Has anyone ever worked with a vendor/manufacturer for a small prefab stormwater pump stations. The issue at hand is a client has had ponding issues on their site as it’s rather flat. Previously the client would have maintenance crew put a “trash pump” (small sump pump from Home Depot?) in the grass area to pump out ponding water into a nearby inlet. Drainage network eventually outfalls to a nearby wetland area. Current project is reconstructing a parking and converting the grass island into a small detention basin. Basin has an outlet pipe that connects to the adjacent drainage network. Client is still concerned that even with the small detention basin water will pond and overflow into the parking lot during heavy rain events, cycling through the drainage network and backing up into the basin.

Client had request we look into a small prefabricated stormwater pump station, for cheap of course at around $4k... Initial designs through a trusted vendor came with options at $20k and $120k. While the $20k option seems close to what we envisioned, it still seemed a bit over designed and the price tag is too much. Linked below is a unit from Australia, ~47 gallon storage and ~40gpm pump rate, for under $2k.

https://www.strongmanpumps.com.au/drainage/storm-water-systems/

If anyone has procured these types of stations in the USA that’d be appreciated. How would you size the pump itself? Our engineering budget is near depleted so we didn’t want to go through any sizing calculations. My thought would be taking the rational method and intensity of the 100-year storm to determine flow to that area but I’m curious if there’d be a better approach.