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Home My WebLink About20080868 Ver 2_Mitigation Report Review_20080815w a rF9p? Michael F. Easley, Governor William G. Ross Jr., Secretary North Carolina Department of Environment and Natural Resources Coleen H. Sullins. Director Division of Water Quality August 15, 2008 David M. Lekson, PWS U.S. Army Corps of Engineers Washington Regulatory Field Office P.O. Box 1000 Washington, NC 27889-1000 Re: PCS Phosphate - Proposed Mitigation Sites DWQ Comments on Restoration Plans Rutman Creek Watershed - Hyde County Upper Back Creek - Beaufort County NCDWQ# 08-0868 Dear. Mr. Lekson: We have reviewed the Restoration Plans for the above-referenced proposed mitigation sites. Our comments are as follows: Upper Back Creek Site Wetland Restoration Hydrology: Extrapolation of well data collected from existing onsite wetlands suggests that hydroperiods are likely two times to several times the length of the proposed 6% (non-riparian) and 10% (riparian) success criteria. Based on these data, water table observations at the July 29, 2008 site visit, and scientific understanding of the targeted wetland types, DWQ believes the proposed criteria are too low to adequately demonstrate that the proposed wetland restoration has been successfully achieved. When the final mitigation plan is submitted for approval, these data (and the hydrology discussion presented for the Rutman Creek Site below) should be reflected in the plan for evaluating project success. Vegetation: Planting plans include appropriate species and densities. Success evaluation should take into account both density (the proposed criteria for stem counts are acceptable) and diversity of the targeted ecosystem types. Project monitoring will occur for five years or until deemed successful by the Corps of Engineers and DWQ, whichever is longer. 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 N `h Carolina Noatura!!ry An Equal Opportunity/Affirmative Action Employer - 50% Recycled/10% Post Consumer Paper Mr. Lekson USACE Washington Regulatory Field Office PCS Phosphate - Proposed Upper Back Creek and Rutman Creek Mitigation Page 2 of 4 Sites Stream and Riparian Buffer Restoration Y. DWQ wishes to reiterate our concerns regarding the amount of zero-order headwater being proposed for both stream credit and riparian buffer credit (Pending Variance). Few of these systems have been constr stream restoration n of ucted to date, rm submitted to DWQ for review. and no performance data a Major a have been Documentation of flow in these systems will be critical in assessin valley systems, and subsequent generation of compensatory mitigation credit. to determine where within the length of these valley that g the success of these headwater It will be extremely both the length of the stream (and amount of associated treamscredi flow begins, as this will determine available for mitigation credit. t) and the acreage of riparian buffer That said, the stream restoration plans for this project appea adequate, proposed success criteria for the headwater valleys. The only issue we noted in with the indicated in the report an ephemeral feature (Table 2.3, Page 7)u. It is an d unclear DWQ how concurs stream generated through restoration of an ephemeral feature. Even assuming Is that the North Prong is credit can Variance to allow for flexible buffer mitigation, buffer credit will not be the issuance of the Major ephemeral streams. be awarded for buffers on Rutman Creek Site Wetland Restoration Soils and Landscape: The locations of targeted restoration Communtt soils and elevation data: the restoration of Wet Hardwood Forest is located on along the western edge of the project, and the riparian zone a es are generally supported by 2' to 4' contours upstream from Alligator Canal. ccompanies the v 1 eYerestorat Yonges n along the [vegetation: Planting plans include appropriate species, but note that fin dependent upon nursery availability. If, at the planting time for each al seedlin substantially from the proposed planting compositions in Tables 2 g quantities will be notified. Please note that poCarpinus sed niana is mentioned as a phase, component of the riparian availability differs plan, but is not included in Table 2. Success ev and 3, then the I ri should hould planting a into proposed criteria for stem counts are acceptable, exctept foroar atake ekin account both density the addressed below) and diversity of the targeted ecosystem types. g riparian buffer credit,, as Hydrology; As discussed at the site visit on July 29, 2008, in the abse DWQ supports the development of hydrologic success nce of substantial reference data criteria based on community descriptions in 401 Oversight/Express Review Permitting Unit 1650 Mail Service Center, Raleigh, North Carol-1650 2321 Crabtree Boule ma 27699 vard, Suite 250, Raleigh, North Carolina 27604 Phone (919) 733-1786 / Fax (919) 733-6893 Internet: httP://h2o.enr state nc us/ncwetiands Nose Carolina ?vWA(rally ?n Equal Opportunity/Affirmative Action Employer- 50% Recycled/10% Post Consumer Paper Mr. Lekson USAGE Washington Regulatory Field Office PCS Phosphate - Proposed Upper Back'Creek and Rutman Creek Mitigation Sites Page 3 of 4 Schafale and Weakley (1990, as referenced in the restoration plan) in combination with Table 5 in the 1987 Corps of Engineers Wetlands Delineation Manual. While Schafale and Weakley note that Coastal Plain Small Stream Swamps are intermittently, temporarily, or seasonally flooded, the surrounding elevation points and proximity to swamp forest at the Rutman site suggest that the project Small Stream Swamps will be wetter than similar systems that grade into upland areas. Further descriptions from Schafale and Weakley include that Nonriverine Wet Hardwood Forests are seasonally saturated or flooded by high water tables, poor drainage, and perhaps by sheet flow from adjacent pocosins; Bay Forests are seasonally saturated or flooded; and Nonriverine Swamp Forests are wet, very poorly drained sites that are seasonally or frequently saturated or shallowly flooded by high water table. Success criteria should be adjusted to reflect these expectations and adequately evaluate whether or not the project is developing into a high quality example of the targeted wetland association. If modeling shows that different hydrologic regimes are predicted for different landscape positions, then it is appropriate to include different success criteria to reflect those predictions. However, LIDAR data for this site show relatively little topographic change, so multiple criteria may not be necessary. Stream and Riparian Buffer Restoration The stream restoration plans for this project appear adequate (noting the overall concerns listed above), and DWQ concurs with the proposed success criteria for the headwater valleys, with the note that the primary success criteria should be actual observations of flow or evidence that flow occurred. The report describes several acceptable qualitative methods for documenting flow. The report also proposes collection of quantitative data via groundwater monitoring wells (page 27), and the use of extrapolation of well data and rainfall data to indicate flow. Groundwater wells can measure the water level elevations, and can document saturation or inundation of the area in the vicinity of the well. However, inundation does not indicate horizontal downslope movement of water, and the described quantitative data will not be acceptable as the sole indicator of a flow event. One additional issue is the proposed vegetative success criteria for the zero-order valleys. On page 24 the report states that the overall success criteria for the project will be 260 trees per acre. For areas being used to generate riparian buffer credit, the vegetative success criteria must be 320 trees per acre after five years (15A NCAC02B. 0260(9)(d)(ii)). Please feel free to contact Tammy Hill or Eric Kulz at (919) 733-1786 if you have any questions regarding this project. None Carolina NawrRlly 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: httD://h2o.enr.state.nc.us/ncwetlands An Equal Opportunity/Affirmative Action Employer- 50% Recycled/10% Post Consumer Paper Mr. Lekson USACE Washington Regulatory Field Office PCS Phosphate - Proposed Upper Back Creek and Rutman Creek Mitigation Sites Page 4 of 4 Sincerely, or- 4 13, +?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 Tom Walker - USACE Asheville Regulatory Field Office 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 None Carolina Ntura!!y An Equal Opportunity/Affirmative Action Employer- 50% Recycled/10% Post Consumer Paper