Back to Emergence of Community Plan
As forwarded to Hyde Park-Kenwood Community Conference. Abridged by Gary Ossewaarde. The Conference also has Galvin's main report (including proposed engineering strategy) dated October 1, 2002. This is a part of the Final Report.
www.savethepoint.org has a complete version (part in pdf) of materials linked from its home page. These include October 1 Report, November 20 Conference Call, and December 7 Final Report.
Hyde Park Herald report on Final Report and coming access report
Letter to friends from the Task Force Executive Committee, December 12, 2002
Hyde Park Historical Society, Community Task Force for Promontory Point
Dear Homer [Ashby],
The Task Force for Promontory Point would like to thank you for your continuing interest in our community's efforts to preserve the history, beauty and recreational value of Promontory Point.
As you know, we retained a coastal engineer, Cyril Galvin, to conduct an independent engineering study of the existing limestone revetment. His final report is enclosed. We think it conclusively proves that the limestone at Promontory Point can be preserved--safely and affordably.
We have also retained a team of preservation architects, Frank Heitzman, AIA, and Wayne Tjaden, AIA, to develop a preservation plan for Promontory Point based on Mr. Galvin's findings. Their plan will provide extensive access for persons with disabilities, as well as swimming access for all. In addition we have retained John McGovern, who chaired the United States Architectural and Transportation Barriers Compliance Board (the "Access Board") Committee for Recreational Facilities and also served on their Outdoor Developed Areas Committee. Mr. McGovern will work with our architects to craft an appropriate plan for a universally accessible Point. He feels strongly that accessibility can be achieved while preserving the limestone revetment.
Finally, with the ongoing leadership and support of 5th Ward Alderman Leslie Hairston, we have formally asked the Chicago Landmarks Commission to declare Promontory Point a Chicago historic landmark.
Thanks again for your continuing interest in or community's efforts to preserve Promontory Point.
Fred Blum, Bruce Johnstone, Jack Spicer, Connie Spreen--Executive Committee, Community Task Force for Promontory Point
This is the Final Report of a study showing that it is feasible and relatively inexpensive to repair and preserve the historic and aesthetically pleasing step-stone revetment of limestone blocks that has protected the perimeter of Promontory Point at 55th Street in Chicago on the shore of Lake Michigan since 1937-38. This Final Report makes extended reference to a Supplement to the Final Report, which must be considered an integral part of this Final Report. This Supplement (26 Nov 02) consists of three documents bound as one: the Report (1 Octj02), the Responses by the government agencies and their engineers to the Report (4 Nov 02), and a Conference Call Record (25 Nov 02) discussing both the Report and the Responses.
The Report (1 Oct 02) concluded that at least three quarters of the existing limestone on the revetment was reusable, despite continuing publicity by the government agencies that the limestone would disintegrate and could not be reused. Since the 1 Oct 02 Report, data from a study (April, 2001) commissioned by the government's engineers has come to light proving that more than 90% of the stone is reusable.
The Report (1 Oct 02) concluded, in the face of misinformation on limestone availability, that there are abundant supplies of new limestone blocks for use as revetment on the Point and that these blocks are available at prices that are reasonable in comparison to costs of other materials. This Final Report includes five letters attesting to this limestone block availability, four of which are from quarry owners responding to provisional specifications on the blocks. The provisional specifications are conservative, and they were generated from data in the April 2001 report commissioned by the government's engineers, which data are consistent with my field experience gained in producing this Final Report.
Statements about Promontory Point made by government officials and their engineers are demonstrably wrong a surprising amount of the time, when appeal is made to the written record and measurable facts in the field. The frequency and importance of the misstatements suggest that the burden of proof should rest with the government agencies and their engineers. In particular, they should be required to demonstrate their qualifications to pronounce on a given subject, and their pronouncements must refer to facts that are published in accepted sources or are measurable at a site. The government's engineers demonstrate a surprising lack of knowledge about the Point, an area where they recommend construction of a $22 million structure which moves the perimeter of the Point into depths that will be subject to higher, more destructive waves.
