Report_4_NEPA_Wetland_Mgmt_Plan.pdf

Prepared for:

Federal Highway Administration Eastern Federal Lands Highway Division 21400 Ridgetop Circle Sterling, Virginia 20166-6511

FINAL

COMPENSATORY WETLAND MITIGATION PLAN

FOR

TIDAL MARSH WETLAND RESTORATION

PROJECT FOPU 10(3)

FORT PULASKI NATIONAL MONUMENT

CHATHAM COUNTY, GEORGIA

OCTOBER 2015

FINAL

COMPENSATORY WETLAND MITIGATION PLAN

FOR

TIDAL MARSH WETLAND RESTORATION

PROJECT FOPU 10(3)

FORT PULAKSI NATIONAL MONUMENT

CHATHAM COUNTY, GEORGIA

Prepared for:

Federal Highway Administration Eastern Federal Lands Highway Division

21400 Ridgetop Circle Sterling, Virginia 20166-6511

Prepared by:

Gulf South Research Corporation 8081 Innovation Park Drive

Baton Rouge, Louisiana 70820

October 2015

TABLE OF CONTENTS

1.0 PROJECT REQUIRING MITIGATION.................................................................... 1-1

1.1 Background .......................................................................................................... 1-1

1.2 Project FOPU 10(3) ............................................................................................. 1-1

1.3 Regulatory Guidance ........................................................................................... 1-2

2.0 COMPENSATORY WETLAND MITIGATION....................................................... 2-1

2.1 Sponsor ................................................................................................................ 2-1

2.2 Agent, Consultant, and/or Representative ........................................................... 2-1

2.3 Mitigation Goals and Objectives ......................................................................... 2-2

2.3.1 Functions Lost at Impact Site .................................................................. 2-2

2.3.2 Functions to Be Gained at Mitigation Site............................................... 2-2

2.3.3 Watershed Improvements to Be Gained at Mitigation Site ..................... 2-2

2.4 Baseline Information............................................................................................ 2-3

2.4.1 Impact Sites.............................................................................................. 2-3

2.4.1.1 Physical Attributes.................................................................... 2-3

2.4.1.2 Historic Land Use ..................................................................... 2-4

2.4.1.3 Current Land Use...................................................................... 2-4

2.4.1.4 Resources Impacted .................................................................. 2-4

2.4.2 Mitigation Sites........................................................................................ 2-5

2.4.2.1 Physical Attributes.................................................................... 2-5

2.4.2.2 Historic Land Use ..................................................................... 2-6

2.4.2.3 Current Land Use...................................................................... 2-6

2.4.2.4 Resources Impacted .................................................................. 2-6

2.5 Wetland Assessment Methods ............................................................................. 2-6

3.0 MITIGATION SITE SELECTION AND JUSTIFICATION ................................... 3-1

3.1 Selecting the Proposed Sites ................................................................................ 3-1

3.2 Likelihood of Success .......................................................................................... 3-1

4.0 MITIGATION WORK PLAN...................................................................................... 4-1

4.1 Location ............................................................................................................... 4-1

4.2 Construction Plan................................................................................................. 4-1

4.3 Planned Mitigation Site Conditions ..................................................................... 4-1

4.4 Verification of Mitigation Site Conditions .......................................................... 4-2

5.0 PERFORMANCE STANDARDS AND MONITORING REQUIREMENTS ........ 5-1

5.1 Performance Standards ........................................................................................ 5-1

5.2 Reference Sites..................................................................................................... 5-1

5.3 Success Criteria.................................................................................................... 5-1

5.3.1 Hydrology ................................................................................................ 5-1

5.3.2 Vegetation ................................................................................................ 5-1

5.4 Comparison of Functions..................................................................................... 5-2

5.5 Monitoring Requirements .................................................................................... 5-2

6.0 SITE PROTECTION AND MAINTENANCE ........................................................... 6-1

Project FOPU 10(3) i Final Wetland Mitigation Plan October 2015

6.1 Responsible Parties .............................................................................................. 6-1

6.2 Protective Measures ............................................................................................. 6-1

6.3 Maintenance Plan................................................................................................. 6-1

6.4 Schedule............................................................................................................... 6-1

7.0 MONITORING PLAN .................................................................................................. 7-1

7.1 Schedule............................................................................................................... 7-1

7.2 Responsible Parties .............................................................................................. 7-1

7.3 Monitoring Data................................................................................................... 7-1

8.0 ADAPTIVE MANAGEMENT PLAN.......................................................................... 8-1

8.1 Remedial Measures.............................................................................................. 8-1

8.2 Responsible Parties .............................................................................................. 8-1

9.0 FINANCIAL ASSURANCES ....................................................................................... 9-1

10.0 REFERENCES............................................................................................................. 10-1

LIST OF TABLES

Table 2-1. E2EM1N Wetlands Impacts ................................................................................ 2-5 Table 2-2. HGM Model Summary of Results ....................................................................... 2-7 Table 2-3. Summary of FOPU 10(3) Impacts, Required Compensatory Mitigation, and

Proposed Mitigation............................................................................................. 2-8 Table 6-1. Tentative Project Schedule .................................................................................. 6-2

LIST OF PHOTOGRAPHS

Photograph 1-1. Fort Pulaski Bridge.......................................................................................... 1-1 Photograph 2-1. Smooth cordgrass within the Southern Approach Impact Area ...................... 2-4 Photograph 2-2. Bushy seaside tansy along the Southern Approach Impact Area.................... 2-4 Photograph 2-3. Proposed Mitigation Site along the Northern Approach of the Fort Pulaski

