Parking-lot runoff

J.C. Penney store, 4951 Slatten Ranch Rd., Antioch Map
Lowe’s, 1935 Arnold Industrial Way, Concord Map
AC Transit Ardenwood Park & Ride parking lot, CA 84 and
Ardenwood Boulevard. Map

The J. C. Penney store in Antioch was designed to meet updated standards requiring that large developments retain and slow runoff significantly, mimicing the original runoff pattern. This was done with fairly deep, concrete-edged basins — an approach pioneered in Contra Costa County.

Arbor and plantings in runoff basin at JC Penney store, Antioch
Above, parking-lot basin designed to avoid “hydromodification” — changing the runoff pattern.
Below, photos from August 2008 (left) and January 2009 (right). Roses rapidly filled the initially rather empty basins.

Newly planted roses in parking-lot basin

By two years, roses had grown to fill parking-lot runoff basin.

Although not all succeeded, most plantings in the runoff basins filled in rapidly. Below left, rock roses. Right, rosemary hides fine-leaved fescue.

Basin to retain parking-lot runoff, January 2011

Rain garden retains parking-lot runoff.

Below: Lowe’s Home Improvement in Concord aims at fewer but wider areas to treat runoff from its large impermeable parking lot. Instead of narrow planted strips throughout the lot, this store has relatively wide “rain gardens” at the main entrance and at the edges of its large parking area.
Colorful, drought-tolerant plantings in rain garden
Above: The entrance rain garden emphasizes plantings that are colorful winter and summer.

A redwood for screening and other California natives, including rushes
Rushes give a natural look to plantings designed to slow and filter runoff.

Left and above: Plantings in large rain gardens edging the lot have a more natural look, with California natives including redwoods and rushes. Cobbles at notches in curbs prevent erosion.
Large corner rain garden with swales, Ardenwood Park & Ride lot.
Swales and a large rain garden edge new portions of the AC Transit Ardenwood Park & Drive parking lot, opened in 2009.
Swale at AC Transit Ardenwood Park and Ride lot