Dare County Nourishment Project Town of Duck

Transcription

1 Dare County Nourishment Project Town of Duck Julien Devisse, P.E. and Ken Willson CB&I / Coastal Planning & Engineering of North Carolina, Inc. February 15, 2017 A World of Solutions

2 Outline Background Beach Fill Design/Construction Plans Borrow Area Design/Construction Plans Construction Photos Bid Items and Schedule Monitoring/Renourishment Questions A World of Solutions 1

3 Background Southern Shores Project Limits ~1.6 Miles 1.4 MCY 1,500 feet 80,000 CY ~3.6 Miles 1.8 MCY ~2.6 Miles 0.9 MCY Approx. 8.3 miles and 4.1 MCY A World of Solutions 2

4 Storm Damage Reduction Project Pre-Project Conditions 3

5 Storm Damage Reduction Project Constructed Beach Fill Initial Construction 4

6 Storm Damage Reduction Project Post-Construction Adjustment in 6-18 months Equilibration of Beach Fill 5

7 Storm Damage Reduction Project Advance Fill Design Beach Nourishment Interval 6

8 Storm Damage Reduction Project Design Beach Loss of Advance Fill During Project Interval Nourishment Interval 7

9 Storm Damage Reduction Project Maintenance (Renourishment) Maintenance = Beach Renourishment 8

10 Profile Equilibration Construction Template Pre-Construction Beach Profile A World of Solutions 9

11 Profile Equilibration Constructed Fill A World of Solutions 10

12 Profile Equilibration Profile Equilibration between January 2015 and July 2015 Profile Equilibration Equilibrated Fill A World of Solutions 11

13 Wave Height Reduction Profile Equilibration between January 2015 and July 2015 Reduction in depth = Reduction in wave height A World of Solutions 12

14 Wave Height Reduction ~1.6 Miles 1.1 MCY 2,500 feet 80,000 CY ~2.7 Miles 0.9 MCY Courtesy of ASBPA A World of Solutions 13

15 Outline Background Beach Fill Design/Construction Plans Borrow Area Design/Construction Plans Construction Photos Bid Items and Schedule Monitoring/Renourishment Questions A World of Solutions 14

16 Project Design Duck Design Classic Advanced Fill and Design Cross Section Concept Design Cross Section Based on Storm Induced Beach Change Model (SBEACH) Advanced Fill Based on 5 Year Renourishment Interval A World of Solutions 15

17 Storm Induced Beach Change Model (SBEACH) Simulates beach profile changes that result from varying storm waves and water levels Identify structures potentially impacted during storm events Additional surveys and SBEACH analysis conducted Town wide A World of Solutions 16

18 Storm Induced Beach Change Model (SBEACH) Eliminated Impacts With 20/80 Design A World of Solutions 17

19 Design ft. Dune Town of Duck Design +20 ft. NAVD Elevation (FT NAVD) ft. Average Design Berm +6 ft. NAVD 5 10 Existing Profile Distance Along Profile (FT) A World of Solutions 18

20 Cover Sheet A World of Solutions 19

21 Control Data A World of Solutions 20

22 Plan View Staging Area Spindrift Lane Bufflehead Road Skimmer Way A World of Solutions 21

23 Staging Area A World of Solutions 22

24 Plan View Baseline Spindrift Lane (1) Dune Bufflehead Road (2) Landward Berm Crest (3) Seaward Berm Crest (4)Toe of Fill (1) Dune (2) Berm (3) (4) A World of Solutions 23

25 Plan View Bufflehead Road A World of Solutions 24

26 Plan View Skimmer Way A World of Solutions 25

27 Cross Sections A World of Solutions 26

28 Construction Template ft. Dune Town of Duck Construction Profile +20 ft. NAVD Elevation (FT NAVD) ft. Average Construction Berm +6 ft. NAVD 5 10 Template Existing Profile Distance Along Profile (FT) A World of Solutions 27

29 Construction Template Town of Duck Construction Profile Elevation (FT NAVD) / 0.5 ft. Paid Tolerance 5 10 Template Existing Profile Distance Along Profile (FT) A World of Solutions 28