Bridge .............................................................................................................. 2-5 Photograph 2-4. Proposed Mitigation Site along the Southern Approach of the Fort Pulaski

Bridge .............................................................................................................. 2-5 Photograph 4-1. Smooth cordgrass multi-stem plug removal (excavation) from an existing tidal marsh ............................................................................................................... 4-2

LIST OF APPENDICES

Appendix A. Mitigation Plan Figures Appendix B. Project FOPU 10(3) Plans Appendix C. HGM Trip Report Appendix D. HGM Data

Project FOPU 10(3) ii Final

1.0 PROJECT REQUIRING MITIGATION

1.1 Background

An Environmental Assessment (EA) was prepared by the National Park Service (NPS), in cooperation with the Federal Highway Administration (FHWA), in January 2013 for the repair or replacement of the Fort Pulaski Bridge at Fort Pulaski National Monument (Fort Pulaski) in Chatham County, Georgia (Appendix A: Figure 1-1). The NPS owns and operates Fort Pulaski, which includes most of Cockspur Island and all of adjacent McQueens Island (Appendix A:

Figure 1-2).

The Fort Pulaski Bridge (Photograph 1-1) is located along the entrance road to Fort Pulaski from U.S. Highway 80 (US 80) and spans the South Channel of the Savannah River (Appendix A: Figure 1-2). It is approximately 1,300 feet (396 meters) in length, carries a two-lane roadway, and provides the only ingress and egress to Fort Pulaski and Cockspur Island. Maintaining the bridge in a safe condition is essential to NPS operations. The bridge also provides access to a U.S. Coast Guard Station and to the Savannah Bar Pilots, which operate on the west end of Cockspur Island.

The Fort Pulaski Bridge was originally constructed in 1938. The bridge was rehabilitated in 1965. More recently, repair projects in 1996 and 2008 have been completed to extend the life of the bridge. However, the bridge has continued to deteriorate. The timber piles, steel beams and bearings, and composite timber/concrete spans all exhibit signs of deterioration. In addition, the embankment no longer provides adequate protection from the flow of the river. Recent assessments of the bridge have deemed it structurally deficient, and its current configuration poses a safety hazard to pedestrians and bikers who must share the narrow bridge with vehicular traffic.

1.2 Project FOPU 10(3)

In March 2015, the NPS and FHWA prepared an updated EA to analyze reasonable and feasible alternatives and their impacts and to reevaluate alternatives that were previously determined to be unreasonable due to cost. In the March 2015 EA, the NPS and FHWA considered a range of alternatives for the proposed rehabilitation or replacement of the Fort Pulaski Bridge that would meet the project objectives (NPS 2015). Replacement of the existing bridge with a new, two-lane bridge on a new alignment has been identified as the Preferred Alternative, hereafter referred to as Project FOPU 10(3).

Photograph 1-1. Fort Pulaski Bridge

Project FOPU 10(3) 1-1 Final

Project FOPU 10(3) would construct a new two-lane bridge upstream of the existing bridge that meets current American Association of State Highway and Transportation Officials (AASHTO) specifications with regard to lane width, shoulder width, live load capacity, and crashworthy railing system. The new bridge would be approximately 29 feet (8.8 meters) wide (including the railing width), with two 11-foot-wide (2.6-meter-wide) travel lanes and a 5-foot (1.5-meter) shoulder (see plans in Appendix A). Project FOPU 10(3) would be constructed in one construction phase. Riprap would be placed at north and south bridge abutments to protect the abutments from scour. After construction is completed and the new bridge is open, the existing bridge, road fill, and riprap to the low water line would be removed. Appendix B contains plans and detailed information for Project FOPU 10(3).

Project FOPU 10(3) would have adverse, permanent impacts on approximately 0.29 acre (0.12 hectare) of tidal marsh wetlands. The roadway approaches for the existing bridge would be restored to tidal marsh wetlands in order to compensate for the loss of wetland function due to the placement of fill material to construct the new bridge. There would be no temporary impacts on wetlands during construction. Sheet piling would be installed temporarily in order to dewater the area to construct the bridge abutments, impacting only existing riprap areas. Silt fence and construction fencing would be placed along the fill limits. The fill would be placed from the existing road and graded in layers to meet the final grade. Geo-fabric may also be used to wrap the layers of fill material.

Construction of the approaches and bridge would be accessed from the existing roadway shoulders and new approaches. No construction equipment access through wetlands would be necessary. After the existing bridge, road fill, riprap to the low water line are removed, the northern and southern roadway approach areas, totaling approximately 0.54 acre (0.22 hectare), would be graded and restored to tidal marsh wetlands.

1.3 Regulatory Guidance

The NPS Director’s Order #77-1: Wetland Protection requires a consistency with “no net loss of wetlands” and compensatory mitigation for impacts on wetlands that total 0.10 acre (0.04 hectare) or more (NPS 2012). Under Director’s Order #77-1, compensation wetlands must, at a minimum, provide one-for-one (1:1) wetland function replacement. Director’s Order #77-1 also states that wetland compensation sites must be on lands managed by the NPS, with the following recommended priority order: 1) within the same wetland system as the impacted wetland; 2) within the same watershed; or 3) in another watershed within the same NPS unit.

Compensation of wetland impacts is also required by the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers (USACE) under Section 404 of the Clean Water Act.

The USACE, Savannah District, has developed a Standard Operating Procedure, Compensatory Mitigation, Wetlands, Openwater & Streams (SOP) to provide methodology for calculating mitigation credit requirements (USACE 2004). The SOP allows for compensatory mitigation supported by the Hydrogeomorphic Approach to Wetland Functional Assessment (HGM Approach) to assess wetland functions.

