Charles P. Johnson & Associates has been working in the Maryland, Virginia, Washington D.C. metro area since 1971. We have accumulated a diverse portfolio of projects from our four offices that show our array of skills and the breadth of our reach. We have planned, engineered, and surveyed everything from residential and commercial developments to roads, streams, and stormwater management systems. Many of our projects are from repeat clients, which demonstrates our commitment to excellence, and their satisfaction.
College Gardens Park (Award Winning Project)
The City of Rockville contracted CPJ with the task of rejuvenating an aging community park in concert with providing Stormwater Management (flood control and water quality improvement) and Stream Restoration work to protect the 2,100 foot downstream receiving water, known as the College Gardens Tributary to Watts Branch. This heavily impaired stream drains a 158 acre, 42% impervious catchment; a mixture of residential and light commercial use with little SM control.
The four primary goals for rehabilitation work included:
Increased park patronage and aesthetic improvement
Cost efficient renovation of the park to provide SM
Reduction of bank erosion along the Tributary
Protection and enhancement of natural resources
CPJ developed three alternative concepts to determine the most effective balance for SWM control and park amenities, based on input from City staff and the community. CPJ evaluated several alternatives including SR along the entire length, onsite pond creation, and off-site SM. The option chosen involved the construction of an extended detention wetland pond encompassing the area of the existing pond but three times in scale. The design included a sediment forebay, aquatic wetland bench and a direct feed of storm flow via a flow splitter from an adjacent 54” diameter storm sewer. The design provides 50% of the water quality volume and 100% of the channel protection goal at the park per MDE standards.
Specific goals for this project included a 42% percent reduction of sediment being generated by streambank erosion along with an 80% removal of total suspended solids (TSS). The stream work was completed in February, 2009 ahead of the park renovation which was completed in December, 2009; the project is being monitored to determine project success.
CPJ worked closely with Slater and Associates to coordinate the pond design as part of a new park master plan with additional and improved park amenities as well as protection of existing natural resources. The end product is a functional SWM facility that is a centerpiece of the park and jewel of the City’s park system.
Guldesky Stormwater Management Pond
University of Maryland - Shady Grove Campus
CPJ has been contracted by Montgomery County Department of Environmental Protection (DEP) under its Task Order system to provide engineering and survey services for the analysis and retrofit of the Gudelsky Pond dam. The dam, formerly identified by Maryland Department of the Environment’s Dam Safety Division (MDE) as ‘high hazard’, was reclassified as ‘unsafe’ pending the results of a dam breach study. CPJ completed the dam breach study of the dam for existing conditions as well as for four different retrofit concepts.
After consultation with DEP and MDE, a weir wall retrofit design has been selected as the preferred alternative and will reduce the hazard class of the dam to ‘low’. Retrofit design plans are concurrently being developed by CPJ and will include the removal of the existing outfall structure, construction of a new weir wall. In the interim, CPJ has updated the Emergency Action Plan for Gudelsky Pond to meet new MDE and federal standards.
Gunner's Branch Stream Restoration
CPJ Environmental Services Department (CPJ) was awarded a contract with the Maryland-National Capital Park and Planning Commission (M-NCPPC) to provide consulting services for the stabilization of several severely degraded stream segments along Gunner’s Branch, Little Falls, and Paint Branch Streams in Montgomery County, Maryland. The purpose of the Task Order is to design restoration practices that will stabilize eroded areas and provide improvements to protect, repair, or replace existing infrastructure threatened by stream erosion. Per direction of Mr. Andrew Frank, Project Manager at M-NCPPC, CPJ conducted a series of field walks with M-NCPPC staff and other interested parties to review existing stream restoration concepts, discuss design approaches, identify site constraints and access points, investigate existing erosion problems and threatened infrastructure, and examine in-stream and riparian habitat improvement needs.
Design issues at the Gunner’s Branch project area included replacement of an existing pedestrian bridge as well as stream restoration design to reduce future impacts from stream erosion and improve accessibility. A 50’x8’ Pony Truss design with a Douglas Fir decking and weathering steel finish of similar design to the existing deteriorating bridge was proposed. A new bridge alignment was proposed to solve several of the design problems associated with the existing location. By locating along a stabile stream reach we reduced the chance that the abutments will be compromised in the future. CPJ also recommended a slightly extended bridge span due to the likelihood that the cross sectional area within the Gunner’s Branch will develop further and cause additional widening of the stream. The existing scour areas adjacent to the trail was stabilized through a combination of a stone toe and fill section, while the opposite stream bank will be excavated to maintain a stable cross section. The top of the banks were given added protection with the establishment of a single height log barrier to discourage access into the stream at these areas.