Personal information from three individuals with disabilities suggest that the existing concrete platform around the east end of the Point would be an attractive and feasible destination if access were provided. Visitors with disabilities prefer round trips without retracing the initial path. Interesting round trips should be possible with the completion of the second underpass at Lake Shore Drive. The concrete platform should be accessed by two 1-on-12 ramps, one on either end of the platform, each with a switchback. These ramps will also serve as access for pedestrian visitors and deep water swimmers. Blind visitors will benefit from relatively simple improvements. Swimming will be restricted to the north and south shores of the Point. The creation of attractive wading and swimming beaches away from the east end will become increasingly feasible. Deep water swimming sites closer to the east ends of the north and south shores are possible.
Historical data made available by the Project Coordinator and the governments's engineers show that the shores north and south of the Point have experienced a remarkable deposition of sediment, probably sand, since initial construction in the 1920s. This sediment has decreased water depths around the perimeter from an orginial 17 or 18 feet to near zero in many places. These depths also demonstrate the boldness and skill of the engineers and contractors who constructed the Point on the bottom of Lake Michigan in the 1920s and 1930's, adding to the historical value of the Point with its step-stone revetment of limestone blocks.
There is no defendable objection to the course of action recommended in the 1 Oct 02 Report. That recommendation should be implemented as soon as possible with the exploratory engineering investigation and detailed design described herein.
Editor's note. Only select portions of this lengthy report can be reproduced here.
Executive Summary p. 2
Context pp. 5-9: Final Report including Supplement, Corrections, Acknowledgements, Accepted Principles
Access for Disabled and for Swimmers pp. 5-15
The Concrete and Steel Plan pp 16-22: Functional Definitions, Responses of Government Engineers, Regulatory Threats, Maintenance History
Limestone Myths pp. 23-34: Block Not Reusable, Block Not Available, Specifications, What Do You Think?
Water Depth at Perimeter of the Point pp. 35-41: Year 2002, Historic Depth Changes
An Endowment for the Point p.42
Renovation of the Revetment pp. 43-45: Limestone, Stability, Piles, Bedding Stone at Promenade, Sheet Pile Partition, Grouting, Storage of Limestone
Corps of Engineers Erosion Predictions p. 46
Summary pp. 47-53: Believability, Mrs. Sobek...Questions, Aesthetics of the Concrete Platform, Overall Evaluation, Recommendations
From ACCESS FOR THE DISABLED AND FOR SWIMMERS (pp. 10-15)
The two subsections below discuss access for persons with disabilities and access for swimmers. Both classes of access should be considered together: there should be an integrated access plan, and, as far as possible, this plan should be driven by what people in the two groups (the disabled and the swimmers) actually want. The access plan should consider the possibility that one person could be a member of both groups.
However, it is likely that the concrete platform on the east tip of the Point will be the dominant attraction for most people in wheel chairs, whereas swimmers will more likely use the northerly and southerly shores, particularly the northwest segment and the east segment of the south shore of the Point. [See figure, a bit below.]
...My contract... deliberately anticipates that someone else would be hired to handle questions of ADA access. This would be in sequence.... [M]y 1 October Report deals only in generalities on the subject of access....However, my contract does require "two feasible concepts for disabled access" that answers the question "How can the limestone blocks be integrated in a structure which provides access for the disabled." This section addresses the contract requirement based primarily on information from three people who live with disabilities..
I recommend the following: highlight the concrete platform as a destination for those in wheelchairs; consider the roundtrip experience for such persons in any design; explore the possibility of balloon-tired wheelchairs to use on the promenade; look into single curbs along paths to assist blind pedestrians; and investigate boardwalks on the promenade with caution... The possibility of a path or a viewing site near the rock perimeter of the park upland might be considered... A pair of ramps down to the concrete platform at its north and south ends will provide access for people with disabilities, for deep water swimmers, an for pedestrian visitors. The ramps with 1-on-12 slopes would be about 120 feet, measured along the ramp, but only 65 feet in longshore distance from one switchback halfway in each ramp.