Project FOPU 10(3) 1-2 Final

On July 21, 2014, the NPS and FWHA held a pre-application meeting to discuss Project FOPU 10(3) with the USACE, Savannah District. Discussions during this meeting and subsequent phone discussions indicated that it was appropriate to complete a wetland functional assessment using the HGM Approach for the small area of wetlands impacted by the proposed project and the proposed compensatory mitigation areas to maintain compliance with the NPS’s 1:1 wetland function replacement and the USACE’s goal of no net loss for aquatic resources, rather than following the Savannah District’s 2004 SOP for calculating credits.

Project FOPU 10(3) 1-3 Final

2.0 COMPENSATORY WETLAND MITIGATION

2.1 Sponsor

The sponsor for Project FOPU 10(3) is the FHWA, Eastern Federal Lands Highway Division.

The FHWA, in cooperation with the NPS, will provide all the necessary regulatory and administrative coordination with the USACE and other Federal, state, and local governmental entities that may be involved in the review and approval of this mitigation plan and the activities proposed herein. The FHWA will also complete the technical and environmental tasks necessary for site assessment and baseline monitoring, development of mitigation concepts and restoration design, coordination and oversight of mitigation site construction, monitoring mitigation site as-built conditions and performance criteria, and preparing appropriate technical documentation and reports, and final project closure.

The primary contact is:

Ms. Lisa Landers Title: Environmental Specialist Federal Highway Administration Eastern Federal Lands Highway Division 21400 Ridgetop Circle Sterling, Virginia 20166-6511 Phone: (571) 434-1592 E-mail: lisa.landers@dot.gov

2.2 Agent, Consultant, and/or Representative

Gulf South Research Corporation (GSRC) is under contract with the FHWA to complete a wetland functional assessment using the HGM Approach for the wetlands impacted by Project FOPU 10(3) and the proposed compensatory mitigation areas at Fort Pulaski. GSRC is also under contract with the FHWA to prepare a compensatory wetland mitigation plan for Project FOPU 10(3). In addition, GSRC will also be providing assistance to the FHWA in completing the technical and environmental tasks necessary for site assessment and baseline monitoring prior to project implementation and with regulatory and administrative coordination with the USACE and other Federal, state, and local governmental entities as necessary.

The primary contact is:

Ms. Carey Lynn Perry Title: Project Manager Gulf South Research Corporation 8081 Innovation Park Drive Baton Rouge, Louisiana 70820 Phone: (225) 757-8088 E-mail: clperry@gsrcorp.com

Project FOPU 10(3) 2-1 Final

2.3 Mitigation Goals and Objectives

The goals are to replace wetland functions lost or degraded at the impact sites with additional functions at wetland mitigation sites and to provide overall watershed improvement at the mitigation sites. The northern and southern roadway approaches of the existing bridge, along with road fill material and existing riprap to the low water line, would be removed and restored to accomplish the following mitigation objectives:

1. Compensate for wetland functions lost or degraded due to Project FOPU 10(3)

2. Maintain consistency with the NPS “no net loss of wetlands” mitigation requirement

3. Maintain compliance with the NPS Director's Order #77-1 to provide 1:1 wetland function replacement and the USACE’s goal of no net loss.

2.3.1 Functions Lost at Impact Site

Wetlands in the impact areas perform biotic and hydrologic functions. High and low marsh composed primarily of smooth cordgrass (Spartina alterniflora) is present immediately adjacent to the Fort Pulaski Entrance Road in an area of transition from the higher elevation of the road to the lower elevation of the tidal marsh. These low marshes, along with the tidal marsh wetlands throughout the impact site, provide important fish and wildlife habitat, including essential fish habitat (EFH). The marshes provide foraging habitat, refuge from predation, and nursery habitat.

Tidal marshes also provide floodwater storage, erosion and sediment control, detritus export, and water purification. Tidal marsh wetlands perform the hydrologic function of erosion and sediment control. In addition, tidal marsh wetlands at the impact sites help filter pollutants from water and act as buffers against offshore storms. Tidal flats in the impact areas support worm and clam populations, and are often important to migratory birds.

2.3.2 Functions to Be Gained at Mitigation Site

Restoration of an impervious roadway to tidal marsh wetland would provide erosion and sediment control, habitat for fish and wildlife, including EFH, and the hydrologic functions of erosion and sediment control and floodwater storage of the South Channel of the Savannah River. While it is anticipated that the mitigation sites will also include a high marsh fringe immediately adjacent to the road restoring the functions lost for that wetland subtype, the primary goal of the mitigation is to compensate for the loss of the low marsh.

2.3.3 Watershed Improvements to Be Gained at Mitigation Site

Restoration of tidal marsh wetlands at Fort Pulaski would address the following watershed needs:

� Replacement (minimum 1:1 functional replacement) of lost biological, chemical, and physical functions of the tidal marsh wetland system.

� Tidal marsh wetland in-kind resource type to be restored will consist of tidal marsh that is contiguous with an existing, fully functional tidal marsh adjacent to the South Channel of the Savannah River (Appendix A: Figures 2-1 and 2-2).

� Increased high-quality habitat acreage for estuarine dependent aquatic invertebrates and vertebrates (e.g., crustaceans, shellfish, and fish).

Project FOPU 10(3) 2-2 Final

� Replacement at a minimum of equal water quality functions for tidal marsh wetlands within the watershed.

