The Pinecliff Park Stream Restoration Phase II design project is located along Plankstone Creek in Frederick County, Maryland within County owned Pinecliff Park. In order to meet National Pollutant Discharge Elimination System (NPDES) requirements, Frederick County selected Plankstone Creek as a stream restoration opportunity. Phase I of the restoration was completed in 2011, and this design will complete Phase II. Phase II will include reaches upstream and downstream of the Phase I restoration, as well as spot repairs to the Phase I restoration. To assist in the assessment of erosion causes and potential restoration strategies, background information was collected on land use, geology, soils, and future development in the contributing watershed. The Pinecliff Park Stream Restoration Phase II design project is located along Plankstone Creek in Frederick County, Maryland within County owned Pinecliff Park. Plankstone Creek is classified as use I-P (Water Contact Recreation, Protection of Aquatic Life, and Public Water Supply). Plankstone Creek is located in the Lower Monocacy River Maryland 8-digit watershed (02140302). Plankstone Creek is also identified as a tributary of The Upper Potomac River. CRI performed a detailed stream geomorphic assessment, a geologic and historic data collection, hydrologic and hydraulic analysis, visual site investigations, and a stream bank stability assessment. These efforts were performed to develop an understanding of the existing impacts within the stream corridor, current geomorphic processes, and causes of instability in order to develop potential restoration recommendations. The stream restoration design utilizes a natural channel design approach. In-stream log and rock structures are proposed to stabilize the impaired channel. Bank grading is proposed to stabilize eroding banks in the Phase I and Phase II project locations. The design is anticipated to remove 171 lb/yr of nitrogen, 67 lb/yr of phosphorous, and 126,499 lb/yr of total suspended sediment. The stream restoration sediment reduction values are based on the standard bulk density and nutrient loading rates. Soil samples were taken onsite, and the nutrient reduction calculations will be updated accordingly at the next milestone. Location: Frederick County, MD Client: Frederick County Department of Public Works Key Services: Delineations Geomorphic Assessment Biological Assessments Tracer Study Hydrology and Hydraulics Mitigation Planning & Design Agency Coordination Permitting The restoration of the main channel of the Plankstone Creek begins at a stable riffle, approximately 115 LF upstream of the exiting concrete weir. The upstream limit was chosen to reduce impacts to the well-developed floodplain wetland and mature forest upstream of the site. The upstream reach of the Phase II restoration extends approximately 500 LF down to the rock cross-vane at the upstream end of the Phase II restoration site. The proposed channel design is based on a Rosgen type Bc channel with the design to include stable dimension, pattern, and profile in order to tie-in to existing stable channel bed features at the upstream end and the Phase I restoration reach on the downstream end. The intent of the design is to reduce shear stresses within the channel and across the limited floodplain surface during high flow events to below the critical shear stress threshold of the substrate. The overall size of the floodplain will be limited to avoid major earthwork and minimize impacts to existing natural resources. Proposed channel bed features such as riffle, run, pool and glide will provide stable epifaunal substrate and create diverse in-stream habitat. The riffle and run features will be stabilized using rock and log structures. Energy dissipation will be achieved mainly through drops and hardened structures within the channel due to the confined floodplain. From analysis of the existing conditions, sediment loading from the upstream reach does not appear to be a major concern mainly due to the expansive floodplain wetlands adjacent to the channel upstream of the restoration site. Based on the exiting profile data, streambed degradation downstream of the failing weir has reduced existing floodplain access. The design will use a constant slope from the existing bed elevation at the weir, down towards the bed elevation of the cross-vane at the upstream end of the Phase I restoration. This approach will require the bed immediately downstream of the weir to be raised, while the downstream end will meet the existing elevations. A simple approach was chosen for stabilizing the reach downstream of the Pinecliff Park crossing. The plunge pool downstream of the culvert, under Pinecliff Park Road, will be stabilized with additional Riprap. A rock cascade is proposed downstream of the scour pool. The top sill of the rock cascade is set to less than 0.2’ below the culvert invert. The cascade will tie into the existing gabion basket structure on the right bank which will remain in-place. The existing riffle material in the channel bottom will be adjusted to meet the proposed dimensions and profile. Smaller material will be used to choke the existing riffle material to ensure surface flow over the structure to reduce the risk of flow piping and provide increased fish passage through the structure. A series of rock weirs will be used downstream of the existing riffle material to safely convey flows down the relatively steep gradient over controlled elevation drops and into the Lower Monocacy.