07-Permit_Attachment_Turbidity_and_Water_Quality_Monitoring_Plan_NPS_05-2019.pdf

TURBIDITY MANAGEMENT AND WATER QUALITY

MONITORING PLAN FOR THE

REPAIR AND REPLACEMENT OF THE WHARF

WITHIN THE CHRISTIANSTED NATIONAL HISTORIC SITE

CHRISTIANSTED, U.S. VIRGIN ISLANDS

INTRODUCTION

The National Park Service (NPS) proposes to replace the existing wharf bulkhead along the Christiansted National Historic Site (Christiansted NHS or park) waterfront. Christiansted NHS is located in the historic town of Christiansted on the island of St. Croix, US Virgin Islands (Figure 1). The goal of the proposed action is to prevent damage from more frequent and more powerful seasonal hurricanes and to mitigate and remediate the effects of historic and continuing storm damage to the Christiansted NHS waterfront landscape, associated historic buildings, visitor use, and marine vessel operations. The existing wharf bulkhead structure, which had protected the historic waterfront from wind-driven wave action and storm damage, has deteriorated considerably. Local failures in the bulkhead have rendered the artificial structure ineffective, unsound, and unsafe for vehicular or marine vessel use. Water movement is expected to continue to undermine the bulkhead, causing erosion of the shoreline. These issues, in conjunction with projected sea-level rise, would continue to exacerbate the deterioration of the existing bulkhead and further threaten the park historic landscape and cultural resources. The proposed action would replace the existing bulkhead by encapsulating it; new steel sheet piling or new cast-in-place concrete would be installed seaward of the existing alignment. The proposed action would also include a new concrete cap (at a similar height to the existing bulkhead), new concrete fascia to protect the “splash zone,” new mooring cleats, a new fendering system, and rehabilitation of the existing concrete apron (the sidewalk adjacent to the bulkhead).

Figure 1: Project Location

1.2 Project Setting

The existing wharf spans the northern shoreline of the Christiansted National Historic Site within the historic town of Christiansted. The area is a historic harbor and has been altered from its natural state. The benthic habitat at the project site includes submerged aquatic vegetation, and manmade structures and small-localized areas of hardbottom covered by thick sediment and macroalgae over rubble and cobble. The submerged aquatic vegetation with in the project areas is dominated Halophila stipulacea, an exotic invasive seagrass. Turtle grass (Thalassia testudinum) was found in very shallow water (less than 6 feet deep) in the easternmost portion of the study area. The bulkhead is colonized by 18 species of stony corals include the ESA Orbicella spp.

Eight of the 18 species of stony corals identified on the wharf bulkhead were also documented on the bottomlands within the project area (mustard hill coral, finger coral, massive starlet coral, lesser starlet coral, golf ball coral, blushing star coral, mountainous star coral, and symmetrical brain coral); only one colony of the federally listed mountainous star coral was noted.

The Environmental Protection Agency’s (EPA), Virgin Islands Ambient Water Quality Monitoring Program (VIAWQMP), monitoring site 42 is located at the western end of the project area as shown in Figure 2. Data from the last two years of sampling data from Station 42 is presented in Table 1. In 2017 the site had elevated Enterococci bacteria during to samplings, but there have no be any incidence of elevated Enterococci since that time. Turbidity at the site has remained low during all sample with the highest recorded turbidity of 0.7 NTU.

Figure 2: Location of VIAWQMP Sample Site No. 42.

Table 1: Data from VIAWQMP Sample Site No. 42.

1.3 Potential Impacts

The NPS proposes to replace the existing 500 linear feet of sheet pile bulkhead at the western end of the wharf. The steel sheet piles will be driven 24 inches seaward of existing sheet piles and a new concrete pile cap and fascia will be poured. Clean granular fill will be placed behind the sheet pile wall. The new pile cap will be a cantilever design with no-tie backs. The new structure will be the same elevation as the existing structure. Once the new pile cap is installed, a new protective concrete coating will be poured on the existing apron (sidewalk). The new concrete fascia will be 4ft in width and will extend below mean low water. The eastern 200 linear feet of the wharf, which is adjacent to the fort, is a concrete bulkhead. A new fascia extending 2’8” from the existing face of the bulkhead.

During construction, the project has the potential to impact water quality due to the suspension of particulate matter through vessels movements (prop wash), pile driving, the placement and removal of barge spuds, and framing activities. If pile socketing is required, this could increase turbidity due the creation of fines (rockflour) as the rock is cut. The project also has the potential to introduce fines from filling and dewatering behind the new sheet piles and the pouring of concrete below the waterline. Surface water runoff over exposed soils could also affect water quality. During construction, Best Management Practices will be implemented to minimize these impacts.

