Appendix_1b_NPDES_SWPPP.pdf

Stormwater Pollution Prevention Plan For the Construction General Permit (SCR100000)

Comprehensive Stormwater Pollution Prevention Plan (C-SWPPP) For

Construction Activities:

Project/Site Name:

FW ACBA 100(1)

Project Address/Location:

Ace Basin National Wildlife Refuge

Charleston County, SC Grove Road and Perimeter Road

843-889-3084 Fax 843-889-3282 / acebasin@fws.gov

Primary Permittee:

Federal Highway Administration

Permittee/Owner Contact:

Kevin Rose

21400 Ridgetop Circle Sterling, VA 20166

571-434-1541 Fax 571-434-1577/ kevin.rose@dot.gov

SWPPP Preparer:

Federal Highway Administration Kevin Rose

21400 Ridgetop Circle Sterling, VA 20166

571-434-1541

Fax 571-434-1577/ kevin.rose@dot.gov

Day-to-Day Operator:

(Leave Blank if not known.)

C-SWPPP Preparation Date:

12 / 16 / 2015

Modification Dates:

Modification I: __ __ / __ __ / __ __ __ __ Modification II: __ __ / __ __ / __ __ __ __

Table of Contents

Section 1 PROJECT OVERVIEW

1.1 Narrative

1.2 Stormwater Management and Sediment Control

1.3 Sequence of Construction

1.4 Non-Numeric Effluent Limits

1.5 Buffer Zone Management

1.6 Certification Statement

Section 2 SITE FEATURES AND SENSITIVE AREAS

2.1 Sources of Pollution

2.2 Surface Waters

2.3 Impairments And TMDLs

2.4 Critical Areas (Coastal Zone Only)

Section 3 COMPLIANCE REQUIREMENTS

3.1 SWPPP Availability

3.2 Pre-Construction Conferences

3.3 Inspection Requirements

3.4 Maintenance Policies

3.5 Record Keeping

3.6 Final Stabilization

Appendices REFERENCE MATERIAL

Appendix A - Site Maps Appendix B - Drainage Maps Appendix C - Additional Approvals/Certifications Appendix D - Engineering Report (C-SWPPP* Only) Appendix E - Inspection Log and Reports (OS-SWPPP** Only) Appendix F - Rainfall Records (OS-SWPPP** Only) Appendix G - Additional Site Logs and Records (OS-SWPPP** Only) Appendix H - Construction General Permit (CGP) - SCR100000

*C-SWPPP is acronym for Comprehensive Storm Water Pollution Prevention Plan

**OS-SWPPP is acronym for On-Site Storm Water Pollution Prevention Plan

Section 1 PROJECT OVERVIEW

1.1 Narrative (CGP Section 3.2.1)

Construction Activities and BMP Summary

The project consists of the rehabilitation of a 1.96 mile segment of Mainline Grove Road and Perimeter Road within the Ace basin National Wildlife Refuge in Charleston County, South Carolina. The work includes aggregate resurfacing of the road, subexcavation and base repairs, rehabilitation of 0.22 miles of earthen causeway across intertidal marsh, pipe culvert replacement and other miscellaneous work.

Perimeter control BMPs will be installed prior to any construction activities in the area.

The primary sediment control measured that will be installed in this project is wire-backed silt fence around the work areas. Another sediment control measured that will be installed is a construction exit to preventing tracking sediment outside the project limits.

Once final stabilization of the project is achieved, the silt fence and other temporary erosion and sediment control measures will be removed from the project.

The construction activities at this site will be implemented in 3 distinct Erosion Prevention and Sediment Control Phases. The first phase includes the establishment of perimeter controls and the construction entrance. The second phase includes the bulk of the construction activities, the implementation of internal stormwater management BMPs, and temporary erosion control measures. The final phase, Phase 3, includes the final stabilization of the site and removal of temporary erosion and sediment control measures.

The project is estimated to start March, 2016 with a duration of 50 days.

Pre-Development Conditions

There are currently seven culverts and one rice trunk wooden water control structure within the project limits. The current condition of these structures is provided below.

Grove Road – there is currently a 49’ long 24” reinforced concrete pipe (RCP) culvert that drains from the north side of the road towards the south side at station 112+37.

Also, there is a 21’ long 15” corrugated metal pipe (CMP) that drains east to west on a driveway connecting to Grove Road between stations 116+00 and 116+40 on the south side of the road.

Both pipes are in a detrimental condition and require replacement. Also, the diameter of the CMP should be increased to handle the volume of water in the area.

In addition, the ditch between stations 115+35 and 116+50 at the south of the road is not providing adequate drainage.

Perimeter Road – There are several pipe culverts in this area that are in a detrimental condition or their diameter should be increased to accommodate the flow of water in the area.

At station 131+13, there is a 32’ long 18” diameter PVC pipe in which water flows from the south side of the road towards the north side, whose diameter should be increased to handle the volume of water in the area.

At stations 155+62 and 155+63, there are two side by side 31’ long 24” diameter CMP culverts in detrimental condition in which water flow from the south side to the north side of the roadway.

