How Will Trenching a New Sewer Line Damage My Yard?

When our plumber diagnosed a collapsed sewer line last month, he referred us to a reputable excavation company who could replace the sewer line from the house to the alley. Our plumber knew the project would be a tricky one since the property was heavily landscaped and perched on top of an old river bed. What we didn’t expect was how disruptive the project would be.

Replacing a sewer line is not something that most people have to experience since sewer lines are usually quite sturdy and made to last for many years. Ours failed for a combination of three different reasons; severe tree root penetration, multiple dips in the line caused by shifting soil, and because the original sewer pipe material used ( which was tar paper) finally fell apart.

The most common way to replace a lateral sewer line is by digging it up and replacing it with a new pipe. What happens is that an excavator will bring a backhoe into the yard and dig a deep trench in order to access the old pipe. Even though a reputable excavating company will try their best to restore the yard back to the original condition, there is still a certain amount of disruption and damage that just can’t be avoided. Are you having a sewer line trenched in your yard? Here are seven things you can expect to happen to the yard during a sewer line installation and what you can do to minimize the damage:

1. Removing the fence

To get that backhoe equipment into your yard, anticipate losing part of the fence. In most cases, excavators can get by with just removing one 8 foot section. Of course, missing part of the fence means the yard can’t be secured.

Ask the contractor if he can provide temporary fencing during the sewer line installation. If your home backs onto an alley, consider moving outdoor furnishings, bikes, and equipment into the garage to prevent theft.

2. Lots of dirt

Our sewer line was buried seven feet below ground which meant that the excavators had to dig a very deep trench. I was stunned at the amount of dirt that came out of that 75 foot trench. If my boys were 15 years younger, they would have had every kid in the neighborhood over for some serious BMX stunt cycling.

To contain the dirt, the excavators had set down sheets of plywood which protected the grass, but did damage the flower beds and ornamental stepping stones.

When having your yard excavated for a sewer, clear away everything within 20 feet of the sewer line. This includes planters, stepping stones, edging, bedding plants, and newly planted veggies you might want to save.

3. Removing trees and shrubs

Every tree and shrub that was within six feet of the pipe had to be removed. While I did lose several lilac trees, we did save my 100 year old syringa bush. The excavator was kind enough to carefully lift it out of the ground and set it out of harm’s way during the digging. After the sewer line was replaced, he relocated it in a different location away from the line.

Expect to lose trees directly in the path of the sewer line. For smaller shrubs and younger trees, ask the excavator if they can be lifted and temporarily moved in hopes of saving them.

4. Damaged sod

Even though our excavators cut up, rolled, and removed a 30″ wide section of sod from the digging area, it wasn’t enough. Once they began digging, they uncovered the river rock beneath the top soil and had to dig a wider trench, resulting in damaged sod. It wasn’t their fault, but now we are left with a 36″ x 75″ stripe in our yard that will have to be sodded.

Expect to lose some of your grass and budget accordingly for grass seed or sod.

5. Lost topsoil

Because my house was built on top of an old river bottom, all my rich organic topsoil got mixed up with river rock during the excavation. It couldn’t be used anymore to smooth out the yard, and the excavator hauled away my top soil/gravel combo to replace it with a load of top soil brought in from somewhere else. This bothered me because I had no idea where that topsoil came from, and what nasty weeds and chemicals might be found in it. I let the contractor use the top soil to level out the lawn but wouldn’t let him bring any of this rogue topsoil into my vegetable garden.

For organic gardeners, let the excavator know your preference about bringing top soil into the yard to replace what had to be removed.

6. Settling

After the soil has been replaced in the trench, excavators will pour hundreds of gallons of water into the area to compact the soil. They’ll also drive over it with their equipment to pack it down even further. Despite all that work, over time the area may dip and the ground will settle further.

Anticipate that you may have to bring in more top soil and reseed the area in the future.

7. Damage to patios, trellises and other outdoor structures

We got off pretty lucky since all that was in the way of the trenches were a couple of trellises. However, had we built our new patio as scheduled last summer, it would have been directly in the path of the sewer line.

Before building a permanent yard improvement such as walkways, patios or decks, shed, trellises, gazebos or other outdoor structures, locate the sewer line first so as to avoid building directly over the line.

When a yard must be excavated for a new sewer line, a homeowner can minimize damage by moving as much as possible out of the way. He should also expect additional costs for restoring the yard back to the original look. The time to find out who pays for these costs is before signing the contract. While most contractors include a certain amount of restorative work in their bid, they generally won’t include the price of replacement sod or top soil, repair to garden structures, or the cost of new trees and landscaping.

Is there an alternative?

In certain cases, a sewer line can be repaired using a trenchless method in which a liner is pulled through the existing sewer line. Using the trenchless method means that yard is excavated in only two spots, at the beginning of the pipe and at the end. A trenchless method did not work for our property, but might be a viable solution for others who really would like to avoid having their yards torn up by a sewer pipe installation.

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