Note: Cyril Galvin will accept engineering (not political) comments from the public until November 4, 2002, to be incorporated in the final version to be released on November 18, 2002. Comments should be as concise as possible, and should be submitted via email to galvincoastal@juno.com

In the questions and answers below, the meaning of the term "The Point" will differ with the individual. My professional concern is with the rock perimeter of the Point. Others will be concerned with the paths within but near the perimeter, or with the meadow in the center of the Point. Still others will view the Point as a whole. Given that there is some looseness in what is meant by "The Point", the particular meaning is usually evident from the context.

1. What is the general condition of the Point?

To answer this question, you have to know how the questioner uses the Point. Let us divide the users into four classes: (1) residents of Hyde Park and Kenwood areas who rarely go to the Point and for whom the Point is a familiar backdrop to their spatial perception of this part of Chicago. (2) commuters and other travelers on Lake Front Drive passing in the vicinity of the Point between 54th and 57th Streets, (3) active visitors to the Point, and (4) government officials whose responsibilities include the Point.

How does the present condition of the rock perimeter affect these users? For class (1), the local residents who rarely visit the Point, the general condition is good. For class (2), the people who see the Point from inside a car, the general condition is good. For class (3), the general condition of the Point for people walking or running, people with bicycles, people who come to picnic or enjoy the view, is good. For those members of class (3) who swim, who actively interact with the shoreline, and especially for those with disabilities, the present condition of the shore has difficulties presented by irregular displacements of the limestone block, by lack of access, and by nearshore variations in depth. Finally, for members of class (4), the government figures who must be concerned with the future, the perimeter of the Point, as it now exists, has reached the closing years of useful life and needs renovation for the Point to have optimum future use.

For all four classes, the integrity and distinctiveness of the Point is determined by its rock perimeter, which is slowly deteriorating. For the City as a whole, the integrity of the Point adds value to life in the south of Chicago. This value determines real estate prices, and thus tax resources for the City.

2. What is going to happen to the Point if nothing is done?

Nothing drastic will happen in the short run, say, in the next decade. The severity of outcome will depend on future lake level and on future ice cover. High lake levels and low ice cover on Lake Michigan are bad for the rock perimeter of the Point, and ultimately for the Point as a whole. Given a "worst-case" future, if water levels in Lake Michigan were to rise to record levels, and if there were two relatively ice-free winters while this high water condition continues, the movement of the limestone blocks would increase noticeably, there is a good chance that the concrete platform surrounding the northeast corner of the Point would deteriorate rapidly, and overtopping would erode grass on the immediate landside of the limestone revetment. These outcomes could be mitigated by prompt action. Given a "typical", plain-vanilla future, if Lake levels remain average and ice cover is at least moderate in winter, conditions at the rock perimeter will gradually deteriorate, some block movement will occur, and there will be local failure in the concrete platform. Given a "best-case" future, if Lake levels drop lower, and if winter ice cover is moderate or heavy, only minor changes would occur over the next decade.

Because of its past history, the rock perimeter at the Point is now in condition where it is better able to resist future storms during average or below-average Lake levels than when the Point first was built.

3. What can be done temporarily to stabilize the Point until another plan is developed?

I strongly recommend against any "temporary" action. Such temporary action is not needed, and it would divert resources and community attention from doing the necessary work. However, it is possible that some lower-cost (not low-cost) actions such as landscaping (french drains) on the upland part of the Point or the addition of sand to the shore on the north side of the Point might provide benefits that would fit well with work for long-term solutions.

4. What is the life expectancy of the temporary measures?

See the answer to Question 3 above.

5. Is the rock at the Point limestone?

The step-stone rock revetment is limestone. In some places, repairs may have been made with dolomite. Some limestone contains small percentages of the mineral dolomite. But it is clear that the architectural character of the rock perimeter at the Point is derived from limestone quarried almost exclusively in the general vicinity of Bloomington, Indiana.

("Limestone", the rock, consists almost entirely of the mineral calcite. "Dolomite", the rock, consists mostly of dolomite, the mineral.)

6. How available is limestone?

New limestone is reasonably available at Indiana quarries, for a price: $25 to $29/ton, loaded on truck at quarry, plus truck transport to Chicago. However, the majority of limestone needed is already on the Point in the existing step-stone revetment.

7. Is limestone durable?

Yes, if it is the quality of limestone from the Indiana area. Almost all Federal Buildings in the Washington DC metropolitan area are clad in this Indiana limestone. This use began in the late 19th century and continues today with good durable results. Indiana limestone quarries provided stone for the rebuilding (now complete) of the Pentagon sector damaged in the 9-11 plane impact.

8. What are the advantages and disadvantages of constructing a revetment with limestone vs concrete? The answer below concerns new (rather than re-used) limestone.

