This is the seventh of a 10-part blog series examining the nature of our local water supply and how to increase the reliability of our supplies now and into the future.
The watershed that drains to the La Jolla ASBS includes beautiful stately homes, dramatic gardens and the quaint streets of the Village. It seems hard to imagine that such an attractive area can be a source of pollution.
And yet it is.
The watershed of the La Jolla ASBS, like any urban watershed, suffers from an abundance of hard surfaces (streets, roof tops, parking lots), aerial deposition of pollutants, over-irrigation of lawns and uncollected pet waste. This means that beneath all the beauty of La Jolla, the same basic water quality problems occur: urban runoff pollution. And it showed in water quality data in runoff from the area and at the coast – monitoring found that concentrations of pollutants like copper, fecal indicator bacteria, dioxins/furans, total PAHs, and turbidity were high enough to be of concern.
To meet the challenge of eliminating discharges to the ASBS, Scripps Institute of Oceanography, University of California San Diego, the City of San Diego Storm Water and San Diego Coastkeeper came up with a plan to protect the ocean and its special treasures. Recently, Coastkeeper and UCSD staff had the pleasure of introducing the jewel in the crown of that plan – four ‘ecology embankments.’ If you are wandering near the Shores, you will notice that there are two large, newly installed landscaped areas.
But don’t be deceived, these are no ordinary gardens.
Beneath the dirt and plants lie a special mixture of soil, plants and beneficial micro-organisms. Urban runoff drains from the surrounding residential and university properties into these areas and gets treated by this special garden. As runoff flows towards the ocean, it will first get filtered and then pass through the special soil mixture that contains important minerals (dolomite, gypsum and perlite) that remove pollutants. Dolomite and gypsum absorb pollutants like metals and phosphorus. Perlite, a volcanic mineral, keeps air and moisture in the soil. This in turn helps beneficial micro-organisms thrive and be ready to filter phosphorus, metals and petroleum pollutants flowing through the soil mixture. The complex soil mixture slows down the runoff, reduces slope erosion and allows for the soil matrix to do its job – absorbing and transforming pollution that may harm organisms dependent on the ASBS.
Water comes out on the beach side cleaner. But wait there is more – the ecology embankment cleverly relies on native and climate-appropriate plants to help do its work. The plants help keep the soil alive and healthy below ground and above ground they provide habitat for other local creatures. The perfect combination of form and function.
Like planets that orbit around a sun, the ecology embankments are surrounded by other smaller but still innovative projects that also help to protect water quality in the ASBS. There are bioswales that collect runoff from parking lots; permeable pavement areas that infiltrate runoff from residential areas near Scripps, and a rain barrel connected to a rain garden that collects and filters runoff from Scripps’ buildings. These rely on the same principles: slowing the flow, letting it soak in and be treated, relying on plants and soils to do the work. All with the same goal – of keeping a special place beautiful.