The one that wasn't

My other major early project at TAMS was the proposed South Suburban Airport near Chicago. Beginning in 1990, we analyzed five alternative search areas ranging up to 18,000 acres in size; full biological inventories of each, over a two and a half year period. While two of the sites were almost entirely agricultural, one included some woodlands of moderate to good quality, and two, the Gary Indiana and Lake Calumet IL sites, included remnants of significant natural communities such as nearshore dune and swale, mesic prairie, and marsh. A lot of experience that would later prove to be valuable came out of this project, not to mention the world-class team I was fortunate enough to work with for those first seven years.

After some political contortions far too complex to describe here, eventually the Peotone site was chosen. It was one of the greenfield, or  agricultural sites and the vast majority of it was in row crops. All of the headwater streams that crossed it were channelized. And therein I found an opportunity.

One of the streams was Exline Slough. Today it's a straight ditch. Where it crosses Beecher-Peotone Road it's as much as 10 feet deep. Each year we sampled fish from within an earthen canyon, unable to see over the sides for the entire 200-meter sampling reach. It had been dredged, probably before 1910, and the rich black dirt sidecast into low irregular levees on either side. it was located just southeast of the proposed airport, well within the noise contours where we'd need to create unpopulated buffer areas.

In spite of the massive alteration we got above average fish assemblages there most years, with IBI scores around 44 if I recall correctly. There was at least one fishkill associated with nutrient over-enrichment, followed by fairly rapid recovery. So it was a reasonably diverse if sometimes unstable assemblage.

The obvious clue came from the name; it had been called a slough for a reason. Standing atop the bank, one could see an elongated basin slowly rising off to either side to the surrounding Valparaiso Moraine.  A glance at a topographic map confirmed it; there was a quarter-mile wide abandoned floodway perched 10 feet above the modern elevation of the streambed. Finally, a look at the 1830's GLO survey notes and map provided additional confirmation. At that time, prior to channelization, Exline Slough had been a quarter-mile wide flowing marsh with a very narrow open channel in the center. It had been like this for miles, from the headwaters all the way to the edge of the higher gradient sloping down to the post-glacial Kankakee Torrent valley.

Exline Slough, we determined, originated from a series of drain tile outlets about a mile and a half north of our sample reach. Here a south facing shallow basin climbed gradually to the divide between the Mississippi River drainage... Exline Slough into the Kankakee River, to the Illinois, and finally to the Mississippi; and the Lake Michigan drainage, via Plum Creek and Thorn Creek and into the Calumet. On the north side of this divide, only a few hundred meters from the Exline Slough drain tiles, we discovered a previously unknown 30-acre prairie set well in from the section roads. It had been heavily grazed by horses, but was restorable.

We quickly developed a concept to grade several miles of Exline Slough back to something like original elevations, re-establishing the wide, shallow and slowly flowing marsh that had once been there. At least two section road crossings would have been removed entirely. The drain tiles would have been removed. The prairie would have anchored the northern end.

Unfortunately, two things got in the way. Most importantly, the FAA issued published guidance restricting wetland mitigation within 10,000 feet of an active runway, for wildlife hazard reasons. The northern part of our site fell within this radius, effectively killing it as potential mitigation. Also, the proposed airport bogged down in Illinois politics. It still hasn't been built almost 20 years later, although land for the first runway (of six originally proposed) and a small terminal has been acquired.

Still, it's worth sharing the concept because there are other places in the Midwestern and Eastern U.S. where it's applicable. Structurally it's obvious enough. What made it so possible though was the existence of a published analog, a reference site a century removed in time. The photo below is from Sherff (1914), based on work done in the Skokie Marsh north of Chicago in 1910-1911 and published by the State of Illinois.

The photo was taken west of Glencoe. Note the relatively narrow open channel, choked with submerged vegetation, and the bordering bands of what appear to be bulrush, dropping into a marsh and wet prairie complex with lower vegetation to either side. Topographically this marsh would have been similar to the one at Exline Slough before both were extensively modified. There's an extensive vegetation list included in the published article and while the two site are perhaps 60 miles apart and they certainly weren't identical, they would have had much in common. It wouldn't have been hard to develop a planting mix from the available information. There's also a surviving area in Barrington Hills, around Spring Lake and Mud Lake, that's similar in appearance and which could serve as a reference site.

This one wasn't to be. However it's an excellent example of how to use historic information and a bit of temporal imagination to re-establish what once was, when the circumstances allow.

Mid-America

The first mitigation project that I worked on as a consultant was Mid-America Airport. When I joined TAMS Consultants in 1990, the very first thing that I was tasked with was writing an Environmental Assessment on this project, and especially conducting an alternatives analysis. This brought me to some fascinating locations in St. Clair, Madison, and Monroe Counties, Illinois (not far from St. Louis MO) in the dead of winter.

The ultimate project site was at first known as the Scott AFB Joint-Use Project, because this ended up being the first joint use airport in the U.S. (there had been earlier examples in Europe). Scott AFB is on the west side of Silver Creek, and the concept was to build a new runway, taxiway, and terminal east of the river. Both the military and civilian sides would share existing maintenance and control tower facilities, reducing both costs and environmental impacts. It also kept Scott AFB off the base closure list, thus building a lot of local economic support.