Between station 155+88 and 156+00, there is a 46’ long 24” diameter CMP in detrimental condition in which water flows from the south east side of an intersection to the North-West side.

At station 171+00, there is a Rice Trunk Wooden Water Control Structure.

At station 193+39, there is a 20’ long 18” diameter PVC pipe in which water flows from the south side of the road to its north side. The diameter of this pipe should be increased to handle the volume of water that flows in the area.

At station 198+01, there is a 20’ long 18” diameter PVC pipe in which water flows from the south side of the road to its north side. The diameter of this pipe should be increased to handle the volume of water that flows in the area.

There are several ditches along Perimeter Road that are not providing adequate drainage.

Post-Development Conditions

There are seven culverts that are being replaced to improve on site drainage.

Grove Road – The existing 24” diameter RCP at station 112+37 will be replaced in-kind.

The existing 15” diameter CMP between stations 116+00 and 116+40 will be upgraded to a 24” diameter RCP.

Perimeter Road – The existing 18” diameter PVC culvert at station 131+09 will be upgraded to a 24” diameter RCP.

The two side by side 24” diameter CMP culverts at stations 155+62 and 155+63 will be replaced with two 24” diameter RCP.

The 24” diameter CMP between station 155+88 and 156+00 will be replaced with a 24” diameter RCP.

The 18” diameter PVC pipe at station 193+39 will be upgraded to a 24” diameter RCP culvert.

The 18” diameter PVC pipe at station 198+01 will be upgraded to a 24” RCP culvert.

Ditches having inadequate drainage will be reconditioned to provide positive drainage as necessary.

Table 1.1-A: Pre/Post Peak Discharges

Summary of Pre/Post Peak Discharges

Outfall 112+37 Outfall 131+09

Pre Post Pre Post

2-YR 92.52 92.52 2-YR 93.67 93.67

10-YR 181.67 181.67 10-YR 184.23 184.23

100-YR 335.67 335.67 100-YR 340.37 340.37

Outfall 155+62 Outfall 171+00

Pre Post Pre Post

2-YR 70.15 70.15 2-YR 165.19 165.19

10-YR 133.79 133.79 10-YR 306.40 306.40

100-YR 241.59 241.59 100-YR 544.09 544.09

Outfall 198+00

Pre Post

2-YR 7.63 7.63

10-YR 15.18 15.18

100-YR 28.24 28.24

Flooding Issues

The existing roadway, culverts, and ditches are in detrimental shape which is causing flooding of the roadway. The existing roadway has deteriorated to a state that is causing poor drainage. The culverts within the project limits are either in poor condition or undersized. Several ditches along the roadway are not allowing for proper drainage.

According to FEMA flood maps (Appendix A) the entire project is within a flood plain.

Residential Subdivision Information

This is not a residential subdivision so this is not applicable.

1.2 Stormwater Management and Sediment Control (CGP Section

3.2.2)

Erosion Prevention BMPs

As the existing site is cleared, grubbed and graded to the proposed contours shown on the construction site plans, erosion prevention BMPs shall be placed throughout the construction site to aid in the prevention of sediment-laden stormwater runoff. These BMPs shall be focused in areas with high potential of erosion, areas preceding infiltration practices, and shall be applied to all steep slopes.

Each erosion prevention measure shall be selected on a site-specific basis and details have been provided on the construction site plans. The plans identify all proposed Erosion Prevention BMPs and the recommended installation, maintenance, and inspection procedures.

Examples of Erosion Prevention BMPs are, but are not limited to, surface roughening, temporary seeding, erosion control blankets, turf reinforcement mats, sodding, riprap, outlet protection, dust control, and polyacrylamide (PAM). Information on the design and proper use of Erosion Prevention BMPs can be located in the SC DHEC’s BMP Handbook.

Sediment Control BMPs

Sediment Control BMPs are designed to remove some of the sediment accumulated within stormwater runoff, to the best extent practicable. These BMPs help prevent sediment impacts to adjacent properties and water bodies from stormwater discharges originating from construction sites.

Typically these BMPs are placed near each of the site’s outfalls and are installed prior to clearing and grubbing of the site (before large areas of soil are exposed). However, these BMPs can also be located throughout the construction site and, in these circumstances, are installed after mass grading has occurred. Placement, sizing and modifications of Sediment Control BMPs should be left to the SWPPP preparer and/or the Site Engineer.

Contractors must consult the project engineer or SWPPP Preparer, as listed at the front of this SWPPP, before making any significant changes to these BMPs.

Each sediment control BMP shall be selected on a site-specific basis. Examples of Sediment Control BMPs are, but are not limited to sediment traps, sediment basins, silt fence, rock check dams, rock sediment dikes, sediment tubes, and inlet protection. All of the erosion and sediment control BMPs utilized are called out on in M-Sheets of the construction plans. Please consult SC DHEC’s BMP Handbook for more information on Sediment Control BMPs.

Structural Control BMPs and Floodplain Placement

No structural control BMPs will be utilized on this site.

