2024  Stormwater Master Plan Report TOWN OF HOLDEN BEACH, NORTH CAROLINA  Prepared by: McGill Associates  Shaping Communitics  mcgil Together McGill Associates, P.A. 712 Village Rd. Suite #103 Shallotte, North Carolina 28470 Firm License No.: C-0459    TOWN OF HOLDEN BEACH  BRUNSWICK COUNTY, NORTH CAROLINA STORMWATER MASTER PLAN REPORT  MICHAEL HANSON, PE, LEED AP  SEAL. 030624  Mig Hanso  gsigned by Al Hanson 8i5:50-0400 2024.06.04  mcgil 712' Village Rd. Suite #103 Shallotte, North Carolina 28470 910.755.5872 JUNE 2024 PROJECT NO. 22.07132  Holden Beach Stormwater Master Plan Report    Executive Summary  Town of Holden Beach Stormwater Master Plan  Introduction/Scope ofV Work  The Town of Holden Beach (Town) has retained McGill Associates (McGill) to prepare this Stormwater Master Plan (SWMP). The primary purposes of this project were to analyze the existing stormwater system at six known areas of concern, evaluate altematives to remedy flooding at these locations, identify future opportunities for stormwater improvements, and create af financial model to determine viability of a Town Stormwater Utility (SWU). The aforementioned  areas of concern are as follows:  Area 1-3 300 Block of Ocean Boulevard West Area 2 - East End of Mullet Street & East End of Avenue A Area 3 - West End Right-of-Way Area 4 - 760 Block of Ocean Boulevard West Area 5- Carolina Avenue Area 6-Davis Street  Ageographic information system (GIS)-based stormwater system inventory and limited closed circuit TV (CCTV)inspections were performed on the existing storm sewer system. Additionally, a detailed topographic survey of drainage features within identified areas of concern was This data was used to develop a hydrologic and hydraulic model of the island community. This model was used to assess the capacity of the existing stormwater system for the 2-year and 10- year storm events within the identified areas of concern and for the 2-year storm event and Two alternative solutions to alleviate flooding at each area of concern were evaluated along with estimating the cost of each alternative solution. A recommended alternative was provided for each area of concem while al heat map was developed for other areas toi identify future A financial model was developed to determine the revenue, expenses, and ultimate viability ofa Town Stormwater Utility including two potential funding scenarios. Revenue was determined using a flat fee amount per month for each parcel. The financial model uses $7.20 per month per developed parcel for Scenario A assuming the projects are funded entirely by the Town. Scenario B assumes grant funding equal to 75% of the project cost with the remaining 25% of the cost funded by the Town. These rates compare favorably to the mean rate charged by four (4) stormwater utilities in coastal communities within approximately 30 miles that charge a flat fee AStormwater Master Plan was prepared to summarize the results and provide recommendations.  performed.  sunny day mean higher-high tide across all other portions of the system.  opportunities for stormwater system improvements.  (Oak Island, Kure Beach, Carolina Beach, and Wilmington) of$11.76.  Holden Beach Stormwater Master Plan Report    Recommendations recommendations to the Town: Stormwater improvements  After completing our requested scope of services, McGill is pleased to provide the following  Area1-3 300 Block of Ocean Boulevard West (OBW)  Issue: Flooding in public ROW and roads during 2-year storm event. Public Benefit: Eliminate 2-year flooding along OBW and Brunswick Ave. Recommended Solution: Install a system of High-Perforance Polypropylene pipes (HPPP) along OBW and High Point St. that discharges into the existing Brunswick Ave. channel. Upsize the existing culvert under Mile Marker Fifty-Five Dr. and the outlet pipe along High Point St. Construct two (2) storage depressions int the ROW between OBW and Brunswick Ave. and connect to the proposed system. Lower the Brunswick Ave. In the future, storage depressions may be converted to underground storage units in order to provide some additional public benefit such as parking or roadway.  channel to accommodate connection into the proposed system.  Area 2- East End of Mullet Street & East End of Avenue A Issue: Flooding in public ROW and road during 2-year storm event.  Public Benefit: Eliminates 2-year flooding along Ocean Boulevard East (OBE) east of Mullet St. and 10-year roadway flooding between Avenue A. and Dunescape drive. Recommended Solution: Dropi inverts of existing pipes along OBE west of Mullet St. to create a positive outfall. Install 1-foot-deep swales along OBE between Dunescape Dr. and McCray St., connected to the existing system via HPPPS. Upsize existing pipes along OBE east of Mullet St. and along Mullet St. to the outfall. Install a tide gate on the  final outlet pipe.  Area 3- West End Right-of-Way  Issue: Flooding inj public ROW and road during 2-year storm event. Public Benefit: Reduces 2-year roadway flooding.  Recommended Solution: Install a system of HPPPS and Reinforced Concrete Pipes (RCP) at the low point of OBW to discharge through an easement into the Intracoastal  Waterway.  Holden Beach Stormwater Master Plan Report  ili    Area 4- 760 Block of Ocean Boulevard West  Issue: Flooding in public ROW and street during 2-year storm event. Public Benefit: Eliminates 2-year flooding along OBW.  Recommended Solution: Install a system of RCPS along the ROW of OBW to discharge  into the Intracoastal Waterway. Area 5- Carolina Avenue  Issue: Flooding in public ROW and street during 2-year storm event. Public Benefit: Eliminates 2-year and 10-year flooding along Carolina Ave. Recommended Solution: Install a system of 24" RCPS along Carolina Ave. and Halstead  St. to discharge into the Intraçoastal Waterway.  Area 6- Davis Street  Issue: Surface runoff erosion from ROW into Intracoastal Waterway. Public Benefit: Improved water quality within the Intracoastal Waterway. Recommended Solution: Install a grassed blind swale with level spreader at the end of the road and adjust existing outfall pipes as needed for proper operation.  Town Stormwater Utility  Based on the project cost of capital stormwater projects and on-going and planned maintenance for the stormwater system we recommend proceeding with implementation of Scenario A (full Town funding), should the Town decide to implement a stormwater management utility. This scenario provides sufficient funds to cover the planned activities for the next ten years while maintaining a sufficient fund balance that suggests the utility will remain stable and fiscally healthy. Ifp pursuit of grant funding is favorable, the utility can easily be converted to Scenario Bin  the future and rates reevaluated at that time.  Holden Beach Stormwater Master Plan Report    Table of Contents Executive Summary 1.0 Introduction.  2.0 Existing Stormwater System Mapping 3.0 Hydrologic and Hydraulic Analysis. 4.0 Existing Stormwater System Analysis. 5.0 Evaluation of Alternatives 6.0 Stormwater Project Recommendations 7.0 Other Problem Areas.. 8.0 Stormwater Utility Feasibility Assessment. 8.1 Revenue. 8.2 Expenses 8.3 Utility Scenarios. 8.4 Model Outcomes. REFERENCES  13 16 36 38 41 41 41 42 44  ATTACHMENTS Attachment A Attachment B Attachment C Attachment! D Attachment E Attachment F Attachment G Attachment H Attachment!  As-Built Survey & Stormwater Network Map  Drainage Basin Maps Hydrologic Data & Calculations Existing Conditions Maps Proposed Conditions Maps Engineering Details  Existing Island-Wide Flooding Heat Map Construction Cost Estimates Stormwater Utility Financial Model Outcomes  Holden Beach Stormwater Master Plan Report    1.0 Introduction  The Town of Holden Beach (Town) is located in Brunswick County, North Carolina on a barrier island that sits between Oak Island to the east and Ocean Isle to the west. Iti is surrounded by the Intracoastal Waterway to the north and the Atlantic Ocean to the south (Figure 1.1). The Town's stormwater infrastructure includes a combination of pipes, structures, and ditches which convey stormwater throughout the Town. The North Carolina Department of Transportation (NCDOT) also owns and maintains stormwater infrastructure within the Town The Town's stormwater infrastructure is frequently overburdened by rainfall events, as well as sunny day tidal flooding, resulting in erosion, road blockages, and damage to surrounding properties. The following six areas of concern have been identified by the Town for capital improvement projects, with Areas 1-5 facing regular flooding and Area 61 facing surface runoff  limits associated with NCDOT roads.  erosion.  1. Area 1-; 300 Block of Ocean Boulevard West 2. Area 2- East End of Mullet Street & East End of Avenue. A 3. Area 3. - West End Right-of-Way 4. Area 4. -7 760 Block of Ocean Boulevard West 5. Area 5- Carolina Avenue 6. Area 6- Davis Street  The Town retained McGill Associates, PA (McGill) to evaluate the Town's stormwater network 1. Analyze the existing stormwater system and drainage conditions at each area of concern 2. Identify deficiencies in the network at these locations and evaluate available alternatives 3. Develop an island-wide flooding heat map for the 2-year rainfall event and sunny day 4. Create a financial model to determine the revenue, expenses, and ultimate viability ofa  with focus on these areas of concem. The goals of this evaluation were to:  for the 2-year and 10-year rainfall events.  to remedy flooding.  high tide to identify future opportunities fori improvement.  Town Stormwater Utility (SWU).  Holden Beach Stormwater Master Plan Report  6    Shallotte  Varnamtown  Holden Beach  2,000 4,000 8,000 lin=4,000R  Feet  Figure 1.1 Location Map  Holden Beach Stormwater Master Plan Report  7    2.0 Existing Stormwater System Mapping  Available data was acquired from reliable sources such as Town records, the North Carolina Floodplain Mapping Program (NCFMP), survey, and the NCDOT and collated to develop an understanding of major drainage patterns, outfalls, and area characteristics. McGill conducted a meeting and field reconnaissance trip with Town staff to confirm which drainage outfalls, pipes, and ditches were present in each area of concem and to identify any major data gaps needed to A field mapping program was conducted by McGill to populate a Geographic Information System (GIS) database of the stormwater features and develop an initial inventory of the fragmented stormwater network (Attachment. A). This consisted of Global Positioning System (GPS)grade mapping of all stormwater system drainage features including inlets, catch basins, pipes, and ditches where present as well as a topographic survey of key areas of concer along Ocean Boulevard. Closed Circuit Television (CCTV) inspections were attempted on two outfalls, however, there was material present which blocked half or more of both pipes and resisted initial removal efforts, preventing a complete inspection along the entire length of the pipes. The datum reference for GPS and survey was North American Datum of 1983 (NAD 83) for horizontal position data and North American Vertical Datum of 1988 (NAVD 88) for vertical The stormwater network map included in Attachment. A shows some of the data collected. The full extent of the data content is included in the GIS geodatabase provided as a digital submittal.  bet filled to analyze the system.  elevation data.  Holden Beach Stormwater Master Plan Report    3.0 Hydrologic and Hydraulic Analysis  Computational Hydraulics Interational's (CHI) Personal Computer Storm Water Management Model (PCSWMM) version 7.6 was used to conduct hydrologic and hydraulic analyses for this study. Drainage basin boundaries (Attachment B) were delineated using QL2 LIDAR data from the North Carolina Spatial Data Download (NC SDD), survey data, aerial imagery, and site photos for each of the following areas of concern identified by the Town:  Area 1-3 300 Block of Ocean Boulevard West  This area of concem includes Ocean Boulevard West (OBW) and Brunswick Avenue West between High Point Street and Neptune Street. The existing stormwater network consists of ditches and culverts along the north side of Brunswick Ave. W. that continue down the east side of High Point St. before discharging into the Intracoastal Waterway. A few pipes that act as underground detention and discharge via infiltration into the soil are present on OBW. For the purposes of this analysis, these detention pipes were not Sub-basins in this area are assigned basin numbers with an A1-Dx prefix. Area 2-E East End of Mullet Street Area & East End of Avenue A  included in the model.  This area of concem includes Ocean Boulevard East (OBE) between Mullet Street and Dunescape Drive, however, in order to model the full stormwater network in this area, the model also included the area of OBE between Mullet Street and Halstead Street. The existing stormwater network consists of ditches and pipes that run along the south side of OBE between Halstead Street and McCray Street and meet at Mullet Street where they run north to discharge into the Intracoastal Waterway. Sub-basins in this area are assigned basin numbers with an A2-Dx prefix.  Area 3-1 West End Right-of-Way  This area of concem includes Ocean Boulevard West between 1324 and 1308 OBW. The existing stormwater network consists of a few pipes that act as underground detention and discharge via infiltration into the soil. For the purposes of this analysis, Sub-basins ini this area are assigned basin numbers with an A3-Dx prefix.  these pipes were not included in the model. Area 4-760 Block of Ocean Boulevard West  This area of concern includes Ocean Boulevard West between 762 and 714 OBW. The existing stormwater network consists of a few pipes that act as underground detention and discharge via infiltration into the soil. For the purposes of this analysis, these pipes  were not included in the model.  Holden Beach Stormwater Master Plan Report  9    Sub-basins int this area are assigned basin numbers with an A4-Dx prefix.  Area 5- Carolina Avenue  This area of concem includes Carolina Avenue between Halstead Street and the end of Carolina Avenue. The existing stormwater network consists of a few pipes that act as underground detention and discharge via infiltration into the soil. For the purposes oft this Sub-basins in this area are assigned basin numbers with an A5-Dx prefix.  analysis, these pipes were noti included in the model.  Area 6-1 Davis Street  This area of concer includes Davis Street. The existing stormwater network consists of two short swale segments that discharge to the Intracoastal Waterway via two short High-Density Polyethylene (HDPE) pipes through the seawall at the end of the road, Sub-basins in this area are assigned basin numbers with an A6-Dx prefix.  however these are not depicted on the survey.  Curve numbers were determined by combining United States Geological Survey (USGS) soils data (Attachment C) with the 2021 National Land Cover Database (NLCD) land use data in The time of concentration for the study basins was calculated by PCSWMM using the Soil Conservation Service (SCS) Curve Number method. The total precipitation depth data for the 2- year and 10-year 24-hour storms were obtained from the National Oceanic and Atmospheric Administration (NOAA) Atlas 14 (Attachment C). Seasonal high-water table (SHWT) and groundwater level data were available from other studies performed on the island by ECS Southeast LLC. From these sources the SHWT used for this project is estimated at elevation The computed hydrologic data (Table 3.1) was used to conduct hydrologic and hydraulic (H&H) modeling using PCSWMM. Runoff was computed using the SCS Curve Number method.  