PART TWO: ENGINEERING INFORMATION

A.   Architectural Character:    

The present dam, while titled the Hofmann dam, is not the dam built by Hofmann.  Rather, it was built in 1950 by the State of Illinois: Department of Public Works and Buildings, Division of Waterways.  The architectural character of the current dam, in comparison to the intention of the 1950 construction, is intact seeing as no alterations have been made since construction. 

However, the 1950 dam is but the last of numerous stages for which this dam site is significant.  Historically, the pooled water level is the only consistency amongst these varying historically significant phases.  While consistently present and contributing to the designed historic landscape, this water level has served differing purposes throughout the life of this dam site.  Additionally, the horseshoe design of the dam, which deviated only slightly before 1950, was replaced by the straight dam which is currently present.  This design is not consistent with the varying horse-shoe designs of the previous historical dams.

In his 1868 Preliminary Report Upon the Proposed Suburban Village at Riverside, Near Chicago (Olmsted, Vaux & Co.) Frederick Law Olmsted, is quoted stating,

“It will probably be best to increase the height of the mill-dam so as to enlarge the area of the public water suitable for boating and skating, and so as to completely cover some low, flat ground now exposed in low stages of the river.  At the same time, a larger outlet should be provided to prevent floods above the dam from injuring the shore.  A public drive and walk should be carried near the edge of the bank in such a way as to avoid destroying the more valuable trees growing upon it, and there should be pretty boat-landings, terraces, balconies overhanging the water, and pavilions at points desirable for observing regattas, mainly of rustic character, and to be half overgrown with vines.” p. 28

This discussion regards the curvilinear designed, horse-shoe dam esteemed by the Fox Brothers with the first dam and Mr. George Hofmann with the second.  Such design exemplifies Frederick Law Olmsted’s landscape architectural theories, upon which the historic town of Riverside, was designed. This design is no longer present. 

B.              Condition of Fabric:

The visible components of the Dam are in excellent condition.  The Hofmann tower and those walls remaining on site, from the period of significance involving George Hofmann’s construction, are in good to poor condition as they have been deteriorating and have mainly been replaced. Of these structures, only the Hofmann tower has been restored.  The By-Pass constructed in 1928, while it has not been operated since the 1980s, remains operable and is in good condition.

C.   Description of superstructure:

“Stream:  Des Plaines River

Location: Above Barrypoint Road Bridge;

Mile 44.45

          Type:     Modified Ogee

          Material: Reinforced Concrete

          Condition:

Good

          Shape:    Straight

          Length:   258.5’

                        Comments: Dam Has Variable Cross Section Dimensions”  

Hofmann dam Des Plaines River Ecosystem Restoration Project; Cook County, IL: Figure 3.5

D.   Description of substructure:

E.   Description of piers:

F.   Description of abutments:                           

G.   Engineering approaches:

H.   Site

The integrity of the site is good in regard to the remaining pool of water at the base of the Hofmann tower.  This pool of water contributed to the development of historic Riverside and the era in which George Hofmann improved the site for recreational purposes. Additionally, it is this same pool that enabled the piles of polluting sludge to congregate behind the dam. 

In regard to the design of the dams preceding the present, the site is in poor condition as the historic design of the original dams is no longer.  The discussions by such significant individuals as Frederick Law Olmsted, and engineers involved in the ecological restoration of the Des Plaines River and the planning of the third dam built in 1950 have not completely been attained as they address the desire for the bountiful plant and river life of the Des Plaines River.

Additionally, the view of this historic site has been compromised by recent construction, currently underway along the south bank of the Des Plaines River.  Current construction is of a large condominium structure, of a scale similar to the Hofmann tower.  This structure occupies a space that was once mainly landscape.  The new structure hinders the view of the historical remains built during the significant period of George Hofmann’s ownership in 1908, specifically the boat docks and concrete walls along the south bank of the Des Plaines River.