Any Structural Control BMPs that are being proposed within the 100-yr floodplains will require approval from the local regulating agency, since SC DHEC does not have the authority to regulate within the associated flood plains. Approvals from the local agency will be located in Appendix C, Additional Approvals/Certifications of this SWPPP. If the required approval is not located in this SWPPP, please contact the Primary Permittee listed on the title sheet of this SWPPP before performing work within the floodplain.

Construction Entrances and Dust Control

All access areas into and out of the limits of disturbance, as shown on the construction site plans, are required to be equipped with a construction entrance. The use of this BMP will limit the amount of sediment being transported by construction vehicles onto existing roadways or other impervious areas. Any tracked sediment, along with any attached pollutants, deposited on impervious areas could be washed downstream during the next rain event. Each construction entrance must be installed as shown in the details section of the construction site plans.

If a new entrance or exit is required, that is not shown on the plans, install the construction entrance as noted by the construction entrance detail, mark the location on the plans and make a record of this minor modification in the SWPPP’s modification log, which is located within one of the appendices of the On-site SWPPP.

During extremely dry conditions, drought, and/or excessive winds, the construction site should be treated for dust control to prevent the suspension of fine sediment particles into the air, being carried offsite, and deposited on adjacent properties or surface waters. This practice is called out for on the M-Sheets of the construction site plans.

Water Quality BMPs During Construction

Site-specific water quality BMPs (e.g., sediment basins, sediment traps, rock check dams, and rock sediment dikes) must be installed prior to the mass clearing, grubbing and grading of the site, and must be kept in functioning order throughout the lifespan of all construction activities. Each of these BMPs must be maintained and inspected until all areas draining to these BMPs have reached final stabilization, approved by the construction site inspector or the SWPPP Preparer, and recorded within the stabilization log located as an appendix of the On-site SWPPP.

The location, installation procedures, and maintenance procedures for each water quality BMP can be found within the approved construction site plans.

Post-Construction Water Quality

Since this project does not disturb 5 acres or more post-construction water quality BMPs are not required.

Other Stormwater Management Procedures

Based on the nature, conditions, and/or procedures associated with this construction site, the following items must be followed and adopted by all those conducting land disturbing activities at this site:

All construction debris must be stockpiled in designated areas, which have been provided with the proper BMPs to prevent the discharge of pollutants through stormwater runoff form building or other similar materials off-site or into surface waters.

Any additional waste material or stockpile material (i.e., soil and mulch) must also be stored in the designated areas as shown on the Construction Site Plans or as the contractor, responsible for day-day activities at this site, deems appropriate. Silt fence or an approved equal shall surround all stockpiled materials.

All parties conducting work at this construction site must be informed of and make note of pollutant sources, both industrial and construction, at this site, and be informed of all controls and measures the will be implemented to prevent the discharge of these pollutants in stormwater runoff.

Any additional non-stormwater discharges, as referenced in the CGP, should be eliminated or reduced to the maximum extent feasible. All unpreventable non-stormwater discharges shall be treated through the approved stormwater management system before release off-site. Following is a list of allowable non-stormwater discharges:

Fire hydrant flushing

Wash water without detergents

Water used for dust control

Potable water

Building wash down water without detergents

Uncontaminated pavement wash water

Uncontaminated condensation from mechanical equipment

Uncontaminated ground or spring water

Water from foundation of footing drains

Uncontaminated excavation dewatering

Landscape irrigation.

Sheet M01 of the construction plans lists additional requirements relating to prohibited discharges, general guidelines, and maintenance and inspection procedures.

1.3 Sequence of Construction

The construction sequence for this project has been provided on sheet M01 of the construction site plans. Each item/step of that construction sequence has been listed is the sequence that they should be implemented.

For additional information or questions on the sequencing please contact the SWPPP Preparer or the Permittee referenced on the cover of this SWPPP.

1.4 Non-Numeric Effluent Limits

Stormwater Volume and Velocity Control

During the implementation of construction activities, all parties performing work at this construction site whose work may affect the implementation of the SWPPP must be informed of and directed on how to comply with this Non-Numeric Effluent Limit, which requires the management of stormwater runoff within the construction site and at each outfall. The purpose of this requirement is to control the stormwater volume and velocity at these locations to minimize erosion.

Specifically, each responsible party should be made aware of the practices that have been or should be implemented at the construction site to accomplish these particular stormwater management practices. Below is a list of practices that may be utilized within the disturbed area and at each outfall at construction sites to control stormwater volume and velocity:

Volume Control

Limiting the amount of disturbed area and exposed soils

Staging and/or Phasing of the Construction Sequence;

Sediment Basins and Sediment Traps

Diverting off-site flow around the construction site;

Controlling the Drainage Patterns within the Construction Site;

Temporary Stabilization of Disturbed Areas.

Velocity Control

Surface Roughening and/or other Slope Stabilization Practices;

Level Spreaders, Riprap Plunge Pools and/or other Velocity Dissipation BMPS located at the Construction Site's and Sediment Basin Outfalls.

Use of Rock Checks, Sediment Tubes, Etc. in Temporary Diversions Swales and Ditches.

Use of Erosion Control Blankets, Turf Reinforcement Mats, and other Non- Vegetative BMPs that can be used to Quickly Stabilize Disturbed Areas.