30 Construction Template Town of Duck Construction Profile No Pay Elevation (FT NAVD) Eligible for Payment +/ 0.5 ft. Paid Tolerance 10 Template Existing Profile Distance Along Profile (FT) A World of Solutions 29

31 Outline Background Beach Fill Design/Construction Plans Borrow Area Design/Construction Plans Construction Photos Bid Items and Schedule Monitoring/Renourishment Questions A World of Solutions 30

32 Borrow Areas A World of Solutions 31

33 Borrow Area Design Locations of geophysical tracklines surveyed and vibracores collected during Phase II and III. A World of Solutions 32

34 Vibracore Analysis Vibracore Analysis Grain Size, Sorting, Silt %, Munsell Color, Shell Hash, Carbonate % A World of Solutions 33

35 Borrow Area Design Proposed Borrow Area C Proposed Design Area = 354 Acres Proposed Design Volume = 2,049,000 cy A World of Solutions 34

36 Borrow Area Plan View A World of Solutions 35

37 Borrow Area Cross Sections A World of Solutions 36

38 Town of Duck Borrow Area Design Borrow Area C finer grained material than native Option 1 - If entire Town of Duck Project constructed from Borrow Area C - 20% Volume Increase Option 2 2:1 ratio (borrow area A: borrow area C) A World of Solutions 37

39 Grain Sizes Coarser Finer Sand Designed Beach A World of Solutions 38

40 Outline Background Beach Fill Design/Construction Plans Borrow Area Design/Construction Plans Construction Photos Bid Items and Schedule Monitoring/Renourishment Questions A World of Solutions 39

41 Construction Photos Fill Area Overview A World of Solutions 40

42 Construction Photos Fill Area Overview A World of Solutions 41

43 Construction Photos Work Limits A World of Solutions 42

44 Construction Photos Work Limits A World of Solutions 43

45 Construction Photos Dune Construction A World of Solutions 44

46 Construction Photos Work Area A World of Solutions 45

47 Construction Photos No Hold Harmless A World of Solutions 46

48 Construction Photos Hold Harmless In Place A World of Solutions 47

49 Construction Photos Sand Ramp A World of Solutions 48

50 Construction Photos Sand Ramps A World of Solutions 49

51 Construction Photos Lighting Shields Condition as of August 7, 2014 (looking south)

52 Construction Photos Lighting Shields Condition as of August 7, 2014 (looking south)

53 Outline Background Beach Fill Design/Construction Plans Borrow Area Design/Construction Plans Construction Photos Bid Items and Schedule Monitoring/Renourishment Questions A World of Solutions 52

54 Bid Items Base Bid Items 3 Towns Mob/Demob, Bonds, BA surveys and Turtle Trawling (5 days) Beach Fill Discretionary Bid Items Potential Unsuitable Fill Material Screening/Removal Environmental Protection Additional Trawling Tilling Turbidity Monitoring Dredge Standy Rates Owner or Regulatory Agency shuts down work (not weather/mechanical delays) A World of Solutions 53

55 Sea Turtle Monitoring Network for Endangered Sea Turtles (N.E.S.T.) May 1 through Nov 15 Nesting Surveys between sunrise and 9 am must clear beach Limits of beach fill reduced Nighttime turtle observer on-site/escort outside of active work zone Sea Turtle observed Work stopped within 500 ft. Lays nest Work shall not resume within 500 ft. until relocated Courtesy of N.E.S.T A World of Solutions 54

56 TENTATIVE Schedule The Schedule is not binding and is meant to provide estimated construction times for planning purposes. The beach nourishment start and end dates are subject to change. Information will be updated as new information becomes available. ~1.6 Miles 1.4 MCY Duck Start Mid/late May End Mid/late July (~60 days) 1,500 feet 80,000 CY KH/Southern Shores Start Mid June End - Mid August (~60 days) ~3.6 Miles 1.8 MCY Kill Devil Hills Start Early August End Early/Mid Sept (~35-45 days) ~2.6 Miles 0.9 MCY Approx. 8.3 miles and 4.1 MCY A World of Solutions 55

57 Moving Forward Construction Town Wide Monitoring Analysis of Town Wide Conditions Nourishment / Renourishment A World of Solutions 56

