Filling the Niches

While our structural practices have barriers to innovation inherited from earlier versions of the Maryland Stormwater Design Manual that would impede adoption of Stockholm's approach to planting trees, the newer Environmental Site Design (ESD) practices appear to be more flexible. In Calvert County, additional flexibility is written into the stormwater ordinance that allows alternative treatment methods to be approved and used, as long as they meet the performance criteria of the Manual.

Photo by Donghee Bae (CC BY-NC-SA 2.0)

Among the ESD practices that lend themselves to inclusion of biochar in their construction are green roofs, reinforced turf, micro-bioretention, rain gardens, landscape infiltration and infiltration berms. The specifications for these practices not only offer biochar niches, but call for the added  performance that biochar so uniquely provides. 

• Green Roofs: the planting media spec calls for "a soil-like mixture," the base gravel layer could also be mixed with biochar, allowing longer roots and even more drought tolerance.
• Reinforced Turf: the spec requires that the turfgrass inside the permeable interlocking concrete pavers be grown on sand or sandy loam, which doesn't exclude the use of biochar to make the grass more resilient against drought and vehicle traffic.
• Micro-bioretention, rain gardens, landscape infiltration and infiltration berms: the spec allows for amendments to the loamy sand or sandy loam to bring pH to within 5.5 to 7.0. Acidic soils in the Coastal Plain could use biochar to raise the pH. The spec also discusses breaking up compaction from construction at the bottom of the bioretention basin. This refracturing step would be a good time to mix biochar into that 12" zone.

These aren't the only ESD practices that offer niche opportunities for biochar. One that might use great quantities of char in gravel niches is Submerged Gravel Wetlands. We just need to identify and quantify the costs and benefits of using that much char. 

At my first U.S. Biochar Initiative symposium, +Chuck Hegberg confided to me that the sector that offered biochar its best shot was not agriculture, but water. That sounded right at the time, but even more so now.

Breakthrough!

Fragipan is one thing, but what about soils that are highly compacted from the top down? This is a problem common in urban landscaping, and not uncommon in parts of suburbia as well. Compaction makes it hard to start and grow plants, including trees, which serve many important functions, especially in cities. The solution is excavation and replacement of the compacted soil with a suitable growing medium.

Photo of urban landscaping by thanh.ha.dang (CC BY-NC-SA 2.0)

In Stockholm, Sweden, one enlightened leader grasped the choice of replacement growing medium as an opportunity to introduce biochar into the mix whenever trees are being planted in civic landscaping projects. Biochar brings many advantages over commonly used peat moss, including its resistance to compaction. The biochar techniques used by Bjorn Embrén, head of landscaping for the city, were developed over decades and have shown stupendous results in the growth rate and survival of trees. The mixes they use include relatively little soil, but massive amounts of various grades of gravel and biochar. Tree roots find the open structure very accommodating.

Embrén's advice to cities who are interested in these techniques is "Dare to try it and you will be convinced!"  What we, in Maryland, must do first is make a few changes to the specifications for growing media in the Stormwater Design Manual, which dictates a loam/sand mix for infiltration devices. Adopting these techniques would make it possible to select from a wider range of vegetation in bioretention and filter devices, as biochar-based filters drain more quickly than those that rely primarily on soil.

At any rate, we shouldn't have to take the full development and test approach to begin adopting these designs - that part has already been done. All we need is a few delegations visiting Stockholm to see how to make them successfully. They can start by reading this manual. It is a bit old and doesn't use the term "biochar." The term they use instead, "structural soil," could have been key to adoption of the changes since it sounds so common sense and familiar.

Biochar to Improve Soil Drainage and Save the Bay

In Maryland, the Environmental Site Design (ESD) standard for water runoff is that it should mimic woods in good condition. This is difficult when impervious surfaces are being added, since the water collected and treated in stormwater management devices must then exceed what would be impeded and filtered if woodlands completely covered the unbuilt portions of the site, i.e. the additional effectiveness required increases with the amount of impervious surface introduced. The Design Manual qualifies the standard to require that it be achieved to the Maximum Extent Practicable (MEP). This is not as big of an escape clause as it may appear, since the manual also includes a checklist that helps determine whether the design process demonstrates a sincere MEP effort.

