21. Management of Water Flows: In the July 21, 1999, Federal Register notice, we proposed to modify this general condition to require permittees to maintain, to the maximum extent practicable, preconstruction surface water flow patterns.
Three commenters supported the proposed modification of General Condition 21. Several commenters objected to the proposed modification. One commenter suggested that the text of the proposed modification should be withdrawn and replaced with the original language of "Section 404 Only" Condition 6. A number of commenters stated that the Corps does not have the statutory authority to impose the requirements of this general condition. Two commenters indicated that the proposed modification of General Condition 21 is contrary to 33 CFR 320.4(m). One commenter said that best management practices should be required instead of this general condition. Numerous commenters stated that the requirements of General Condition 21 duplicate existing state or local programs. One commenter expressed concern that this general condition will impose requirements that are contrary to local standards or watershed plans. One commenter said that the requirements of this general condition will make the NWP program useless because all dredge and fill activities affect water flow.
We have statutory authority, through section 404 of the Clean Water Act, to impose General Condition 21 because this general condition is necessary to ensure that activities authorized by NWPs result in minimal adverse effects on the aquatic environment. Flooding and erosion that results from changes in surface water flows can have more than minimal adverse effects on the aquatic environment. The requirements of this general condition are not contrary to 33 CFR 320.4(m) because that section of the Corps regulations, which addresses the allocation of water supplies, is unrelated to the intent of General Condition 21.
District engineers can refer to best management practices to assist permittees in complying with this general condition, but we do not agree that best management practices are more efficient methods of achieving the objectives of General Condition 21. Although the requirements of this general condition may duplicate existing state or local programs, it is important to note that not all state and local governments address the management of water flows. Therefore, we believe that it is necessary to impose, on a nationwide basis, the requirements of General Condition 21 on activities authorized by NWPs. If the state or local government adequately addresses the management of surface water flows, the district engineer will defer to those agencies. However, if the state or local government does not adequately address the management of water flows, district engineers will determine if the proposed work complies with General Condition 21 and may impose special conditions on the NWP to ensure that the authorized work results in minimal adverse effects on surface water flows. If the activity is part of a larger system designed to manage water flows, then activity-specific management of water flows is not required. It is unlikely that this general condition will result in requirements that are contrary to watershed plans, because the intent of General Condition 21 is to ensure that activities authorized by NWPs result only in minimal adverse effects on the aquatic environment.
Although most discharges of dredged or fill material into waters of the United States authorized by NWPs alter surface water flow patterns, these changes are usually minimal or could be mitigated to the minimal adverse effect level and would comply with General Condition 21. If more than minimal changes to surface water flows will occur as a result of the proposed work, the activity should be reviewed through the individual permit process or the activity should be modified with mitigation to comply with General Condition 21.
Two commenters objected to the proposed modification, stating it is too subjective. These commenters said that a lack of specific criteria will cause inconsistent and arbitrary implementation. These commenters requested specific criteria that will allow consistent determination of compliance. One commenter stated that the general condition should specify a storm event magnitude that will be used to determine compliance, because requiring no change in water flows for a 2-year storm event is different that requiring no change in water flows for a 100-year storm event. A commenter requested clarification whether the general condition addresses stream flow, overland flow, and/or stormwater flow. One commenter objected to the proposed modification of this general condition because it requires only qualitative analysis. Two commenters opposed the proposed modification of General Condition 21 because the Corps has not explained how compliance will be determined, specifically how pre-construction and post-construction water flows will be determined. One commenter recommended that the Corps adopt the guidelines at 23 CFR Part 650 (i.e., the Federal Highway Administration's regulations concerning bridges, structures, and hydraulics) to address floodplain encroachments and provide consistency for permit applicants.
We do not agree that specific criteria should be provided nationally, because of the large variability in hydrologic regimes and site conditions across the country. District engineers are better suited to establish local qualitative criteria to determine compliance with this general condition. As discussed in the July 21, 1999, Federal Register notice, this general condition applies to general surface water flow patterns over the course of a year, not to any particular storm event. The types of water flows subject to this general condition include both stream flows and overland flow. For example, this general condition prohibits the use of NWPs to authorize activities that will redirect substantial amounts of surface water to adjoining property owners and more than minimally increase the magnitude of flooding on their property.
To determine compliance with this general condition, district engineers will rely on their judgement and knowledge of local water flow patterns. District engineers will not require detailed hydrologic analyses or engineering studies.
Two commenters stated that requiring permittees to maintain, to the maximum extent practicable, surface water flows from the site is an impossible standard to meet, since such a requirement allows no change from pre-construction water flow conditions. Two commenters said that the phrase "to the maximum extent practicable" is an arbitrary threshold and will result in disputes between the Corps and project proponents with no mechanism for resolution.
The phrase "to the maximum extent practicable" provides flexibility for permittees to comply with the requirements of General Condition 21. This general condition does not establish a "no effect" requirement for compliance. It does not prohibit changes to surface water flows. General Condition 21 merely requires that the activity cause only minimal changes to surface water flows and maintain those flows so that they are similar, not necessarily identical, to preconstruction flow conditions. If changes to surface water flows will be more than minimal, the district engineer will either mitigate those impacts, or if that is not practicable, assert discretionary authority and require an individual permit.
Several commenters said that the analysis required to determine compliance with General Condition 21 is costly and burdensome on project proponents and is inappropriate for NWP activities. One commenter recommended that the text of this general condition include a statement requiring district engineers to defer to state and local agencies that have adequate requirements to manage water flows. A commenter suggested that General Condition 21 should be modified to provide greater flexibility for flood control and stormwater management activities, because this would allow permittees to demonstrate that changes in water flows comply with state or local flood control standards or benefit local hydrology or flow regimes. Another commenter recommended that activities authorized by NWPs should also be designed to allow the movement of aquatic organisms or require mitigation to maintain those movements.
Since district engineers will not require detailed hydrologic or engineering analyses, and must utilize qualitative analyses to determine whether or not a particular activity complies with this general condition, there will not be additional economic burdens on prospective permittees. Although district engineers should defer to state and local agencies if those agencies already impose adequate requirements for maintaining surface water flows, we do not agree that it is necessary to make this statement in the text of General Condition 21. We believe that the text of General Condition 21 provides adequate flexibility for flood control and stormwater management activities because it requires maintenance of surface water flows to the maximum extent practicable. In addition, this general condition does not prohibit the construction of facilities that impound water, such as retention or detention ponds, if the primary purpose of the project is to impound water. General Condition 4, Aquatic Life Movements, already addresses the issues raised by the last comment in the previous paragraph.
In the text of General Condition 21, we have changed the word "project" to "activity" to be consistent with the other general conditions, which refer to activities. This general condition is adopted with the modification discussed above.
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