Investigation and Assessments

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Investigation and Assessments

Floodline Mapping Studies

CRA has the technical in-house capabilities to prepare floodplain delineation studies.  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 EPA SWMM5. 

CRA also has leading-edge capabilities in the preparation of two- and three-dimensional (2D and 3D) modeling studies using ECOMSED and GEMSS (Generalized Environmental Modeling System for Surface Waters).  ECOMSED is a fully integrated three-dimensional hydrodynamic wave and sediment transport model, designed to simulate time-dependent distributions of water levels, currents, temperature, salinity, tracers, cohesive and noncohesive sediments, and waves in marine and freshwater systems. GEMSS is an integrated system of 3D hydrodynamic and transport models embedded in a geographic information and environmental data system (GIS) with a set of pre- and post-processing tools to support the 3D modeling.

Development Impact Assessments

Development impact assessments, conducted in the planning stages of a development, provide the necessary information to determine potential impacts that proposed activities may have on the environment and natural resources within the study area.  Working in conjunction with municipalities, conservation authorities, and other interested parties, CRA has prepared numerous development impact assessments.  CRA tailors these assessments to the unique features of each site and end-user needs.

Water Balance Studies and Long Term Water Availability Assessments

Water balances can be prepared using a variety of techniques, including relatively simple and straightforward methods such as the Thornthwaite, Priestly-Taylor and Mather method or through continuous simulation of the hydrologic cycle over a period of 30 years.  Both methods are used to determine system inputs (rainfall, snowfall and solar radiation) and losses (evapotranspiration, direct runoff, and infiltration) to determine water availability and impact on existing natural resources.

Water balance studies are also applied in the assessment of landfill site leachate collection system performance, where water inputs to a system are calculated through the hydrologic analysis and leachate collection volumes are recorded.  Discrepancies between the volume of water collected by the leachate collection system and the calculated water inputs are highlighted through preparation of the water balance and the performance of the system is assessed.  Water balances are also used to assess water availability for such applications as irrigation on a golf course or influent water to sustain a wetland.

Water and Sediment Quality Assessments

Water quality assessment is important when determining baseline conditions in rivers and streams as well as effluent characterization, be it from a stormwater management pond or process discharge.  Characterization of both flow streams is necessary when developing allowable discharge limits to natural environments.

Since many pollutants released into our waterways settle out or adhere to larger sediment particles, sediment analysis represents an important step in evaluating and determining the nature and extent of any impacts related to historic discharge of pollutants into the environment.  Sediment quality assessment allows characterization of the contributing watershed and can be used to date development of the watershed based on the stratification of the sediments.  In pond and riverine systems, sediment analysis is critical when considering dredging activities.  Characterization of the sediment is necessary to determine disposal options and handling risks that will be encountered during the dredging activities.  Assessment of baseline sediment quality within a receiving water body may also be important for new developments with proposed discharge systems.

CRA has several numerical water quality models, including the US EPA SWMM5 model, PC SWMM, and XP SWMM models. CRA can also analyze the transport and fate of conservative and first-order decaying sediment-bound tracers in cohesive and non-cohesive aquatic sediment environments.

Receiving Stream Assimilative Capacity Studies

Assimilative capacity studies are necessary when establishing effluent water quality objectives and limits for effluent discharges to water bodies such as stormwater, process water, or municipal sewage.  Based on water quality characterizations undertaken for both the discharger and the receiver, limits may be established that ensure the environment will not be adversely impacted as a result of the discharges.

CRA has capabilities to perform 2D mixing analyses using the US EPA supported CORMIX and Visual Plumes models. Both programs represent computer tools for predicting the qualitative features (flow classification) and the quantitative aspects (dilution ratio, plume trajectory) of the hydrodynamic mixing processes resulting from different discharge configurations.

CRA also has expertise in modeling mixing in near-field and far-field hydrodynamic regions using sophisticated 3D hydrodynamic models such as ECOMSED and GEMSS. Both conservative and first order decay simulations can be performed to determine the fate and concentration of effluent tracers in the receiving stream based on the tracer's chemical characteristics.

