← Back to the list of projects

City of Ann Arbor SSWWEP - Citizens Advisory Committee Coordination — City of Ann Arbor

← Back to messages

2.92 -C- What will be done (if anything) to remedy the "air gap" problem present in most of the EXISTING FDDs?

Posted by Lori Byron on 22 Dec, 2013
Category: Category 2 - about potential recommendations

Frank Burdick’s Log Number: 62, 63
Submitted by: Burdick log
Category (1,2,3): 2
Status: Closed
Estimated date to address: TBD, CAC to prioritize

Q. What will be done (if anything) to remedy the "air gap" problem present in most of the EXISTING FDDs?  The air gap allows the sump pump to discharge water right next to the home's foundation allowing it to eventually soak back down to the footing drains to be constantly just re-circulated. This excessive water is then allowed to permeate the un-compacted permeable freshly excavated soil caused by the tie-in of the discharge piping.  In addition the waterproofing on the exterior of the foundation is compromised by both the excavation and exposure during the tie-in steps. This compromised waterproofing allows the water to enter the foundation. What does the City intend to do remedy this issue on existing FDDs? 

Q. What design changes are being considered for potential new FDDs to remedy the air gap / discharge issue as described above. 


A. 

Comments

Lori Byron on 24 Jan, 2014:

[CITY]: 
The air gap is installed to allow for an emergency overflow, if the discharge line from the house to the storm sewer were to become blocked or if the storm sewer were to become blocked.   Water only exits from the air gap in the rare occurrence when it is prevented from flowing freely through the discharge line into the storm sewer and prevents the sump pump water from flowing back into the sump.  

The installation of the discharge pipe, at the air gap, requires a minimal area of excavation ranging in depth of 2-3 feet adjacent to the outside wall of the home. This excavation is backfilled and compacted by the contractors. In addition, if the contractor damages any waterproofing within this excavation, they are required to repair it. 

We are unaware of any locations where there is compromised waterproofing. If such instances exist, they should be brought to the City’s attention and will be investigated.