From: “Ruth Wright”
Subject: South Boulder Creek – Flood Mitigation Project 2-25-20
Date: February 25, 2020 at 1:37:10 AM MST
To: “‘Boulder City Council ‘” <firstname.lastname@example.org>
Hello Members of the City Council,
Here are some comments for you to consider and perhaps get some clarification for all of us, at your ery important discussion on Tuesday Feb 25th.
The Detention Pond. The concept of the flood control mitigation project is quite simple. We detain flood waters flowing down the South Boulder Creek Valley on the upstream side of Highway 36 in a large detention pond, and then, the water is released in a controlled manner through the West Valley on the downstream side of Highway #36. The key to success is the detention pond, especially its size. If it is too small, flood waters will go over #36, flow down the highway, and spill into the urbanized West Valley, including Frasier Meadows – as it did in the 2013 flood. Without going into details, it should be mentioned that CU South has the lowest elevation in the Valley, not only because of the angle of Highway 36, but also because the gravel and sand removed by years of mining by Flatirons lowered much of it by 12 feet. And as you know, there are several small ponds on the site showing a high groundwater table. CU bought the 308 acres in 1996 – much of it a mined-out gravel pit – with its eyes wide open.
From the beginning, CU proposed that the smallest amount of land (the “footprint” for the detention pond) be used so that the maximum amount of land could be developed, Excavation to minimize the footprint was first suggested by CU’s Jeff Lipton at meetings of the design team in May and June 2010. The high ground water table was mentioned, but quickly disregarded. (The meeting summaries are attached.) Eventually Option D from the July 2015 “South Boulder Creek Major Drainageway Plan – Alternatives Analysis” by the consultant CH2MHill was chosen as the preferred alternative. Nowhere in the text of the report does it mention the size of the Option D’s detention pond, nor that a large portion of the detention is created by excavation, which would already be filled by groundwater when the next flood arrived. Digging into the voluminous 2015 consultant report, I found that only 81 acres (the footprint) were devoted to storage of 371 acre feet of water. Option D was eventually rejected. For the next iteration our new consultant firm RJH acknowledged the high groundwater table. But instead of getting more land, the consultant still proposed excavation down to bedrock, but now sealing the hole with an impervious wall down to bedrock – creating a huge permanent hole in CU South. While I have some concern that over time the wily waters will somehow find their way into this hole, how much does such an engineering solution like this cost, versus simply obtaining more land for the detention pond?From the time that Jeff Lipton insisted on excavation, it has been part of each iteration (but one, to be explained below) and the present proposal is no different. CU still refuses to provide an adequate amount of land for the detention pond.
CU/City Relationship. As you know, the only possible location for the City’s flood mitigation project is on CU South, having been run out of town by the residents of Marshall further upstream. Boulder needs some of CU’s land to build the project. On the other hand, CU needs to annex to Boulder to obtain the many services a city provides, like water, sewer, etc. so that it can develop its property. It is definitely a “quid pro quo”, though the media sometimes touts CU’s generosity in “giving” the land to Boulder. Before annexation, a home rule city, Boulder, has equal negotiating powers with a state entity, the University of Colorado. However, because Boulder needs this project NOW, and CU will not be developing CU South in the near future, CU has us over a barrel because it can wait it out. Perhaps that is why CU now has a new demand. Incredibly, CU now insists that the City pay for bringing enormous amounts of earth to the site to “soil fill” its gravel pit and raise the elevation of some of its property so more can be developed! CU knew what it was buying in 1996 – “a pig in a poke”. Now it wants the City (we taxpayers) to remedy its own mistake, a situation of its own making, by paying an extra $10 to $24 million!
Regarding the 100-year versus 500-year issue. Our latest consultant at RJH would have you believe that the 500-year option is financially unattainable. A look at Table 5 (attached) shows otherwise. The 500-year option actually has the highest cost-benefit ratio. When this chart was first presented to you, the cost of the project and the cost of filling the land (now called the Soil Fill) was not broken down. Now we can see why the 500-year option appeared to be so much more expensive than the 100-year. It was the Soil Fill: $10M for the 100-year and a whopping $34M for the 500-year – a $24M difference. Now you can see that for the flood mitigation project (named Regional Flood Detention on the chart) by itself costs $47 M for 500-year option cost versus $ 41 M for the 100-year – only $ 6 million differential. And the additional benefits are huge: people benefitted 4,100 vs 2,300; structures 730 vs 260; dwelling units 1,900 vs 1,100. A very good cost-benefit ratio!
The Soil Fill is not part of the flood mitigation project. It is a totally separate issue that needs to be debated!
Upstream Storage Many citizens testified in support of some storage further upstream so as not to have all of our eggs in one basket. It would also relieve the tight squeeze that now exists for adequate detention, requiring excavation. For reasons unknown City staff and the RJH consultant have always given this idea short shrift. And while the environmental consultant objected to upstream storage because it would impact the water plants that have established themselves there after the mining days, she inexplicably did not object to using the only OSMP open space that is designated a State Natural Area for the detention pond in one of the options. This also happened to be the only 500-year option that CU supported because it created a huge dam perpendicular to Highway 36 which completely protected CU South from any flooding.
Recent Federal Court case. A December 2019 Federal Court decision held that a government-induced flooding on private property constituted a “taking of a flowage easement” under the 5th Amendment of the US Constitution and held the federal government liable for the damages it caused. The Corps of Engineers built a huge dam to protect Houston, but did not buy enough land upstream of the dam to hold all of the floodwaters. It had been open prairie, but subdivisions were built, and when Katrina swept through, the upstream homes were flooded. (Copies of the first and last pages of the decision are attached.) I have copies of the entire case if you are interested.) Although the fact situation is very different, there are also similarities and takeaways. Most importantly, the decision recognizes “flowage easements” – in effect, rights-of way for flood waters. If these flow easements are interfered with and damage of private property results, the governmental entity is liable for such damages. Using the “takings” argument in flooding cases is, for me at least, a whole new legal way of looking at drainage and flood control. If a building were approved in a floodway, for example, and the waters damaged private property which would not have been damaged but for the new building causing the changed flood flow, it is a “taking”. Governments beware! And what would the court say about CU’s berm which kept CU South dry during the 2013 flood, while forcing additional flood waters over Highway 36 into the West Valley – thereby causing more harm to its citizens and property. (Map Attached) Or what about CU doing considerable “soil fill” in its floodplain and the City funding CU to accomplish that – thereby forcing the floodwaters to flow elsewhere to someone’s detriment. Let’s be thoughtful about this.