The idea of using wooded areas as the standard for all sites is very suitable for Maryland, as a glance at Google Earth will show how very wooded our state is. Yet, rumor has it that the next update to the manual will not be so stringent. As it is, the absolute minimum standard already obviates the wooded area criteria, if it turns out to be impractical on any given site. That minimum standard in the eastern part of Maryland is to design stormwater devices to hold an amount based on 1" of rainfall, ensuring that a specified portion of that water volume drains into the ground to recharge the aquifer. I hope they hold to the more rigorous ESD standard because the Chesapeake Bay will flourish if we can insulate it from the effects of our exploits on the land.

Photo by Birgit Speulman (CC BY-NC-SA 2.0)

Deep biochar-soil mixtures in planting beds would be an effective way to improve drainage, thus helping to meet the recharge volume requirement. Wet ponds are preferred to dry ponds, but you get less aquifer recharging since the water drains slowly in a wet pond. What you could do is use biochar to improve drainage of combination pond forebays, possibly allowing smaller overall pond size.

Here in Southern Maryland, we have a lot of Beltsville soils which are typified by a fragipan layer that is practically impenetrable. It may even reform after being broken up. Here again, biochar could help if it could be injected in fragipan layer breaches, preventing it from reforming. For the gardener, this might involve digging with a post hole digger and dropping biochar into smaller holes that have been chiseled through the fragipan. This would improve drainage considerably and, if the biochar was inoculated first and enough added, eventually eliminate the fragipan through microbial action.

Storming and Norming lead to Underperforming

Just from my brief exposure so far, I have concluded that the management of stormwater runoff is typical of our engineered environment in that much effort is put into the design and construction of a device, after which ensues a lifetime of neglect. It's not due to lack of regulation or even oversight, but a lack of attention by owners and a failure of governance. A well constructed stormwater pond can degrade due to erosion, poor control of vegetation, or flowpath blockages and remain that way for years, all the while earning its full TMDL credit, though performing only half as well as it should. The local authorities are loath to penalize or even notify violators of their maintenance obligations out of fear of having a negative economic impact on business. State and federal enforcers are just as remiss.

Now that Environmental Site Design has downscaled the control of stormwater to smaller devices spread throughout a new development site, it will be interesting to see whether things will be better maintained due to aesthetics and scale. Education will be key. Fortunately, the Design Manual spells out the maintenance requirements for each device type.

Here's the type of problems that degrade a stormwater pond. The photo here is from a place I frequent that has not been maintained much for about 5 years. Trees grow on embankments where the roots compromise the dam's ability to hold water. Banks are eroded into the pond, reducing the vegetation inside, causing pooling of water, and reducing the overall pond capacity. Cut trees are left inside the pond, putting more nitrogen into the watershed as they decay. I hope to catalogue many stormwater devices such as this in Calvert County over the coming months and use this in presentations to those who need to know. They will be posted on my newest tab on this blogger site.

The Grass is Always Greener when You Can Sell It

3-inch deep hardwood mulch extends 3-feet
beyond the dripline of our cherry tree

When my Watershed Stewards Academy instructor blithely offered that we should stop cutting our lawn grass for the sake of better nutrient and water retention I wasn't sure if she meant stop entirely or just let it grow longer than normal. I suspect the latter, which would also support the outside-the-box idea proposed by Gene Logsdon to grow fodder crops in lieu of turf. In my case, there is only a small area remaining on my property that would lend itself to grass. I went the conservation landscaping route a year ago and my mowing duties have been minimal since.

I've been thinking of planting grass on the strip remaining in front of my Kentucky fence. I've also been trying to come up with a good guerilla gardening idea for the right-of-way that fronts the forested lot under the power lines running on the far side of my street. Aside from the black raspberry plant I stuck there last week, this just might be the best way to go.

