Inflow and infiltration?

Yes, sorry for the vague abbreviation.

Joe

I had to google it but it made an answer for me.

Do we have any info about public sources of I&I?

Any possibility to update this at tomorrow's meeting?

A: A number of changes to the collection system have been made through the years to address the observed basement backup problems, including the following:

a.         Smoke Testing Georgetown Area - 1998

This study detailed the results of smoke testing performed in the Bromley and Orchard Hills study areas.  The work was performed to document potential sources of rainwater inflow and infiltration that may have been the cause of basement backups in August, 1998.  It also included a list, by address, of the number of downspouts potentially connected to the sanitary collection system.  This report contained an inspection log of manholes in the two study areas.  The inspection included cover type, manhole type and condition, wall type and condition, observed infiltration, and potential infiltration.  Individual field inspection forms for each manhole are available.

 

b.         Lansdowne Investigations - 1987

Three related reports prepared by Soil and Materials Engineers, Inc., McNamee Porter & Seeley, and Harza, document contributing factors to basement backups in the Morehead area.  These reports provide boring logs that document area geology, groundwater elevation data, and a recommendation for three relief sewer projects.  These reports include information on the impacts of the August 22, 1987 storm event, a summary table listing the impacted residences, and a discussion of flow monitoring performed in the area.

c.         Northeast Ann Arbor - Ann Arbor Internal Memoranda - 1982

This document provides a detailed review of the Bromley and Orchard Hills study areas and documents the basement backups that took place during a June 28, 1982 storm event.  There is information regarding roof drain downspouts connected to the sanitary system and reference is made to a basement elevation survey conducted in 1970 for some homes in the study areas.  There is also a reference, including some technical information, concerning the retention basin constructed in the Orchard Hills area in 1970.  While there is mention of a flow meter installed in the Bromley area, data from that meter was not included in the document.

A program was conducted in the 1980’s to disconnect roof drains from the sanitary sewer system.  At this time, it is believed that most of the roof drains in the City have now been disconnected from the sanitary system. If areas where roof drain connections are suspected are located in the future, further investigation will be performed.

Other sources of I&I may include leakage through manholes and manhole covers, aging sewer pipes, and leaking sanitary sewer leads from private properties. Although a comprehensive program does not currently exist, leakage through manhole covers in flood prone areas are addressed with temporary plugs in manhole pickholes as they are discovered. Also, the City has a biannual sewer lining program to repair aging sewer pipes.

"as they are discovered".  Is there a systematic check system in place?

[City]

A. Not at this time, however the City plans to use the stormwater model (when project is completed) as a tool for developing a formal program.  In addition, developing a formal program is a likely recommendation that will come out of the CAC.

re: B. Lansdown.

"and a recommendation for three relief sewer projects."  

What were they?  Were these projects done?

Certainly have paid for a lot of studies.

re: C. Northeast Ann Arbor 

"addressed with temporary plugs in manhole pickholes".  So plugging manhole pickholes have been discussed before......

I posted my observation of the manhole cover pickholes in the Miller "basin" area, but I don't see it now.

Found it:

There are ten (10) manhole covers labeled SEWER on Miller where the traintracks pass over - the site of the flooding, stormwater overrun, shown previously.  Each of those manhole covers have two (2) pickholes.  None of those pickholes are sealed.  All are open.

Lori:

Can you please find the answer to my question.

re: B. Lansdown.

"and a recommendation for three relief sewer projects."  

What were they?  Were these projects done?

Thanks

Hi Pat, 

Yes, I have submitted your question to the City. I will notify you when the response is posted. 

~Lori

Robert, we have discussed I&I and whether or not it is significant, specifically, from pickholes during heavy wet weather incidents.  I believe we discussed some neighboring municipality that had closed all their pickholes and found a significant reduction of flow.   While this is not an exclusive remedy, every little bit does help.  What would it involve to address this simple task (cost, effort..)?

From the City, in response to Pat's question:

The recommendations from the study led to the “Southwest Sanitary Relief Sewer” project which was constructed in 1988. The project included a construction of a relief sewer in Scio Church Road extending across Pioneer High School to a sewer in Stadium Blvd.

Regarding Michelle's question, the cost, effort and effectiveness of plugging pickholes will be examined as part of the alternatives evaluation phase of the project. 

Thank you.  What were the other two projects?  Were they done?

From the City, in response to Pat's question about the other two projects:

We want to correct the misstatement in the response earlier in this thread: it should have said "3 relief sewer alternatives." 

The 1987 report from Soil and Materials Engineers, Inc., McNamee Porter & Seeley, and Harza mentioned 3 relief sewer alternatives were evaluated and one was chosen for implementation (i.e. the “Barnard Heights Relief Sewer” a/k/a the “Southwest Sanitary Relief Sewer”).  A copy of the 1987 report is attached for reference.