HomeMy WebLinkAbout20110931 Ver 1_U-3810 mitigation plan final(revised June 2012)_20160321
On-site Mitigation Plan
SR 1406 (Piney Green Road) from NC 24 to US 17
Jacksonville, Onslow County, North Carolina
T.I.P. Number U-3810
WBS No. 35801.1.1
June 21, 2012 (Revised)
1.0 BASELINE INFORMATION
The North Carolina Department of Transportation (NCDOT) will perform on-site mitigation for
unavoidable jurisdictional impacts associated with Transportation Improvement Program (TIP)
U-3810, the widening of SR 1406, Piney Green Road from NC 24 to US 17. The onsite
mitigation site will provide for 1.05 acres of riparian wetland restoration and 7.87 acres of
riparian wetland preservation.
The site is located within USGS Hydrologic Cataloging Unit 03030001, and NC Division of
Water Quality (NCDWQ) sub-basin 03-05-02 of the White Oak River Basin. The site is located
immediately east of SR 1406, Piney Green Road in Jacksonville, Onslow County, on land that is
entirely owned by the North Carolina Department of Transportation. Adjacent land uses are
mainly residential with scattered commercial zones, fragmented forests, and large riparian forest
systems on both sides of Piney Green Road.
Two jurisdictional features are associated with the roadway project area: Little Northeast Creek,
which is a 303(d) listed tributary of Northeast Creek, and the adjacent Cypress-Gum Swamp
community located within the floodplain of Little Northeast Creek. Little Northeast Creek has
been assigned Stream Index Number 19-16-2 with a classification of C; NSW. The Cypress Gum
Swamp community (Wetland #5 in the NRTR) has a NCDWQ rating of 93. It is classified as a
riverine swamp forest according to the NC Wetland Assessment Method.
The U-3810 Natural Resources Technical Report dated January 2006 provides further details
concerning existing roadway and project study area conditions.
2.0 SITE SELECTION
The mitigation site is immediately adjacent to a section of Piney Green Road that will be
widened for the proposed TIP U-3810, east of roadway -L- Sta. 222+68 to 233+71.50.
Currently the site is characterized in the Natural Resource Technical Report as a
maintained/disturbed upland community. The site consists of old fill in an area that was
previously cypress gum swamp wetland. The fill varies in depth from 1 to 5 feet and extends out
to the bank of a tributary to Little Northeast Creek.
A Dual Utility Easement (DUE) containing both overhead power lines and a sewer line runs
parallel to Piney Green Road and crosses the westernmost portion of the mitigation site.
3.0 SITE PROTECTION INSTRUMENT
The mitigation site is located within the NCDOT Right-of-Way for the project. It will be
managed to prohibit all use inconsistent with its use as mitigation property, including any
activity that would materially alter the biological integrity or functional and educational value of
the site, consistent with the mitigation plan.
The site is designated on the plan sheets as a mitigation area and will placed on the Natural
Environment Section’s Mitigation GeoDatabase. This database is provided to all NCDOT
personnel as a record of mitigation sites and their attributes, including prohibited activities.
NCDOT is held by virtue of the permit associated with this mitigation site and the associated
roadway impacts to protect the site in perpetuity.
4.0 OBJECTIVES
The goal of the proposed onsite mitigation is to offset impacts due to construction of U-3810 by
restoring the adjacent wetland system to its natural conditions. This will be achieved through
restoration of 1.05 acres and preservation of 7.87 acres of riparian wetland in the floodplain of
Little Northeast Creek.
5.0 MITIGATION WORK PLAN
The site will be constructed in conjunction with the construction of U-3810. The restoration of
the wetland area will be accomplished via excavation of the fill material out to the bank of the
tributary of Little Northeast Creek. The site will be graded to match the target elevations in the
adjacent wetland.
Approximately 0.91 acres of the 1.05 acre restoration area will be reforested to match the
existing species composition of the adjacent riverine swamp forest preservation area. The area
will be planted at a density of 680 stems per acres of bare root seedlings of a mixture of swamp
tupelo (Nyssa sylvatica var. biflora), bald cypress (Taxodium distichum), green ash (Fraxinus
pennsylvanica), water tupelo (Nyssa aquatic), and tulip poplar (Liriodendron tulipifera). The
northern bank of the tributary to Little Northeast Creek will be planted on three foot centers with
live stakes of silky dogwood (Cornus amomum) and black willow (Salix nigra). This area is
represented by cross hatching on the attached figure.
