FAQs on the damage caused by driving or parking vehicles on or over a septic tank, septic system piping, or the septic drainfield: set #2.

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

FAQs #2 a Driving over the septic tank, piping, leachfield

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.

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 2019-08-30 by (mod) - Not OK to put a garden shed over a corner of the septic drainfield

Covering any part of the septic drainfield is a bad idea, Derek; the concerns are traffic and weight over the drainfield that compresses soil or even damages pipes, and when covered, reduction of evaporation and transpiration.

If the closest edge of a garden shed to the closest drainfield trench is 10 feet you may still be OK.

Watch out: But in your photo I see all those white PVC pipes right at ground level. What are those? If that's part of your septic system something is seriously wrong; septic leachlines would never be left exposed at ground surface, and your shed is right on top of some of that piping - not something you should attempt.

Watch out: I also see that the edge of your apparent drainfield is just a foot or two from nearby trees. That installation is likely to be rather quickly clogged by tree roots, leading to a septic failure.

On 2019-08-30 by Derek

I want to put a small 7x7 garden shed in my yard. I have laid an 8x8 section of patio stones down for it that is covering a small portion of where my drain field is - the back corner farthest from the septic tanks

It’s covering maybe 1/8 of the entire bed on a corner. In the image attached, it would be the corner nearer to the tree at the back.

My question is whether ANY weight at all can go on any portion of the bed - I’ve read about it affecting respiration or something. Please advise. Thanks!

On 2019-07-06 by (mod) - sauna set atop the septic bed - smells

Turtle

Well you could try mentioning that we have occasional reports of an explosion when people put a fuel-burning or electrical heater type device over a septic tank or drainfield where sewer gases are present.

On 2019-07-06 by Turtle

We purchased a barrel sauna for our cottage. My husband placed it onto of the septic bed. I hate the look of it.

Sometimes the smell seeps into the wood into the sauna and when having a sauna it stinks. There are ant hills on the septic bed and now I have them in my sauna.

Please tell me how to convince him to move it closer to the lake and not at the back of the property on the septic bed. Its 16' long with a change room and covered porch.

On 2019-07-03 by (mod) - Schedule 40 or Schedule 80 PVC pipe to avoid vehicle damage

You may want schedule 40 or even schedule 80 pipe and you may need to take further steps to protect it from damage depending on just what vehicles are going to drive over it.

I would expect your building or plumbing inspector to approved the ability to drive over a sewage effluent line provided that the pipe is of a type that is protected from vehicle damage.

On 2019-06-30 by Lisa - off site drain field

We have an off site drain field on our five acre piece of property. The easement for the drain line crosses the whole width of our property and is about halfway through the middle of the lot. We would like to build a shop on the other side of the line and have a road going to the shop. Is this possible if we aren’t driving over the drain fields but crossing the 10’ sewage easement drain line?

On 2019-06-24 by Amy

It is PVC pipe running from my septic tank to the drain field. Can we dig up about 12 feet of it, nearest the septic tank, and run it through a culvert then rebury the whole deal so we can then drive over that pipe? If so, do we fill the inside of the culvert, around the pipe, with dirt we dug out of there?

Or put some sort of other fill in there? Or leave it open?.... I cant seem to find anything about this anywhere. Also we live in the upper peninsula of Michigan, so below zero temps are definitely a factor.

On 2019-05-16 by (mod) - How do I find out how to fence off my septic Drainage Field without hitting anything in the ground?

Molly you'd either keep a generous obvious distance away based on a site inspection or you'd actually locate the drain lines.

See details at SEPTIC DRAINFIELD LOCATION https://inspectapedia.com/septic/Septic_Drainfield_Location.php

On 2019-05-10 by Molly

How do I find out how to fence off my septic Drainage Field without hitting anything in the ground?

On 2019-03-24 by (mod) - how to get felled trees off of the drainfield

Annr I can't say which does more damage, since

- soft soil and unprotected traffic over it risks crushing buried drainfield pipes and compressing the soil, ruining the field

- burning could melt plastic pipes if they are close to the surface and on occasion has set off a methane explosion if close to a septic tank.

I'd consider cutting the trees to smaller segments that can be dragged or wheel barrowed off of the fields.

On 2019-03-23 by Annr

A couple of trees came down in a storm. They lay on the lawn that has the laterals not far away. There seem to be only Two options for removal. truck and trailer over lateral system are to get to the trees and hall the wood out, or create a wood burning area which may be in part over the laterals and burn the wood there.

Will burning on the lawn above the laterals system do as much damage as the truck and trailer would?

