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Septic system collapse and truck rescue (C) Daniel FriedmanFAQs on Driving Over Septic Tank or Fields

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Questions & answers about driving or parking vehicles on or over a septic tank, septic system piping, or the septic drainfield:

These FAQs explain the restrictions on driving over septic system components and explain the risks involved.

This article series explains the problems that occur if septic components are located under a drive or parking area.

Our page to photo shows a big effort underway to pull a dump truck out of a seepage pit.



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FAQs about Driving over the septic tank, piping, or drainfield.

PHOTO of a septic seepage pit collapse when a truck drove over it.

These questions & answers about driving over septic tanks, drywells, cesspools, drainfields, leachfields, or soakaways, were posted originally at DRIVING or PARKING OVER SEPTIC - be sure to review that article. Also see SEPTIC & CESSPOOL SAFETY.

Watch out: as we report at SEPTIC TANK ACCIDENT REPORTS, driving over and damaging a septic tank cover or lid can result in a later cave-in, fall-in, or extremely serious hazards. While it is possible to purchase septic tank covers that are rated for withstanding heavy loads, even vehicles, as-installed residential septic tank covers are not normally capable of withstanding such traffic.

On 2017-05-28 by (mod) re: Can you run underground pipes over the septic tank

Marc

What sort of pipes and for what purpose. Sanitary codes specify, for example, a minimum clearance distance between potable water pipes and septic components. And running other pipes such a as a waste line over a septic tank, depending on the tank lid depth, may invite breakage of the line.

On 2017-05-28 by Marc

Can you run underground pipes over the septic tank but avoiding the lids? I know its not preferred but the site has no other way around it. It will be inspected ( Santa Cruz Ca.)

On 2017-05-19 by (mod) re: why can't I just lower the sewer line to avoid a damage problem ?

Leslie

You probably can't lower an existing drainfield connecting pipe since it'd just sit filled with wastewater; the lines need to slope between 1/8" and 1/4" per foot from source to destination.

But you should never allow heavy equipment nor any vehicles to driver over a drainfield. Even if a pipe isn't broken the soil compaction will destroy the fields. If a pipe runs under an area that's not a drainfield itself and needs to be driven over, then you need a properly-sized heavier pipe (perhaps schedule 80) properly bedded in sand and backfilled.

On 2017-05-17 by Leslie

Thanks I will surly propose that question to the man coming to give me an estimate. Any thoughts on the drainage pipe compromised so close to surface and could that be dug out an lowered underground more? thanks again

On 2017-05-17 by (mod)

"right up to the top", Leslie, sounds as if an outlet pipe between your septic tank and drainfield was blocked. If that's the only problem we're lucky since that's a rather modest repair. I'm not sure what the repair person saw that argues to replace the whole field, though I'd agree with him that the condition of a 30 year old drainfield is always suspect.

Start by excavating and replacing the broken pipe; then let me know what happens, and use the page top or bottom CONTACT link to find our email if you can send along photos of the work.

On 2017-05-17 by Leslie

Found a soggy spot in my front yard while mowing. its a good 40 ft from the septic tank entry. I poked around and found a broken plastic tube. I called the septic guy who pumped out the tank which was right up to the top with liquid; not a lot of solids.

He said it wasn't draining at all. Well it is... if there is water 40 ft away coming from that drain tube The rest of the yard is dry. He said i would have to replace the whole field. The tube with the leak is right at the ground surface, cant it just be dug out and lowered and reaireared with more rock and soil??? and if its not draining cant they try to clean out the lines first before digging them up? the system is approx 30 years old. Any help would be great!! thanks.

On 2017-04-15 by (mod) re: horse grazing over the drainfield?

Lisa, please see GRAZING ANIMALS OVER SEPTIC SYSTEMS and let me know if you have further questions.

On 2017-05-01 by Lisa

Can horses pasture over a septic drain field without damaging it? We have four horses and the field is about 100 x 140. Fencing and fence posts would be placed outside the drain field.

On 2017-04-15 by (mod) re: can I repair damage caused by driving a truck over the drainfield

yes of course, by excavating and repairing the points at which drainfield lines were crossed

On 2017-04-15 by Joe

I've driven truck and damaged septic field.can it be repaired?

On 2016-11-09 by (mod) re: can I drive a boom truck over the drainfield to remove trees?

Kevin:

Good question. I have just arrived back in our lab from Two Harbors. The frost line in southern MN has been studied (in 1993 - see this MINNESOTA GROUND FROST STUDY [PDF] original source: http://files.dnr.state.mn.us/natural_resources/climate/summaries_and_publications/minnesota_ground_frost_study.pdf ) teaching us that if you wait long enough for the ground to be frozen to the depth in your area (perhaps 36") you may be OK.

