National Academies Press: OpenBook

Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications (1988)

Chapter: Part II. The Criteria, Options, and Evaluation

« Previous: Part I. Background Considerations
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 45
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 46
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 47
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 48
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 49
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 50
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 51
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 52
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 53
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 54
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 55
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 56
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 57
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 58
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 59
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 60
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 61
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 62
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 63
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 64
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 65
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 66
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 67
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 68
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 69
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 70
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 71
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 72
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 73
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 74
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 75
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 76
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 77
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 78
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 79
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 80
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 81
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 82
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 83
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 84
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 85
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 86
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 87
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 88
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 89
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 90
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 91
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 92
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 93
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 94
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 95
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 96
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 97
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 98
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 99
Suggested Citation:"Part II. The Criteria, Options, and Evaluation." National Research Council. 1988. Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications. Washington, DC: The National Academies Press. doi: 10.17226/9502.
×
Page 100

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

rag I' The Criteria Options' and [valuation

4 Preservation Options and Evaluation Criteria THE OPTIONS The committee identified and evaluated ten principal options, some of which foreclose others. For example, relo- cation would eliminate from immediate consideration the con- struction of a seawall, and a seawall would make subsequent relocation difficult or impossible. Other options, such as beach nourishment or breakwater construction, could be used in combination. The committee did not evaluate every pos- sible option, but selected the following as worthy of consid- eration: Incremental relocation of the lighthouse intact Rehabilitation of the groinfield without revetment Rehabilitation of the groinfield with revetment Seawall/revetment Artificial- reefs · Offshore breakwaters and groinfield rehabilitation Deployment of artificial seagrass Continuing beach nourishment No action New lighthouse CRITERIA TO EVALUATE PRESERVATION OPTIONS To evaluate the options, the committee developed a set of criteria or tests against which to judge the options. The 47

48 committee then discussed appeared relevant. Each respect to each criterion. The criteria the committee used are: Criteria, Options, and Evaluation and listed those criteria that option was then discussed with Technical feasibility. Can the option be implemented suc- cessfully from a technical or engineering standpoint? Long-term reliability. Will the option protect the light- house for at least 100 years? Short-term reliability. house for at least 20 years? Initial cost. the option? Will the option protect the light What is the approximate cost to implement Long-term cost. What are the likely recurrent future costs to maintain the effectiveness of the option? Protection of natural resources. What are the potential effects on ecological, hydrological, geomorphological, and related natural systems and processes in the vicinity of Cape Hatteras Lighthouse? Aesthetic impact. What is the visual effect of the option? Local public considerations. How are residents of the Outer Banks, specifically Buxton, N.C., likely to view the option? Protection of historical values. What is the implication of the option for preserving the lighthouse, its associated build- ings, and its historical milieu? Will a precedent be set for protection of other historic structures similarly endangered? Public access and recreation. What is the effect of the option on public enjoyment of the lighthouse site, including the beach in front of it?

Options and Criteria 49 Risk of damage to the lighthouse during implementation. What is the likelihood of damage to or destruction of the lighthouse due to or during implementation of the option? Preservation of other options--short term. To what extent does the option immediately foreclose alternative pres- ervation options? Preservation of other options--Ion" term. ervation options foreclosed after 20 years? Are other pres Construction time. How long will it take to achieve effective protection after an option is chosen? Coastal Barrier Resources Act. Although NPS is not covered by the CBRA, to what extent is the option consistent with the act? NPS shoreline-management policies. Is the option consis- tent with NPS policy not to obstruct natural processes on coastal barriers? North Carolina coastal policies. Is the option consistent with state policy on response to shoreline retreat? Flood-hazard mitigation. How does the option relate to the national goal of reducing flood hazards through adjust- ment of land use in floodplains, the National Flood Insurance Act, and Executive Order 11988? Wetlands effects. What is the option on wetlands and other U.S. Section 404 of the Federal Clean Water Act? potential effect of the waters regulated under Fisheries. What are the potential effects of the option on commercial and recreational fish habitats? Navigation. How would the option affect commercial and recreational navigation? The criteria fit into four general categories. The first contained crucial criteria: if an option failed to meet these

50 Criteria, Options, and Evaluation criteria, it was not considered further. The crucial criteria were technical feasibility, short-term reliability, initial and long-term cost, protection of historical values, and risk of damage to the lighthouse during implementation. Options that met the criteria in category 1 then were considered against criteria in category 2. This category con- tained important criteria but not so important that failure to meet one of them automatically excluded an option from fur- ther consideration. Some of these criteria are relative-- although no option would guarantee protection under all cir- cumstances, some would offer better protection than others. All options that would provide at least some protection would cost a substantial amount of moneY. but some would cost more than others. . . . . . . - ~. ~. . . - . ~ ~ , The criteria in category 2 were long-term ready, Nag and ~ong-~erm cost, protection of natural recreation, lone term. _ resources, aesthetic impact, public access and preservation of other options in the short and construction time, and NPS shoreline-management policies and North Carolina's coastal policies. The third category consisted of criteria that overlapped with one or more in category 2: Coastal Barrier Resources Acts flood-hazard mitigation, and wetlands effects. Although these criteria were not identical to any in category 2, every time the relevant category 2 criteria--i.e., protection of natural resources and relevant coastal-management policies-- were met, these criteria also were satisfied. Category 4 contained two criteria that did not appear to be affected much by any option--fisheries and navigation-- and one criterion, local public considerations, which is impor- tant to decision makers but outside the committee's purview. Six options failed criteria in category 1. Deployment of artificial seagrass is not technically feasible in that it does not work, and the committee was uncertain of the effective- bullulng a new light- nouse would not protect historical values as required by NPS's mandate. Beach renourishment would incur excessive long-term costs, and no action or rehabilitation of the groin- field without a revetment would not provide reliable short- term protection for the lighthouse. The committee's evaluations of the remaining four options were based largely on criteria in category 2 and are dis- cussed in detail in Chapter 5. In brief, relocation would not , . . ness of artificial reefs at this site.

Options and Criteria 51 fail any criterion. The seawall/revetment option would con- flict with coastal management policies, historic preservation, long-term cost, public access and recreation, aesthetic con- siderations, risk of damage during implementation, and pres- ervation of other options. Rehabilitation of the groinfield with a revetment and offshore breakwaters with groinfield rehabilitation would not satisfy criteria concerning long-term reliability and shoreline management policies. The types of conflicting considerations faced by the com- mittee (such as conflicting public policies and the desirability of minimizing cost while maximizing protection) also might arise in other NPS decisions regarding historic preservation and conservation. The committee suggests that an approach similar to one it used--developing a set of relevant criteria and studying options against those criteria--would prove use- ful for other decisions that involve conflicting considerations.

5 Evaluation of the Options The committee provides cost estimates for the options discussed below (except for artificial reefs, for which too many variables are involved, and artificial seagrass, for which no effective level of application can be determined). In some cases, estimates from other sources were used as the basis for the committee's estimates. In other cases, the committee developed its own estimates. The committee's cost estimates are conservative, and should be considered as guides, within a range of perhaps +20%. The actual cost of each option can be determined only by receiving a specific proposal from a contractor. Variables not included in the committee's cost estimates include com- petition, experience, expertise and equipment already owned, and time involved in obtaining necessary permits and insur- ance. Several options imply costs of maintenance and repair or of rebuilding or choosing another option in the future. In addition, an appropriate discount rate must be applied when considering future costs. - For example, if OMB's current dis- count rate of 10°h per year is applied, a cost of $5 million 30 years in the future is minor compared with a similar cost next year. Except in the case of beach nourishment, the committee did not attempt to account for inflation in future costs, and all estimates of future costs are in present dollars. In addition, the committee made no attempt to adjust pre- vious cost estimates from other sources. Thus, the dollar values of all previous estimates are valid for the dates of the estimates. 53

54 Criteria, Options, and Evaluation INCREMENTAL RELOCATION: THE PREFERRED OPTION Overview The committee concluded that the best option is to relo- cate the lighthouse a minimal distance--400-600 feet (122- 183 meters)--to the southwest, which will ensure protection for approximately 25 years. Thereafter, the lighthouse should be moved further as advance of the sea requires. Steel lifting beams for the move would be left in place (concealed by sand) to facilitate future moves. Subsequent moves would be less expensive than the first, because much of the work required need be done only once. * The current groinfield would not be repaired under this option. Choice of the initial resting site should be made by NPS; the committee favors an area close to the southwest corner of the present parking lot. This and other areas are dis- cussed under "Site Selection." The committee recognizes that methods for relocating the lighthouse other than the rail and track method described below are available. However, based upon the information currently available to it, the committee believes this method will minimize cost and will minimize cost and ecological damage. Detailed confirmation of the correctness of this approach and the technical details of any relocation must be determined by a contractor, retained by NPS. A conceptual description of the committee's suggestion is outlined below. In preparation for the move, the building's structure would be assessed and minor repairs and reinforcements made as needed. The foundation of the lighthouse would be tun- neled for insertion of a series of needle beams. Then the lighthouse (minus part of its below-surface foundation and The three groins were constructed by the Naval Facilities Engineering Command to protect the U.S. Navy facility north of the lighthouse, although the south groin was installed south of its originally planned location to extend protection to the lighthouse (U.S. Army Corps of Engineers, 1985~. The present committee was asked to consider options to protect the lighthouse, not the Navy facility. If the groins were maintained, they would probably continue to reduce beach erosion in front of the Navy facility and the lighthouse.

