You can get those plastic rivets online or auto parts stores.
Most modern cans are using them in inner fender well, and other places. So you can pick some up cheap.
I just put my blades in vise, and use 60 grit flapwheel on drill...then cone balance
First I soak them in pan of water for ez clean. 20 minutes, crud wipes right off & no dust fumes.
I'd be shocked if it was permitted to fill the swale with gravel. That would look bad.
Once grass starts growing, it will be fine. Just have to avoid the bottom when wet, or push mow hat part only.
The ditch (swale) would be "Right of Way" for underground water / gas etc & not actually owned by homeowner.
Can't make changes like that without written permission. But homeowner is to care for it.
In fuel storage, phase separation occurs when enough water contaminates the gasoline, causing the ethanol to attach itself to the water molecules and leaving two distinct layers in the storage tank.