2.4 Baseline Information

2.4.1 Impact Sites

2.4.1.1 Physical Attributes

The impacted tidal marsh wetlands for Project FOPU 10(3) are located on NPS property, approximately 11 miles (18 kilometers) southeast of Savannah in Chatham County, Georgia, along both the northern and southern approaches to the Fort Pulaski Bridge (Appendix A:

Figures 2-1 and 2-2). The tidal marshes are included in the South Atlantic Regional wetland subclass. The South Atlantic subclass, from Virginia Beach, Virginia, to Indian River, Florida, primarily includes temperate wetlands, and is further subdivided into three sub-regions based on gross differences in tidal regimes (microtidal, macrotidal, and tidally restricted lagoons) (Shafer and Yozzo 1998).

The tidal marsh wetlands at the impact sites are macrotidal, with a daily tidal range of approximately 6.92 feet (2.93 meters) (National Oceanic and Atmospheric Administration [NOAA] 2015). Tidal marshes in the impact areas are generally inundated twice daily by high tides. Mean high water and mean low water elevations are approximately 3.08 and -3.42 feet

0.938 and -1.04 meters) (NAVD88), respectively (NOAA 2015). The sites are located in the Lower Savannah River Hydrological Unit Code (HUC) 03060109 (Appendix A: Figure 2-3) and on the Fort Pulaski U.S. Geological Survey (USGS) Quadrangle Map (Appendix A: Figure 2-4).

The National Wetland Inventory (NWI) Map of the sites shows the presence of one wetland type (Appendix A: Figure 2-5), estuarine, intertidal, emergent, persistent wetlands (E2EM1N).

A delineation of the wetlands was completed as part of the 2015 EA. The wetlands in the impact area were identified as intertidal wetlands, and include E2EM1N, estuarine, intertidal, unconsolidated shore, mud wetlands (E2US3), and estuarine, intertidal, rocky shore, rubble, artificial wetlands (E2RS2r) (Dial Cordy and Associates, Inc. 2011). The limits of the intertidal zone are from the upland edge of the wetland to the extreme low water elevation of spring tides, or mean low low water (MLLW). The MLLW elevation in the impact areas is approximately -4.05 feet (-1.23 meters) (Dial Cordy and Associates, Inc. 2011). In addition, an approximately 3- to 5-foot-wide fringe (0.10 acre) of high marsh is present within the 0.29-acre impact sites.

The E2EM1N wetlands are a near monoculture composed of smooth cordgrass (Photograph 2-1).

Smooth cordgrass remains standing at the sites from one growing season to the next. The upper fringe of the marsh within the project area is very narrow and is a mix of smooth cordgrass and bushy seaside tansy (Borrichia frutescens) (Photograph 2-2). Other species present in the tidal area include bushy seaside tansy, saltgrass (Distichilis spicata), and eastern baccharis (Baccharis halimifolia). According the Natural Resources Conservation Service (NRCS 2015), the soil type within the impact areas is tidal marsh, salty (Appendix A: Figure 2-6).

Project FOPU 10(3) 2-3 Final

Photograph 2-1. Smooth cordgrass within the Southern Approach Impact Area

Photograph 2-2. Bushy seaside tansy along the Southern Approach Impact Area

2.4.1.2 Historic Land Use

The War Department declared Fort Pulaski a National Monument on October 15, 1924. The monument was transferred to the NPS on August 10, 1933. The history of the bridge dates back to 1936, when Congress passed an act that expanded Fort Pulaski to nearly 500 acres (202 hectares) and permitted the construction of a bridge across the South Channel from McQueens Island to Cockspur Island (NPS 2003). Ferry service, initiated in 1934, provided access to Cockspur Island at this time. The Civilian Conservation Corps (CCC) filled in marshes to prepare for the construction of a bridge across the South Channel, and the construction of the bridge was completed as a Public Works Administration project. The CCC worked on the landscape of the approaches to the bridge and some of the riprap at its terminal abutments. The bridge was opened to the public in May 1938 (NPS 2003).

The bridge was rehabilitated in 1965 and repaired in 1996 and again in 2008 to extend the life of the bridge. The repair projects addressed all serious structural deficiencies noted at the time, but primarily repaired the deteriorated piles.

2.4.1.3 Current Land Use

The NPS-owned land on either side of the northern and southern bridge approaches consists of E2EM1N wetlands that are a near monoculture of smooth cordgrass (see Photograph 2-1). The upper fringe of the marsh within the project area is very narrow and is a mix of smooth cordgrass and bushy seaside tansy. Other species present in the tidal area include bushy seaside tansy, saltgrass, and eastern baccharis.

2.4.1.4 Resources Impacted

Project FOPU 10(3) would have adverse impacts on the cultural landscape, species of special concern, wetlands, and wildlife and wildlife habitat; however, measures would be taken to mitigate the adverse impacts. Removal of the existing bridge would remove a feature that contributes to the cultural landscape. Documentation of the bridge would be done prior to its demolition.

Construction of the bridge on a new alignment would require in-water, work which would disrupt aquatic species and would permanently fill tidal marsh located adjacent to the bridge.

Project FOPU 10(3) would result in unavoidable impacts on approximately 0.29 acre (0.12

Project FOPU 10(3) 2-4 Final hectare) of E2EM1N wetlands on NPS property at Fort Pulaski (Table 2-1; Appendix A: Figures 2-1 and 2-2). Once the new bridge is opened, Project FOPU 10(3) would have long-term beneficial impacts on visitor use and experience, park operations, and health and safety.