Benthic Bio-Monitoring Assessments

Water quality is commonly assessed based on individual samples, representing a snapshot in time.  Benthic macroinvertebrate investigations provide inferred sustained water quality information based on the presence of aquatic life and diversity within creek, river, or lake systems.  These assessments are commonly used to:

• Establish discharge criteria
• Provide baseline water quality conditions prior to site development
• Develop protection plans to prevent degradation of the water course
• Monitor the effects of changes to effluent and discharge criteria on a receiving water body
• Identify enhancement opportunities

 

Assessment of historic benthic environments may be conducted in a lake system.  Using buried lake sediment, these assessments can approximate historical water quality conditions.  This information is useful for assessing long-term change in a study lake or pond, providing reference (undisturbed) conditions for that system and timing of change. Benthic bio-monitoring assessments can provide water quality information in the absence of directly measured water quality data.  These historical assessments are most beneficial on long-established sites of degraded water quality. 
 
CRA's staff are fully qualified to conduct benthic bio-monitoring assessments, and have conducted them for a variety of industrial and municipal clients.

Habitat Assessments

Habitat assessments represent an inventory that documents plants, animals, and fish within a study area, as well as the potential for that area to support the various populations.  These assessments are necessary to identify constraints on proposed developments or areas that would benefit from potential enhancement. 
Ecological site assessment is the process by which ecological resources within an area of interest are identified and their functions within the ecosystem are evaluated.  These assessments are conducted for a variety of reasons as they can:

• Provide a baseline that can be used to evaluate impacts of a proposed or approved project
• Monitor changes in conditions over a period of time
• Be used to evaluate the feasibility of a land purchase or proposed project

 

For example, it is useful to know if one or more sensitive resources, such as wetlands or threatened and endangered species, are present within a project area before proceeding with plans for development or other action that might impact sensitive resources.

The level of effort required for an ecological site investigation depends on several factors, such as the purpose of the investigation and availability of existing data.  In some instances, ecological resources can be adequately characterized with limited fieldwork and use of existing data.  For example, ground truthing may identify the habitats present, and available natural resource inventories can be used to identify resources expected to be associated with each habitat.  In other cases, a comprehensive field survey may be required, such as the historical occurrence of a species of concern on or near a project site. 

CRA has conducted ecological site investigations throughout North America for a diversity of habitats and ecosystems.  Our experience includes characterization of benthic macroinvertebrate and fish communities, water quality assessments, characterization of plant and wildlife communities, habitat assessments, surveys for threatened and endangered species, and wetland assessments.  CRA works closely with our clients to identify their needs and conducts ecological site investigations with a level of effort commensurate with the project objectives in a cost-effective manner.

Wetlands Evaluations

Wetland evaluation, including delineation, is an important constraint on most development and remediation projects.  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.  In other cases, habitat creation or restoration may be a proactive measure, such as stabilization of stream banks or other areas prone to erosion; vegetative cover following closure of landfill to attract birds and other forms of wildlife; or naturalization of stormwater management basins. 

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's staff is fully capable of delineating wetland limits and negotiating buffer limits intended to prevent adverse impacts to the wetland form and function.  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.

Erosion and Sediment Transport Studies  

Wetland evaluation, including delineation, is an important constraint on most development and remediation projects.  The 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.  In other cases, habitat creation or restoration may be a proactive measure, such as stabilization of stream banks or other areas prone to erosion; vegetative cover following closure of landfill to attract birds and other forms of wildlife; or naturalization of stormwater management basins.   

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's staff is fully capable of delineating wetland limits and negotiating buffer limits intended to prevent adverse impacts to the wetland form and function.  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.

Fluvial Geomorphic Evaluation

The natural form and function of a river as it matures and develops over time is related to its hydrology, the topography of the watershed, and the sedimentology within the river system.  All of these factors must be considered when introducing change to the watershed through development or when restoring sections of a channel to ensure that the design is resilient and long-lasting.  Assessment of bed materials, bed load, meander patterns and pool and riffle sequences all form part of geomorphic investigations prepared by CRA.  This information is then used to develop restoration plans or discharge limits for proposed developments. 

Sewer Inflow/Infiltration (I/I) Studies

Sewer inflow and infiltration studies are the most efficient method of identifying rainfall related inflow into sanitary sewer networks, thereby minimizing the infrastructure required to serve a community.  CRA provides services to install and monitor flow monitoring equipment in the sewer collection network.  This is performed to identify areas where significant inflow and infiltration occurs and to facilitate further studies to either disconnect inflow sources such as connected roof drains or reduce infiltration resulting from failing infrastructure. 

CRA also provides modeling services that can assist in developing "what-if" scenarios for prediction of anticipated flow rates to a water pollution control plant or the reduction in flow resulting from remediation works in a sector of a service area.