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National Environmental Policy Act / Clean Water Act
Section 404 (NEPA/404) merger process and agreement
for transportation projects in Colorado.


In a May 12, 2003, letter from Mr. James L. Connaughton, Executive Office of the President, Council on Environmental Quality, to Mr. Norman Y. Mineta, Secretary of Transportation, Mr. Connaughton advises, "In situations involving two or more agencies that have a decision to make for the same proposed action and responsibility to comply with NEPA or a similar statute, it is prudent to jointly develop a purpose and need statement that can be utilized by both agencies". For transportation projects requiring a Clean Water Act (CWA) Section 404 permit, both the Federal Highway Administration and U.S. Army Corps of Engineers have a decision to make regarding the same project.

Parties to this Agreement:

Signatory agencies
Colorado Department of Transportation
US Army Corps of Engineers
US Department of Transportation, Federal Highway Administration

Participating non-signatory agencies
US Environmental Protection Agency
US Department of Interior Fish and Wildlife Service


The purpose of this agreement is to establish a procedure and provide guidance to ensure that documentation and coordination conducted to comply with the National Environmental Policy Act will meet the standards of all signatories and that any preferred alternative selected under this joint National Environmental Policy Act (NEPA) / CWA Section 404 decision-making process also complies with CWA Section 404(b)(1) guidelines. These procedures do not supersede lead agency NEPA decision-making requirements.


The National Environmental Policy Act (NEPA) requires federal agencies to consider the environmental effects of, and any alternatives to, their proposed actions. The Federal Highway Administration (FHWA) is the NEPA lead federal agency for federally funded roadway projects proposed by the Colorado Department of Transportation (CDOT). A CDOT action that involves the placement of fill material into a water of the US also requires a CWA Section 404 permit (Permit) from the US Army Corps of Engineers (USACE). If the Permit required is a Standard Individual Permit (IP), the USACE must determine compliance with the CWA and NEPA prior to issuance of the Permit.

USACE may choose to participate as a cooperating agency in the NEPA process conducted by FHWA and CDOT, which provides the USACE the ability to adopt the FHWA/CDOT NEPA documentation for determining whether the proposed project is in compliance with the CWA and for determining USACE compliance with NEPA. In such cases, the Purpose and Need statement developed by FHWA and CDOT should be developed in a manner that allows the USACE to define the CWA required "overall project purpose".

The USACE uses information supplied by the applicant to define the basic and overall project purpose during their CWA review process. The basic project purpose is the fundamental or irreducible reason for the project that is used by the USACE to determine if the proposed action is water dependent. The overall project purpose is a more detailed, comprehensive and project specific version of the basic project purpose. It is similar to the NEPA purpose and need and is used by the USACE when they consider alternatives. The NEPA process includes alternative development and analysis leading to the identification and selection of a preferred alternative. Alternative screening and evaluation techniques should be developed and conducted in a manner that complies with NEPA and provides evidence that the applicant (CDOT) has not inappropriately eliminated the "Least Environmentally Damaging Practicable Alternative" (LEDPA) from further consideration. It is the ultimate responsibility of the Permit applicant to prove to the USACE that the LEDPA has not been screened out during this decision making process.

The NEPA preferred alternative must be considered the LEDPA for the USACE to proceed with authorization under the CWA. The LEDPA, as defined in 40 CFR Part 230.10(a), is the alternative with the least impacts to the aquatic ecosystem, so long as the alternative does not have other significant adverse environmental consequences. "Environmental" in this context is defined as non-aquatic natural resources. The alternatives screening process should, therefore, only eliminate alternatives that may be less damaging to the aquatic ecosystem if they don't meet the Purpose and Need, have other significant consequences to the natural environment, or they are not practicable based on the Section 404(b)(1) guidelines' (Guidelines) definition of practicability (the term practicable is defined in 40 CFR 230.3(q) as that available and capable of being done after taking into consideration cost, existing technology, and logistics in light of overall project purposes.)

Thresholds for initiating the NEPA/404 Merger process

The NEPA/404 merger process shall be required when a project is expected to be processed using an Environmental Impact Statement (EIS) and an IP. A project expected to require an Environmental Assessment (EA) and an IP will enter the merger process only if the FHWA, USACE and CDOT determine it is in the overall best interest of the project. This decision will be made considering potential impacts to waters of the US, the range of potential alternatives, and the potential for controversy on environmental grounds.