Back before global warming was hot on our necks, the deepest frost was found in the second and third week of February. If your area has a "sudden increase in snow depth" you can get to maximum frost depth earlier if the snow remains (through say February) without melting. The study said that there were wide variations in frost depth in Southern MN as snow cover increased so this is not a hard-fast rule.

I speculate that if you do not see the truck leaving ruts in the ground you may get away with little or no damage to the drainfield. In areas where I was worried about soil compression I bought a few sheets of plywood to lay down over critical spots.

On 2016-11-09 by Kevin

I have some trees to be removed. Is it safe to drive boom truck on drainfield once the ground is frozen this winter. I'm in southern Minnesota.

On 2016-11-05 20:59:24.001848 by Charlie

Thanks for your suggestions. I live in rural New Mexico sorry. In many ways its still the wild west

On 2016-11-01 16:11:36.259060 by (mod)

Aw geez, Charlie. One more real-world case illustrating that "expensive homes" are not necessarily built by a builder with any more sense than less costly homes.

In my experience, no competent, honest building code inspector would approve such a design. You will want to check with your local plumbing or building or health department - whomever approves septic designs where you live, to obtain a copy of the local septic code. Typically local codes (modeled on Shasta CA septic regulations as an example www.co.shasta.ca.us/docs/Resource_Management/ehd-forms/Septic.pdf?sfvrsn=0 ) state something like this:


"The site of the leach field and 100 percent of the replacement area shall not be covered by asphalt, concrete, or other impervious material or [sic should be nor] subject to vehicular traffic or other activity which would adversely affect the soil or leach lines". [Op. cit.]

I use this citation because you don't say where you live.

What does your local building department say? Did they approve this septic system as built? Can you get a copy of the septic plan as approved?

The issue isn't just crushing pipes it's that there is no aeration, no oxygen, and no transpiration. So the drainfield won't work to treat effluent even if it does seem to dispose of it.

I agree that extending the drainfield into an open area makes sense. If I were building it I'd ask my local plumbing or building inspector if they'll approve an extension without making me chop up the drive to replace the perforated piping; if the inspector says no, then I'd look into a plumbing contractor who has the equipment to re-line or seal a perf pipe line to get thee effluent to the new destination. If you can achieve that by gravity flow you're in good shape. if not there's the added work to install a pumping chamber and effluent pump to a new drainfield in a suitable location.

(Or move the drive if that's feasible).

Please see SEPTIC & DESIGN CODES & SPECIFICATIONS U.S.A. at http://inspectapedia.com/septic/Septic_Design_Regulations_U.S.A.php for links to septic code sources for various U.S. and other communities.

On 2016-11-01 07:50:33.795065 by Charlie

Jim,

I have a two year old expensive custom home. The septic drain field was placed under the drive by the contractor who built the home. It was then paved over. It is now failing. I am facing a large unexpected expense. Your explanation is clear. I am now looking for references (code, rules, formal guidance) that say this should not be done. Can you help?

Next, best route to extend drain field is from end away from septic tank. I think it is sufficiently protected to prevent crushing. Is using the existing drainfield pipe a performance issue?

On 2016-10-28 20:56:33.778326 by Anonymous

Thanks for your comments. I really appreciate it. jim

On 2016-10-28 20:12:10.788073 by (mod)

Fair question, Jim. I really dunno. I think a lot depends on soil conditions and depth and type of piping and installation details. If your tractor never leaves depressions or ruts on the ground surface over the drainfield I don't think it's likely to be the culprit.

On 2016-10-28 15:58:16.714779 by Jim

I have a Kubota BX that weighs around 1300 pounds. I didnt think about it at the time. What are my chances. My tank worked fine all summer. Last winter however someting froze. Im not sure the two are connected.

On 2016-07-22 20:57:23.568652 by (mod)

Great question, Mary. Not one that someone could possibly answer for certain by mere e-text: variables that affect the risk include:

- soil properties, density
- soil moisture levels
- pipe material
- existing pipe condition
- weight of the vehicle.

If you're facing a simple one-time crossing event, consider laying down pieces of plywood to distribute vehicle weight.

On 2016-07-21 18:58:43.827904 by Mary Skarzenski

If septic laterals are at least 3 feet underground, and have been there for 17 years, is it safe to drive a car over them?

