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

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FDD Horizontal Directional Drilling and Bentonite Drilling Mud - Irv Mermelstein Emails and Attachments

Posted by Charlie Fleetham on 12 May, 2014
Category: No category

Good morning,

Per the request of Irv Mermelstein, please find attached two emails and various attachments regarding FDD Horizontal Directional Drilling and Bentonite Drilling Mud. As some of you may have already received communication on this topic from Mermelstein, I thought it was appropriate to inform you all.  Also, please be aware that the project team has discussed some of  Mermelstein's claims regarding Horizontal Directional Drilling and Bentonite Drilling Mud. Currently, we are not planning on discussing this topic on Wednesday night, though it may become a topic for the June combined SSWWE/FDD CAC meeting.

Charlie

Comments

Robert Czachorski on 12 May, 2014:

Folks,

The City (Nick Hutchinson) asked me to post the information below for the CAC to address the topics raised by Mr. Mermelstein's email.

Take care,
Robert

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Burial Depth of Sump Discharge Lines
 
Assumptions have been made that the burial of the sump discharge line 24-inches deep is indicative of a systemic defect in the City’s FDD program. The City’s  24” burial depth (minimum) standard is based on the following requirements and assumptions:

a) The sump discharge lines in the ROW and on private property is required to be constructed with a positive slope meeting the project specifications and the building code based on the size of the pipe.  Each construction installation has been verified and approved by Planning & Development Services.

b) With the required slope, the pipes will not have standing water in them.

c) It is also assumed that the sump pump discharge water is “warm” at about 55 degrees and will not have time to cool down and freeze in the sump lead or curb drain if positive slope is present.

These requirements and resulting conditions promote effective functioning of the sump discharge line and curb drain, even under extreme cold conditions like those experienced last winter. The specifications themselves are not indicative of any systematic defect in the City’s system.

It is possible that in the case of the two houses along Avondale that the sump leads may have “dips” or flat sections in them where the water could collect and cool.  When it was pushed downstream with the next pumping cycle it became susceptible to freezing in the curb drain due to the “icicle” effect.  If such sump discharge line and curb drain collector line dips exist, they do not meet the City’s specifications.

The City plans to investigate the reported cases of pipe freezing and identify any necessary corrective work.

Use of Drilling Fluid in Curb Drain Installations

Concerns have been raised recently regarding the use of bentonite drilling fluid in the installation of curb drains in the City’s FDD Program. Bentonite is a clay material that is mixed with water to form a slurry to assist in the installation of directionally drilled pipes.  The material is required to be inert, and is not toxic. The same material is widely used in the construction industry in the drilling of drinking water wells.