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Wednesday, September 26, 2012

Stormwater Pond Gets Help Getting More Natural

The Back Story
Let me give you the back story first.  Our township had this ghastly looking, neatly manicured stormwater retention basin that was dedicated to the township by a developer after they finished building the adjacent Penn's Meadow residential subdivision.  The township mowed the basin every week (because any grass growing higher than 1.5 inches is an abomination in suburbia).  The photo below shows the Penn's Meadow basin as it used to appear, with its long concrete spillways leading to an outlet.  It was nothing more than a shortly-mowed lawn inside of a big berm.  There were no plants other than the grass, and the only birds you’d see were occasional Canada geese when the basin was holding water after a storm.

The stormwater basin as it looked until two years ago.

Two years ago, with the help of some grant money, our township and the county soil conservation district teamed up to do a retrofit of the basin.  The retrofitted basin became a model of stormwater Best Management Practices (BMPs).  BMPs, for the layperson, are ways of managing stormwater runoff to limit how much runoff reaches the nearest surface water body.  Stormwater runoff carries contaminants washing off of road surfaces, as well as sediment that messes with all varieties of aquatic critters.  Meadows were planted around the area, resulting in the entire area now functioning as a fairly well balanced ecosystem that supports a diversity of plants, birds, and insects.  The location is already becoming popular with local birdwatchers.

The retrofit used three different BMP methods for each of the three stormwater inlets that discharge into it.  There is a vegetated low-flow channel, a constructed treatment wetland, and a forebay with a sand filter.  All three of these individual BMPs empty into a wet pond.  Being the enviro-geek that I am, I've stood here in heavy rain to watch the stormwater moving through each of the three BMPs and into the wet pond (that should not be surprising to anyone who really knows me, though).  Credit for the BMP design goes to Bill Erdman's crew over at Keystone Consulting Engineers of Wescosville, PA.  

The entire 6.5 acres of this open space area was not required for the stormwater management facility.  Therefore, the northern 2.5 acres was planted as an upland area with 150 native trees and shrubs.  A check on the trees earlier this summer by the Pennsylvania district forester for our region found that an impressive 75 percent of those trees have survived their first two winters.
The Current Part of the Story
This past Saturday, our township’s Environmental Advisory Council (EAC) joined forces with our local Boy Scout Troop (Troop 131 of Wescosville, PA) to accomplish our goal of planting over 360 aquatic and wetland plants in and around the Penn’s Meadow pond.  Twenty-four boy scouts and 17 parents of scouts got down and dirty, and occasionally wet, while planting the native wetland plants that will provide cover and shelter for some of the wildlife that passes through or resides at the location.  In addition to EAC members, the scouts, and their parents, the work crew also included seven local residents who heard about the workday on Facebook and wanted to be a part of it.

We planted five different native plant species:  swamp rose mallow, common spike rush, longhair sedge, green arrow arum, and grassy arrowhead.  All five species are wetland plants that thrive being inundated by standing water anywhere from two weeks per year to year-round, depending on the species.  These new plants will increase the biological diversity of this little ecosystem even further and encourage even more insects, birds, and amphibians to frequent the pond.

While the planting activities were underway, the volunteers who did not want to get wet or muddy went about weeding the mulched pathways that criss cross the roughly 6.5-acre site.  In addition to cleaning up weeds on the pathways, these non-muddy volunteers also patrolled the meadow surrounding the pond, pulling invasive plants that compete with native plant species for sunlight, space, and nutrients.

This is what the Penn's Meadow area looked like in July when more of the wildflowers were in bloom.
The Hibernaculum
I've wanted to build a hibernaculum for amphibians at the Penn's Meadow site for a while.  A hibernaculum, as its root word implies, is a place for critters to hibernate safely for the winter.   Not that we've actually spotted any amphibians in or around the pond yet, but they might be there.  Plus, one of the township staff offered to transplant some frog egg masses from his home pond to the Penn's Meadow pond as soon as they start laying their eggs in a couple weeks.  So even if our hibernaculum doesn't get much use this winter, it will definitely get used next winter.

The ingredients:  logs and mulch mixed with sand.
After all of the plants were planted on Saturday, I rounded up one of the weeding crews to help me build a hibernaculum near the pond.  I've never built a hibernaculum before, but I've looked up various plans.  They can be built using rocks or logs.  Rather than try to find someone to deliver a quarter ton of cobble-sized rocks to our site and then move them to our hibernaculum hole, I chose to grab an armful of firewood that I already had cut for my fire pit at home. 

The series of photos below document the creation of our hibernaculum.  The key idea here is that the logs should be stacked in the hole so that they are leaning into the prevailing wind direction at about 45 degrees.  That way the exposed ends of the logs (the entrance) will be downwind.  We dug our hole to about two feet deep, even though our frost line in this area is about 3 feet deep.  When we were finished stacking the logs and filling the gaps with the sand mixture, we mounded the excavated soil on top of the logs and sand for a finished height above grade of just over one foot (2 feet below and 1 foot above ground). 

It starts with a hole in the ground in close proximity to the pond.
This one measured about 2' x 3' by 2 feet deep.

This is what 200 pounds of sand mixed with two 5-gallon buckets of mulch looks like.  This mixture was used for the spaces between and around the logs, plus about 3 inches in the bottom of the hole under the logs.

Add the sand/mulch mixture to the downwind side of the hole to support the logs.  The logs are stacked at a 45-degree angle with the exposed ends pointing downwind from the prevailing wind direction.  Cover all but the exposed ends of the logs with more of the sand/mulch mixture, then top with the soil that was excavated.

The completed hibernaculum.  Soil we had doug out was mounded on top of the logs for added insulation, and only the ends of the logs are exposed for the entrance.  Complete, except for seeding the bare soil on top to try to beat invasive plant seeds from getting there first.

The Moral of the Story
The take home message here is that no major or minor conservation project can get off the ground without a lot of people from different backgrounds and with different expertise coming together for a common cause.  Doing the retrofit two years ago to naturalize the township's stormwater basin required a lot of coordination between the county conservation district, the design engineer, a local excavator, elected officials, and township staff.  And many volunteer hours.  The former watershed specialist from the Lehigh County Conservation District, Rebecca Kennedy, was the driving force behind making this retrofit a reality, and former township Commissioner Deana Zosky was only half a step behind Rebecca in herding all of the cats that had to be herded to make this project happen.  It all starts with one or two people sharing a common vision of what could be.

Likewise, last week's wetland planting, weeding, and hibernaculum building effort at Penn's Meadow was successful because we were able to pull together a great mix of enthusiastic people.  We started with a handful of EAC members who are very familiar with the naturalized stormwater pond; a few local residents who are excited about the evolution of a formerly barren stormwater basin into an ecologically diverse, naturalized pond; and a bunch of local boy scouts who were genuinely enthused about doing a local conservation project.  Individually, none of these groups would have had the numbers, the muscle, or the expertise to accomplish the day's events alone.  Grassroots conservation happens just like grass roots happen.  By branching out and digging in.

And at the end of the day, when you've finished working on your conservation project, be sure to take your family for a nice, little nature walk.  This photo was taken later that day at another of the township's open space properties, Camp Olympic Park.