Indirect and Cummulative Impacts

Within the NEU, the Indirect and Cumulative Impact (ICI) and On-site Mitigation Groups are responsible for identification and development of on-site stream and wetland mitigation and T & E Buffer Conservation as well as analysis and minimization of ICI impacts.

Introduction to ICI in the Natural Environment Unit

Assessment of ICI is required under the national (NEPA) and state (NCEPA) environmental policy acts. In addition, regulations for NC's 401 Water Quality Certification require that the Division of Water Quality (NCDWQ) determine whether a project will "result in cumulative impacts, based upon past or reasonably anticipated future impacts, that cause or will cause a violation of downstream water quality standards" [15A NCAC 02H .0506 © (4)]. In 2002, NCDWQ issued a policy providing new regulatory guidance on implementing the existing portions of the 401 certification and isolated wetland rules that concern cumulative impacts. Evaluation of ICI is also required by the U.S. Army Corps of Engineers, NC Division of Coastal Management , the U.S. Fish and Wildlife Service.

ICI assessment provides an estimate of the indirect effects of a transportation project and the combined or cumulative effects of the project along with other past, present, or reasonably foreseeable future development activities. The primary focus is on the project's potential to induce growth and change land use (e.g., urban and suburban growth), that could in turn affect natural resources of the study area. The recent history of NCDOT and ICI assessment has been focused on the effects to water quality and aquatic species, however, other concerns have begun to emerge including habitat fragmentation, and terrestrial endangered plant and animal species.

Transportation improvements often reduce the time-cost of travel and improve access enhancing the attractiveness of surrounding land to developers and consumers. Development on vacant land or conversion of the built upon environment to more intensive uses is often a consequence of highway and transit projects. Urbanization and the associated increase in impervious surfaces typically result in an increase in stormwater runoff (total volume, magnitude and frequency of peak rates, and peak velocity), decreased infiltration, and an increase in certain pollutants. Without proper controls, these changes can in turn erode streambanks, degrade aquatic habitat, and adversely affect water quality.

The purpose of estimating indirect and cumulative impacts of proposed transportation projects is to contribute to the body of information that will support a decision about whether

to proceed with the plan or project, as proposed; to formulate a revised plan or project; or to otherwise mitigate adverse impacts associated with the proposed plan or project.

Definitions

The following definitions are taken from the NC administrative code containing rules for implementing NC's Environmental Policy Act (15A NCAC 01C .0103) and are similar to those in the NEPA regulations (40 CFR 1508.8).

Indirect Impacts or Effects (also Secondary Impacts):
Indirect impacts caused by and resulting from a specific activity that occur later in time or further removed in distance than direct impacts, but are reasonably foreseeable. Indirect impacts may include growth inducing effects and other effects related to induced changes in the pattern of land use, population density or growth rate, and related effects on air and water and other natural systems, including ecosystems.

Cumulative Impacts:
Environmental impacts resulting from incremental effects of an activity when added to other past, present, and reasonably foreseeable future activities regardless of what entities undertake such other actions. Cumulative impacts are the reasonably foreseeable impacts from individually minor but collectively significant activities.

Direct Impacts:
Environmental impacts which are caused by an activity and occurring at the same time and place.

Role of the Human Environment Unit

An analysis of indirect effects to the human environment is under the purview of the Human Environment Unit (HEU) within NCDOT. Both the N.E.U. and H.E.U. work cooperatively to produce a comprehensive assessment of indirect and cumulative impacts.

The Community Studies unit in the HEU is made up of urban planners who evaluate the growth potential resulting from transportation projects and the effects upon surrounding communities. These effects take the form of both direct and indirect impacts, and are documented within the Community Impact Assessment (CIA). The indirect and cumulative effects are typically in the form of increased urban and suburban development in response to increased access to land, labor and resources.

The analysis of project areas of influence includes a review of local land use planning, demographic trends, market forces, infrastructure and a variety of other factors that play a part in fostering urban and suburban development. In this way, a future urbanization scenario is devised from which effects and impacts to both the human and natural environment can then be estimated and described. The Community Studies unit, upon describing the future urbanization scenario and the effects upon communities, will then transfer this information to the appropriate NEU. staff who will then evaluate the future urbanization scenario for impacts to specific natural resources (this is particularly important for quantitative ICI assessments).

The HEU plays a central role in conducting project prescreening, land use projections, and the qualitative ICI assessment (steps 1 through 5 in Section 8.6 documented in an Indirect and Cumulative Effects or ICE report). Staff in the ICI Group review qualitative assessments conducted or coordinated by the HEU and assume the lead role in quantitative ICI assessments.

Levels of Analysis and Prescreening

There are at least three levels of analysis for ICI impacts.

