My View
By Donald C. Wotring, Ph.D., P.E. Geotechnical Civil Engineer
In regard to the SBPF efforts currently being discussed in your publication, I had a couple of comments.

Both biological and physical changes will occur at the borrow site. The U.S. Army Corps Manual, Design of Beach Fills, (EM 1110-2-3301) indicates that the following aspects should be considered when selecting a borrow site.

Biological

1. While certain fauna, such as fish, may not be affected by the borrow dredging operations because they can simply swim away, many other types of fauna and flora cannot relocate themselves and direct mortality will result.

2. A common physical alteration that results from dredging is the exposure of a substrate that differs from the naturally exposed substrate. Because many organisms are adapted to a specific substrate condition, organisms may not survive repopulation attempts from adjacent nondredged areas.

3. Dredging operations have negative impacts on organisms due to suspension of silt and clay size soil particles in the water.

Physical

Dredging operations will alter the natural substrate relief features. As a result, wave energy and refraction patterns will be altered, which may negatively impact nearby shorelines. While the SBPF has concluded that their numerical analyses indicate that there will be negligible impact to the wave patterns and energy dissipation, thus a negative impact on the nearby Nantucket shoreline, caution should be used while interpreting these conclusions. The results of numerical analyses are sensitive to the input data, and even with perfect input, the analyses reduce the complex ocean behavior with a mathematical equation. A mathematical equation cannot "model" such complex phenomena for all possible scenarios. Nor do we have the ability to predict the oceans response to future unknowns, such as weather, global warming, change in currents, etc. It is difficult to imagine that the dredging of enough material to "protect" a natural shoreline, will not have an equally negative impact on the borrow area. In fact, EM 1110-2-3301 states: "Dredging material from ebb tidal shoals is a likely source of wave modification because these shoals lie close to the shore and their crests are at relatively shallow depths." The fact is, the SBPF cannot realistically predict that dredging offshore of Nantucket will not negatively impact wave action on the shoreline.

The design of a beach fill (nourishment) for protection will require indefinite future maintenance. The SBPF proposal does not indicate how they intend to pay for this indefinite maintenance program. They indicate that they are willing to pay for this, but for how long? What will happen if one of the current owners, who is willing to pay, dies or sells their property? The future owner(s) may not be so willing to fund an indefinite shoreline maintenance program. Two likely scenarios are possible: 1) once the owner(s) decide that they are unwilling to pay, the shoreline will deteriorate to existing conditions, which will put the future home owners in the same situation; or 2) enough political pressure will be placed on government officials that it becomes a Massachusetts, or at least a Nantucket tax payer burden. I am quite certain that if you ask the average Massachusetts taxpayer if they would be willing to pay for shoreline protection of a few superwealthy home owners, they would be less than enthusiastic. The SBPF should clearly indicate how their proposal will be paid for in future generations.

Another indication of the SBPF's lack of forethought and planning is the absence of a planned long-term performance monitoring program. Again, the U.S. Army Corps Manual, Design of Beach Fills, (EM 1110-2-3301) defines the primary objectives of a long-term monitoring program:

• "Document and assess project performance to determine how well it fulfills the protection requirements for which it was designed;

• Identify maintenance and renourishment requirements;

• Evaluate project impacts; and • Assess the behavior of the borrow area.

Accomplishing these objectives should follow a three-phase approach, which includes a field data collection of required information, data analysis, and project assessment."

EM 1110-2-3301 further states that the minimum monitoring program should include the following four items:

1. Beach profile surveys;

2. Beach sediment sampling;

3. Wave and water level measurements; and

4. Shoreline aerial photography.

The manual provides guidelines for the frequency of recommended data collection.

In addition, EM 1110-2-3301 also recommends implementing a long-term monitoring program at the borrow area. "The purpose of monitoring the borrow site is to evaluate the borrow site suitability, continuing changes in morphology and sediment characteristics, and biology of the area after the borrow operation. The monitoring program should include bathymetric and subbottom surveying, sediment core and surface sampling, and biological data collection."

An operation and maintenance (OM) manual should also be developed to assist the current and future responsible parties. This Manual should include the following four main components:
1. Background;
2. Operation and Maintenance;
3. Periodic Nourishment; and
4. Responsibilities.

As part of the OM manual, the responsibilities section should clearly indicate the parties responsible for: monitoring, data analysis, renourishment, decision making and funding.

The proposed beach renourishment project is not a new idea and has been both successfully and unsuccessfully applied in the past. However, the stateof the-practice requires further planning on the part of the SBPF.

I wish the best for all concerned.

- Donald C. Wotring, Ph.D., P.E.

Geotechnical Civil Engineer