Initiating the Merger Process

The merger process shall be initiated when the lead federal agency submits, and the USACE responds affirmatively to, a formal written request for the USACE to be a cooperating agency and that the project be processed using the merger agreement. The decision to request cooperating agency status and initiate the merger process shall be made only after early consultation with the USACE on the subject.

Roles and Responsibilities

USACE: Under this agreement, USACE will participate in meetings and review draft EIS, or EA chapters, as appropriate, such as the project purpose and need to provide input to ensure that the information being presented may also be used for CWA compliance. This may include providing substantive comments on the project Purpose and Need, refinement of practicability criteria for evaluation of alternatives, providing comments relative to whether the Preferred Alternative is the apparent LEDPA, and providing input on proposed compensatory mitigation. The USACE will confirm compliance with the CWA by providing written concurrence that the Purpose and Need statement may be used to define basic and overall project purpose, the Alternatives Selected for Detailed Evaluation comply with the Guidelines, the Preferred Alternative is the LEDPA, and the proposed Compensatory Mitigation adequately offsets impacts to aquatic resources.

FHWA: FHWA is the lead federal agency under NEPA and is required to furnish guidance, participate in the preparation, independently evaluate, and if appropriate, approve and adopt NEPA documents prepared for federally funded highway improvement projects (in Colorado). The Federal Transit Administration (FTA) has a similar role to that of FHWA for projects that use federal transit funds. In the event a project has both highway and transit components, FHWA and FTA may be co-lead agencies under NEPA. Under this agreement, FHWA will actively encourage adherence to NEPA and CWA requirements, assist in the determination to enter the merger process, encourage joint development of purpose and need, review and approve purpose and need, evaluation criteria, alternatives, and the preferred alternative.

CDOT: The highway improvement program in Colorado is programmed, developed and implemented by CDOT. Section 102(D) of NEPA provides the authority to CDOT to prepare NEPA documents with guidance, participation, and independent evaluation by the lead federal agency. CDOT is the permit applicant for CWA Permits. CDOT, in conjunction with FHWA (FTA, as appropriate), will have the primary role for implementing this merger agreement.

Role of Other Reviewing Agencies

The US Environmental Protection Agency (USEPA) and the US Department of Interior Fish and Wildlife Service (USFWS) shall be provided the opportunity to participate as commenting agencies in the NEPA1404 merger process.

The USEPA has responsibility under Section 404 of the Clean Water Act including, but not limited to:

The U.S. Fish and Wildlife Service (USFWS) has responsibility under the Fish and Wildlife Coordination Act, the Endangered Species Act (ESA) and other similar wildlife legislation. The Fish and Wildlife Coordination Act (FWCA) provides the basic authority for USFWS involvement in evaluating impacts to fish and wildlife from proposed water resource development projects. It requires that fish and wildlife resources receive equal consideration to other project features. It also requires that Federal agencies that construct, license or permit water resource development projects must first consult with the USFWS (and the National Marine Fisheries Service in some instances) and State fish and wildlife agency regarding the impacts on fish and wildlife resources and measures to mitigate these impacts. The ESA requires federal agencies enter formal consultation with the USFWS if a proposed federal action may affect a federally listed species. The USACE typically circulates IP applications to the USFWS for their review pursuant to the above statutes. The USFWS also has authority to elevate certain Section 404 decisions (Section 404[q]). Full consideration is to be given to USFWS recommendations.

Commenting agency status requires that these agencies be included in concurrence meetings and that all information provided to USACE will also be provided to the USEPA and USFWS for their review. Official concurrence will not be sought from these agencies. Rather, they will review and provide comments on material provided. Full consideration shall be given to comments provided by these agencies. Any disputes shall be referred to the lead federal agency. Typically, administrative draft NEPA documents are only distributed to cooperating agencies. The documents are considered deliberative and not for public dissemination. Therefore, USEPA and USFWS should be invited and accepted as cooperating agencies prior to being supplied the draft purpose and need or other deliberative material. In the absence of cooperating agency status, some form of agreement must be exercised with the commenting agency to ensure that deliberative material will not be distributed to the public freely or through the Freedom of Information Act. This can be accomplished through a separate MOU or by transmitting deliberative materials under a cover letter that specifically describes that material provided pursuant to this merger agreement is subject to deliberative process privilege and not releasable under the Freedom of Information Act. The letter should indicate that by acceptance of the material that the commenting agency understands and agrees to this privilege.

