Yesterday was a great day for our little wetland! Starting in the morning, a few of us rambled over to the north shore on a plant foraging mission. From a coastal flat near a small stream we carefully divided several cinquefoil plants, also called ‘silverweed’ (Potentilla anserina), the roots of which are a highly regarded food source (!)
We also got 2 plantain-like plants called ‘sea plantain’ (Plantago maritima), which is also considered an important food source. (Remember the wetland is contaminated and should not be eaten from)
We also got several unidentified rushes, and some cattail (Typha latifolia). After a quick stop at Quest and a fun food distribution mission, we got ready to work party in the Wetland.
Some of us started by pulling out all the garbage, which seems to be layered in differed sediments and degrees of degradation throughout the wetland’s soil (as well as in hefty piles on top of it). Some of the soft plastics were really hard to separate from plant roots, which had literally grown right through the plastic. The hard plastics that had been around for a few years were difficult to handle, breaking into many small pieces at the slightest provocation. We also found: boots, radios, old umbrellas, many different rotted wires, an old metal plate from a diesel tank, and many other ‘treasures.’
Others went to gather cardboard, which we would use to sheet mulch an area around the standing water in the wetland. The idea with the cardboard is that it will make it harder for the Himalayan Blackberry and Canary Grass to grow back. We also actively attacked the blackberry roots to help with this.
As you can see, once we put the cardboard down, we covered it with a mixture of wood chips and city soil. Before laying all the cardboard, we worked to dig out a part of the wetland, in order to make part of it deeper. The hope here is that a deeper hole will hold water for longer, leaving our wetland wet for more months in the summer, when it tends to dry out. We also worked to make the slope of the wetland less severe. A slow, gradual slope means that there will be more wet area in the wetland. In essence, we brought high spots down slightly, in the hope of making a bit more wetland.
After covering all the cardboard with soil and wood chips, a few folks went foraging for some more plants that could be divided from nearby, and found 2 different rushes as well as a Red Osier Dogwood (Cornus serecia). Along with the plants we foraged in the morning, as well as the lovely Snow Berry Adam propagated, we planted everything into the wetland.
Finally, we installed the sweet new sign we made!
We’ve been featured in the June edition of Megaphone – Vancouver’s street paper. Check it out!
Filed under: Pod updates | Tags: bioremediation, guerilla gardening, wetlands
We’ve been poking away at our little urban wetland, getting to know the site and developing strategies for its transformation. To date, we have: removed a section of chain link fencing containing it, cut many large Himalayan Blackberry canes to the ground, removed 250 kg of waste from the site, pulled even more waste out of the wetland and piled it on the side of the cul-de-sac, planted a few Hardhack and Snow Berry shrubs, and consulted with local bio-remediation firms and wetland restoration groups (notably Western Seed and Erosion and the BC Wetlands Institute).
We’ve come to realize that completely remediating the soil of all toxins is likely impossible. The proximity of many CN rails with their creosote soaked ties, and the position of our site at a low point directly adjacent, means that the polycyclic aromatic hydrocarbons (PAHs) common in creosote have likely seeped into our wetland. The guide Brownfields to Greenfields: A Field Guide to Phytoremediation says “PAHs are over 100 chemicals, formed during the incomplete burning of many organic substances.” PAHs have been shown to damage red blood cells, leading to anemia. They also suppress the immune system and are known to cause cancer.
There are, luckily, 3 easily grown native plants that will degrade PAHs in the soil. White Clover (Trifolium repens), Tall Fescue (Festuca arundinacea), and Switch Grass (Panicum virgatum) naturally take up and break down PAHs “through the release of enzymes and metabolic processes such as photosynthetic oxidation and reduction. In this process organic pollutants are degraded and incorporated into the plant or broken down in the soil.” Red Mulberry (Morus rubra) and Hybrid Poplar (Populus deltoides x P. Nigra) are also able to phyto-degrade PAHs. We have not received results from soil testing and so are not sure what other contaminants may be in our wetland.
The plan for now is to invigorate the wetland nature of this site, by planting a variety of native plants that like wet conditions. In the coming weeks, we will purchase some plants from local nurseries and acquire many more through respectful seed gathering and division from healthy local wetlands and riparian areas. We will also be laying down a permeable barrier of burlap in an attempt to control the invasive Himalayan Blackberry on site. We hope to cover this layer with an inoculated soil mixture, designed to introduce beneficial bacteria and fungi, to further bio-degrade soil contaminants. We are also going to excavate a small area at the center of the wetland, to expose water for more of the season. We’ve found that in the late spring, water slips just below the soil level. Digging down a foot or two will leave this water exposed to the surface and provide an important water source for native insects and birds.
Here is a partial list of local plants we hope to gather (along with the aforementioned phyto-degraders): Skunk Cabbage (Lysichiton americanum), Cattail (Typha latifolia), Red Osier Dogwood (Cornus stolonifera), Willow (Salix spp.), Hardhack (Spiraea douglasii), Sweet Gale (Myrica gale), Pacific Crab Apple (Malus fusca), Paper Birch (Betula papyrifera), Black Cottonwood (Populus balsamifera), Red Alder (Alnus rubra).
radicle beets 