805 Des Moines Drive
Windom MN 56101
November 18, 2008
Mayor Riordan & City Council
City Administrator Nasby
444 9th Street
Windom MN 56101
Dear City Leadership:
We offer the following comments regarding the 11-13-2008 SEH “Feasibility Report”:
The EXECUTIVE SUMMARY states the dam failed during a recent flood event. Comment:
The attached DNR Windom Dam photos dated 8-18-2005 and 4-7-2006 indicate the DNR knew the dam riverbank was eroding well before 2007, the date used by SEH as when this situation started. It was a long-term failure that one would reasonably conclude from the photographs was allowed to proceed to the current status. I do not know when the City had knowledge of this issue. Timely maintenance and completion of a 20 year old temporary repair could have prevented the current situation. See Attachments “A”.
The EXECUTIVE SUMMARY discusses limited short-term funding options. Comment:
As our group has advocated, restoring the riverbank can be but one step in a longer range plan. As SEH correctly notes elsewhere, if the dam was removed then the newly dry property reverts to private hands. Obtaining the needed 100% cooperation from the affected stakeholders for projects after removing the most attractive feature in their environment would appear to be problematical. The difficulties in selling river property as expressed by Mr. John Galle speak for themselves. Maintaining the reservoir and continuing to make use of the flowage easement the City now has would maintain this area as public waters. As we discussed within our “Save the Dam” stakeholder group this maintains the potential for using the island as a nature area or trail interconnected with the mainland on either end with pedestrian bridging. SEH did not consider the recently passed Constitutional Amendment which creates a funding stream of over $100 million per year specifically “To restore, protect and enhance wetlands, prairies, forest and habitat for fish, game and wildlife. And “to support parks and trails wetlands restoration projects”. DNR Trails and Waterways funds or Transportation Enhancement Funds, both of which are viable funding sources for island trail related work in a public land setting were also apparently not considered in the context of a longer term multi-phase approach.
The EXECUTIVE SUMMARY states “…several residents…..” who expressed their desire to maintain the dam pool. Comment:
See my comment for “3.3 Alternative Refinement” below.
The EXECUTIVE SUMMARY makes comments regarding the DNR concerns about the need to promote fish passage Comment:
We simply note that upstream, at the Heron Lake Outlet into the Des Moines River, there is an electric fish killer to prevent rough fish passage into Heron Lake which is an interesting contradiction. We also note a riprap retrofit downstream of the dam would address this concern (see SEH alternative #3).
As previously discussed, a riprap retrofit (as per the video of Fargo) would create a centerpiece of a revitalized Island Park. The pool drawdown capability would facilitate future reservoir related work should the city choose to pursue this option in the future.
The EXECUTIVE SUMMARY makes the statement that “there are no technical reasons to maintain the dam” Comment:
This is simply not true. Attached is a North Dakota State University paper (Attachment “B”) that discusses the engineering benefits of low head dams that SEH has chosen to disregard. Lessons learned by experience from others, and from the Red River should never be trivialized. The overall stability of the Windom reservoir area for over a century is also noteworthy, considering the otherwise strong meandering nature of the Des Moines river.
Also noteworthy is the fact that it is acknowledged that removing the dam will result in significant riverbed scour during major events. This will place water, sanitary, telecom, and gas lines as well as bridge piers at risk unless they are otherwise stabilized. I note the following sequence of events regarding these concerns:
(1) My concerns were attacked in internal DNR correspondence as “Bush-Cheney” scare tactics.
(2) Bridge stability concerns were at first trivialized by SEH in 9-16-2008 correspondence under the mistaken assumption that the bridge pilings were 300 feet below the riverbed.
(3) All these items were determined to require steel sheetpiling for effective protection.
(4) In the final report it has been determined that “rock cutoff walls would be sufficient protection. Ironically, substantial rock cutoff wall construction may require steel sheeting be driven during construction. It is noted that substantial rock protection around the bridge pilings would both decrease the cross sectional area under the bridge and therefore further increase the water velocity during major floods.
Less substantial rock structures are susceptible to failure as has apparently already happened to the rock riffles at the Appleton MN river restoration project.
We also note this report has no discussion of flow velocities in the dam-out condition compared with the dam-in condition, even though the scour potential changes from very minor to significant due to the steeper gradient of the dam-out riverbed.
We further note that as the riverbed scours to a natural river profile elevation along its length, the amount of soil cover over the utility lines will decrease in a dam out condition. Without the insulating effects of water, the ground will freeze and heave and this could lead to the failure of some utility lines with major consequences at particularly critical times of the year.
The EXECUTIVE SUMMARY makes the statement that “If changes are made to the river channel, property values could impact home sale prices and potential future revenue to the City in the form of taxes….”. Comment:
If the homes of Windom residents are damaged by actions of the City, one may assume that reduced property taxes may be the first of many issues the City will have to deal with.