Projects that have little or no anticipated impacts. Standard language has been developed to include in the environmental document and/or permit application. Examples would include standard bridge replacements, minor intersection improvements such as turn lanes, etc., and minor widening projects where the improvement consists of pavement widenings (10 ft. to 12 ft. lanes, etc.). Projects that follow the 8-step assessment process (see below) but do not require water quality modeling, thus requiring a coarser level of land use projections. The majority of transportation projects require a qualitative assessment of the project's potential to affect land use and foster development. Projects that follow the 8-step assessment process AND require a detailed water quality modeling analysis, requiring detailed land use analysis focused on parcel level data (quantitative analysis). Most often this is necessary when the project resides in an area where water quality is already degraded (303d waters) or that is considered environmentally sensitive (e.g., Trout and SA waters, endangered species). A key factor that would warrant detailed, quantitative analysis is a conclusion that project-induced land use changes would occur for which watershed management practices or programs would be inadequate. Typically, the detailed land use analysis would be performed on the least environmentally damaging practicable alternative (LEDPA) as part of the ICI assessment for the NEPA document while the detailed water quality analysis would be performed for the 401 Water Quality Certification.

Pre-screening of projects for ICI will evaluate whether or not the factors point to the need to commence a detailed, project-specific 8-step assessment. The pre-screening process is described in more detail within the pre-screening guidance document (see policy and guidance section).

Land Use Projections

The first step in the analysis of potentially significant indirect and cumulative effects is to assess the potential and magnitude of project-induced growth. This step is generally conducted or coordinated by the HEU. Once the level of induced growth has been assessed, impacts on the natural environment arising from development can be evaluated.

In order to analyze indirect/cumulative effects, the first step is an assessment of the magnitude and location of development induced by a project. Cumulative and indirect effects can be evaluated by comparing the Action and No-Action forecasts. The forecasts developed should include other activities in the study area that could impact notable features. At least two forecasts are necessary:

No-Action Forecast which describes future conditions in the absence of the project or plan; and An Action Forecast describing conditions in a future point in time following implementation of the project alternative or plan.

There are several types of qualitative and quantitative techniques for analyzing indirect effects. In a quantitative forecast exercise for indirect/cumulative effects, it is necessary to relate projections of population and employment with consumption of land. Unless this step is integrated into a formal land use model, the analyst must determine standards for land consumption by land use. Population can be related to land use by determining the number of units per acre and the average household size; similarly, employment can be related to land use by utilizing standards of employees per square foot or per acre for various types of commercial development.

In areas with established land use controls, the analyst may use zoning ordinances, anticipated plans, and historical trends to assist in development of scenarios.

In areas where land use is not widely controlled or where population projections have not been related to land consumption, it may be necessary to develop a no-action future scenario from the beginning utilizing assumptions about location choices and land consumption with and without the transportation improvement.

Encroachment-alteration effects arising from the project itself should also be assessed after induced growth impacts are explored so that these alteration effects can be fully understood in the context of future land uses. Encroachment-alteration effects include alteration of the behavior and functioning of the affected environment caused by project encroachment changes (physical, chemical, or biological) on the environment.

Eight-Step ICI Assessment

The NCDOT and NCDENR have established guidelines that present a systematic approach to indirect and cumulative impact assessment that includes the following steps:

Study area boundary (ies) - watershed/subwatershed boundaries are typically appropriate for assessing ICI downstream water quality impacts. However, each resource, whether it is water, plant or animal, will likely have a different study area based on the specific characteristics of that resource. Study area needs, directions, goals - the planning context accounts for local watershed/subwatershed plans (or lack thereof), specifically, what entities are involved, the effectiveness of such plans, and how such plans relate to current and future land uses. Notable features inventory - includes identification of potentially affected water bodies, their characteristics, water quality classifications, monitoring data, relevant water quality protection regulations, and extent of impervious cover in the study area. Other notable features can include conservation lands, National forests, State and Local parks, etc. Cause-effect relationships between past, present, and future actions and downstream water quality, i.e., what are the major sources of pollutant loadings and what measures have been taken to control these sources. Identification of significant ICI issues - includes assessment based on Steps 1-4 of whether existing measures and controls are sufficient to protect downstream water quality in light of potential indirect and cumulative impacts. Note: Step 5 is where the decision is made between a qualitative or more complex, quantitative analysis in accordance with the Division of Water Quality policy regarding cumulative impacts. This decision is likely to occur during NCDWQ's review of the draft EIS or at Concurrence Point 3 of the Merger process. The ICI Group should be notified by the PDEA project planning engineer (In-house Group) or consultant engineer (Consultant Group) when a quantitative ICI may be required. Detailed analysis (if significant issues are identified) - estimates of future land use changes through detailed analysis used as input to quantitative water quality analysis. Assess results - reasonableness and sensitivity to varying assumptions. Develop mitigation - to address needs for improved watershed management identified by the analysis.

