Gate City Foundation Drainage — Replacing a damaged corrugated pipe drainage system running beneath a sloping driveway
Shawn (Gate City Foundation Drainage @ YouTube; Gate City Foundation Drainage) is at a house with a steeply-sloping gravel driveway. A corrugated stormwater pipe runs underground within the slope and drains some catch basins and gutters at the rear of the house, but it was damaged when some earlier drain work was being done at the neighboring property. Due to the drainage system no longer working properly, the driveway was beginning to get washed out when it rained. The damaged line is to be replaced with PVC piping, and a sump pump hose exiting from the exterior wall will also be drained into the new line.
The existing corrugated piping at the rear of the home still seems to be working, so the plan is to leave it as-is. The new pipe system will connect to that existing piping near a downspout by the back corner of the house. Instead of reusing the original discharge that’s at the bottom of a retaining wall next to the sidewalk, Shawn plans to have the new system discharge next to the retaining wall instead.
Shawn’s crew member begins to dig by hand near the base of the downspout at the back corner of the house, to determine what exactly they’re working with there. An open pipe is discovered below the downspout’s elbow, although the corrugated piping that’s attached to the downspout appears to be routed toward the front of the house. Further investigation reveals that the opening is part of a T-fitting.
An excavator is used to start digging up the old pipe, but a wooden fencepost at the corner of the house is in the way. This fencepost is removed, and the digging continues. Since the new pipe has to attach to the existing T-fitting, the new trenching has to be dug relatively deeply. While doing this digging, an unanticipated steel pipe that the 811 service didn’t mark is discovered. It’s decided that the new pipe will run below this existing pipe. Shawn also removes a segment of the old corrugated pipe that was running alongside the house, and shows how it is about seventy-five percent full of debris.
A PVC Y-fitting is used below the surface to connect the existing corrugated system to some PVC piping that runs to the existing downspout near the corner of the house. The output of this Y-fitting connects to the long, relatively-straight run of pipe that goes down beneath the surface of the sloped driveway, toward the sidewalk at the front of the house. Care is taken to avoid damaging the sewage drain line that also cuts across the driveway.
Eventually, the digging reaches a large rock near the stairs leading up to the home’s front entry. The excavator is used to move this to the side, and the trenching for the new drain pipe continues. Some small portions of the upper part of the newly-laid piping are partially covered with soil, and a smaller sideline pipe is then added to capture the water coming from the sump pump hose that exits from the side of the home. The existing flexible sump hose is fed into a vertical piece of this solid PVC piping that runs up along the exterior wall of the house.
The remainder of the pipe leading down to the sidewalk is added. A square piece of flat granite rock is embedded in the soil next to the sidewalk for the end of the pipe to rest on. The final piece of pipe is laid down, and then it’s cut to length so the end of it drains over the piece of granite. The pipe is cut at an angle to try to help it blend into the slope of the driveway, to try to avoid it getting damaged.
With all of the pipe laid, the excavator is used to bury the new system. The dirt is graded away from the house, and the excavator’s treads are used to compress it. Shawn shows that some moisture that was in the existing pipes is already beginning to drain out of the newly-laid PVC piping, all the way to the sidewalk.
Shawn return several weeks later, during a rainstorm. Water is observed flowing out of the end of the pipe, as expected, and the system appears to be working. Although some gravel is still getting washed down the driveway when it rains, he notes that it seems to be much less than was getting washed away prior to the new system being installed.