On 2019-03-24 by (mod) - how to get heavy trees off of the septic field

Annr I can't say which does more damage, since

- soft soil and unprotected traffic over it risks crushing buried drainfield pipes and compressing the soil, ruining the field

- burning could melt plastic pipes if they are close to the surface and on occasion has set off a methane explosion if close to a septic tank.

I'd consider cutting the trees to smaller segments that can be dragged or wheel barrowed off of the fields.

On 2019-03-23 by Annr

A couple of trees came down in a storm. They lay on the lawn that has the laterals not far away.

There seem to be only Two options for removal. truck and trailer over lateral system are to get to the trees and hall the wood out, or create a wood burning area which may be in part over the laterals and burn the wood there.

Will burning on the lawn above the laterals system do as much damage as the truck and trailer would?

On 2019-03-17 by (mod) - We have water gushing out of one of the drainfield pipes intermittently.

LA it makes sense to have the suspect drainfield line inspected with a sewer camera or to do some exploratory digging.

I worry that the drainfield is essentially in failure but first let's rule out a crushed pipe.

On 2019-03-17 by LA -

We have water gushing out of one of the drainfield pipes intermittently.

There is a sewage smell and it is wet but not flooded around the pipe.

In the late fall, we had a large tree fall over the drain field, but the gushing water is before the area where the tree fell. Also, we have had an extremely wet winter this year.

Any ideas of what this could be? We had a new distribution box and a repaired clogged drain field pipe about 10 years ago with no problems until now.

On 2019-02-27 by (mod) -

Of course,
And inspected for function, damage, safety.

On 2019-02-27 01:38:25.926689 by Cindi

I own some property that has a septic tank.. but there is no house.. can i still have my tank pumped? For future reference

On 2018-12-01 05:02:32.520149 by (mod) -

Assuming you're talking about solid piping that isn't leaking into the drain field I don't think that would be a problem itself.

However there is a risk that if you drive equipment order the drainfield to dig trenches you're risking compacting soil and damaging the fields.

On 2018-11-30 by Chris

In order to drain away surface flow water that is partially saturating the drainfield, is there any problem with running drainage lines from surface intakes over top of a drainfield from the high side to below the low side?

Note that the distribution box and lines are approximately 4' deep while the drainage lines would be only approximately 1' deep.

Thanks, Chris

On 2018-09-14 by (mod) -

On 2018-08-09 by (mod) -

Well this doesn't sound good. If you know driving over the field is absolutely unavoidable you might reduce the damage by driving the crane over heavy planks to distribute its weight.

Any chance of using smaller equipment to cut up the tree in place and move smaller segments - that might help.

On 2018-08-09 by Jon

Leach Field Dilemma!

I understand that it is a bad idea to run a heavy vehicle over a leach field. Unfortunately, I have a large dead tree that has to be removed that will require the use of a heavy truck/crane and the only way to get to the tree is over part of my 40-year-old leach field.

Because of the weakened state of the tree, it would be too dangerous to climb the tree to cut it down. The soil in this area is very sandy. Any suggestions about protecting the leach field from damage would be greatly appreciated!

On 2017-12-03 by (mod) -

You might find the effects of drainfield damage subtle and delayed, ranging from a shorter life and reduced drainfield capacity due to soil compaction, to an actual drain line damage or collapse.

The latter shows up as a sewage backup or slow drains, or is revealed by having a plumber scan the drain interior using a sewer inspection camera

On 2017-12-03 by Angelina

We jusr purchased our first home with a septic bed. The inspector said our bed was great and advised us to never drive over it. On moving day it is obvious that the previous owners used a truck right over the bed to move. There are many heavy tire marks over it. How can I tell if this damaged the tiles?

On 2017-07-29 by David Engelmann - Using Permeable Pavers, Permeable Asphalt, or Permeable Concrete when installed Over a leach bed

Please do not just reply with a canned answer, With all of the advancements in Septic Systems Engineering and materials, Surely there must be a septic system design or combination of elements of design that can be used to place a septic leach bed / septic drainage field under a residential Driveway.

I had found an article where Using Permeable Pavers, Permeable Asphalt, or Permeable Concrete when installed Over a leach bed / septic drainage field provided evaporation at an approved / acceptable rate,

By utilizing Chambers with a carefully compacted washed gravel cover, Then covered with a filter membrane, and finally covered with soil and sand, with a permeable surface material on top. The area under the chambers when placed on the sand bedding diverted the compaction to those areas adjacent the chambers and not to the bedding areas under the chambers.

I believe they used a dousing systems under minimal pressure to force absorption into the bed. Any Information you or your associates have with links would be greatly appreciated

On 2017-07-27 by Kathy - pool over the leach line

We have our own septic. I put up an above ground pool by accident over the last line. We had a backhoe out and did some work. In addition, we had to dig part of the area where the line is because our house is on a slop.

