For several months the County Council has been grappling with a Limited Master Plan Amendment for Ten Mile Creek. The Clarksburg Master Plan, adopted in 1994, staged development in Clarksburg so when triggers were met on stages I - III, the last stage could not go forward without assessing impacts of the first three stages on Ten Mile Creek. Even 20 years ago, planners realized the high water quality of this stream; one of three that empty into the Little Seneca Reservoir which was built in the 1980s to act as an emergency water supply in times of drought should the Potomac River flow drop too low to withdraw the massive quantities needed to supply our regional drinking water.

What does this have to do with our community? A lot. In the 20 intervening years, several scientific and technological advances have taken place that allow the county to look closely at natural resources, their interrelationship with one another and how these can inform responses to development trends. Under the Federal Clean Water Act, Montgomery County was compelled to develop a stream monitoring program in 1994. Until then, the county had not even put a thermometer in a stream to look at temperature changes caused by heavy rainstorms since the 1970s. It takes time to gather and analyze scientific data from monitoring and see the trends. In the late 1990s, GIS data also became available which allowed resources like forest cover, wetlands, biodiversity areas, and steep slopes to be mapped. With this tool, overlays were made to find sensitive areas containing one or more significant environmental features. The Potomac Subregion Master Plan Revision was the first plan review to make use of the new mapping and initial monitoring data. The environmental assessment of Potomac's innumerable resources created the underpinnings for the final Plan, adopted in 2002. Subsequent water monitoring data shows that water quality in streams, starting in jurisdictions like Rockville and Gaithersburg and passing through our subregion on their way to the Potomac River, are improved by our low density zoning, considerable forest cover, and even by the way roads are constructed. Many have grass swales to capture and infiltrate runoff instead of sidewalks and storm drains to direct it. Our Master Plan provides a precedent for making decisions based on protecting water resources.

Ten Mile Creek is benefiting from our experience and from a full 20 years of monitoring data collected through the Countywide Stream Protection Strategy run by the Department of Environmental Protection (DEP). Since the County Council work sessions on Ten Mile Creek began early in the new year, DEP aquatic biologists and regional water quality experts have provided councilmembers with scientific data that shows conclusively how levels of imperviousness from roads, rooftops, parking lots, etc. degrade streams with sediment and chemicals from runoff. Engineered stormwater techniques and facilities are not enough to protect highly sensitive streams. Since the DEP began evaluating the health of streams, biologists have mostly monitored ongoing degradation in streams throughout the county. They have learned the hard way that once a stream declines, it is unlikely to be brought back to health and attempts at restoration are far more costly than preserving our waters through sound land use and adequate forest buffers.

Ten Mile Creek is the highest quality stream we have left, a regional reference stream which scientists speaking to the County Council called "a jewel in the crown" of Montgomery County. It has become a rallying cry for clean drinking water and the Save Ten Mile Creek Coalition, begun in the Spring of 2013, has grown to 30 organizations — all urging the County Council to protect our "last best stream" and place a higher value on water quality than it ever has before by lowering density on development sites while also implementing additional criteria like extended forest and wetland buffers. Save Ten Mile Creek Coalition proposed a more far-reaching full protection plan, which the Council did not discuss. But they have been moved by public concern and a joint committee is recommending a compromise plan that will allow development within the confines of much reduced impervious levels on three separate properties. In the coming weeks they will take a final vote and determine the future of the Ten Mile Creek watershed, Little Seneca Reservoir, and the sole source aquifer on which many upcounty residents depend. The question is: will it be enough, how will we know, and is such a compromise worth the risk?