I'm planning to install a gravel driveway on my property by the end of the month, and I need to use a culvert for drainage. I've got a 20" culvert that I got for free, but I'm unsure if I need to excavate the ditch before I set it in place. The ditch is about 3 feet lower than the road surface. Can I just drop the culvert in and start filling with gravel, or should I do some excavation first?
3 Answers
I actually just tackled a similar project, and here's what worked for me: I dug about 4 inches deeper than the planned depth of the culvert and filled it with river stone. Then, I placed my culvert about an inch lower than the natural ground level for better drainage. After filling around it with more stones and topping with gravel, I compacted everything down so it’s solid. Oh, and make sure your culvert slopes slightly downward for smooth water flow. I learned that the hard way when I didn’t slope my driveway and ended up with puddles.
Just a heads up, local regulations can vary. In my area, there are specific guidelines we have to follow for culvert installation. It’s great that your township has given you the green light, but remember that the water flow during spring thaw can cause issues if you don't handle it right. You definitely don’t want to accidentally make a pond!
Before you lay down that culvert, consider what's at the bottom of your ditch. If it’s just grass and mud, you should actually excavate about 8-12 inches and fill that space with gravel compacted in there. Otherwise, the weight of everything might cause the culvert to settle too much into the ground. Ideally, you want to prevent any water from undermining it, so a little excavation helps ensure proper placement and pitch for drainage.