Advantages of limestone: Proven record of use, natural appearance, fit with existing structure, simplicity of manufacture, placement that can be modified without major unwanted consequences. Good re-used limestone blocks have the advantage of being on site.

Advantages of concrete: Near-universal availability, familiarity of work force with technology, ability to be formed in different shapes and sizes.

Disadvantages of limestone: For new stone, the necessity for long-distance transport; necessity for quality control to eliminate stone with disabling partings or low density; at least in the beginning, relative unfamiliarity of work force with large scale masonry; mix of available sizes. All but one limestone quarry closes during the winter.

Disadvantages of concrete: Necessity to build an exposed structure having many contacts between steel and concrete; sterile, unnatural appearance, uniformity of design and surface. Monolithic form that cannot be modified. Less long-term experience with the specific design of the Corps.

Note: Each material has lobbyists that will bring out the best points of their material, while implying that the other material is inferior. In addition, proponents of some materials are often better connected with local politicians and fit better with the local work force. Thus, it is necessary to carefully examine any claim about materials.

9. What is relative cost of limestone vs concrete.

Cost depends on the unit of measure used. It is typical to sell stone by the ton, concrete by the cubic yard and steel sheet by the pound (converted to length). To provide a common basis, these material costs must be combined with labor costs, and computed on the basis of annualized total cost per foot of lake shoreline. Annualized costs include costs of maintenance and expected useful life.

Typical structural concrete is about $85 per cubic yard delivered; cast-in-place with forms, about $250/cubic yard. Heavy concrete weight about two tons per cubic yard, or for simple cast-in-place concrete, about $125/ton. Stone loaded on truck at the quarry about $27 per ton, about 20 tons per load. At $2.00 per loaded mile and 230 miles from the quarry, this comes to about $53 per ton of new limestone block, delivered on a flat bed truck at the Point.

10. Is $20 million enough to rebuild the existing structure? (Posed differently, what would $20 million get us in rebuilding the Point?)

$20 million will get you a complete renovation.

11. How do the maintenance costs of limestone revetment compare to the maintenance costs of a concrete revetment?

There is a major difference between maintenance costs of the limestone revetment and a concrete-steel structure. The limestone revetment is more forgiving of partial damage than structures made of sheet pile. Displacement of limestone blocks by waves usually puts the displaced blocks where they continue to provide shore protection, and most of the displaced blocks are reusable. Displacement of even one sheet pile can lead to unraveling of the entire structure, and almost nothing is reusable. The new sheet pile and concrete structure just north of the Point is well constructed when viewed as a finished product. It should not require repairs for a decade or so, if constructed as designed. However, it does not serve functionally as a user-friendly, lake-front environment for the Point.

12. What grade of concrete is specified in this type of construction? Is this grade being used?

I do not now know the answer to either question. But the owner of a new concrete structure almost always requires that tests be made to verify that the concrete is up to specifications. This information should be available from the City or from the Corps of Engineers. Failure to conform to specs is a serious breach of contract.

The structures along the shore north of the Point which I have visited look good, look well--constructed, when viewed as finished products shortly after construction.

13. Are there large cavities under the Point? Is Promontory Point going to fall into the water?

Cavities are limited to the rock perimeter of the Point and do not extend landward of the rock perimeter. Available observations by Matt Frank and my personal observation verify that cavities in the shape of thin horizontal wedges extend back as much as ten feet. Wave-driven water freely percolates back another ten feet to the landward edge of the rock perimeter in numerous places under the concrete platform with coffins.

The answer to the second question is an unqualified NO.

14. Is the settling of the stone structure related to wave action or to compaction?

Initially, I had been of the opinion that compaction was an important factor in causing tilting and movement of the stone. However, my observations made with Matt Frank and Connie Spreen on 23 September 2002 conclusively indicate that erosion by wave-driven water under the concrete platform is the main cause.

15. Is the Point going to wash away? Is it eroding? What erosion rate should be expected? Is this the erosion rate that the City/Army Corps is employing?

It is possible to answer these four questions with a high degree of certainty, based on facts in the field and in published documents.

(a) Wash away? NO WAY.

(b) Eroding? Yes.

(c) The Point as it exists now is eroding slowly. In terms of shoreline retreat, it is eroding almost not at all. In terms of volume removed from the shore front, small quantities are being lost each year. It is likely that small volumes of upland soil on the Point are also being lost annually from soil erosion in storms.

(d) The erosion rates predicted by the Corps of Engineers in their House Document 103-302 dated 1994 have not occurred. Those (1994) erosion rates from the Corps of Engineers for the entire project have no credibility, and that fact was known in 1994.

16. Is it possible to build a limestone revetment that will last?

Yes.

