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Home My WebLink About20201989 Ver 1_WEI Response to IRT Comments_East Mingo Mitigation Plan Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 June 12, 2023 Ms. Kim Isenhour Mitigation Project Manager Wilmington District Regulatory Division US Army Corps of Engineers RE: IRT Review comments for Mitigation Plan Wildlands Cape Fear 06 Umbrella Mitigation Bank East Mingo Mitigation Site Cape Fear River Basin 03030006 USACE ID#: SAW‐2020‐02093 NC DWR # 20201989 Dear Ms. Isenhour, Thank you for compiling and providing comments on the East Mingo Mitigation Site draft Mitigation Plan. We have reviewed the comments dated April 4, 2023 and have revised the Mitigation Plan accordingly. This letter includes a response to each comment; comments have been reprinted with our response in italics. The revised Mitigation Plan is being submitted with this letter. 1. Have adjacent landowner concerns regarding hydrologic trespass on her pasture been resolved? Yes, I have been in contact with the adjacent landowner so that she could better understand the project and know that it does not affect her property. 2. Figure 11: a. Please add a flow gauge to Wolf Creek. With the amount of sediment coming into the system, there’s a concern that maintaining a defined channel may be challenging. A flow gauge was added to Wolf Creek. Tables and Figure 11 were updated accordingly. b. Please add a cross‐section to Beaver Creek restoration area. A cross‐section was added to Beaver Creek. Tables and Figure 11 were updated accordingly. c. Please add a cross‐section to the restoration portion of Deer Creek. A cross‐section was added to Deer Creek. Tables and Figure 11 were updated accordingly d. I’m confused why the erosional channels are shown on this figure. These should be re‐ labeled that they will be filled, or removed from the figure. Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 These features were removed from Figure 11. e. Please add a veg plot to the ponded area adjacent to Wolf Creek. A random vegetation plot will be sampled within the long‐term ponded area near Wolf Creek. This is indicated on Figure 11. Please note that the vast majority of this long‐term ponded area is already forested and the planting zone within is relatively small (see plan sheet 2.5). f. Please capture the areas where the erosional channels are being filled with a random veg plot at least once during monitoring. A random vegetation plot will be sampled in the vicinity of the filled erosional features, if applicable. This is indicated on Figure 11. Disturbance to the existing forested canopy will be minimized when filling these features so there may only be small planted zones in this area. g. Please add a photo point to crossing #2. A photo point was added. h. Please plan for a random veg plot along Beaver Creek at least once during monitoring. We will do this. i. Is there a rain gauge on site? An on‐site rain gauge will be installed. Data from a weather station will be substituted if the gauge malfunctions. The nearest weather station with a history of reliable records is Dunn 5 NW located 8.3 miles away at 35.3243, ‐78.6878. j. Please include photo points at all crossings. Photo points will be taken at both crossings. k. Please update Table 19 with these additions. Table 19 has been updated with these changes. 3. Page 6: Did you discuss thinning any of the loblolly pines along Cow Creek? Is there a concern that these will provide a seed source? Do you plan to use the mowing guidelines during monitoring to prevent pines from overtaking the floodplain? There is no plan to thin the loblolly pines along Cow Creek. In the event that dense pine regeneration is negatively impacting establishment of desirable vegetation, selective brushcutting and/or chemical treatments will be applied on an as‐needed basis. Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 4. Will pasture grasses be treated prior to planting? Yes, non‐native pasture grasses will be chemically and/or mechanically treated prior to planting. 5. Page 13, Section 3.5: After discussions with WRC, we have concerns with proposed ford crossings in a sand‐bed system. Depending on the underlying material, it can be very difficult to maintain a stable crossing. WRC will not object if you feel like the geology and construction design will maintain a stable crossing while allowing the sand bed system to transport bedload naturally while maintaining surface flow. Please provide photo documentation of each crossing annually. Detailed ford crossing designs for East Mingo Creek and Lamb Creek have been added to Sheets 5.9 and 5.10, respectively. The East Mingo Creek crossing uses a series of 4’x10’ cattle slats. These slats have very low roughness to facilitate sediment transport and each slat weighs approximately 2.2 tons. The slats are 6” think and sit on a base of #57 stone. The Lamb Creek crossing is similar in design to the East Mingo Creek crossing. The major difference is Lamb Creek uses hog slats, which are less dense than cattle slats, due to this stream having much less shear stress. Each 4’x8’, 4” thick hog slat weighs approximately 0.6 tons. Photo documentation will be provided of each crossing annually. 