Design and Construction

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Design and Construction

Flood Plain Delineation and Redefinition

CRA has the technical in-house capabilities to prepare floodplain delineation studies.  These studies can be prepared using the United States Army Corps of Engineers (US ACE) Hydrologic Engineering Center's (HEC) HEC-2 software or US ACE HEC's River Analysis System (HEC-RAS).  Floodline mapping can also be prepared using the Extran module in PC SWMM, XP SWMM or using EPA SWMM5.

Flood-Proofing Measures

CRA's design services group provides detailed structural design to provide flood-proofing measures for structures located in areas prone to frequent flooding in order to ensure protection of property.

Stormwater Management Facilities

CRA provides engineering and design services for water quality and water quantity treatment to minimize the impact of development on receiving water courses and the environment.  Stormwater management facilities include application of a variety of "best management practices" ranging from vegetated treatment swales to buffer strips to detention ponds as appropriate for each individual site location and needs.

Grading and Drainage Plans

CRA provides engineering and design services for proposed developments and re-development activities to ensure protection of property, ease of accessibility and economical development of the site.

Sediment and Erosion Control Plans

CRA offers design services for preparation of sediment and erosion control plans for implementation during construction activities in compliance with current federal NPDES, state, and provincial regulations.  Sediment and erosion control plans are required as part of most construction projects where significant areas of land will be disturbed and left exposed for the duration of construction.

Stream Naturalization and Rehabilitation

Restoration and enhancement of creeks, streams and watercourses is complex.  Many processes and factors associated with flow and function must be taken into account.  These processes and factors include, but are not limited to, hydrology (surface water and groundwater), hydraulics, erosional forces, and water quality.  These assessments are conducted at an ecosystem scale, considering both the aquatic and terrestrial ecological resources associated with the stream and watershed.  These resources may include wetlands adjacent to or hydrologically connected to a stream.  Due to this complexity, successful and effective stream restoration and enhancement requires expertise from a wide variety of engineering and scientific disciplines.

To provide our clients with the highest level of services possible, CRA has assembled a diverse and experienced team of engineers, hydrologists, water quality specialists, ecologists, and wetland scientists to design and implement stream restoration and enhancement projects.

CRA professionals have training and experience in the application of United States Army Corps of Engineers (US ACE) Hydrologic Engineering Center's (HEC) HEC-2 software or US ACE HEC's River Analysis System (HEC-RAS), Instream Flow Incremental Methodology (IFIM), Rosgen Methodology, and Habitat Evaluation Procedures (HEP).

Shoreline Stabilization

CRA provides expertise in the area of shoreline engineering services in stream, river,  lake and ocean environments.  This expertise covers a range of coastal and river engineering services, including shoreline and erosion protection design, sediment transport and pollutant fate studies and remedial design.  CRA provides specialist advice, based on varied and long experience, in the development of unique, cost-effective solutions that meet our clients needs and requirements.

CRA engineers have worked on shorelines subject to wave climates ranging from the ocean to the Great Lakes to small ponds.  CRA engineers have worked on continental rivers to major rivers to the smallest streams and creeks.  CRA engineers have worked in environments ranging from the Gulf to the Arctic, on projects across the US and Canada.

CRA utilizes state-of-the art numerical tools and computer models that have wide acceptance in the engineering and regulatory communities.  This assures our clients of both quality work and results that will be quickly approved.  In addition, when required, CRA is able to employ physical modeling approaches.  CRA engineers also employ specifically written numerical tools for sediment transport studies where the client issue exceeds available modeling tools.

CRA has expertise in cohesive and non-cohesive sediment transport studies using state-of-the-art three-dimensional models.  Hydrodynamic components of these models can be used to generate 3D matrices of shear velocities required in the design of shoreline and river bank protection measures.  The models can also be used for simulating oil spills or simulating the trajectories of floating objects.