Growing long grass will push the limit on the HOA's rules, but if I'm going to use that grass for fodder, so would keeping a barnyard animal. Until I get to that level, I'm sure there will be someone in my circles who would appreciate the extra feed. It would also serve well as a compost activator.

An Offer You Can't Refuse

Earthworks like swales are ways to direct and slow the flow of surface water, but the low hanging fruit for livestock farmers to reduce nutrient flows into the Bay is installation of riparian buffers. That is, they should build fences to exclude grazing livestock from access to streams. If they want to save on a big fence bill and have an even more helpful result, they should consider rotational grazing. In any case, simple fences that allow wildlife to get through are an important feature.

The Best Management Practice (BMP) with the next highest potential to achieve TMDLs is conservation tillage, which includes no till and minimum till. When you include biochar as a soil amendment (not yet recognized as a BMP, but deserves that distinction), humus formation is accelerated by perhaps a factor of 10. Conservation tillage relies on humus and plants to make up for the absence of artificial soil aeration. As the years go by, such soil-building measures make it possible to reduce fertilizer additions to zero.

Biochar would also be useful just for its filtering ability in such devices as micro bioretention ponds and ditches. Specifications for these includes 2 feet of sandy soil, but a smaller amount of biochar could provide the same drainage and many times the nutrient filtering of the current designs. It would also yield better plant root growth than just sandy soil.

+Paul Stamets used buried burlap sacks loaded with mycelium to filter runoff from his property. It worked so well, it amazed the government inspectors who came to see the results.

These are all examples of how more effective measures are possible, but not promoted by the bureaucracy, since such official prescriptions such as the Maryland Environmental Site Design Manual don't recognize them. As the 2025 deadline for Chesapeake Bay TMDLs approaches too soon for the counties and states to clean up their watersheds, they are going to want to be able to claim the improvements that mycelium and biochar offer over existing practices.

Too Big to Swale

Fortunately (and wittingly) we have avoided major overflow incidents from wastewater treatment plants here in Maryland for the past several years. Easier to overlook (and we have) are nonpoint sources of water pollution, which are classified as agricultural, urban, forest, and rural, i.e. septic systems. We have become pretty wise to containing hazardous materials, but the pollutants that are choking our bays and rivers with algae are everyday elements carried in the water seeping through or running over the land. There are over 500 potential water pollutants managed in various parts of Maryland, but one ubiquitous element, nitrogen, is the major problem nutrient feeding the algae invasion of our tidal waters.

Photo by Neil Williamson (CC BY-SA 2.0)

Agriculture is the largest contributor to nitrogen pollution and likely to remain so for many years. This could be because agriculture has consolidated its operations disproportionately to its proper ecological scale. Farms these days, in spite of their vast acreage, are generally family operations. Driven by globalization, agriculture has become a very competitive industry, so much that Maryland farmers would not settle for local administration of their part of the Total Maximum Daily Load (TMDL). They needed more consistent application of the standards that constitute the nutrient diet for the Bay, so TMDL for agriculture is managed at the state level.

However, it is the counties who are responsible for their reducing all of their nutrient flows (including agriculture) below set targets or risk losing their federal funding for infrastructure. In other words, the counties have accountability, but no authority for the behavior of their agricultural sectors. It should be no surprise that they have to shoot beyond their targets in the other sectors in order to make up for the lack of progress by agriculture. (I only have data from St. Mary's County, but am assuming that this subversion of local authority has the same effect everywhere.)

Am I being unfair to the agristocracy? Don't I realize they are working hard to make sure I don't go to bed hungry? No. If anybody has been unfair to them, it's the drafters of the TMDL limits. If those limits are unrealistic or biased, they should be changed. Until then, I'm sticking with my view that Ag is too big to swale and follow other Best Management Practices (BMP's) in fulfillment of their responsibility to help clean up the Bay.