43. Stormwater Management Facilities: In the July 21, 1999, Federal Register notice, we proposed to issue an NWP to authorize discharges of dredged or fill material into non-tidal waters of the United States, excluding non-tidal wetlands adjacent to tidal waters, for the construction and maintenance of stormwater management (SWM) facilities.
Several commenters supported the issuance of this NWP and one commenter agreed that the construction of SWM facilities in wetlands is often necessary and that these SWM facilities are often more effective than SWM facilities constructed in uplands. Several commenters objected to the issuance of an NWP that authorizes the construction of SWM facilities in wetlands and other commenters opposed the issuance of a separate NWP for SWM facilities. One commenter said that this NWP should authorize discharges of dredged or fill material into non-tidal wetlands adjacent to tidal waters.
We maintain the position discussed in the July 21, 1999, Federal Register notice that the construction of SWM facilities in waters of the United States is often necessary and may provide more protection to the aquatic environment. SWM facilities located in waters of the United States are often more effective than SWM facilities constructed in uplands, because storm runoff flows to streams and wetlands, making these areas more effective at trapping sediments and pollutants than upland areas. The local aquatic environment benefits from more efficient SWM facilities. Low value wetlands and low value ephemeral and intermittent streams may be the best places to locate SWM facilities, to reduce adverse effects to higher value waters by attenuating storm flows and preventing pollutants from further degrading those areas. Division engineers can regionally condition this NWP to prohibit its use in high value waters. For those activities that require notification, district engineers can add case-specific conditions to ensure that the adverse effects on the aquatic environment are minimal or exercise discretionary authority and require an individual permit for activities with more than minimal adverse effects. We do not agree that the scope of applicable waters for this NWP should be expanded to non-tidal wetlands adjacent to tidal waters, because this restriction is necessary to ensure that NWP 43 authorizes activities with minimal adverse effects on the aquatic environment.
Two commenters asked whether NWP 43 authorizes the construction of dams and detention basins to build new SWM facilities. Several commenters said that this NWP does not clearly identify the extent of the Corps regulatory jurisdiction concerning stormwater retention and detention facilities. One of these commenters stated that SWM facilities constructed in uplands that contain wetland vegetation should not be considered jurisdictional wetlands. One commenter said that 40 CFR 131.10 prohibits states from designating waste transport or waste assimilation uses for any water of the United States. This commenter indicated that NWP 43 is contrary to this regulation because it authorizes the construction of SWM facilities in waters of the United States.
This NWP authorizes the construction of dams and detention basins for SWM facilities. However, this NWP does not authorize discharges of dredged or fill material into perennial streams for the construction of new SWM facilities. SWM facilities that were constructed in uplands and have not been abandoned are generally not considered waters of the United States, but district engineers reserve the right to determine on a case-by-case basis whether these areas are waters of the United States (see 51 FR 41217). The provisions of 40 CFR 131.10 do not prohibit discharges of dredged or fill material into waters of the United States for the construction or maintenance of SWM facilities. Stormwater is not categorized as waste.
One commenter supported the proposed 2 acre limit and several commenters recommended increasing the acreage limit to 3 acres for SWM facilities constructed by local governments or local flood control agencies. One commenter said that the 2 acre limit is too low but another commenter indicated that this acreage limit is too high. One commenter suggested a 1 acre limit for NWP 43 and another commenter recommended a 1/4 acre limit. One commenter said that this NWP should have a 100 linear foot limit for stream bed impacts.
We have reduce the acreage limit for this NWP to 1/2 acre, to ensure that NWP 43 authorizes activities with minimal adverse effects on the aquatic environment. In addition, we have added a 300 linear foot limit for filling or excavating perennial or intermittent stream beds.
One commenter supported paragraph (b) of the proposed NWP (now designated as paragraph (c)), which states that NWP 43 does not authorize discharges of dredged or fill material into perennial streams for the construction of new SWM facilities. One commenter said that this NWP should not authorize discharges of dredged or fill material into any stream with perennial stream segments, because some arid regions of the country have perennial streams that occasionally become dry along certain reaches. Two commenters stated that this NWP should not authorize any discharges of dredged or fill material into streams to construct SWM facilities. One of these commenters expressed concern that the NWP would authorize activities with more than minimal cumulative adverse effects in urban areas and said that the conversion of streams to SWM ponds results in the creation of pollution sinks for urban storm runoff. One commenter said that this NWP should contain a condition that requires the maintenance of stream base flows.