6. Section 3.5: Are there encroachment concerns from the housing development west of Rabbit Creek? Additional signage and horse tape may be beneficial to establish a boundary. There are no current concerns, However, areas adjacent to existing mowed land will be posted with extra signage. Wildlands will further assess encroachment risk and add polytape if deemed high risk. 7. Section 3.3.4: It would be helpful for the review if a summary table of existing groundwater gauge data was included. A summary table was added and groundwater gauge plots in Appendix 1 were updated to include additional data collected since draft mitigation plan submittal. 8. Table 6: Are the impacts for crossings included in this table? Table 6 was revised and includes impacts from crossings. 9. It would be helpful to include the WETS table information for normal conditions. A WETS table has been added to Appendix 1. 10. Section 4.2 and Appendix 4: Have you looked up the site on iPaC recently? The regulatory viewer shows the Tricolored bat, RCW and Monarch Butterfly for that area. I was glad to see several pollinator species in the seed mix. Yes, as of April 26, 2023 the Tricolored bat is listed as a proposed endangered species Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 and the Monarch Butterfly is listed as a candidate species for this project area. 11. The DWQ stream ID form for Wolf Creek lists invasive aquatic plants. Which invasive aquatic species are on the site? Marsh dewflower (Murdannia keisak) was observed in Wolf Creek. Marsh dewflower will be chemically managed as needed throughout the life of the project. 12. Is there potential for adaptive management needs on Snake Trib if the pond upstream is fixed and flow from the pond changes? This was an IRT concern during the site visit so it may be helpful to include this discussion in the AMP section. We walked upstream during the design phase of the project and found that the mainstem of the creek actually continues along the western side of the existing pond, well upstream of the pond itself instead of routing through the pond. The pond is an off‐line feature. The outlet of the pond is a shallow ephemeral channel that only engages during storm events. The pond and outlet structure appeared stable during our inspection. A description of this has been added to the existing conditions description of Snake Creek in Section 3.3.1. 13. Appendix 5: It might be beneficial to add discussion on crossing maintenance if any is anticipated. A discussion on crossing maintenance has been added to Appendix 5. 14. Appendix 6: I know this is template language, but please add item #7 for the initial credit release that includes documentation of the establishment of the long‐ term/endowment/escrow account. This has been added to Appendix 6 in Section 1.1 f. 15. Appendix 8: The cost calculation from UP2S may need to be updated. The mitigation plan lists 45.89 acres, but the acceptance letter and spreadsheet from UP2S list 44.75 acres. They may need to update their estimates based on inflation and the mileage costs as well. We contacted UP2Save and they are okay with keeping the cost as is with the slight discrepancy in conservation easement acreage. 16. Please confirm that the BMP at the top of Beaver Creek is not located within a jurisdictional area. I couldn’t locate the BMP on the design sheets to verify it’s location. The depression at the top of UT to Beaver Creek appears to be an old settling pond and is indeed a jurisdictional wetland. We have edited our details on sheet 1.14.1 to show that we are adding stabilization to the outlet of that wetland area to Beaver Creek but not making any changes that would change the hydrologic function of the wetland. It is not being designed to hold back flow during storm events more than it naturally does. The jurisdictional wetland area will continue to filter runoff from surrounding agricultural fields in its present condition. Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 17. Appendix 1: The growing season listed on the gauge data is March 1 to November 16. Table 10 on page 19 lists the growing season as March 17 to November 5. Please update the final mitigation plan with the proposed modified growing season start and end dates and include photo documentation of multiple species bud burst in Appendix 1 to support the proposed March 1st monitoring start date. Section 8.0 Performance standards has been updated to discuss proposed growing season dates of March 1 through November 16. Photos of bud burst and leaf senescence were added to Appendix 1. Table 10 is a summary of reference wetland hydrology from 2006‐2010 which was analyzed many years ago using March 17 through November 5 as the growing season dates. This table is not intended to guide how we currently set growing season dates, but rather to show the range of anticipated wetland conditions found at a reference site. We did not have access to raw data to calculate hydroperiod percentages for this reference site using March 1 through November 16 as growing season dates. We are currently attempting to gain permission to access this site and conduct reference wetland monitoring. 