The EXECUTIVE SUMMARY discusses sediment removal Comment:
An ideal water depth for migratory bird habitat is 4 feet, it is suggested that future regrading efforts and/or sediment removal efforts have this in mind, along with maintaining a linear natural island in the river which was a major nesting area for ducks, geese and other bird and wildlife. As mentioned earlier, this state has just created a major new long term funding stream for wetlands restoration projects that should be considered. Again, maintaining this area as public lands with a reservoir setting would seem to be preferable than dealing with individual landowners.
Sleepy Eye is an example of a successful local dredging project. Redwood Lake using primarily state bonding funds would have been a similar example except for the fact that their project bidding was held at the peak of the oil price curve. (They anticipate rebidding their dredging project according to the Redwood-Cottonwood Rivers Control Area August 2008 Newsletter.) In over a century, there has never been a dredging project in the Windom reservoir area.
2.0 CHRONOLOGY SEH discusses a 1959 US Army Corps of Engineers (USACE) study that recommended dam removal to eliminate sediment and flooding issues Comments:
Other noteworthy actions from April 1959 include official resolutions from Windom City and Cottonwood County. These resolutions in part state the following, in support of a dredging project:
“That the Des Moines River is considered to be one of Windom’s most valuable assets, not only for the benefit of present residents, but as an attraction to the future industrial and residential expansion of the City:
“It provides a scenic view along which many homes have been constructed and are continually being constructed. It provides the site for recreational areas, which are vital to a healthful environment for its residents and neighbors.”
“The river provides a source of beauty to the City which cannot be measured.”
“Parks and playgrounds have been developed by the City along its shores which attract literally thousands of people every year to enjoy family reunions, picnics and hours of recreation.”
“That the preservation of the Des Moines River in Cottonwood County by improving the same is deemed to be important to the recreational life of the people of our county and surrounding areas, as well as an enhancement of the living conditions as a whole.”
After due consideration of all the relevant factors, in 1960, the City completed its first major City funded dam project.
No mention was made by SEH of a June 1972 US Army Corps of Engineers Study in my possession, prepared for the MN Department of Conservation. Here they discuss suggested zoning requirements, specifying minimum basement and first floor elevations, and the like. This USACE report makes it clear the dam has a trivial effect on flooding, if any at all. This position is also supported by the findings of a previous city river committee. Interestingly enough, this USACE report makes no criticism of the dam, nor does it suggest its removal.
3.3 Alternative Refinement discussion notes that: “Survey results obtained from the public are included in the Appendix Manual”. Comment:
As previously noted we made a tabulation of survey results on Thursday afternoon October 9 at the end of the workday. I noted the following breakdown:
Keep the dam and reservoir: 27 38%
Rock riffle dam and reservoir: 28 40% .
No dam, no reservoir: 15 22%
I (and Ron Tibodeau) was very surprised to learn that as of the close of business the very next day the tally had become:
Keep the dam and reservoir: 32 33.5%
Rock riffle and reservoir: 30 31% .
No dam, no reservoir: 34 35.5%
The dam group I am part of made no effort to skew the results. One may reasonably conclude however that others may have.
While this alone wouldn’t be noteworthy, to the extent that some are trying to make conclusions about community sentiment from this data, it must be commented on. In our door to door efforts and by word of mouth, we have noted a very high level of support for the reservoir and the wetlands environment it has created. When the ecological and other reservoir benefits are mentioned, the support becomes even higher. To some extent that this data has apparently been skewed. The ducks, herons, egrets, pelicans, geese, mussels and muskrats all seemed to like a wetlands reservoir environment as well, how many votes do they get?
Discussion that notes “…repairs to the bridge will be done by MnDOT and any future bank erosion at the apartments and homes will not become an issue because the pool of water will provide the necessary protection.” Comment:
While true, we simply note this contradicts the previous assertion that “there are no technical reasons to maintain the dam”.
Discussion on Pages 7 and 8 that notes upstream transition to a perched river condition. Comment:
It is agreed that a new dynamic equilibrium will be established if nothing is done. It is also noted that the ideal water depth for migratory bird habitat is approximately 4 feet deep from discussions with others and literature. If one accepts this, and the idea of leaving a linear nature island in the river then the scope of a sediment removal or reshaping project becomes much smaller. An island would create 4 shorelines instead of two and greatly increase the habitat available for birds and other wildlife. The USACE and SEH agree that there would not be significant changes to the groundwater table in either circumstance.
Discussion on Page 8 that discusses “retraining the river” towards the center of the channel. Comment:
While this is certainly a noble goal, it is noted that if this is not fully successful the first time, then the damage to the east riverbank in a major flood could be quite severe. Damage to the Rolling Green side of the river could also occur if SEH isn’t completely successful in training the naturally meandering river exactly right. Particularly as major floods erode riverbed sediment and cuts a deeper channel upstream from the current dam location and thru the area of maximum scour near the Highway 62 bridge.