Evaluation of the Options 55 the timber mat) would be vertically raised by hydraulic jacks to clear the below-surface foundation that remained. The lighthouse would be lowered onto rollers that rest on multiple horizontal steel-rail beams supported by precast con- crete piles. The entire lighthouse structure would be moved on the tracks with hydraulic jacks and pulled to its new site , where it would be placed on a newly constructed foundation, such as a pile-supported concrete mat (Figure 9~. The total time estimated for the move, including engineering analyses, is approximately 1 year; preparation and relocation of the lighthouse would take fewer than 3 months. The actual relo- cation should not occur during hurricane seasons--summer and fall. It is expected that the light will be nonfunctional during this 3-month period. The keepers' quarters could be moved using standard housemoving techniques. Before relocation, the external structure would be strengthened and reinforced as an integral unit by vertical and circumferential prestressing as discussed in "Risks to the Lighthouse," and as shown in Figure 10. The foundation tun- neling would involve no movement of the tower. Needle beams would be inserted immediately into 3-foot (91 cm) tun- nels; thus, the base of the lighthouse would not be weakened. During lifting, hydraulic jacks would be equipped with mechanical locknuts, and cribbing would be placed close behind; this would limit vertical displacement to less than inch ( 1.3 cm) in case of jack failure. Were a jack to fail, the center of gravity would move about 11 inches (3.2 cm) horizontally. The top would move more, but such displace- ment should have little effect on the stability of the light- house. _ ~. ~. . ~- - - - - , · . Cost of First Move The MTMA Associates report ( 1980) described relocation of the lighthouse in one piece to an area approximately 2,800 feet (850 meters) southwest of the present location at a cost of $2.7 million. The NPS Environmental Assessment ( 1982) estimated $5.9 million, and the Move the Lighthouse Commit- tee (Fischetti et al., 1987) estimated $3.2 million to move the lighthouse to the same area.

56 Criteria, Options, and Evaluation . End beam ~ ~ ~' Walls r A Hydraulic jacks on top of girder it . ,. ~. ~., ,. ~ ,.,~/////~ Lighthouse _ it., ~ _ Id'., ... Y/W ~ ),~ ,. ~ c 1 ~ rig q ~ ·, Concrete piles under / girder Heavy steel rail-beam Girders - pile supported for full length Note: End beams are either very deep prestressed concrete beams or steel trusses FIGURE 9 Schematic drawing of proposed tion. Plan view. Intermediate beam prestressed concrete or steel beam lighthouse reloca

Evaluation of the Options Prestressed 57 Circumferential concrete tie beam \ -Lighthouse wall \ K~ _ .; ,: .~.-'~\\\\\\\~ ,,:,. \\\\\\\ .' b ,' W\\\\\\ ~ Deb / rods ~ - Circumferential prestressing tendons Steel rollers or tellon-lubrite 1 1 1 1 1 1 Hydraulic- - - _ jacks ..... _ - 1 1 I I ~! ~ Two heavy steel wide-flange rail-beams Hydraulic jacks Reinforced concrete main rail girder \ 12 sq. prestressed concrete piles at 100T capacity FIGURE 10 Schematic drawing of proposed lighthouse relo- cation, showing some external reinforcing of the structure. Cross section of A - A from Figure 9.

58 Criteria, Options, and Evaluation The committee estimates that relocation of the lighthouse and its associated structures 500 feet ( 150 meters), including design and construction of a new site, would cost approxi- mately $4.6 million. The marginal cost of moving the light- house an additional distance is estimated at approximately $600 per foot ($1,970 per meter). The committee's cost estimates were based on the follow ~ng: · Current site Sheet piling around excavation; dewatering and excavation; piling; concrete reac- tion/support beams; concrete ring reinforcement; prestressing rods; main support beams; end-sup- port trusses; prestressing; installation of beams, including. tunneling; jacks; cribbing; raising of the structure Rail/track Pile supports, concrete caps, steel beams/plates, rollers or sliding surfaces (steel on polytetrafluoroethylene) · New foundation Pile supports; excavation; material for new concrete foundation; removal of trusses and beams; patching of lighthouse base; backfilling, grading, and landscaping area · Existing structure: strengthening and repairs Joint-bonding of masonry; circumferential stres- sing; vertical prestressing; repairing the gallery, stairs, and windows; removal of external coating and recoating . Site restoration Demolition of concrete track and old site, cutting off or removing piles, restoration of old site, removal of present park- ing lot, landscaping of site $ 750,000 660,000 280,000 470,000 210,000

Evaluation of the Options Moving the keepers' dwellings E· - nglneerlng NPS administration Insurance Replacement of lighthouse Professional liability Contractor9s Profit · Contin£e'ncY 59 200,000 360,000 400,000 200,000 55,000 400,000 600~000 Total Cost of Future Moves $ 4~585.000 By leaving the needle beams in the base of the lighthouse, the cost of a future move is much reduced. Also, the light- house would not need to be cut from its stone foundation a second time. The committee estimates the cost of a future move of 500 feet (150 meters) at approximately $1,600,000 (current dollars) if the move continues in the same direction as the first move. The estimate is based on the following: Reinstallation of external strengthening (i.e., tendons and bands) Uncovering the needle beams, rejacking the lighthouse Railbeams, piles, etc.; construction of 500-foot move track New foundation, and site preparation (e.g., landscaping) E· - nglneerlng Insurance · Contractor9s profit $150,000 105,000 500,000 1 1 5,000 100,000 1 50,000 280,000

60 Criteria, Options, and Evaluation · Contingency200 000 Total $ 1,600~000 Evaluation Structural Integrity: Can the Lighthouse be Moved? The lighthouse is structurally sound (Hasbrouck Hunderman Architects et al., 1986~. Small cracks visible in the structure do not compromise its integrity. The committee concludes that the risk of damage in a properly performed relocation would be minimal and certainly less than that involved in · ·. ~· . ~. . _ ., building a seawall/revetment or leaving the lighthouse at its present site. - ^ ~ .. . .. . ~ ~ _ ~ ~ ~ ~ weight of the granite in the 45-foot lo further reduce the risk of damage to the lighthouse, the committee recommends structural repairs and a variety of measures to strengthen the structure temporarily that are discussed below. The Move the Lighthouse Committee (Fischetti et al., 1987) estimated the weight of the lighthouse at 2,600 tons (2 360 metric tons) the present committee judges that the ~ ~ 13.7-meter) diameter base was underestimated and estimates the weight of the structure at 2,XOO tons (2,540 metric tons). Success in moving structures depends on careful, detailed study and design of each case. However, many large, heavy struc- tures--some larger and older than Cape Hatteras Lighthouse-- have been moved successfully (Appendix C). Examples include a 3,000-ton (2,720-metric ton) masonry wing moved 260 feet (80 meters) in 1949 and the five-story, 2,350-ton (2,130-metric ton) brick Willard Parker Hospital building, moved 60 feet (18 meters) in 1941 (Prentis and White, 1950~; a 3,200-ton (2,900-metric ton) brick and frame church moved 20 feet (6.1 meters) in 1923 (Anonymous, 1923~; a 12,000-ton 10.900-metric ton) 14th century church moved 2,4()() feet ~ , , ~ _ ~ A . ~ _ ~/ ~ ~ ~ \ ~ (730 meters) In Czechoslovakia In 1 Y75 fourths, 1 Y-/Y); and oil-related structures as much as 200 feet (61 meters) tall and weighing up to 35,000 tons (31,700 metric tons) that were moved onshore before being loaded onto barges (Gerwick, 1986~.