Merger Framework and Timing

This merger process shall be initiated early in project development and upon written request to the USACE. The timing may coincide with determining the results of project scoping and the decision on class of NEPA document (EIS vs EA). The merger process is a sequential process intended to achieve interagency concurrence on four key issues: 1) Purpose and Need, 2) Alternatives Selected for Detailed Evaluation, 3) the Preferred Alternative, and 4) Compensatory Mitigation.

The concurrence points should be scheduled considering the overall NEPA schedule so that concurrence is sought in advance of milestones or other work efforts to minimize risk that completed work will need to be revisited. Concurrence will generally be sought by providing written material and conducting a NEPA/404 concurrence meeting. Meeting materials will consist of draft purpose and need chapter, evaluation criteria, etc., as described below. After internal FHWA and CDOT review, CDOT will submit draft information to USACE a minimum of 5 business days prior to a scheduled concurrence meeting to provide sufficient review time. The USACE will issue a written concurrence, or provide detailed comments outlining deficiencies that prevent their concurrence within 30 business days following a concurrence meeting. The USACE will direct all written correspondence to the FHWA and any co-lead federal agencies. The applicant shall be sent a duplicate copy.

A written concurrence that the project complies with the guidelines will allow the project to proceed to the next concurrence point without revisiting the decision unless new information is obtained or it is required by law. In the event that comments are provided outlining deficiencies, FHWA and CDOT shall assess the ability to satisfy USACE comments and arrange a second concurrence meeting to present remedial information within 30 days of receipt. The USACE will have 30 days to issue concurrence or provide comments after the second concurrence attempt. Failure to obtain concurrence at this point will trigger the dispute resolution process as described in Appendix D.

Comments received from commenting agencies shall be fully considered and incorporated into the project, as appropriate. FHWA will provide a meaningful written response to the commenting agency, if necessary. The commenting agency will be provided copies of all formal correspondence between signatories.

Tier 1 NEPA documents

The decision regarding whether a Tier 1 NEPA document enters the merger process shall be made at the discretion of the signatories. Consideration shall be given to the level of detail that the Tier 1 document will obtain and use for decision making and whether that level of information will, be adequate for determining CWA compliance. If the decision is made to have the Tier 1 project enter the merger process, "concurrence" that the Preferred Alternative is the LEDPA will be a written statement from USACE that the Preferred Alternative complies with the LEDPA requirements of the Guidelines.

Decisions and "concurrence" issued during the Tier 1 process will not be revisited unless new information is obtained or it is required by law. If a subsequent Tier 2 document meets the threshold for entering the merger process, the process will be reinitiated using the Tier 1 preferred alternative/s only. However, if the merger process is not used in development of a Tier 1 document, all Tier 1 alternatives will be subject to review by USACE to determine the LEDPA.

Purpose and Need

The purpose of this concurrence point is to ensure that the NEPA Purpose and Need includes sufficient detail for alternative screening, for the USACE to determine the overall project purpose, and to present evaluation criteria that will be used to screen alternatives. A draft Purpose and Need, evaluation criteria, and information regarding any preliminary screening are necessary materials for this stage. Concurrence on Purpose and Need is required before it may be used as a factor in alternative screening. Any alternative screening that occurs prior to concurrence shall be based on the definition of practicability or impacts to natural resources.

A draft Purpose and Need chapter will be required for USACE concurrence. It shall provide a detailed description of the need/s for the proposed action. Project needs shall be measurable and quantitative where feasible, recognizing that, in some cases, the needs may require evaluation in a more qualitative manner. Traffic data, traffic projections, population and growth projections, level of service, safety data, roadway deficiencies, etc. are typical needs that shall be included in the draft chapter, as appropriate. The FHWA and any other co-lead agencies shall participate in the development of and be provided the opportunity to review and ensure that the project Purpose and Need complies with their NEPA requirements prior to submission to the USACE for concurrence.

The project needs allow the identification of primary goals or objectives that must be met to justify the expenditure of funds. These primary goals or objectives will form the basis and should clearly relate to alternative evaluation criteria. Examples of primary goals and objectives may be to reduce congestion, increase capacity, eliminate a safety hazard, or provide mode choice. Secondary goals or objectives that add value to the project and support the overall purpose may also be considered during alternative evaluation.