Swimming Access. Field evidence to be discussed later indicates that it will become increasingly feasible during the coming years to maintain a sand beach on the north shore of the Point, probably northwest of the Field House, that is, in toward the Lake Shore Drive.
The people conducting the swimming study first need to identify the parameters that the city will set for swimming. As indicated in the Report, there are at least three classes of swimmers: waders, beach bathers, and deep water swimmers. For the most part, these are distinct groups that will benefit from different improvements. It is strongly recommended that individuals in each group be identified, preferably while they are at the Point, and interviewed about their ideas on optimal swimming arrangements. Only then will it be possible to develop a plan to optimize the benefit to each of the groups.
From THE CONCRETE AND STEEL PLAN starting p. 18
Responses of the Government's Design Engineers. STS devotes 16 pages of the Responses (pages 10 to 35) to saying that the Community's preservation plan in the Report will not work. Those arguments are examined in detail within the Conference Call record (see Supplement). The arguments fall into three classes:
Evidence that the STS engineers are unfamiliar with the site includes (see Conference Call record in the Supplement):
Possibly because they do not know the existing field conditions or have not read the Report, they say we propose the following:
Under the bluff and bluster category, one may include:
Regulatory Threats. The STS Responses are unusually concerned with process, particularly with permits and standards. I have been in the consulting business a long time and know the power of regulatory agencies to delay work using the permitting process. The authors of the STS Responses bring up this possibility repeatedly.
Nowhere do the STS reviewers provide a single calculation to show that the design proposed in the Report fails to meet adequate standards.
LIMESTONE MYTHS starting p. 23
Myth: Limestone Block Not Reusable. [Galvin gives] five numbered quotations dealing with limestone reuse for construction at the point. ...1 and 2 are by the government's design team. 3, 4, 5, by a consultant to the City. [Cites a 2001 government investigation by Associated Geologists that refuted largely anecdotal claims of extensive block failures in the Solidarity Drive revetment reconstruction, quoted repeatedly against limestone, and points to other problems at that site. Those studies said at least 90% of the blocks did not appear structurally weakened after 70 years of freeze-thaw cycles and wave action--Concrete does not approach such durability, Galvin added.]
Myth: Limestone Block Unavailable. [Says this is false and produces five letters responding to inquiry with specifications; shows other visual documentary evidence.]
WATER DEPTHS AT PERIMETER OF POINT pp. 35-42
[Describes direct measurements June and November, 2002 showing the depth is shallow and there is no stability problem, making for ease of work. The slope is steeper off the concrete platform, but large rocks provide protection there. p. 40:] Looked at functionally, the Point is a very large groin sticking out into Lake Michigan. ...By analogy with conditions elsewhere, we expect the north side to shoal and the south side to erode. Actually, the record shows that both sides have accreted, and the south side has accreted nearly twice as fast as the north side.... [In fact,] the shore just northwest of the [northwest] council ring...would be a good place to put a bathing beach...Even more practically, these shoaling data show that the tie rods that were essential in holding the crib together when it stood in 17 feet of water are now serving no structural function. This is a good thing, because almost all of them have been broken for a while.
AN ENDOWMENT FOR PROMONTORY POINT pp. 42>
The money saved over the government plan could endow the Point's upkeep in perpetuity, with funds left over for the Park District.
The Responses to the original Report put us in a difficult position as far as specifying the work. We were "damned if we did, or damned if we did not" describe exactly how to accomplish the work suggested in the Report. If we did describe, this was thought to be specifying the contractor's methods; if we did not, this was thought to be evidence that the work was impractical or not constructible.
With this in mind, the following headings describe the various aspects of the project. I believe that construction engineers and medium-sized contractors, who need not be marine contractors, can come up with ways to improve on many of the suggestions below.
Limestone. Information gained since completion of the Report (1 Oct 02) has confirmed conclusions available then that limestone blocks in the existing revetment are reusable. At least 75%, and possibly 90%, of the existing blocks are reusable. Information gained since then demonstrates sufficient limestone blocks are available, and that they are likely to be available in a competitive market.
