There are more technical explanations, but in simple terms, the federal agreement means that when your local sewer plant is at capacity, you can't expand it.
That's because there is a limit on how many "nutrients" you can discharge into the streams and rivers that lead to the bay. Officials say plants are so efficient now that until there is a technological breakthrough, not much can be done.
But, as I noted in April, "the development of new technology accelerates when there's money to be made. And in this case, the inventor who finds a way to take more nutrients out of wastewater will reap a harvest of cash."
Marshall read that column and after a bit of phone tag, we talked about the new technology he has come across that he feels might help Washington County.
It's called the Groundwater Replenishment System, which Marshall would like to see used in Wayne County, where a 1992 report from the Ohio State University Extension Service said that 98 percent of all households use groundwater.
That includes public water systems, most of which use deep wells. That same extension service report says that Wayne County averages only 38 inches of rain fall each year and that only six inches of that goes to recharge the aquifer - the place below ground where water is naturally filtered and collected.
If I understand Marshall's concern correctly, it is that he fears the aquifer will be pumped dry and will then take many years to recharge on its own.
Enter the Groundwater Replenishment System (GWR), which takes sewage at the end of conventional treatment and distills it into drinkable water.
GWR officials didn't get back to me in time for this column, but in September of 2004, National Public Radio did a piece just after the company broke ground for a large plant in Orange County, on California's Pacific Coast.
According to NPR, the treated wastewater, or effluent, is drawn through filters that are "300 times smaller than the width of a human hair."
The it goes through a process called reverse osmosis, which Srivaji Deshmukh of the Orange County Water District said can filter on the molecular level.
Finally, the effluent is passed through an ultraviolet light, in case something harmful has escaped the first two stages of the process. The story claimed that, at that point, the water is "four times as pure as a mountain stream."
What Orange County does then is to inject much of it into the ground, where it is further filtered and eventually pumped back up for use as drinking water.
Orange County also does this in part, according to GWR's Web site at www.gwrsystem.com, because it needs to create an underground barrier of fresh water to keep seawater from seeping into the area's water supply.
So at this point, you might say: Who cares about Orange County?
Consider this: If that county has installed a process so good that it will allow the final product to be pumped back into the ground, what might the same process do for our local problems with nutrient removal?
The Oran ge County system still needs final approval from state environmental officials, but has already been given grant money by the U.S. Environmental Protection Agency.
It needs it. The project's estimated cost is almost $500 million, to turn effluent into enough water to meet the needs of 144,000 families.
But this is a massive project that includes a 13-mile pipeline to send treated effluent back to recharge lakes in Anaheim. Local installation of a GWR system to serve only Washington County might not be nearly as costly.
It also seems possible that several counties along the Potomac might be able to share the costs and benefits of a system, although the engineering involved in a pipeline to carry effluent from one plant to another might argue instead for several smaller plants.
Perhaps formation of a regional authority might help counties negotiate for a bulk price, so to speak, on several plants.
If all this sounds too much like science fiction without the alien monsters, I wish it were. But federal officials are now telling local governments that if they want to expand, conventional treatment isn't enough.
As long as we don't adopt Orange County's first slogan - "Toilet to Tap" - it seems only prudent to give the GWR system a look.
Bob Maginnis is editorial page editor of The Herald-Mail newspapers