On 2016-06-24 17:30:01.261913 by (mod)

Even if the drive was gravel, if it passes over the soil abaorption area, or worse, over piping, the weight of vehicles compresses soil and may break pipes - ruining the fields; remember that it's not just light-weight cars but heavy trucks that may pull into a drive from time to time.

If the drive was on the very edge of the fields it might make little difference; you need to know where & what components and pipes are located, the overall field design and layout.

Have the septic system inspected and tested; if it's not in failure I doubt that it's cost-justified to excavate, move, adjust soil etc.

On 2016-06-24 05:01:58.458866 by Melissa

All reports state no driving/parking on the drain field area. I am looking at buying a house and the driveway covers the edge of the drain field. Our best guess is the driveway was originally gravel and therefore an acceptable material. Then someone upgraded to an asphalt drive without realizing the drain field was there. Are there any solutions? What if it only covers a small portion (and how could we find that out?). If it is unsafe, how can it be fixed ?

On 2016-05-17 11:41:12.046741 by (mod)

Anon: there is no precise answer to maximum weight over a soakaway bed because bed design, soil properties, depth of the buried pipes, soil moisture and other factors may vary widely.

But generally considered "safe" are riding lawn tractors in the 500-700 pound range.

A 2000 pound lawn tractor is pushing your luck. A VW Beetle weighs about 3000 and a Toyota FJ Cruiser about 4000 pounds. Certainly those would be considered "cars" that ought to stay off of a drainfield.

If you see that a vehicle leaves ruts or depressions in the soil over which it is driving that's a warning that the combination of weight and soil conditions is risking damage to the drainfield both by breaking or crushing pipes and by compressing the soil. My opinion is that regular and varying passage over whole area of the fields by a heavy motor might be considerably worse than a single trip as one trip may break a pipe but won't compress the entire soil area.

On 2016-05-17 11:19:27.524240 by Anonymous

maximum weight over weeping bed

On 2016-05-17 11:17:32.480434 by Anonymous

can a 2000 pound lawn tractor drive over weeping tiles

Question: best materials for a walkway over a septic field

(Sept 27, 2012) Clark said:
I am hoping to drive a 2220kg Thomas loader over a septic system for the removal of tree brush. We plan on laying down thick plastic pads to disperse the weight of the loader. What is your opinion on the risk of this action?

(Dec 11, 2012) beth said:
designing landscape for nursing home. is there any type of material that can be used for a walkway so that it can cross a leaching field?

Reply: in the U.K. see Section H2 of the Building Regulations about pathways over septic fields. In the U.S. minimize the surface blockage and weight.

Beth, in my opinion a walk across the septic field should cover so little area as not to interfere with field function. I'd use dry laid slate if not for the worry of trip hazards for your occupants.

But I have a secondary worry. Make sure that during construction heavy equipment is kept away from the fields to avoid damage. As some readers comment (below) "you can't construct a 'path' over a septic tank drainfield. But "path" in the U.K. can have a very different meaning than in the U.S. or Canada. In the U.K. there are old right-of-way common access pathways across otherwise private land. These paths can have significant usage - which is why one would not route an access path across a septic leachfield or soakbed. But on private property where there is limited access the issues are less severe and walking across a working drainfield should not harm it.

(Jan 9, 2013) Maureen Webb said:
In the UK, you cannot construct a path over a septic tank drainfield - Section H2 of the Building Regulations.

Reply:

Maureen:

A path "constructed" over a drainfield, especially if it means carrying equipment or traffic that compacts soil, would, I agree, be a bad idea.

On the other hand, for a properly built and working drainfield, a human (not livestock) just walking over the field, will be harmless.

Comment:

(Dec 22, 2012) Great page said:
Very informative site, thanks for your time.

Question:

(Mar 27, 2013) Bill said:
Can you give advice. A neighbour has dug up half our septic tank filter system (which is on their land) and damaged one of the pipes leading from the septic tank - which they said they'd made good. They were putting in foundations (within 15 m of the filter system - which the council allowed). They've driven all over the filtration site. The council won't get involved and are now saying that water is leaching from our filter system onto their land and they're going to take action against us.

Reply: neighbour dug up part of our septic system which is on their land

xBill,

What a mess. Your septic system is almost surely illegal right - in all of the local sanitary codes I've seen you are not allowed to dispose of your septage nor septic effluent off of your property (onto a neighbor.)

You will want to relocate your septic tank and other components to be completely on your property as well as far enough from property boundaries and other site features to be code compliant.