The SWPPP Preparer/Engineer should approve any modifications (Additional BMPs or Changes to Existing BMPs) to address the management of stormwater volume and velocity prior to implementation. All approved SWPPPs that were issued coverage under the CGP should include ample BMPs and other control measures to address this specific Non-Numeric Effluent Limit.

Soil Exposure, Compaction and Preservation

Throughout construction activities, the amount of soil exposed during construction should be kept to a minimum. This may be accomplished by minimizing the amount the disturbed area within the permitted Limits of Disturbance (shown on the approved construction site plans) to only that which is necessary to complete the proposed work.

For areas that have already been disturbed and where construction activities will not begin for a period of 14 calendar days or more, temporary stabilization techniques must be implemented within 7 days.

Prior to implementation of any major grading activities, topsoil is to be preserved by placing it in areas designated for stockpiling until final grades are reached. Each stockpile must be equipped with proper sediment and erosion controls to preserve the topsoil and protect adjacent areas from impacts. Once final grades have been reached, the preserved topsoil should be utilized to apply to areas identified for stabilization.

Topsoil contains nutrients and organisms that aid in the growth of vegetation.

The Compaction of Soil should also be minimized to the degree practicable during grading activities. This is especially important during the replacement of topsoil to aid in a quick establishment of vegetative cover. Compaction of soil may also reduce rainfall's ability to infiltrate into the soil, increasing the amount of stormwater runoff.

Soil Stabilization

Throughout construction activities, soil stabilization techniques are to be initiated as soon as practicable whenever any clearing, grading, excavating, or other land-disturbing activities have permanently or temporarily ceased on any portion of the construction site and will not resume for a period exceeding 14 calendar days. For areas where initiating stabilization measures is infeasible, (e.g., where snow cover, frozen ground, or drought conditions preclude stabilization), initiate vegetative or non-vegetative stabilization measures as soon as practicable.

Steep Slopes (Slopes of 30% grade or greater)

All disturbed steep slopes (30% grade, ~3H:1V, or greater), and steep slopes to be created through grading activities must be managed in a fashion that limits the potential of erosion along the slopes. All parties whose work is/was responsible for the creation/disturbance of steep slopes must comply with the following items:

Minimize the Disturbance of all steep slopes, when possible.

Divert Concentrated or Channelized Flows of stormwater away from and around steep slope disturbances.

Use Specialized BMP Controls including temporary and permanent seeding with soil binders, erosion control blankets, surface roughening, reducing continuous slope length with terracing or diversions, gradient terraces, interceptor dikes and swales, grass-lined channels, pipe slope drains, subsurface drains, level spreaders, check dams, seep berms, and triangular silt dikes to minimize erosion.

Initiate Stabilization Measures as soon as practicable on any disturbed steep slope areas where construction activities have permanently or temporarily ceased, and will not resume for a period exceeding 14 calendar days.

A Vegetative and/or Non-Vegetative Cover must be established within 3 working days from the time that stabilization measures were initiated.

Stabilization of steep slopes should be a priority for those performing work at the construction site. At the very least, runoff control BMPs should be implemented to transport stormwater runoff from the top of the slope to the toe of the slope. An example of this is to install diversion swales along the top of slope and direct the runoff towards pipe slopes drains to transports the runoff to the toe of the slope. All pipe slope drain outlets are to be equipped proper outlet protection.

Sediment Discharge Minimization

Permittees, Contractors, and all other parties responsible for conducting land-disturbing activities are required to install and maintain all erosion and sediment BMPs that are identified on the approved construction site plans. These BMPs have been designed and approved to address such factors as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soils particle sizes expected to be present on the construction site. Proper installation, inspection, and maintenance will allow these BMPs to operate at maximum efficiencies in order to minimize sediment discharges to the maximum extent practical.

Pollutant Discharge Minimization

Permittees, Contractors, and all other parties responsible for conducting land-disturbing activities are required to install, implement, and maintain effective pollution prevention measures to minimize the discharge of pollutants. At a minimum, the following items must be implemented:

Minimize the discharge of pollutants from dewatering trenches and excavations by managing runoff with the appropriate controls. Otherwise these discharges are prohibited;

Minimize the discharge of pollutants from equipment and vehicle washing, wheel wash water, and other wash waters. Wash waters must be treated in a sediment basin or alternative control that provides equivalent or better treatment prior to discharge;

Minimize the exposure of building materials, building products, construction wastes, trash, landscape materials, fertilizers, pesticides, herbicides, detergents, sanitary waste and other materials present on the site to precipitation and to stormwater; and

Minimize the discharge of pollutants from spills and leaks and implement chemical spill and leak prevention and response procedures.

Prohibited Discharges

Permittees, Contractors, and all other responsible parties for conducting land-disturbing activities are prohibited to discharges, from the construction site, the following items:

Wastewater from washout of concrete, unless managed by an appropriate control;

Wastewater from washout and cleanout of stucco, paint, form release oils, curing compounds and other construction materials;

Fuels, oils, or other pollutants used in vehicle and equipment operation and maintenance; and

Soaps or solvents used in vehicle and equipment washing.