Typical secondary goals and objectives may be to adhere to existing land use plans, or minimize environmental effects. These secondary goals and objectives should be introduced in the alternatives section as important considerations during alternative development and evaluation, but shall not be used for screening against meeting the Purpose and Need.

USACE scoping comments and FHWA guidance on preparing Purpose and Need should be followed and an interim consultation meeting may be conducted to ensure that the draft chapter and evaluation criteria are proceeding consistent with requirements.

The above requirements are intended to ensure that the Purpose and Need chapter will meet the Guidelines' requirements for evaluation of alternatives. If the purpose and need statement changes substantially from the draft version submitted to the USACE for concurrence, a second opportunity for review shall be granted. Modifications to the Purpose and Need shall be submitted to FHWA and USACE for concurrence.

Alternatives to be Evaluated in Detail

Concurrence for alternatives selected for detailed analysis (reasonable range of alternatives under NEPA and practicable under CWA) must be sought as early as possible and prior to detailed analysis in the DEIS. This will ensure that alternatives carried forward have met the agreed upon screening criteria and can be evaluated to determine the LEDPA. The screening criteria for each level of screening should be presented in table format (see Appendix E). The criteria descriptions and rationale/basis for screening for Existing Technology, Logistics, Costs and Environmental Consequences are recommended to closely match those presented in Appendix E. Materials needed for this stage include a description of how evaluation criteria were applied and used to screen alternatives, an accounting of alternatives that have been screened out, and a description of the alternatives to be evaluated in detail. It is recommended that a table or similar format be used that clearly identifies how well an alternative meets the evaluation criteria, including purpose and need, practicability and environmental consequences.

When comparing impacts to the aquatic ecosystem to significant adverse impacts to other natural resources, consideration should be given to mitigation that will minimize effects to those other natural resources (Ex. The Section 7 consultation process requires that an adverse effect to a federally listed species be minimized through the issuance of Reasonable and Prudent Measures intended to minimize take. These measures are required and, by definition, decrease the level of take). Mitigation to other natural resources must be considered, however compensatory mitigation for impacts to waters of the US may not be considered in the evaluation for the LEDPA. This requires a comparison between a mitigated impact to a natural resource and an unmitigated impact to a water of the US.

Impacts to resources that are not defined as "Natural" or "aquatic" may still be used to eliminate an alternative. However, they must be described as either not meeting the purpose and need or by using one of the three practicability factors (Existing Technology, Logistics and Costs). For example, an adverse socioeconomic impact that is not socially feasible (See Appendix E - Social Feasibility) may be eliminated as not practicable. Practitioners would compare each alternative to the project Purpose and Need during screening and, if they meet it, would then fully explain why disadvantages of the alternative in terms of cost, logistics, or lack of available technology cause it to be eliminated from further consideration. For example, if the alternative with the greater socioeconomic impacts causes the lead agency to be unable to meet Executive Order 12898, Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations, it would not be a socially feasible alternative and thus not practicable.

Practitioners should keep in mind that the merger process is intended to ensure that alternatives that have been screened out are not the LEDPA. The public review process and interagency consultation may always identify new alternatives subject to consideration under this NEPA and CWA merger agreement.

Preferred Alternative

The purpose of this agreement is to ensure that information developed for an FHWA/CDOT project may be used by the USACE for their NEPA and CWA requirements. The goal is to reduce duplicative efforts and to ensure that FHWA and CDOT will be fully informed of, and have the opportunity to correct, any deficiencies in meeting the requirements of the CWA. It is the desire of FHWA and CDOT to select a preferred alternative that may also be permitted under the CWA. For this reason, this stage in the process requires the USACE review the preferred alternative for their concurrence that it appears to be the LEDPA.

Concurrence on the preferred alternative shall be sought prior to issuance of the DEIS or FEIS, depending on which document contains the initial selection of the preferred alternative. After concurrence that the preferred alternative is the LEDPA, CDOT will submit a Permit application to USACE, and the public notice issued by USACE will coincide with the release of the DEIS or FEIS for public comment.

A meeting should be scheduled with the USACE to present the results of detailed alternative analysis and to recommend the preferred alternative. The USACE will provide a letter indicating whether or not the preferred appears to be the LEDPA. Formal determination that the preferred alternative is the LEDPA will be made through the issuance of the CWA Section 404 permit for the project. In the case of a tiered document, the USACE will provide a letter indicating whether the preferred alternative/s is in compliance with Guidelines.