The remaining 0.14 acres of the restoration area is within the DUE. This area, represented by
diagonal hatch on the attached figure, will be seeded using a native wetland seed mix typical of a
non-tidal freshwater marsh.
No work will be performed within the 7.87 acre riverine swamp forest preservation area.
See the attached figure for the specific locations of each mitigation area.
The Natural Environment Unit shall be contacted to provide construction assistance to ensure
that the mitigation areas are constructed appropriately. An as-built report will be submitted
within 60 days of completion of the project.
6.0 PERFORMANCE STANDARDS
Success for vegetation monitoring within the restoration area is based on the survival of planted
woody vegetation and coverage of seeded herbaceous vegetation.
Vegetation success shall be measured by survivability over a 5-year monitoring
period. Survivability will be based on 320 stems/acre after three (3) years and 260 stems after
five (5) years. . If the surviving vegetation densities are below the required thresholds after the
five-year monitoring period, the site may still be declared successful at the discretion of and with
written approval from the regulatory agencies.
NEU will be contacted during construction to provide oversight and ensure that the site is graded
to match the existing, adjacent, reference wetland elevation.
Upon successful completion of construction, the following monitoring strategies are proposed for
the mitigation site. NCDOT will document monitoring activities on the site in an annual report
distributed to the regulatory agencies.
7.0 MONITORING REQUIREMENTS
No specific hydrological monitoring is proposed for the wetland restoration area. The target
elevation is based on the reference wetland areas and will be verified during construction.
Constructing the site at the adjacent wetland elevation will ensure the hydrology in the restored
area is similar to the hydrology in the reference area.
NCDOT shall monitor the restoration area by visual observation, vegetation plots and photo
points for vegetation survival. A survey of vegetation during the growing season shall be
conducted annually over the five-year monitoring period and submitted to the regulatory
agencies via the NCDOT website. Monitoring will be initiated upon successful completion of
the site grading and planting.
8.0 OTHER INFORMATION
None
9.0 DETERMINATION OF CREDITS
Based on field and meeting discussions with agency representatives and per the NCDOT plans
and 401/404 permit application for U-3810, NCDOT proposes the following riparian wetland
mitigation and ratios for the site: 0.91 acres of riverine swamp forest restoration at 1:1 ratio
(0.91), 0.14 acres of non-tidal freshwater marsh at 2:1 ratio (0.07), and 7.87 acres of riverine
swamp at a 10:1 ratio (0.78).
An as-built report will be submitted within 60 days of completion of the each mitigation site to
verify actual mitigation areas constructed and planted. The success of the mitigation areas and
determination of final credits will be based upon successful completion and closeout of the
monitoring period.
9.1 CREDIT RELEASE SCHEDULE
NCDOT proposes immediate, full release of the proposed mitigation as on-site mitigation for
unavoidable impacts associated with U-3810.
10.0 GEOGRAPHIC SERVICE AREA
The proposed Geographic Service Area (GSA) for the mitigation area is composed of the 8-digit
Hydrologic Cataloging Unit (HUC) 03030001.
11.0 MAINTENANCE PLAN
The site will be held by NCDOT and placed on the NEU mitigation geodatabase. Once
monitoring is completed and the site is closed out, it will be placed in the NCDOT Stewardship
Program for long term maintenance and protection.
If an appropriate third party recipient is identified in the future, then the transfer of the property
will include a conservation easement or other measure to protect the natural features and
mitigation value of the site in perpetuity.
12.0 LONG TERM ADAPTIVE MANAGEMENT PLAN
The site will be managed by the NCDOT according to the mitigation plan. Encroachments into
the area will be investigated and appropriate measures taken to minimize any negative effects. In
the event that unforeseen issues arise that affect the management of the site, any remediation will
be addressed by NCDOT in coordination with the Interagency Review Team.
13.0 FINANCIAL ASSURANCES
NCDOT is held by permit conditions associated with U-3810 to preserve the mitigation site.
NCDOT has established funds for each project and within each Division to monitor the
mitigation site and to protect it in perpetuity.
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