Suisun Marsh

In 1993 I was asked to take over a California wetland mitigation project. The woman who had barely started it had transferred out from one of our east coast offices, but had clashed with the engineer who ran our Concord office. After only a few months and with one completed project in the northeast corner of the state, she had left for an opportunity in Atlanta. As the only other ecologist in the company with previous California experience, I was asked to take over the permitting and mitigation design, and as a result I worked about half time from Concord over the next year or two on this and another project.

The project involved the widening of SR 12 through Suisun City, in Solano County. The decision had already been made to mitigate the filling of a roadside ditch through wetland re-establishment on the adjacent Hill Sough Wildlife Area, and an agreement to that effect had been negotiated with California Department of Fish and Game. The outlines of the concept were in place; the deep, straight ditch would be replaced by a meandering brackish and tidal slough. There would be about nine acres of adjacent seasonal wetlands, and the mitigation site would be separated from the Wildlife Area by a dike. We weren't happy about this last part, but CDFG insisted upon it.

My role was to help work out the final design details and then to obtain the permits. We brought out a hydrologist and designed a weir to keep a small area of fresh water below the outfall (the upper segment of the stream was underground in a  residential neighborhood) as pond turtle habitat. I modified the elevations and some of the channel contours to minimize "islands" of upland that might serve as weed traps. I worked with a local landscape architect to develop a planting plan, after first educating him on why non-native ornamentals were not an option (he learned quickly and ultimately did well).

Then I got the permits. These were almost too easy. The Corps of Engineers was quite cooperative. There were no issues with the dreaded Bay Conservation and Development Commission, it was the first time I'd dealt with them and I didn't know any better. Possibly stopping by their San Francisco office to meet staff and ask to use some of their publications for research helped.

The project was built in the fall of 1994, and I visited every couple of years for a while. At first it was fairly successful. We met the permit requirements at the end of year five (Caltrans did the monitoring, I visited on my own time).

Then they walked away. After 1999, no one did anything to manage the site. After another 10 years, the trail had cracks in the pavement and the interpretive signs were too faded to read.

The interior of the site still looked pretty good, still met performance criteria. This included the new channel and the nine acre seasonal wetland, so actually most of the site looked pretty good. The problem was the upland buffer between the channel and the road. It was pretty weedy. Only an acre or two, but still.

I learned the importance of long-term management. I also learned not to place mitigation sites contiguous with roads, if at all possible. It hadn't been a choice in this case, we'd pressed as far into the Wildlife Area as we realistically could.

Overall, the mitigation site is a big improvement over pre-project conditions. I'd always like to see better, however I've got to acknowledge that we met the stated goals even without long-term management. We'd provided additional habitat for two listed species known on the adjacent lands, Suisun shrew and salt marsh harvest mouse. We'd eliminated habitat for non-native gobies documented in the ditch before the project. We'd removed a considerable amount of compacted fill which had encroached into the margin of Suisun Marsh, the largest estuary in the western U.S. And I'd gained California project and permitting experience. More on that in the next post.

Although I disliked working in the suburban car culture that is Concord… it was faster to get in the car to go to lunch than to walk across the six lane street, which was dangerous… I did very much enjoy the project area. Often I'd drive down to the end of Hill Slough Road, past the golden treeless hills and the endless marshes. In the evenings I'd eat in Fairfield or drive over to Berkeley and browse bookstores after dinner. One weekend I drove up to Tioga Pass, making snowballs at 11,000 feet after crossing the baking 100-degree central valley. I took full advantage of the opportunity to expand on my earlier experiences in Southern California, San Francisco, and Mendocino County.

snakes

Spring is approaching, and with it groundbreaking on a variety of projects. I'm beginning to get requests to visit sites to complete required pre-construction surveys.