Thus, there is no doubt about limestone block integrity or competitive availability. We produced a provisional specification. Almost certainly, those specs can be loosened after further study.
Stability. Shoaling along the perimeter of the Point eliminated the structural function of the cribs that were essential in the early years of crib existence. The wood pile walls of those cribs now function as permeable partitions and not containers of rock dikes. Slopes surrounding the Point are made of clastic sediment, the larger sizes (rocks, boulders) on the steeper slopes, and those slopes are generally mild.
This shoaled condition does not eliminate the need for exploratory engineering studies and for the utmost attention to safety that any construction deserves. But it does suggest that there is no inherent barrier to undertaking the work because of slope stability.
Piles. The pile remnants around the perimeter serve one essential function: they retain the promenade limestone blocks during storms. They need only resist horizontal jostling from the outer row of promenade limestone blocks during storms. They also serve to retain the coarse bedding stone under these blocks. To fix the piles with ties and deadmen would not be a good use of time and money. The piles should get wales, duplicating the existing wales, or perhaps, as the engineer may decide, a double wale.
However, replacing the piles will not be easy. A study of the historic plans suggests that my original idea of jetting out the piles was probably not the best way to go. The needed new piles are not long, compared with piles used in most coastal construction. It is probable that the soil is rocky on both sides of the existing shoreline row of piles. The best plan will be developed after exploratory pits, boring or auguring to depths of 10 feet below surface of the bottom near the existing piles.
The existing piles might be used as guides for the new piles, and then the existing piles cut at grade.
Bedding Stone at Promenade. It is clear that the piles originally formed a wall. It is doubtful if there ever was any sheeting used with them. The gaps between the piles were those due to natural irregularities and taper. The new piles likewise should be touching with installed. It is recommended that somewhat coarser bedding stone be used under the outermost block of the promenade to reduce future loss of bedding stone.
Sheet Pile Partition. The historical plans lend encouragement to this part of the construction. Available information suggests that the fill just landward of the orginial crib may eliminate the need for trenching and back filling with sand as originally recommended. Again, exploratory boring or augers should provide information.
Grouting. No task attracted more attention than this. An expert should be consulted, but here is what my idea is:
[Map the holes under the concrete, develop a plywood form for the front face, grout the first bedding stone at the lakefront, grout the cavern, use no retainer on lake side.]
Storage of Limestone. [on adjacent land, as in 1964 platform construction]
[Criticism of these not addressed in government response.] The following facts cannot be disputed or evaded:
Believability. [Says the public has been mislead by public statements and actions of the government. Example: people were grateful in the mid 90's when the Corps agreed to go with step-stone--not suspecting the Corps would come up with steel concrete. The design reports have been full of misstatements--see the Truth Table.]
Aesthetics. [There is an aesthetic to the 1964 concrete platform with its "coffins" at the east end (and coffins on north side), and they serve an essential role in dissipating erosive forces. Galvin recommends they remain, along with the limestone step stones.]
Those not reproduced here: October 1 Report, Conference Call, experience vita for Galvin.
The summary document called 22 Questions, distributed at the October 1 meeting that introduced the preliminary Galvin Report. From the Save the Point website, edited by Roger Deschner for the Task Force.
ALWAYS WANTED TO KNOW ABOUT THE POINT
TWENTY-TWO QUESTIONS, WITH ANSWERS
Questions prepared by the Community Task Force on Promontory Point
prepared for the Hyde Park Historical Society under the direction of the Executive Committee of the Community Task Force for Promontory Point
Cyril Galvin, Coastal Engineer
Box 623, Springfield Virginia 22150, USA
30 September 2002
WHAT YOU ALWAYS WANTED TO KNOW ABOUT THE POINT
TWENTY-TWO QUESTIONS, WITH ANSWERS
Questions Prepared Independently by the Community Task Force on Promontory Point
Answers are by Cyril Galvin, Coastal Engineer
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?
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?
20. Can disabled access be integrated into limestone preservation?
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.
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.
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