ArcGIS Pro.  2.5 with the groundwater level around elevation 2.  Holden Beach Stormwater Master Plan Report  10    Table 3.1. Summary of Model Hydrologic Inputs  Area of Basin Area Concern Name  Time of CN Concentration (min) 24 14 14 24 24 22 30 32 28 41 10 28 29 19 24 31 18 17 35 17 18 19 25  (ac)  A1-D1 7.40 A1-D2 4.49 A1-D3 3.34 A1-D4 5.22 A1-D5 6.17 A1-D6 3.25 A2-D1 9.05 A2-D2 5.82 A2-D3 8.41 A2-D4 10.22 A2-D5 0.99 A2-D6 9.84 A2-D7 23.88 A2-D8 1.72 A2-D9 2.86 A2-D10 2.64 A2-D11 1.75 A3-D1 3.78 A4-D1 7.52 A4-D2 2.97 A5-D1 4.73 A5-D2 2.57 A6-D1 3.05  60 60 60 59 59 58 61 60 59 59 61 60 66 57 53 58 54 60 61 60 60 61 59  1  2  3 4 5 6  The hydraulic parameters of the current stormwater system were input into the model based on the data collected during survey. Channel cross-sections were generally based on the topographic survey, supplemented with QL2LIDAR as needed. Overland flow was modeled as overtopping weirs to simulate flow over the roads or connections between adjacent basins. Weir crest elevations and dimensions were approximated from the topography at each location. Tidal data was obtained from two National Oceanic and Atmospheric Administration (NOAA) Tidal Datum Stations, Bowen Point- Shallotte Inlet on the west side of the island and Varnamtown Lockwoods Folly River on the east side of the island. Mean tide levels and mean higher-high water (MHHW) levels were obtained from each station and averaged together to create one mean tide and one MHHW level for the whole island (Table 3.2 and Attachment C). Outfalls were set to a fixed elevation equivalent to the mean tide for the 2- and 10-year storm event runs and the MHHW level was used to simulate sunny day flooding conditions.  Holden Beach Stormwater Master Plan Report  11    Table 3.2-Tidal Station Data  Mean Higher-High Water Level (ft.) 4.76 4.27 4.52  Mean Tide (ft.) 2.28 2.08 2.18  Station 8659665 Bowen Point. - Shallotte Inlet Station 8659414 Varnamtown - Lockwoods Folly River Island-wide Average Used for Model  Holden Beach Stormwater Master Plan Report  12    4.0 Existing Stormwater System Analysis  The existing system analysis identified stormwater system deficiencies within the areas of concern and validated known problems or deficiencies int the existing systems. The existing system was found to be undersized at several locations based on surcharges shown by the Hydraulic Grade Line (HGL)in the conveyance system (Table 4.1). The maps in Attachment D provide a visual representation of the undersized portions of the stormwater network and show  the extent oft flooding during the 2- and 10-year storm events. Area1-300 Block of Ocean Boulevard West  Several hundred feet of public right-of-way (ROW) along Ocean Boulevard West (OBW), in an area referred to as the 300 Block, experience significant floodwater retention following storm events due to a low point in the road which acts as a storage depression. This allows water to pond on the road up to a depth of -1 foot before it can overflow down the road and into the canal west of High Point Street. Ai few small underground storage pipes that allow for infiltration are present here, however, their inverts sit below the measured seasonal high-water table (SHWT) elevation and likely do not contribute significantly to 2-year storm retention. The stormwater network along Brunswick Avenue During the sunny day (ie. no rainfall) MHHW tide, the northern half of High Point St. experiences flooding however a tide gate prevents backflow into the Brunswick Avenue  W. is also undersized for the 2-year storm event.  stormwater network.  Area 2. - East End of Mullet Street Area & East End of Avenue A  Public ROW along Ocean Boulevard East (OBE) on the east end of Holden Beach, between Ferry Road and Dunescape Drive, experiences frequent periods of standing water following rain events as runoff is transported through the existing stormwater network or infiltrates into the soil. Much of this existing network is undersized for the 2- year storm event with the entire system undersized for the 10-year storm event. This network also contains a large number of pipes with negative slopes (the pipe outlet is higher than the pipe inlet) which produces inefficient flow conditions and contributes to Al lack of any stormwater infrastructure along OBE between McCray Street and Dunescape Drive contributes to the flooding in this area during the 10-year storm event though natural depressions in the existing topography appear to control the 2-year storm This area does not experience sunny day flooding due to the MHHW tide.  surcharging.  event.  Area 3. - West End Right-of-Way  The public ROW near 1338 Ocean Boulevard West experiences flooding following rain events due to al low point in the road which acts as a storage depression, allowing water  Holden Beach Stormwater Master Plan Report  13    top pond to a depth of -21 feet before it can overflow into the Intracoastal Waterway. The only stormwater network present in this area are ai few small underground storage pipes that allow fori infiltration; however, their inverts sit below the average groundwater level and likely do not contribute significantly to 2-year storm retention. This area does not experience sunny day flooding due to the MHHW tide.  Area 4- 760 Block of Ocean Boulevard West  The public ROW near 743 Ocean Boulevard West experiences flooding following rain events due to al low point in the road which acts as a storage depression, allowing water to pond to a depth of -1 foot before it can overfiow into the Intracoastal Waterway. The only stormwater network present in this area are two 12" underground storage pipes that allow for infiltration. As these pipes sit above the SHWT it is possible that they contribute to 2-year storm retention, however, due to their small size these pipes were not included This area does not experience sunny day flooding due to the MHHW tide.  in the model.  Area 5- Carolina Avenue  The public ROW near 142 Carolina Avenue experiences flooding following rain events due to a low point in the road which acts as a storage depression, allowing water to pond to a depth of -0.751 feet before it can overfiow south to Ocean Boulevard East. The only stormwater network present in this areai is a single 12" underground storage pipe that allows fori infiltration. As this pipe sits above the SHWT iti is possible that it contributes to 2-year storm retention, however, it was not included in the model due to its small size. This area does not experience sunny day flooding due to the MHHW tide.  Area 6. - Davis Street  No flooding due to storm events was reported in this area as all runoff sheet flows south down the road and into the Intracoastal Waterway. However, the low elevations at the end of the road make the final 501 feet of Davis Street susceptible to sunny day flooding The Town has also reported surface runoff erosion that may bei impacting water quality.  due to the MHHW tide.  Holden Beach! Stormwater Master Plan Report  14    Table 4.1- Existing Condition Model Results  2-YRStorm Flood Depth (t.) 5.61 1.11 5.98 0.07 5.13 5.06 0.01 6.82 0.60 6.78 0.33 6.63 5.16 1.61 6.61 1.10 10.56 0.85  10-YR Storm WSEL Flood Depth( (ft.) 5.97 1.47 6.17 0.26 5.26 5.14 0.09 7.62 1.40 7.62 1.17 7.64 0.64 5.54 1.94 6.70 1.20 10.70 1.00  Problem Area 1  Overtop Elev. WSEL 4.50 5.91 5.30 5.05 7.00 3.60 5.50 9.70  Location Ocean Boulevard West Brunswick Ave. (Start of Channel) Brunswick Ave. (Marker Fifty-Five Dr.) High Point St. at Outlet Pipe Ocean Boulevard East (West of Mullet St.) 6.22 Ocean Boulevard East (East of Mullet St.) 6.45 Ocean Boulevard East (McCray St.- Dunescape Dr.) Ocean Boulevard West Ocean Boulevard West Carolina Avenue  2 3 4 5  Holden Beach Stormwater Master Plan Report  15    5.0 Evaluation of Alternatives  Two altematives were evaluated for areas of concern 1 through 5 as identified in Chapter 4 to achieve the 2-year level of service and improve conditions during the 10-year storm. Where a 2- year level of service was not possible, alternatives sought to improve flood conditions as much Ing general, improvements consisted of hydraulic improvements such as upsizing or adding pipes and swales within the improvement area. Below is a description of the evaluated alternatives for each area of concern. Water surface elevation comparisons for each altemative are shown separately for each area of concern. A concept-level Opinion of Probable Construction Cost is Ai fact sheet was developed for each alternative that describes the existing problem, project benefits, solution, and costs ofi implementation. The fact sheets are included in this chapter, but each fact sheet is designed for standalone use for presentations or meetings with stakeholders.  as possible.  provided for each alternative and detailed in Attachment H.  Full maps of each alternative are provided in Attachment E. Area 1-: 300 Block of Ocean Boulevard West  The following alternatives for Area 1 are presented in two phases. Phase 1 seeks to provide immediate flood relief whereas Phase 2 seeks to maintain the level of service achieved by Phase 1 while allowing the Town to undertake future construction projects. Phase 2 is included int this analysis for informational purposes only and is not included in the recommendations  found in Section7 7. Alternative 1 Phase 1  A dedicated right-of-way (ROW) at 317 Brunswick Avenue West, which connects Ocean Boulevard West (OBW) and Brunswick Ave., is currently used as an unofficial vehicle and pedestrian access. Phase 1 of this alternative would see this ROW converted to a 2.5-foot-deep storage depression to hold runoff from both OBW and Brunswick Ave. Catch basins will be installed along the north side of OBW, including at the low point of the road, and at the intersection of High Point Street and Brunswick Ave. As the catch basin at the low point of the road will be located within the ROW of OBW and not on the road itself, its rim elevation will sit above the lowest elevation of the road. For this reason, iti is recommended that the road be raised to elevation 4.85' to encourage Catch basins will be connected by 15" High Performance Polypropylene pipes (HPPP), producing two different directions of flow: one, from the low point of the road, through the storage depression, and discharging at the outset of the Brunswick Ave. channel, and  positive flow to the inlet and to avoid further road ponding.  Holden Beach Stormwater Master Plan Report  16    the other from the low point of the road, down OBW and High Point Street, and discharging into the channel near the intersection of High Point St. and Brunswick Ave. In order to maintain a positive outfall within the proposed storwater network, the Brunswick. Ave. channel will be dropped approximately 1.51 feet between its outset and the inlet of the existing outlet pipe. The channel will be regraded as needed while The existing culvert under Marker Fifty-Five Drive and the existing outlet pipe running along the east side of High Point St. will both be upsized to 18" Reinforced Concrete Pipes (RCPs). The tide gate on the existing outlet pipe will be replaced. Alternative 1 Phase 1 eliminates flooding from the 2-year storm event along Brunswick Ave. and reduces flooding from the 2-year storm event along OBW. to -0.1f feet. This alternative also reduces the flood depth of the 10-year storm to 0.1 feet along The estimated construction cost of Alternative 1 Phase 1 is $450k- - $675k.  maintaining minimum side slopes of3:1.  Brunswick Ave. and -1.Ofoot along OBW.  Phase 2  This ROW area may also be suitable for use as a roadway or parking area. Should the Town wish to pave this area for such uses, the storage depression from Phase 1 could be converted to an underground storage/ infiltration system. This underground detention system was modeled after the ADS StormTech SC-310 system (AttachmentF). All other  improvements from Phase 1 would remain in place. Alternative 1 Phase 2 produces comparable results to Phase 1.  The estimated construction cost of Alternative 1 Phase 2i is $731k-$1.1 million.  Alternative: 2 Phase 1  Alternative 2 Phase 1 includes all improvements proposed in Alternative 1 Phase 1 with the addition of a second 1.5-foot-deep storage depression at 339 Brunswick Ave., another dedicated ROW. This storage depression will be connected to the proposed stormwater network on OBW and discharge north into the Brunswick Ave. channel just Alternative 2 Phase 1 solves flooding on Brunswick Ave. during both the 2-year and 10- year storm events and on OBW during the 2-year storm event. 10-year flood depths on The estimated construction cost of Alternative 2 Phase 1 is $498k-$747k.  before the Marker Fifty-Five Dr. culvert. OBW are reduced to -1.01 foot.  Holden Beach! Stormwater Master Plan Report  17    Phase 2  Alternative 2 Phase 2 includes all improvements proposed in Alternative 1 Phase 2 with the second storage depression being similarly converted into an underground storage/ infiltration system in order to accommodate a drive and/or parking. This additional underground detention system was modeled after the ADS StormTech SC-160LP Alternative 2 Phase 2 solves flooding on both Brunswick. Ave. and OBW during the 2- year storm event. 10-year flood depths are -1.01 foot on OBW and -0.1 feet on The estimated construction cost of Alternative 2 Phase 2is $1.55- $2.33 million.  system (Attachment F). Brunswick. Ave.  Table 5.1-Area 1 Results Comparison  Alternative 1 WSEL 5.00 4.74 4.55 4.50 5.87 6.09 5.25 5.16  Alternative2 WSEL 4.68 4.69 4.48 4.43 5.85 6.06 5.22 5.15  Location  Overtop Elev. 2-YEARS STORM 4.85 5.91 5.05 10-YEAR STORM 4.85 5.91 5.05  Flood Depth (ft.) 0.15  Flood Depth (ft.)  Ocean Boulevard West Brunswick Ave. (Start of Channel) Brunswick Ave. (Marker Fifty-Five Dr.) 5.30 High Point St. at Outlet Pipe Ocean Boulevard West Brunswick Ave. (Start of Channel) Brunswick Ave. (Marker Fifty-Five Dr.) 5.30 High Point St. at Outlet Pipe  1.02 0.18 0.11  1.00 0.15 0.1  Note that for both Table 5.1 above and the maps in Attachment E, only results for Phase 2 are shown as this is the anticipated final condition. Were Phase 1 to be pursued without Phase 2, results would be slightly lower, however the addition of parking in Phase 2 and the subsequent switch from above ground to underground storage, decreases the amount of storage possible.  Holden Beach Stormwater Master Plan Report  18    Area 1-A Alternative 1 Phase 1  300 Block of Ocean Boulevard West  Legend Outfall Prop. 15" Ex.Catch HPPP Basin Prop. 18" Ex. Drainage RCP Pipe Prop. Storage Ex. Drainage Depression Channel 2-YR Flood Prop. Catch Area Basin 10-YRI Flood Prop. 12" Area HDPE Parcels Flow Direction Contours  Lower ex. channel "1.5ft. andregrade  6012P0 1inch=120feet  PROBLEM  PROJECT BENEFITS  Existing road topography along the 300 Block of OBW leads This alternative eliminates flooding on Brunswick. Ave. storm. An existing stormwater system along Brunswick Ave., year storm. Flood depths on both Brunswick Ave. and just north of this area, is similarly undersized for the 2-year OBW are reduced during the 10-year storm.  