Who will assume liability if this doesn’t work, and will the City inform the residents of the new risks being imposed on them that haven’t been there for decades? At Windom, the river drains an area of 1,135 square miles and design floods at the bridge assume flow volumes of over 15,000 cubic feet per second and velocities of 4.7 feet per second. Is there a warranty on this work? If adverse effects are noted 5 years from now, will the city take the necessary steps to protect homes?
4.0 Final Alternatives - Discussion on Page 9 that notes island Park be used as emergency spillway. Comment:
It is agreed that this is the best and only feasible option, and one that has actually worked relatively well for decades. Armoring of the riverbank may be warranted to minimize erosive effects.
Discussion on Page 9 that discusses using rock cutoff walls (in place of the previously discussed interlocking steel sheeting.) Comment:
It is not agreed that this would provide the same level of protection as the previously discussed steel sheeting. More evidence would have to be provided as to why this switch from steel sheetpile was made and if it is widely accepted by industry as an equivalent substitute in this application.
5.0 Permitting discussion about the DNR requiring that the City provide a detailed geotechnical and structural investigation to prove the dam meets current structural standards. Comment:
If the DNR persists in this requirement, it is again suggested that legal counsel be involved to ascertain what statutory authority exists for this requirement. A riprap retrofit on the downstream face of the dam (Option #3) should completely eliminate any rational need for this step.
6.2.2 Ecology - Wildlife Comments:
This section by all appearances appears to be generally backwards from actual observed effects. Herons, Egrets, and Pelicans are now virtually non-existent without a wetlands / reservoir habitat where before they were abundant and seen feeding on a daily basis. Ducks are greatly diminished, about 10% or less of their previous levels. We routinely observed large families of nesting Canadian geese, the last several years this has been greatly diminished, about 10-20% of their previous levels is our estimate. While some do view geese as nuisance wildlife, particularly in certain Twin Cities urban lake areas, the large majority of Windom residents view them as very desirable and indicative of a healthy wetlands/pond environment. Eagles, Muskrats and turtles are greatly diminished without a dam also. We have observed piles of dead clams throughout the channel area. While it is more subjective, we have also seen fewer deer on the “island” without the pool of water. Most notable is that the island is/was a significant nesting habitat for the aforementioned birds, there were regular sightings of migratory birds either nesting or in the water with their young. The river residents should be acknowledged as being the most authoritative as to what is occuring in our “backyards”. “Water is life”…the less water, the less life there generally is.
6.2.3 Aquatic Species Comments:
It is noted a riprap retrofit will address most or all of these concerns. It should also be noted however that piles of dead clams are in the reservoir area, ironically killed by the loss of the pool habitats in which they were living. Directing the reservoir water flow into one or two channels will mimic natural flow conditions.
6.3.1 Sediment Accumulation Comments:
Any notion that the river channel has stabilized is premature since this town has not seen and significant flood events since 2001. Regardless, SEH also notes elsewhere the channel should be modified if the dam is removed. A significant flood may well in fact mobilize major amounts of sediment and transport it downstream as a natural river downcuts to the natural channel and resumes meandering action.
Given the ecological considerations prevalent at the DNR, there is every reason to believe the DNR will NOT allow the construction of another dam at this location regardless of the needs or wishes of the City and residents. It is noted that DNR controlled dams are in place upstream at Talcot Lake and Currie Lake but they are actively attempting to remove non-DNR dams elsewhere.
6.3.2 Highway 62 Bridge Comments:
It is noted that the bridge plans refer to a dam in place downstream. SEH also reported the scour calculations show the potential of 19 feet of scour in a major flood with one foot of safety margin at the Highway 62 bridge pilings. Any proposed changes to the hydraulic environment and associated mitigation should be discussed with MnDOT bridge and hydraulic staff in Mankato and/or the Central Office bridge staff in Oakdale.
Beyond the bridge, again this scour issue needs to be considered in the context of utility lines in the vicinity of the bridge. Making sure these utility lines are in stable ground and also protected from frost heaving and a shifting riverbed is a concern that cannot be overemphasized.
6.3.3 Flooding Comments:
The table for Windom contains recent flood spikes that are misleading. A review of the hydrograph curves at the time revealed sharp “spikes” in the data indicative of ice affecting the actual gauge. This is why I asked SEH to include the Jackson gauge data which is more representative of actual river peak flood conditions over the decades.
6.3.4 Groundwater Comments:
Reports also indicate that a number of residences throughout town use pumps because of the shallow groundwater in general (Perkins Creek and the Des Moines River establish a hydraulic perimeter around a major part of town.) During any wet season and spring runoff the water table throughout town should be expected to remain shallow. This has always been the case in Windom and always will be regardless of the dam status.
