Reference

Barbara Allera-Bohlen, 410-545-8633

Maryland State Highway Administration (SHA)

Project Highlights

  • Stream Geomorphic Assessment
  • H&H Analysis
  • Design Plans, Specifications and Estimate
  • Agency Coordination
  • Construction Inspection

Project Details

pic_proj_hammond

The mitigation for impacts along US Route 29 consists of stream restoration and water quality improvements along Hammond Branch within the Patuxent River watershed. The Hammond Branch Mitigation Site is located in a developing area of Howard County, north of the existing MD 216 between Leishear Road and the westbound ramp (Ramp E) from Interstate 95.

In this reach, past channelization confined the stream and disconnected it from its floodplain. This channelization led to eroding streambanks that threatened adjacent properties and impaired water quality and aquatic habitat.

Design

Stream restoration techniques were proposed at five design points that include floodplain grading along a 2,000 linear foot reach as a water quality enhancement. The water quality enhancement goals include:

  • Flood storage and flood relief
  • Reduction of sediment loads and bank erosion
  • Creation of habitat zones for aquatic species
  • Infiltration/groundwater recharge

Floodplain was created throughout the proposed reach by excavating soil from the floodplain and lowering the floodplain to the bankfull bench elevation. This elevation would allow flows from Hammond Branch to access the floodplain during storm events. Vegetation within the new floodplain bankfull bench is a mix of wetland and upland species.

CRI provided and reviewed all existing geomorphic data including channel cross sections, profiles surveys, and pebble counts. CRI assisted the Engineers in the development of additional proposed conditions cross sections and reviewed the results of the proposed conditions channel hydraulics model.

CRI also assisted the Engineers in preparing construction documents including plans, specifications, and estimates. Pre-bid services were also provided by CRI.

Construction Inspection

CRI provided Construction Inspection activities throughout the construction phase of the project including overseeing daily activities of the environmental construction contractor building streambank stabilization, stream channel realignment, grade control, bioengineering, wetland creation, and riparian buffer mitigation sites in the Hammond Branch watershed. CRI routinely inspected survey stakeout, sediment and erosion control measures, grading operations, plantings and soil bioengineering for conformance with approved design plans. CRI oversaw the construction of instream structures such as rock cross vanes, log vanes, imbricated riprap wills, and step-pools. CRI ensured that all construction activities are in strict compliance with numerous project permits and special conditions. CRI coordinated with the SHA project engineer and contractors when field changes were necessary to meet the design intent of the project plans.