tor road flooding during storm events including the 2-year  and significantiy reduces flooding on OBW during the 2-  storm. SOLUTION  PROJECT CHALLENGES  Disruption of traffic during construction Low road surface elevations limit pipe size and material options along OBW Small difference between surface elevations and SHWT limits available storage volume Estimated Construction Cost Range $450,000 to $675,000  Construct a 2.5-ft deep storage depression int the ROW at 317 Brunswick Ave. that discharges into the existing Brunswick. Ave. channel Install system of 15" HPPPS along OBW and High Point St. that discharges into the existing Brunswick Lower Brunswick Ave. channel by -1.5f feet Upsize existing Mile Marker Fifly-Five Dr. culvert and outlet pipe along High Point St. to 18" RCPs  Ave. channel  ÇOST  Holden Beach Stormwater Master Plan Report  19    Area 1- Alternative 1 Phase 2  300 Block of Ocean Boulevard West  Legend Outfall Prop. 18" Ex. Catch RCP Basin Prop. Ex. Drainage Underground Pipe Storage Ex. Orainage 2-YRI Flood Channel Area Prop. Catch 10-YR Flood Basin Area Prop. 12" Parcels HOPE Contours Prop. 15" Flow Direction HPPP Replace Phase storage depressions with underground detention/ infitration systems  60 12. linch- 120feet  PROBLEM  PROJECT BENEFITS  The solution presented in Phase 1 limits the This altemative allows for flood reduction comparable to that in Phase 1  usage of the ROW at: 317 Brunswick Ave. which may be suitable for use as roadway or beach access parking. SOLUTION  while allowing all or part of the ROW to be paved.  PROJECT CHALLENGES  Small difference between surface elevations and SHWT limits  size of underground storage High cost  Replace the storage depression at 317 Brunswick Ave. with an underground storage/ infiltration system (StormTech SC-310or similar) that discharges into the existing Brunswick Ave. channel  COST  Estimated Construction Cost Range $731,000 to $1,096,500  Holden Beach Stormwater Master Plan Report  20    Area 1- Alternative 2 Phase1  300 Block of Ocean Boulevard West  Legend Prop. 8" KDPE Prop. 12" Prop. 15" Prop. 18" Parcels Flow Direction  Outfall Ex. Catch Basin Ex. Drainage MDPE Pipe Ex. Drainage HPPP Channel Prop. Catch RCP Basin  Prop. Storage Depression 2-YR Flood Area 10-YRI Flood Area Contours  channel 1.5n. and regrade  PROBLEM  PROJECT BENEFITS  Existing road topography along the 300 Block of OBW leads This alternative eliminates flooding on OBW during storm. An existing stormwater system along Brunswick. Ave., both the 2-year and 10-year storms. Flood depths  to road flooding during storm events including the 2-year just north of this area, is similarly undersized for the 2-year  the 2-year storm and on Brunswick Ave. during on OBW are reduced during the 10-year storm.  storm. SOLUTION  PROJECT CHALLENGES  Disruption of traffic during construction Low road surface elevations limit pipe size and material options along OBW Small difference between surface elevations and SHWT limits available storage volume Estimated Construction Cost Range $498,000 to $747,000  Construct storage depressions on the ROWS at 317 Brunswick. Ave. (2.5-ft-deep) and 339 Brunswick Ave. (1.5-f-deep) that discharge into the existing Brunswick Ave. channel Install a system of 15" HPPPS along OBW and High Point St. that discharges into the existing Brunswick Ave. channel Lower Brunswick. Ave. channel by -1.5f feet Upsize existing Mile Marker Fifty-Five Or. culvert and outlet pipe along High Point St. to 18" RCPs  COST  Holden Beach Stormwater Master Plan Report  21    Area1- Alternative 2 Phase 2  300 Block of Ocean Boulevard West  Legend Prop. 8" HDPE Prop. 12* Prop. 15" Area Prop. 18" Flow Direction Contours Replace Phase storage depressions with underground detention/ Infiltration systems  A Outfall Ex. Catch Basin Ex. Drainage HDPE Pipe Ex. Drainage HPPP Channel Prop. Catch RCP Basin  Prop. au Underground Storage 2-YRI Flood 10-YR Flood Area Parcels  601290 linch-120feet  PROBLEM  PROJECT BENEFITS  The solution presented in Phase 1 limits the usage This altemative allows for flood reduction comparable to that of the ROWS at 317 and 339 Brunswick Ave. which in Phase 1 while allowing all or part of the ROW to be paved.  may be suitable for use as roadway or beach  access parking. SOLUTION  PROJECT CHALLENGES  Small difference between surface elevations and SHWT limits size of underground storage  Replace the storage depressions with underground storage/ infiltration systems at 317 (StormTech SC-310 or similar) and 339 Brunswick Ave. (StormTech SC-160LP or similar) that discharge into the existing Brunswick Ave. channel  High cost  COST  Estimated Construction Cost Range $1,550,000 to $2,325,000  Holden Beach Stormwater Master Plan Report  22    Area 2. - East End of Mullet Street Area & East End of Avenue A  Alternative 1  The existing stormwater network along Ocean Boulevard East (OBE) west of! Mullet Street will remain with individual pipe inverts dropped as needed to create positive drainage within the system. Existing pipes along OBE east of Mullet St. will be upsized to 24" RCPS with the final of these pipes upsized to a 30" RCP. In order to accommodate the burial of the new 24" RCP, the existing channel at the upstream end of this pipe system will be dropped by -0.5 feet and regraded as needed while maintaining a Similarly, the existing pipe under Blockade Runner Drive will be upsized to an 18" RCP with its downstream pipe that runs under OBE upsized to a 24" RCP. All pipes along Mullet St. will be upsized to 30" RCPs and a tide gate will bei installed on the final outlet pipe. These are the largest pipe sizes that can reasonably fit underneath the road while Alternative 1 solves flooding from the 2-year storm east of Mullet St. and reduces the 2- year flood depth west of Mullet St. to -0.5 feet. This alternative also reduces the flood depth of the 10-year storm to -0.7 foot between Halstead St. and McCray St. and to  minimum side slope of3 3:1.  maintaining necessary clearance.  -0.25 feet between Avenue A and Dunescape Dr.  The estimated construction cost of Alternative 1 is $650k-$975k.  Alternative 2  Alternative 2i includes alli improvements from Alternative 1. Additionally, three (3) 1-foot- deep swales with 4:1 side slopes will bei installed along the northern ROW of OBE between McCray Street and Dunescape Drive. 12" HPPP culverts will be installed under roadways to connect the swales and tie them to the existing system. Alternative 2 produces similar results to Alternative 1, slightly increasing the 10-year flood depth on OBE but providing additional storage capacity along OBE between McCray St. and Dunescape Dr. that is not currently available and eliminating road flooding during the 10-year storm in the same aforementioned area. The estimated construction cost of Alternative 2 is $808k -$1.21 million.  Due to the Coastal Area Management Act (CAMA), improvement options in this area are limited.  Holden Beach Stormwater Master Plan Report  23    Table 5.2- - Area 2 Results Comparison  Alternative1 Flood Depth (ft.) 0.46  Alternative2 Flood WSEL Depth (ft.) 6.68 0.46 5.33 6.63 7.33 7.33 7.25  Location  Overtop Elev. WSEL 2-YEARSTORM 7.00 10-YEAR STORM  Ocean Boulevard East (West of Mullet St.) 6.22 Ocean Boulevard East (East of Mullet St.) 6.45 Ocean Boulevard East (McCray St.- Dunescape Dr.)  6.68 5.33 6.63 7.26 7.25 7.26  Ocean Boulevard East (West of Mullet St.) 6.22 Ocean Boulevard East (East of Mullet St.) 6.45 Ocean Boulevard East (McCray St.- Dunescape Dr.)  1.04 0.80 0.26  1.11 0.88 0.25  7.00  Holden Beach Stormwater Master Plan Report  24    Area 2-Alternative! 1  East End of Mullet Street & East End of Avenue A  Legend Outfall Prop. 24" Ex. Catch RCP Basin Prop. 30" Ex. Drainage RCP Pipe 2-YR Flood Ex. Drainage Area Channel 10-YR Flood Prop. 18" Area RCP Parcels Contours  Lower ex. pipel inverts west ofMullets Sta asneeded tocreate positive slope  Lower ex. channel "0.5R. andr regrade  87.5175. linch- 175feet  PROBLEM  PROJECT BENEFITS  Portions of the existing stormwater network along Ocean Boulevard East This altemative eliminates flooding on OBE undersized for the 10-year storm. Some pipes within the existing network reduces flooding west of Mullet St. Flood  (OBE) are undersized for the 2-year storm with the entire system were installed at a negative slope, leading to water retention and surcharging. Al lack of stormwater infrastructure along OBE between McCray St. and Dunescape Dr. leads to roadway flooding in this area during  east of Mullet St. during the 2-year storm and depths during the 10-year storm are similarly reduced across the entire problem area. PROJECT CHALLENGES Disruption of traffic during construction Low road surface elevations limit pipe size options along OBE Estimated Construction Cost Range $650,000 to $975,000  the 10-year storm. SOLUTION  Drop inverts of existing pipes along OBE west of Mullet St. as Upsize existing pipes along OBE east of Mullet St. to 24" RCPs Drop existing channel on east side of system by -0.5 feet and Upsize pipes at Blockade Runner Dr. to an 18" RCP (upstream- Upsize existing pipes on Mullet St. to 30" RCPs Install a tide gate on the final outlet pipe  needed to create a positive outfall  COST  regrade most) and 24" RCP  Holden Beach Stormwater Master Plan Report  25    Area 2- Alternative 2  East End of Mullet Street & East End of Avenue A  Legend Outfall Prop. 24" Ex. Catch RCP Basin Prop. 30" Ex. Drainage RCP Pipe Prop. Ex. Drainage Channel Channel 2-YR Flood Prop. 12" Area HPPP 10-YR Flood Prop. 18" Area RCP Parcels Contours  ofMulet ex, pipe St. as linverts needed west tocreate positive slope  -05R. Lower ex. and channel regrade  Prop. Cannel 'Depth, 4:15S PROJECT BENEFITS  875175. linch-175feet  PROBLEM  Portions of the existing stormwater network along Ocean Boulevard East This altemative eliminates flooding on OBE east and surcharging. A lack of stormwater infrastructure along OBE between the entire problem area and roadway flooding McCray St. and Dunescape Dr. leads to roadway flooding in this area between Avenue A and Dunescape Dr. is  (OBE) are undersized for the 2-year storm with the entire system undersized for the 10-year storm. Some pipes within the existing network were installed at a negative slope, leading to water retention  ofMullet St. during the 2-year storm and reduces flooding west of Mullet St. Flood depths during the 10-year storm are similarly reduced across  during the 10-year storm. SOLUTION  eliminated. PROJECT CHALLENGES  Drop inverts of existing pipes along OBE west of Mullet St. as Install 1-foot-deep swales along OBE between McCray St. and Dunescape Dr., connected tot the existing system by 12" HPPPS Upsize existing pipes along OBE east of Mullet St. to 24" RCPS Drop existing channel on east side of system by -0.51 feet and Upsize pipes at Blockade Runner Dr. to an 18" RCP (upstream- Upsize existing pipes on Mullet St. to 30" RCPs Install a tide gate on the final outlet pipe  Disruption oft traffic during construction Low road surface elevations limit pipe size options along OBE New stormwater system options are limited without a CAMA permit Estimated Construction Cost Range $808,000 I to $1,212,000  needed to create a positive outfall  regrade most) and 24" RCP  COST  Holden Beach Stormwater Master Plan Report  26    Area 3. - West End Right-of-Way Alternative 1  Inlets will be installed on the north side of Ocean Boulevard West (OBW) with at least one (1)at the low point of the road. Inlets will be connected by 12" HPPPS. A 12"RCP will discharge this system through a public utility easement acquisition, adequate public ROW location, or other secured point of outfall, into the Intracoastal Waterway. Catch Alternative 1 reduces flooding during the 2-year storm event to -0.41 feet and during the 10-year storm event to -1.2 feet. These results are approximate and may change  basins will have open bottoms to allow for infiltration.  depending on the outfall location chosen.  The estimated construction cost of Alternative 1 is $120k-$ $241k.  Alternative 2  Inlets will be installed on the north side of Ocean Boulevard West (OBW) with at least one (1) at the low point of the road and one inside the ROW in front of 1330OBW. These inlets will be connected by 12" HPPPS. An 18" RCP outlet pipe will discharge this system through a public utility easement acquisition, adequate public ROW location, or other secured point of outfall, into the Intracoastal Waterway. Catch basins will have Alternative 2r reduces flooding during the 2-year storm event to -0.8 feet and during the  open bottoms to allow fori infiltration. 10-year storm event to -1.51 feet.  The estimated construction cost of Alternative 2 is $212k-$ $378k.  Due to the low elevation of the road (elevation 3.6'), options for pipe size and material are limited for both alternatives. A 12" HPPP is the largest pipe that allows for both a positive pipe slope to the outfall and sufficient pipe clearance under the road. Both alternatives will require acquisition of a CAMA permit in order to create a new outfall. New outfalls are feasible as a CAMA major permit. These are evaluated on a case-by-case basis and may require some form  of water quality treatment. Table 5.3. -Area 3 Results Comparison  Alternative: 1  Alternative 2  Location Ocean Boulevard West  Storm Overtop 2-year 10-year  Elev. WSEL Flood Depth (ft.) WSEL Flood Depth (ft.)  3.97 4.76  0.37 1.16  4.42 5.13  0.82 1.53  3.60  Holden Beach Stormwater Master Plan Report  27    Area 3- Alternative 1  West End ROW Legend Ex. Catch 2-YR Flood Basin Area Ex. Drainage 10-YRI Flood Pipe Area Prop. Catch Parcels Basin Contours Prop. 12" Potential HPPP OutfallArea  CBatlow polnt of road regardless ofc chosen outfall  37.575. 1Inch=75feet  PROBLEM  PROJECT BENEFITS  Existing road topography of OBW near 1338 including the 2-year storm. The currenti infiltration system is unable to handle these storms and there is no way to drain the road in case of an  This altemative better reduces flooding along OBW during both the 2-  OBW leads to roadi flooding during storm events year and 10-year storms.  PROJECT CHALLENGES  emergency. SOLUTION  Disruption of traffic during construction Low road surface elevations limit pipe size and material options New stormwater outfalls require a CAMA permit May require easement acquisition  along OBW  Install catch basins within ROW of OBW, including at the low point of the road Install 12" HPPPS to connect catch Install 12" RCP to discharge through easement: location to be chosen by  COST  basins Town  Estimated Construction Cost Range $120,500 to $240,750  Holden Beach Stormwater Master Plan Report  28    Area3 - Alternative 2  West End ROW Legend Ex. Catch 2-YR Flood Basin Area Ex. Drainage 10-YR Flood Pipe Area Prop. Catch Parcels Basin Contours Prop. 12" Potential HPPP OutfallArea  37.575 linch=75feet  PROBLEM  PROJECT BENEFITS  Existing road topography of OBW near 1338 including the 2-year storm. The current infiltration system is unable to handle these storms and there is no way to drain the roadi in case of an emergency. SOLUTION  This altemative somewhat reduces flooding along OBW during both the  OBWI leads to road flooding during storm events 2-year and 10-year storms.  