20130595 Ver 1_Credit Modification Request_20151019

Upper Silver Creek Wetland WMU Credit Modification Request
Michael Baker Engineering respectfully requests to revise the wetland WMU credit type breakdown for
the Upper Silver Creek Restoration project and reclassify approximately 0.78 WMUs of currently defined
Riparian Wetlands to Non-Riparian Wetlands in order to fulfill the contracted value and help DMS meet
their programmatic needs.
In the initial site evaluations these wetlands had been determined to be non-riparian by Baker scientists
and were proposed as such in the first drafts of the mitigation plan. However, based on comments
made in the final round of reviews by two members of the IRT, these wetlands were changed to riparian
in the final version of the plan. It appears that there was concern regarding the location of these
wetlands, specifically that they were located within the geomorphic floodplain. The comments cited the
USGS Topographic map as evidence of this assumption. However, using more detailed mapping data it
seems apparent that in fact the wetlands are located outside of the floodplain after all. Figure 1 shows
both the FEMA FIRM 100-year floodplain for the project and the Baker-revised LOMR showing the slight
changes to that FEMA floodplain resulting from the stream restoration project construction. The
wetlands proposed for reclassification are located outside both those floodplain boundaries, and are
approximately 200 feet from the restored stream channel, and 4 feet higher in elevation. Figure 2
shows the original FEMA FIRM map for the project site (Panel 3710166800J). It actually defines the
“Area X” (where the subject wetlands are located) as being located outside the 500-year floodplain.
On October 8, 2015, Baker personnel met with DMS staff to evaluate the area in question. The wetlands
are a fairly narrow strip located along the toe-of-slope of a hill where the hydrology is provided by a
seep or series of seeps. In three locations the seep actually reaches the surface as shallow ponded
water as shown in Figure 1 and Photograph 1. Hydric soils were also identified in the wetland areas
(Photograph 2), confirming what was determined in the hydric soils report conducted by Chandler Soil
Corporation in 2010. The wetlands are almost entirely currently designated as wetland restoration at a
1:1 ratio, though a small area in the northernmost wetland is enhancement at a 2:1 ratio. The following
Tables detail the WMU credit breakdowns for the signed contract, the mitigation plan, and the proposed
revision.
Table 1. Currently Contracted WMU Credit Breakdown
Riparian WMUs Non-Riparian WMUs Total WMUs
5.89 0.62 6.51

Table 2. Current WMU Breakdown in Mitigation Plan
Riparian WMUs:
Restoration
Riparian WMUs:
Enhancement
Riparian WMUs:
Creation
Non-Riparian
WMUs: Total
Total
WMUs
5.30 1.64 0.33 0.0 7.27

Table 3. Proposed Revised WMU Breakdown
Riparian WMUs:
Restoration
Riparian WMUs:
Enhancement
Riparian WMUs:
Creation
Non-Riparian
WMUs:
Restoration
Non-Riparian
WMUs:
Enhancement
Total
WMUs
4.56 1.60 0.33 0.74 0.04 7.27
Thus, the proposed revision does not alter the total wetland acreage being claimed, the ratios for credit
calculation, nor the total number of WMUs to be provided. In fact, it still provides an excess of credits
for the contracted Riparian credit value, while also fulfilling the Non-Riparian credit need.
Please feel free to contact me with any comments, questions, or detailed mapping requests.
Sincerely,
Scott King, NC-LSS #1301, PWS #1908

Photograph 1: Ponded water from a hillslope seep located in the wetlands of interest.

Photograph 2: Hydric soils found within the wetlands of interest.
!A
!A
!A
!A
FEMA Zone AE(100yr)
FEMA Zone X(outside 500yr)
100YR FloodplainLOMR Revised
0.57 WMU
0.04 WMU0.17 WMU
NC OneMap, NC Center for Geographic Information and Analysis, NC 911Board
0 200Feet
FEMA Floodplain and Wetland MapUpper Silver Creek Site
±
Proposed Non-Riparian WetlandsRestoration (1:1 credit, 0.74 WMUs total)Enhancement (2:1 credit, 0.04 WMU total)
!A Seep Location
Wetland Monitoring Well
Revised LOMR 100-Year FloodplainUpper Silver Creek Stream
Area ofInterest
FEMA FIRM Panel3710166800JEffective Date: Sept 5, 2007
±
Upper Silver Creek Project
Not to Scale
Figure 2