Table 2-1. E2EM1N Wetlands Impacts

Location E2EM1NWetlands Impact Area Square Feet Acres Hectares

Northern Approach 5,865 0.13 0.05 Southern Approach 7,185 0.16 0.06

TOTAL 13,050 0.29 0.11

2.4.2 Mitigation Sites

2.4.2.1 Physical Attributes

The removal of the existing bridge, road fill, and associated riprap to the low water line would allow for 0.54 acre (0.22 hectare) of E2EM1N wetlands to be restored on-site (Appendix A:

Figures 2-1 and 2-2). The mitigation sites are currently paved entrance road areas adjacent to E2EM1N wetlands (Photographs 2-3 and 2-4). The sites consist of artificial, impervious surfaces, including concrete and mowed turf grass. Prior to construction of the Fort Pulaski bridge, the mitigation areas would have consisted of tidal marsh contiguous to the fully functioning existing tidal marsh, as described in 2.4.1 for the impact sites.

Photograph 2-3. Proposed Mitigation Site along the Northern

Approach of the Fort Pulaski Bridge

Photograph 2-4. Proposed Mitigation Site along the Southern Approach of the Fort Pulaski Bridge

The mitigation sites are located in the Lower Savannah River HUC 03060109 (Appendix A:

Figure 2-3) and on the Fort Pulaski USGS Quadrangle Map (Appendix A: Figure 2-4). The NWI Map of the sites shows the presence of one wetland type (Appendix A: Figure 2-5), E2EM1N. According the NRCS, soils within the mitigation areas are currently listed tidal marsh, salty (Appendix A: Figure 2-6).

Project FOPU 10(3) 2-5 Final

2.4.2.2 Historic Land Use

Prior to construction of the Fort Pulaski bridge, the mitigation areas would have consisted of tidal marsh, as described in 2.4.1 for the impact sites.

2.4.2.3 Current Land Use

The entrance road to Fort Pulaski is the only route connecting Cockspur Island and Fort Pulaski to McQueens Island from US 80. Along the entrance road, the Fort Pulaski Bridge carries two travel lanes across the South Channel of the Savannah River. The bridge is approximately 1,300 feet (396 meters) long and 25 feet (7.6 meters) wide.

2.4.2.4 Resources Impacted

Wetland mitigation would restore tidal marsh wetlands in the project area to compensate for wetland functions lost as a result of Project FOPU 10(3). Once the existing bridge is removed, the FHWA would obliterate the paved northern and southern roadway approach areas and remove road fill material and existing riprap to the low water line to provide approximately 0.54 acre (0.22 hectare) of in-kind tidal marsh wetland restoration. Due to the difference in elevation of the road and surrounding tidal marsh, it is anticipated that a fringe of high marsh will develop between the new approach roach and the low marsh, similar in width (3 to 5 feet wide) to the existing conditions. Approximately 0.15 acre of the 0.54-acre mitigation area is anticipated to be high marsh, resulting in a restoration of approximately 0.39 acre of smooth cordgrass-dominated low marsh.

2.5 Wetland Assessment Methods

In June 2015, GSRC completed a wetland functional assessment using the HGM Approach to identify whether the proposed mitigation areas could be restored to provide 1:1 or better replacement of wetland functions impacted by Project FOPU 10(3). Because no regional guidebook has been developed for use in South Atlantic tidal marsh wetlands, wetlands were assessed based on application of the HGM Approach developed for the Tidal Fringe Wetlands along the Mississippi and Alabama Gulf Coast (Shafer et al. 2007). The May 2015 HGM Trip Report is provided in Appendix C, and HGM data can be found in Appendix D.

The HGM model was applied based on the Chapter 5 Assessment Protocol (Shafer et al. 2007).

GSRC collected field data for model variables on May 5, 2015, at Fort Pulaski. Data was collected within four Wetland Assessment Areas (WAAs). Two WAAs represented project impact areas, while the other two areas were used to assess mitigation potential in the tidal marsh adjacent to the existing roadway, which is the area proposed for compensatory mitigation (see figures in Appendix C: HGM Trip Report). The applied HGM model components include five main functional variables:

1. Wave Energy Attenuation

2. Biogeochemical Cycling

3. Nekton Use Potential

4. Provide Habitat for Tidal Marsh-Dependent Wildlife

5. Maintain Characteristic Plant Community Structure and Composition

Project FOPU 10(3) 2-6 Final

Table 2-2 presents the summary of results from application of the HGM model. Along the northern roadway approach, approximately 0.58 acre (0.24 hectare) of tidal marsh would need to be restored for every 1.0 acre (0.49 hectare) of tidal marsh impacted to compensate for the biological, chemical, and physical functions that will be lost. For each acre of tidal marsh impacted along the southern approach, only 0.38 acre (0.15 hectare) of tidal marsh would need to be restored to achieve a minimum 1:1 ratio of functional replacement. Applying the HGM model results, Project FOPU 10(3) is in compliance with the NPS Director’s Order #77-1 for a minimum 1:1 functional replacement.

Overall, in-kind restoration of approximately 0.14 acre (0.05 hectare) of tidal marsh within the watershed would be required to compensate for wetland functions lost or degraded due to the 0.29-acre tidal marsh impact of Project FOPU 10(3) and to maintain compliance with NPS Director's Order #77-1 (Table 2-3). Moreover, after the existing bridge is removed, the FHWA proposes to remove the northern and southern roadway approach areas, along with road fill material and existing riprap to the low water line, to provide approximately 0.54 acre (0.22 hectare) of in-kind restoration, which would provide nearly a 1:2 ratio of tidal marsh functional replacement (Table 2-3).

