Waterline Cover 1

The ASCE Committee Report, "Pressure Pipeline Design for Water and Wastewater" (1992, and of course pre-9/11) includes the statement, "Depth of bury of pipelines is a function of the probability of line protection from construction damage, surface of line protection from construction damage, surface live loads, freezing and rupture, scour depth at river crossings and occasionally, pipeline grades." As I believe only one of these factors can arguably/clearly be related e.g. to geographical climate etc. vulnerability factors, and for that matter pipelines in many areas may also even need to come in or out of the ground at some locations, perhaps absolute/literal "minimum depth of cover" from a practical matter is somewhat of misnomer and a reliable regional or state "map" of same might be some hard to find?
That being said, I think many utilities, perhaps based on practice or experience, do in general like to get most extants of their uninsulated pipelines at least down assuredly below the "frost line", and I believe you can probably confirm this by looking at/pulling up some local city utility specs e.g. online and compare these to geographical frost depth maps (similar to a topo map) with a good search engine or other references. I think frozen and other expansive soil conditions, as well as surface loads and impacts, can exert great forces on pipelines, and pipe strength, damage resistance and ductility may be particularly important for these and perhaps other reasons when piplines must be buried more shallow than normal.

thank you rconner. What I was really looking for was the frost depth map you mentioned which I found with some help from a structural engineer in the office.

thanks again.

Skip all that mumbo jumbo, keep a good 6' of cover and you will be fine. For a large diameter line with heavier flow, you can get away with 4 or 5 feet, but try to maintain 6.

Check the AWWA pipe manuals. I know AWWA D100 includes a copy of a minimum-bury chart, but it's bound to be taken from some other AWWA standard. It's different from the frost depth chart.

Thanks JStephen for providing us this reference (I was not familiar with these tables in the D100 standard, which of course is the AWWA Standard for Welded Steel Water Tanks, so I obtained a copy of same). Figure 3 of this standard is entitled, "Extreme frost penetration - in inches (based on state average)". Figure 4 of the same standard is entitled, "Recommended depth of cover (in feet above top of pipe)" I looked to see where these tables/pipe cover was referred to in this standard. In this regard I saw that this standard states, "The extreme frost penetration depths in Figure 3 shall be the minimum depth of foundation below the ground line. Foundation depth shall be increased in localities where soil or other factors are favorable to deep frost penetration and may be reduced for piers resting on rock." I also noticed there was also another section,
"12.9.2 Pipe cover. Pipe cover shall be provided in accordance with Figure 4, unless local conditions dictate that greater or lesser cover should be used."