The Chena Slough has been slowly dying since it was cut off from its headwaters during construction of the Moose Creek Dam in the 1970's. Chena Slough is now a roughly 15 mile long channel, its first 3 miles completely clogged with native plants and debris, and the lower 5 miles filled with native plants as well as a new arrival, Elodea.
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| Drawing from Technical Report 06-02 |
Prior to 2010, several local groups were working to increase flow in the Chena Slough to restore its once healthy ecosystem for recreational uses and fish habitat. Several documents available on-line show that various agencies were concerned with the declining health of the Chena Slough and the loss of habitat for fish spawning. Once Elodea was discovered in the Chena Slough in 2010, all talk turned to eradication of this invasive species, with the promary goal of stopping its spread to the Chena, Tanana, and Yukon Rivers.
1. Technical Report 06-02 (Ihlenfeldt, 2006)
In 2006, the Department of Natural Resources issued a report, "RESTORATION OF SLOUGHS IN THE FAIRBANKS NORTH STAR BOROUGH (TANANA RIVER WATERSHED)." In this report, they detailed the cause of decline and problems associated with cutting the flow of water in the Chena Slough from it's once mighty 1000 feet per second (fps) flow down to less than 70fps.
This report identifies a Chena Slough Technical Committee formed in 2000, the committee consisted of:
Alaska Department of Envir onmental Conservation (ADEC)
Alaska Department of Natural Resources (ADNR)
Office of Habitat Management and Permitting (OHMP)
Division of Mining, Land and Water (DMLW)
Alaska Department of Transportation and Public Facilities (ADOT/PF)
Planning Division Chena Slough Neighborhood Committee (CSNC)
Chairman Fairbanks North Star Borough (FNSB)
Planning Department Fairbanks Soil and Water Conservation District (FSWCD)
Mayor of North Pole – Jeff Jacobson
Natural Resources Conservation Services (NRCS)
University of Alaska-Fairbanks (UAF) Fisheries
U.S. Army Corps of Engineers (COE) Regulatory Branch
U.S. Fish and Wildlife Service (USFWS)
Habitat Restoration Division U.S. Geologic Survey (USGS),Water Resource Division
Scant information is now available on the Chena Slough Technical Committee. It's possible they disbanded upon completion of the Persinger Road culvert replacement project in 2013, the last in a series of actions outlined in Technical Report 06-02.
The report outlined the main problems with the slough as seen in 2001, all relating to "fish passage":
- Culverts undersized for the design discharge
- Grade breaks within the culvert barrel creating hydraulic jumps
- Culvert slopes no t matching the channel gradient
- Excessive water surface restriction (flow contraction) at the inlet
- Culverts blocked by debris and/or grates
- Culverts set above the channel thalweg (perched).
This report checks the progress of actions from a 2001 survey:
- Replace culverted crossings with bridges or much larger, correctly placed, depressed culverts that meet proposed width/depth ratio.
- Construct a channel (within the existing channel/floodway) with a width/depth ratio of 20’-30’ wide by 2’-3’ deep, sinuous with intermittent pools, runs, riffles and slack water ponds.
- Create a beaver management program and reduce beaver dams.
- Divert water from Moose Creek to Chena Slough to double the existing discharge (existing summer flows = 70- 90 cfs, winter flows = 40 cfs) to a proposed 140-180 cfs.
- Conduct fish habitat use studies along the length of the slough.
- Continue the recreational and educational use of the slough.
As outlined in this technical report, nearly all of the infrastructure (bridge/culvert) repairs had been completed by 2006 through a series of funding: $374,000 from state grants and $75,000 from the U.S. Fish and Wildlife Service. The work done addressed some pressing issues related to fish passage. The report contains many before and after pictures, such as these pictures of the slough crossing at Hurst Road:
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| Before - Photo from Technical Report 06-02 |
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| After - Photo from Technical Report 06-02 |
The summary of Technical Report 06-02:
"Culverts, beaver dams, poorly installed utility lines and illegally placed fill material are acting as barriers for free flowing water and the movement (“flushing”) of ice and vegetation and unwanted nutrients in many of the sloughs in the FNSB. To achieve agency and community goals, maintain fish habitat and passage, and maintain or increase recreational use of the sloughs, the continued removal of these barriers is necessary."
2. Chena Slough Hydrologic and Hydraulic Analysis for Existing Conditions and Channel Modifications (Hydraulic Mapping and Modeling, 2013)
This report prepared for the Fairbanks Soil and Water Conservation District analyzed the flow of water through the Chena Slough in light of modifications made between 2000 and 2013. Included in this report is a description of the effects of Elodea on water flow.
