Reflection on a seasonal treatment wetland concept for South Gate at the LA River
March 6, 2012 § 3 Comments
Here’s a concept I developed back in 2002, while a staffer at North East Trees, that might interest the stormwater wetland folks. A couple of posts ago, I reflected on how we really don’t need our stormwater treatment wetlands to receive artificial water supplementation – that we have regional seasonal wetland models to draw from. Here was an early effort of mine to demonstrate that point.
We’d been awarded a project to develop a multi-benefit project between the L.A. River and the 710 Freeway at Imperial Highway. Jurisdictionally, it was a complicated parcel of land – owned by South Gate, but also in the City of Lynwood, with Caltrans and oil company easements.
With the collaboration of ecologist Verna Jigour and engineer Mahmoud Vatankhaki, I proposed a seasonal wetland that would divert and infiltrate stormdrain flows from the adjacent neighborhoods. We recommended excavating a basin area, with a seasonal riparian corridor leading from a stormdrain inlet. A clay liner through the riparian corridor and wetland area would prolong the moisture transmitted via stormwater, while alluvial scrub would be suitable and durable in the infiltration area. An overflow would tie into an existing outfall should storms ever provide more than the site could manage. The project included overlooks from the bike path, and a short trail. Upland habitat defined the perimeter and intermediary slopes of the property – the perimeter being bermed up with the excavated soil taken from the wetland areas – to minimize the influence of the 710 freeway, while grasslands plantings would reside over the oil pipeline to maintain access. The plant palette worked with the appropriate species for the available hydrology of the site.
We were initially awarded $2 million in funding to move this into construction – until Caltrans said no. They needed the land for their up-coming widening project. After I left North East Trees, the Rivers and Mountains Conservancy was able to purchase private land nearby and has revived the project on that site with NET – as covered by Joe back in 2008. We’ll have to check in on the progress and report back – hopefully they are demonstrating what can be done with stormwater without drawing from distant aquifers.