Question: rock garden over leach field

(Mar 25, 2014) Tricia Williams said:
Can I place a rock garden over part of my leach field? I want to put it right in the center and then plant bermuda grass over the rest of the field, around the rock garden.

Reply:

Tricia

Yes and no. Yes if you're talking about light-weight stuff and no use of heavy equipment to set it in place and no deep-rooting plants.

No otherwise.

Please see PLANTS & TREES OVER SEPTIC SYSTEMS at

inspectapedia.com/septic/Plants_On_Septics.php

Question: sports area over the septic soakbeds?

June 30, 2014) Alison said:
We want to create a sports area for the grandkids when they visit and the flattest and most unused area of our property is over the septic field. Could we add more topsoil, turf it and then use it for games such as badminton, croquet, bocce, horseshoes and golf putting? Obviously we would not dig any holes within the field itself and use would be infrequent.

Reply:

In my OPINION, normal human foot traffic over a working (not leaking, not unsanitary) septic drainfield should not damage it.

BUT the construction of a play area over a septic field by using equipment that might compress or disturb soil or break a buried pipe risks costly damage

AND adding topsoil can seriously interfere with proper drainfield operation by reducing the oxygen level in the soil below, thus reducing the level of aerobic bacterial treatment, thus leading to discharge of contaminants to the environment. Adding topsoil also can reduce the disposal of water in the effluent dispersal system via evaporation.

Question: ok to put up a post-supported structure over the septic fields?

(July 21, 2014) Steve said:
Could I erect a building on posts above our field bed knowing exactly where the lines are and placing the posts to avoid them?

Reply:

(July 23, 2014) (mod) said:
You might be OK with the posts if you stop there.

I would not build a structure over a drainfield. What happens when you need to repair or replace the fields? And what are the chances that we an build a structure without ever driving machinery close-by, ruining the fields?

Question: drove the moving van over the septic area ... it was only there for a short time. Is there damage?

(Sept 18, 2014) Ann said:
Recently while moving my son backed the moving van over the septic area. It was there only a short while before it was noticed and was asked to move the truck. How can we determine if any damage was done?

Reply:

good question, Ann,

If your system has a distribution box, open the box and see if there are signs of backup or failure to accept effluent in one or more of the lines.

Beyond that, I don't know a good answer. In my OPINION if there is no sign of blockage such as a sewage backup, new odors, or wet areas developing in the drainfield or near it, then it's not worth digging up the spot to see what happened.

If you do find signs of a backup at the D-box or on the ground surface or in the septic tank and were looking for a broken crushed drainfield line, then I'd dig and look at just where the van drove over the field trenches.

Question: build a small Tee-Box on the septic fields at a golf course

(Oct 21, 2014) Mike Allara said:
Can I build a small tee box on my septic field at my golf course? the field is reasonable large and I would not look to add anything bigger than 4 x 5 with some elevation.

Reply:

(Oct 21, 2014) (mod) said:
A tee-box indeed sounds like a golfing system component. If you mean a tiny receptacle to accept golf tees, just put a birdhouse-sized box on a little post and don't drive the post into a drainfield trency.

If you mean a rain shelter or larger structure, it'd be smart to keep such structures away from the fields. For that matter, we might worry about field compression and damage if people are driving golf carts over it too.

If you mean the distribution box, the size needed is determined by the number of connections the box must feed. Or you could daisy-chain several.

Question: Nina's contractor leaves a mess

24 Feb 2015 Nina said:
The septic tank left the drain lines lying on top of ground. It looks awful!

He also put the lines in our driveway! He is supposed to be a professional

Our septic tank guy left the drain lines on top of ground! Is this acceptable?

He also put the drain lines in our driveway!

Reply:

Nina I don't have a clear picture of what the heck is going on but it sounds as if a septic field installation is unfinished.

Certainly we wouldn't put a drainfield under a driveway, but pipes (rated to withstand the weight of traffic) might have to cross a driveway to carry effluent to a drainfield or septic tank.

Question: picnicing over the drainfield: dirt, mulch, rocks or what?

24 Feb 2015 karen said:
We have grass and couple of picnic tables over our leach field but we would like to put some more dirt or some mulch because the roots from trees and the fact that grass doesnt grow too well from limited sunlight in this area. We were thinking of putting mulch, small stones or rubber mulch down which is easy to walk on. What material is okay to put down over a leach field??