PROJECT CHALLENGES  Disruption of traffic during construction Low road surface elevations limit pipe size and material options New stormwater outfalls require a CAMA permit May require easement acquisition Outfall is within a storage depression that allows backflow into  along OBW system COST  Install catch basins within ROW of OBW, including at thel low point of the road and in front of 1330 OBW Install 12" HPPPS to connect catch Install 18" RCP to discharge through easement - location to be chosen by  basins Town  Estimated Construction Cost Range $212,000 to $378,000  Holden Beach Stormwater Master Plan Report  29    Area 4. - 760 Block of Ocean Boulevard West  Alternative 1  Inlets will be installed along the northern edge of Ocean Boulevard West (OBW)with at least one (1)at the low point of the road which will connect to the existing catch basin on the south side of OBW via a 15" RCP. Proposed inlets will be connected via 24" RCPs. A24" RCP will discharge this system through a public utility easement acquisition, adequate public ROW location, or other secured point of outfall, into the Intracoastal Alternative 1 solves flooding from the 2-year storm event and reduces flood depths from These results are approximate and may change depending on the outfall location The estimated construction cost of Alternative 1 is $149k-$473k.  Waterway.  the 10-year storm event to -0.7 feet.  chosen. Alternative?  Four inlets will be installed along the northem edge of Ocean Blvd. at -200-foot intervals, starting at the low point of the road and running just past 762 OBW. A1 15" RCP will bei installed to connect this system to the existing catch basin on the south side of OBW. A2 24" RCP will connect the remaining inlets and turn northwest to discharge into Alternative 2 also solves flooding from the 2-year storm event and reduces flood depths This alternative would avoid either easement or property acquisition but would not provide as much reduction in flood depths from the 10-year storm. The estimated construction cost of Alternative 2 is $273k-$409k.  the Intracoastal Waterway.  from the 10-year storm event to -1.31 feet.  Both alternatives will require acquisition of a CAMA permit in order to create a new outfall. New outfalls are feasible as a CAMA major permit. These are evaluated on a case-by-case basis and  may require some form of water quality treatment. Table 5.4. -Area 4 Results Comparison  Alternative1  Alternative2  Location Ocean Boulevard West  Storm Overtop 2-year 10-year  Elev. WSEL Flood Depth (ft.) WSEL Flood Depth (ft.)  4.39 5.81  4.89 6.35  5.09  0.72  1.26  Holden Beach Stormwater Master Plan Report  30    Area 4- Alternative: 1  760 Block of Ocean Boulevard' West  Legend Ex. Catch Prop. 24" Basin RCP Ex. Drainage 10-YR Flood Pipe Area Prop. Catch Parcels Basin Contours Prop. 15" Polential RCP OutfallArea  CBatlow froad regardless chosen outfal  60_12Pe linch-120feet  PROBLEM  PROJECT BENEFITS year storm. PROJECT CHALLENGES  Existing road topography in the 760 block of OBW leads to This alternative eliminates flooding along OBW during the road flooding during storm events including the 2-year storm. 2-year storm and better reduces flooding during the 10-  The current infiltration system is unable to handle these storms and there is no way to drain the road in case of an  emergency. SOLUTION  Disruption of traffic during construction New stormwater outfalls require a CAMA permit May require easement or property acquisition Estimated Construction Cost Range $148,500 to $472,750  Install catch basins within ROW of OBW, including at Install 15" RCP to connect existing catch basin to Install 24" RCPs to connect proposed catch basins and discharge through easement or property - location to be chosen by Town  thel low point of the road proposed system  COST  Holden Beach! Stormwater Master Plan Report  31    Area 4- Alternative: 2  760 Block of Ocean Boulevard West  Legend New Outfall Prop. 24" Ex. Catch RCP Basin 2-YR Flood Ex. Drainage Area Pipe 10-YR Flood Prop. Catch Area Basin Parcels Prop. 15" Contours RCP  60129 1inch-120feet  PROBLEM  PROJECT BENEFITS  Existing road topography int the 760 block of OBW the 2-year storm. The current infiltration system is unable to handle these storms and there is no way to drain the road in case of an emergency.  This altemative eliminates flooding along OBW during the 2- storm, It does not require easement or property acquisition.  leads to road flooding during storm events including year storm and somewhat reduces flooding during the 10-year  PROJECT CHALLENGES  SOLUTION  Disruption of traffic during construction New stormwater outfalls require a CAMA permit  Install catch basins within ROW of OBW from low point of the road to 762 OBW install 15" RCP to connect existing catch basin to proposed system Install 24" RCPs to connect catch basins and discharge into Intracoastal Waterway  COST  Estimated Construction Cost Range $272,500 to $408,750  Holden Beach Stormwater Master Plan Report  32    Area 5- Carolina Avenue Alternative 1  Two inlets will be installed, one on the north side of Carolina Avenue at the low point of the road and another in the parking lot of Halstead Park. These inlets will be connected via 30" RCPS with junction boxes att the intersections of Carolina Ave. & Halstead St. and Halstead St. & Southshore Dr. to facilitate pipe elevation and direction changes. A 30" RCP will also connect the first proposed inlet to the existing catch basin on the south The inlet in the parking lot of Halstead Park will also act as the outflow, with water leaving the system by bubbling up out of the inlet and sheet flowing over the parking lot This alternative solves flooding from both the 2-year and 10-year storm events without  side of Carolina Ave.  and into the Intracoastal Waterway. requiring a CAMA permit. Alternative 2  The estimated construction cost of Alternative 1 is $207k-$310k.  This alternative utilizes the same pipe and structure layout as Altemative 1 but using a 24" RCP instead ofa a 30" RCP and installing an outlet pipe from the final inlet that discharges into the Intracoastal Waterway. While this altemative is more hydraulically efficient, providing a higher level of service and eliminating discharge within a parking area as depicted in Alternative 1, it will create a new stormwater outlet and thus require a CAMA permit. New outfalls are feasible as a CAMA major permit. These are evaluated on a case-by-case basis and may require some form of water quality treatment. This alternative solves flooding from both the 2-year and 10-year stor events. The estimated construction cost of Alternative 1i is $205k-$327k.  Table 5.5. -Area 5 Results Comparison  Alternative1  Alternative2  Location Carolina Avenue  Storm Overtop 2-year 10-year  Elev. WSEL Flood Depth (ft.) WSEL Flood Depth (ft.)  8.71 9.43  7.48 8.40  9.70  Holden Beach Stormwater Master Plan Report  33    Area! 5-A Alternative: 1  Carolina Avenue Legend Ex. Catch Prop. 30" Basin RCP Ex. Drainage 2-YR Flood Area Pipe Prop. Catch 10-YR Flood Basin Area Prop. Parcels Junction Box Contours  CBtob bubble upa ando discharge vias sheet flow over parking! lot  Cctana  Duumsatohut  03757500 1inch-75feet  PROBLEM  PROJECT BENEFITS  Existing road topography: along Carolina This altemative eliminates flooding along Carolina Ave. during the 2-year and 10-  Ave. east of Halstead St. leads to road flooding during storm events including the 2-year storm. The current infiltration system is unable to handle these storms.  year storms without the need for a CAMA permit.  PROJECT CHALLENGES  Disruption of traffic during construction  SOLUTION  Creates flooding across Southshore Dr. during the 10-year storm and through the Halstead Park parking lot during both the 2-year and 10-year  Install catch basins and junction boxes within ROW of Carolina Ave. and Halstead St. Install 30" RCPs to connect existing and proposed structures  storms. COST  Estimated Construction Cost Range $206,500 to $309,750  Holden Beach Stormwater Master Plan Report  34    Area! 5-A Alternative: 2  Carolina Avenue Legend New Outfall Prop. Ex. Catch Basin Ex.D Drainage RCP Pipe Prop. Catch Basin  Junction Box Prop. 24" Parcels Contours  Qunctoaol  37.5_75 Linch=75feet  PROBLEM  PROJECT BENEFITS 10-year storms. PROJECT CHALLENGES  Existing road topography along Carolina This alternative eliminates flooding along Carolina. Ave. during both the 2-year and  Ave. east of Halstead St. leads to road flooding during storm events including the 2-year storm. The current infiltration system is unable to handle these storms.  Disruption of traffic during construction New stormwater outfalls require a CAMA permit  SOLUTION  Install catch basins and junction COST boxes within ROW of Carolina Ave. and Halstead St. Install 24" RCPs to connect existing and proposed structures and discharge into the Intracoastal Waterway  Estimated Construction Cost Range $204,500 $327,200  to  Holden Beach Stormwater Master Plan Report  35    6.0 Stormwater Project Recommendations  The following is a summary of the recommended alternative for each area of concem based on the extent of improvements, implementation cost, ease ofi implementation, and overall net benefit, followed by a tabulation of the estimated cost for each (Table 6.1). The recommended solutions are noti interdependent, therefore the Town could implement any of the recommended solutions at any time, depending on funding availability, easement and/or property acquisition, and coordination with stakeholders (e.g. NCDOT).  Area 1-3 300 Block of OBW  Several hundred feet of public ROW along Ocean Boulevard West (OBW), in an area referred to as the 300 Block, and Brunswick Avenue to the north, experience significant floodwater retention following storm events. As previously mentioned in Section 5, only Phase 1 of these Alternative 1 Phase 1 would eliminate 2-year flooding along Brunswick Ave. while reducing 2- year flood depths on Brunswick Ave. and 10-year flood depths across the entire area. Alternative 2 Phase 1 would eliminate 2-year flooding across the entire area and 10-year flooding on Brunswick Ave. while reducing 10-year flooding on OBW. As the only difference between the alternatives is the addition of a second storage depression in Alternative 2 which does not significantly increase expected construction costs, Alternative 2 Phase 1 is recommended in order to achieve a 2-year level of service across the entire area  alternatives is recommended in this report.  and a 10-year level of service along Brunswick Ave. Area 2- East End of Mullet Street & East End of Avenue A  Public ROW along Ocean Boulevard East (OBE) on the east end of Holden Beach, between Ferry Road and Dunescape Drive, experiences frequent periods of standing water following rain events as runoff is transported through the existing stormwater network or infiltrates into the soil. Both alternatives involve upsizing the existing stormwater system such that a 2-year level of service is achieved in the section of OBE east of Mullet St. and the entire area sees a reduction int flood depths due to both 2-year and 10-year storms. Alternative 2 further reduces flooding from the 10-year storm by eliminating roadway flooding along OBE between Avenue A and Despite its slightly higher cost, Alternative 2 is therefore recommended for its higher level of  Dunescape Dr. improvement. Area 3-West End ROW  The public ROW near 1338 Ocean Boulevard West experiences flooding following storm events. Both alternatives would improve flood conditions during both the 2- and 10-year storms.  Holden Beach Stormwater Master Plan Report  36    Alternative 1 produces al better chance of successful flood drawdown as it allows for less piping, and therefore a steeper slope and higher pipe capacity, to reach an outfall in the Intracoastal Waterway. As iti is also the lower cost option, Alternative 1 is recommended, with future survey  needed to identify an appropriate outfall location. Area 4- 760 Block of Ocean Boulevard West  The public ROW near 743 Ocean Boulevard West experiences flooding following storm events. Both alternatives will solve flooding from the 2-year storm with Alternative 1 being more effective at draining the 10-year storm due to its steeper pipe slope. However, the cost of property acquisition is likely not worth the small improvement in system efficiency. Therefore, Altemative 2 is recommended, with future survey needed to identify an appropriate outfall location.  Area 5- Carolina Avenue  The public ROW near 142 Carolina Avenue experiences flooding following storm events. Both Alternative 2 is the more hydraulically efficient option, providing a higher level of service without requiring localized flooding, therefore it is recommended despite higher costs due to permitting. While no flooding was reported in this area, the Town has reported surface runoff erosion that may bei impacting water quality. In order to catch sediment before it reaches the nearby Intracoastal Waterway, the installation of a grassed blind swale/detention area and possible level spreader at the end of Davis St. is recommended, with existing outfall piping retrofits  alternatives would eliminate flooding from both 2-year and 10-year storms.  Area 6- Davis Street  suitable for proper operation. Table 6.1. Summary of Selected Alternatives  Project Area 1 2 3 4 5 6  Selected Alternative 2 2 1 2 2  Project Description 300 Block OBW West End ROW 760 Block OBW Carolina Ave Davis St  Cost Estimate $498k-$747k $808k : $1.21 million $121k - $241k $273k-s $409k $204k-$ $327k $17.5k-$26.25k  East End Mullet St. & East End Avenue A  Holden Beach Stormwater Master Plan Report  37    8  4 5 3 s o o o  6  2 3  6    DB  5 0  5 s 15 o or o 00  s e  00 1 u 6 0 d  5 u 0  7 8  9  2    9  0  2 ]s 4 0 0  0 0  a N 8 W     8.0 Stormwater Utility Feasibility Assessment  At financial model specific to the proposed Holden Beach Storm Water Utility (SWU) was developed using expected expenses for administration, operation, maintenance, and capital projects provided by the Town. Costs associated with each of these functions were used to determine the overall revenue requirements of the utility. User charges required to meet these revenue needs were developed on a monthly per parcel basis. Revenue and expenses were then projected for a period of 10 years based on customer growth rate, inflation, etc., to geta  sense of the utility's potential viability.  8.1 Revenue  Revenue is determined using a flat fee amount per month for each parcel, which is a typical methodology for a number of Stormwater Utilities in North Carolina. The financial model uses $7.20 per developed parcel. This compares to four (4) stormwater utilities in coastal communities within approximately 30 miles that charge at flat fee. The median value of these utilities (Oak Island, Kure Beach, Carolina Beach, and Wilmington) charged for residential properties based on al building lot with approximately 3,000 square feet ofi impervious surface is  $11.76. Jurisdiction Flat Fee Oak Island Kure Beach Carolina Beach Willmington Median  Table 8.1 Coastal Communities with Stormwater Utilities using Flat Rates  $7.04 $15.00 $17.00 $8.51 $11.76  Revenue transferred from the Town's General Fund required for startup of the proposed stormwater utility is anticipated in the amount of $300,000. This amount is repaid to the General The model allows revenue generation to be adjusted based on changes to input and assumption entries to create various scenarios for evaluation. The values used for alternate The Town requested an alternate scenario (Scenario B) that assumes USACE Federal 5113 funding is secured and therefore reduces the cost of each capital improvement project by 75%.  Fund at year 10-year of the planning period (FY34).  