Wednesday, June 07, 2023

Subdivision raised too many questions with too few answers

| December 19, 2006 11:00 PM

To the Editor:

If you're wondering if logic rules in Lincoln County, don't waste your time wondering.

The McMillan Creek diversion ditch that makes a T-intersection at Farm to Market Road was accepted as the delineation for a 100-year flood as it acts as a barrier of flood protection to the proposed Airport Way subdivision.

Although 70 very concerned neighbors representing nearly every home in the area signed a petition against the subdivision, the subdivision passed a conditional preliminary plat approval by a unanimous vote from the county commissioners.

There were too many questions and too few answers for this subdivision to have ever been given the go-ahead - too many assumptions and not enough facts and even when facts were available, assumptions were made.

During the three public hearings, numerous causes for concern were brought forth including the history of flooding below the McMillan Creek watershed, wrong numbers used in the design of the diversion ditch, the actual ditch not even built according to the design, and evidence of erosion and failure of the check dams already occurring with just the fall rains.

When the diversion ditch was designed, an assumption was made that the average-sized stone in the channel was 150 mm (cobble sized) but when an outside study was conducted on the ditch, the average-sized stone was found to be only 30 mm (gravel sized).

This can have a huge impact on the stability on the channel since the friction within the channel is in reality less; water flow speed becomes higher, erosion higher, and more sediment ending up at the bottom of the ditch along Farm to Market Road ultimately clogging culverts resulting in flooding.

No true investigation of the watershed was conducted and incorporated into the design and construction of the ditch. The percent of the 6,057-acre watershed was assumed to be 95 percent forested but the actual numbers from the Forest Service indicate the forested acreage of the McMillan Creek watershed is closer to 67 percent, which means a higher water flow than estimated.

This information is important because the entire watershed is right at the maximum allowable clearcut acreage.

Also, according to Forest Service documentation, inlet creeks of the McMillan Creek watershed are highly unstable which could intensify the runoff and sediment load during a rain on snow event or the spring runoff.

To add insult to injury, the construction of the ditch wasn't even built according to the actual design. The slope of the bottom of the ditch was steeper than the design having an actual average .006 ft/ft slope rather than the designed .0038 ft/ft.

Both side slopes were designed to be the same height but the north slope was built significantly lower that the south slope leaving the neighboring property to the north more vulnerable to flooding.

The actual slopes of the banks were designed to have a 3:1 slope but the north slope varied from 3:1 to 4:1 and the south slope varied from 2.25:1 to 3:1. The change of these numbers could have an impact on erosion and sediment load.

Questionable numbers used in the design and construction of the diversion ditch as well as instability evidence indicated by erosion problems in the ditch led the Montana state regional floodplain engineer to make a statement to the county, "This channel is one the key issues associated with the proposed subdivision and it has the potential to have a direct and adverse impact upon the public's health and safety inside and outside of the development, therefore the DNRC recommends that the above referenced issues and problems be resolved prior to this proposed project moving forward in the subdivision process."

Well, all I can say is excellent advice from the DNRC because just last week, due to an increased water flow from the half inch of rain on Tuesday and Wednesday morning, the water flowing through the ditch later Wednesday night and Thursday morning absolutely destroyed the gabion structures and water backed up along and nearly flowed over Farm to Market Road, just as the county was warned and backed up by strong evidence. Yes, "Nightmare on Farm to Market Road" is fast becoming a reality right in front of our very own eyes.

Where's the logic thinking a ditch will hold a 100-year flood but the entire Amish field couldn't contain the flood of 1997? Where's the logic in claiming the ditch will carry a 100-year and even a 500-year flood without considering the fact the ditch has a bottleneck at Farm to Market Road?

This whole project is entirely based on theory since there's never been a gauging station in McMillan Creek to know the actual watershed flow. An engineer might be able to draw a ditch on a computer but when too many assumptions are made, reality will paint a completely different picture.

Now that major erosion has already taken place around the drop structures in this ditch following a relatively low water flow compared to what this ditch is supposed to handle, logic would have to side with world-renowned hydrologist Luna Leopold when he stated, "drop structures cannot be permanent and should be avoided".

What this diversion ditch really amounts to is a quick fix to get water off a developer's property without any true consideration and thorough study of what impact the water would have and where it would go once it leaves the property.

Now we have a big mess on our hands. How big? No one knows for sure, but I seriously doubt we'll have to wait 100 years to find out. It could be as early as this spring that flooding occurs and we may find a new intersection on Farm to Market Road called "hammered cutoff" located just north of Hammer Cutoff.

Should the interests of developers in Lincoln County supercede the interests of health and safety of its citizens? The county commissioners took an oath of office to support, protect, and defend the Constitution of the State of Montana which clearly states in Article II, Section 1: All government of right originates with the people, is founded upon their will only, and is instituted solely for the good of the whole. Article II, Section 3 states: All persons are born free and have certain inalienable rights.

They include a right to a clean and healthful environment … acquiring, possessing and protecting property, and seeking their safety, health and happiness in all lawful ways.

Now we as citizens of the state of Montana are asking our government officials to uphold their oath of office and seek the good of the whole.

Andrew Foote