Evaluation of the Options Risks to the Lighthouse 61 A potential, but manageable, risk to the structure would be experienced during the acceleration phase at the start of the move. The initial accelerating force must overcome the static friction between the rollers and the rails. The critical moment in moving the lighthouse occurs when the static fric- tion of the mass resting on its temporary supports is broken and the tower begins to move horizontally. The force required to produce an acceleration is a func- tion of the mass of the tower and its supports, according to Newton's Law: F = m x a where F = force, m = mass, and a= acceleration. However, frictional force must also be overcome. Because static friction is much greater than moving friction, the force required to overcome static friction is much more than that required to balance moving friction. As the force of static friction decreases suddenly to the force of moving friction, the lighthouse will begin to accelerate rapidly. The rate of change in acceleration from O to an increasing rate is a "jerk," a dynamic action that tends to change the stability of the mass. This would tend to cause the lighthouse to rock. To minimize this risk, elasticity in the cables should be minimized and controlled, or short rods should be used. If a contractor were to set up a winch at the far end and use wire ropes to pull the structure, elastic strain energy would build in the wire ropes, resulting in a sudden jerk. Inertial forces during such a jerk could be similar to those of a small earthquake. Rather than wire-rope cables, the current state- of-the-art method uses positive displacement jacks with short strokes, reacting against brackets on the rail beams. The jerk can be minimized further by using roller bearings or steel on polytetrafluoroethylene-coated lubrite surfaces, which minimize starting and moving friction. The- accelerating force can thus be limited to negligible values--O.OS times the force of gravity or less. . . .

62 Criteria, Options, and Evaluation Another risk would be settlement of the supporting beams during the move. At each spot along the entire move track, the beams must be able to ~ ~ ~ ^^^^ _ , ~. support the entire weight of 2,800 tons. For this reason, the committee suggests the use of pile-supported beams. The structural integrity of the structure should be posi- tively ensured by a series of steps taken before relocation. Hasbrouck Hunderman Architects et al. (1986) noted the need for a new external tension rod lust below the gallery at the top of the lighthouse. . ,, ~ ,, The committee suggests temporarily placing a new, heavily reinforced concrete tension ring around the base of the lighthouse. ~ Additional tension bands could be placed as necessary at several elevations of the tower and removed after relocation. The committee also suggests consideration of vertical pre- stressing for the tower shafts. This would most easily be done by pairs of tendons, one inside and one outside, around Alternatively, structural steel bracing could be placed outside for the full height of the this method often has been used successfully. The bracing frame also can be used as a scaffold for repairing the coating and windows. The committee further suggests tying the foundation course together by epoxy injection to bond the foundation blocks into an integral unit. Holes should be drilled and high-strength bars inserted and stressed. The horizontal move of the lighthouse must be level. The cost estimates above do not include significant changes in elevation. In addition to the structural risks, the committee heard and read several comments concerning risks associated with dewatering, which is required for construction that occurs below the water table. the foundation timbers. the tower7s circumference. tower: ~ · ~ ~ One concern was onset of dry rot in If dewatering is for a duration of only 3 to 6 months, then the fungus that causes dry rot should not have the opportunity to cause appreciable deteri- oration. Another concern was settlement of the sands under the foundation, because reduction of the pore-water pressure in the sands could allow them to consolidate. Such settle- ment generally is uniform and can be reduced to acceptable limits by restricting the depth of dewatering to the elevation of the foundation timbers.

Evaluation of the Options 63 Site Selection The committee did not assess the merits of all possible sites for lighthouse relocation. Instead, it considered three areas (Figure 11) that met the following constraints: · The route to the site must be a straight line. This would minimize moving costs and the number of times the lighthouse would need to undergo the shock of acceleration. e The move track must not traverse any extensive wet- lands. Wetlands are habitats of widely acknowledged ecolo- gical value (e.g., Teal and Teal, 1969; Nixon, 1980; Odum et al., 1984) and have broad protection under the Clean Water Act (Platt, l9X7~. If the move track traversed any large wetland, some disruption--at least temporary--necessarily would take place, perhaps even involving filling of low areas until after the move were completed. This would add econo- mic and ecological costs to the move. . The move track must not encounter any substantial topographic relief, such as the relict dune ridge and swale system along the Buxton Woods nature trail. Substantial excavation and filling would be required to prepare a level move track. Such preparations would add to construction and restoration costs. Furthermore, such a move would dis- rupt large areas of vegetation, because the move track would need to be substantially wider than the approximately 60 feet (18 meters) required in more level terrain to permit stable sloping transitions to the natural elevation at the edges of the move track. The lighthouse must remain within the boundaries of the Cape Hatteras National Seashore. This reflects a practi- cal need to avoid costs and political constraints. In addition, the lighthouse should remain in the general vicinity of Cape Hatteras to illustrate its historical role as a warning to mar- ~ners.

64 Criteria, Options, and Evatuation Hi= - _ NAT'L SEASHORE BOUNDARY _ ~ J ~ u s NAVY FACIUTY GROIN - , . . . I..:... i,,.:,- I-:;,. ~_AR=~6~' ~ LIGHTHOUSE ~7 COAST GUARD- ': it ;- . . . STA FAR ... .. ; (1 2,000' SW) my, (J~,£-~_~: ~ 1 1 1 1 3,000 FEET REGREW PIT FIGURE 11 Cape Hatteras, showing major features and the three potential relocation areas considered by the committee. Adapted from aerial photographs and United States Geological Survey map. (Stippled areas represent marshy areas. Small pockets of wetlands are not shown.)

Evaluation of the Options 65 · The move should succeed in postponing immediate at least 100 years. This follows directly from the National Park Service's request for a long-term solution on this time scale. threat from shoreline retreat for The only sites that meet these criteria lie within a narrow band extending approximately southwest from the lighthouse's present location and running approximately parallel to the paved road leading from the lighthouse to the parking lot near the nature trail. The committee considered three gen- eral areas along this path. The Nearby, Favored Area parking lot, 400-600 feet present position. · · ~ This area is near the southwest corner of the present ( 122-183 meters) from the tower's ~ he precise location of the new site would be determined by aesthetic and site-design considerations. Any future moves would be much less expensive if they con- tinue in the same direction as the first move. Factors that aided in the committee's selection of this nearby area were: . The move would cost less than a longer move. · Ecological damage would be minimized. The historic and aesthetic integrity of the lighthouse site would be preserved. The lighthouse would remain close to the beach and the ocean. The option is a flexible response to a dynamic problem. This area offers many aesthetic advantages. The tower would remain close to the shore, almost unchanged in appearance to those approaching it, but safe from storms. A move to this area would avoid much ecologically valuable land that an extended move would require, and the beach shoreline would remain a smooth curve. The committee expects that the existing groins would be left in place, but no major repairs would be undertaken.

66 The Intermediate Area Criteria, Options, and Evaluation The committee considered the area broadly described by the Move the Lighthouse Committee (Fischetti et al., 1987~. The area is approximately 2,800 feet (850 meters) southwest of the present location of the lighthouse. near the parking lot at the head of the nature trail. _ , _ At current rates of shoreline retreat, this area would provide protection to the lighthouse for at least 100 years. However, uncertainties associated with estimates of the position of the shoreline increase with the period of the prediction. The committee judges the area east of the paved road that leads to the campground to be preferable to the west, because the vegetation is less dense, the terrain is flatter, and the wetlands are less extensive. Furthermore, a site east of the road would not intrude on the nature trail or the dense and rare maritime forest in the relict dune and swale system of Buxton Woods west of the road. A location near the road would facilitate access during preparation of the move track and probably maximize distance from the eroding east-facing shoreline. A protective fringe of vegetation bet- ween the road and the new site of the lighthouse could help preserve the tradition of isolation of the lighthouse and its associated structures from the violation of historic values implicit in the close presence of roads, cars, and parking lots. Public appreciation of the historic, isolated nature of the lighthouse keeper's experience might be achieved best by use of such natural vegetational buffers. The Distant Area The third area considered by the committee is near the south shore of Cape Hatteras, approximately 12,000 feet (3,700 meters) southwest of the lighthouse's present position. A move to this area would place the lighthouse and the associated structures close to the south shore of Cape Point. This shoreline is accreting, so protection against future shoreline erosion likely would be effective for more than 100 years. The area is characterized by flat topography of low vegetation, mostly grasses. If the lighthouse were relocated to this general area, it again would be close to the sea, at

Evaluation of the Options 67 least until the shoreline accreted some distance farther south; erosion protection would be maximal; and the site would be naturally open. The location is isolated from most other park structures except the nearby campground. However, relocation to this area would cost nearly $7 million more than the move to the near area and would damage ecologi- cally valuable areas. These disadvantages are sufficiently serious that the committee did not consider the area further. Ecological Consequences of Moving the Lighthouse Ecological costs of moving the lighthouse are temporary or permanent habitat alteration in the approximately 60-foot ( 1 S-meter) wide path of the move track; potential water-table depletion and saltwater intrusion during the making of con- crete for the track and new foundation; and habitat destruc- tion for creating the 6- to S-acre (2.4- to 3.2-hectare) site for the repositioned lighthouse and associated structures. Habitat Damage Along the Move Track Ecological damage along the move track depends on the precise location and design of the new site for the lighthouse complex and the path taken to reach it. The Near Area If the lighthouse were moved to the near area, little alteration of natural vegetation would occur, because most of the move would proceed across grass lawns and pavement. The Intermediate Area If the lighthouse were relocated to the intermediate area, vegetation in a track of 60 x 2,800 feet ( 18 x 850 meters) would be disrupted at least temporarily. The ecological dam- age would not be great, because the sparse dune grasses