In any marine construction, the potential for negative impacts to marine life and degradation of water quality exist. When sediments are suspended in the water column through dredging or deposition of fill, these suspended sediments add to the turbidity of the water. The lowering of the transparency of seawater can greatly affect sessile marine organisms that rely on the transmission of the light for their existence. Settling sediments can also smother coral colonies and prevent larval sediment of reef organisms. Through careful planning and monitoring, such potential

Date mm/dd/yyyy

Station

ID

Time (hh:mm)

Total Depth

(m) xx.x

Temp (°C) xx.xx

Salinity (ppt) xx.xx

DO

(mg/L) xx.xx pH (s.u.)

xx.xx

Turbidity

(NTU)

xx.x

Secchi (m) xx.x

Enterococci #/100ml

Surface 0.5 27.0 35.04 6.18 7.97 0.15 Bottom 2.6 27.1 35.04 5.98 7.98 0.13 Surface 0.5 29.34 34.66 6.02 8.03 0.4 Bottom 2.5 29.23 34.69 6.04 8.04 0.4 Surface 0.5 27.9 34.24 6.86 8.12 0.26 Bottom 2.6 27.9 34.24 6.88 8.12 0.18 Surface 0.5 26.7 35.49 6.99 7.93 0.49 Bottom 3.1 26.7 35.50 6.94 7.93 0.44 Surface 0.5 27.20 35.40 6.21 8.28 0.3 Bottom 2.6 27.19 35.30 6.19 8.29 0.4 Surface 0.5 28.84 35.27 5.33 8.33 0.4 Bottom 3.2 28.71 35.27 5.26 8.31 0.4

10:28 Surface 0.5 28.01 35.30 6.90 7.75 0.7 Bottom 3.4 27.99 35.31 6.84 7.74 0.5

12:33 Surface 0.5 26.29 35.48 7.01 8.18 0.3 Bottom 3.2 26.26 35.49 7.03 8.19 0.1 Surface 0.5 26.77 35.81 6.16 8.40 0.1 Bottom 3.2 26.73 35.83 5.96 8.40 0.0

3.7 3.7

STC-42

12:36

3.0 3.0

STC-42 12:00

3.6 3.6

>10

STC-42 12:01

3.1 3.1

STC-42 3.9 3.9

STC-42

8:29

5/30/2018 >10

>10

>10

STC-42

11:00

3.1 0.6 965/11/2017

7/18/2017

12/12/2017

1/23/2018

3.0

>10

STC-42 11:09 3.1 3.1

8/7/2018

11/13/2018

2/19/2019 STC-42 3.7 3.7 >10

>10STC-42 11:35 3.7

5/14/2019

Sample Depth

(m) xx.x impacts can be minimized and abated. The purpose of this monitoring plan is to ensure that potential impacts to aquatic species are minimized to the greatest extent possible.

1.4 Best Management Practices

In order to ensure that water quality is maintained this water quality-monitoring program will be implemented during all in-water work pile driving, pre-drilling, filling and concrete pours. This plan will monitor turbidity and look at the effectiveness of the sedimentation control. If any degradation of water quality is detected immediate measures will be taken to abate the impacts.

Proper length (approximately 1 ft. from seafloor) turbidity barriers will be installed around all areas of in-water work. Turbidity curtains will be installed with a minimum of 2 meters between them. The curtains will be attached to the bulkhead and may be held offshore by carefully placed traditional anchors or screw anchors. Divers will assist in the placement of all anchors to minimize impact. The curtains will be monitored on a daily basis and if at any time deficiencies or damage is noted it will be repaired immediately. A small workboat will be kept at the bulkhead so the curtains can be serviced quickly in the event of need.

On land silt, fencing will be placed around all areas of earth disturbance to prevent sediment laden runoff from being carried into the sea. Silt fencing will be monitored on a daily basis and repair when and if damage or deficiencies are noted.

1.5 Project Permits and Approval Requirements

The NPS has requested a Coastal Consistency Determination from the U.S. Virgin Islands Department of Planning and Natural Resources Coastal Zone Management Division. The project is designed to meet the Goals and Policies of the Coastal Zone Management Act. The NPS prepared Environmental Assessment (EA) in accordance with the National Environmental Policy Act of 1969, as amended (NEPA), and implementing regulations, 40 Code of Federal Regulations (CFR) Parts 1500–1508, NPS Director’s Order 12: Conservation Planning, Environmental Impact Analysis, and Decision-making (NPS 2011) and the accompanying handbook (NPS 2015a).