We have retained this paragraph in NWP 43. In arid regions of the country, division engineers can regionally condition this NWP to prohibit or restrict its use in streams with intermittent or ephemeral stream segments, if those streams are high value waters. We do not agree that the prohibition in paragraph (c) should be extended to intermittent or ephemeral streams because we believe that, under the terms and conditions of this NWP, the construction of SWM facilities in these waters will result in minimal adverse effects on the aquatic environment. District engineers will monitor the use of this NWP to ensure that it does not authorize activities with more than minimal adverse effects on the aquatic environment, individually and cumulatively. Compliance with General Condition 21 will ensure that surface water flows will be maintained to the maximum extent practicable.
Two commenters objected to the proposed NWP because it does not contain limits for ephemeral stream impacts. These commenters suggested that this NWP should contain language stating that notification to the district engineer is not required for the construction or maintenance of SWM facilities constructed in ephemeral streams. These commenters also recommended that the text of this NWP explicitly state that SWM facilities that were originally constructed in ephemeral streams that have become perennial or intermittent streams are exempt from any permit requirements.
The 1/2 acre limit for this NWP adequately limits impacts to ephemeral streams. Division engineers can regionally condition this NWP to impose limits on discharges of dredged or fill material resulting in the loss of ephemeral stream bed, if there are specific concerns for the aquatic environment in those regions. Any discharges of dredged or fill material into waters of the United States associated with SWM facilities constructed in ephemeral streams that are considered waters of the United States requires a Corps permit.
Two commenters said that the 1/4 acre PCN threshold is too small and two other commenters suggested a 1/3 acre PCN threshold. One commenter stated that the PCN threshold should be lower.
We have lowered the PCN threshold for this NWP to 1/10 acre, to ensure that district engineers have the opportunity to review all activities that have the potential to result in more than minimal adverse effects on the aquatic environment. We have removed the PCN threshold for activities causing the loss of greater than 500 linear feet of intermittent stream bed, since we have added a 300 linear foot limit for stream bed impacts.
One commenter asked if the PCN threshold applies to wetlands that were created as a result of the impoundment of stormwater. This commenter expressed concern that permittees would be required to mitigate for impacts to wetlands created by the construction of an SWM facility. This commenter said that these wetlands are often removed during routine maintenance activities and that requiring compensatory mitigation for the losses of these created wetlands would adversely affect the ability of permittees to effectively restore SWM facilities to their original design capacities.
Notification to the district engineer is required for discharges of dredged or fill material that result in the loss of greater than 1/10 acre of waters of the United States. District engineers will determine the appropriate amount of compensatory mitigation necessary to offset losses of waters of the United States to ensure that the adverse effects on the aquatic environment are minimal. Subparagraph (d)(3) clearly states that compensatory mitigation is not required for maintenance activities in designated maintenance areas of existing SWM facilities.
One commenter recommended the removal of subparagraph (c)(1) of the proposed NWP (now designated as subparagraph (d)(1)) because the maintenance of SWM facilities occurs on an unpredictable, episodic basis which is not conducive to a maintenance plan. Another commenter said that a compensatory mitigation proposal should not be required for all activities that require notification because the construction of some SWM facilities may result in the establishment of diverse, mature wetlands in areas that are not disturbed for extended amounts of time. This commenter suggested that the district engineer should have the ability to determine whether or not compensatory mitigation should be required for maintenance activities authorized by this NWP.
Subparagraph (d)(1) does not require maintenance on a timed schedule. The maintenance plan can include a statement that maintenance activities will be conducted as needed, to ensure that the SWM facility continues to function effectively. The maintenance plan should also identify the designated maintenance areas of the SWM facility. Subparagraph (d)(3) requires only the submission of a compensatory mitigation proposal with the PCN. Based on the review of a PCN, a district engineer can determine that compensatory mitigation is unnecessary because the adverse effects on the aquatic environment are minimal without compensatory mitigation or that they will be mitigated as wetlands are established in the SWM facility.