17. Why did the existing structure fail? Is it the result of poor design, poor maintenance, or some other factor?

Most engineers who had studied the history of Promontory Point would not agree that the structure failed. For an acceptable design, the engineer considers how to withstand reasonable risks imposed by the environment (structural design) while performing a task that society wishes done (functional design), all at costs that society is willing and able to pay.

Citizens of early 20th-century Chicago wished to create parkland along the south shore of Chicago. An expedient way to do that was to fill Lake Michigan bottom to create new land. To do this, a structure was needed to retain the often-soupy fill within a perimeter, and to prevent wave and water level combinations from eroding the fill before it dried out. The original structure that performed these functions in early 1920s is still there, still functioning today. Those early engineers and contractors succeeded in both objectives rather well. Promontory Point has existed for nearly 80 years on an area that was formerly the bottom of Lake Michigan. If no other work is done, Promontory Point (the Point as a whole) will still be there, with storm-induced modification to its rock perimeter, for decades into the future.

So objectives of the original structural and functional design of Promontory Point have been achieved. The structure has not failed. But it is in need of repair.

Added to those original objectives was the aesthetic objectives of a landscape architect. The style of the step-stone revetment, the meadow, and the council rings at the Point is the style used by Alfred Caldwell, but we have not found direct evidence to link Caldwell to the rock perimeter. The stepped-stone revetment around the perimeter rested on and was slightly landward of the original perimeter structure that contained the fill. The step-stone revetment finished in 1937-1938 served as protection against waves and overtopping water and as an aesthetically pleasing perimeter. It does this today to a remarkable degree after 65 years. In particular, aerial views of the Point in 2002 strike me as aesthetically very pleasing, and (on balance) show the revetment still to be intact.

Locally, waves have damaged the shore near the northeast corner of the Point and repairs have been made in the form of the concrete platform around the most exposed segment of the perimeter. The concrete platform now needs further repair. The segment of the perimeter stepped-stone revetment on the south shore of the Point is in remarkably good shape for a 65-year old structure along the Lake Michigan shore.

There is no evidence of poor design. The northeast segment of the rock perimeter would have been built stronger if designed new today. Continuous maintenance would have better preserved the original alignment of the stepped-stone revetment, but probably that maintenance would have been costly in terms of real benefits, and only delayed the present condition by a decade or so.

18. The City has designed the new concrete revetment to withstand a 200-year wave. Do we need to plan for a 200-year wave? Is this a reasonable way to plan a revetment? What is the worst we can expect from Lake Michigan?

I have not documented this question to find where the City has designed for a 200-year wave, as the average citizen would understand that phrase. The most damaging wave to hit the stepped-stone revetment will be the wave just breaking a short distance offshore. Whether the design wave in the middle of Lake Michigan is the 200-year wave or the 50-year wave is not likely to make much difference to a structure on the shore of Lake Michigan because bigger waves will break offshore, and thus will be relatively harmless by the time they reach the revetment. Thus, if the City has actually designed for a 200-year wave at the Point, then at worst they have wasted a little time and a little money in the design phase, but it should all come out in the wash if proper procedures were used.

The most damaging wave would be on the order of 10 feet high, a vertical distance from highest crest to lowest trough. Larger waves would break harmlessly offshore, smaller waves would do less harm. Most of the limestone revetment could withstand limited durations of direct hits from such ten-foot waves.

19. Is there danger of flooding of Lake Shore Drive from water overtopping the Point?

No.

20. Can disabled access be integrated into limestone preservation?

Yes.

21. How can swimming access be integrated into limestone preservation?

There is no intrinsic obstacle to providing swimming access from the limestone revetment. However, it seems to me, as an outsider having long-term experience with recreational use of the shoreline, that two things need to be done before designing specific access:

• First, there should be a poll of swimmers to see what they like and what they do not like about the present situation. There are at least three classes of swimmers to consider: the non-swimming swimmers who enjoy walking in the water (those perhaps include many seniors and young children); the beach bathers (teenagers, families); and serious deepwater swimmers (primarily adults of all ages).

• Second, some permanent accommodation needs to be made with the City government on the right to swim from the Point. It is understood that the City prevents swimming from the east end of the Point (the deepest end) for good reasons. By allowing swimming from elsewhere on the Point, the City may add a potential liability that all citizens in Chicago would have to bear. Yet, deepwater swimming is a unique feature of the Point that adds variety and interest and should be accommodated.

22. Can the revetment be structurally supported without the use of steel sheet pile?

Yes, it will be possible to get by without visible steel sheet pile in all but a few places. There may be some local areas where steel sheet pile is necessary.

Cyril Galvin, Coastal Engineer
22 Sep 02
(Revised 30 Sep 02) The Cover Photo clearly identifies where we are. It is classy, it is even classical, and it is slightly in need of repair.