68 Criteria, Options, and Evaluation (mostly Spartina patens, but also Ammophila breviligulata, Panicum amarum, and Uniola panicuZataJ, low shrubs (Myrica cerifera, Ilex vomitoria, Juniperus virginiana, Baccharis hali- mifolia), and low trees (mostly Quercus virginiana) that must be cleared can be reestablished fairly rapidly. Many of these plants are adapted to disturbance, especially from washover (Holier, 1973; Godfrey and Godfrey, 1976; Hosier and Cleary, 1977~. Seeding, transplanting, and fertilizing can be used to speed recovery of the grasses. Because the area of the move track would be surrounded by vegetation and open to salt spray only to the northeast along the move corridor, recov- ery of natural shrubs should take place quickly. Topsoil would need to be handled carefully during preparation and restoration of the move track, because soil organics accumu- late very slowly on coastal barriers. Their absence would greatly retard vegetation recovery (Au, 1974~. The most eco logically valuable areas that might be affected in moving the lighthouse to the intermediate area are small areas of wet- lands that contain Juncus and other marsh plants, but that total less than one-half acre (.2 hectare). However, reloca- tion of the lighthouse would affect only a small area, and the disturbance would be temporary. After the topography were restored, recovery of wetland plants would proceed and could be aided by transplantation and fertilization (Lunz et al., 1978~. . . - Habitat Lost to the New Site ~, The amount and type of habitat lost to provide the new site for the lighthouse complex would depend greatly on the specific site chosen for relocation and its design. The Near Area If the lighthouse were moved only a short distance to the southwest, preparation of the new site would necessitate only clearing of grasses, low shrubs, and pavement. Revegetation of the previous site of the lighthouse would replace the plants lost at the new site with a very similar species com- position. Thus, the short move would entail little net ecolo

Evaluation of the Options 69 gical loss due to clearing and preparing a new site for the relocated lighthouse complex. The Intermediate Area If the intermediate area were selected, the habitat that would be lost from Buxton Woods would have ecological con- sequences. NPS holdings in Buxton Woods are only about one-third of Buxton Woods, so any loss would be significant. Furthermore, any loss of Buxton Woods habitat would violate the November 1979 agreement between NPS and North Caro- lina, which registered all NPS Buxton Woods holdings as a "natural heritage area." This prohibits any habitat disturb- ance or alteration in Buxton Woods. However, a site in this area would not involve loss of tall, dense maritime forest but would affect low shrub thicket and sparse taller trees. a common habitat type on coastal barriers. Of the new site would reduce habitat loss. Water-Table Depletion , ~ Thoughtful design It will be necessary, and not difficult, to ensure that the water table not be lowered in relocating the lighthouse. If too much water were drawn from the narrow lens of fresh water that constitutes the water table of Hatteras Island, consequent saltwater intrusion might endanger the maritime vegetation of the island. Current hydrological estimates (R. Heath, United States Geological Survey, retired, Raleigh, N.C., personal communication, 1987) suggest that fresh water is being tapped at about half the maximal rate that Hatteras Island can provide without saltwater intrusion. This is one reason that much of Buxton Woods has been proposed as an "area of environmental concern" by the North Carolina Coastal Resources Commission to restrict the types and density of development that would create more demand on the limited freshwater resource. Even if all the water needs for concrete used in the move track and the new foundation were met by water-table extractions, the amount--about 242,000 gallons (916,000 liters) for a move of 2,800 feet (850 meters)--probably would be too

70 Criteria, Options, and Evaluation small to have any serious effect on the water table and biota. Nevertheless, the committee recommends that no fresh water be taken from the water table for construction. The concrete slabs needed for the move track could be prefabri- cated or made with salt water, which is satisfactory when concrete is not expected to be permanent. Water needed for construction of a new foundation (approximately 12,000 gallons (45,000 liters)) could be transported to the new site. These measures would remove all potential risks of ecological damage from water use. - Recent Legislation Moving the lighthouse 500 feet is consistent with recent federal legislation and North Carolina's regulations. Section 1306 of the National Flood Insurance Act of 1968 recently was amended (section 544 of Public Law 100-242, the Housing and Community Development Act of 1987) and provides some insurance coverage for buildings that are threatened by erosion to permit them to be relocated before they collapse. Buildings containing four dwelling units or fewer must be relocated landward 30 times the annual erosion rate (30-year setback requirement); larger buildings have a 60-year setback requirement. Furthermore, North Carolina's Administrative Regulation 15 NCAC 7H Rule .0306 requires a 30-year setback for new buildings less than 5,000 square feet in base area and a 60-year setback for larger buildings. Rule .0306(k) requires structures relocated with public funds to conform to the above setback requirements. (Although Cape Hatteras Lighthouse covers less than 1,600 square feet, it clearly is a large building.) North Carolina calculated the erosion rate for Cape Hat- teras Lighthouse at 9 feet per year according to rule .0304(1 Baby; an updated estimate of 7 feet per year is pending approval. A move of 500 feet would provide erosion protec- tion for slightly more than 55 years according to this value for erosion rate (71 years according to the updated estimate). The Army Corps of Engineers ~ 1985) gives the rate of erosion at the lighthouse at 5.2 feet per year from July 1945 through May 1983. A move of 500 feet would provide erosion protec- tion for 96 years according to this value.

Evaluation of the Options 71 In addition, the North Carolina Coastal Resources Commis- sion made a declaratory ruling that Cape Hatteras Lighthouse is a unique cultural resource and may be protected in any way that does not interfere with natural migration of the shoreline (June 2S, 1985~. The committee therefore believes that moving the light- house back approximately 500 feet would be in accord with the above legislation and regulations. In addition, it would provide for further moves as the shoreline approaches the lighthouse some time in the future. · ~ ~ ~ . ~ Summary The committee rated the option of relocating the light- house to the near area as the most reliable and involving the fewest risks. This option also rated well in terms of cost- effectiveness, preservation of historic and aesthetic values ~. . ~. ~ . ~ . . · ~· · . and accordance with relevant pUbllC policies. - By moving the lighthouse and the associated buildings, the entire complex could be preserved and its historical relation- ships to habitations and service structures left intact at a new setting. The setting might even be improved by reloca- tion: plastic sandbags and trampled dunes from uncontrolled passage could be cleaned up and repaired; remnants of old groins would be less visible. The cost of preparing and relo- cating the lighthouse, all the associated buildings, the park- ing lot, and the access trails, estimated by this committee to be $4.6 million, is comparable to the cost of other options and lower than some. Furthermore, long-term costs (other than routine maintenance) do not apply to the relocation option, except those anolied to a further move. , ~. · ~ _ _ ~. ~. ~^. But even that would COSt less than the ~ 1rst move and probably would not be needed for 25 years or more. Relocating the lighthouse after careful consideration of its historic value and the relevant cr~ter~a--instead of trying to protect the lighthouse in situ--would be an exemplary response by NPS to the generic problem of shoreline erosion. Relocation is consistent with NPS policies to let natural processes proceed unhindered and to use the national parks as models of wise management of natural and cultural resources. Moving also is consistent with the NPS mandate _ _

72 Criteria, Options, and Evaluation to preserve historical landmarks and structures for future generations and respects policies of the North Carolina Coastal Resources Commission. Relocation probably would attract much media attention, providing NPS an opportunity to educate a large national audience on the nature of coastal barriers. Relocation has some negative aspects. Several local res- idents expressed strong opposition to relocation, preferring that the lighthouse be preserved in situ, despite the greater risks to the structure that this approach would entail. Relo- cation also implies a potential loss of several acres of natural habitat, depending on the location chosen. If the short move is chosen, some space already devoted to the lighthouse complex might continue to be used for that purpose. Any habitat loss could be minimized by careful site selection and design. The rarity of maritime forest on the Outer Banks renders a potential loss of habitat at the intermediate area of some ecological and environmental significance. Because NPS owns and controls only about one-third of Buxton Woods, it might be possible to mitigate the loss of this acreage by NPS acquisition of additional Buxton Woods acreage at the park boundary. Such lands are likely to be developed in the future, so acquisition and preservation would be a form of compensation for clearing the new lighthouse site. However, such acquisition would require congressional approval and would add to the cost of this option. PROTECTION OF THE LIGHTHOUSE IN SITU Groinfield Rehabilitation Without Revetment This option involves repairing and shortening the existing three groins, and constructing a fourth groin approximately 500 feet ( 150 meters) long and 500 feet south of the existing third groin. A fifth groin might be needed another 500 feet to the south to promote beach accretion southeast of the lighthouse. Some beach nourishment would be required at least initially to start accretion between the old and new groin or groins. Subsequent beach nourishment would be determined by the incidence of major storms.

