Creek for biological, physical, chemical and habitat factors. They sample numerous areas multiple times during the day and before and after rains to gain an accurate picture.

 

To overcome the logistics of managing a project spread over 465 square miles, Kharaghani’s team involved multiple agencies.“I am blessed to work with good people, and have so many doing a piece of the puzzle,” he says. “I learned that if you have a clear vision and share it with your team, seek their opinions and incorporate them as you implement the program, your chances for success will increase.”

As a result of the team’s efforts, stormwater runoff again recharges the aquifer instead of flooding the streets of Los Angeles.