777 S Yarrow Street in Lakewood, Colorado is the location of the proposed 800,000 square foot Belmar Park West multifamily project within the habitat zone of Lakewood’s amazing Belmar Park unprotected wildlife and bird sanctuary.
The site contains unstable, expansive soil which is not an uncommon problem in Colorado. But what is unusual is that the developer plans a construction feature that makes the presence of expansive soil much more ominous.
Expansive soils cause billions of dollars of damage every year!
The losses include include severe structural damage, condemnation of buildings, and disruption of pipelines and sewer lines.
According to page 4 of the Intertek/PSI geotechnical report, the site is located in an area known from a published map of expansive soil locations to have ‘Moderate Swell Potential’.
The report further quoted from the publication “Potentially Swelling Soil and Rock in the Front Range Urban Corridor, Colorado” by Stephen S. Hart that:
“Special foundation designs are generally necessary to prevent damage.”
Soil samples tested from the site confirm the problem is there. Soil swell pressure measured as high as 5,300 psf!
Since this was not a final geotechnical report, there could be areas at the site with even higher swell pressures. They could not even test the center of the site because the original Irongate building was still there.
The presence of these expansive soils is especially ominous for the enormous proposed project because the developer also plans to use underground storage of stormwater rather than the more common surface ponds!
How is this possible you may ask? Because the developer plans to install underground concrete stormwater detention vaults against the written advice at p12 of the Mile High Flood Control District engineer:
“Concerning the underground detention systems, MHFD does not recommend underground detention facilities”
Why would a developer put these facilities underground? According to the Commercial Real Estate Development Association: “The main reason to consider underground detention is the return on investment on the value of the increased land or building capture.”
Will installing these ill-advised underground stormwater vaults in proximity to potentially unstable, expansive soils be a formula for construction disaster causing problems such as building damage, foundation damage, building condemnation, inability to complete the construction phase, bankruptcy, etc?
If you have lived in the Front Range long enough, you have likely seen examples of buildings significantly damaged by expansive soils. It happens.
Expansive soils can expand up 20% or more when exposed to water!
The City of Lakewood does not have the capability to remediate such a hypothetical disaster.
If Belmar Park West is approved and subsequently encounters technical and related financial problems, we know what can happen. We have the example of 1225 Wadsworth that became a construction fiasco in Lakewood. If Belmar Park West were also to go off the rails during construction, the project would possibly sit there decaying as the problems are worked out via years-long litigation.
And it gets much worse.
These underground vaults could pose a forever risk to the building or to the environment
Keep in mind that these underground stormwater vaults could become problematic at any future point in time even decades in the future due to inadequate inspection or maintenance. So it is not a matter of simply completing the construction phase without incident. Therefore, these underground vaults could pose a forever risk to the building or to the environment and therefore to Lakewood and the Belmar Park vicinity.
For example, without proper maintenance, the stormwater vaults could lose the ability to trap contaminants. Without proper and timely inspections, it might not be noticed if the vaults develop cracks or leaks allowing detained water to leach into the surrounding expansive soils.
A Geologist Offers Advice
Engineering Geologist Amy Crandall of the Colorado Geological Survey even wrote to Lakewood’s Engineering Division dated July 28, 2022 (at p.9) and emphasized the importance of “minimizing water ponding and infiltration through construction and the life of the project.“
“Strict oversight, testing, and verification of earthwork and foundation preparation activities must be performed by a qualified geotechnical professional familiar with all project-specific geotechnical recommendations”
Of course, the developer may claim the expansive soils will not pose any long-term risk due to their engineered mitigation strategies. Great! Then is there any problem providing a lifetime remediation warranty due to expansive soil damage regardless of causation?
And even with a warranty, that does not obviate the need for regular maintenance of the vaults. And when it comes to regular maintenance and inspections, future property owners may not be equally diligent. This might be especially true given the unusual maintenance chores on these stormwater facilities that are hidden underground.
There is also the safety concern that whenever workers are inside these vaults performing maintenance or inspections, if a weather event suddenly creates a stormwater flow into the vaults, workers could be trapped and drown.
As the US Department of Transportation notes: “Frequent maintenance is required to remove sediment and debris and to ensure that the outlet structure is functioning properly. Large-scale removal of accumulated sediment in the system may be difficult due to limited access. In addition, underground systems will be considered confined spaces that require additional safety requirements for inspection and maintenance.”
What Needs to Happen
What needs to happen now for the benefit of all stakeholders is that the city should require industry-proven surface stormwater ponds instead of these ill-advised underground vaults.
The city also needs to require adequate bonding or other suitable financial security to assure any failed project can be remediated before becoming a public nuisance. Otherwise, we could have another 1225 Wadsworth fiasco when the next failed project occurs somewhere in Lakewood.
Get it done, Lakewood!