I had a chance to check out another finished drainage project in El Segundo. The new portion of the parking lot looks great and ties into the existing really well. The original lot had another loading dock for trucks to back into. The client wanted to fill this area in to add more parking and to be able to back trucks into the warehouse.
The new concrete area was tied into the existing in a way that would not require sump pumps for the addition. The existing grade of the parking lot left very little room to make this work. Especially with tying into the existing swale for drainage. The building outline to the swale was very flat. We also had to keep many existing features which proved a real challenge.
One of the features was an existing sump pump for the other loading dock along with roof downspouts. We also needed to make sure there was a trench drain in front of the loading door just in case any water came back towards the building. The new trench drains, lead to a new catch basin that was built above the existing sump pump vault. Imagine before construction where I am standing would be about 5' below the concrete with a sump pump vault underneath.
The trench drain was over designed to compensate for this. Generally whatever we size, the contractor will build a smaller version of the trench drain. So if I want a 4" trench drain I have to make sure to call out a 12" wide one. We had this conversation in the field between myself, the soils engineer, and the contractor. The soils engineer even laughed because he knew what I was doing just as the contractor said he was going to put a 2" wide trench drain.
The owner of the building left and a new logo was put up. Being fascinated with airplanes, seeing the Air Force parking striping on most of the parking spots was nice to see. This is a better view of how the drainage slopes towards the existing swale. The existing swale is surrounded by new asphalt concrete, while the new swale is surrounded by concrete.
This parking lot came out very clean and the drainage works well. We were able to take most of the existing stormwater off of the pump system and use sheet flow instead.