scenarios are listed with the description of each model scenario. All other assumptions and inputs remain constant in Scenario B.  8.2 Expenses  Expenses include ongoing costs for personnel, operations, maintenance, capital investment, debt service, transfers, and contingency as applicable. Repayment of the startup funding contribution is anticipated to begin in FY26, and transfers will continue to complete full  Holden Beach Stormwater Master Plan Report  41    repayment in FY34. The costs for personnel, operations, maintenance, and capital investment have all been developed in collaboration with Holden Beach management staff. Capital Improvements are funded using available stormwater utility resources including available Fund Balance, Sinking Fund, debt issues as necessary, and/or external sources (grants, legislative appropriation, etc.). Fund Balance is managed to maintain a minimum of90 days of Cash on Hand. Transfers to the Sinking Fund are determined by the funding amount(s) required for specific future capital investments, i.e. construction projects, specialized equipment, The model allows expense forecasts to be adjusted based on changes to input and assumption entries to create various scenarios for evaluation. The values used for these inputs are listed in  etc., and/or available net income generated by utility user fees.  Table 8.2. 8.30 Utility Scenarios  Two stormwater utility scenarios were created for the Town's consideration using thei inputs and Scenario A assumes 100% of the projected capital investment needs are funded by user fees Scenario B assumes 75% oft the projected capital investment needs are funded using US Army The model allows for adjustments to be made to each input and assumption to see the effect of each potential change and quantifies the resulting outcomes for evaluation of the utility's viability  assumptions shown in Tables 8.2 and 8.3. generated by the stormwater utility.  Corps of Engineers (USACE) Environmental Infrastructure Assistance.  and sustainability.  Holden Beach Stormwater Master Plan Report  42    Table 8.2-Summary of Financial Model Scenario Inputs & Assumptions  Model Parameters  Scenario A  Scenario B  Developed Parcels  3,617 $7.20 0.2% 4.5% 2.5%  3,617 $5.30 0.2% 4.5% 2.5% USACE 75% User Fees 25% 5-Years  Inputs Initial Monthly Fee: Per Parcel Basis  Developed Parcel growth rate (annual) Inflation: Personnel/Labor Inflation: Other operating expenses Capital Improvements Funding Source(s)  User Fees 100%  20-Years  Assumptions Debt Issues: Bank Loan Terms  4.25% Interest 5.25% Interest  Sinking Fund Target per 5-year cycle Fund Balance Target: Min. Days Cash on  $200,000  $400,000  90  90  Hand  Table 8.3. - Financial Model Scenario Output Summary Tables: 5-Year Snapshot  Scenario A - Model Outputs and Tracking  Parameter Per-Parcel Monthly Fee Fund Balance Days Cash on Hand Parameter Per-Parcel Monthly Fee Fund Balance Days Cash on Hand  Year 1 $7.20 1,076 Year1 $5.30 882  Year2 $7.40 821 Year 2 $5.40 546  Year 3 $7.60 678 Year3 $5.60 613  Year 4 $7.80 435 Year4 $5.70 356  Year 5 $7.90 276 Year 5 $5.90 195  Sinking Fund Balance $ 62,000 $ 124,000 $ 154,000 $ 214,000 $ 269,000  $ 458,000 $ 540,000 $ 567,000 $ 494,000 $ 362,000  Scenario B - Model Outputs and Tracking  Sinking Fund Balance $ 62,000 $ 124,000 $ 154,000 $ 224,000 $ 299,000  $ 375,000 $ 366,000 $ 382,000 $ 312,000 $ 199,000  *See Attachment Ifor 10-Year Expanded Table  Holden Beach Stormwater Master Plan Report  43    8.4 Model Outcomes  Model outcomes are presented in a series of data tables (Attachment I) including a summary chart showing a 10-year projection ofr revenue, expenses, user fee adjustments, financial outcomes (neti income), effect on user fees, financial indicator (benchmark) and capital improvements plan (CIP). Definitions of each of the model outcome parameters are as follows:  Revenue and Expenses  Revenue data is presented in the following three (3) general categories: 1.Operating Revenue Base User Fee: Represents revenue generated by initial stormwater utility user fees and increases by the addition of parcels over time. 2. New Revenue - Fee Adjustments: Revenue generated by projected user fee increases that are based on a 2.5% annual rate of inflation. 3. Total Projected Revenue: The sum of the former revenue categories. Expenses are presented in the following four (4) general categories:  1. Cash Financed Capital Improvements Plan (CIP): Capital projects that are funded 2. Projected Debt Service: Projected principal and interest payments on debt incurred to 3. Existing Debt Service: Principal and interest payments on debti incurred in years prior 4. Operating Expenses: The remaining costs to operate and maintain the stormwater  using available utility fund equity (cash). fund capital improvements. to the financial model.  utility.  Percent Increase Applied (assumed at 2.5%). Financial Outcomes  Tracks overall revenue percentage adjustments needed to keep pace with inflation  Tracks total annual revenue less expenses and the difference or shortage (positive or  net income) for each year.  Holden Beach Stormwater Master Plan Report  44    Effect on User Fees  Tracks the net monthly fee for each customer class (residential and commercial) and  dollar-amount adjustments as they occur.  Financial Indicators  Track the general sufficiency of revenue over expenses. Fund Balance Tracker reports available cash for the beginning of each fiscal year and is an indication of the general stability of the utility. Days Cash on Hand shows number of days that fund balance (cash) would cover expenses in the absence of operating revenue (user fees). Values consistently above the target of 90 days indicate effective overall management of the  utility. Summary Chart  Graphic display oft the data described above, showing the relationships between various types of revenue and expenses, and providing a general indication of anticipated  revenue and expense trending over time.  Capital Investment  Summarizes the cost and timing of capital projects over the 10-year planning period.  8.5 Recommendations  Based on the project cost of capital stormwater projects and on-going and planned maintenance for the stormwater system we recommend proceeding with implementation of Scenario A. This scenario provides sufficient funds to cover the planned activities for the next ten years while maintaining a sufficient fund balance that suggests the utility will remain stable and fiscally healthy. If pursuit of grant funding is favorable, the utility can easily be converted to Scenario B  in thei future and rates reevaluated att that time.  Holden Beach Stormwater Master Plan Report  45    REFERENCES  2023-24 UNC School of Govemment, Environmental Finance Center NC Residential Stormwater Utility Fee Dashboard https/etc.sog.uncedunestormwater-dashboard' ECS Southeast LLC, Report of Seasonal High Water Table Estimation and Infiltration Testing: Ocean Boulevard Driveway, ESC Project No. 49.22774, April 5, 2024 NOAA's National Weather Service Precipitation Frequency Data Server htps/ndc.nws.noagovhdselptospies map cont.htm17bkmrk-nc https/lidesandcurrents.noaa.govstations.htmi2lvpe-Datums  NC Spatial Data Download httpsi/Isdd.nc.gov  NOAA's Tides & Currents Tidal Datums  United States Department of Agriculture, Natural Resources Conservation Service, Web Soil Survey ntips/Awebsolsurveysc.egovusda. QOV/App/WebSoilSurveyaspx USGS, National Land Cover Database nttps/www.usgs.glenterserossccience/national. and-cover-database7gt-science. center obiects-0Hat-science center objects Urban Hydrology for Small Watersheds, Technical Release 55, United States Department of  Agriculture, June 1986  Holden Beach! Stormwater Master Plan Report  46    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix A  As-Built Survey &  Stormwater Network Map  MCGILL ASSOCIATES5400 TRINITY ROAD, SUITE 107, RALEIGH, NC27607/99378911, /MCGILLASSOGATESCOM    "  C 5  > - 3  &s  FOR:  COASTALGEOMATICS  TOWNG OFHOLDEN. BEACH HOLDEN BEACH, NORTHCAROLINA    SHS IS3NH HOMV  MOTB TS 3N  BLOCKADE RUNNER  DUNESCAPE DRVE   TOPOGRAPHIC AND. STORMSEWER ASBUILT SURVEYFOR: TOWN OF HOLDEN BEACH  COASTALGEOMATICS    MOBB ZS. 3Nn HOMI  s ,  CONCH STREET  EFERRY ROAD  STREET  HOLDEN STREET  STRE  SHRIMP STREET  BENDIGO STREET  CRAB  FERRY ROAD  3  TOPOGRAPHIC  COASTALGEOMATICS  TOWN OF HOLDEN BEACH  LAND    FERRY ROAD  TOPOGRAPHIC ANDS STORMSEWER ASBUILT SURVEY FOR: TOWN OF HOLDEN. BEACH  COASTALGEOMATICS    1SV3 OA3INOBNN  8S  UNE FSEE BELON  :  TOPOGRAPHIC  ASBUILT  COASTALGEOMATICS  TOWN OFHOLDEN BEACH    DAVS STREET CVO8 HOV38  GCIGRIGRON  BRUNSWICK AVE  COLE STRET  TOPOGRAPHIC ANDSTORMSEWER. ASBUILTS SURVEYF FOR: TOWN OF HOLDEN BEACH  COASTALGEOMATICS  LAND    r  3AN3AV XOIWSNA88  TOPOGRAPHIC ANDSTORMSEWER ASBUILTSURVEYF FOR: TOWNO OF HOLDEN. BEACH  COASTALGEOMATICS      * * *  3N80 3NAIG3N *  * * *  0A18 N300-9111 uS   *   :  oen    SAILOR STREET  * * * * ASBUILTS SURVEY FOR:  :  TOPOGRAPHIC. ANDS  COASTALGEOMATICS  TOWN OF HOLDEN BEACH    CHARLLOTTE SIREET  ORT  HICHPOINT STREET  MATCH  SHEET 00F1  SEE SHEET  DURHAM STREET  TOPOGRAPHIC/ ANDS  ASBUILT  FOR:  COASTALGEOMATICS  TOWNOFHOLDEN, BEACH    S3M OABN300-9111 WS  SCOTCH BONNET DRIVE  1  GREENSBORO STREET  TOPOGRAPHIC AND: STORMSEWER. ASBUILT SURVEYF FOR: TOWN OF HOLDEN BEACH  COASTALGEOMATICS      TOPOGRAPHIC ANDSTORMSEWER. ASBUILT SURVEY FOR: TOWN OF HOLDEN BEACH  COASTALGEOMATICS  LAND    1S3N ONB MB2-911 85  TOPOGRAPHIC. ANDSTORMSEWER. ASBUILT SURVEYFOR: TOWN OFHOLDEN BEACH  COASTALGEOMATICS    LOCERHEAD DRNE  TOPOGRAPHIC ANDSTORMSEWER. ASBUILTS SURVEY FOR: TOWN OF HOLDEN BEACH  COASTALGEOMATICS  LAND    Shaping Communities Together  mcgil  TOWN OF HOLDEN BEACH IS STORMWATER MASTER PLAN REPORT  Appendix B  Drainage Basin Maps  MCGILL ASSOCIATES 5400 TRINITY ROAD, SUITE 107, RALEIGH, NC: 27607/919378911, MCGILLASSOCIATES.COM    HigmPoints  VeptuneDrs    peoysieH  Shrimpsn  hiimpso  Cbst  Conchsa  Conchst    77Oft oIs  eRunners  mescapeDr            USDUyeSIpog  aSPuAPsuIo8  Dsys60  70S SAEO,  0SE100 3  0s0100    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix C  Hydrologic Data &  Calculations  MCGILL ASSOCIATES! 54001 TRINITY ROAD, SUITE 107, RALEIGH, NC2 250/9937891/MCGILLAISOGAIESCOM    0 9e  919888  &%  6668660  99999949995  mu uu uu uu  9999899.9.99BB9BBE9B99.8.9989999 oa 49PP91444149 egge 8 M E988P3989153889    USDA United States Agriculture NRCS Natural Resources Conservation Service  Aproduct of the National aj joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants  Custom Soil Resource  Department of Cooperative Soil Survey,  Report for Brunswick North Carolina Holden Beach SW Management  County,  RFQ  110,000  March 26, 2024    Preface  Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties oft the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, Various land use regulations of Federal, State, and local governments mayi impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are usedi in making various land use or land treatment decisions. Thei information is intended to help the land users identify and reduce the effects of soill limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments fntp/www.nres.sda, gov/wps/ otalncmansolsmalm, and certain conservation and engineering applications. For more detailedi information, contact your local USDA Service Center (ntps,/omces.Sc.egovusda.govlocatorapp7agency-nrcs) or your NRCS State Soil Scientist nttp/www.nres.usa.gowwps/portsportalnrcs.detallsols/contactus/? Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject toi flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septict tank absorption fields. Ahigh water table makes a soil poorly suited to The National Cooperative Soil Survey is aj joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Information about soilsi is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require  protect, or enhance the environment.  d-ncs142P2.053951).  basements or underground installations.  Cooperative Soil Survey.  2    altemative means for communication of programi information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or( 202)720-6382(DD). USDA is an equal opportunity  provider and employer.  3    Contents Preface.. How Soil Surveys Are Made. Soil Map.. Soil Map.. Legend.. Map Unit Legend.. Map Unit Descriptions. Brunswick County, North Carolina., BO-Bohicket: silty clayl loam.. CA--Carteret loamy fine sand.. Co-Corolla fine sand... Du--Duckston fine sand.. W-Water. References.  10 11 11 13 13 14 15 16 17 18 19 20  NeE--Newhan fine sand, 2t to 30 percent slopes.. NhE--Newhan fine sand, dredged, 21 to 30 percent slopes..  4    How Soil Surveys Are Made  Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. Theyi include a description of the soils and miscellaneous areas and their location on thel landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; thel kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, ina a soil. The profile extends from the surface downi into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid ofr roots and other living organisms and has not been changed by other Currently, soils are mapped according tot the boundaries of major land resource areas (MLRAs). MLRAS are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only al limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding oft the solvegetaton-landscape relationship, are sufficient to verify predictions of thel kinds of soil in an area and to determine the boundaries. Soil scientists reçorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them toi identify soils. After describing the soils in thes survey area and determining their properties, the soil scientists assigned the soils tot taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has as set of soil characteristics with precisely defined limits. The classes are used as al basis for comparison to classify soils systematically. Soil taxonomy, the system oft taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil  biological activity.  areas typically consist of parts of one or more MLRA.  specific location on the landscape.  5    Custom Soil Resource Report  scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined bya unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components oft the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the mapi provides sufficient information for the development ofr resource plans. Ifi intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of thel landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smalier number of measurements of individual soil properties are made and recorded. These measurements mayi include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties ofe each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements dor not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other While a soil survey is inj progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all oft the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop! yields under defined levels of management are assembled from farm records and from field or plot experiments on the same Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with at fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that al high water table will always be at a specific level int the soil on a specific date. After soil scientists located and identified the significant natural bodies of soili in the survey area, they drew the boundaries of these bodies on aerial photographs and  research.  