mitigating stormwater pollution

Spring thunderstorms have unveiled a new problem related to the paving of White Lake Road and ultimately the 'old-fashioned' stormwater infrastructure that was designed along with it. Despite the fact that this section of the Township is elevated, hilly and geologically coarse-textured (sandy/gravelly), the road was designed in the way that it would have been if it were built in the flat lakeplain of Detroit.

Essentially all the water is collected in catch-basins along the continuously curbed edges of the road, and then piped to designated outlets located at low spots along the road where it is released completely untreated and uncontrolled. So that means that when it rains hard, it releases a lot of water. It also means that anything relatively light that happens to be laying in the road gets washed down the drain and into these "release-zones". Image below shows one of the release zones.



One possible solution to this problem would be to perforate the underground piping that carries this water to the drainage outlets. By punching small holes in the pipes, the water that is travelling through the pipes can trickle through the small perforations and into the local sandy soil, reducing the amount of rainwater that is actually released at the drainage outlets. Because our soil is composed mostly of sand and gravel, it can absorb large amounts of rainwater. This not only reduces the amount of polluted water released at the outlets, but also helps recharge our aquifer and keep invasive plant seeds from being washed into sensitive wetlands and other natural areas where they are harder to control.

There's not much that can be done about it now that the road is complete, however the release-zones can be enhanced to help maximize stormwater treatment before it reaches sensitive wetlands. Our corner lot prairie is one of only a couple release zones along White Lake Road. Prior to this spring, the drainage outlet sent stormwater on a straight path downhill to the hardwood swamp complex south of the site. The result was an unnatural looking ditch that polluted the swamp and adjacent vernal ponds with sediment and garbage. Image below shows a vernal pond that is being influenced by sedimentation pollution from excessive stormwater runoff. Vernal ponds are the primary breeding grounds for amphibians. High-quality vernal ponds (those without pollution) are few and far between.



This spring we spent time re-routing the ditch, hoping to slow the water down so that the sediment and other crap can settle out before the water reaches the swamp. The native prairie/savanna flora will help aid in trapping excessive nutrients and sediment as well. We also planted some white pines that will stabilize the soil with their strong roots and provide screening for the adjacent residence. The image below shows part of the newly re-routed ditch (drainage outlet in background). That dirty looking water is running off a paved road.

spring prairie burn

Spring has arrived early this year, giving us great weather for a March burn. On Wednesday, March 24 we burned the newly acquired corner lot prairie remnant. This lot which is a little over an acre, was previously a wooded site until it was cleared in the spring of 2006. After the landowner cleared almost all of the vegetation to build a house, the project went idle and the field went fallow.

A look at historic aerial photos shows that the site was completely free of trees at least from 1940-1963. After that, the land was left to regenerate on its own and thus was full of fire sensitive vegetation (elms, red cedars, maples, dogwoods). Historic vegetation maps from MNFI indicate that black oak barrens (oak savannas) once covered the area and the remnant vegetation that we have observed over the past four years has supported that theory.

Surprisingly, this site has produced a variety of native wildflowers since it was cleared four years ago which means that it most likely wasn't tilled during the farming era (1850-1960). Sites like these that were not tilled due to soggy/poor soils or irregular topography were likely used for pastures and could potentially be high-quality prairie or savanna remnants.

Our site slopes to the south from White Lake Road at the north and Highland Hills Drive to the east. Interesting about the site is that it ranges from dry-mesic at the north to wet-mesic at the south where it borders a larger hardwood-swamp complex. On the day of our burn, the weather was relatively warm (about 50F), low relative humidity (about 30%) and no wind which made the burn nice and slow which is what we wanted due to the fact that this site probably hasn't been burned for at least 50 years (most likely much, much longer). The slow burn really cooks the invasive brush and helps to consume as much fuel as possible, waking as much of the native seedbed as possible. It will be an interesting first growing season to see how the native flora responds.

Our next duty will be to remove and treat all the invasive brush, and monitor for other aggressive exotic species throughout the growing season.

fall prairie burn

Following a fairly cold October, an indian summer has arrived giving us the unique weather conditions conducive to a fall burn. On Sunday November 8th, with help from the local fire department we burned the half acre roadside prairie. In a previous post I talked about an experimental patch of the roadside prairie that I was working on in the spring of 2008. The experiment included removing the existing cool-season vegetation with a single glyphosate treatment and then burning the dead thatch to expose a clean seedbed for native prairie seeding. All this was done in the late spring as to maximize the eradication of newly emerging exotic species as well as expedite germination of the warm-season plants. As of now this has been a successful strategy. In our roadside prairie the plan is to burn the accumulated dead thatch in the fall, seed all cold moist stratification required seeds in early winter, glyphosate early emerging cool-season non-natives in late March of 2010, and plant warm-season grasses in late April/early May 2010. See photos...