The purpose of this report was to provide information to land managers that would allow them to make decisions to improve fish habitat and decrease Elodea. To do so, they used four models of improvements in their assessment:
- Replace ALL culverts with bridges
- Dredge a new channel for increased flow
- Remove excess vegetation
- Introduce more water for a "flushing" flow
Flow Characteristics
This report details the flow characteristics of the Chena Slough. The crew conducting surveys installed two flow meters and conducted an extensive elevation survey. The following diagram is very important, though its importance has been overlooked. The Fairbanks Soil and Water Conservation District has expressed an interest in applying Fluridone herbicide to the Chena Slough in a constant drip fashion to keep a concentration of ~50ppm of Fluridone in constant contact with the Elodea.
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| Hydraulic Mapping and Modeling, 2013 |
The elevation of the lower 16,000 feet (3.03 miles) is such that the water level here mirrors that of the Chena River, as discussed in the report:
"The water surface elevation at the confluence varies over time, as flow rates in both the Chena River and the Chena Slough change. As such, the Chena River discharge will affect both the water surface profile and channel velocity of the Chena Slough for a short distance upstream. HEC - RAS analyses show that the effects of lower water conditions (-1 ft) in the Chena River may affect the Chena Slough water surface profile for 12,000 feet or so upstream. Higher water level conditions in the Chena River (+1 ft) may affect the water surface profile upstream to the Peede Road crossing, at River Station 16005 feet. Modeling results upstream of Peede Road are likely not affected by the range of normal flow conditions in the Chena River."
Why is this important? Land managers at the Fairbanks Soil and Water Conservation District have shown an eagerness to apply herbicides in the flowing waters of the slough. These flow characteristics will present a major challenge.
Even the areas not effected by the Chena's rise and fall will still see large fluctuations, as noted here in the report when a beaver blocked a culvert, causing a water to rise dramatically:
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| Adapted from Hydraulic Mapping and Modeling, 2013, Figure 7 |
Conclusion of 2013 Study
The engineers responsible for this survey mapped flow characteristics and then applied four models (remove all culverts, dredge a channel, remove vegetation, and introduce a flushing flow). They determined that the only model that significantly increased the flow was the model where a 50 foot wide swath of vegetation was removed from the center of the slough.
"Reducing channel resistance by clearing a 50-foot wide swath of all aquatic vegetation appears to have a significant impact on average channel velocity. This option has some advantages to the other options analyzed in this report, including the lack of earthwork or other construction activities such as dredging or culvert replacement."
The problem with the Chena Slough is its overall health. Cut off from the Tanana, it is a slow moving seepage-type stream. Now filled with weeds, invasive and native alike, the slough cannot move correctly. The build-up of silt is likely a contributing factor, according to this report as well.
3. The FSWCD
The Fairbanks Soil and Water Conservation District has done a phenomenal job cheerleading the need for restoring the Chena Slough over the past 20 years. They are a minor state government organization, chartered to "Support self-governance and property rights, to assist landowners and managers with conservation and development through technical, financial, and educational programs."
The FSWCD falls under the Alaska Department of Natural Resources (DNR). The DNR has effectively neutered the state's SWCDs in dealing with Elodea infestations. For instance, the Anchorage SWCD (ASWCD) discovered an infestation of Elodea in their Sand Lake and wanted to explore non-chemical methods of eradication or even allowing it to grow. Their management plan was completely stopped mid-progress as explained here (ASWCD, 2015):
"The ASWCD has absolutely no involvement in the current project on Sand Lake (or Delong or Little Campbell Lakes) to utilizing fluridone for three years in each of the three lakes, starting this summer (2015). All questions should be directed to Heather Stewart of the Alaska Department of Natural Resources (DNR) at (907)745-8721.
DNR halted the ASWCD's public process and have proceeded without
1.) a completion of the public process or outstanding issues that were in final negotiation, final determination, etc.; or
2.) incorporation or meaningful review of the information contained in the ASWCD's draft report (written in collaboration with many experts from across the country, utilizing hundreds of studies, case reports, precedent projects, etc.), which was scheduled for public hearings and further public input and feedback when DNR stepped in and mandated an end to the public process.
Any communications or conversations you may have had with the ASWCD's representatives are not applicable to DNR's process or project. DNR's project will not be addressing the issues such as the sewer, incoming contaminants causing the issue, overgrowth of the other species of plants, or other issues brought to light during the ASWCD's public process. Work was to begin summer 2013, but delays by DNR prevented the ASWCD from proceeding."
This is a travesty. Is the Fairbanks Soil and Water Conservation District about to issue a similar release?
A Plan for the Chena Slough
#1
First off, Fluridone or Diquat will not work. Diquat does not completely kill Elodea, Fluridone will not be able to be controlled at the proper dosage. The Sonar salesman said that the Fluridone would need to be carefully controlled at a certain ppm to remain effective for the 60-90 days it takes to kill Elodea. A glance at any year's river gauge sites shows that the lower 1/3 of the Chena Slough will be too erratic to accurately dose herbicides.
