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Trotter Road Streambank Stabilization


Trotter Rd, Clarksville, MD, USA

Page owner: JMT (Johnson Mirmiran & Thompson, Inc.)

Project Overview
Project Name: Trotter Road Streambank Stabilization
Date Completed: 2014
Location: Clarksville, Maryland, United States
Project Status: Complete

Project Tags: water stream hydrogeologist

Project Team

Disciplines That Worked on Project

Civil Engineer: Construction ManagementCivil Engineer: Environmental (Stream / Waterbody restoration)Civil Engineer: GeotechnicalCivil Engineer: Site Design (Land development)Civil Engineer: Site Design (Site development stormwater)Civil Engineer: TransportationCivil Engineer: Water (Flood study)Civil Engineer: Water (Site development / transportation stormwater)
People That Made The Project Happen (e.g., engineers, scientists, etc.)
Organizations That Made The Project Happen (e.g., engineering companies, government agencies, etc.)

Project Details
About this project
This project kept a road safe and protected the water quality of the stream.
The banks of a stream adjacent to Trotter Road in Howard County was experiencing significant erosion. If the streambank erosion continued, the stream would get wider and undercut the soil beneath the road. This would eventually damage the road, which is used by about 2,000 vehicles each day. In addition, the streambank erosion was washing soil into the stream and reducing the stream’s water quality. The stream’s use is designated by the State of Maryland as “Recreational Trout Waters and Public Water Supply”. The county previously tried to stabilize the streambank by dumping rock and spraying concrete (i.e., shotcrete) on the embankment. These efforts only worked temporarily.

This project involved designing a long-term solution to stabilize several hundred feet of stream bank. In 2009, JMT conducted an in-depth investigation of the stream channel and streambank slope. This included water resource engineers conducting field work to determine the stream classification. They also computed the amount of water the stream could handle before it overtopped its banks. Geotechnical engineers conducted a geotechnical field investigation and performed geotechnical engineering analysis based on soil borings completed by a subconsultant.

Based on the analysis, JMT identified five slope stabilization options for the client (i.e., Howard County) to consider. The options were slurry grouting, gabion slope stabilization, imbricated rip-rap slope stabilization, a conventional cantilevered retaining wall structure, and a secant pile retaining wall.

Based on an analysis of the cost and environmental factors, the agreed-upon solution was an imbricated rip-rap slope stabilization. Imbricated rip-rap is stones stacked together to form a wall. This prevents the soil from washing away and stabilizes the streambank. This option would stabilize the roadway while minimizing stream disturbances.

The benefits of the imbricated rip-rap option included:
- Proven technique that’s been used extensively in stream restoration projects
- Most natural looking option
- Minimal maintenance requirements

JMT designed the project, assisted with permit coordination, and provided oversight during construction as required by the client. JMT also provided post-construction baseline and year one monitoring.
Who benefits from this project, and how?
The people in 2,000 vehicles each day who use the road benefit from the project. If the project had not been completed, the road would have eventually been damaged and would need to be closed.

This project also protected the stream by reducing the amount of soil that erodes into the water. The stream is an unnamed tributary of the Middle Patuxent River, which drains to the Patuxent River, which drains to the Chesapeake Bay. Therefore, in a small way, this project also protects the Chesapeake Bay, which is home to about 300 species of fish, shellfish and crab species.
Environmental considerations
Where possible, the rip-rap was designed to tie into existing bedrock to reduce the potential for undermining and surficial erosion. Landscaping plans were developed for reforestation of areas within the limits of disturbance using native herbaceous, shrub, and tree species. Live stake plantings were proposed in areas near the stream channel to provide habitat and vegetative stability.

As a result of the project, the streambanks are stabilized. This improves the stream water quality and the nearby road.

Funding & Costs
Funding source: Public
Project cost: $$

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