Rock Creek Assessment

Conclusion
Through the public participation process, we identified a perception of Rock Creek is that of a wounded watershed not worthy of saving. The study was designed to address questions that were a result of the public meetings held at the start of the project:

·      What is the impact of sewage, agriculture and stormwater on Rock Creek?

·      Why is the creek muddy?

·      Does the creek heal itself?



What is the impact of sewage, agriculture and stormwater on the Rock Creek Watershed?
Impacts of stormwater and agriculture on sections of the Rock Creek Watershed are documented on the federal list of impaired waters. Our study supports this to an extent. The data show significant increases in nitrate, orthophosphate and sulfate concentrations from upstream of Steven’s Run to downstream of the borough of Gettysburg. Surprisingly, other urban impacts included a significant increase in nitrates, sulfates and orthophosphates from upstream of Steven’s Run to downstream of the borough of Gettysburg as well. This is most probably due to over-fertilization of lawns, improper disposal of household pet wastes, and potentially illicit and other discharges observed in Steven’s Run. We recommend performing soil tests on a regular basis to determine the proper amount of fertilizer that is needed on a lawn, properly disposing of pet wastes and identifying the sources of discharges that were observed.

Our habitat assessment also indicated stormwater impairments to the stream in the amount of erosion and subsequent sedimentation that was visually observed. Agricultural impacts were observed more through the habitat assessment than through the chemical monitoring. The habitat assessment indicated a lack of stream bank stability, riparian buffer and in-stream sedimentation in agricultural areas.

Our monitoring program has documented the negative impacts of sewage treatment plants as well. The data show significant increases in nitrate, orthophosphate and sulfate concentrations from upstream of the Gettysburg Municipal Authority Sewage Treatment Facilities to sites at and downstream.  Increasing development will only add to the existing nutrient load unless necessary measures are taken. There are 2 proposed sewage treatment plants. We recommend implementing nutrient reduction technologies at proposed and existing sewage treatment facilities to further treat wastewater and prevent additional nutrient loading to the creek.

Why is the creek muddy?
The geology of the Rock Creek Watershed consists mainly of shales and sandstones that erode to clay and other fine materials that tend to stay suspended in the water column. Our study did not support the perception of the Rock Creek as being a “muddy” creek. Our monitoring events were scheduled at the same time each month and may not have captured effects of storm events that would contribute to muddy and turbid streams. A future study focusing on comparing transparency results at high and low flow may be warranted.

Does the Rock Creek heal itself?
Our study shows that without additional impacts, whether from sewage treatment plants or encroaching development, the creek does appear to have the capacity to heal itself, for now.

Each site was evaluated based on the data gathered at that site.  Dissolved oxygen and percent saturation of DO, and macroinvertebrate data are more of and indicator of local water quality than nutrient data.  The rationale is that parameters that support local aquatic life are a better indicator of water quality.  Nutrients, like phosphates and nitrates, were considered less of a concern for local water quality because dissolved oxygen levels and percent saturation were adequate to support aquatic life.  It should be noted that our water quality evaluations are for local conditions.  We recognize that nutrient loading, while not impacting local water conditions, do present a problem for water quality downstream and in the Chesapeake Bay.

Overall, the picture we see is NOT a watershed beyond repair but a watershed on the brink. Increasing developmental pressures push the watershed closer to the edge.  Future health of the watershed depends on the actions that are needed today.