Table 2-2. HGM Model Summary of Results

HGM Function North Roadway Approach South Roadway Approach

WAA 1

(Impact)

WAA 2

(Mitigation)

WAA 3

(Impact)

WAA 4

(Mitigation)

Wave Energy Attenuation Area (hectares) 0.07 0.12 0.07 0.20 HGM Functional Capacity Index (FCI) 0.671 0.671 0.671 0.671 HGM Functional Capacity (FC) per hectare 0.047 0.080 0.047 0.121 Biogeochemical Cycling Area (hectares) 0.07 0.12 0.07 0.20 HGM Functional Capacity Index (FCI) 0.711 0.711 0.711 0.711 HGM Functional Capacity (FC) per hectare 0.050 0.085 0.050 0.128 Nekton Habitat Utilization Area (hectares) 0.07 0.12 0.07 0.20 HGM Functional Capacity Index (FCI) 0.467 0.467 0.467 0.467 HGM Functional Capacity (FC) per hectare 0.033 0.056 0.033 0.084 Provide Habitat for Marsh-Dependent Wildlife Area (hectares) 0.07 0.12 0.07 0.20 HGM Functional Capacity Index (FCI) 0.418 0.418 0.525 0.577 HGM Functional Capacity (FC) per hectare 0.029 0.050 0.037 0.104 Characteristic Plant Community Structure and Composition Area (hectares) 0.07 0.12 0.07 0.20 HGM Functional Capacity Index (FCI) 0.600 0.600 0.600 0.600 HGM Functional Capacity (FC) per hectare 0.042 0.072 0.042 0.108

OVERALL HGM FC PER HECTARE 0.201 0.344 0.208 0.545

OVERALL HGM FC PER ACRE 0.496 0.850 0.514 1.346

Project FOPU 10(3) 2-7 Final

Table 2-3. Summary of FOPU 10(3) Impacts, Required Compensatory Mitigation, and Proposed Mitigation

Location Proposed Impacts Total Compensatory Functional Mitigation Proposed Mitigation

North Abutment 0.13 acre (0.05 hectare) 0.076 acre (0.06 hectare) 0.28 acre (0.11 hectare) South Abutment 0.16 acre (0.06 hectare) 0.061 acre (0.05 hectare) 0.26 acre (0.11 hectare)

TOTAL 0.29 acre (0.12 hectare) 0.14 acre (0.055 hectare) 0.54 acre (0.22 hectare)

Project FOPU 10(3) 2-8 Final

3.0 MITIGATION SITE SELECTION AND JUSTIFICATION

3.1 Selecting the Proposed Sites

The mitigation sites were selected due to several important factors:

1. The sites are owned by the NPS.

2. The sites are adjacent to an existing and historically stable tidal marsh.

3. The sites were historically tidal marsh prior to construction of the existing Fort Pulaski

Bridge.

4. The sites are located in an area where hydrology is present to support tidal marsh vegetation.

5. The sites are located away from present-day activities on Cockspur Island and NPS and

U.S. Coast Guard operations.

6. The sites can be preserved in perpetuity.

3.2 Likelihood of Success

The practicability of restoring tidal marsh at the Project FOPU 10(3) sites is high since 1) the soils and hydrology to support and maintain tidal marsh plant community structure and composition is already present; 2) the adjacent tidal marsh provides many valuable wetland functions, including wave-energy attenuation, biogeochemical cycling, habitat for nekton and wildlife, and presently supports tidal marsh plant community structure and composition; and 3) the sites were historically tidal marsh prior to construction of the existing bridge.

Project FOPU 10(3) 3-1 Final

Project FOPU 10(3) 4-1 Final

4.0 MITIGATION WORK PLAN

4.1 Location

As previously described, restoration of approximately 0.54 acre (0.22 hectare) of tidal marsh would occur on NPS property at Fort Pulaski (see Appendix A: Figures 2-1 and 2-2).

4.2 Construction Plan

After the existing bridge, road fill material, and existing riprap to the low water line are removed, the northern and southern roadway approach areas, totaling approximately 0.54 acre (0.22 hectare), would be restored to tidal marsh (Appendix A: Figures 4-1 through 4-3). The existing and adjacent tidal marsh wetlands would be surveyed using standard survey industry equipment and methodologies prior to commencing work within the proposed wetland mitigation areas, and each mitigation area would be graded to match the elevation of the adjacent existing wetlands (Appendix A: Figures 4-1 through 4-3). Specifically, high and low spots (5 total) in the adjacent smooth cordgrass-dominated low marsh would be flagged within each of the impact and wetland mitigation areas. The FHWA would invite resource agencies to observe the flagging. Elevations of the flagged locations would then be surveyed, and the mean elevation would be used to determine the target elevation of each wetland mitigation area.

The mitigation sites would be staked, and the expected grades would be established. Road fill material and existing riprap to the low water line would be removed by an excavator at the northern and southern roadway approach areas (Appendix A: Figure 4-1 through 4-3).

Biodegradable coconut fiber matting would be placed on the graded mitigation areas for erosion control and to stabilize the site. Oyster shell bags would be placed along the shoreline between the mean low water and mean high water elevations to provide shoreline stabilization and protection. Floating turbidity curtains would also be installed between the construction areas and the South Channel of the Savannah River for sediment erosion control. During construction, only the area that can be stabilized at the end of the day will be disturbed unless an approved erosion and sediment control measure is installed. Any loose sediment would be stabilized quickly to prevent sediment runoff into the existing adjacent marsh. All excavated fill material would be hauled to an offsite upland disposal site.

