3.3 Thermal Pollution

Another water quality issue facing York Creek is the threat of thermal pollution. The addition of paved, impervious surfaces throughout the watershed is again a concern. Water flowing over these areas picks up heat and, as most of the stormwater is not adequately detained, it delivers the thermal energy, along with other NPS pollutants, to the stream.

Surface runoff and its constituents are not the only temperature related problems in the York Creek Watershed. As the amount of impervious area in the watershed increases, lesser amounts of stormwater can infiltrate the surface to recharge the groundwater system. As inflow of cooled groundwater is an important contributor to York Creek, a decrease in groundwater recharge could result in an increase in stream temperature, further decreasing the survival chances of coldwater fish species.

A detention basin located in the York Creek Estates subdivision has had its outlet plugged in order to create a wet pond. The residents of the neighborhood then use the collected water for lawn irrigation. As a result, the basin is usually near capacity, and therefore the ability to detain additional stormwater is diminished to the point where even small rain events cause discharges over what was once the emergency spillway. Unfortunately these discharges are of warmer surface water rather than the cooler water located deeper in the basin. Situations of this nature further threaten the water quality of York Creek.

Another potential source of thermal pollution is located in the lower reaches of the watershed where the primary land use is industrial. A paving company located on Mill Creek Avenue stockpiles crushed asphalt, sand, and other materials on site. The larger asphalt pile is located less than 100 feet from York Creek, and it is believed that no method exists for treatment of stormwater runoff on the site. One result of this is that during rain events, thermal energy stored within the pile is released as precipitation runs over the pile. Runoff from the site then is directly conveyed to York Creek through the curb drains in Mill Creek Avenue. In addition to thermal contributions, the runoff from the stockpiled asphalt contains elevated levels of petroleum related materials. An oily sheen on the water downstream from the paving company is readily apparent during rain events. Additional study to more precisely determine the impacts of the facility on York Creek is recommended.

Another potential thermal problem associated with the current development trend is the decreasing vegetative canopy over the creek. As streamside trees are cut down and replaced with turf, the stream is exposed to increased amounts of sunlight, which increases stream temperature. The maintenance of a riparian buffer is critical to the return of York Creek to trout quality habitat.