In accordance with Section 7 of the Endangered Species Act (ESA) and the Marine Mammal Protection Act, the NPS is consulting with the National Marine Fisheries Service (NMFS) Protected Resources Division (PRD). In February 2019, the NMFS concurred with the NPS’s determination that the proposed coral relocation activities fall within the scope of Programmatic Biological Opinion on Threatened Caribbean Coral Research, Restoration and Relocation (PBO), initiated on October 18, 2016; and that any activities that fall within the scope of the PBO would not cause jeopardy to lobed star coral species complex, Elkhorn coral, and staghorn coral.

In accordance with Section 7 of the Endangered Species Act (ESA) and the provisions of the Magnuson- Stevens Fishery Conservation and Management Act (16 USC Section 1801 et seq.), the NPS is consulting with the NMFS Habitat Conservation Division and has submitted an Essential Fish Habitat Assessment with the EA.

In March 2019, the U.S. Fish and Wildlife Service concurred with the NPS determination of may affect, but not likely to adversely affect Antillean manatee, Green, Hawksbill, Leatherback and Loggerhead sea turtle species based on the nature of the project, the habitat characteristics of the project area, and the mitigation measures that would be employed.

This Turbidity Management and Water Quality Monitoring Plan address the means and methods the NPS will undertake to protect aquatic species under the jurisdiction of USFWS, and NOAA/NMFS, and the

USVI DPNR.

2.0 WATER QUALITY MONITORING

2.1 Monitoring Plan Design

The monitoring plan has been designed to help ensure that existing water quality is maintained and not degraded by the reconstruction of the wharf. The plan has been designed to address all potential construction activities that effect water quality or create bottom disturbances that will in turn affect water quality. The monitoring design is based on the turbidity control, which will be implement.

2.2 Monitoring Objectives

The objective of the monitoring plan is to ensure that turbidity control is properly implemented and to assess where the implemented methods are effectively controlling water quality. If the implemented control is not adequately controlling turbidity, the monitor plan lays out additional steps that will be taken to minimize water quality degradation.

2.3 Monitoring Parameters

The proposed bulkhead reconstruction has the potential to impact water quality through the suspension of bottom sediments during pile driving, bulkhead framing, offshore vessel movement, and anchoring or spudding if the project is built from a barge. The project has the potential to affect water quality through de-watering, filling and concrete pouring. These activities will affect the turbidity within the water column. Therefore, turbidity and water clarity are the parameters that will potentially be affected and will be monitored throughout construction of the project. Total suspended solid may also be impacted however; this parameter requires laboratory analysis and cannot provide real-time monitoring. Turbidity will be measured with an EPA approved calibrated field nephelometer as Nephelometric Turbidity Units (NTU). Secchi disc readings will also be made as a measurement of water clarity.

2.4 Monitoring Sites

Water quality samples will be taken 5m outside the turbidity barriers immediately offshore of where the current work is ongoing. Three sites will be taken approximately 10m apart with the central point immediately off the area of work. The monitor will also take samples in any plume that is noted coming through the turbidity barriers. The monitoring samples will be placed in the areas most likely to be impacted by the project. Control sites will be established in areas which should be exposed by the same ambient conditions but should not be impacted by the projects activities. Two control sites will be established one to the east and one to the west.

Samples will be taken 1 meter below the surface and will be analyzed by either a Hach 2100 Turbidity meter or an YSI Multi-meter or other equivalent approved EPA meter. The meter must be calibrated daily prior to sampling.

Prior to the start of construction, a baseline of water quality conditions will be established. In order to assess and compare water quality conditions at the site prior to any work, three samples will be taken evenly spread along the length to the project area. This data along with the VIAWQMP data will be used to determine the pre-construction water quality.

Figure 3: Water Quality Monitoring Locations. (Locations shown are sample baseline locations.

During construction, samples will be taken around area of work 5m outside turbidity barriers.)

2.5 Monitoring Frequency

During construction, sampling will occur a minimum of twice a day with samples spaced at least 4 hours apart. The monitor will also sample anytime a plume is noted escaping the turbidity barriers.

2.6 Monitoring Schedule

Prior to the start of construction, a baseline of water quality conditions will be established. The five sampling locations shown in Figure 3, will be sampled on a weekly basis for a period of 2 months (8 events) prior to the start of construction. Weather and sea conditions will be recorded for each sampling time. The data from the baseline will be used to establish the existing conditions so that this may be used to compare with data collected during the construction project to help assess whether readings are a result of the construction project or are due to ambient conditions.

During construction, sampling will occur anytime in-water work is being undertaken, during all pile driving, all framing, all de-watering, all filling and all concrete pours.

3.0 DURING CONSTRUCTION

3.1 Turbidity Control

During all in-water work, which includes, pile driving, pre-drilling filling, framing and concrete pouring, a double set of proper length (1ft from seafloor) turbidity barriers must be installed.