properties.  kinds of soil.  6    Custom Soil Resource Report  identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, andi rivers, all ofv which helpi in locating boundaries accurately.  7    Soil Map  The soil map section includes the soil mapi for the defined area ofi interest, al list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to  produce the map, and a description of each soil map unit.  8    OODOBE O006SE O0OBGE OOASAE 00006AE O009SA: OODISEE O0OBSAE OODSEE O0DISAE  M.IZET. &  M.ZEI 8 e  B  COBE CDOBRIE ODO0GE  OODISE O006SAE OOOSE O0DisE    o  D03 a 198 0% 0x4600 +:00A8    Custom Soil Resource Report  Map Unit Legend  Map Unit Symbol  Map Unit Name Bohicket silty clayl loam Carteretl loamy fine sand Corolla fine sand Duckston fine sand Newhant fine sand, 2to 30 percents slopes Newhan fine sand, dredged, 2 to3 30p percent slopes Water  Acres in AOI  Percent of AOI  BO CA Co Du NeE NhE W  10.1 542.8 169.8 24.7 793.5 419.9 405.7 2,934.9  0.3% 18.5% 5.8% 0.8% 27.0% 14.3% 13.8% 100.0%  Totals for Area ofl Interest  Map Unit Descriptions  The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. Amap unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. AI map uniti isi identified and named according toi the taxonomic classification oft the dominant soils. Within ai taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond thel limits defined for at taxonomic class. Areas ofs soils of a single taxonomic class rarely, ifever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which iti is named and some minor components that belong to taxonomic classes other than those oft the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components." They generally are in small areas and could not ber mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. Ifincludedi in the database fora given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A1 few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it  11    Custom Soil Resource Report  wasi impractical to make enough observations to identify all the soils and The presence of minor components in a map uniti in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate thel landscape intol landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information fort the development of resource plans. Ifi intensive use of small areas is planned, however, onsite investigation is needed to define andI locate the soils and miscellaneous Anic identifying symbol precedes the map unit name int the map unit descriptions. Each description includes general facts about the unit and gives important soil Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ int texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis ofs such differences, a soil series is divided into soil phases. Most oft the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates af feature that affects use or management. For example, Alpha silt loam, 01 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such ani intricate pattern or in such small areas that they cannot be shown separately on the maps. The patter and proportion of the soils or miscellaneous areas are somewhat similar ina all areas. Alpha-Beta complex, Oto 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present ora anticipated uses of the map units in the survey area, ity was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, Ot to 2 percent slopes, is an example. An undifferentiated, group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one oft the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, Oto 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example.  miscellaneous areas on the landscape.  areas.  properties and qualities.  12    Custom Soil Resource Report  Brunswick County, North Carolina  BO-Bohicket silty clay loam Map Unit Setting National map unit symbol: 3w6q Elevation: Ofeet Mean annual precipitation: 42to 58 inches Mean annual air temperature: 61 to 64 degrees F Frost-free period: 190t to 270 days Farmland classification: Not prime farmland Bohicket, tidal, and similar soils: 85 percent  Map Unit Composition  Estimates are based on observations, descriptions, and transects of the mapunit.  Description of Bohicket, Tidal Landform: Tidal marshes Down-slope shape: Linear Across-slope shape: Linear A-Oto 8inches: silty clay loam Cg1-8to 38 inches: silty clay Cg2-38t08 80 inches: loamy sand Properties and qualities Slope: 0 to 1 percent Depth to restrictive feature: More than 80i inches Drainage class: Very poorly drained Runoff class: Negligible low (0.00 to 0.06 in/hr) Depth to water table: About Oi inches Frequency off flooding: Very frequent Frequency ofp ponding: Frequent Calcium carbonate, maximum content: 5, percent Gypsum, maximum content: 1 percent Sodium adsorption ratio, maximum: 55.0  Setting  Parent material: Silty and clayey fluviomarine deposits  Typical profile  Capacity oft the most limiting layert to transmit water (Ksat): Veryl low to moderately  Maximum salinity: Moderately saline to strongly saline (8.01 to 32.0 mmhos/cm) Available waters supply, Oto 60 inches: Moderate (about 6.5 inches) Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8w Ecological site: R153BY130NC- Tidal Marsh on Mineral Soil  Interpretive groups  Hydrologic Soil Group: D Hydric soil rating: Yes  13    Custom Soil Resource Report  CA-Carteret loamy fine sand Map Unit Setting National map unit symbol. 3w6v Elevation: Oto 10 feet Mean annual precipitation: 42to5 58i inches Mean annual air temperature: 61 to 64 degrees F Frost-free period: 190 to 270 days Farmland classification: Not prime farmland Carteret, tidal, and similar soils: 85 percent  Map Unit Composition  Estimates are based on observations, descriptions, and transects of the mapunit.  Description of Carteret, Tidal Setting Landform: Tidal flats Down-slope shape: Linear Across-slope shape: Linear Ag-Oto9inches: sand Cg-9to 80i inches: sand Properties and qualities Slope: 01 to 2 percent Depth to restrictive feature: More than 80 inches Drainage class: Very poorly drained Runoff class: Very high to 19.98 in/hr) Depth to water table: About 0t to 12 inches Frequency of flooding: Frequent Frequency of ponding: None Maximum salinity: Strongly saline (16.0 to 80.0 mmhos/cm) Sodium adsorption ratio, maximum: 60.0 Available water supply, Oto 601 inches: Low (about 3.6 inches) Land capability classification (irigated): None specified Land capability classification (nonirigated): 8w Hydrologic Soil Group. A/D Ecological site: R153BY130NC-1 Tidal Marsh on Mineral Soil Hydric soil rating: Yes  Parent materia!: Sandy fluviomarine deposits and/or eolian sands  Typical profile  Capacity of the most limiting layer to transmit water (Ksat): High to very high (5.95  Interpretive groups  14    Custom Soil Resource Report  Co-Corolla fine sand Map Unit Setting National map unit symbo!: 3w6y Elevation: 01 to 101 feet Mean annual precipitation: 42to 581 inches Mean annual air temperature: 61to 64 degrees F Frost-free period: 1901 to 270 days Farmland classification: Not prime farmland Corolla and similar soils: 85 percent Minor components: 7 percent Description of Corolla Setting  Map Unit Composition  Estimates are based on observations, descriptions, and transects of the mapunit.  Landform: Troughs on barrier islands Landform position (wo-dimensiona): Backslope, toeslope Landform position (hree-dmensiona): Base slope Down-slope shape: Concave Across-slope shape. Concave Parent material: Eolian sands and/or beach sand A-Oto3inches: fine sand C-3to 26 inches: fine sand Ab -26to 32 inches: sand Cg-32to 80 inches: sand Properties and qualities Slope: 0 to 61 percent Depth to restrictive feature: More than 80 inches Drainage class: Moderately well drained Runoff class: Very! high 39.96 in/hr) Depth to water table: About 18 to 36 inches Frequency of flooding: Rare Frequency of ponding: None Sodium adsorption ratio, maximum: 20.0  Typical profile  Capacity of the most limiting layert to transmit water (Ksat): Very high (19.98 to  Maximum salinity: Slightly saline to strongly saline (4.0 to 16.0 mmhos/cm) Available water supply, 0t to 60 inches: Veryl low (about 1.2 inches) Land capability classification (irigated): None specified Land capability classification (nonirigated): 7s  Interpretive groups  Hydrologic Soil Group: A Hydric soil rating: No  Ecological site: R153BY110NC - Coastal Strand, Beaches, and Dunes  15    Custom Soil Resource Report  Minor Components Duckston  Percent ofi map unit: 5 percent Landform: Depressions Down-slope shape: Concave Across-slope shape: Concave Hydric soil rating: Yes Carteret, high Percent ofi map unit: 2 percent Landform: Tidal marshes Down-slope shape: Linear Across-slope shape: Linear Hydric soil rating: Yes  Ecological site: R153BY120NC- Wet Dune Slack  Ecological site: R153BY130NC- Tidal Marsh on Mineral Soil  Du--Duckston fine sand Map Unit Setting  National map unit symbo!: 3w70 Elevation: Oto 10 feet Mean annual precipitation: 42 to 58 inches Mean annual air temperature: 61 to 64 degrees F Frost-free period: 190 to 270 days Farmland classification: Not prime farmland Duckston and similar soils: 90, percent  Map Unit Composition Description of Duckston Setting  Estimates are based on observations, descriptions, and transects of the mapunit.  Landform: Depressions Down-slope shape: Concave Across-slope shape: Concave Parent material: Eolian sands and/or beach sand A-Oto8 8inches: fine sand Cg-8to1 13 inches: sand Ab-131017inches: sand C'g- 171080inches: sand Properties and qualities Slope: 01 to 2 percent Depth to restrictive feature: More than 80 inches Drainage class: Poorly drained  Typical profile  16    Custom Soil Resource Report  Runoff class: Very high 39.96 in/hr) Depth to water table: About 01 to 6i inches Frequency of flooding: Occasional Frequency of ponding: None Sodium adsorption ratio, maximum: 20.0  Capacity oft the most limiting layer tot transmit water (Ksat): Veryh high(19.98 to  Maximum salinity: Moderately saline to strongly saline (8.0t to 16.0 mmhos/cm) Available water. supply, Oto 60 inches: Very low (about 3.0 inches) Land capability classification (irrigated): None specified Land capability classification (nonirigated): 7w Hydrologic Soil Group: A/D Ecological site: R153BY120NC- - Wet Dune Slack Hydric soil rating: Yes  Interpretive groups  NeE--Newhan fine sand, 2 to 30 percent slopes  Map Unit Setting National map unit symbol: 3w7f Elevation: 0 to 20 feet Mean annual precipitation: 421 to 58 inches Mean annual air temperature: 61 to 64 degrees F Frost-free period: 190 to 270 days Farmland classification: Not prime farmland Newhan and similar soils: 85 percent Minor components: 5 percent Description of Newhan Setting Landform: Dunes Down-slope shape. Convex Across-slope shape: Convex A-Oto 2inches: fine sand C1-2 to 50inches: fine sand C2-50t to 80i inches: sand Properties and qualities Slope: 2 to 30 percent Depth to restrictive feature: More than 80 inches Drainage class: Excessively drained Runoff class: Very low  Map Unit Composition  Estimates are based on observations, descriptions, and transects oft the mapunit.  Landform position (wo-dimensiona): Shoulder, backslope Landform position three-dimensiona): Side slope Parent material: Eolian sands and/or beach sand  Typical profile  17    Custom Soil Resource Report  Capacity of the most limiting layer to transmit water (Ksat): Very high (19.98 to  39.96 in/hr) Depth to water table: More than 80i inches Frequency of flooding: Rare Frequency of ponding: None Sodium adsorption ratio, maximum: 20.0  Maximum salinity: Slightly saline to strongly saline (4.0t to 16.0 mmhos/cm) Available water supply, Oto 60 inches: Very low (about 1.8 inches) Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8s  Interpretive groups  Hydrologic Soil Group: A Hydric soil rating: No Minor Components Beaches  Ecological site: R153BY110NC- - Coastal Strand, Beaches, and Dunes  Percent of map unit: 5 percent Landform: Barrier beaches, barriert flats R153BY120NC- Wet Dune Slack Hydric soil rating: Yes  Ecological site: R153BY110NC Coastal Strand, Beaches, and Dunes,  NhE--Newhan fine sand, dredged, 2 to 30 percent slopes  Map Unit Setting  National map unit symbol: 3w7g Elevation: Oto 101 feet Mean annual precipitation: 421 to 58i inches Mean annual air temperature.: 61 to 64 degrees F Frost-free, period: 190 to 270 days Farmland classification: Not prime farmland Newhan and similar soils: 85 percent  Map Unit Composition Description of Newhan Setting  Estimates are based on observations, descriptions, and transects of the mapunit.  Landform: Dune slacks, dunes Landform position "wo-dimensiona): Shouider, backslope Landform position (hree-dimensiona): Side slope Down-slope shape: Convex Across-slope shape: Convex Parent material: Sandy dredge spoils A-Oto 1inches: fine sand  Typical profile  18    Custom Soil Resource Report  C-1to801 inches: fine sand Properties and qualities Slope: 21 to 30 percent Depth to restrictive feature: More than 80 inches Drainage class: Excessively drained Runoff class: Very low 39.96 in/hr) Depth to watert table: More than 80i inches Frequency oft flooding: Rare Frequency of ponding: None Sodium adsorption. ratio, maximum: 20.0  Capacity oft the most limiting layer to transmit water (Ksat): Very! high (19.98 to  Maximum salinity: Slightly saline to strongly saline (4.0t to 16.0 mmhos/cm) Available water supply, Oto 60 inches: Very low (about 1.8 inches) Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 8s  Interpretive groups  Hydrologic Soil Group: A Hydric soil rating: No  Ecological site: R153BY110NC- Coastal Strand, Beaches, and Dunes  W-Water  Map Unit Composition Water: 100 percent Description of Water Interpretive groups  Estimates are based on observations, descriptions, and transects oft the mapunit.  Land capability classification (irrigated): None specified Land capability classification (nonirigated): 8  Hydric soil rating: No  19    References  American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods ofs sampling American Society for Testing and Materials (ASTM). 2005. Standard classification of Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Federal Register. July 13, 1994. Changes in hydric soils oft the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. ntp/www.nrcs,usda.govwpsponal Soil Survey Staff. 1999. Soil taxonomy: Al basic system ofs soil classification for making andi interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:!! www.nresusda.gowmpsporaincceainatonalsols/co-nIs142P2.053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:!! www.nrcs.usda. govwpsportalnrcs/detai/natonalsols/7od-nrcs142P2.053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and' Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. tpwww.nres.usdagowmpsportalnrcs/etallsols/ United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. ntp/Nwwnrcsusdagowwpsponalinves,  and testing. 24th edition.  soils for engineering purposes. ASTM Standard D2487-00.  Service FWS/OBS-79/31.  soils in the United States.  nrcs/detallnationalsois7cid-nrcs142p2.054262  Section. Report Y-87-1.  