Reply:

Karen,

What we want to avoid over a leach field are plants that might send down deep roots that invade the system and clog it, and of course we don't want to drive equipment over the field while delivering anything heavy as that too can damage the fields. Your citation that there are trees over the septic fields is itself a worry.

a complete guide is at PLANTS & TREES OVER SEPTIC SYSTEMS

If you were to replace a small area of grass with stone, say around a picnic table itself I doubt that'd have a measurable impact on the septic system. But if you were to add gravel over large areas, while transpiration (evaporation) of effluent may continue, you're losing the benefits of moisture movement that is achieved by the grass that was there - a result is a wetter lleachfield and a shorter life.

Question: signs of damage from driving over the septic system or drainfield

(Apr 7, 2015) Ruth said:
Someone just drove over our septic area about 4 feet from the riser. How soon should we notice a problem in the house (gurgling drains,etc.) if damage to the line was done?

Reply:

I can't say, Ruth as we don't know enough about your septic system piping layout. If an exit line between septic tank and drainfield were totally blocked and if the septic tank has no leaks, you'd notice backing up drains as soon as you've run enough wastewater to fill the septic tank that last few inches to its lid and to fill the piping between tank and house - normally within a day. But a cracked or partly crushed line could still be damaged but take months to show up as a problem since it can take time for soil or roots to fill in the damaged piping.

LInes buried very deeply are less likely to have been damaged by a drive-over.

Since you know exactly where the line was driven-over, you have the option of digging to look.

Question: walkway over septic?

(July 15, 2015) Dave said:
Can I create a walkway (patio stones/interlock) over a tile bed (in Ontario Canada)
The walkway would only be from 4 to 6 feet wide and would cross the tile bed

Reply:

Dave:

You've probably read that in general we don't want to cover the absorption bed and we don't want to compress soils nor drive over it. I don't know the total size of your particular tile bed but I speculate that the area that is covered and thus lost to transpiration / evaporation by simply hand-laying interlocking pavers to walk over the area would not be significant and so may be just fine. MAYBE.

If you are going to drive equipment over the "walkway" then I'd vote against it. If you are simply going to have people and maybe pets walking on it that's likely to be ok.

(July 16, 2015) Dave said:
Thank you for your info. A little more info on the possible project.
The walkway would only be for people and pets to access the home(looking to relocate entry door to home) also I was thinking that I could use a combination of flagstone and clear stone to create the walkway. Would that be acceptable?
Would that affect the tile bed, especially in the winter (we get temperatures as low as -40 Celsius)

Reply:

The weight of flagstones and people walking a narrow path across a septic field shouldn't harm it;

Question: ok to drive on planks over the drainfield?

(July 20, 2015) Marg said:
Would it be Ok to drive a bucket truck on to the lawn on planks for a short period of time, just long enough to pressure wash the peak of the house, let it dry and paint it?

Reply:

Marg

If the weight of the truck is sufficient to compress soil or worse to break a buried line, that takes only seconds. So "a short period of time" won't avoid trouble.

IF and I do mean IF your contractor can put down enough heavy 4x8 sheets of plywood to distribute the weight over a larger area than would be done by planks you might get away with it. Use 4x8 foot plywood of 5/8 or better 3/4" thickness. Planks are more doubtful.

OR you can make sure that the route of the truck is not over piping or soakaway bed trenches.

Question: septi cpipes run under a road?

(Sept 15, 2015) Joseph said:
Is it common to build a septic system where the pipes will be laid under a road? What problems could occur over time. If there is no other option, what measures should be taken to prevent damage to the system?

Reply:

If we're discussing solid piping to move effluent to a drainfield, proper pipe type (schedule 80 or better), depth, trench preparation and backfill can protect the pipes from damage from the road above. We wouldn't put part of the drainfield itself under a road - it would lose its evaporation capacity for that area and repairs would be quite costly.

Question: I just ran a large mini excavator across a drain field perpendicular to pipes

(Sept 25, 2015) David N said:
I just ran a large mini excavator across a drain field perpendicular to pipes . The machine had tracks not tires and the tracks are at least 8 foot long . Since it had tracks it didn't sink into areas where pipes were ( I could see where soil was lower where the pipes were buried) I'm worried that damage may have occurred, how do I tell if it was damaged ? Only crossed it once.

Reply:

David,

All the worrying is my profession I have to admit that not every possible catastrophe is going to happen. Your septic fields may be okay. It depends on

If there is a distribution box upstream from the leach field lines that you crossed you can open that box to watch for signs of an effluent backup.

To go further would require excavation either at the end of the leach line or in the area where you drive across it before digging up such lines to look for damage I would watch the d'box as I said and I would watch for effluent break out or back up anywhere in the system.

if you don't see those problems then I think the further excavation is probably not justified. Do keep us posted on what you see.

...


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