If the water level in the Chena River rises or falls one foot, it will effect the Chena Slough for 12,000 feet (2.27 miles) to 16,000 feet (3.03 miles). Approximately 1/3 of the Chena Slough is affected by changes in Chena River flow. From the US Geological Society's flow station on the Chena River nearby, we see a typical years changes in flow:
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| From USGS Website |
These massive, continual changes will make it impossible to accurately dose Fluridone in the Chena Slough. Additionally, do we want to introduce an herbicide, one with medicinal qualities, one that has been banned in entire European Union despite their on-going battle with Elodea? The water-table level is a primary concern.
Fluridone may not be applied within 1/4 mile of a drinking water intake. There are hundreds of drinking wells within a hundred feet of the Chena Slough. The water that feed the Chena Slough also fills our drinking wells.
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| From Hydraulic Mapping and Modeling, 2013, Figure 17 |
#2
If we want to let the FSWCD do its job without the DNR stopping them, let's start a grass-roots movement to rid the slough of Elodea ourselves. Elodea is easily pulled with a simple grappling hook on a rope. Homemade ones like the state uses in surveys are easily constructed.
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| From: http://depts.washington.edu/uwbg/education/conferences/2014InvPlants/PresentationPDFs/BELLA.pdf |
If the FSWCD would offer to buy bags of Elodea that private citizens remove from the slough, thousands of man-hours would be happily donated. From experience on my property, it takes about 10 minutes to remove enough Elodea, that when dried, will fill a large garbage bag. One could fill 4-6 bags worth in an hour.
If the FSWCD paid individuals $5 per bag of Elodea, there would be no end of volunteers willing to help. The FSWCD could then give away or sell the Elodea to gardeners for compost or simply dispose of it in an empty field.
Using the FSWCD's estimates of 238 manhours to clear 1/2 acre, a couple hundred kids with rakes could have the slough Elodea free in two weekends for about $10,000 (versus $600,000 for Fluridone).
#3
Do nothing. This option is being used all over the world. Unless Elodea directly impacts a commercial or recreational activity, we need to just live with it. Elodea is in the Chena, Tanana, and quite possibly the Yukon rivers by now. The Chena Slough needs to be the state's case-study for "doing nothing".
In 2011, the FSWCD wrote a report on Chena Slough Elodea which stated:
"Elodea will most likely not cause catastrophic damage to any particular resource."
Yet the same year, the National Park Service also wrote a report on Chena Slough Elodea which stated:
"Each year of doing nothing will give the existing infestation time to spread, and will reduce the opportunity for prevention. At some point, Elodea will become so widely distributed in the state that there will be no reasonable means of preventing its further spread or limiting its detrimental ecological and economic impacts."
For 5 years we have "done nothing" to stop the spread of Elodea from the Chena Slough. Is it time to allow "jack-booted thugs" to tell us we must submit the Chena Slough to three years of herbicide treatment?
#4
If there is money available, let's buy a couple of these:
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| From Wisconsin DNR website |
Conclusion
This series started out strictly about restoring the Elodea infested Chena Slough. A look at its history shows that a ripping current is no longer possible as the health of the slough naturally declines. There are things we can do to increase the life of the Chena Slough that do not involve harsh chemicals.
While researching, it appears Elodea is becoming a hot topic in Alaska and it may soon be out of our hands. Nobody seems to care anymore about recreation and fish movement, but only about the Elodea that is growing here. No one even really knows what kind of Elodea this is or where it came from. Outside interests want to sell us a lifetime of chemicals to keep Elodea out of Alaska, but the entire world has tried, and failed, to contain Elodea.
Elodea is here to stay unless we lay waste to the entire state in eradication attempts. Let's not fill the pockets of Outside herbicide companies. Alaska has a great history of "sending people packing" when we smell a rat. Elodea is bring all kinds of rats to North Pole. Let's send them packing and fix the Chena Slough ourselves. Let the rest of the state learn from us.
Anyone listening?
References:
ASWCD, (2015). Alaska Sand lake Elodea Project Management Plan. Retrieved from http://www.aswcd.org/sandlake.html
Hydraulic Mapping and Modeling, (2013). Chena Slough Hydrologic and Hydraulic Analysis for Existing Conditions and Channel Modifications. Retrieved from http://www.fairbanksweeds.org/user-files/Final-Chena%20Slough%20H&H%20Report%20Existing%20Conditions%20and%20Proposed%20Channel%20Modifications.pdf
Ihlenfeldt, N (2006). RESTORATION OF SLOUGHS IN THE FAIRBANKS NORTH STAR BOROUGH (TANANA RIVER WATERSHED). Retrieved from http://www.adfg.alaska.gov/static/home/library/pdfs/habitat/06_02.pdf
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