How much damage have I done? The pool is a 20' pop-up that we took down last year and an to again this again. Your input will definitely help me decide if it comes down now, or later and ever goes up again. Thanks.

On 2017-06-06 by (mod) - septic tank covers rated for vehicle traffic - safety concern

Rhonda,

You ask an important question for which I don't have an absolutely authoritative answer, in part because I have no idea what boards are to be laid down and thus how much they will flex or will distribute or not distribute the RV weight. I also don't know what sort of septic tank you want to cross over.

A septic tank sporting a cover that is made of concrete reinforced with steel re-bar is a far different case from an old steel septic tank with a sheet-metal lid. In the latter case I'd say that no board-crossover-plan is going to be safe. In the former case ... it's still doubtful from the weight you give.

If you *know* that your septic tank is a "traffic-rated" tank and know who constructed it, you would still want to give the manufacturer a call to be sure that their "Traffic rating" included a 14,000 lb. vehicle and you'll need to know the dimensions of the tank and the spacing of the vehicle's axles.

Consider that unless you have installed a septic tank with a "vehicle traffic rated" or Highway Traffic Rated strength cover, a typical concrete residential septic tank, following the University of Minnesota design guide (as a typical standard) is built to carry the weight of the soil covering the septic tank and a vehicle wheel load of 2,500 lbs. That is a far cry from your 14,000 lbs.

Let's *pretend* that your RV is so long that only two wheels of it are on the septic tank at a time while you drive across (scared ***itless to forgive the pun) - you're putting a 7,000 load on the lid. Your boards would have to be both long enough to span well more than the septic tank AND to be so thick and rigid as to not deflect to place a significant load on the tank itself.

Septic tanks designed to withstand vehicle traffic ("HS20 vehicle traffic rated septic tanks") have not just a thicker lid but heavier tank sides and bottom too. HS20 loading is defined by the American Association of Highway and Transportation Officials (AASHTO) as follows:

A vehicle with an 8,000-pound (3,630 kg) front axle and one or more rear axles weighing 32,000 pounds (14,500 kg) each and spaced at least 14 feet (4.3 m) apart. This is a key measurement since it means that the vehicle's axle spacing is greater than the tank width, so only one wheel set is on the tank at a time. HS20 and H20 are used interchangeably.

Please see SEPTIC TANK COVERS at https://inspectapedia.com/septic/Septic_Tank_Covers.php

and also SEPTIC TANK DESIGN STRENGTH SPECS https://inspectapedia.com/septic/Septic_Cesspool_Design_Strengths.php

OK so what now: I consulted with an expert source on concrete septic tank design, the National Pre-Cast Concrete Association who, as is no surprise, have looked at the question of how to make it possible to driver over an existing septic tank. Here is an excerpt from the associations article on this that I'll cite below:

Engineering analysis demonstrates the tank design shown in Figure 1, initially designed for non-traffic use, can be made into a HS20 traffic-rated tank with careful engineering and many preconditions. Delta Engineers, Architects & Surveyors of Endwell, N.Y., performed the engineering analysis. The eight conditions are as follows:

1. 1 to 2 feet (0.3 to 0.6 m) of soil shall be over the top of the tank.

2. No more than one axle or two wheels shall be over the tank at any one time.

3. The minimum concrete strength will be 5,000 psi (35 MPa) compressive strength.

4. The top slab thickness shall be increased to 6.5 inches (165 mm). However, the bottom slab and wall thicknesses cannot be modified.

5. The tank contains a monolithic compartment wall.

6. The water table shall be at least 3 feet (0.9 m) below grade when the tank is empty.

7. The walls are supported at the roof by an interlocking recess that is cast into the top slab.

8. Reinforcing bar size, spacing and location shall be installed per Professional Engineer recommendation.

Barger, Eric, "Traffic Related [Septic] Tank Design", [PDF we will provide] NPCA, National Precast Concrete Association, 1320 City Center Drive, Suite 200, Carmel, IN 46032 USA, Phone: (800) 366-7731 Website: http://precast.org/ 28 July 2010, retrieved 2017/06/06, original source: http://precast.org/2010/07/traffic-related-tank-design/

Here is a copy of that article: https://inspectapedia.com/septic/Traffic-Related-Septic-Tank-Design-NPCA.pdf

On 2017-06-06 by Rhonda - lay down boards to distribute the weight of an RV (14,000 lbs) to safely cross over septic tank?

Can you lay down boards to distribute the weight of an RV (14,000 lbs) to safely cross over septic tank?

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?

...

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• SEPTIC TANK DESIGN STRENGTH SPECS
• SEPTIC TANK COVERS
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• PLANTS & TREES OVER SEPTIC SYSTEMS

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