18. Page 28 and Table 18: For the ponded areas, the proposed 160 stems per acre of planted trees is not sufficient. You will need to propose interim performance standards for monitoring years three and five (this applies to the discussion on page 28). You will also need to propose a performance standard that addresses stem density for shrub species. An acceptable performance standard example would be, “Trees will have 160 planted stems per acre at MY07, survival of at least 245 planted stems at MY‐3 and 200 stems per acre at MY‐5. Shrubs will have 160 surviving plants at MY‐3, 130 at MY‐5 and 105 at MY‐7. Herbaceous coverage should be at least 80% at MY‐7. “ Interim and final performance standards for woody stem density are now included in Table 20 Summary of Performance Standards. The long‐term ponded area planting zone includes tree and shrub species which will be intermixed throughout the planting zone; there will not be separate zones for trees and shrubs. We are also concerned that reporting on separate stem density criteria for trees and shrubs could become convoluted. For these reasons we prefer to evaluate success of tree and shrub density as a combined metric as done on previous projects. Interim and final woody stem density performance standards for the long term ponded areas have been increased from the originally proposed quantities. Please note that Table 18 in the draft mitigation plan is now Table 20. 19. Page 30, Section 6.9: Are the ponds west of Cow Creek and Snake Creek stable? Is there a concern of the dams breaching? The ponds have been inspected and appear stable. There is no concern of breaching at this time. 20. Is there a sediment source in the field west of Wolf Creek? There is not a significant sediment source in the field west of Wolf Creek. Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 21. Page 33: The summary credit table lists a 2% benthic credit adjustment. I don’t recall benthic monitoring being discussed in the text except for one line on page 35. I also don’t see monitoring locations on Figure 11. The Guidance states that for those projects where this monitoring is conducted, an additional credit of up to 2% may be generated for each reach being monitored, it would not be based on the entire site unless all tributaries were being monitored. Please clarify and adjust accordingly. After receiving further clarification from USACE, the 2% benthic credit adjustment has been updated to reflect just East Mingo Creek being sampled for a total of 86.076 credit adjustment. Benthic sampling will follow Standard Operating Procedures (NCDWR, 2016) and will not be tied to performance standards or success criteria. The credit adjustment will be released upon completion of benthic sampling. Sampling points can be found on Figure 11. 22. Section 9.0, page 35: The vegetation plots proposed on Figure 11 appear to be adequate to monitor the overall veg success of the site, except for adding a plot adjacent to Wolf Creek. I don’t think it’s necessary to adjust the number of vegetation plots. Noted. 23. Page 37, Table 20: Since the crossings are internal, crossing maintenance should be discussed in this section. A discussion on crossing maintenance has been added to this section. 24. Design Sheets: Grading and limits of disturbance lines were not included. Given the extent of wetland restoration, ditch filling and stream restoration through existing wetlands, it would have been helpful to see preliminary grading information. Preliminary grading contours have been added to the design sheets. 25. Design Sheets – Please confirm that stream reach credits are ending at the confluence streambank and not the confluence centerline. Stream reach credits all end at confluence streambanks, not at confluence centerlines. 26. The narrative discussed the existing wooded areas onsite as having a mature canopy but lacking an understory, as well as the need for privet control. Why was supplemental planting with understory and shrub species not proposed across the site? For my educational purposes, what is the stem survival of understory plantings in your experience? A supplemental planting of understory and shrub species was not proposed for this site based on prior experience of plot failure at the Maney Farm Mitigation Site (See Table 1. Understory Vegetation Plot Data Summary). As discussed in January during the Maney Farm Mitigation Site monitoring close‐out site walk, it is incredibly difficult to mimic natural understory establishment. In natural conditions, species often wait in the seedbank or as a small plant until the perfect lighting conditions arise (dappled Wildlands Engineering, Inc. (P) 919.851.9986 • 312 West Millbrook Road, Suite 225 • Raleigh, NC 27609 light, small canopy gaps, diffuse light, morning light, etc). The conditions are too specific to expect success from a “broad swath” approach to planting. Wildlands believes that under diligent management of Chinese privet, contemporaneous ecological micro‐niches will be made available into which native understory species may recruit and establish. Table 1. Understory Vegetation Plot Data Summary (Maney Farm Mitigation Site) Plot # As‐Built # of Stems MY1 # of Stems MY3 # of Stems MY7 # of Stems 12 16 13 3 1 13 16 15 8 7 14 16 12 3 0 If you have any questions please contact me at aallen@wildlandseng.com, (919)851‐9986 x 106. Sincerely, Angela Allen, P.E., Project Manager