6.3.5 Recreation Comments:
Suggested larger scale prototype can be found in Pierre, SD – see attachment “C” for LaFramboise Island. In Windom the scale would be more modest and focused on a nature trail. One downstream connection could potentially be made to the sanitary lift station property which is both very attractive and underutilized. This would provide a seasonal nature trail and help reconnect people with the environment in a unique manner.
6.3.8 Maintenance Comments:
Sediment has never been removed in well over a century from the River, according to our information. (It has been moved to create a channel behind 4 houses in Rolling Green some decades ago, for $400.) Performing an activity like sediment removal every 50 years should not remotely be considered as a maintenance level activity. Practices such as farm drain tiling in fact reduce sediment runoff and therefore are helpful to the situation. The local county environmental office is also working to improve the situation by for example promoting best management practices in farming. A contact at the Cottonwood County Environmental Office previously noted the sediment-loading situation is improving, not getting progressively worse. The sediment also needs to be mapped to help model what best to do with it.
SEH notes that “If the dam is removed, maintenance and inspection responsibilities will shift to the protection of the structures next to the river.” Given the level of stewardship shown by the city to the dam, a much higher standard of care will be necessary if the City changes the historical status-quo conditions.
6.3.9 Slope Stability Comments:
Again, we refer to the North Dakota State University article which speaks for itself.
It is agreed that in any event the entire reservoir would benefit from river slope improvements, particularly the planting of suitable native grasses with very deep roots and the educating of landowners as to their benefits.
There is no discussion at all of potential slope stability concerns in the West River hillside which has a very shallow water table interconnected with the river. The water table will undergo wider fluctuations without a dam to moderate the fluctuations. These are risk factors for slope stability concerns and besides homes there are some critical structures that could be at risk.
6.3.11 City Liability Comments:
As SEH correctly notes, each site is unique and needs to be judged individually. However we also note that the residential protection measures in place work in the dam-in situation but may function differently in the dam-out situation depending on channel redirection efforts and changes in flow velocity. We have seen no flow velocity discussions, dam-in vs. dam-out. We have seen no discussion of how faster flowing and focused floodwaters would affect the riverbank opposite Island Park without the benefits of a dam at the current dam site.
It is not logical to state that “If the dam is removed, the liabilities associated with owning a dam are removed”. If by removing a dam, the city causes damage, one can reasonably assume the city would be liable.
I have provided an example of my slope stability concerns using an example from along a state highway adjacent to a river in Crookston (see Attachment “D”) as something that should be seriously considered in Windom. Again, my concerns were trivialized with the message being “It can’t happen here.” Yes, it CAN happen here. It would be prudent to consider why it hasn’t happened in Windom.
In medicine a principal precept for medical students is “First, do no harm." We suggest it applies here as well.
Save the Island Park Dam Group
Attachment A.1 - Windom Dam 08-18-2005 Photo from DNR
Attachment A.2 - Windom Dam 04-07-2006 Photo from DNR
NORTH DAKOTA STATE UNIVERSITY
4. LOW-HEAD DAMS - Over the years, we have observed that the greatest rates of mass wasting occur: 1) when soils are saturated with water, and 2) when the river level is low. Because the Red River is a manipulated river (operations of dams upstream often control outflow), times exist when the river level at is low even at times of high soil moisture conditions.
Our maps of problem areas in the Fargo region show a related phenomenon: slopes in pool areas above low-head dams show little propensity for large-scale failure. Indeed, much of the area of east-central Fargo has shown no indication of slump development, even during saturated soil conditions.
We suspect that the dams are affecting the rates of slope instability in two ways: 1) in the pool area, a constant water level serves to induce continuous hydraulic pressure against the channel walls, slowing clay flow toward the channel, and 2) the velocity profile of the river is "evened-out" across the channel because of the presence of the dam. Because water spills over the lip of the dam at a uniform rate, erosion is no longer concentrated at the cut bank positions of meanders within the pool region.
Although dams seem to be effective structures at reducing mass wasting rates, it is unlikely that any more will ever be constructed along the Red River. Dam construction is expensive, and the placement of dams on the Red requires an approval process involving two states plus the federal government. Dams have a negative impact on fish movement. They are also dangerous (many drownings have occurred on local dams) and inhibit the development of other recreational uses for the river. In some areas, the presence of a dam could negatively impact water quality; such, for example, would probably be the case if a new dam were to be installed at the north edge of Fargo.
Upstream of this dam near 12th Avenue North, the rates of slope instability are markedly reduced. Dams can be effective engineering structures to remediate problems with mass wasting along the Red River. However, there are many problems associated with dams, and hence the construction of additional dams simply to relieve slope instability should not be encouraged.
(RJW Note: a downstream riprap retrofit eliminates the “drowning machine” hazard as per DNR produced video.)