10-States Standards and TR-16 Standards applied to HDD
10-States Standards and TR-16 Standards applied to HDD
(OP)
Hi:
I'm just curious to hear from people about their experience with applying 10-States or TR-16 Standards to installation of sewer pipes using HDD(horizontal directional drilling). 10-States requires consistent line and grade between manholes. Most HDD work would have trouble meeting that standard especially in adverse conditions (i.e. - soil with cobbles, stones and boulders). Have you had HDD installations that meet this requirement? Do regulatory agencies offer a relaxation of the standards given the nature of the HDD process? I'd be interested in hearing about your experiences. Thanks, BC
I'm just curious to hear from people about their experience with applying 10-States or TR-16 Standards to installation of sewer pipes using HDD(horizontal directional drilling). 10-States requires consistent line and grade between manholes. Most HDD work would have trouble meeting that standard especially in adverse conditions (i.e. - soil with cobbles, stones and boulders). Have you had HDD installations that meet this requirement? Do regulatory agencies offer a relaxation of the standards given the nature of the HDD process? I'd be interested in hearing about your experiences. Thanks, BC





RE: 10-States Standards and TR-16 Standards applied to HDD
RE: 10-States Standards and TR-16 Standards applied to HDD
RE: 10-States Standards and TR-16 Standards applied to HDD
33.44 Slope Between Manholes
Sewers shall be laid with uniform slope between manholes.
33.5 Alignment
In general, sewers 24 inches (600 mm) or less shall be laid with straight
alignment between manholes. Straight alignment shall be checked by
either using a laser beam or lamping.
RE: 10-States Standards and TR-16 Standards applied to HDD
Some of the thoughts/concerns that I have had based on recent experiences are:
1. If we move away from laser straight line and grade, what standard should we apply to as-built drawings? The location of the pipe between manholes can no longer be predicted by measuring the location and elevation of the inlet and outlet. When does this become a problem?
2. If we allow bends in the pipe, does mandrel testing become more important to the likelihood that deflections/out of roundness becomes a problem to flow or passing maintenance equipment through it?
3. With significant changes in direction and grade, there become a greater chance that turbulent flow features develop. Will this create a larger release of corrosive and/or odorous gases to the atmosphere in the sewer? Will this increase the likelihood of manhole corrosion and odor complaints?
4. The minimum 8" pipe diameter, should that be revisited? The theory is that the smaller the diameter the more likely that HDD will be successful avoiding obstructions. Most sewer maintenance equipment can fit in much smaller pipe than it used to.
I think that we have enough experience as an industry to come up with specific concerns and guidance. When we discuss generalities, such as "maintenance concerns," if could give the impression that we are defending the standards out of an "institutional momentum" rather than fairly considering other points of view, regardless of whether that is true or not.
RE: 10-States Standards and TR-16 Standards applied to HDD
That being said, I think you ask some good questions. I believe I have seen in different specifications allowable ponding or apparent sags or bellies ranging from as little as only 1/8" all the way up to 10% of the pipe ID (i.e. slightly over 3/4" e.g. for 8" pipe). As someone who has been around practical open cut and HDD pipe work now for several decades (and is generally not in favor of relaxing Engineering standards or guides, meant to protect the public and important watersheds, without good reason), for some often tough dewatering and bedding work going on down deep in the ground, the 1/8" sounded pretty restrictive to me for even open cut! In fairness to Owners who wants a pretty straight ship, I guess the perception probably is that the alignment won't improve with the passage of time. All have a good weekend.