home/7cid-nrcs142p2.053374  delallnationalandusenduselangepasurec-steprdb1043084  20    Custom Soil Resource Report  United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. ntp/wwwnrcs.usda.govmwps/portal United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. ntp/wwanrcsusda.gompporalnccesdetalnatonalsols? United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:!! wwamcauadagowimtemnentmeFE-POCUMENTSmnm42R.05290pd  nrcs/detallsols/scietists7eid-nres142p2.054242  cd-nres142P2.053624  21    3/18/24,4:34PM  Precipitation! Frequency Data Server  NOAA Atlas 14, Volume 2, Version 3 SOUTHPORT 5N Station ID:31-8113 Location name: Southport, North Carolina, USA* Latitude: 33.9922°, Longitude: -78.01° Elevation: Elevation (station metadata): 201 f* "source: ESRI Maps 5 source: USGS POINT PRECIPITATIONI FREQUENCY ESTIMATES G.M. Bonnin, D. Martin, B. Lin,T T. Parzybok, M.Y Yekta, andD.F Riley NOAA, National Weather Service, Silver Spring. Maryland PF_tabularl PF graphical Maps& aerials  PF tabular  PDS-based point precipitation frequency estimates with 90% confidence intervals (ini inches)'  Average recurrence interval (years)  Duration' 1 5-min 0.544 10-min 0.869 15-min 1.09 30-min 1.49 60-min 1.86 2-hr 2.22 3-hr 2.38 6-hr 2.98 12-hr 3.50 24-hr 4.08 2-day 4.68 3-day 4.90 4-day 5.13 7-day 5.79 10-day 6.50 20-day 8.72 30-day 10.8 45-day 13.3 60-day 16.3  2 0.647 1.04 1.30 1.80 2.26 2.71 2.90 3.64 4.27 4.94 5.66 5.92 6.18 6.98 7.78 10.4 12.8 15.7 19.2  5 1.20 1.52 2.16 2.77 3.41 3.66 4.62 5.45 6.40 7.25 7.54 7.82 8.77 9.63 12.6 15.4 18.7 22.5  10 1.34 1.69 2.45 3.20 4.03 4.36 5.50 6.53 7.67 8.64 8.94 9.24 10.3 11.2 14.5 17.5 21.0 25.1  25 1.50 1.90 2.82 3.76 4.87 5.34 6.77 8.10 9.64 10.7 11.0 11.3 12.5 13.4 17.2 20.4 24.3 28.5  50  100 200 500 1000 1.63 1.76 1.89 2.06 2.19 2.07 2.23 2.38 2.59 2.75 3.11 3.41 3.71 4.12 4.46 4.22 4.70 5.20 5.91 6.51 5.60 6.38 7.23 8.47 9.56 6.22 7.16 8.21 9.79 11.2 7.90 9.13 10.5 12.6 14.5 9.50 11.1 12.8 15.5 17.9 11.4 13.4 15.7 19.2 22.2 12.6 14.7 17.1 20.7 23.9 12.9 14.9 17.2 20.8 23.9 13.1 15.1 17.4 20.9 24.0 14.3 16.3 18.5 21.7 24.3 15.3 17.4 19.6 22.7 25.4 19.4 21.7 24.2 27.7 30.5 22.7 25.0 27.5 30.9 33.6 26.8 29.5 32.2 35.8 38.7 31.2 33.9 36.6 40.2 42.9  0.750 0.837 0.943 1.02 1.11 1.19 1.30 1.39  0598055)0801069109)08SOB3)OTAoNBODos110101419.0 08-1.28) (416-141/124151) (0.808-0.939) (0.961-1,12)! (1.11-1.29) (1.24-1.44) (1.38-1.62) (1.50-1.76) 18.199,07120122,.0.35238) (1.01-1.17) (1.21-1.40) (1.41-1.64) (1.56-1.82) (1.75-2.05) (1.90-2.23): 203240)2.16257) 1232280/1244299) (1.38-1.61) (1.67-1.94) (2.00-2.33) (2.27-2.64) (2.59-3.03) (2.85-3.35) (3.11-3.67) 13364.00,13.6944,6)13.964.84) (1.73-2.01) (2.09-2.43) (2.56-2.98) (2.95-3.44) (3.45-4.04) (3.87-4.54) (4.28-5.06) (4.71-5.61) 529639/16787.06) (2.05-2.43) (2.50-2.96) (3.14-3.72) (3.70-4.39) (4.45-5.31) (5.09-6.10) (5.76-6.95) (6.48-7.87) 75.924,(0840-105 (2.18-2.61) (2.66-3.18) (3.36-4.02) (3.98-4.78) (4.86-5.85) (5.61-6.81) 64278,030899,0581071070123 (2.73-3.30) (3.34-4.02) (4.22-5.09) (5.01-6.06) (6.12-7.44) (7.08-8.68) (8.13-10.0) 02.15/00339.124109) (3.18-3.91) (3.87-4.75) (4.93-6.07) (5.88-7.26) (7.22-8.98) (8.42-10.5) 1971422).1-142)0 (33472/151498) (3.76-4.47) (4.57-5.44) (5.89-7.02) (7.04-8.43) (8.76-10.6) (10.2-12.5) (11.9-14.7) (13.6-17.3) (163213)(186249) (4.34-5.11) (5.26-6.18) (6.71-7.96) (7.94-9.49) (9.76-11.8) (11.3-13.9) 11163,150.190/C78231202289) (4.56-5.33) (5.51-6.44) (6.99-8.22) (8.24-9.76) (10.1-12.1) (11.6-14.1) 433164/052.190,088023,03270) (4.78-5.55) (5.76-6.70) (7.27-8.49) (8.54-10.0) (10.4-12.3) (11.9-14.3) 13616515--91.08224/205271) (5.44-6.19) (6.56-7.48) (8.22-9.40) (9.58-11.0) (11.5-13.4) (13.2-15.4) (49176)(166209.092237.212274) (6.12.6.94) (7.32-8.32) (9.02-10.3) (10.5-12.0) (12.5-14.4) (14.1-16.5) (15.9-18.7y 0722/092392279) (8.20-9.32) (9.77-11.1) (11.9-13.6) (13.6-15.6) (16.0-18.4) (17.9-20.8) 199234220.82/248303270336) (10.2-11.5) (12.1-13.7) (14.5-16.4) (16.5-18.6) (19.1-21.7) 3102390399121.95,00239 (12.6-14.1) (14.9-16.7) (17.6-19.8) (19.8-22.3) (22.8-25.8) (25.1-28.5) 2733141296344,102387/950421) (15.5-17.3) (18.3-20.3) (21.3-23.8) (23.7-26.5) (26.9-30.2) 043D0170/P40359004DR143 'Precipitation frequency (PF) estimatesi int this table areb based onf frequency analysis ofp partial duration series (PDS). Numbers inp parenthesis areF PF estimates: atk lower andu upper bounds oft the 90% confidence interval. Thep probability that precipitation frequency estimates (for ag given duration and averager recurrencei interval) willl be greater than the upper bound (ork less thant thel lower bound)is 5%. Estimates atu upper bounds arer noto checked against probable maximump precipitation (PMP)e estimates andr may! be! highert than currentlyv valid PMP  values.  Please refer toN NOAAAtlas 14 document for morei information.  Backt tol Top PF graphical  https:/hdsc.n nws.noaa. gowposplts.pminpayehmAtrasarsienskatrcsphsna-englahaseres-pals  1/4    3/18/24, 4:34PM  Precipitation Frequency Data Server  PDS-based epthduraton-feqveny, (DDF) curves Latitude: 33.9922°, Longitude.-78.0100"  Average recurrence interval (years)  40 30  10 25 50 100 200 500 1000  0  :* 5 h Duration  40 30 20 10  Duration 5-min 10-min 15-min 30-min 60-min 2-hr 3-hr 6-hr 12-hr 24-hr  2-day 3-day 4-day 7-day 10-day 20-day 30-day 45-day 60-day  10  25 50 100 200 500 1000  Average recurrence interval (years)  NOAAA Atlas 14, Volume 2, Version 3  Created (GMI): Mon! Mar 1820:34:042024  BacktoToR Maps & aerials Small scale terrain  ps/ndsenwanosagopbapta.pinpageimfhatmoisa-3iannsunisrenglhiseres-p.is  2/4    3/18/24, 4:34PM  Precipitation Frequency Data Server  MILITARY OCEANTML SUNNYPOINT  3km 2mi  Large scale terrain  ke  Fayetteville.  Pamlie  Jacksonville Bay  INA  Wilmington Onslow  Long Bay 100km  leston  Large scale map Fayetteville  Jacksonville Wilmington  orth ston u ston  100km 60mi  Large scale aerial  tips/hdsc.nws.noaagpwptasplds.pmnpagehtm78-ncst-ncista-31-8ii3sdaua-dephnsuntsenyglshâseries-pds  3/4    3/18/24, 4:34PM  Precipitation Frequency Data Server  Fayetteville  Jacksowile wilmington  harleston mure  100km  BacktoTOR  US Department of Commerce National Oceanic and Atmospheric/ Administration Nationaly Woather Sorvice National Water Center 1325 East West Highway Silver Spring. MD: 20910 Questions?: HPSCO-ssmsnsagy Disclaimer  itps./hdsc.nws.noaaowpidsptas.pmnpagehim?s-ncksta3181136daba-dephsunts-englishéseries-pds  4/4    hitps/www.noaagov), PEUPEENTS (  Home () / Products products.htm!) /Datums datonahimintpe-Datumo, /8659665 BOWEN POINT, SHALLOTTE INLET Favorite Stations  Station Info Tides/Water Levels Meleorological Obs. Phys. Oceanography Datums for 8659665, BOWEN POINT, SHALLOTTE INLET  NOTICE:All data values arer relative totheN MLLW. Elevations on Mean Lower Low Water Station: 8659665, BOWEN POINT, SHALLOTTE INLET Status: Accepted (Jan 312 2023) Units: Feet Control Station: 86581201 Wimington, NC TM.:0 Epoch: amm.plomsam-MDe) 1983-2001 Datum: MLLW Datum MHHW( Gaun.PominTAMEw, MHW Veaum.oponshamimaw, MTL (datum_ options. htm#MTL) MSL (Idalum_ options. htm#MSL) DTL( (Idatum_ options. htm#DTL) MLW (dalum_ options. htmi#MLW) MLLW( (/datum_ options. htmi#MLLW) NAVD88 (datum options.h htmi) STND( (datum_ options. htm##STND) GT (datum_ options. html#GT) MN( (datum_ options. htm!#MN) DHQ (Idatum_ options. htm!#DHQ) DLQ (datum_ options. htmI*DLQ) HWI (/datum_ options. htmi#HWI) LWI (datum_ options. htm#LWI) Max1 Tide (Idalum_ options. html#MAXTIDE) Max Tidel Date &1 Time (datum.options. hIIMAXTIDEDI) Min Tide( (Idatum_ options. hImHMINTIDE) Minl Tide Date &1 Time (Idatum_ options.h hUlMINTIDEDT) HAT (datum_ options. htm!#HAT) HAT Date &1 Time LAT( (/datum options.h hUnI#LAT) LATDate &1 Time Tidal Datum Analysis Periods 01012022-05312022  Value 4.76 4.42 2.28 2.26 2:38 0.15 0.00 2.87 -23.90 4.77 4:26 035 0.15 0.52 6.90  Description Mean! Higher-- -High Waler Meank High Water Mean1 Tide Level Mean Seal Level Mean Diumal Tidel Level Mean Low Water Mean Lower-Low' Water North American Vertical Datum of 1988 Station Datum Great Diumal Range Mean Range ofl Tide Mean Diurnal High Water Inequality Mean Diurnal LowV Waterl Inequality Greenwich Highy Waterl Interval (int hours) Greenwicht Low Waterl Interval (in hours) Highest Observed Tide Highest Observed Tide! Date &1 Time Lowest Observed Tide Lowest Observed1 Tide Date &1 Time Highest Astronomical Tide HATO Date andT Time LowestA Astronomical" Tide LATO Date and Time  6,16 10/28/2011 13:30 -152 02/09/2001 07:24    Datums for 8659665, BOWEN POINT, SHALLOTTE INLET  Allf figuresi inf feet relative tox MLLW  OMHEW:4.76. MHW: 4.42. KAVD88: 2.87  DHQ: 0.35  MSL:D.26 MTL:2.28,0TL238 MN: 4.26 GT:4.77.  MLW:0.15 MIW.O  m0.15  Showing datums for 1611347 PORTA ALLEN, HAN.. Datum MLLW Data Units e Feet  Meters Epoch @ Present (1983-2001) Superxedea/19604970) Submit  Hide nearbys stations NEARE BOWENP POINT, SHALLOTTEINLET  Wilmington, NC( (datums. Mm78-8552b5ame-waningonisue-Nc) Springmaid Pier. SC( (dalums. himi?d-86610705name-Spingmand Pier&state-sC) Wrightsville Beach, NC (datums. aiSww-iyAe Beachéstate-NC) Beaufort, Duke! Marine Lab, NC nwwwtwA DukeN MarineL Lab&state-NC) Don HoltE BridgeA Air Gap, SC (datums. Mma-s75éname-Danl HoltE Bridge Air Gap&state-sC) Ravenel BridgeA Air Gap, SC (datums. mAtSSAaneRaen. Bridge Air Gap&state-sC) Charleston, SC( (datums. mamr7a-885530Snamer-cansonisia-so) ORIENTAL, NEUSE RI, R, (datums. htmi7d-88551338name-ORIENTAL, NEUSE Ri&statesR.) CEDARI ISL, D, (datums. dessiitnm-cED. ISLéstate-D.) Ocracoke, Pamlico So, d. (datums. html?id-8 e854789éname-Ocache Pamlico So&state-d.) FortF Pulaski, GA (datums. Mimfna8/0e/0inamefonPuasksae-OA  Varnamiown FollyCount Holden Beach  Mer nbens Clubat S James  Clubaist Ployeis  01 h  Ocean Pier Beach  Ocean Per  Long Beach Oak Islant  Bg Besc  sle    NOAR/  TIDES8 CURRENTS  htps//www.noaagow,  ()  Home () I Products (products.htm!) /Datums SatonshmrypecDaum, / 8659414 Varnamtown, Lockwoods Folly River Favorite Stations  Station Info  Tides/Water Levels  Meteorological Obs. Phys. Oceanography  Datums for 8659414, Varnamtown, Lockwoods Folly River  NOTICE: All data values are relative to the MLLW. Elevations on Mean Lower Low Water Station: 8659414, Varnamtown, Lockwoods Folly River Control Station: 8658163 Wrightsville Beach, NC Epoch: datum.options.htmiNTDE) 1983-2001  Status: Accepted (Apr 262 2023) Units: Feet T.M.:0 Datum: MLLW Datum  Value 4.27 3.95 2,08 2.15 2.14 0.20 0.00 1.99 -26.13 4.27 3.76 0.31 0.20  Description Mean Higher-High Water Mean High Water Mean Tide Level Mean Sea Level Mean Diurnal Tide Level Mean Low Water Mean Lower-Low Water North American Vertical Datum of 1988 Station Datum Great Diurnal Range Mean Range of Tide Mean Diurnal High Water Inequality Mean Diurnal Low Water Inequality  MHHW At.PCEMTAMHV, MHW aum.PIonsnmeNrw, MTLdam.PimahmTy MSL Gatum.cPtonshmeMs) DTL VGaum.pPlonsmimeoTy MLW datum.cPlomanmnMw, MLLW Gum.ponhn-MLw, NAVD88 datum.optons.ntm!, STND Gaum.cptonahmasINo) GT( Gaum.cPlons.inso MN Gaum.cptonshtmaMN, DHQ Gatum.cPlonanime0mo, DiQamm.ptpahmoio,  A    Datum  Value 1.05 7.62  Description hours)  HWI Gatum.cPlonstmarw, LWI Gatum.Plions.ntmm.w, Max Tide (datum_oPtions.htmiMAXTIDE) Max Tide Date & Time (datum.options.htmI#MAXTIDEDI) Min Tide (datum.options.ntns.ItmIMINTIDE) Min Tide Date & Time datum.oPtions.htm#MINTIDEDI) HAT Gatm.PtonstmA) HAT Date & Time  Greenwich High Water Interval (in Greenwich Low Water Interval (in hours) Highest Observed Tide Highest Observed Tide Date & Time Lowest Observed Tide Lowest Observed Tide Date & Time Highest Astronomical Tide HAT Date and Time Lowest Astronomical Tide LAT Date and Time  5.63 10/27/2007 13:54 -0.91 01/31/2014 07:30  LAT Gatum.pPions.nimHLA) LAT Date & Time  Tidal Datum Analysis Periods 04012022-08202022  Datums for 8659414, Varnamtown, Lockwoods Folly River  All figures ini feet relative to MLLW  OMHHW: 4.27  MHW: 3.95..  DHQ: 0.31  MSL:2.15 DTL214TAmL208. WAVDBB:1.99  MN:3.76 GT:4:27  MLW: 0275  CMLLW:0 Datums  DLQ:0.2  NOM/NOS/CO-OFS    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACH IS STORMWATER MASTER PLAN REPORT  Appendix D  Existing Conditions Maps  MCGILL ASSOCIATES5400 TRINITY ROAD, SUITE 107, RALEIGH, NC. 27607/919378.91MACGILLASSOCIATES.COM    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix D  Existing Conditions Maps  MCGILL ASSOCIATES 54001 TRINITY ROAD, SUITE 107, RALEIGH, NC27607/91937893789M1/MCGILLASSOCIATESCOM    HigbPoins  unandspues    Conchs?  Conchst    MOHOnO    ISpBBISICH  OSPEOISIEH  Overflow 10    SSDugpsIpou  ISGDABO  OSSIAPO    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix E  Proposed Conditions Maps  MCGILL ASSOCIATES! 5400 TRINITY ROAD, SUITE 107, RALEIGH, NC27607/97937893789M1/MACGILLASSOCIATES.COM    aigbpons    9  ugbpoms      GDPomst    Higbponst  45  -3    Conchsp  Conchst  AvenueB    Conchst  Conchst  deRungr  AyenueA  enueB        OE 5    7580BW 7540BW  OBW 744 OBW  7380BW 7300BW 726 OBW 720OBW    ano    USPBBISIEH  aSpeSIsEH    USDBaISIH  OSDBEISIEU    Shaping Communities Together  mcgil  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix F  Engineering Details  MCGILL ASSOCIATES 5400 TRINITY ROAD, SUITE 107, RALEIGH, NC 27607 919.378.9111, /MCGILLASSOCIATES.COM    515  DRAWN: JLM DATE: 010924 REVIEWED: JLM PROJECTNO REV:  D  SC-160LP STANDARD DETAILS  NOTTOSCALE    DRAWN: JLM DATE: REVIEWED: JLM PROJECTNO: REV:  ADS  SC-310 STANDARD DETAIL  NOTTOSCALE    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix G  Existing Island-Wide Flooding Heat Map  MCGILL ASSOCIATES 54001 TRINITY ROAD, SUITE 107, RALEIGH, NCZ 27607 7919378.9111/MCGILLASSOCIATES.COM    TI    I    II  S        p            TRE    A    Shaping Communities Together  mcgill  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix H  Construction Cost  Estimates  MCGILL ASSOCIATES 54001 TRINITY ROAD, SUITE 107, RALEIGH, NC: 27607/919378.911, /MCGILLASSOCIATES.COM    Holden Beach Stormwater Improvements 300 Block OBW. - Alternative 1 Phasel 1 Opinion of Probable Construction Cost  May 29, 2024 Item No.  Description  Qty 1  Unit Unit Cost Total Cost* LS $ 19.150 19,500.00 LS S 11,490 $ 11,500.00 LS $ 11,490 s 11,500.00 EA $ 9,000.00 $ 9,000.00 EA $ 5,000.00 $ 20,000.00 LS $ 3,000.00 $ 3,000.00 TON $ 60.50 $ 13,500.00 SY $ 122.00 $ 20,500.00 LF $ 160.00 $ 10,000.00 LF $ 95.00 $ 130,000.00 LF $ 87.00 s 20,500.00 EA $ 10,000.00 $ 10,000.00 AC $ 2,900.00 $ 3,000.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC EROSION CONTROL CLEARING & GRUBBING > REMOVE &1 REPLACE CATCH BASIN 6 INSTALLI NEW CATCHI BASIN 7 CONTROL OF WATER/ DEWATERING 8 BREAKINGOFI EXT ASPH PVMT 9 REMOVAL OF EXT ASPHALT: PVMT 10 2" ASP CONC SURF CRS $9.5B OR S9.5C 11 8" ASP CONCI BASE CRS B25.0C 12 REMOVE. & REPLACE SIDEWALK 13 12" HDPE 14 15"F HPPP 15 18" CLASS IIII RCP 16 REMOVE. & REPLACETIDE GATE 17 CLASS BRIPI RAP 18" THICK 18 GEOTEXTILEI FOR DRAINAGE 19 SEEDING ANDI MULCHING 20 EXCAVATION 21 GRADING 22 HAULINGI EXCESS MATERIAL Contingencies (3094* Price Escalation. Factor (2096* *Rounded tot then nearest $1000  LS S SY $ SY S TON $  1,500 S 1,500.00 3.00 $ 7,500.00 9.50 s 23,000.00 79.00 s 68,000.00  4 2,389 2,389 215 860 167 60 1,365 230 1.0 TON $ 1,594 SY $ 1.00 1,338 CY $ 4,840 SY $ 1,338 CY $  80.00 $ 3.50 $ 6,000.00 6.60 $ 9,000.00 3.00 $ 15,000.00 28.00 s 37,500.00 Subtotal" S 450,000.00 $ 135,000.00 $ 90,000.00 Total* S 675,000.00  500.00  Opinion ofl Probable Construction Cost Range*: $450,000.00 to $675,000.00    Holden Beach Stormwater Improvements 300 Block OBW- Alternative 11 Phase 2 Opinion of Probable Construction Cost  May 29, 2024 Item No.  Description  Qty I  Unit  Unit Cost Total Cost* LS $ 32,675 $ 33,000.00 LS $ 19,605 $ 20,000.00 LS $ 19,605 $ 20,000.00 LS $ 3,000.00 $ 3,000.00 TON $ 60.50 $ 8,000.00 AC $ 2,900.00 $ 1,000.