Walnut Creek: North Creek Church

2303 Ygnacio Valley Rd., Walnut Creek Map

bgnpchurchpondchain Walnut Creek: North Creek Church
Stiffened rules require not only that urban runoff be filtered to reduce pollutants, but also that large projects not increase peak storm flows. One way to address this is shown by these linked shallow basins at North Creek Church in Walnut Creek. (The project is new and landscaping still sparse.)

The basins are designed to be dry most of the time, yet give rain some chance to soak into soil. Sandy, quick draining soil covers a thick layer of gravel. Near the top of the gravel layer, a perforated pipe that shunts very high flows to storm drains.

Photo below shows green pipe linking ponds, bottom left. It also shows that the system has been partly defeated by removing the sides from the raised concrete drain meant to keep the pond from overflowing. Because of the open sides, the pond will not fill and hold back peak storm flows as it should.
bgnpchurchbaddrain Walnut Creek: North Creek Church
bgnpchurchgooddrain-234x192 Walnut Creek: North Creek Church
bgnpchurchroofdrainlandscaping2-235x95 Walnut Creek: North Creek Church
Left above, a properly constructed drain designed to prevent overflow, with intact sides. Left below, brown pipe drains roof to detention basin.
bgnpchurchsandfilters Walnut Creek: North Creek Church
Below, space was limited for retrofit for parking lot for adjacent church school. The metal plates, with access doors, cover sand filters that both filter and retain runoff.