58 Thank you! Contact Julien Devisse, P.E. Project Engineer (910) Office A World of Solutions 57

59 Frequently Asked Questions Why does the sand pumped onto the beach initially appear to be a darker color? What impacts can be expected during nourishment construction? What if the contracted volume is reached before all sections of the project area receive sand? What will happen to the organisms, such as sand fleas, that live on the beach and in the surf zone? Why are there escarpments on the beach? Why don t we have federal assistance like Wrightsville Beach or Virginia Beach? What do you mean by FEMAreimbursed nourishment? What happens if a storm hits and damages the beach? How long will construction take place in front of a particular property? Why is dredging occurring during the summer months?

60 Frequently Asked Questions Why does the sand pumped onto the beach initially appear to be a darker color? The sand has been buried and unexposed to sunlight. Once exposed to the elements, this disappears quickly and the material will match the existing sand. What impacts can be expected during nourishment construction? Once the project starts the contractor will be working 24/7 to complete the project as quickly as possible. To ensure public safety during this time, direct access to the beach in front of a given property will be prohibited. The contractor will install caution tape at crossovers that lead to the active construction area. Likewise, the contractor will install a temporary barrier on the northern and southern boundary of the active construction area to prohibit pedestrian traffic. In the immediate construction zone, the sound of heavy equipment, including backup alarms, will be heard and, at night, lights will be visible. As the project moves down the beach, a pipe will be placed incrementally to pump the sand for the project. Ramps will be provided at regular intervals to ensure that access to the water is maintained.

61 Frequently Asked Questions What if the contracted volume is reached before all sections of the project area receive sand? GLDD and CPE-NC will monitor the quantity placed each day to insure that the nourishment volume is distributed according to plan. Minor adjustments are made as the project progresses along the beach in response to changing conditions so as to provide the planned nourishment volume within each subsection of the project area. What will happen to the organisms, such as sand fleas, that live on the beach and in the surf zone? Benthic organisms (organisms that live on or near the seabed) in the surf zone generally have short life cycles and recover rapidly after beach nourishment (or severe storms). Typical recovery rates are measured in months according to numerous studies. Why are there escarpments on the beach? Equilibration of the profile may leave low escarpments at the edge of the surf between the new dry beach and the wet beach. This process is similar to what natural beaches experience after minor storm events, particularly during the first northeasters of the fall. Any escarpments greater than 18 inches that are present between May 1 and August 30 shall be leveled.

62 Frequently Asked Questions Why don t we have federal assistance like Wrightsville Beach or Virginia Beach? Unfortunately, federal funds for beach nourishment have never been made available to Nags Head. Dare County has been working with the US Army Corps of Engineers on a county-wide, federally-funded project for many years, but money for construction has never been allocated. What do you mean by FEMA-reimbursed nourishment? If the Town experiences a storm that is declared a disaster by the President, the Town may be eligible for FEMA funding to replace sand lost during that storm. A monitoring and maintenance plan, along with a plan for funding the maintenance, must be in place for FEMA to consider reimbursing the Town for lost sand. What happens if a storm hits and damages the beach? The Town will establish a monitoring and maintenance program that will help us determine the amount of sand loss so that we can move forward with either the regular maintenance nourishment or a FEMAreimbursed nourishment.

63 Frequently Asked Questions How long will construction take place in front of a particular property? The progress can vary greatly depending weather, downtime and the volume of sand being placed along the beach. At the commencement of the project, progress is typically slower as the contractor needs some time to work out the kinks in their equipment. Once these kinks have been worked out, the contractor averages between 150 and 250 feet of beach per day. Therefore, a specific property will be impacted by construction on average 4 to 6 days. Once the Project commences a daily progress map will be available at Why is dredging occurring during the summer months? Dredging operations offshore of the Outer Banks typically take place in the summer months because it is much safer for the crews working on the offshore dredge. The increased risk of safety and anticipated decreases in productivity in the winter months when sea conditions can shut down dredge operations were found to drive the costs of the projects up to a point where they would have no longer been financially viable.

64 Summertime Dredging A World of Solutions 63