1.5 Buffer Zone Management

Buffer Zone Narrative (Compliance Option C)

Per Section 3.2.4.C of the CGP, a buffer zone is required to be provided along Perimeter Pond and the Dawho River; however, an undisturbed buffer zone is not capable of being provided due to pre-existing development that has disturbed the majority of the required buffer zone area. For this reason, Compliance Option C was selected for this project.

Section 2 SITE FEATURES AND SENSITIVE AREAS

2.1 Sources of Pollution

Throughout construction activities, each permittee, contractor, and person responsible for conducting work will need to ensure that sources of pollution are managed to prevent their discharge from the construction site. Expected pollution sources during construction have been identified in Table 2.1-A, but due to the nature of construction activities, it is often tough to predict all pollution sources that may appear throughout the life of a construction project. For that reason, the following table has also been provided to help all those performing work at this construction site identify possible sources of pollution

Stormwater runoff subjected to the identified pollution sources must be treated by the appropriate BMPs as directed by this SWPPP.

In the event that any additional sources of pollution are identified during construction, the person(s) with day-to-day operational control at the site is to add the new source(s) to Table 2.1-A and consult with the SWPPP Preparer to properly address this source and to prevent the discharge of it's pollutant through stormwater runoff.

Table 2.1-A: Potential Sources of Pollution

Source Material or Chemical

Location* Appropriate Control Measures

Loose soil exposed/disturbed during clearing, grubbing and grading activities

Sediment

All areas within the Limits of

Disturbance

As directed by the construction Plans. This includes Silt Fence, sediment tubes, sediment basins, and sediment traps.

Areas where construction equipment are cleaned, a.k.a.

concrete washout

Heavy Metals & pH

Located adjacent to each construction entrance

Concrete Washout Basin as shown on sheet C-8 of the plans.

Water encountered during trenching

Nutrients & Sediment

In and around any trenching activities.

Direct water into impoundments such as basins or traps to allow for the sedimentation of the listed pollutants.

Paving Operations

Sediment & Trash

All areas to be paved.

Inlet protection.

Material Delivery and Storage

Nutrients, pH, Sediment, All areas used as storage

Silt fence and/or sediment dikes.

Areas Heavy Metals, oils & grease areas

Equipment fueling and maintenance areas

Metals, hydrocarbons, oils and greases

Areas surrounding fuel tanks

Provide secondary containments, locate in upland areas. Repair leaking and broken hoses.

Paints

Metal oxides, stoddard solvent, talc, calcium-carbonate, arsenic

Throughout site, primarily in areas of building construction

Wash water should be contained and is prohibited from being discharged.

2.2 Surface Waters

Stormwater runoff from the proposed construction site discharges from 8 locations as outlined in Figure 2.2 to low lying areas or unnamed tributaries of Dawho River, which lies along the southern boundary of the site. The first outfall is located in the along the southern edge of Grove Road. The second outfall is located in the northeast edge of Perimeter Road into marshlands that connect to an unnamed tributary of Dawho River.

The third outfall is located along the eastern edge of Perimeter Road and discharges into an unnamed tributary of Dawho River. The fourth outfall is the western edge of Perimeter road along Perimeter Pond, at this location the roadway drains into Perimeter Pond. The fifth outfall is on the eastern edge of Perimeter Road along Perimeter Pond where the roadway discharges into multiple unnamed tributaries of the Dawho River.

The sixth outfall is located on the southwestern edge of Perimeter Road and discharges into an unnamed tributary of the Dawho River. The seventh outfall is located at the south east edge of Perimeter Road and discharges into marshlands. The eighth outfall discharges from the parking area at the southernmost part of the project site and directly into the Dawho River. From the multiple unnamed tributaries, the stormwater runoff from this site will enter the Dawho River. The Dawho River discharges into the South Edisto River.

1,520 LF of Perimeter Pond, as outlined on the construction plans, has been identified as a managed tidal impoundment. This area is proposed for grading for the rehabilitation of an existing causeway and road. A Managed Tidal Impoundment General Permit has been obtained from the USACOE and is included in Appendix L. A Coastal Zone Consistency Certification will be obtained from DHEC Office of Ocean and Coastal Resource Management.

Figure 2.2: Stormwater Runoff Route

2.3 Impairments and TMDLs

Impairments Effected by Construction Site Discharges and Methods to Control Potential Pollutants Causing or Contributing to the Impairments

Some Waters of the State (WoS) have been identified as not meeting the State’s water quality standards for recreational swimming, fish consumption, aquatic life use, and/or shellfish harvesting for one or more pollutants even after controls for point and nonpoint source pollution have been put in place. These waterbodies have been classified as “impaired.” Once these waterbodies have been identified they are listed on the State’s

303(d) List of Impaired Waterbodies. South Carolina lists impairments as “stations” where samples were taken along a waterbody.

