Clueless Commissioners

Hugelkultur may not be in the Maryland Stormwater Design Manual, but it doesn't matter for the majority of properties. If a development activity doesn't disturb more than 5,000 square feet of land, the Manual isn't applicable. Most developed properties under private ownership are not going to build more large surfaces or structures, they just get landscaped, so we can do lots of things not discussed in the Manual that will contribute to cleaning up the watershed.

Some locations are still subject to local restrictions; critical areas, for instance. There are many homes in Southern Maryland located in critical areas, i.e. within 1,000 feet of a tidal waterbody. They are critical for the obvious reason that their proximity to the water makes them, by far, the major potential contributors to water pollution. Critical area buffers are therefore, the primary element of watershed protection that should be enforced everywhere.

Violators of critical area rules are sometimes fined when they are reported by neighbors or passersby, but there could be reinforcement of the rules by a more systematic monitoring effort to identify those who bypass the permitting process or don't follow requirements when they develop their waterfront properties. One such effort was proposed by our local Watershed Restoration Specialist that would have entailed making observations of properties via boat and reporting concerns to homeowners and authorities, if necessary. The knee-jerk rejection of said proposal by a St. Mary's County commissioner elicited the rejoinder,"Why Mr. Commissioner? What are you doing illegal on your property?"

Clueless in Tarcoles by Carol Blyberg  (CC BY-NC 2.0)

I hope someone does finger that particular politician and that he ends up paying in full for whatever he is trying to hide. Meanwhile, in Calvert County, Evan Slaughenhoupt, has raised the ire of environmentally conscious citizens by his favoring of Dominion with their white elephant LNG plant construction. He also seems to favor opening the gates wider in the county to land development, with all of the lovely environmental consequences, one of which is the failing D grade given to the Patuxent River on the latest Chesapeake Bay Report Card.

Charcoalkultur

Infiltration berms belong at the public works level, but a comparable practice for us masses is hugelkultur. I attended a talk last year at the Mother Earth News fair comparing biochar to hugelkultur and discovered that hugelkultur is generally easier and less chancy than making and applying biochar. Yet, a hugelkultur bed will not be as long-lived as one with a load of biochar.

Hugelkultur is the practice of piling soil and organic material on top of a bunch of logs and sticks to form a mound (mainly on contour) which can capture runoff in order to grow plants like a super high raised bed. +paul wheaton published a DVD about it and  +Sepp Holzer put some good instructions on Paul's richsoil website.

I've been using hugelkultur to augment swales in order to reduce erosion on the back slope of my property. My previous post about infiltration berms brought me to consider hugelkultur not as an alternative to biochar, but as another opportunity to put biochar to good use. Filling the gaps with biochar (or some percentage thereof) while building a hugelkultur bed is one way. Biochar could also be applied in areas where there is a need for extra moisture.

Such was the case with my wife's hydrangea which she wanted planted in a sloped area that normally would not stay moist enough for this plant. Yet, there is a roof downspout nearby which spills out onto the slope (via a splash plate) once the rain barrel fills up. I built a quasi-hugelkultur bed to direct the overflow to the hydrangea and loaded the outlet with unground biochar in order to slow the flow of water and hold it close to the plant.

There is enough of a dam behind the biochar to keep it from being washed away. Over time the biochar will break down into small particles and leach into the soil where it can do even more good.

I can see using biochar in a similar fashion on the uphill toe of a hugelkultur bed in order to reduce the tendency of the toe to erode where runoff sheetflow meets the mound. For highly steep slopes (> 25%), a deep swale on the uphill side of the hugelkultur mound containing some percentage of biochar could serve the same purpose.

Swales are an approved ESD practice in the Maryland Stormwater Manual. Hugelkultur beds aren't, but there may be enough latitude in the specs and descriptions that it would fit without requesting special approval. Beyond these practices, terracing is the next step for reducing runoff on steep slopes. For that, heavy equipment is needed, so it's better in most cases to think in terms of swales and mounds.

Filling the Berm

Biochar is well suited to Environmental Site Design (ESD) for stormwater management applications. Its ability to absorb up to six times its weight in water and its long drying time can be used in slowing down runoff to maintain discharge timing while increasing infiltration and evapotranspiration.

Many ESD standard practices include a gravel underlayment to promote drainage. Some of those same ESD practices do not contribute sufficiently to meeting the Channel Protection Volume (Cpv) requirement, i.e. the amount of water that is allowed to run off from a 24-hour one year storm (that is, the average of the largest 24-hour storms historically occurring in an area each year). Since Cpv is sometimes difficult to meet with ESD alone, traditional structural practices must sometimes augment the more distributed ESD practices.

One of the practices that does not contribute to Cpv is infiltration berms. These are long mounds

built orthogonally to the flow of runoff. They consist of 6" of topsoil over an aggregate core. If, like the Stockholm tree planters, we were to load the gaps in the aggregate with biochar, that much more channel protection volume could be earned based on the additional water holding capacity of the biochar.

Of the other practices that already contribute to the channel protection volume, a thick layer of unground biochar between the soil and the aggregate or gravel underneath would help prevent clay particles from blocking the drain, contributing thereby to a more sustainable solution.

Since these two modifications deviate from the specifications in the Maryland Stormwater Design Manual, special review and approval of the innovations would be required at the county and/or state level. MARVALUS Engineering may be the one to request approval of these innovative practices and then earn royalties on their application. Developers and owners probably wouldn't mind paying a small fee along with the price of using biochar if it saves them the expense and real estate of added structural devices or maintenance of the aggregate layer.

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.