Letters to the Editor

Spreading the Word

I love this publication. If I, a municipal engineer, am your target, then you have hit the mark. I anticipate its arrival each month, and I won’t throw old issues away until I am forced to.

If there was one suggestion it would be to expand your readership. I wish every civil consultant that does sanitary sewer rehabilitation would read your publication. In fact, it should be required reading. When I am with consultants, there are many times that I find I know more than they do about rehab techniques. And frankly, I don’t know that much. I would encourage you to continue to provide your readership with “news you can use.” The more “hands on” an article is the better it is.

I also think that every civil consultant doing sewer rehab work should be a member of NASSCO. Irv Gemora and crew have been doing a great job for our industry.

Keep up the good work.

Mike Smith, P.E.
Municipality of Bethel Park, Pa.

The Importance of Gel Strength

In regards to the article “Drilling Fluid Flubs” that appeared in the November 2008 issue, the author failed to discuss gel strength, one of the more important parts of an HDD fluid’s make-up. Gel strength is the ability of the fluid to support the cuttings, whereas viscosity, which was discussed in detail, relates to how thick the fluid is (or really defined as resistance to flow).

Since HDD is drilling a horizontal hole, the ability of the fluid to keep the “roof” from falling in relates to the gel strength and its ability to support and suspend. Knowing a fluid’s gel strength that would be needed for the soil that is being drilled is critical; a high  or low viscosity is really a secondary issue. Ideally a fluid should have the highest gel strength with the lowest viscosity as possible in any given HDD application.

Andy Fitzpatrick
HDD Specialist
Ditch Witch of Maryland
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