Even with some very creative designing to minimize impacts, the need for a connecting taxiway across the 1.5-mile wide floodplain associated with Silver Creek meant some pretty substantial impacts to second-growth floodplain forest which qualified as jurisdictional wetland. To this day it's the largest mitigation project that I've actually helped build, by about double: We mitigated 100 acres of fill at a 2:1 ratio, or 200 acres of mostly bottomland hardwood forest re-establishment.

The concept was fairly simple. The existing floodplain forest, while vast, was badly fragmented. The forest had been repeatedly cut and most of it was from 30 to 50 years old; one small section was about 90 years old and beginning to show some mature habitat structure, but mostly we were working with even age stands dominated by cottonwood, silver maple, box elder, and green ash. Agricultural fields had been cleared within the forest and leveed off. In wet years they simply flooded from the inside, and most fields produced crops only about half the time. Most of the fields were small, although the largest one, and the cornerstone of our mitigation concept, was about 70 acres. The general idea was to breach the low levees to restore connectivity to the river and the floodplain, and then to plant trees. We also jump started things by salvaging some of the larger trees cut in the taxiway area, and placing them upright in the largest mitigation site as snags. The idea was to get structure more typical of mature forests in place right away. Reducing fragmentation was a primary goal, and with the help of USACE-WES and USFWS we applied a then draft Bottomland Hardwood Forest Community HSI model to document existing and predict future conditions.

We also took an opportunity to re-meander the river and an associated tributary. The northwest end of the new runway required relocating part of Silver Creek, in a reach just south of Interstate 64 where it had been straightened and channelized. The new design included sweeping meanders similar to those intact in the southern part of the project site. We planted willow stakes to stabilize the meanders and to encourage formation of a riparian zone, and included some in-channel structure in the design.

Mitigation construction began in October of 1993, and the impact side of the project was built in 1995-1996. Most of the mitigation was completed at the same time, with a Phase 2 area north of I-64 built a few years later to compensate for some impacts that were also delayed.

We experienced heavy flooding in 1997, the same well known Mississippi River events that flooded parts of the St. Louis riverfront and destroyed entire small towns such as Valmeyer (our engineers helped design the relocation of Valmeyer to the top of the bluff). Our new meanders held, although the in channel structure was swept away and replaced with natural woody debris. Then came some very dry summer months. In spite of all this the mitigation held up fairly well. The design was flexible enough to allow for stochasm. It was resilient, a term not much in use yet at that time. That experience has influenced my restoration concepts ever since.

What would we have done differently? The agencies asked for relatively homogenous oak and hickory plantings, and we didn't argue as hard as we should have. In practice the oaks and hickories did pretty well on the somewhat drier terraces, and not well at all on the lowest and wettest areas which grew up instead with willows and other soft mast species. This turned out to be OK, because when I went to the Corps with monitoring results and aerial photos documenting excellent interspersion of habitat structure, we were released from permit conditions for the Phase 1 part of the effort. Everyone, agencies and consultants, learned from the experience. That was in 2005, which was the last time I visited the site; someone else completed the Phase 2 monitoring.

So the only thing I'd really change would be to not waste money by planting hard mast trees in the wettest areas.

We documented increased biodiversity. Fish sampling resulted in mainstem IBI scores returning to just above pre-project levels and tributary IBI scores well above pre-project and into the very good range. Amphibian species richness increased slightly (I published this data a few years later), and state-listed red-shouldered hawks nested in our snags the first year.

This photo shows the largest mitigation unit as of 2013; maybe someday I'll return to the site again, but that will require coordination with and permission from airport security. So for now I'll rely on remote sensing. That's Silver Creek on the left, and some of the more mature remaining forest is on the left of the river. The mitigation site (about the center third of the photo, from the river to that vertical green slash within the brown just right of center, that's a ditch which bounded one side of the site) continues to show good interspersion, although it looks like there's been some recent flooding. The pond just left of center was excavated as part of the project to mimic an oxbox pond. The small more densely wooded area in the top right is a pre-project stand of then very young trees, about 20 years older than the mitigation plantings. The pale green area in the very bottom center is the wettest part of this site, and is unlikely ever to support more than a few large trees.

There was one other lesson, one I don't have an answer to. Some of the suburbs nearby, especially along the interstate corridor, sprawled post-project. Where three towns meet, retail developers played the towns off against each to get concessions. The result was shopping malls with no pedestrian friendly features, and only the bare minimum of stormwater retention. They represent the worst of suburban sprawl and car culture. Those places were beyond our planning control, and yet in the long term they will affect local water quality as well as quality of life. It's a policy dilemma that's larger than any one project.

24 years of restoration

The next series of posts will focus on the various mitigation projects I've worked on since 1990. While all of these qualify as habitat restoration at some level, the things they have in common are that I worked on them in my consulting role, and most (but not all) were intended to mitigate for some project-related impact. Perhaps later I'll take a look at some of the pure restoration projects I've been involved in over the years, however there are some important lessons to be learned from the mitigation projects.

These follow only a very rough timeline. The larger projects lasted for years, in one case for 14 years. Smaller projects came and went in the midst of these. Some were designed and built quickly, others were built only several years after design. So there's some jumping back and forth within a very roughly older to newer progression.