The first Filterra unit was installed almost a decade ago. Filterra started in the Virginia/Maryland area of the county to address the pollutant removal requirements of the Chesapeake Bay Act. The units have both comprehensive field and laboratory testing. Filterra units were tested in accordance with the TARP protocol.
About 18 months ago Filterra branched out to California to help promote Low Impact Development (LID) and increase public awareness about stormwater pollution. Let me know if you would like to visit some of the sites in the Bay Area. I also am available to give presentations on Filterra to LA’s, Cities, and Engineers.
Clay don't hate too much on Filterra. I used to feel very similar. My strongest concerns were mainly with the aesthetics of the unit, specifically the concrete exposed on the surface and the fact that the plant material had to be either a shrub or flowering ornamental tree. I was also, originally, under the impression that every 5 years or so these units required major maintenance, including the replacement of the filter soil media and plant material.
All of these concerns were recently laid to rest for me though. Back in June I attended a BMP Maintenance Seminar and met with representatives from Filterra. I witnessed first-hand a full maintenance routine for the system. Filterra requires very minimal and infrequent maintenance. All that is required is to twice a year open the top grate, which has been hiding all of the litter and debris collected, remove and dispose of all litter, debris and top 2 inches of mulch, and then replace the top 2 inches of mulch. My original impression of having to replace the filter media and plant material every 5 years was apparently inaccurate. Filterra assured us that the only maintenance required is the process which I just described. I think that is a bit ambitious and believe that these systems probably have a similar life span to that of typical Bioretention, which should last approximately 20-30 years.
My aesthetic concern regarding the concrete being exposed on the surface is no longer an issue since Filterra has just recently released a new recessed unit. It is very similar to how a paver tray might be use over a manhole or utility vault, where now you can surround your tree grate with pavers, mulch, or even lawn. I have attached the Recessed Unit cut-sheet.
Filterra has also just recently released a larger unit to finally accommodate a street tree application. The unit also has concrete knock-out locations on 3 walls of the units, which will allow for root connects from the unit to adjacent soil or structural soil. I have also attached this cut sheet and their recommended street tree list.
Overall I've changed my point of view on the Filterra system and feel that in the right application this can be a very successful tool.
These improvements do make them a little bit more appealing but I still think that they look like weeds growing out of a storm drain. I dont understand why they need to have the grate over top of the unit. Im sure it has some function but I think they have a long way to go before I will promote their use from an aesthetic standpoint.
If they are back of house or in large commercial parking lots then i think they are fine but we have had engineers place these things in some of our more Designerly projects (if that is even a word) and they are really out of place.
I'm usually not a big fan of tree grates, however I actually think that the grate does provide a very important function is a system like this. In any curbside Bioretention system you will have to manage the gross pollutants that will inevitably build up in the system, i.e. cups, wrappers, other litter.... In an exposed system you will see all of this debris on the surface throughout your plant material. The grate on the filterra hides this debris and litter until you open the grate and remove it twice a year. This also reduces your maintenance needs to twice a year as opposed to the continuous maintenance you will need with an exposed system.
So I would actually say that this application would be appropriate for any urban environment where you are likely to collect litter, especially situations such as back of house or large commercial parking lots.