The most recently-approved 303(d) list can be found at the following link:

http://www.scdhec.gov/environment/water/tmdl/index.htm#4

After a pre-determined period of time, DHEC is obliged to develop a Total Maximum Daily Load (TMDL) for the pollutant of concern for each impaired station listed on the 303(d) List. A TMDL is the amount of a single pollutant (such as bacteria, nutrients, metals) that can enter a waterbody on daily basis and that waterbody still meet water quality standards. “TMDL” refers to both a calculation of a pollutant entering a waterbody as well as the document containing this calculation along with source assessments, watershed and land use information, reductions and allocations information, implementation and other relevant information, maps, figures, and pictures.

Once a TMDL has been developed and approved by the EPA, the impaired WoS is removed from the 303(d) list. A separate list is maintained for WoS with approved TMDLs.

Any construction site whose discharges are released into a WoS listed on the 303(d) List or for which an EPA-approved TMDL has been developed must address the specific pollutant set forth in the TMDL and/or potential pollutants for the impairment. The SWPPP must include a description of BMPs to address these pollutants.

The primary permittee and/or contractor must ensure that the construction site discharges remain in compliance with the State’s water quality standards. To do so, these parties will have to ensure the function of all approved BMPs to handle the specific pollutant.

Construction Stormwater Discharges are expected to contain pollutants that contribute and/or can cause the following impairments to receiving water bodies: BIO (Macroinvertebrate Community), Turbidity, TP (Total Phosphorus), TN (Total Nitrogen), CHLA (Chlorophyll-a), and Fecal Coliform in waters classified for Shellfish Harvesting in the coastal zone. The presence of any of these impairments in receiving waters will require approval control of the site’s construction stormwater discharges. Information on each of these impairments and how to treat stormwater runoff for these impairments has been provided below.

1. BIO (Macroinvertebrate Community): A balanced and varied group of Macroinvertebrate organisms is an indicator of a healthy stream that supports aquatic life. A balanced community can be defined as a natural, diverse group of organisms (including Macroinvertebrate) characterized by the ability to sustain itself through season changes, presence of food chain species and a lack of domination by pollutant tolerant or invasive species. If these conditions do not exist, then the site may be considered impaired due to the presence of an undesirable or non-existent Macroinvertebrate community. Sediment from construction sites may further threaten the propagation of these organisms.

Address by: Examples include limiting the amount of disturbed area, designing sediment control BMPs to remove the maximum amount of sediment possible, immediate stabilization of disturbed areas, and other practices may be utilized to control the discharge of sediment from construction sites.

2. Turbidity: Turbidity can be generally defined as the “cloudiness” of a waterbody and may be caused by the growth of aquatic phytoplankton and the presence of suspended solids in the water column. In SC, a water quality standard for turbidity is applicable to all waters of the State (see R. 61-68 D. 11. for numeric targets by waterbody classification). Turbidity levels that exceed the water quality standard may reduce light penetration, thereby inhibiting aquatic flora growth, and may reduce the ability of fauna, such as fish, to absorb oxygen across their gills.

Address by: Examples include limiting the amount of disturbed area, designing sediment control BMPs to remove the maximum amount of sediment possible, immediate stabilization of disturbed areas, and other practices may be utilized to control the discharge of sediment from construction sites.

3. TP (Total Phosphorus): Similar to total nitrogen, TP is an essential nutrient for the propagation of aquatic life. In SC, a water quality standard for TP is applicable to lakes greater than 40 acres (see R. 61-68 D. 11. for numeric and narrative targets). At acceptable levels, TP is assimilated by aquatic flora ensures the propagation of an overall balanced, indigenous aquatic community. TP levels that exceed the water quality standard are considered impaired and may cause negative impacts to the overall health of the aquatic community by promoting excessive algal growth in lakes. Phosphorous may enter a site’s stormwater when excess amounts of the nutrient are applied to the site during temporary or final stabilization.

Address by: To prevent this soil should be tested to determine the quantity of the nutrient present in the soil and the correct amount that needs to be added so that it is absorbed by the vegetation.

4. TN (Total Nitrogen): Similar to total phosphorus, TN is an essential nutrient for the propagation of aquatic life. In SC, a water quality standard for TN is applicable to lakes greater than 40 acres (see R. 61-68 D. 11. for numeric and narrative targets). At acceptable levels, TN is assimilated by aquatic flora and ensures the propagation of an overall balanced, indigenous aquatic community.

TN levels that exceed the water quality standard are considered impaired and may cause negative impacts to the overall health of the aquatic community by promoting excessive algal growth in lakes. Nitrogen may enter a site’s stormwater when excess amounts of the nutrient are applied to the site during temporary or final stabilization

Address by: Examples include that the soil should be tested to determine the quantity of the nutrient present in the soil and the correct amount that needs to be added so that it is absorbed by the vegetation.

5. Chlorophyll-a (CHLA): CHLA is a pigment present in the cells of photosynthetic flora and some algal species. The presence of CHLA in an aquatic environment is a water quality indicator of the overall productivity in the aquatic system. CHLA is linked to the levels of TP, TN and light penetration in the water column. In SC, a water quality standard for CHLA is applicable to lakes greater than 40 acres (see R. 61-68 D. 11. for numeric and narrative targets). CHLA levels that exceed the water quality standard may suggest that other undesirable water quality impacts are present as the aquatic system may be too productive to support the propagation of an overall balanced, indigenous aquatic community.