Two commenters said that the reference to "watershed protection techniques" should be deleted from paragraph (e) of the proposed NWP (now designated as paragraph (f)) or the term should be defined for the purposes of NWP 43. One commenter stated that the maintenance of existing SWM facilities should be exempted from the requirements of this paragraph. One commenter said that it is inappropriate for the Corps to characterize bioengineering methods as best management practices. This commenter indicated that bioengineering methods should be considered as mitigation and that the permittee should be given compensatory mitigation credits for utilizing bioengineering methods. One commenter indicated that there is a contradiction in the July 21, 1999, Federal Register notice because this notice states the district engineer can allow the establishment of mitigation credits in SWM facilities constructed with bioengineering techniques, but mitigation credits cannot be established in regularly maintained areas in SWM facilities. This commenter said that that mitigation credits should be limited to non-maintenance areas and that mitigation credits should not be allowed for the establishment of aquatic benches.
We have retained the phrase "watershed protection techniques" in paragraph (f) because these techniques are an important mechanism to ensure that NWP 43 authorizes activities with minimal adverse effects on the aquatic environment. We will not define this term because appropriate watershed protection techniques may vary in different areas of the country. For example, in many arid regions of the country it may be impractical to establish and maintain vegetated buffers next to streams. In general, the requirements of paragraph (f) apply to the construction of new SWM facilities, but best management practices should be used when conducting maintenance activities. Bioengineering techniques can be used to mitigate adverse effects on surface water quality. These techniques should be considered as best management practices in accordance with the definition in the "Definitions" section of the NWPs. District engineers can grant compensatory mitigation credits for bioengineering methods if those methods result in net gains in aquatic resource functions and values and are not located in areas within SWM facilities that require regular maintenance. Aquatic benches can provide compensatory mitigation, if those areas are not in designated maintenance areas of SWM facilities.
One commenter said the NWP 43 will authorize the construction of more than one stormwater management facility in a single watershed. This commenter stated that paragraph (e) of the proposed NWP (now designated as paragraph (f)) should contain a provision that requires the consideration of other SWM facilities located in the same watershed.
NWP 43 can be used to authorize more than one SWM facility in a particular watershed, provided each of those SWM facilities constitutes a separate single and complete project with independent utility. District engineers will monitor the use of this NWP to ensure that it does not authorize activities with more than minimal adverse effects on the aquatic environment, individually or cumulatively.
Several commenters said that maintenance of SWM facilities should be considered exempt from Corps permit requirements. One commenter stated that the requirements of paragraph (f) of the proposed NWP (now designated as paragraph (g)) are unnecessary because this activity can be authorized by NWP 3.
The maintenance of SWM facilities constructed in Section 404 waters is not exempt from Corps permit requirements. However, most maintenance does not require a Corps permit because the activity only involves incidental fallback of dredged material. NWP 43 authorizes the maintenance of existing SWM facilities that involves discharges of dredged or fill material into waters of the United States. NWP 43 does not authorize maintenance activities in Section 10 waters.
One commenter expressed concern about the provision in paragraph (g) of the proposed NWP (now designated as paragraph (h)). This commenter said that a developer could fill up to 3 acres of waters of the United States under NWP 39 and the local government could build an SWM facility for the development under NWP 43, which would exceed the total acreage for a single and complete project.
We believe that most SWM facilities constructed for a particular development will be built by the developer, not the local government. The developer may turn over the SWM facility to the local government for maintenance, but the construction of the SWM facility will be reviewed with the construction of the development. If NWP 39s and 43 are combined to authorize a single and complete project, the activity is subject to General Condition 15. There may be instances where a local government will construct a regional SWM facility that serves more than one development. These regional SWM facilities are considered to have independent utility from the serviced developments and may be authorized by NWP 43.
In response to a PCN, district engineers can require special conditions on a case-by-case basis to ensure that the adverse effects on the aquatic environment are minimal or exercise discretionary authority to require an individual permit for the work. The issuance of this NWP, as with any NWP, provides for the use of discretionary authority when valuable or unique aquatic areas may be affected by these activities. This NWP is subject to General Condition 25, which restricts its use in designated critical resource waters. For NWP 43 activities resulting in discharges of dredged or fill material into waters of the United States within 100-year floodplains, General Condition 26 requires the permittee to notify the district engineer and demonstrate that the proposed work complies with FEMA or FEMA-approved local floodplain construction requirements. NWP 43 is issued with the modifications discussed above.
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