Client

Maryland Transit Administration

Key Services

  • Delineations
  • Groundwater Monitoring
  • Hydrology and Hydraulics
  • Mitigation Planning and Design
  • Agency Coordination
  • Permitting
  • Designated Specialist Construction Services

Project Details

The Purple Line is a light rail transit project connecting Prince George’s and Montgomery Counties in Maryland.  Unavoidable impacts to wetlands totaled 0.8 acre of forested and emergent wetlands.  Project impacts to wetlands were required to be mitigated in accordance with the Clean Water Act.

CRI conducted an extensive site search within the affected watershed for suitable mitigation opportunities.  The site is situated within the 20.2-acre Ken-Gar Palisades Park in Montgomery County, a multi-use recreational park owned by Maryland-National Capital Park and Planning Commission (M NCPPC) and identified as the preferred compensatory mitigation wetland site for the Purple Line Project in consultation with the regulatory agencies. The wetland creation areas for the site abut existing wetlands and forest, which connect to Rock Creek via an unnamed tributary.  The entire park is located within the 100-year floodplain.

Natural resource inventories were conducted to document existing conditions and provided the basis for the restoration design. CRI performed wetland and forest stand delineations, wetland functional assessments, soil borings and analysis, and hydraulic modeling to develop a water budget.  Groundwater monitoring wells were installed, and data was collected monthly for several years.  Invasive species inventories were conducted, and an Invasive Species Management Plan was developed.

CRI was the lead designer for the Ken-Gar wetland creation project. Project goals include creating 1.43 acres of palustrine forested, 0.23 acre of palustrine emergent (PEM) wetlands, and enhancing 1.90 acres of existing PEM wetland on site.  Enhancement of the existing emergent wetland will include treatment of the invasive common reed (Phragmites australis), broad-leaf cattail (Typha latifolia), and reed canary grass (Phalaris arundinacea) that currently covers the majority of the wetland.  The wetland creation design also included the relocation of the current soccer field.

CRI developed the preliminary investigation and concept design (30%), semi final design (60%) and final design (90%) report, plans, specifications and estimate. CRI also presented the design strategy to stakeholders and review agencies at milestone meetings. In addition, contract documents (100%), including plans, specifications, and estimates required for project advertisement were prepared.  Coordination with the M NCPPC regarding access, safety, design features, and vegetation and wildlife management was conducted extensively throughout the project.

CRI prepared the Federal/State Joint permit application and plates for impacts to obtain the wetland and waterway construction authorization associated with the wetland mitigation project.  Post construction monitoring protocols were developed, and CRI will also provide designated specialist construction services during construction of the wetland creation site.