Retention ponds why do we need them? My sub-division has two. Can’t the water just get drained to the river?
In: Engineering
Lots of people getting the first half of the answer right: when you develop an area, you increase the rate of runoff. To avoid flooding streams or stormwater pipes downstream, you set up a retention pond to slow the rate at which water drains off your site. It rains, and the water gets stored in the retention pond and released slowly into the stream or stormwater pipe to leave the site.
The answer to your second question is the answer to all things civil engineering: you can do it, but it costs more. Sometimes developers use underground retention. Basically, instead of an open pond, you have an underground structure that holds the water while it is let out slowly. You might use a really big pipe, an underground concrete vault, or this weird looking modular product that looks like milk crates. That way you can put a park, a road, or a parking lot over top of it. The only downside is it costs more money.
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