CRA provides these services to private clients, local and state governments and other clients in the following areas:

Design

• Shoreline and river bank stabilization and protection
• Gravel and cobble beaches
• Nourished sand beaches
• "Soft" shoreline protection design
• Scour protection
• Armor block revetments
• Artificial islands
• Oil production and exploration islands
• Marinas
• Dredging program design
• Design/build

 

Computer Numerical Modeling

• Ice pile-up modeling and design
• Ice jamming modeling
• Oil spill containment modeling
• Hydrodynamic modeling of complex hydraulic environments
• Cohesive and non-cohesive sediment transport modeling

 

Physical Modeling

• Shoreline protection
• Nourished beach studies
• Toe scour protection

 

Aquatic Habitat Compensation and Mitigation

There are many reasons why corporate and government entities create or restore habitat for fish and wildlife.  Creation of new wetlands may be a condition of permits issued by federal or state regulatory agencies.  Primary or compensatory restoration may be a condition of a negotiated settlement for natural resource damages.  Habitat restoration may be offered as a Supplemental Environmental Project (SEP) in lieu of a fine for a regulatory violation. 

Prior to developing a habitat creation or restoration plan, the quality and functions of the habitats being replaced are often characterized.  CRA has a staff of highly qualified field biologists experienced in conducting surveys of flora, fauna, and threatened and endangered species, as well as performing quantitative and semi-quantitative functional habitat assessments, using tools such as Habitat Evaluation Procedures (HEP).  CRA has also prepared habitat creation and restoration plans for a diversity of habitat types, including all types and forms of wetlands, stream banks and channels, and riparian corridors.  In addition to design, CRA can oversee construction or restoration activities and monitor the success of the created and restored habitats.

Constructed Wetlands Treatment Systems

Engineered wetlands are suitable for low flow, long term treatment scenarios.  CRA maintains expertise in the use of engineered wetlands for the treatment of heavy metals, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs) in soil and groundwater.  CRA has conducted the following engineered wetlands projects:

• Site remedy at a chemical manufacturing facility as part of a conceptual design (90% complete) for the use of engineered wetlands to treat mercury and chlorinated solvents in groundwater
• Two-year evaluation of ability of wetland plants (cottonwood and cattails) to metabolize and breakdown trichloroethene (TCE) in groundwater at a solvent recycling facility

 

CRA also recently constructed a pilot wetland using native and nursery stock Typha plants for the treatment of metals in acid mine drainage.  The wetland was constructed during the summer of 1998 at a non-active copper mining site.  Drainage from a tributary is diverted to the wetlands via a dam constructed across the tributary.  The drainage contains iron, copper, manganese, and other metals and has a typical pH range of 3 to 4.  Flow volumes of 200 to 600 gallons per minute (gpm) enter the wetland and are regulated using a butterfly valve.  The wetland divides into nine cells constructed of concrete barriers with limestone aggregate, native fill, hay bales, organic strata (mushroom compost), and aquatic plants over a geosynthetic clay liner.  CRA initiated weekly sampling in October 1999.  The wetland is currently working as predicted with reduction of both total and dissolved metals as well as increase in discharge pH to 6 to 7.  If the pilot project is deemed successful, as many as 40 more acres of wetlands will be constructed.

In conjunction with wetlands treatment, the CRA has investigated the use of phytoremediation and natural attenuation.  Phytoremediation is suitable for erosion control, limited groundwater control, and potential uptake/degradation of pollutants.  CRA is studying the applicability of the following areas:

1. Selection of appropriate plant species for site remediation and design of a tree/sapling planting and husbandry plan
2. Investigation of approaches to native plant propagation to allow field testing of pollutant uptake potential
3. Testing of plant species for uptake potential in a controlled environment

 

Natural attenuation involves the use of anaerobic and aerobic zones to degrade pollutants in situ.  The environmental conditions present can be enhanced to aid in the degradation process.  CRA has developed innovative remedial concepts for specific applications and is investigating methods to apply amendments to enhance natural degradation, including horizontal drilling, ORC socks, bedrock fracturing, and deep reactive barriers.

Design/Build

CRA offers the capacity to provide design build services for all engineered solutions that we provide.  Design build offers faster completion, a single point of contact responsible for all aspects of the project from design through construction, high quality, cost savings since design and construction personnel work and communicate as a team to evaluate alternative materials and methods efficiently and accurately, time savings since bidding periods are eliminated, and development of guaranteed construction costs at an early stage in the project.