Walking along Gwynns Falls Trail with Baltimore Harbor Waterkeeper Tina Meyers, it's ironic that we pass a beige, beat-up, overturned residential trash can lying by the tree line. We're on our way to survey the Gwynns Falls stream where it meets the Middle Branch of the Baltimore Harbor. Soaking rain falls steadily — it's the kind of day that carries trash down storm drains and into creeks.

In the distance, Interstate 95 spans the gray skyline as we stop midway on an iron-and-wood footbridge. Below, dark waters dotted with Styrofoam cups and plates, take-out containers, potato chip bags and plastic bottles flow toward the Middle Harbor. The shorelines on either side of Gwynns Falls are strewn with muddied, multicolored litter.

Such a sight is disheartening, Meyers said, especially when the first rain after a volunteer cleanup event brings tons of new trash into the water. "It's becoming more and more clear that the solution is addressing the problem at its source," she said.

Trash and trashy waters are an all-too-familiar sight for most Baltimoreans. The city has long wrestled with how to stop the never-ending flow of trash. Baltimore's fleet of trash skimmer boats work seven days a week to clear around 200 tons of debris from the harbor each year. In addition, inceptors filter trash at storm drains and long booms collect floating trash. In 2011, a giant waterwheel trash inceptor broke because of the overload of trash. And every time it rains, the outpouring continues.

To try to break the water-bound trash cycle, the Maryland Department of the Environment is reviewing a plan that would treat trash like other pollutants — such as nitrogen, phosphorus and sediment — and help the state meet an EPA mandate to limit trash in the harbor waters.

In 2008, the EPA approved the listing of Baltimore Harbor's Middle Branch and Northwest Harbor as impaired by trash, debris and floatables under the federal Clean Water Act. That listing put Maryland on the hook to create the TMDL, formally called a Total Daily Maximum Load, a maximum load limit for trash that can be in the water. Maryland, California and the District of Columbia are the only jurisdictions that have developed a trash TMDL.

A TMDL is like a pollution diet, explained Lee Currey, of MDE's TMDL Technical Development Program. On this portion-controlled diet, a waterbody can only receive a certain amount of a pollutant — such as a nutrient, a toxin like PCB, or a bacterium. That amount is set low enough so that water quality standards will support living resources, maintain public health and reach other goals.

"Trash is an unconventional pollutant," Currey said. "It was determined in the Anacostia River TMDL — both Maryland and DC agreed — that interpretation of that water quality standard is 100 percent removal of the trash, and we applied that same process to Baltimore Harbor."

As with the Anacostia's TMDL, MDE wrote load requirements for the Baltimore Harbor TMDL using a "load removal" measurement system — how many pounds of litter should be removed from the watershed — to reach their goal of removing 100 percent of the trash by 2030. In its current draft, Baltimore's TMDL requires more than 410,000 pounds of litter per year to be removed from the watershed. That 100 percent is based on a baseline figure that MDE determined is the average full load of trash.

Removing 100 percent of the trash doesn't mean that on any given day there will be zero trash in the system, Currey explained, because it's not realistic to remove every single piece of trash. Even toxic substances don't have a TMDL of zero, he said.

Baltimore's trash TMDL comes on the heels of Anacostia's TMDL, approved in 2010, which is also measured by pounds of trash recovered by traps, volunteers or the city-run trash skimmer boats. Anacostia Riverkeeper Mike Bolinder said it's a move in the right direction, but it hasn't addressed the root of the problem.

"It's kind of a creative way to cram a nontraditional pollutant (square peg) into a TMDL structure (round hole), but it has two obvious flaws," Bolinder said. "One, it assumes the baseline to be analogous to the 'ambient load' of trash — as if somehow Styrofoam cups and single-use bottles are naturally occurring in the earth. Two, it only captures trash at the bottom end of the pipeline, and really only succeeds at creating a 'maid service' for the watershed's floating litter."

Baltimore Harbor Waterkeeper and other environmental groups believe that Baltimore's current TMDL version focuses too heavily on scooping trash from the water instead of preventing trash from entering the water in the first place.

"It needs to be focused on the upstream sources, not on removing it from the water," Meyers said.

Finally, Baltimore watershed groups say that the TMDL allocations must be set at zero (with a reasonable margin of error for some rogue trash items) for the new limits to work.

Currey of MDE maintained, though, that whether the TMDL is measured in terms of trash removed from the watershed or measured as an amount discharged into the waterbody, the results will be the same: lowering trash levels in the harbor. For the trash TMDL, the agency proposes a suite of solutions to meet the load requirement, including source-based solutions (such as education, outreach and trash removal from land) as well as skimmer boats and trash nets, said Jay Apperson of MDE.

The agency is refining the draft TMDL that was published in September 2012. After an autumn public comment and response period, the agency recently decided to delay the finalization of the TMDL to re-evaluate and ensure that the final document accounts for current science and policy.

Once a trash TMDL is finalized, Baltimore and Maryland will need to get creative. Solutions to curb the trash flow may include more trash nets; stricter and better enforced illegal dumping and littering ordinances; increased street sweeping; creating a return deposit fee for glass and plastic containers; increased frequency of trash collection; and more.

Meyers said that solutions should span charging fees for plastic bags, banning foamed polystyrene, getting young people involved in cleanups and stenciling storm drains and making sure every resident has a trash can with a lid.

Back at the Gwynns Falls, the rain hasn't let up. Nor has the flow of plastic bottles and Styrofoam plates that float past. It's clear that the Harbor needs to start its trash diet soon — and that Baltimore residents have a monumental challenge ahead of them as they figure out how to stop the steady stream of litter.

Harris Creek suggestions include lids, landkeeper

Watershed groups continue to push for a focus on upland sources as the best way to reduce trash in the harbor's waters because the cycle starts in the neighborhoods, explained Ray Bahr, a retired cardiologist.

Bahr joined up with the Baltimore Harbor Watershed Association's project to investigate trash pollution in the Harris Creek watershed. There, he learned firsthand that local residents were seeing volumes of trash like never before. While making rounds with the neighborhood association president, Bahr identified 100 or more "mini-landfills" behind vacant houses, where trash would accumulate, often attracting pests and spilling out into alleys.

Three years ago, the committee launched a 10-week project that focused on 4,000 homes in the middle of the watershed, many of them in neighborhoods beset by poverty, vacant lots and empty houses — prime targets for trash dumping by outsiders. City workers, Bahr said, would sometimes ignore the dumping and allow trash to accumulate.

Bahr's group placed an interceptor in Canton to measure the amount of Harbor-bound trash coming from 17 neighborhoods, and found three to five tons of trash washing through in a month. After a cleanup project for half of the watershed, they found they'd reduced the amount to half a ton.

This was just one watershed, Bahr explained, and there are many watersheds around the Inner Harbor.

He and his committee made recommendations to distribute trash cans with lids to residents and to appoint an independent "landkeeper" who could spot and report trash accumulations. "As long as we allow this practice to continue [land trash flowing into the harbor], we're not going to make it swimmable or fishable in the near future," Bahr said.