Compensatory Mitigation

The CWA Permit application must identify compensatory mitigation for unavoidable impacts to wetlands and other waters of the US. Therefore, compensatory mitigation options should be presented to the USACE for their review and comment prior to submittal of the permit application. Official concurrence for compensatory mitigation will occur upon permit issuance. The USACE will provide comments on whether or not the compensatory mitigation would provide functional replacement for impacts to waters of the US. The compensatory mitigation plan may be "conceptual" at the time that the Section 404 permit application is submitted for review. Conceptual is defined as providing sufficient information so that the USACE can determine the proposed mitigation adequately replaces aquatic resource functions lost or adversely affected by the project (the USACE must be able to determine that the mitigation proposal complies with the Guidelines and the 1990 USACE/USEPA Mitigation MOA). The conceptual mitigation proposal shall include baseline information, goals and objectives, site selection criteria, mitigation work plan, recommended performance standards, site protection plans and contingency plans (See Regulatory Guidance Letter 02-2, Guidance on Compensatory Mitigation Projects for Aquatic Resource Impacts Under the Corps Regulatory Program Pursuant to Section 404 of the Clean Water Act..., dated December 26, 2002). The USACE may require submittal of a more detailed design of the mitigation site prior to the initiation of construction activities.

In most cases, a jurisdictional determination should be obtained prior to completion of the DEIS. Note that often large corridor projects have been permitted to obtain a jurisdictional determination prior to identification of the preferred alternative to avoid unnecessary field work that would be required to make a determination for all alternatives that are being evaluated.

Maintenance of Agreement

This agreement will be revisited by signatory agencies every three calendar years to assess its effectiveness and recommend and implement changes, as necessary, to maintain it as a useful working agreement.

By signing this agreement, I agree to work cooperatively to implement the NEPA/404 merger process described above.

Signed by Tom Norton       Date: 1/6/05
Tom Norton, Executive Director, Colorado Department of Transportation

Signed by Todd Wang       Date: 12/15/04
Lieutenant Colonel Todd Wang, Commander, US Army Corps of Engineers, Albuquerque District

David Nicol       Date: 12/9/04
David Nicol, Division Administrator, Colorado Division, Federal Highway Administration

Appendix A - NEPA/404 Merger Process Outline

Initiating the process:

- Lead Agency request for cooperating agency status and participation in the merger process. Lead agency informs commenting agencies that the merger process will be initiated.

Purpose and Need:

- CDOT Project Team (PT) will present the Draft Purpose and Need, Goals and Objectives, and Evaluation Criteria to the USACE for concurrence.

- CDOT PT will identify any alternatives screened out during preliminary screening based on practicability or significant impacts to the natural environment.

Alternatives to be Evaluated in Detail:

- CDOT PT will present results of alternatives screening (provide documentation that supports screening of alternatives based quantitative objectives where data is available) to USACE for concurrence.

- CDOT PT will identify primary pros/cons of remaining alternatives with respect to aquatic ecosystems and other potentially significant effects

Preferred Alternative:

Prior to the issuance of the FEIS (or DEIS if a preferred alternative has been identified), CDOT PT will provide to USACE, for concurrence, the following:

- Results of detailed analysis and recommendation for the preferred alternative/LEDPA

Compensatory Mitigation:

Prior to the issuance of the FEIS (or DEIS if a preferred alternative has been identified), CDOT PT will provide to USACE, for concurrence, the following:
- Estimated unavoidable impacts of preferred alternative to wetlands and other waters of the US
- Conceptual compensatory mitigation plan*

*Prior to initiation of construction activities, the USACE may require a detailed design of the proposed mitigation site for review and concurrence.