The NCDOT/NCDENR Guidance on Integrated NEPA/SEPA/401 Eight-Step ICI Assessment provides more detail of this process.

Water Quality Modeling

The decision to conduct a quantitative water quality analysis (from Step 5 above) will typically call for the use of water quality models. Mathematical simulation models have been used in water quality planning and pollution control for decades. Models provide the ability to understand and evaluate complex environmental processes of source, transport, transformation, and fate of pollutants. They are essential in evaluating future conditions and the effects of land use changes and various management alternatives.

Numerous watershed loading and receiving water quality models are available. Descriptions and reviews are available to assist in selecting the appropriate model (McKeon and Segna 1987; Donigian and Huber 1991; Shoemaker et al. 1997; Deliman et al. 1999; Fizpatrick et al. 2001; Novotny 2003). Watershed loading or runoff models are aimed at predicting pollutant movement from the land surface to waterbodies. Receiving water models evaluate the response of a waterbody to pollutant loading. Some runoff models include transport and transformation routines and thus have some elements of receiving water models.

Development of a model consists of four primary steps: (1) identify the issues and objectives the model should address, (2) develop a conceptual model of important environmental processes and parameters, (3) select the modeling framework, and (4) develop the site-specific application tool (Council for Regulatory Environmental Modeling 2003).

Selection of Modeling Framework

Models are neither universally applicable to all watersheds and water bodies, nor capable of describing all environmental processes. An appropriate modeling framework must be selected for the quantitative ICI analysis following the identification of project objectives and the important environmental processes.

Model selection and its desired complexity will typically depend on the project goals, objectives, and management issues, as well as site-specific environmental characteristics, resource constraints, data availability, the parameters of concern, and the spatial and temporal scales of interest . Selection should be based on how the model meets the management need (e.g., the 401 WQ Certification), and not by the level of sophistication with which it describes the watershed system. Often, selection of the simplest approach that adequately addresses the management question with an acceptable level of uncertainty should be used. However, the consideration, documentation, and analysis requirements should be commensurate with the potential for and magnitude of adverse impacts. Therefore, if a simpler approach indicates (or will likely indicate) the potential for considerable impacts, a more complex approach may be appropriate.

In a survey and assessment of water quality models, the Water Environment Research Federation (Fizpatrick et al. 2001) suggested the consideration of the following criteria during the model selection process:

Record of successful application Level of analysis (screening versus detailed) Spatial and temporal scale Pollutants and processes represented Resource requirements Input and output aids Model support (documentation and technical support) Model availability (public domain or proprietary)

Examples of models commonly used to evaluate the water quality impacts of land use change and urbanization include the Generalized Watershed Loading Functions (GWLF), Soil and Water Assessment Tool (SWAT), Hydrological Simulation Program Fortran (HSPF), and Storm Water Management Model (SWMM). Models have differing needs with regard to inputs (e.g., land use), some involving greater or lesser levels of detail and effort.

The parameters of concern may include upland loads of nitrogen, phosphorus, sediment, and fecal coliform bacteria. In addition, the analysis will likely consider the impacts to watershed hydrology such as increases in peak velocity and runoff volume, and the potential to erode receiving stream channels (stream erosion may be evaluated directly or indirectly as appropriate). A special focus should be placed on the parameter(s) considered to have the greatest impact on the resource (e.g., trout waters and sediment, SA waters and fecal coliform, nutrients and nutrient sensitive waters, and 303(d) waters = parameter causing impairment).

Scoping

In the N.E.U., water quality modeling will typically involve coordination with a private consulting firm unless in-house resources are available. The firm selected should have staff with an appropriate educational background, training, and experience in conducting modeling of watershed runoff and pollutant loading. In addition, the consulting staff should have an adequate understanding of the science embodied within the particular model(s) selected for the project as well as experience applying them.

Following the request for proposal, the project scope should be developed jointly between PDEA, the consulting firm, Community Studies unit, and the ICI Group. Approval of the modeling framework and study area boundary by NCDWQ is recommended and should occur during a meeting with the agency prior to finalizing the scope. Once a scope is finalized, the cost estimate approved, and a notice to proceed received, work by the firm may begin. The firm should provide updates and request input as appropriate during key points of the project.

Documentation Requirements

Modeling reports should contain the following components:

Executive summary Introduction and objectives Data collection and synthesis Model selection and justification Model description Model development and parameter estimation Model calibration, confirmation/validation, and results 1 Uncertainty and sensitivity 2 Model application and scenario analysis Key assumptions and limitations Mitigation recommendations Conclusions References Staff Qualifications

Data available for calibration and confirmation will vary depending on the project. At a minimum, a qualitative discussion is required.