Evaluation of the Options 73 The northernmost two groins, 530 feet ~ 162 meters) long, are 1,200 feet (366 meters) and 550 feet ~ 168 meters) north of the tower. The south groin, 610 feet (186 meters) long, is about 100 feet (30 meters) south of the lighthouse (U.S. Army Corps of Engineers, 1985~. Cost MTMA Associates (1980) estimated an initial construction cost of $3.2 million for groinfield expansion and beach nour- ishment. The estimate included $235,000 to construct a new 450-foot (137-meter) groin and $2,934,000 to pump 500,000 cubic yards (380,000 cubic meters) of sand. No money was budgeted to repair existing groins. The subsequent costs for repair, maintenance, and renourishment were estimated at $63 million over 100 years. NPS ~ 1982) estimated the construc- tion cost of a new groin and replacement of existing groins without beach nourishment at $4 million with a 50-year addi- tional cost of $12 million. The committee estimates the initial cost of this option to be $3.7-$4.7 million. This includes $ 1 million for one new groin, $1.9 million to repair the existing groins, and $800,000 for 300,000 cubic yards (230,000 cubic meters) of beach nour- ishment. A fifth groin, if constructed at the same time as the fourth, would add another $ 1,000,000. This does not include additional costs for renourishment, even in the absence of major storms. Evaluation Deprivation of sand to the downdrift shoreline resulting from expanding the groinfield is not viewed as a problem. Unlike developed shorelines with multiple owners, the area that would be affected is owned by NPS and is unimproved, so a slight increase in the rate of shoreline retreat in such areas is acceptable. Despite the favorable conditions for groins at this site, construction of groins departs from NPS policy by interfering with natural processes and is contrary to the policies of the North Carolina Coastal Resources Commission. However, nat

74 Criteria, Options, and Evaluation Ural processes already have been interrupted at the site, and variances can be obtained from the coastal regulations when public benefits are high and adverse consequences are mini- mal. Continued use and expansion of the groinfield would have some advantages as a short-term measure for protecting Cape Hatteras Lighthouse. The visual obtrusiveness of the struc- tures would not be much worse than that caused by the three present groins and might be lessened if the dysfunc ~ The groins would continue to create wave characteristics favored by surfers. The lighthouse could remain at its present loca- tion in its historical conjunction with the other structures at the site. Although groinfield improvements are a possible short- term approach to the problem of - preserving the lighthouse, this option merely postpones the need to make a long-term choice. And, unlike relocating the lighthouse, it does not make future protective measures easier or less expensive. Groins on this high-energy shoreline will need frequent attention unless they are very well constructed. The groins initially installed in 1969-70 were damaged seriously in the early 1 970s; they were repaired in 1975, but they are again in need of repair and modification (Figure 12~. The commit- tee's estimates for this option were based on groins that are likely to last 20 years without repair. Even an expanded and well-maintained groinfield cannot ~ : ~ ~~~ ~ ~ the storm surge and wave action of a 1 OO-year storm or hurricane. The groins and beach could be overwhelmed by such an event. The committee does not favor this option because it would not protect the lighthouse against severe storms, recurrent maintenance costs probably would be needed, and it would not ensure long-term protection for the lighthouse. tlonal outer segments ot the groins were removed. ensure Protection of the lighthouse against Groinfield Rehabilitation with Revetment This option includes all aspects of the previous option. It also entails construction of a below-grade-level concrete caisson revetment to prevent undermining of the lighthouse (Figure 13~. This would be constructed by the established

Evaluation of the Options o z 75 cat en cat a' cd sit o cat o · _ cat cat sit an a_ V ce >~ ·- so - v ~s ~ .o - o cot ~ =: ,= 4 L =4 ~4 o o _ =\ ~ _ .

76 . ~ FIGURE 1 3 meet. Criteria, Options, and Evaluation +9 f / J DILL ,., REINF. CONCRETE SLAB l ~L4~ / CHEMICALLY STABILIZE (OPTIONAL) REINFORCED CONCRETE WALL CONSTRUCTED IN SLURRY TRENCH - CONTINUOUS AROUND PERIM ETER OF FOUNDATION. Schematic diagram of proposed -35 caisson revet

Evaluation of the Options 77 "slurry-trench diaphragm-wall" technique, in which a full- ciepth concrete wall would be constructed in six 1 2-foot (3.7meter) segments. In this application, the joints between segments would need to be reinforced (several proprietary methods are available to accomplish this). The segments would be cast in trenched slots and kept open with bentonite slurry. Then, a thick, horizontal, reinforced concrete slab would be constructed between the top of the wall and the base of the lighthouse. The joint would be unbended to accommodate differential displacements caused by differential settling. Recharging wells would be installed around the base to prevent dry rot of the existing timber-mat foundation under the lighthouse; such wells would be 11-inch (3.S cm) diameter perforated pipes, with a cap that periodically would be filled with water. They could be either inside the lighthouse structure or around the outside, whichever the architect thought would be least noticeable. This caisson revetment is not a substitute for the sea- wall/revetment of the U.S. Army Corps of Engineers, because it does not protect the lighthouse from battering by large storm waves that would occur after the shoreline retreated to the lighthouse. Therefore, the caisson revetment would have to be accompanied by rehabilitation of the groin field to maintain the protective beach in front of the lighthouse. Several lighthouses survive indefinitely in the face of vio- lent waves that batter them directly, for example, Minot's Ledge Lighthouse in Cape Cod Bay and the Eddystone Light- house in the English Channel. Those lighthouses, however, are constructed of massive, interlocking granite blocks spe- cially designed to withstand such assault (Hague and Christie, 1975~. The brick Cape Hatteras Lighthouse, constructed con- ventionally, would not survive such conditions. Thus, although this option would protect the lighthouse against undermining and would provide some protection against storm surges and waves, it might not protect against a major hur- ricane.

78 Cost Criteria, Options, and Evaluation MTMA Associates (1980) estimated a construction cost of $2.6 million for partial revetment, one new groin, modest repairs to existing groins, and initial beach nourishment with 235,000 cubic yards (180,000 cubic meters) of sand. This option costs less than the previous option because it provides less beach nourishment. Maintenance' repair, and renourish- ment costs were estimated at $31 million over 100 years. The committee estimates the initial construction costs to be $4.7-6.7 million, including initial beach nourishment of 300,000 cubic yards of sand. Renourishment costs could not be quan- tified. The committee's cost estimates include construction of a modern groin that is likely to last for 20 years without repair and thorough repairs of the three existing groins. The committee's estimates are as follows: Revetment wall (caisson): materials, design, construction · Construction of two new groins at $661,500 each · Repair of 3 existing groins at $242,670 each · Five trestles for construction and repair, reusing the materials five times at $376,000 each time $529,000 1,323,000 72S,000 · Overhead and profit · Engineering and design Beach nourishment with 300,000 cubic yards (229,000 cubic meters) of sand Total 1,880,000 934,000 500,000 800~000 $6~694.000 If only two groins were repaired and one new one con- structed, the cost would be reduced by approximately $2 million. Evaluation The caisson revetment would protect the lighthouse against undermining and to some extent against storm surges and waves. However, this option might not provide protec

Evaluation of the Options 79 lion against a major hurricane and would not provide long- term protection for the lighthouse. Depending on the frequency and severity of storms, maintaining the shoreline in front of the lighthouse would become increasingly costly, and perhaps impossible. The lighthouse would need to be moved, which probably would cost 50% more (in constant dollars) than it would today, when the lighthouse and its structures are still some distance from the sea. This option conflicts with national and state policies concerning barrier proposed revetment places a new, hard structure on the coast--albeit below ground. Because of these disadvantages, the committee did not favor this option. However, of the options that would pre- serve the lighthouse in situ by defensive means, this offers some protection to the lighthouse at relatively low cost. . in, , . coastlines, because the Seawall/Revetment This option was developed by the U.S. Army Corps of Engineers (1985~. The lighthouse and the adjacent oilhouse (but not the keepers' dwellings) would be encircled by an octagonal reinforced concrete seawall constructed symmetri- cally with the base of the lighthouse. The design has four major structural components: a gravity-mass concrete sea- wall, a prestressed concrete sheetpile cutoff wall extending from the toe of the seawall to 16 feet (4.9 meters) below mean sea level (MSL), a stone revetment fronting the sea- wall, and a compact earth fill backing up the seawall (Figure 14~. The top of the seawall would rise 23 feet (7 meters) above MSL ( 15 feet (4.6 meters) above grade at the base of the lighthouses, with a public promenade encircling the inter- ior edge of the seawall 20 feet (6.1 meters) above MSL-- approximately 12 feet (3.7 meters) above the existing ground elevation around the lighthouse base. The earth fill would begin at the granite fence base 48 feet (14.6 meters) from the base of the lighthouse and would rise toward the prome- nade at a moderate 25% grade. Each segment of the seawall would be 129 feet (39.3 meters) along its toe face, which would be 157 feet (47.9 meters) from the center of the light house. The stone revetment would extend 51 feet ( 15.5

