1. There was a minor amount of water (1-2" deep) in the bottom right section of the crawlspace when the owner purchased the home recently. The contractor on this job is one of those paper-pusher salesman types and told the owner she needed to build a bunch of french drains. It's possible the water has been there for years or there's a leaky pipe or something and there is no true drainage problem at all. [highlight #FCE94F]so the obvious question remains, do you really need a french drain? maybe a sump pump in the crawlspace is adequate.[/highlight]
2. That's a good question for the contractor who decided it was needed. Do you think building french drains on this was a stupid decision? It's all already built and I'm trying to decide how to handle it.
3. There's no survey so I don't know the elevations. The site is flat though all the way through with the exception of the front yard and driveway (top of image) slopes down towards the street like 5ft drop in 20ft length approximately.
4. There's currently a pump in each catch basin. Right now the catch basin on the left doesn't drain to the right, as shown. It pumps straight back up the page to the street and they made it so it empties out all over the neighbor's driveway lol. So I changed it to go to the other catch basin on the right. The one on the right currently pumps all the way to the street which the city said was illegal so I changed it to be an outfall in the middle of the front yard a couple feet down. Not sure if those two changes are good ideas or not. [highlight #FCE94F]So wouldnt it have been better to just slope the french drain towards the front yard and let it drain naturally without a pump since there is a good slope there?[/highlight]
5. The catch basins are grated because they have a metal grate that's sitting on top of them. They are basically just a drum that's dug into the ground and they cut a hole in the side and the french drain pipe is sticking into the side of it draining into it. I'm not sure if they should be separated from the french or not. One problem with that would be that a 1/8" per foot drain slope would put the drains below the water table after any reasonable distance so that's why I believe the pumps were installed. [highlight #FCE94F]If you have 4 foot drop in the front yard, you should confirm that your water table is actually 2-3 feet deep. or do you have springs next to the driveway?[/highlight]
6. Probably. I already told the owner I don't do drainage but she still insisted I handle it. I still have the option to either get a peer reviewer to help or sub it out completely if it sounds too hard for me to handle with no experience. I want to learn as much as possible and at least wanted to look into it a bit first and try to learn something about it before I have someone else handle it. I guess I'm trying to figure out if it's easy and I'm making it harder than it really is or if it's hard and I should let someone else do it. What do you think? Is this an easy drainage project or a pain in the butt one?
7. The water table is like 2-3ft down. It's a high water table. The catch basins are existing and built too low and are currently filling up with groundwater and the pumps are just turning on all the time and pumping groundwater out to the street lol. That's how the owner figured out the contractor was being stupid and wants me to fix it. [highlight #FCE94F]if you have perf pipe running into a catch basin that is below the water table, than yes, they will always run. do you really want these pumps running full time trying to lower the water table?[/highlight]
8. Yeah, I believe it is supposed to handle surface runoff. I believe the original idea with it was that there was water in the crawlspace so lets make sure it doesn't get down there again. It has rained since they built the drains and no water made it into the crawlspace so it seems like what they have is at least kinda working, assuming the problem wasn't leaking pipes that slowly accumulated over the years. [highlight #FCE94F]surface runoff should always be handled by surface drains, not by french drains. if it is surface water, proper site grading is the preferred solution[/highlight]
9. I don't know what kind of soil. Is there any nasty soil conditions I should be aware of that have a negative effect on catch basins and french drains? [highlight #FCE94F]ground water flows through the soil, so knowing what you are dealing with is important for proper design.[/highlight]
10. I'm assuming by grading plan you mean grading the site so the water drains in the desired direction (away from the house)? I don't think that's feasible on this one since the backyard has planter boxes and grass and stuff and the site is flat. It's not like there's a hill nearby flooding the house or anything. [highlight #FCE94F]sounds like you should evaluate surface drainage before you make that assumption.[/highlight]