4.3 Planned Mitigation Site Conditions

The existing roadway approach areas would be restored to E2EM1N wetlands to replace functions lost at the impact sites. The compensation areas are directly adjacent to the surrounding E2EM1N wetlands and the South Channel of the Savannah River (see Appendix A:

Figures 1-3 and 1-4); therefore, hydrology to support the compensation wetlands is already present.

The compensation wetlands would blend into the surrounding E2EM1N wetlands. The existing soils have been compacted. Compaction of the soil will be minimized during operations by utilizing equipment having low unit pressure ground contact and by limiting repeat passes over the same areas. In order to minimize the impacts of soil compaction, the area may be over-excavated and backfilled with topsoil if necessary.

Prior to construction at the 0.29-acre (0.12-hectare) impact sites, existing vegetation, which is primarily a monoculture of smooth cordgrass, would be excavated as 1-foot by 1-foot (0.3-meter by 0.3-meter) square clumps, or plugs. The plugs would be vegetation and root-soil masses dug from the impact site, consisting of multiple stems of intact live aboveground vegetation and live roots and rhizomes excavated to depth of approximately 12 to 18 inches (30 to 45 centimeters) (Photograph 4-1). Once excavated, plugs would be transplanted into containers with an organic soil mixture (2:1 topsoil:sand ratio), transported to an off-site location, and kept irrigated with water until placement into the mitigation sites following obliteration of the existing bridge and associated road fill and riprap and site preparation. All smooth cordgrass sods would be installed at the site on 2-foot (0.6-meter) centers (Appendix A: Figure 4-1 through 4-3).

As necessary, additional smooth cordgrass plugs would be obtained in coordination with Georgia Department of Natural Resources, Coastal Resources Division (CRD), from a nursery source as close to the restoration site as possible to fill in gaps between the sods and to help revegetate the approximately 0.54-acre (0.22-hectare) tidal marsh wetland mitigation areas. All plugs obtained from the CRD and planted at the site would be installed using no more than 0.5-foot (0.15-meter) centers.

4.4 Verification of Mitigation Site Conditions

After construction is completed, the surface of the restored marsh areas would be surveyed to determine their elevations relative to existing marsh habitats and to confirm appropriate planting elevations have been established. Elevation data would be collected using one or multiple standard survey approaches, including standard visual leveling, digital bar code leveling, and/or real time kinematic (RTK) GPS. Ground shots would be taken at least every 25 feet within the restored marsh areas. Once the surface elevations are checked and soils stabilized post-excavation and allowed to acclimate to exposure to air and surface water exchange, the restored marsh surface would be planted.

In addition, a letter report and one copy of as-built drawings, including GIS data, will be submitted to the USACE and other regulatory agencies following completion of the mitigation sites. The report will include:

� Date(s) all compensatory mitigation construction activities were completed;

� Schedule for future mitigation monitoring, implementation, and reporting pursuant to final, USACE-approved mitigation plan;

Photograph 4-1. Smooth cordgrass multi-stem plug removal (excavation) from an existing tidal marsh

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� Summary of compliance status with each special condition of the associated USACE permit or verification (including any noncompliance previously having occurred or currently occurring and corrective actions taken to achieve compliance);

� Color photographs of the wetland habitats constructed at the compensatory mitigation site and color photographs of the areas before compensatory mitigation; and

� One copy of the final as-built drawings as described below.

The final as-built drawings will be provided on the original construction drawings and will indicate the following features:

� Extent of re-established, established, and enhanced areas (in plan view);

� Extent of both cut and fill;

� Spot elevations to accurately characterize the finished surfaces, including high and low points;

� As-built cross sections;

� Location of any permanent markers (e.g., identification stakes, photodocumentation stations, elevation benchmarks);

� Planted areas; and � Other pertinent features.

Any changes from the original construction drawings will be indicated in indelible red ink. The final as-built drawings will be submitted to the USACE and other appropriate resource agencies within 6 weeks of construction completion at the mitigation sites.

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Project FOPU 10(3) 5-1 Final

5.0 PERFORMANCE STANDARDS AND MONITORING REQUIREMENTS

5.1 Performance Standards

The FHWA will utilize the applicable performance standards and success criteria, as outlined in the Mitigation Metrics and Performance Standards (Appendix 10) of the USACE, Savanah District’s Draft Guidelines to Establish and Operate Mitigation Banks in Georgia (USACE 2011), for mitigation site monitoring and to document annual and final success.

5.2 Reference Sites

Two recommended reference sites (Figure 4-4) within the tidal marsh wetlands adjacent to the mitigation areas have been identified for use in assessing the success of the wetland mitigation overtime. The reference sites were chosen because they are the most similar wetlands in the vicinity to those wetlands impacted. Vegetation consists primarily of smooth cordgrass, a simple network of one to two tidal channels is present, and little wetland disturbance has occurred.

Likewise, the reference sites are located on NPS property and can be accessed through existing NPS lands, trails, or roadways. Monitoring transects, vegetation plots, and boreholes will be established within each reference site concurrent with monitoring site setup following the same methods that are used within each mitigation area.

5.3 Success Criteria

5.3.1 Hydrology

Restoration of hydrology and hydrological functions at the mitigation sites will be considered successful if the following milestones are reached:

� Hydrology will be deemed successful if the hydrologic function matches the reference site for parameters including degree, duration, and periodicity of inundation annually.

� The restored marsh provides habitat utilized annually by the same nekton and tidal marsh-dependent wildlife as the reference marsh.

