gardenfish said:Such a wonderful thing! And very environmentally sound. We should do these here; we do have an enormous amount of rain runoff; and in agricultural areas run off from fields invariably contains high nitrogen fertilizers; once these go into the creeks, streams, rivers and lakes they cause algal booms that deplete the oxygen and kill the fish.
That's what caused all the brouhaha about that hog farm that was placed on Big Creek in Northern Arkansas. Big Creek goes directly into the Buffalo River, our first National River. It took 7 years, I think, to finally close that hog farm down. Adding to the issues was the fact of the sub strata up there; it's limestone karst; and absorbs water readily and carries the excess nutrients and pollutants into the underground aquifers.
The one limiter to them (besides size...keep in mind I have have almost 300 cubic feet of dry well...the first almost 200 was technically enough to handle my yard, but I didn't realize why it was still flooding before installing the last ~100 cubic feet...to handle a well-designed 1500 square foot exterior space plus 600 square foot roof) is that they're less effective where the water table is high and/or the soil has low absorption rates. DC's clay soil isn't ideal for dry wells, but they work for me because I'm on high ground (I can see the Washington Monument from over 3 miles away in a direct line because I'm over 100 feet above its base), so the ground actually drains out pretty fast. The amount of holding that a farm would need would be astronomical, and if the water table is high (next to a river, it usually is), they would need to be even bigger. Otherwise they just overflow and it's like you never spent the money. They're much better for household drainage solutions. There are tank-style solutions (literally a tank installed in the ground with french drains capturing surface water and directing it in) for larger areas, but they're really expensive and take even longer to drain because you displace more soil that would otherwise be uptaking the water.
ETA: I installed the metal edging yesterday. I now have a 3.5-4.5" buffer from water running in from the neighbor's downspout. There's some natural runoff that occurs because the back half of their yard is a smidgen higher than mine, but what hits their lawn (cough weeds) and upwards walkway was nowhere near enough to cause the kind of flooding I was seeing.
