Photo on 22 October 2016 Post Matthew. Nags Head Shoreline Management Committee Meeting

Transcription

1 Photo on 22 October 2016 Post Matthew Nags Head Shoreline Management Committee Meeting 18 January 2017

2 Project Schedule for the 2018 Re-Nourishment 2016 Month 1 May Initiate work (1) Define the ideal (target) beach condition Mon 2 5 Jun- (2) Conduct borrow area survey Sept (3) Develop renourishment requirements, dune stabilization alternatives, and initiate engineering studies Mon 6-8 Oct-Dec Design scenarios, cost estimates, initiate permit liaison 2017 Mon 9 13 Jan-May (1) Select renourishment scenario (2) Obtain boring, and complete preliminary design (3) Pre-application meetings with regulatory & resource agencies, and prepare supporting environmental documents Mon 14 Jun Submit permit applications with supporting documents Mon Jul-Dec Permit liaison to secure permits in time 2018 Mon Jan-Apr Receive permits / prepare plans and specifications, request bids, receive bids, select contractor, construction preparation Mon May-Aug Construction and construction administration

3 Planning Goal of the 2018 Re-Nourishment To Define a Target Beach Condition Provide higher level of storm protection Provide wider recreational beach Address south end of Nags Head erosion issue Integrate dune management plan into the renourishment design Replenish sand deficit in the sand box Maintain Nags Head s eligibility for future FEMA community assistance funds* *FEMA Disaster Assistance Fact Sheet DAP Eligible Sand Replacement on Public Beaches: Renourishments must be to the project design; partial renourishments or hot-spot nourishments are not considered maintenance of the improved project.

4 Project Reaches and Subreaches Reach 1 MP 11 to to Reach 2 MP 16.8 to 19.2 R to Reach 3 MP 19.2 to to o R3N MP 19.2 to 20.2 R2 R3 Dune to o R3S MP 20.2 to to Reach 4 MP 20.8 to to

5 Limulus St. Subreaches in Reach 3 Seagull Drive 1500 ft 3500 ft

6 Review of 2018 Renourishment Scenarios Reach Length Low Fill Mid Fill High Fill Selected 1 29,300 ft 590,000 cy (20 cy/ft) 2 13,000 ft 390,00 cy (30 cy/ft) 3N 5,500 ft 300,000 cy (55 cy/ft) 3S 3,500 ft 420,000 cy (120 cy/ft) 4 1,500 ft 100,000 cy (67 cy/ft) 880,000 cy (30 cy/ft) 480,00 cy (35 cy/ft) 300,000 cy (55 cy/ft) 490,000 cy (140 cy/ft) 240,000 cy (160 cy/ft) 1,150,000 cy (40 cy/ft) 600,00 cy (45 cy/ft) 500,000 cy (90 cy/ft) 490,000 cy (140 cy/ft) 240,000 cy (160 cy/ft) 880,000 cy (30 cy/ft) 390,00 cy (30 cy/ft) 500,000 cy (90 cy/ft) 490,000 cy (140 cy/ft) 240,000 cy (160 cy/ft) Total 52,800 ft 1,800,000 cy (34 cy/ft) 2,400,000 cy (45 cy/ft) 3,000,000 cy (57 cy/ft) 2,500,000 cy (47 cy/ft)

7 Project Scale for the 2018 Re-Nourishment 10-mile from MP 11 to 21 Four reaches and two subreaches in Reach 3 Selected fill quantity = 2.5 MCY (~47 cy/ft) Fill density (# of cy per ft) varies from north to south Reaches 1 & 2 (8-mi) have economic fill density of 30 cy/ft Reaches 3 & 4 (2-mi) have restoration fill density of cy/ft North Boundary near Bonnett St. (MP 11) South Boundary near McCall Court (MP 21)

8 Preliminary Design of Average Profile By Reach/Subreach Reach 1 (29,300 ft) Volume = 880,000 cy Fill Density = 30 cy/ft Dune Reach 2 (13,000 ft) Volume = 390,000 cy Fill Density = 30 cy/ft

9 Preliminary Design of Average Profile By Reach/Subreach Reach 3N (5,500 ft) Volume = 500,000 cy Fill Density = 90 cy/ft Dune Reach 3S (3,500 ft) Volume = 490,000 cy Fill Density = 140 cy/ft Dune Fill = 10 cy/ft