5.3.2 Vegetation

The restoration efforts for vegetation will be considered successful and complete if, at the end of the 5-year monitoring period, the stem density of smooth cordgrass within monitoring plots at each mitigation site is 80 percent of that with the reference site. Stem densities (live, standing-dead, and shoot) and stem heights for smooth cordgrass and other native tidal marsh species will be collected within 5.3-square foot (0.25-square meter) quadrats placed along two sampling transects, that run perpendicular to the river and intersect with the shoreline, within each mitigation site.

5.4 Comparison of Functions

The compensation wetlands will be monitored and maintained to ensure that they provide the same level of functions as the impacted wetlands. To monitor achievement toward 1:1 tidal marsh functional replacement, the HGM Approach will be used annually for a period of 5 years to compare wave energy attenuation, biogeochemical cycling, nekton utilization potential, habitat for tidal marsh-dependent wildlife, and maintain characteristic plant community structure and composition functions of the restored tidal marsh to those of the reference marsh.

5.5 Monitoring Requirements

The monitoring criteria will be based on restoration of tidal hydrology through excavation and exposure of the historical marsh surface, restoration of tidal marsh vegetation (e.g., predominantly smooth cordgrass), restoration of water quality, and restoration of aquatic biology utilization. Elevation is a critical factor determining tidal marsh plant community structure and function. Since elevation and tidal hydrology determine the pattern, frequency and duration of marsh inundation, elevation will be monitored for change over time. Based on time and budget availability, elevation data will be collected using one or multiple standard approaches, including standard visual leveling, digital bar code leveling, and/or RTK GPS. Elevations will be tied to the North American Vertical Datum 1988 (NAVD88).

Hydrology will be monitored directly on-site for one tidal cycle annually using a combination of boreholes and staff gauges, as approved by the NPS. Boreholes within the reference and mitigation wetlands will be used to measure water levels. After digging the holes, sufficient time will be allowed for water to infiltrate and stabilize at the water-table level. The required time will vary depending on site conditions, such as soil texture. Once stabilized, the water level within each borehole will be recorded. For many wetland mitigation projects, particularly those similar to this one in which the area is small, there is good access, and travel to the sites is not problematic, water levels using this technique has proven to be a suitable and less labor-intensive method than installing monitoring wells (Minnesota Board of Water & Soil Resources 2013).

Staff gauges are another direct, on-site way to track water levels in wetlands (Minnesota Board of Water & Soil Resources 2013). Following typical monitoring protocols, and upon approval from the NPS, commercially available staff gauges will be purchased and installed at the reference and mitigation wetland sites. Staff gauges will be attached to a fencepost that has been driven into the marsh surface, or will be attached to some other stable structure. The staff gauges will be used to quickly and easily record the water level with the reference and mitigation wetlands during annual monitoring.

Hydric soil conditions if not already present are expected to develop rapidly once the historic tidal marsh is re-exposed, and qualitative measures of inundation (e.g., flooded, wet, moist, dry) at the restored tidal marsh and reference site will be recorded to monitor hydrology. Estimates of water chemistry parameters, including dissolved oxygen, temperature, and salinity, will also be recorded using a simple handheld water quality sonde such as a YSI® Pro2030 Dissolved Oxygen, Conductivity, and Salinity Instrument.

Project FOPU 10(3) 5-2 Final

Tidal marsh vegetation stem densities (live, standing-dead, and shoot) and stem heights for smooth cordgrass and other native tidal marsh species will be collected within 5.3-ft2 (0.25-m2) quadrants randomly placed at 20 sampling plots within each mitigation site. Any non-native or woody marsh species within the mitigation sites will also be noted during monitoring efforts.

Annual reports will be prepared in accordance with Regulatory Guidance Letter No. 08-03 dated October 10, 2008 (USACE 2008), and will be submitted after each year of monitoring, within 30 days of field data collection. At a minimum, the annual monitoring report will include the following:

� Reference regulatory permits authorizing project activity � A summary of restoration efforts � Figures, maps, and photographs of the restoration area � Estimates of stem density and height for herbaceous vegetation � Estimates of species composition of herbaceous vegetation � Observations of invasive species and corrective measure to control the species � A summary of overall restoration site conditions, including hydrologic conditions

Should all performance criteria for Year 5 be met before Year 5, the FHWA will request approval from the USACE to discontinue monitoring and close the mitigation project and transition the mitigation area to long-term management. In the case that only one or several parameters meet the performance criteria for Year 5 ahead of schedule, the FHWA will continue monitoring all the parameters for one additional year or until the final year of monitoring until all the performance criteria are met. Once all Year 5 performance criteria are met, the FHWA will discontinue monitoring and will request approval from the USACE to close the mitigation project and transition the mitigation area to long-term management.

If the mitigation sites have not met the performance criteria by the end of Year 5, and the criteria are considered accurate and reasonable, maintenance and monitoring obligations would continue until performance criteria are achieved or until alternative contingency measures can be negotiated with regulatory agencies. The FHWA understands that failure of any significant portion of the mitigation sites may result in a requirement to replace that portion of the sites and/or extend the monitoring and maintenance period until all success standards are met.

Project FOPU 10(3) 5-3 Final

6.0 SITE PROTECTION AND MAINTENANCE

6.1 Responsible Parties

Upon completion of Project FOPU 10(3) and associated mitigation monitoring (i.e., at end of Year 5), the NPS will be responsible for all site protection and maintenance activities.

6.2 Protective Measures

The mitigation sites are managed under Federal ownership by the NPS.