Scientific Application Of Street Rainfall Retention Can Reduce Costs Of

Required Drainage Improvements In Flat Areas
By GEORGE O. CONSOER
Consoer, Townsend & Associates
Consulting Engineers

THERE are quite a few sewer districts in the Chicago area on which street retention of excess rainfall is being successfully practiced. In these areas the trunk sewers are sized to carry off immediately a total rainfall of one inch per hour or less. When the rate of precipitation exceeds the carrying capacity of the sewers the excess water accumulates on streets for short periods. Restricting the area of pavement inlets and of inlet connecting pipe has been practiced and has proved to be a successful method of holding excess water on the surface and minimizing flooding of residential basements. Basically, this type of installation will be workable for all flat areas.

In one such installation of relief sewers at Maywood, Illinois, inlet areas were kept small and usually more than one inlet was connected to each catchbasin, using small eight inch pipe. The catch-basins were connected to manholes, also utilizing eight inch pipe. Ponding of water around inlets occurs during heavy rains but basement flooding even in the most severe storms is quite a rare occurrence.

The sizes required for the main drainage channels in the Chicago area, such as the Chicago, Calumet, and Des Plaines Rivers, are, of course, materially affected by the rate of discharge from the tributary storm sewers. Wider practice of planned retention as a means of lessening satisfactory sizes of trunk sewers would be reflected in decrease of channel capacities required for these main river outlets as well as reducing the size and cost of trunk sewers.

It is not intended in this article to claim that the use of retention and flow retardation is the best solution to a given drainage problem. Rather, the use of these methods may be the only reasonably attainable solution, considering capacity of available outlets and costs of enlargement versus available sources of financing. When weighing the costs of this type of solution, which would result in only a moderate amount of damage and inconvenience, as compared with the cost of a perfect solution, other needs of a community should also be considered. In the opinion of the writer, the critical need for expansion of educational, recreational, cultural, transportation and other facilities usually demand that the most economical method of achieving a satisfactory drainage system be followed.

Police sirens are banned in Winnipeg, Canada, because "they give the driver a false sense of security. Without a siren one must travel with due regard to traffic and the lives of others."

Great Bend, Kansas, has been named the Grand Award winner for conducting the most outstanding city Community Vehicle Safety Check Program in the nation. Other awards for excellence of programs by population groups went to: Oelwein, Iowa, Painesville, Ohio, Greenville, South Carolina, Gary, Indiana, and Seattle, Washington.

November 1958 / Illinois Municipal Review / Page 263