20200775 Ver 1_DWR comments on the Middendorf Springs Draft Mitigation Plan_20230410

DWR comments on the Middendorf Springs Draft Mitigation Plan
April 9, 2023
1. DWR appreciates the review (and extensive comments) from Kelly Phillips of DMS.
2. DWR would like to emphasize the comment on the DMS review of Sheet C-2. DWR has concerns
over the extensive use of Angled Log Sills on some of these streams with the slopes present.
3. Table 4 (and Section 3.3.1): DWR has concerns over the flow (because of the small drainage
areas and slate belt geology) for the following tributaries; 1B, 1C and trib 5.
4. Section 3.3.2.2- Hydric Soils Investigation- DWR was appreciative of the fact there was a Hydric
Soil report by a Licensed Soil Scientist; however, the hydric soils report in Appendix E has several
shortcomings. As was stated in the report, “Due to time constraints, the hydric soil investigation
was not a complete review of the entire area…”. The review lacked covering the entire project
area, lacked geolocating the borings on a map, and should have included many more borings
given the wetlands that were evidently present.
5. Section 7.2.1- Stream Restoration Approach- DWR cautions raising a small drainage area stream
in the slate belt region. DWR believes that there will be continuous flow issues on most of the
streams in this project.
6. Table 12- Shows that the D50 proposed metric is to be 101.6 mm, or about 4 inches. Seeing the
typical for the constructed riffle, of which there will be many on this stream, DWR noted the use
of Class A rip rap in the typical. DWR believes that this will result in a considerable “hardening”
of the stream channel. DWR does not support the extensive use of class A rip rap in these
stream channels.
7. DWR appreciates the design firm utilizing the wetland performance criteria of 12% hydroperiod
during the growing season.
8. Section 9.5- DWR will require three additional gauges be placed in existing wetlands to ensure
that the constructed stream channel does not significantly reduce the wetland hydroperiod. The
specific areas will be mentioned in the review of the Design sheets.
9. Figure 7. It would have helpful if the drainage area acreage would have been listed on the map.
10. Figure 11- Proposed Mitigation Plan-there are several areas of concern on this map. First of all,
DWR urges the designer to capture all areas that connect to the easement that may affect either
the stream or wetlands. Examples of these areas which will likely affect the streams include the
headwaters of tributaries 1C, 1B, and 4. In addition, there are several areas (proposed wetlands
A and B, and existing wetlands, WF, WH, and WA) where the easement line is directly on either
proposed wetlands or existing wetlands. In the past the IRT has encountered problems where
wetlands just outside the easement line were ditched by the landowners and of course these
ditches affected the wetlands within the easement. Also, tributaries 5 and 6 both are shown to
run down valley from where they initially had their confluence with the stream. Figure 14 is
offered for evidence for tributary 5’s path, however, DWR did not note any support for tributary
6’s path.
11. Figure 12- Monitoring Plan- DWR believes there should be flow gauges in the upper third of the
reach on each of the reaches proposed for restoration or enhancement work. Tributary 1B does
not show a flow gauge.
12. Design sheet- C2-there is a lot of slope in this section with a lot of log sills. In the past, log sills
have shown to be prone to leak or lose the ability to hold grade. Careful oversight will be

needed in the construction of so many log sills. Moreover, DWR requires a gauge in the existing
wetland placed stream right approximately near station 4+50.
13. Design sheet- C5 - DWR requires a wetland gauge stream right near station 2+50. This section
shows a lot of constructed riffles. DWR would like to emphasize their concern of placing rip rap
in the stream channel. DWR suggests the designer look for a source of rock on site that more
resembles native rock on site both in type and in size for the stream. In addition, DWR noted
that there does not appear to be any bank treatments for the meander bends. How does the
designer intend to maintain the stability of the stream in these areas (Design sheet C6)?
14. Design sheet C7-same comment as #12 regarding slope and log sills.
15. Design sheet C9- in the longitudinal plot there were no lines.
16. Design sheet C16- DWR requires a gauge stream right at approximately station 4+50
17. Design sheet DT3 – DWR requests the on-site construction supervisor emphasize the specs of
the log sill rollers with the construction company and specifically emphasize placement, footer
logs and the minimum amount of length the log embedded into the bank.
18. Design sheet DT4- DWR requests the designer look for rock on site which will be more suitable
for the stream rather than using NCDOT Class A rip rap.