Appendix B - Acronyms

CDOT - Colorado Department of Transportation

CEQ - Council on Environmental Quality

CWA - Clean Water Act

DEIS - Draft Environmental Impact Statement

EA - Environmental Assessment

EIS - Environmental Impact Statement

FEIS - Final Environmental Impact Statement

FHWA - Federal Highway Administration

FTA - Federal Transit Administration

IP - Standard Individual Permit

LEDPA - Least Environmentally Damaging Practicable Alternative

NEPA - National Environmental Policy Act

PT - Project Team

USACE - US Army Corps of Engineers

USEPA - US Environmental Protection Agency

USFWS - US Department of Interior Fish and Wildlife Service

Appendix C - References

Federal NEPA Laws and Regulations

FHWA Laws and Regulations

NEPA Guidance

Clean Water Act Guidance

Appendix D - Dispute Resolution

All agencies agree to work cooperatively to avoid and resolve conflicts. The agencies agree to explore issues thoroughly before seeking to use this dispute resolution mechanism by ensuring that adequate communication has occurred, that all agencies fully understand the issues, and the reasons why an agency is committed to a position.

If disagreements emerge which cannot be resolved, the impasse shall be escalated as follows:


Project Manager

Project Coordinator

Operations Engineer

Field Office Supervisor

Regional Transportation Director

Program Delivery Engineer

Regulatory Branch Chief

Chief Engineer

Assistant Division Administrator

District Engineer

Executive Director

Division Administrator

When the parties at the lowest organizational level of the agencies have agreed to escalate, a meeting date will be established within 14 days. At that time, the agencies from both levels will meet to discuss the issues and come up with a resolution. If an agreement cannot be reached, then the issue will be escalated to the next level and a meeting date established within 30 days. At that time, the agencies from all three levels will meet to discuss the issues and come to a resolution. If an agreement cannot be reached, the issue will be escalated to the highest level and a meeting date established within 30 days. At that time, all agencies will come to resolution.

Mediation and facilitation may be used at any level to help expedite resolution. Documentation of all disagreements and resolutions shall be furnished to all involved agencies and included in the project file.

Appendix E - Sample Screening Criteria Table for Transportation Projects

Screening Category Criterion Description Rationale/Basis for Screening Criterion

Purpose and Need

  PN1 Must improve transportation capacity (for urban rehab: through and within the corridor) To advance, an alternative must provide sufficient additional person-carrying capacity to meet projected demand in 2025 (urban rehab: through and within corridor).

PN2 Must improve transportation mobility (for urban rehab: through and within corridor).

To advance, an alternative must improve projected 2025 peak hour Level of Service to "D" (urban rehab: through and within the corridor)

PN3 Must provide multi-modal transportation opportunities

To advance, an alternative must provide increased peak hour transit mode share, with at least "X" percent non-highway mode.

PN4 Must improve existing design and safety deficiencies

To advance, an alternative must improve existing design and safety deficiencies to current standards. Technology

Existing Technology

ET1 Must use proven technology

To advance, proposed transportation technologies must be tested and proven.

ET2 Must be technically feasible to construct To advance, known features or alternatives that do not meet technical feasibility to construct should not be carried forward.

LI Must conform to federal and state laws

To advance, alternatives must not violate any applicable federal or state laws. One example would be an alternative that, if implemented, would violate applicable air quality standards, thereby violate the Clean Air Act.

L2 Location of transportation improvements To advance, alternatives must be located outside of national parks, wilderness areas, wildlife refuges and Superfund sites.
L3 Social Feasibility To advance, an alternative must be socially feasible. An example of an alternative that might not be socially feasible would be one that would require extensive relocation of numerous families or businesses within one or more neighborhoods.
 Cl Must not be, by inspection or detailed analysis during later screenings, unreasonably expensive To advance, an alternative must not be so unreasonably costly, relative to other alternatives, that it does not warrant further consideration. The determination of what constitutes reasonable expense should consider whether the projected cost is substantially greater than the costs normally associated with the particular type project.
Environmental Consequences
  ECI Must not jeopardize the continued existence of a T&E species nor result in destruction or adverse modification of critical habitat To advance, the impacts of an alternative must not result in a Jeopardy or Adverse Modification Biological Opinion, issued after completion of consultation under Section 7(a) of the Endangered Species Act.
EC2 Must avoid and minimize impacts to the aquatic ecosystem To advance, an alternative must avoid and minimize direct, indirect and cumulative impacts to the aquatic ecosystem. Applicant's selection of the preferred alternative will be based on the practicable alternative, that meets the Purpose and Need, with the least adverse impacts to the aquatic ecosystem.
EC3 Must not result in significant adverse affects to the natural environment To advance, an alternative must not result in other significant adverse affects to the natural environment. Before an alternative can be eliminated using this criterion, the Corps of Engineers must concur with the determination.

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