80 Criteria, Options, and Evaluation ~ 0 ~= ~ ~ ~ O ~ ~ ~ . Oz ~ LL It \ oz iN . q.~\\\ .' f~\\\\ . /\\\\ ~\\\\\ . ~\\\\ ,. \ , .. ~\\\\\ `~\\\\\~ . /\\\\\\ \\\\\\ . \\\\\\' \\\ \\\M . \\ . \\\\\ \N .\\\\\\ \ . .\\\\\\\ . \\\\\\\ . \ \ \ \ \ \ \ , .\\\\\\\ ,. \\\ \\\\ \\\\\\\1 \ \ \\\ \ \ \\\\\\\ \\\\\\ n \\\~` - ~D c c - o) - J C O _ - 40 U ~n ~ :3 1 O) :~ o - CO 2 - ~D c o o U. - o N cn o O + G Z \ O ~ ~ ' ~E'. :# U. ~ [L.l u) I ~ CO ~ LU ~ C~l: ~ o N g ~ 1 -~ ~O ~ 1 ~ U) ~ ·_ o CO o V - o 3 G m G J - o - ~n J LL cn z 2 0: LL UJ ~c z O z c~ o 6 ~ CO o ·_ 4 - C) U) - - 3 - co 4 - ~ - - LM oo - c~

Evaluation of the Options 81 meters) beyond the outer edge of the seawall, reaching a distance of 208.5 feet (63.6 meters) from the center of the lighthouse (Figure 15~. Initially, only the six seaward sides of the seawall would be constructed, leaving the west and the northwest landward sides open to facilitate public access to the lighthouse. However. the entire revetment and the sheetpile cutoff wall Below ground level would be constructed to encircle the base of the lighthouse. Upon encroachment of the sea, flood walls would be constructed, eventually closing off the two oven faces of the seawall on the landward side (Figure 16~. In constructing the seawall/revetment, excavation and dewatering would be required to place the base of the revet- ment 10.5 feet (3.2 meters) below MSL and the base of the seawall 1 foot (30.5 cm) above MSL. To facilitate this oper- ation, a temporary sheetpile coffer cell probably would be constructed. The cell would be confined to the immediate area of structure. After elevation cm) MSL ~. ~ _ . - _ excavation or constructed to encircle the entire the initial excavation reached the prescribed top of the concrete sheetpile cutoff wall +3 feet (91 along the seaward faces and +5.5 feet ( 1.7 meters) MbC along the landward faces, the sheetpiling would be placed by jetting and driving. Thereafter, additional - excava- tion and dewatering would be necessary on both sides of the sheetpile to permit geotextile filter fabric and stone revet- ment to be placed. This excavation would need to be at least 60 feet (18 meters) wide and would need to extend 10.5 ~ ~ ~ ~ (3~5 meters) below the top of the timber-mat foundation of the lighthouse. The center of the excavated area would be ap- proximately 175 feet (53 meters) from the center of the lighthouse. The water table at the excavated area is esti- mated at +1 foot (30.5 cm) MSL. feet f3.2 meters) below MSL--anoroximatelv 11.5 feet Cost MTMA Associates ( 1980) estimated a cost of $4.5 million initially, $1.1 million in maintenance cost over 100 years, and a total cost of $5.6 million. The U.S. Army Corps of Engineers ( 1985) estimated a $5.72 million construction cost

82 1 'I 1 ~1 ~ _ _ ; _ _ ... j: -I ~\~ 71 1 ~ \~ §8 8{ Criteria, Options, and Evaluation cot s: ._ o Q sit o V so On o Lo 4_ Ct - - Cd 3 cd cn 3 · _ > Lo-

Evaluation of the Options FIGURE 16 Artist's impression of Cape Hatteras Lighthouse surrounded by seawall 10-20 years after construction. SOURCE U.S. National Park Service, 1982. 83

84 Criteria, Options, and Evaluation (including closing the seawall in response to recession of the shoreline) with an annual maintenance cost of $16,000. (This estimate was vague regarding details of the project; no dimensions were provided, and "seawall" and "revetment" were used interchangeably.) NPS ( 1982) estimated a cost of $5.3 million, with no maintenance costs. The Move the Light- house Committee (Fischetti et al., 1987) estimated a construc- tion cost of $6.7 million, with a 1 OO-year maintenance cost of $54 million, based on the U.S. Army Corps of Engineers (1985) specifications. This committee estimates approximately $6 million in con- struction costs to construct the seawall/revetment proposed by the Army Corps of Engineers, with substantial but unquantifiable maintenance and repair costs. Evaluation The seawall/revetment option would require a long con- struction phase-- 19 to 20 months--during which the light- house would be exposed to potentially serious risks. The extensive excavation required to install sheetpiling and the stone revetment could endanger the foundation of the light- house if a severe hurricane with surging waves hit the widely exposed area and breached the temporary cofferdam. This presents the greatest construction-related risk to the light- house of all the options evaluated. The committee judges that the U.S. Army Corps of Engineers's estimated annual maintenance cost of $16,000 was unrealistically low. Seawalls and revetments constructed in areas of high wave energy often need maintenance and repair after a time, as illustrated by experience with structures at South Padre Island, Texas; Seabrook Island, South Carolina; Sines, Portugal; Island Esther off Seal Beach, California; Pacifica, California; and other California examples discussed by Fulton-Bennett and Griggs ( 1987~. The committee judges that, to ensure long-term reliability, the proposed seawall/ revetment probably would need expensive maintenance and repair. Interlocking concrete sheetpiling behind the toe revetment might move if stones in the toe revetment were rearranged during a major storm. Sand could leak rapidly, followed by undermining and local seawall collapse. The

Evaluation of the Options 85 potential scour adjacent to this seawall, exposed to the Cape Hatteras storm-wave climate, could threaten the structure during its design life. Such partial failures would require · - expensive repairs. In preserving the nation's historical heritage, NPS assigns significance to the total setting of the landmark, including aesthetic values. The seawall would greatly alter the setting; lighthouse, dine octagonal Grouse base, with its distinctive red- brick panels framed in granite, would be obscured from outside the seawall. In addition, the light house keepers' quarters would be separated from the light house. As the shoreline receded and the enclosed lighthouse became a tombola or completely separated from land, pres ervation of the other buildings would require relocation land ward, away from the lighthouse. Construction of a seawall/revetment probably would accelerate loss of the treacle in front of the structure. In any event, when the eroding beach reached the structure, the structure would interrupt continuity of the beach and pose an obstacle to passage along the water's edge. The initial construction cost estimated by the U.S. Army Corps of Engineers (1985~--$5.6 million--is high but not out of line with other options for a permanent solution. a seawall would compete visually with the especially from nearby. .. .. .. .. . . . . _. . ~ ~ . ~ . ~ How- ever, the committee found the estimate for maintenance-- $16,000 per year--to be unrealistic, because of periodic requirements for replacement of riprap at the seaward toe. Some localized failure related to storm and scour damage would probably occur within the next few decades. If this Damage were not repaired, would ensue. Although surrounding Cape seawall/revetment is technically not favor this option because: . large-scale structural collapse Hatteras Lighthouse with a feasible, the committee does _' _ _ __ ( 1 ) the risks to the light house during the construction phase would be serious; (2) reliability would be uncertain in the long-term; (3) the integrity of the historic site would be destroyed; (4) a major coastal structure of this kind is not in accord with the letter or spirit of local, state, and federal coastal guidelines; and (5) the unknown maintenance costs for this option likely would be high.

