Area Residents Are Already Dealing With Flooding Concerns |
The original plans of the Southwest Chicago Christian School were to sell the southwest corner of their property to Anthem Memory Care - the results of the site analysis conducted there resulted in relocating the proposed facility to the northwest corner
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Flooding Concerns
Disclaimer: The measurements and resulting calculations referenced below were derived using the measurement tools on the FEMA website and the measurements reflected on the preliminary drawings released to date. They are as close of approximations as one can make without having the actual site plans available. Furthermore, I am not an engineer, so I will not profess to know where the water that is winding up in residents' homes is coming from direction-wise other than from the sky, or in some messier instances, a combination of the sky and the sanitary sewers when things get really bad.
Part of the neighborhood in the area is actually located in a FEMA-designated floodplain, so some residents are already dealing with flooding issues on a regular basis. Those homes located in the blue-shaded areas of the maps are in the 100-year floodplain and are required by law to maintain flood insurance. The orange-shaded areas of the maps are in the 500-year floodplain, which are areas deemed to be at risk but that do not require flood insurance.
FEMA's National Flood Hazard Layer (Official)
Source: (http://fema.maps.arcgis.com/home/webmap/viewer.html?webmap=cbe088e7c8704464aa0fc34eb99e7f30)
Note: Use the controls on the image to zoom in & out to view the area.
Source: (http://fema.maps.arcgis.com/home/webmap/viewer.html?webmap=cbe088e7c8704464aa0fc34eb99e7f30)
Note: Use the controls on the image to zoom in & out to view the area.
The footprint of the bus depot currently occupying the site consists of a single building with a concrete/asphalt parking lot creating approximately 25,339 square feet or .58 acres of impervious surface area.
The exact surface area figures for the proposed facility have not been officially released yet, although preliminary drawings show the building footprint to be somewhere between 21,000-22,000 square feet with a 24-foot wide paved horseshoe-shaped drive looping around the building and 36 paved parking stalls that measure 9' x 18' each or 5,832 square feet combined.
Adding the low-end building footprint square footage of 21,000 to the parking stall total of 5,832 square feet equals 26,832 square feet. Adding the paved drive square footage will only increase the difference between the total for the existing bus depot and total for the proposed facility.
Note: The images below reflect a rough estimation of the entire footprint of the proposed facility using the tools available on the FEMA website and the measurements from the preliminary drawings. Not all of this area will be impervious surface and all run-off from this site will be directed to a retention pond described in the next section. Showing the entire lot simply helps provide a perspective on where things will be located in relation to the FEMA floodplain.
Adding the low-end building footprint square footage of 21,000 to the parking stall total of 5,832 square feet equals 26,832 square feet. Adding the paved drive square footage will only increase the difference between the total for the existing bus depot and total for the proposed facility.
Note: The images below reflect a rough estimation of the entire footprint of the proposed facility using the tools available on the FEMA website and the measurements from the preliminary drawings. Not all of this area will be impervious surface and all run-off from this site will be directed to a retention pond described in the next section. Showing the entire lot simply helps provide a perspective on where things will be located in relation to the FEMA floodplain.
Village code will require a 4-foot deep retention pond for this development. It is going to be located on the south end of the parcel. How close it will be to the 100-year floodplain remains to be seen as the preliminary drawings vary greatly and not all of them contain measurements to use for point of reference. Anyway, the area residents have been assured that the retention pond capacity will be sufficient enough to hold the rainwater run-off collected from proposed facility site before gradually releasing it into the storm sewers.
While the engineering and physics behind the design of such retention ponds is sound, their practical application has not been 100% effective when it comes to dealing with mother nature as evidenced by situations encountered in other areas of Oak Lawn that have attempted to utilize them. Without getting too technical there are flow restrictors in place that must be properly maintained. Additionally, it has been admitted that design limits of even properly-functioning retention ponds can be exceeded by what mother nature decides to do, i.e. the random "act of god" scenario.
How would you feel if you lived in this area and were told to simply "trust us"?
Those that dismiss this "no guarantee that it will work 100% of the time" argument should contact the village engineer or the Metropolitan Water Reclamation District of Greater Chicago (MWRD) for confirmation.
While the engineering and physics behind the design of such retention ponds is sound, their practical application has not been 100% effective when it comes to dealing with mother nature as evidenced by situations encountered in other areas of Oak Lawn that have attempted to utilize them. Without getting too technical there are flow restrictors in place that must be properly maintained. Additionally, it has been admitted that design limits of even properly-functioning retention ponds can be exceeded by what mother nature decides to do, i.e. the random "act of god" scenario.
How would you feel if you lived in this area and were told to simply "trust us"?
Those that dismiss this "no guarantee that it will work 100% of the time" argument should contact the village engineer or the Metropolitan Water Reclamation District of Greater Chicago (MWRD) for confirmation.