The curtains must be maintained throughout all work. The contractor must have additional barriers so that they are available for deployment if the barriers become damage or if additional barriers are necessary to control turbidity. Silt fencing must be properly installed in all areas of upland soil disturbance and maintained until such time that the area has become revegetated or paved.

3.2 Sampling

Three (3) samples will be taken around the area of in-water work; these samples will be taken in a radial pattern around the area of work at a distance of 5meters outside the turbidity booms and spaced approximately 10m apart with the center sample taken immediately off the area of work.

Samples will be taken 1 meter below the surface and will be analyzed by either a Hach 2100 Turbidity meter or a YSI Multi-meter. Samples will be taken minimum of twice a day.

The two control samples will be utilized to determine whether elevated turbidity is a function of the project or due to ambient conditions. As per the Virgin Islands Code, visual depth visibility readings (Secchi disk measurements) should not fall below 1 meter and turbidity may not exceed three NTU in Class C waters. The water quality was not seen to exceed that value over the last two years of ambient monitoring data (VIAWQMP).

All results will be recorded on field sheets (Appendix 1). Wind speed and direction, wave height and direction, and rainfall will be recorded on the field at the time of sampling. GPS of the sampling points will be included on the field sheets. The monitor will take pictures as necessary as a part of the monitoring to document activities at the site and to document any incidents, which may occur.

3.3 Corrective Actions

During construction if the water samples show NTU readings in excess of the allowable limits and if it is determined that the elevated turbidity is the result of the project, the source of the problem will be identified, and methods worked out to reduce the turbidity. If elevated readings are encountered, the construction will stop and any deficiencies in the deployed turbidity controls will need to be corrected. Work may resume once turbidity has fallen to allowable levels. If there are no deficiencies in the deployed turbidity control, additional curtains will need to be deployed around the area of work. If additional barriers are not effective the work may need to be slowed (i.e. – dewatering or fill behind the bulkhead slowed.) In-water work will have to stop until turbidities reach allowable levels before resuming. If the additional measures cannot be deployed which are adequate to control turbidity, then work will have to be shut down every time readings become elevated over acceptable ranges and will only be able to resume once they have fallen back into acceptable ranges.

4.0 REPORTING

4.1 Elevated Readings

During construction if the water samples show NTU readings in excess of the allowable limits, DPNR, DEP, NPS, COE and NMFS will be notified by email. The baseline samples will be utilized to determine if an increase in turbidity or suspended solids is a result of natural phenomena or if the monitoring sample is elevated above the ambient background because of the project. If it is determined that the elevated turbidity is the result of the project, the source of the problem will be identified, and methods worked out to reduce the turbidity. The construction contractor must always have someone at the construction site who has the authority to implement sediment control devices, so that the monitor can work with them to stop construction and implement additional turbidity control.

If elevated readings are encountered, the construction will stop and if any deficiencies in the deployed turbidity controls are encountered, they will need to be corrected. Work may resume once turbidity has fallen to allowable levels. If there are no deficiencies in the deployed turbidity control, additional curtains will need to be deployed or work may need to be slowed. In-water work will have to stop until turbidities reach allowable levels before resuming. If the additional measures cannot be deployed which are adequate to control turbidity, then work will have to be shut down every time readings become elevated over acceptable ranges and will only be able to resume once they have fallen back into acceptable ranges.

4.2 Weekly Reports

A weekly report will be provided to DPNR, DEP, NPS, COE and NMFS by email detailing the week’s events and the results of all monitoring activities. The reports will include a summary of all actions taken and the results of those actions. The reports will include photographs of the activities, which were undertaken during the week, as well as photographs of any incidents, which occurred.

REFERENCES:

National Park Service (NPS)

2011 Directors Order 12. Conservation Planning, Environmental Impact Analysis, and Decision Making. Approved October 5, 2011.

2015a National Park Service NEPA Handbook. September 2015.

Water Quality Standards for Waters of the Virgin Islands, Title 12, Chapter 7, Amendments to Subchapter 186, August 28, 2015 p26.

Calibration:

Sea Conditions Wave Height: Wave Direction: Wind Speed: Wind Direction: Rainfall:

Construction Activities:

Morning Sampling Lat/Long Turbidity NTU Secchi Depth

Location

Control E

Control W

Actions (if necessary):

Construction Activities:

Afternoon Sampling Lat/Long Turbidity NTU Secchi Depth

Location

Control E

Control W

Actions (if necessary):

Signature of Sampler:

Name of Sampler:

NPS

REPLACMENT OF THE NPS WHARF

Date:

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