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Home My WebLink About20070747 Ver 1_Mitigation Bank Proposal Review_20080729Q?QF WA TF9OG co July 29, 2008 David M. Lekson, PWS U.S. Army Corps of Engineers Washington Regulatory Field Office P.O. Box 1000 Washington, NC 27889-1000 Re: Proposed Flat Swamp Mitigation Bank Site Craven County, North Carolina NCDWQ# 07-0747 Dear. Mr. Lekson: Michael F. Easley, Governor William G. Ross Jr., Secretary North Carolina Department of Environment and Natural Resources Coleen Sullins. Director Division of Water Quality We have reviewed the Draft Phase II- Preliminary Mitigation Plan dated June 2008 (the Plan) prepared for the above-referenced project. DWQ has also received a draft MBI and plans (dated July 2008) to establish a riparian buffer and nutrient offset bank at the site. Additionally, Eric Kulz and Periann Russell with DWQ visited the site on July 23, 2008. Our comments are as follows: Stream Restoration Review of the USDA soil maps, USGS topographic map and LIDAR images of the property did not give any indication of the former presence of streams on the site. Based on the aerial photographs presented in the Plan, the former presence of all of the stream threads shown on Figures 7 and 8a through 8d appears inconclusive. However, it is possible that this site did formerly support zero-order stream valleys/swamp runs, as described in the draft guidance document entitled Information Regarding Stream Restoration with Emphasis on the Coastal Plain (2007). In addition, due to the significant hydrologic manipulation of the site and surrounding areas, the proposed stream valley restoration project outlined in Figure 11 may actually include some stream creation, as proposed swales and valleys are not shown in the same locations and alignments as the original streams depicted in Figures 7 and 8a through 8d. That said, DWQ does not necessarily disagree with the proposed concept of zero-order valley restoration (creation) on this site for mitigation credit. DWQ is concerned that based on the fall across the site (one foot of fall from the northwest corner to the main outfall, as per Scott Frederick), and the potentially small sizes of the subwatersheds of each of the proposed valleys shown on Figure 11, that some of the stream features may not exhibit flow and may not be considered to be streams. 401 Oversight/Express Review Permitting Unit 1650 Mail Service Center, Raleigh, North Carolina 27699-1650 2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604 Phone (919) 733-1786 / Fax (919) 733-6893 Internet: http://h2o.enr.state.nc.us/ncwetlands One Np ?r hhCarolina Naturally An Equal Opportunity/Affirmative Action Employer-50% Recycled/10% Post Consumer Paper Mr. Lekson USACE Washing Regulatory Field Office Proposed Flat Swamp Mitigation Bank Site Page 2 of 3 Data on the size of each proposed subwatershed should be provided to the MBRT to assess using the above-referenced data as guidance. Of utmost importance in this project is that the streams restored/created need to exhibit flow. Some form of flow documentation, whether it is photodocumentation of actual flow, or of wrack lines or drainage patterns forming, or using sand plots, must be included in the success criteria. These issues were discussed with Scott Frederick on-site, and the possibility of reducing the number of proposed valleys was discussed. According to the Plan and Scott Frederick during on-site discussions, surface flow to the proposed stream valley restorations will be supplied by ditches carrying flow from upgradient areas offsite. It is unclear how the water in these ditches, some of which are fairly large and deep, will be brought up to the new streambed elevation to flow into the shallow swales or valleys which will constitute the zero-order streams to be restored. Wetland Restoration and Other Issues The desire for the Sponsor to generate nutrient offset credit has the potential to affect the wetland portion of the bank, which has already been approved. Figure 11 a in the proposed buffer MBI (a modification of Figure 11 in the stream plan) shows areas shaded in gray where potential buffer credit for nutrient offset can be generated. Some of this credit is proposed to be generated along the restored/created stream runs. Other credit is proposed by leaving sections of ditches downstream from the green ditch plugs in place (ditches can be buffered for nutrient offset credit, unlike riparian buffer credit). What this proposal will amount to is open (but buffered) field ditches extending from the ditch plugs and through the riparian zone of the restored/created streams, discharging to these stream features. We are not comfortable with the idea of providing stream credit for a stream that has ditches (even buffered) entering every 100 feet along the stream run, as this does not constitute restoration of a "natural" or reference riparian system. DWQ also questions the effect of these remnant ditches on the proposed wetland restoration areas on- site. This proposal also potentially reduces the amount of wetland credit available, as described in the MBI for the wetland portion of the site. According to Scott Frederick, the ledger presented in Appendix B of the stream restoration plan is not really correct, as the green unshaded (wetland) areas on Figure 11 a do not total 323 acres, as the ledger indicates. A revised ledger has been provided to me for my files, but DWQ indicated to Scott that this would require approval of the MBRT and a modification of the wetland MBL 401 Oversight/Express Review Permitting Unit 1650 Mail Service Center, Raleigh, North Carolina 27699-1650 2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604 Phone (919) 733-1786 / Fax (919) 733-6893 Internet: http://h2o.enr.state.nc.us/ncwetlands Noa` Carolina tura!!y An Equal Opportunity/Affirmative Action Employer - 50% Recycled110% Post Consumer Paper Mr. Lekson USACE Washing Regulatory Field Office Proposed Flat Swamp Mitigation Bank Site Page 3 of 3 DWQ strongly feels that a meeting of the MBRT, the Sponsor, and the consultants for the project be held to determine the scope of work proposed for the project, a discussion of the types of stream and wetland systems expected to be restored, and the expected mitigation credits to be generated. Plans submitted in the original wetland restoration plan (for which an MBI was executed), the stream restoration plan, and the draft buffer restoration plan/draft state MBI all appear to show differing plans and credits for the project. Some of the work proposed to create buffers for nutrient offset credit may be detrimental to the establishment of a functioning headwater stream and wetland system. Please feel free to contact Eric Kulz at (919) 733-1786 if you have any questions regarding this project. Sincerely, C 4 1;4 Cyndi B. Karoly, Program Manager 401 Oversight and Express Review Program cc: File Copy (Eric Kulz) Central Files Kyle Barnes - DWQ Washington Regional Office NeehCarolina ataM4 401 Oversight/Express Review Permitting Unit 1650 Mail Service Center, Raleigh, North Carolina 27699-1650 2321 Crabtree Boulevard, Suite 250, Raleigh, North Carolina 27604 Phone (919) 733-1786 / Fax (919) 733-6893 Internet; hftp://h2o.enr.state.nc.us/ncwetiands An Equal Opportunity/Affirmative Action Employer - 50% Recycled/10% Post Consumer Paper