86 Criteria, Options, and Evaluation Artificial Reefs This option involves submerged obstructions seaward of the lighthouse to diminish wave energy and promote beach accretion in front of the lighthouse. Such artificial reefs could consist of rubble mounds, concrete caissons weighted with sand and stone, concrete or steelpile structures of vari- ous configurations, or surplus ships filled with sand and stone, as considered by the committee in its interim report. The latter allows construction to proceed intermittently, ves- sel by vessel, as weather permits. Construction could be extended as advisable and economic. The number of obstructions required would depend on their size, condition, and distance offshore. The committee envisioned placing obstructions far enough offshore to be entirely submerged, so a large number of them might be required. Cost In view of the many uncertainties associated with this option, the committee is unable to estimate costs. Evaluation Any submerged object of sufficient size could serve as an artificial shoal that reduces wave energy by causing the waves far from shore to break and dissipate energy in tur- bulence, rather than moving beach sand. The Hatteras offshore is strewn with more than 100 submerged wrecks; these probably have contributed to the longevity of this pro- truding section of coastline. Deliberate sinking of ships would require some costly preparation and cleaning to rid them of oil and other contaminants, a disadvantage that could be avoided by constructing artificial reefs from other materials. In a major hurricane, very large waves can occur in deep water. As they approach the shore, their height is limited by water depth. In 30 feet (9 meters) of water, with an expected storm surge of 9 feet (2.7 meters) when the astro

Evaluation of the Options 87 nomical tide is 4 feet (1.2 meters), a wave could be 32 feet (9.8 meters) high from trough to crest. If allowed to pro- ceed to the beach, the run-up and turbulence would be dis- astrous to groins and foreshore. If a storm lasted long enough, it probably would undermine and destroy the light- house foundation and topple the tower. A submerged artificial reef constructed in a suitable depth and location and strong enough to withstand the turbulence would cause such waves to break, expending most of their energy on the lee side. A depth of 16 feet (4.9 meters) would support a wave about 12 feet (3.7 meters) high. Such a wave might be reduced by vortex effects in the lee of the reef before breaking on the beach. The beach would increase in width with time because of the sheltering effect of the reef. Time-lapse photographs illustrate how a discontinuous offshore impediment has caused shoaling and widening ot beaches on other coasts (U.S. Army Consequently, the more time gasses after reef construction before a major storm, the bet- ter the protection that Is afforded to structures near the shore. The reef would not protrude above water level at any time and would be visible only during normal heavy weather as a line of foam and breakers. Suitable navigation aids sup- plementing the Diamond Shoals beacon and bell would serve to warn small boats and shallow draft vessels. Thousands of miles of shoreline in many parts of the world are so pro- tected by natural coral formations. The high wave energy of the east-facing shoreline at Cape Hatteras might reduce the effectiveness of artificial reefs as offshore breakwaters. In the wave conditions near the light- house, artificial reefs would not be expected to retain their structural integrity or position indefinitely. Therefore, large but unquantifiable maintenance costs are associated with this option. The committee is unable to cite an example of artificial reefs in areas with wave energy as high as that at Cape Hatteras. Although construction of submerged artificial reefs is attractive in many aspects, it would require substantial study to produce reasonably precise estimates of the size and number of obstructions needed, the cost of construction, and probable effectiveness. , . ~ . ~ . ~ ~. - Corps of Engineers, 1984~. . . ~. . · . . . · . .

88 Criteria, Options, and Evaluation The many uncertainties concerning construction, func- tional lifespan, initial and continuing costs, and effectiveness constrains the committee from favoring this option. Offshore Breakwaters and Groins Under this option (NPS, 1982), four breakwaters con- structed of rock and rubble would be constructed within 200 feet (61 meters) of the shoreline. Three breakwaters would be perpendicular to each of the existing three groins; the fourth would be placed about 500 feet ( 150 meters) south of the southernmost groin. An additional short groin would be constructed about 500 feet south of the fourth breakwater. The breakwaters would be visible from the shore. Cost The breakwater system described by NPS (1982) was estimated to cost $4.4 million and did not include mainten- ance costs. The committee estimated this option would cost $5 million, with unknown maintenance costs. Evaluation This option would interfere with natural processes, which would violate NPS policy and alter the beach contrary to the regulations of the North Carolina Coastal Resources Commis- sion. Because the shoreline is expected to retreat during the . . next 1( 0 years, this solution would be effective only for a limited period. The breakwaters would be visible from shore and might pose hazards to surfers, swimmers, and boaters. At an estimated cost of $5 million, this solution does not compare well with other short-term measures. Furthermore, this option does not conform to relevant policy guidelines and affords uncertain long-term protection of the lighthouse.

Evaluation of the Options 89 Artificial Seagrass This option involves installation of commercially manufac- tured artificial seagrass in the surf zone to trap sand and induce beach accretion or reduce erosion. Natural and arti- ficial seagrasses have been employed successfully elsewhere as baffles to current flow, resulting in enhanced sediment deposition and bottom stabilization (Ginsburg and Lowenstam, 1958; Orth, 1977; Peterson et al., 1984~. However, seagrass was installed in 1981, 1982, and 1984 at Cape Hatteras with- out these results (U.S. Army Corps of Engineers, 1984; Rogers, 1986~. Cost Because the previous installations of seagrass at Cape Hatteras proved ineffective, a cost estimate for this option is irrelevant. Evaluation Artificial seagrass ("Seascape") was installed three times in the lighthouse vicinity without the desired results (Appen- dix A). This method has- been applied successfully only under con- ditions of far less wave and current energy, less turbulence, and less intense oscillatory water flow than are present at Cape Hatteras. In southern California, a carefully controlled and monitored experimental installation of artificial seagrass did not effectively alter beach dynamics (Jenkins and Skelly, 1987~. None of the applications of Seascape at Cape Hatteras promoted beach accretion. In addition, Seascape fabric and its anchoring mechanism clearly are unable to withstand the strong bottom shear forces characteristic of the surf zone at Cape Hatteras Lighthouse (Rogers, 1986~. The committee acknowledges the appeal of a solution that contains no visible intervention. Nonetheless, application of artificial seagrass would not build up the beach, significantly reduce erosion at Cape Hatteras, or protect the lighthouse.

90 Criteria, Options, and Evaluation Beach Nourishment Sand from nearby sources could be pumped to the beach in front of the lighthouse. Beach nourishment has been applied to eroding shorelines north of the lighthouse in amounts of 312,000 cubic yards (240,000 cubic meters) in 1966, 200,000 cubic yards (153,000 cubic meters) in 1971, and 1.25 million cubic yards (960,000 cubic meters) in 1973 (MTMA Associates, 1980; U.S. Army Corps: of Engineers, 1985~. Cost MTMA Associates ~ 1980) estimated an initial cost of $2.9 million to pump 500,000 cubic yards (380,000 cubic meters) of sand to the beach in front of the lighthouse. Supposing a need for an additional 300,000 cubic yards (230,000 cubic meters) every other year and 300,000-500,000 cubic yards after every major storm, the long-term cost was estimated at more than $120 million (not discounted) over 100 Years. NPS ~ , , (1982) estimated an initial cost of $3 million and a 50-year cost of $60 million. To nourish the beach with 1,000,000 cubic yards, the committee estimated an initial cost of approximately $2 million and further estimated that the maintenance cost--initially about $700,000 per year--would increase with time. Even applying OMB's discount rate of 10% per year, a maintenance cost of $700,000 per year over the next 20 years is worth more than $5,000,000 in present value. Evaluation Beach nourishment, achieved by transporting sand from near Cape Hatteras or from Diamond Shoals, is one techni- cally feasible response to the erosion problem at the light- house. This approach -has the merit of requiring no visually obtrusive structures at the lighthouse except those related to pumping sand. Furthermore, the sand to be taken for place- ment at the lighthouse is not needed to maintain a developed the virtually permanent . - downdrift shoreline. ~i, ~. . . Nevertheless,

Evaluation of the Options 91 pipeline and pumping equipment necessary for the repeated nourishments would intrude upon the natural setting and interfere with beach use by visitors to the seashore. ~^ ~ ~ 11- sand were taken from the beach near Cape Hatteras, the huge borrow pits might interfere with beach access and reduce nesting sites for birds. However, the benefits of beach nourishment are short lived. Therefore, large quantities of new sand must be applied frequently to counteract erosion. The decisive criterion that this option fails is cost. The costs of beach nourishment are prohibitive, as described above, and, as the shoreline continues to retreat, the costs of maintaining an increasingly large artificial promontory at the lighthouse would grow disproportionately. Within 50 years, this option may become technically unfeasible as well as prohibitively costly. Furthermore, this option to control erosion at the lighthouse does not ensure against loss of the lighthouse during a major storm. ,, , . . No Action Although the committee was charged with evaluating options to preserve the lighthouse, it includes! no action as a management alternative, consistent with the National Envi- ronmental Policy Act. No action would lead to loss of the lighthouse within the next few decades, or possibly sooner, in the event of a direct hit by a severe hurricane or series of lesser storms. The option of doing nothing was eliminated from consid- eration because it would expose the lighthouse to a high risk of loss. The lighthouse probably would not be standing today without the present groin system. An additional risk is deterioration of the lighthouse foun- dation if no action is taken. The top of the existing timber mat is now approximately +2 feet (61 cm) MSL. When the lighthouse originally was constructed, the fresh groundwater level was above the top of these timbers, protecting them from dry rot. As the sea approaches, the groundwater level will continue to drop closer to MSL, exposing the timbers to dry rot and the lighthouse to serious settlement and possible collapse, if it remains in its present location (Lisle, 1985~.