One of these sites is in the Sacramento Valley, and it's potential giant garter snake (Thamnophis gigas) habitat. We're not certain if the species actually occurs in the project area, which is currently in rice production, and the nearest documented locality is about six miles away. But it might be there, and as so often happens, it's more efficient to assume presence and mitigate.

There's some controversy about the habitat needs of the species. The agencies generally consider rice fields to be habitat, and it's true that snakes do sometimes enter them. Rice fields are wet in summer, and thus they mimic the presettlement wetlands of parts of the Central Valley which were once fed by now diverted Sierra snowmelt well into the summer. Rice fields also harbor tadpoles... Pacific tree frogs or introduced bullfrogs... and as the fields are drained in late summer, snakes may forage in the shrinking pools of water if there is more permanent vegetated wetland habitat nearby to provide cover and food in other seasons.

Rice fields are also subject to frequent disturbance, and they can concentrate pesticides and herbicides. They are structurally simple. In my opinion, they're marginal habitat for giant garter snakes, at best. They're used only because so little else exists.

Giant garter snakes persist on some of the National Wildlife Refuges in the area, but these tend to be command-and-control facilities driven by pumps, and managed for waterfowl. They are largely dry in the summer months, and thus they differ considerably from the historic condition. Where more permanent water is present, snakes can do well because vegetation is more structurally diverse and food sources more predictable.

It seems at first glance to be easy to restore the requisite habitat. In practice it may not be so easy, because the water control system is so vast. Yet there are certainly at least some areas where restoration is feasible, and indeed it's been done at a few mitigation banks. Overall though, the lack of imagination is striking, when considering this species.

While I'm out on those sites, I'm going to be looking around, getting a better understanding of the landscape, and of the possibilities.

following through

While I'm working through my current reading material, here are a few thoughts on an older project... one that worked pretty well for a while.

I was still pretty early in my consulting career, and the client... a California state agency... had already developed a mitigation concept. The previous consultant had botched a few things, and one day I got one of those "help" calls from one of our west coast offices. I spent about the next year completing permitting for the project, and making some minor adjustments to the design.

It was one of those things that had to be an improvement, because pre-project it was nothing but a straight-sided ditch with weedy banks. We ultimately restored a gently meandering tidal channel with bordering seasonal wetland and a short interpretive trail. Because it was the first restoration project that I'd worked on and actually seen built, I visited several times over the years to see how it was doing.

Through the five year monitoring program, things went well. The agencies signed off on a "success" and then... nothing. There was, as far as I can tell, no maintenance after that. I'm not even sure if anyone except me has looked at the site since then.

The tidal channel still looks pretty good, as of last summer. The brackish water does a pretty good job of keeping weeds out, so there's a nice bulrush-dominated community lining the channel.

The problem is that the project site borders a busy highway. Predictably, the area between the road and the channel has become pretty weedy. What's perhaps even more disappointing is that the interpretive signs are faded and unreadable, and weeds grow through cracks in the trail.

On the interior half of the site, across the tidal channel from the road, things are much better. I don't have access to the site and have chosen not to climb the fence, but as far as I can tell the seasonal wetland there is working as it was intended to. It's not pristine, but it's not unusually weedy either. That part of the site is contiguous with adjacent public open space, and it's functioning pretty nicely.

Overall, the disappointment is minor. There are a few lessons learned; one is that because no parking was provided for the interpretive trail, no one other than the kids from the adjacent subdivision ever seems to go out there. The local municipality has posted no parking signs along the road (they went in years after project completion), so it's just barely possible to squeeze one small car off the roadside by the trailhead.

I guess the project counts as 75% successful. There was never any stated intent to maintain a pristine native upland community, but the presence of invasives along the roadside is troublesome. The biggest lesson, for me, is that project sponsors can't always be counted on to maintain a mitigation site after the monitoring period, especially when all of the people involved have retired or moved to other jobs.

It's been about 18 years since the permits were issued and the project was built. I intend to revisit the site from time to time, every few years, to watch the trajectory. Never stop learning.