Excess nutrients may discharge from a construction site during temporary and final stabilization. Limiting the amount of phosphorus and nitrogen applied while establishing vegetation will prevent excessive levels of CHLA in receiving waters.

Address by: Examples include that the soil should be tested to determine the quantity of the nutrients present in the soil and the correct amount that needs to be added so that it is absorbed by the vegetation.

6. Fecal Coliform (FC) in Shellfish Harvesting waters: Fecal Coliform is an indicator bacteria for other pathogens which may be present in a waterbody.

Shellfish Harvesting Waters are tidal salt waters protected for shellfish harvesting and must be protected to a higher standard than other waters because of the risk to human health posed by ingesting shellfish from areas with high levels of bacteria.

Bacteria levels increase following rain events. Potential sources of bacteria on construction sites include improperly located porta-johns and litter that may attract rodents and other animals.

Address by: Porta-johns should be placed away from WoS and not placed on catch basins and other drainage structures. Litter and construction debris should be placed in identified areas and emptied on a routine basis.

Impairment Sources and Prevention

Construction sites can contribute to these impairments directly through the release of excess soil and/or nutrients within stormwater runoff. For this reason, proper sediment and erosion control BMPs should be implemented and the design of the stormwater management systems, during both construction and post-construction, should address the control of stormwater runoff. A reduction in the volume released or the rate at which this volume is released can significantly improve the quality of stormwater runoff and limit the amount of the pollutants that contribute to the above listed impairments.

As an example, sediment basins and/or traps should be used during construction to allow for sedimentation of soils/nutrients, and to control the release of stormwater into the impaired water body. Vegetated Detention and Infiltration structures should be implemented as post-construction BMPs to control stormwater volumes. Caution is advised when using fertilizers to reach Final Stabilization; excess fertilizer can contributes to each of the above listed impairments.

Site-Specific Requirements

This construction site’s discharges drain into WoS that is either Impaired or has an established TMDL for the following impairment(s): Enterococci and/or Turbidity. Due to the possibility of pollutants in construction stormwater discharges from this site that may contribute to any of these impairments, the following must be conducted throughout the lifespan of all land-disturbing activities at this site:

Monthly monitoring of the construction site’s outfalls;

Weekly inspections of all the primary sediment control BMPs, and within 24 hours of a rainfall of .25 inches or more;

Employee training/acknowledgement during the Pre-Construction Meeting;

Installation of additional BMPs to meet the water quality standards (as directed by the SWPPP preparer and as approved by the regulating agency); and

All sediment control BMPs have been designed to meet or exceed an 80% trapping efficiency.

2.4 Critical Areas (CZC only)

The project is located within a coastal zone county. This project includes the reconditioning of an existing causeway for a managed tidal impoundment; therefore no new impacts to Critical Areas will occur.

Section 3 Compliance Requirements

3.1 SWPPP Availability

A copy of the OS-SWPPP, as defined by Section 3.1.1.H, must be retained at the construction site or a nearby location easily accessible during normal business hours, from the date of commencement of construction activities to the date that final stabilization is reached.

On-Site SWPPPs must be made available upon request and at the time of a construction site inspection by EPA; DHEC; a tribal or an entity delegated under Regulation 72-300;

local government officials; and the Operator of a Municipal Separate Storm Sewer System (MS4) receiving discharges from the construction site to the requestor.

3.2 Pre-Construction Conferences

The pre-construction conference requirements are located in the construction plans on sheet M02.

3.3 Inspection Requirements

The inspection requirements for all BMPs are located in the construction plans on sheet M01.

3.4 Maintenance Requirements

The maintenance requirements for all BMPs are located in the construction plans on sheet M01.

3.5 Record Keeping

The record keeping requirements are located in the construction plans and specifications.

3.6 Final Stabilization

The final stabilization requirements are located in the specifications.

Appendix A Site Maps

To develop a site-specific SWPPP for a construction map, an assortment of site maps must be used in addition to an on-site assessment to develop an effective stormwater sediment and erosion control plan. The maps located in this appendix have been obtained from various sources, or have been developed by the SWPPP Preparer. Listed below is standard information on a few of the type of maps that may be found within this Appendix.

Locations Maps

A general location map is helpful to identify nearby water bodies in proximity to other properties, and can be a useful tool used to locate the site when on the road. This map should include the outlined project locations, labeled roadways, a North arrow and a scale. SWPPP Preparers may opt to locate this map on the first sheet of the construction site plans in lieu of including it in this appendix.

Site Maps

Site maps tend to go a step beyond a typically location map by adding zooming in on the limits of disturbance and identifying a number of features at the construction site related to land-disturbing activities and stormwater management practices. Each site map should include the following: Stormwater flow directions and discharge locations, Areas and features to be protected, Outline of disturbed areas, Locations of all major BMPs, Areas to remain stabilized, and Adjacent features (e.g., road and water bodies).

Topographic Maps

Topographic Maps can be very useful when determining the existing contours at a construction site, not to mention the existing drainage patterns. These maps must include the project boundary outline, route of runoff from site to nearest waterbody shown, and adjacent road names. These maps are readily available on the Internet (e.g., www.terraserver.com) or by contacting the US Geological Survey Store (http://store.usgs.gov).