92 Criteria, Options, and Evaluation Because no action probably will lead to loss of the light- house, this option is not satisfactory. New Lighthouse This option was not considered in the interim report. A new lighthouse would be built a suitable distance inland from the shoreline. A replica of the present lighthouse would be one possibility; another would be to hold a design competi- tion. Cost It is impossible to provide a cost estimate for this option, because the committee could not predict the designs that would be considered. Evaluation Building a new lighthouse would be consistent with the history of the first lighthouse at this site, which was destroyed when the present one was built (Holland, 1968~. When the original 1803 lighthouse at Cape Hatteras became endangered by the sea in the 1 860s, it was replaced by the current structure. The original tower was destroyed. When the present tower appeared to be endangered in 1936, it was abandoned temporarily, and a steel tower was erected farther inland. When shoreline erosion was reversed in the 1 940s, the steel tower was abandoned, and the 1870 lighthouse was reactivated. This option has several advantages. The beach would not be affected by any new structure, and natural processes would not be impeded. lowed. An example would be set for other problems In coastal-zone management elsewhere, teaching the value of adapting to ecological forces rather than trying to hold fast to difficult positions. However, NPS's purpose is to preserve Cape Hatteras Lighthouse as required by its mandate to preserve historic Historical precedent would be fol ~. ~. ~Ha -

Evaluation of the Options 93 structures. Construction of a new lighthouse, however imaginatively designed or built to resemble the original, would not serve the purpose of historic preservation. Recon- struction merely suggests the form and materials of the old structure. To replicate the lighthouse in all its detail, using original construction methods and materials, would be pro- hibitively expensive and might not be possible. For this rea- son, this option does not meet NPS's needs.

6 Practical Consiclerations The committee discussed a variety of practical matters related to moving the lighthouse. Some would apply to any option chosen by NPS, others are specific to the relocation option. CONTRACTING CONSIDERATIONS Because of the unusual nature of lighthouse relocation and the intricacies of federal procurement regulations, the com- mittee believes it prudent to comment on the potential NPS contracting process. NPS must comply with the Federal Acquisition Regulations System ( 1987), as well as its own agency-specific procurement regulations and policies. Within those constraints, two considerations are of great importance in this matter: . . The need to select a well-qualified contractor from the small number of firms technically capable of performing such a project successfully. The need to allow appropriate flexibility regarding spe- cific methods to be used by the contractor to accom- modate realities such as local availability and cost of materials, as well as geological, structural, and engi- neering factors that will be inherent to the methods employed. 95

96 Criteria, Options, and Evaluation A suitable way to select a contractor is a two-stage, negotiated procurement process such as that used by the U.S. Army Corps of Engineers on similarly complex projects involving potential risk, such as the Wolf Creek Dam cut-off wall in Kentucky. Offerors would submit qualifications (e.g., experience in similar projects, technical and engineering capabilities, and proposed supervisory staff). NPS would carefully screen the technical qualifications of potential con- tractors (with an independent advisory board if necessary) before specific technical and cost proposals for the actual work were solicited. Qualified offerors would provide a detailed technical pro- posal for carrying out the lighthouse relocation. This would include the following: Prepare detailed plans to strengthen the lighthouse to give it full structural integrity. Prepare detailed plans for the permanent foundation of the relocated lighthouse. Prepare detailed specifications for repairs to the gallery, lantern, stairs, windows, and masonry coatings. Prepare detailed plans for moving the lighthouse. Prepare detailed performance criteria for the move, including raising the structure, temporary dewatering and excavation, jacking procedure and controls, allow- able tilt, allowable accelerations and restrictions on jerk, control during the horizontal move, and final set down. With the advice of a board of consultants (and an inde- pendent engineering consultant with structural and geological expertise), NPS would review all submitted materials and select qualified contractors and request a financial proposal. NPS would be permitted to suggest minor modifications in any offeror's technical plans. Selected contractors would submit competitive cost proposals for the total project, which would include assumption of responsibility, and an appropriate insurance policy.

Practical Considerations 97 Allowing flexibility in methods to be used implies the need to develop and specify performance criteria for the light- house relocation--rather than detailed methodological require- ments--in the NPS request for proposals. The committee emphasizes that no set of detailed methocls, including the committee's own example of a relocation concept, should be specified at the outset. Rather, performance criteria, such as the desired lighthouse site location, structural and architec- tural rehabilitation and strengthening, measurable damage limitations, allowable displacement of structural components, and other criteria suggested above are preferable for this type of project. INSURANCE Builder's risk insurance is available to cover any physical damage to a structure that results from external events, such as tornadoes and hurricanes during the contract period. Insurance also is available to cover contractor's errors or omissions. Maximum coverage would be limited to replace- ment value of the structure. Professional liability insurance is available to protect the relocation contractor and the engineering consultant from errors in design or specifications, including omissions. Limits are specified, but usually have a maximum of $5,000,000. Project wrap-up insurance can be obtained on a case-by- case basis, which includes the professional liability of all parties involved in design. An insurance company usually will insist on an independent review. INTERIM MEASURES The committee was asked to comment on interim measures for protecting the lighthouse. Such measures should be taken as soon as possible to reduce the possibility of damage or destruction of the lighthouse before long-term protective measures can be completed. However, no interim measure would provide enough protection to justify postponement of a long-term solution.

98 Criteria, Options, and Evaluation The immediate danger to the lighthouse is the destructive erosion that might occur during a single storm or series of storms, rather than gradual, long-term retreat of the beach. A storm or storms might occur at any time of year, and would provide at most a few days' warning of their arrival. The most cost-effective interim measure--and one that could be implemented quickly--is beach nourishment in the bight immediately south of the southernmost groin. The ~ ~ ~ e ~ ~ ~ ^~^ ___ ~ _ (9 1 0 meters' ot neacn south of the southernmost groin. This would require a volume of sand 3 yards (2.7 meters) deep and 40 yards (37 meters) wide, totalling 120,000 cubic yards (92,000 cubic meters). The estimated cost of pumping this quantity of sand from the vicinity of Cape Point is $530,000. It should be recognized that this measure would be sacrifi- cial--the new sand would be lost in a major storm. But its purpose would be served if it buys enough time to implement a long-term protective option. committee suggests adding sand along Mu varos REHABILITATION OF THE LIGHTHOUSE . . ~. ,~. Constructed of mass brick masonry, the lighthouse is structurally sound. However, long vertical cracks are evident in the interior brick wall on the north and south sides of the lighthouse from the first landing level to the sixth land- ing level, extending intermittently for 150 feet (46 meters). These cracks pass through many points where stair stringers are anchored to the wall and through the sections that con- tain the window openings. Thermal effects probably caused these long cracks. When the outer cylindrical masonry wall of the lighthouse expands, high tensile stresses are induced in the inner cylindrical wall, because the two are tied together by a series of large, brick ribs. Cracks would be expected to occur in the interior wall along its weakest vertical sections. Movement of these cracks under thermal changes was confirmed by field instru- mentation measurements. Additional cracks also have been observed at various loca- tions where metal attachments are fastened to the interior wall. These cracks likely have developed as the result of corrosion of the anchorage for the attachments. _ . . . . . ~

Practical Considerations 99 Although these cracks do not adversely affect the struc- tural integrity of the lighthouse, the committee recommended that they be cleaned and sealed with a high quality, flexible joint sealant to prevent further deterioration and intrusion of moisture into the wall. These necessary rehabilitation efforts and other preservation measures have been thoroughly defined by an architect/engineer team (Hasbrouck Hunderman Architects et al., 1986) and should be implemented as soon as feasible, regardless of the option chosen for long-term pro- tection of the lighthouse. The committee hopes it will be possible to open the light- house to public access on completion of relocation or other long-term protective measures. SITE DESIGN Before the lighthouse is moved, the future location of the dwellings and other structures that form the lighthouse com- plex must be considered carefully. It would be best to place these structures at the new lighthouse site so that their physical relationship to the tower will continue as it has been in the original location. The present visitor parking and picnic areas impinge on the historical setting of the lighthouse. The committee suggests that additional parking and other visitor facilities should be separated from the lighthouse complex and screened by natural vegetation. Every effort should be made to recreate the sense of isolation of the original 1870 light- house setting.

Next: Appendix A »
Saving Cape Hatteras Lighthouse from the Sea: Options and Policy Implications Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!