Model documentation should convey key results and important model limitations to nonmodelers in the simplest manner possible, as well as contain sufficient detail for model reviewers to critically evaluate the application. The content of the report should be consistent with the scoping document.

Model Review and Approval

The ICI Group is responsible for reviewing the ICI modeling documentation for technical and policy requirements. NCDWQ may be consulted for review of a draft report, following NCDOT's review and refinement of a first draft. Approximately 3 to 4 weeks should be allocated for a NCDWQ review. Any detailed technical review of the model application (internal or external) should be conducted by personnel with expertise in water quality modeling.

The Council for Regulatory Environmental Modeling (2003) has identified some best practices for model evaluation that may be consulted for assistance.

In addition to paper copies of the modeling report, the final deliverable should include a CD with the report in electronic formats (MS Word and Adobe Acrobat), the model application, and supporting files. Multiple copies of the final report will be provided to the permit specialist for permit applications and agency review.

Mitigation

The results of the ICI analysis may be used to assist NCDOT, NCDENR, and local governments in evaluating alternative methodologies to mitigate the indirect impacts of projects. Mitigation responsibility for indirect and cumulative impacts of transportation projects proposed by NCDOT is based on the distinction between those effects that are within and outside the control of NCDOT.

Encroachment-alteration effects can be equated to within the control of NCDOT, while induced growth and effects related to induced growth are generally outside the control of NCDOT (the exception being to avoid or minimize impacts through change in access location, where practicable). Commitments for mitigation outside of agency control may be required as a condition of permit approval by NCDWQ or as a conservation measure by USFWS (e.g., approval of an enhanced local ordinance to minimize stormwater impacts).

Policy and Guidance

Guidance for Assessing Indirect and Cumulative Impacts of Transportation Projects in North Carolina Volume I: Guidance Policy Report. Prepared For State of North Carolina Department of Transportation/Department of Environment and Natural Resources. Prepared By The Louis Berger Group, Inc. November 2001. Guidance for Assessing Indirect and Cumulative Impacts of Transportation Projects in North Carolina Volume II: Practitioner's Handbook. Prepared For State of North Carolina Department of Transportation/Department of Environment and Natural Resources. Prepared By The Louis Berger Group, Inc. November 2001. DRAFT Internal Policy Cumulative impacts and the 401 Water Quality Certification and Isolated Wetland Programs. NC Division of Water Quality. October 3, 2002. Version 1.6 Revision to NCDOT/NCDENR Guidance for Assessing Indirect and Cumulative Impacts of Transportation Projects in North Carolina - Volume II: Practitioner's Handbook. Section II: Pre-Screening Projects for Applying Indirect/Cumulative Impact Assessment. January 14, 2004. NCDOT/NCDENR Indirect and Cumulative Impact Assessment Guidance: Integrated NEPA/SEPA/401 Eight-Step ICI Assessment Process. January 21, 2004. Handbook on Integrating Land Use Considerations into Transportation Projects to Address Induced Growth. Requested by AASHTO Standing Committee on the Environment. Prepared by ICF Consulting. NCHRP Project 25-25(3). March 2005.

References

Council for Regulatory Environmental Modeling. 2003. Draft Guidance on the Development, Evaluation, and Application of Regulatory Environmental Modeling. Draft - November 2003.

Deliman, P.N., R.H. Glick, and C. Ruiz. 1999. Review of watershed water quality models. US Army Corps of Engineers Waterways Experiment Station. Technical Report W-99-1.

Donigian, A, S. Jr. and W. Huber. 1991. Modeling of nonpoint source water quality in urban and nonurban areas. U.S. Environmental Protection Agency, Washington, D.C. US EPA 600/3-91/039.

Fitzpatrick, J., J. Imhoff, E. Burgess, and R. Brashear. 2001. Water quality models: a survey and assessment. Water Environment Research Federation Project 99-WSM-5.

McKeon, T.J. and J.J. Segna. 1987. Selection criteria for mathematical models used in exposure assessments: surface water models. US EPA Office of Health and Environmental Assessment. Washington, D.C. EPA/600/8-87/042.

Novotny, V. 2003. Water Quality: Diffuse Pollution and Watershed Management. Second Edition. John Wiley and Sons, Inc. New York.

Shoemaker, L., M. Lahlou, M. Bryer, D. Kumar, and K. Kratt. 1997. Compendium of tools for watershed assessment and TMDL development. US EPA Office of Water, Washington, DC. EPA841-B-97-006.

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