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC EROSION CONTROL 4 CLEARING & GRUBBING 5 CONTROL OF WATER/DEWATERING 6 2" ASP CONC SURF CRS S9.5B OR S9.5C 7 g"ASP CONCI BASE CRS B25.0C SC-310 INFILTRATION: SYSTEM 9 SEEDING ANDN MULCHING 10 EXCAVATION/ FILL 11 GRADING  LS $ TON S CF $ CY $ SY $  1,500 $ 1,500.00 79.00 $ 41,500.00 30.00 $ 594,000.00 6.60 $ 4,500.00 3.00 s 4,500.00 Subtotal" $ 731,000.00 $ 219,300.00 > 146,200.00 Total" $1,096,500.00  130 520 19,796 0.30 614 1,452  Contingencies (309)" Price Escalation. Factor (20%)" *Rounded tot the nearest $1000  Opinion of! Probable Construction Cost Range*:S $731,000.00 to $1,096,500.00    Holden Beach Stormwater Improvements 300 Block OBW- - Alternative 2 Phase 1 Opinion ofProbable Construction Cost  May 29, 2024 Item No.  Description  Qty I  Unit Unit Cost Total Cost* LS $ 21,300 $ 21,500.00 LS S 12,780 $ 13,000.00 LS S 12,780 $ 13,000.00 LS $ EA $ 9,000.00 $ 9,000.00 EA $ 5,000.00 $ 20,000.00 LS $ 3,000.00 S 3,000.00 SY $ SY $ TON S 60.50 $ 13,500.00 TON $ SY $ 122.00 $ 20,500.00 LF $ 160.00 $ 19,500.00 LF $ 95.00 $ 130,000.00 LF $ EA $ 10,000.00 S 10,000.00 TON $ 80.00 $ SY $ AÇ $ 2,900.00 $ 3,500.00 CY $ SY $ CY $ 28.00 $ 57,000.00  MOBILIZATION MAINTENANCE OF TRAFFIC EROSION CONTROL CLEARING & GRUBBING REMOVE & REPLACE CATCH BASIN 6 INSTALLNEW CATCH BASIN CONTROL OF WATER/ DEWATERING BREAKING OF EXT ASPHE PVMT 9 REMOVAL OF EXT ASPHALTE PVMT 10 2" ASP CONC SURF CRS $9.5B OR S9.5C 11 8" ASP CONC BASE CRS B25.0C 12 REMOVE &1 REPLACE SIDEWALK 13 12" HDPE 14 15"] HPPP 15 18" CLASS III RCP 16 REMOVE. & REPLACE TIDE GATE 17 CLASSE BI RIPI RAP 18" THICK 18 GEOTEXTILE! FORI DRAINAGE 19 SEEDING AND MULCHING 20 EXCAVATION 21 GRADING 22 HAULINGEXCESSI MATERIAL Contingencies (30%)* Price Escalation Factor (209)" *Rounded tot ther nearest $1000  1,500 $ 1,500.00 3.00 $ 7,500.00 9.50 $ 23,500.00 79.00 $ 69,500.00 87.00 $ 20,500.00 3.50 $ 11,500.00 6.60 $ 13,500.00 3.00 $ 16,500.00 Subtotal* S 498,000.00 $ 149,400.00 $ 99,600.00 Total* S 747,000.00  4 2,433 2,433 219 876 167 120 1,365 230 1.0 3,183 1.11 2,033 5,382 2,033  500.00  Opinion of Probable Construction Cost Range*: $498,000.00 to $747,000.00    Holden Beach Stormwater Improvements 300 Block OBW - Alternative 2 Phase 2 Opinion of Probable Construction Cost  May 29, 2024 Item No.  Description  Qty I  Unit Unit Cost Total Cost" LS $ 69,575 $ 70,000.00 LS S 41,745 $ 42,000.00 LS $ 41,745 $ 42,000.00 LS $ 3,000.00 $ 3,000.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC 3 EROSION CONTROL 4 CLEARING & GRUBBING CONTROL OF WATER/DEWATERING 6 2" ASP CONÇ SURF CRS S9.5B OR S9.5C 8"A ASP CONÇ BASE CRS B25.0C SC-310 INFILTRATION: SYSTEM SC-160LP: INFILTRATION: SYSTEM 10 SEEDING. ANDI MULCHING 11 EXCAVATION/FIL 12 GRADING  LS $ 260 TON S 1,040 TON $ 19,796 CF $ 17.741 CF $ 1.11 646 CY $ 5,382 SY $  1,500 $ 1,500.00 60.50 $ 16,000.00 79.00 $ 82,500.00 30.00 $ 594,000.00 38.00 $ 674,500.00 6.60 $ 4,500.00 3.00 S 16,500.00 Subtotal" $ 1,550,000.00 $ 465,000.00 $ 310,000.00 Total" S 2,325,000.00  AC $ 2,900.00 $ 3,500.00  Contingencies (309)" Price Escalation Factor (20%)* *Rounded tot thet nearest $1000  Opinion of] Probable Construction Cost Range": $1,550,000.00 to $2,325,000.00    Holden Beach Stormwater Improvements Opinion ofl Probable Construction Cost  East End Mullet Street & East End Avenue. A-A Alternative 1  May 29, 2024 Item No.  Description  Qty  Unit  Unit Cost Total Cost* LS $ 28,075.00 $ 28,500.00 LS $ 16,845.00 $ 17,000.00 LS $ 16,845.00 $ 17,000.00 LS $ 5,615.00 $ 6,000.00 EA $ 9,000.00 S 135,000.00 EA $ 1,560.00 $ 23,500.00 EA $ 2,800.00 $ 3,000.00 LS $ 16,845.00 $ 17,000.00  MOBILIZATION MAINTENANCE OF TRAFFIC EROSION CONTROL CLEARING & GRUBBING 5 REMOVE & REPLACE CATCH BASIN ADJUST EXISTING CATCHI BASIN/ PIPE REMOVE BLIND. JUNCTION, BOX CONTROL OF WATER/DEWATERING BREAKING OF EXT ASPH PVMT 10 REMOVALOF EXT ASPHALTI PVMT 11 2" ASP CONC. SURF CRS S9.5B OR S9.5C 12 8" ASP CONC BASE CRS B25.0C 13 PIPE REMOVAL 14 18" CLASS III RCP 15 24" CLASS IIII RCP 16 30" CLASS II RCP 17 TIDE GATE 18 CLASS BI RIP RAP 18" THICK 19 GEOTEXTILE! FOR DRAINAGE 20 SEEDING. ANDI MULCHING 21 EXCAVATION 22 GRADING 23 HAULING EXCESS MATERIAL Contingencies (30%6)* Price Escalation. Factor (20%6)" Rounded to ther nearest $1000  15 15 1 1,889 1,889 170 680 1,794 60 566 1,180 I 1.0 2 0.75 2 3,630 2  SY $ SY $ TON $ TON $ LF S LF $  3.00 $ 6,000.00 9.50 $ 18,000.00 60.50 $ 10,500.00 79.00 $ 54,000.00 28.00 $ 50,500.00 87.00 s 5,500.00  LF $ 110.00 s 62,500.00 LF $ 146.00 $ 172,500.00 EA $ 8,000.00 $ 8,000.00 TON $ 80.00 $ SY $ AC $ 2,900.00 $ 2,500.00 CY $ SY $ CY $  500.00 3.50 $ 500.00 6.60 $ 500.00 3.00 $ 11,000.00 28.00 $ 500.00 Subtotal* S 650,000.00 $ 195,000.00 130,000.00 Total"s 975,000.00  Opinion of Probable Construction Cost Range*: $650,000.001 to $975,000.00    Holden Beach Stormwater Improvements Opinion ofl Probable Construction Cost  East End Mullet Street & East End Avenue A- Alternative 2  May. 29,2024 Item No.  Description  Qty 1 15 15 I 1,889 1,889 170 680 1,794 215 60 566 1,180 1 1.0 2 1.00 166 4,840 166  Unit  Unit Cost Total Cost* LS $ 35,000.00 S 35,000.00 LS $ 21,000.00 $ 21,000.00 LS $ 21,000.00 s 21,000.00 LS S 7,000.00 S 7,000.00 EA $ 9,000.00 $ 135,000.00 EA $ 1,560.00 $ 23,500.00 EA $ 2,800.00 S 3,000.00 LS $ 21,000.00 S 21,000.00 TON $ 79.00 $ 54,000.00 SY $ 122.00 $ 69,000.00 LF S 28.00 S 50,500.00 LF $ 274.50 $ 59,500.00 LF $ 87.00 S 5,500.00 LF $ 110.00 $ 62,500.00 LF $ 146.00 S 172,500.00 EA $ 8,000.00 $ 8,000.00 AC $ 2,900.00 S 3,000.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC 3 EROSION CONTROL 4 CLEARING & GRUBBING 5 REMOVE & REPLACE CATCH BASIN 6 ADJUST EXISTING CATCH BASIN/I PIPE 7 REMOVE BLIND. JUNCTION! BOX 8 CONTROL OF WATER/ DEWATERING 9 BREAKINGOFI EXTA ASPH PVMT 10 REMOVAL OF EXTA ASPHALT: PVMT 11 2" ASP CONC: SURF CRSS S9.5B OR S9.5C 12 8" ASP CONC BASE CRS B25.0C 13 REMOVE &1 REPLACE CONCRETE DRIVE 565 & SIDEWALK 14 PIPE REMOVAL 15 12" HPPPI PIPE 16 18" CLASS III RCP 17 24" CLASS III RCP 18 30" CLASS mI RCP 19 TIDE GATE 20 CLASSI BI RIPI RAP 18" THICK 21 GEOTEXTILEI FOR DRAINAGE 22 SEEDING ANDI MULCHING 23 EXCAVATION 24 GRADING 25 HAULINGI EXCESS MATERIAL Contingencies (30%)" Price Escalation. Factor (20%)" *Roundedt tot thes nearest $1000  SY $ SY S TON $  3.00 $ 6,000.00 9.50 $ 18,000.00 60.50 $ 10,500.00  TON $ SY $ CY $ SY $ CY $  80.00 $ 3.50 S 6.60 $ 1,500.00 3.00 $ 15,000.00 28.00 $ 5,000.00 Subtotal* S 808,000.00 $ 242,400.00 $ 161,600.00 Total" $ 1,212,000.00  500.00 500.00  Opinion ofl Probable Construction Cost Range": $808,000.00 to $1,212,000.00    Holden Beach Stormwater Improvements West End ROW- Alternative 1 Opinion ofProbable Construction Cost  May 29, 2024 Item No.  Description  Qty I - 2 1 167 167 15 60 145 155 1.0 2 0.10 484 25  Unit Unit Cost Total Cost* LS S 4,775.00s 5,000.00 LS $ 2,865.00 $ 3,000.00 LS $ 2,865.00 $ 3,000.00 LS $ 955.00 $ 1,000.00 EA $ 9,000.00 $ 9,000.00 EA $ 5,000.00 $ 10,000.00 LS $ 2,865.00 $ 3,000.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC EROSION CONTROL 4 CLEARING & GRUBBING 5 REMOVE & REPLACE CATCH BASIN 6 INSTALL NEW CATCHI BASIN 7 CONTROLOF WATER/DEWATERING 8 BREAKING OF EXT ASPH PVMT 9 REMOVALOFI EXT ASPHALT PVMT 10 2" ASP CONC SURF CRS S9.5B OR S9.5C 11 8" ASP CONCI BASE CRS B25.0C 12 REMOVE. & REPLACE CONCRETE DRIVE 42 13 12" HPPP PIPE 14 12" CLASS III RCP 15 CLASS BI RIPI RAP 18" THICK 16 GEOTEXTILEI FOR DRAINAGE 17 SEEDING. ANDI MULCHING 18 GRADING 19 HAULINGEXCESS MATERIAL Contingencies (3096* Easement Acquisition Price Escalation Factor (20%6)* *Rounded to ther nearest! $1000  SY $ SY $ TON $ TON $  3.00 $ 9.50 $ 2,000.00 60.50 S 1,000.00 79.00 $ 5,000.00  500.00  SY $ 122.00 $ 5,500.00 LF $ 274.50 $ 40,000.00 LF $ 183.00 $ 28,500.00 TON $ 80.00 $ SY $ AC $ 2,900.00 $ SY $ CY s  500.00 500.00 500.00  3.50 $ 3.00 $ 1,500.00 28.00 $ 1,000.00 Subtotal" S 120,500.00 $ 36,150.00 $ 60,000.00 $ 24,100.00 Total" S 240,750.00  Opinion of Probable Construction Cost Range*: $120,500.00 to $240,750.00    Holden Beach Stormwater Improvements West End ROW- Alternative: 2 Opinion ofl Probable Construction Cost  May 29, 2024 Item No.  Description  Qty I 1 2 I 189 189 17 68 400 390 1.0 2 0.15 726 66  Unit  Unit Cost Total Cost* LS $ 8,725.00s 9,000.00 LS $ 5,235.00 $ 5,500.00 LS $ 5,235.00 $ 5,500.00 LS $ 1,745.00 $ 2,000.00 EA $ 9,000.00 $ 9,000.00 EA $ 5,000.00 $ 10,000.00 LS $ 5,235.00 $ 5,500.00 SY $ SY $ TON $ 60.50 S 1,500.00 TON $ SY $ 122.00 $ 5,500.00 LF $ 274.50 $ 110,000.00 LF $ 87.00 $ 34,000.00 TON $ SY $ AC $ 2,900.00 $ SY $ CY $  MOBILIZATION 2 MAINTENANCE OF TRAFFIC EROSION CONTROL CLEARING & GRUBBING 5 REMOVE & REPLACE CATCH BASIN 6 INSTALL NEW CATCH) BASIN 7 CONTROL OF WATER/DEWATERING 8 BREAKING OF EXT ASPH PVMT 9 REMOVALOF EXT ASPHALTI PVMT 10 2" ASP CONC SURF CRS S9.5B OR S9.5C 11 g" ASP CONC BASE CRSE B25.0C 12 REMOVE & REPLACE CONCRETE DRIVE 42 13 12" HPPP PIPE 14 18" CLASS III RCP 15 CLASS BI RIPI RAP 18" THICK 16 GEOTEXTILE! FOR DRAINAGE 17 SEEDING ANDI MULCHING 18 GRADING 19 HAULINGI EXCESS MATERIAL Contingencies (30%)" Easement Acquisition Price Escalation. Factor (20%6)* *Rounded to thet nearest $1000  3.00 $ 1,000.00 9.50 $ 2,000.00 79.00 s 5,500.00 80.00 $ 3.50 $ 3.00 $ 2,500.00 28.00 $ 2,000.00 Subtotal" $ 212,000.00 $ 63,600.00 $ 60,000.00 $ 42,400.00 Total* S 378,000.00  500.00 500.00 500.00  Opinion of Probable Construction Cost Range": $212,000.00 to $378,000.00    Holden Beach Stormwater Improvements 760 Block OBW - Alternative 1 Opinion ofl Probable Construction Cost  May 29, 2024 Item No.  Description  Qty I 2 1 300 300 27 108 35 250 1.0 2 0.10 484 21  Unit  Unit Cost Total Cost* LS $ 3,800.00 $ 4,000.00 LS $ 2,280.00 $ 2,500.00 LS $ 2,280.00 $ 2,500.00 LS $ 760.00 $ 1,000.00 EA $ 5,000.00 $ 10,000.00 LS $ 2,280.00 $ 2,500.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC 3 EROSION CONTROL 4 CLEARING& GRUBBING 5 INSTALL NEW CATCH BASIN CONTROL OF WATER/DEWATERING BREAKING OF EXT ASPH PVMT 8 REMOVALOFI EXT ASPHALT PVMT 9 2" ASP CONC SURF CRS $9.5B OR S9.5C 10 8" ASP CONC BASE CRS B25.0C 11 REMOVE & REPLACE CONCRETE DRIVE 139 & SIDEWALK 12 15" CLASS III RCP 13 24" CLASSI III RCP 14 CLASS BI RIPI RAP 18" THICK 15 GEOTEXTILEI FOR DRAINAGE 16 SEEDING ANDI MULCHING 17 GRADING 18 HAULINGI EXCESS MATERIAL Contingencies (309)" Easment Acquisition OR Property Acquisition Price Escalation. Factor (20%" *Roundedi tot then nearest SL000  SY $ SY $ TON $ TON $  3.00 S 1,000.00 9.50 $ 3,000.00 60.50 $ 2,000.00 79.00 $ 9,000.00  SY $ 122.00 $ 17,000.00 LF $ 62.00 S 2,500.00 LF $ 110.00 $ 27,500.00 TON $ SY $ AC $ 2,900.00 S SY $ CY $  80.00 $ 3.50 $ 3.00 $ 1,500.00 28.00 $ 1,000.00 Subtotal" S 148,500.00 $ 44,550.00 $ 60,000.00 $ 250,000.00 $ 29,700.00 Total* $ 472,750.00  500.00 500.00 500.00  Opinion of Probable Construction Cost Range*: $148,500.00 to $472,750.00    Holden Beach Stormwater Improvements 760 Block OBW. : Alternative 2 Opinion ofl Probable Construction Cost  May 29, 2024 Item No.  Description  Qty 1 I 4 1,178 1,178 106 424 35 820 1.0 2 0.15 726 68  Unit  Unit Cost Total Cost* LS $ 11,775.00S 12,000.00 LS $ 7,065.00 $ 7,500.00 LS S 7,065.00 $ 7,500.00 LS $ 2,355.00 s 2,500.00 EA S 5,000.00 $ 20,000.00 LS $ 7,065.00 $ 7,500.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC 3 EROSION ÇCONTROL 4 CLEARING& GRUBBING 5 INSTALL! NEW CATCHI BASIN CONTROL OF WAIEN/DEWATERING BREAKING OF EXT ASPH] PVMT REMOVALOF EXT ASPHALTPVMT 9 2" ASP CONC SURF CRS $9.5BOR $9.5C 10 8" ASP CONC BASE CRSI B25.0C 11 REMOVE &1 REPLACE CONCRETE DRIVE 500 & SIDEWALK 12 15" CLASS III RCP 13 24" CLASSI III RCP 14 CLASS BI RIPI RAP 18" THICK 15 GEOTEXTILEI FOR DRAINAGE 16 SEEDNGANDMULCHING 17 GRADING 18 HAULINGI EXCESS MATERIAL Contingencies (30%6)" Price Escalation. Factor (209)" Rounded tot ther nearest! $1000  SY $ SY $ TON $ TON $  3.00 $ 4,000.00 9.50 $ 11,500.00 60.50 S 6,500.00 79.00 $ 33,500.00  SY S 122.00 s 61,000.00 LF $ 62.00 $ 2,500.00 LF $ 110.00 $ 90,500.00 TON $ SY $ AÇ $ 2,900.00 S SY $ CY $  80.00 $ 3.50 S 3.00 $ 2,500.00 28.00 $ 2,000.00 Subtotal* $ 272,500.00 $ 81,750.00 54,500.00 Total"s 408,750.00  500.00 500.00 500.00  Opinion of Probable Construction Cost Range": $272,500.00 to $408,750.00    Holden Beach Stormwater Improvements Carolina Avenue Alternative. 1 Opinion ofl Probable Construction Cost  May 29, 2024 Item No.  Description  Qty  Unit  Unit Cost Total Cost* LS $ 8,475.00 8,500.00 LS $ 5,085.00 S 5,500.00 LS $ 5,085.00 $ 5,500.00 LS $ 1,695.00 $ 2,000.00 EA $ 5,000.00 $ 10,000.00 EA $ 5,000.00 $ 10,000.00 LS $ 5,085.00 S 5,500.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC 3 EROSION CONTROL 4 CLEARING& GRUBBING CATCH BASIN 6 JUNCTION. BOXI MANHOLE CONTROL OF WATER/ DEWATERING 8 BREAKING OFE EXT ASPH PVMT 9 REMOVAL OF EXT ASPHALTI PVMT 10 2" ASP CONC SURF CRSS S9.5B OR S9.5C 11 8" ASP CONCI BASE CRSI B25.0C 12 REMOVE & REPLACE CONCRETE DRIVE 276 13 30" CLASS IIII RCP 14 SEEDING. AND MULCHING 15 GRADING 16 HAULINGI EXCESS MATERIAL Contingencies (30%)* Price Escalation. Factor (20%6)* Rounded to ther nearest $1000  2 2 778 778 70 280 570 0.10 500 48  SY $ SY $ TON $ TON S SY $ 122.00 $ 34,000.00 LF $ 146.00 $ 85,000.00 AC $ 2.900.00 $ SY $ CY $ 28.00 s 1,500.00  3.00 S 2,500.00 9.50 s 7,500.00 60.50 $ 4,500.00 79.00 $ 22,500.00 3.00 $ 1,500.00 Subtotal* $ 206,500.00 $ 61,950.00 41,300.00 Total" S 309,750.00  500.00  Opinion of Probable Construction Cost Range": $206,500.00 to $309,750.00    Holden Beach Stormwater Improvements Carolina Avenue - Alternative: 2 Opinion ofl Probable Construction Cost  May 29, 2024 No. Item  Description  Qty 1 2 2 1 833 833 75 300 705 0.15 722 59  Unit  Unit Cost Total Cost* LS $ 8,375.00 S 8,500.00 LS $ 5,025.00 $ 5,500.00 LS $ 5,025.00 $ 5,500.00 LS $ 1,675.00 S 2,000.00 EA $ 5,000.00 S 10,000.00 EA $ 5,000.00 $ 10,000.00 LS $ 5,025.00 $ 5,500.00  MOBILIZATION 2 MAINTENANCE OF TRAFFIC EROSIONCONTROL 4 CLEARING & GRUBBING 5 CATCH BASIN 6 JUNCTION: BOXI MANHOLE CONTROL OF WATER/ DEWATERING BREAKING OF EXT ASPH PVMT 9 REMOVALOFI EXT ASPHALT PVMT 10 2" ASP CONC SURF CRS S9.5B OR S9.5C g" ASP CONC BASE CRS B25.0C 12 REMOVE & REPLACE CONCRETE DRIVE 283 13 24" CLASS IIII RCP 14 SEEDING. ANDMULCHING 15 GRADING 16 HAULING EXCESS MATERIAL Contingencies (30%)* Permitting (10%)* Price Escalation. Factor (2096)" Rounded tot cher nearest S1000  SY $ SY $ TON $ TON $ SY $ 122.00 S 35,000.00 LF $ 110.00 $ 78,000.00 AC $ 2,900.00 $ SY $ CY $  3.00 $ 2,500.00 9.50 $ 8,000.00 60.50 $ 5,000.00 79.00 $ 24,000.00 3.00 s 2,500.00 28.00 $ 2,000.00 Subtotal" s 204,500.00 $ 61,350.00 $ 20,450.00 $ 40,900.00 Total* S 327,200.00  500.00  Opinion of Probable Construction Costl Range": $204,500.00 to $327,200.00    Holden Beach Stormwater Improvements Davis Street Erosion Control Opinion of Probable Construction Cost  May. 29, 2024 Item No.  Description  Qty  Unit  Unit Cost Total Cost* LS $ 800.00 $ 1,000.00 LS $ 160.00 s LS $ 15,000.00 $ 15,000.00 AC S 2,900.00 $ 1,000.00  MOBILIZATION 2 CLEARING& GRUBBING BLIND SWALE/LEVEL: SPREADER 4 SEEDING. ANDI MULCHING Contingencies (30%6)" Price Escalation. Factor (20%" Roundedt to ther nearest $1000  500.00  0.20  Subtotal" $ 17,500.00 $ 5,250.00 $ 3,500.00 Total" s 26,250.00  Opinion of Probable Construction Cost] Range-:517,500,00: to $26,250.00    Shaping Communities Together  mcgnll  TOWN OF HOLDEN BEACHISTORMWATER MASTER PLAN REPORT  Appendix  Stormwater Utility  Financial Model Outcomes  MÇGILL ASSOCIATES 5400 TRINITY ROAD, SUITE 107, RALEIGH, NC27607/9193789378911/MCGILLASSOCIATES.COM    1888 88888888 88  6    Thousands    8 d8 1888  0 88    Thousands  3