Soils Maps

Soils Maps are helpful tools used to determine the soil types and other soil characteristics that are located at a construction site. Each soils map must contain the project boundary outline and the predominate soil types found at the site. Soils Maps can be readily obtain online from the NRCS (http://soils.usda.gov).

Floodway Maps

Floodway Maps are used to determine the location of the 100-yr Flood Plain and other related flooding issues at or adjacent to the construction site. Each Floodway Map must contain the project boundary outline and a legend. These maps can be readily obtain online from FEMA (www.fema.gov).

Sources: Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Communityq

FW-ACBA 100(1)

LOCATION MAP

0 8 16 24 324 Miles brian.eisenmann Rectangle brian.eisenmann Callout Project Location

Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community q 0 0.5 10.25 Miles

FW-ACBA 100(1)

LOCATION MAP

S ta te R oa d

S -1

-3

Grove Road

Perimeter Road

USGS The National Map: National Boundaries Dataset, National Elevation Dataset, Geographic Names Information System, National Hydrography Dataset, National Land Cover Database, National Structures Dataset, and National Transportation Dataset; U.S. Census Bureau - TIGER/Line; HERE Road Data

FW-ACBA 100(1)

TOPOGRAPHIC MAP

0 0.2 0.4 0.6 0.80.1 Miles brian.eisenmann Polygonal Line brian.eisenmann

Approximate project location brian.eisenmann Polygonal Line brian.eisenmann

Approximate project location

Appendix B Drainage Maps

Drainage maps become an essential tool when both developing and reviewing hydrology models of a construction site during the various phases of developing such a site (i.e.

pre-development conditions, construction conditions, and post-development conditions).

Typically these maps are enhanced site maps that add the features of drainage basins outlines and their respective outfall markers. Each SWPPP must contain, at a minimum, a pre-development and a post-development drainage map for the entire on-site area and adjacent off-site areas that contribute runoff to any of the marked outfall locations.

Additional drainage maps should also be included for any sediment control BMP in which sediment trapping efficiency calculations are required to be submitted. A drainage map for “During Construction” conditions should also be included if the basin and subbasin drainage patterns differ from both the pre-development and post-development patterns.

All provided drainage maps must clearly correspond to any calculations submitted for review, the outfall locations chosen for comparing runoff rates and the total drainage area analyzed (from pre- to post-development conditions) may not change. However, the immediate drainage areas contributing to each outfall location may shift.

Each Drainage Map should be provide on an 11x17 sheet and must show the contours for the specific stage of construction each map represents.

Description

Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms.

The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows:

Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.

Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.

Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.

Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material.

These soils have a very slow rate of water transmission.

If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes.

Rating Options

Aggregation Method: Dominant Condition

Component Percent Cutoff: None Specified

Tie-break Rule: Higher

Hydrologic Soil Group—Charleston County Area, South Carolina, and Colleton County, South Carolina

Natural Resources Conservation Service

Web Soil Survey National Cooperative Soil Survey

10/27/2015

Appendix C Additional Approvals/Certifications

This appendix has been provided as a catchall to store any additional correspondences that may be required to either obtain coverage under the current CGP or to implement land-disturbing activities at a construction.

Examples and descriptions of such correspondences have been listed below. All associated correspondences and approval for this site-specific SWPPP can be located on the following pages.

Coastal Zone Consistency Certification

A Coastal Zone Consistency (CZC) Certification needs to be obtained for all land disturbing activities located within any of the eight coastal counties (Beaufort, Berkeley, Charleston, Colleton, Dorchester, Georgetown, Horry and Jasper) before applying coverage under the NPDES Permit Program. These certifications establish that all land and water uses within these critical areas are consistent with both the State’s Coastal Zone Management Plan (SCCZMP) and the Federal Coastal Zone Management Act.

CZC Certifications ensures that any land disturbance activities will be conducted in a manner in which they preserve, protect, develop, and where possible, restore and enhance the resources located within South Carolina’s coastal zone.

Please contact the DHEC-OCRM office nearest you for all information on the types of permits or certifications needed for your particular project. More information on 401 Certifications can be found on DHEC's website via the following link:

http://www.scdhec.gov/environment/water/401.htm

USACE's Jurisdictional Determinations

The procedure of identifying and locating jurisdictional waters of the US regulated by the Corps under Section 404 of the Clean Water Act and Section 10 of the Rivers & Harbors Act of 1899 is commonly referred to as the “Jurisdictional Determination Process”, a “wetland determination” or a “delineation”. In general, these determinations are good for five years from the date the Corps notifies you in writing that you have accurately delineated the jurisdictional features on your property.

This survey procedure establishes a line that identifies and separates the Corps regulated areas from non-regulated areas. Regulated (i.e., jurisdictional) areas can include wetlands, stream channels, rivers, lakes, ponds and coastal and offshore waters.

The JD process is essential when investigating, planning, designing, or submitting an application for a permit from the Corps to determine if the proposed work will occur in wetlands or waters of the…