10 Preliminary Design of Average Profile By Reach/Subreach Reach 4 (1,500 ft) Volume = 240,000 cy Fill Density = 160 cy/ft Dune Fill = 10 cy/ft Dune Total (52,800 ft) Volume = 2,500,000 cy Fill Density = 47 cy/ft

11 Summary of Preliminary Design By Reach/Subreach More uniform dunes Reach Length (ft) Nourishment Berm (ft) Dune* Before (cy/ft) Dune** Added (cy/ft) Dune* After (cy/ft) Fill Density (cy/ft) 1 29, , N 5, S 3, , Total 52, *Dune volume includes frontal dune and back beach volume and is calculated from the crest of the dune to +6 ft NAVD. **Dune will be constructed during renourishment between +6ft and +10 ft NAVD.

12 Check Box of Planning Goals of the 2018 Renourishment Provide higher level of storm protection Provide wider recreational beach Address south end of Nags Head erosion issue Integrate dune management plan into the renourishment design Replenish sand deficit in the sand box Maintain Nags Head s eligibility for future FEMA community assistance funds

13 Nags Head Average Profiles June 2016 (Before Matthew) Versus Oct 2016 (After Matthew) Loss Average volume loss by Matthew is 27 cy/ft or ~1.43 million cy

14 Preliminary Design to Restore Volume Loss Caused by Matthew Reac h Length (ft) Total Volume Loss (cy/ft) Unit Volume Loss (cy/ft) Fill Density* (cy/ft) Total Fill (cy) 1 29, , , , , ,000 3N 5, , ,000 3S 3, , , ,500 69, ,000 Total/ Avg 52,800 1,431, ,430,000 * Dune volume is included here, and will be designed and constructed between +6ft and +10 ft NAVD wherever necessary.

15 What to Expect after 2018 Renourishment Provide higher level of storm protection Dune growth Provide wider recreational beach Wider beach Address south end of Nags Head erosion issue Improved south end Integrate dune management plan into the renourishment design Enhanced dune growth Replenish sand deficit in the sand box More sand in the sand box Maintain Nags Head s eligibility for future FEMA community assistance funds Possible federal/state funds Long-Term Management Plan

16 Natural Dune Growth

17 One-Mile Average Beach Width Before/After 2011 Project From CSE Monitoring Reports

18 Additional Beach Width Added by Renourishment (Before Matthew) 2016 (After Matthew) 2018 Renourishment (2.5 MCY) 2018 Renourishment + FEMA (3.93 MCY)

19 Cost Analysis Construction Cost Summary Year Location State Scale (mcy) Max Pumping Distance (miles) Unit Cost* ($/cy) 2001 PKS/IB NC PKS/IB/EI NC Isle of Palms SC Nags Head NC Southampton NY Feb 2016 KDH/KH/Duck NC Mar 2016 KDH/KH/Duck NC Apr 2016 Buxton NC Oct 2016 Edisto Beach SC ** Myrtle Beach SC * Unit cost includes mobilization/demobilization and pumping. ** Based on the USACE s estimated construction cost published on 26 Sept 2016.

20 Cost Analysis Nags Head 2018 Renourishment Mobilization/Demobilization Cost = $5 million Pumping Unit Cost = $7.50/cy Equivalent unit cost = $9.50/cy Total construction estimate of 2.5 mcy = $23.75 million

21 Summary of Probable Cost Estimates Project Length (ft) Volume (MCY) Mob/De (M$) Pumping ($/cy) Total Const. (M$) Permitting/ Eng* (M$) Total Cost (M$) 2018 Renourishment FEMA Restoration Combined Projects** 52, MCY $5 M $7.50/cy $23.75 M $4.08 M $27.83 M 52, MCY $4 M $8.50/cy $16.16 M $4.08 M $20.24 M 52, MCY $5 M $7.50/cy $34.48 M $4.40 M $38.88 M * It includes the cost of permitting, engineering, legal, benthic studies, turtle monitoring, post-project monitoring, sand fencing, vegetation, contingency, etc. ** Assumed 2018 renourishment and FEMA restoration projects can be permitted and constructed under the same construction period.

22 Discussion