St. Joseph County (SJC) is proposing tiered modifications to its retention basin south of KPVillas "to allow the basin to completely drain after storm events," per SJC engineers' meeting minutes. Regardless of the eventual basin changes, the next phase of the plan will likely include re-construction of the degraded spillway between the KPVillas pond and the SJC basin, for which the County will take the lead role.
If initial conservative efforts by SJC don't improve the basin's water-removing capability, more aggressive options would follow. Then, outcomes of new construction may include, but are not limited to, dewatering the basin; an expanded basin to the north and east; loss of foliage along the boundary; and a longer and closer fence along KPVillas lot lines.
A summary of the August 2023 SJC meeting minutes and relevance to KPVillas is posted on the KPVillas Retention Pond page (October 19, 2023) and is reprinted below:
St. Joseph County (SJC) has identified some next steps in the Gumwood Road Basin Improvements project, which is a County initiative to alter the large retention basin on the south boundary of KPVillas. Per the minutes of a 2023 August 15 SJC Design Meeting, the County seeks "to allow the basin to completely drain after storm events." Among design outcomes may be dewatering the basin; an expanded basin to the north and east; loss of foliage along border; and a longer, closer fence along KPVillas lot lines.
The County basin was originally supposed to hold excess stormwater until the water percolated through the ground. Instead, it has retained water continuously, with the excess water encroaching on adjoining private properties after heavy rainfall. Recently the County commissioned a study from engineering firm Lawson-Fisher Associates PC (LFA), after which the County staff met with LFA to discuss remediation and next steps.
A former KPVillas homeowner recalled how he was told by a party to the original basin construction, "You'll never see water in there." In fact, the homeowner never saw it dry, for the basin has always held water like a pond. Over time the basin with its omnipresent water has become a vibrant habitat for waterfowl.
In the meeting minutes, the geotechnical report notes how an impermeable layer of silt is preventing groundwater from filtering down to the water table. "Currently there is a layer of fines on the surface of the basin floor that is preventing drainage, which must be addressed before any solution is implemented."
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The County will likely take a tiered approach to improve the functionality of the existing basin. If one conservative modification doesn't work, it would step up to a more ambitious (and expensive) plan. A possible first step is to de-water the pond and locate the sandy levels indicated by the studies. Capital improvements would begin with drywells if they're deemed a viable solution. These large concrete cylinders with holes would punch through the impermeable layer and allow accumulated water to percolate down.
If alterations within the extant fence line don't yield sufficiently lower water levels SJC would consider a more aggressive project. For example, a leading County proposal would be to purchase the (Fox) farmland east of the County's current retention basin and to expand the basin's size. That plan may include expanding north and east, potentially bringing the County basin and its longer fence up to the property line of KPVillas.
Another design item from the engineers' meeting specifically addresses the KPVillas pond and spillover. A construction supervisor writes, "We did discuss the transition area between ponds, and the reconstruction of that area is also included in the next phase." From the meeting minutes:
"Riprap Overflow from Knollwood Villas Basin – The landowners to the north of the project have requested that the project allow them to continue to utilize a walkway around the edge of the pond to the north of the basin. To mitigate future erosion, options will be reviewed for the overflow that passes into the basin. Examples given were geoweb, a culvert, and riprap. A culvert would be least desirable due to the potential for backwater from the Gumwood Basin to impact the Knollwood Villas Basin."
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Expensive caissons had been considered for the site; however, "acquiring property, expanding the basin to the east, and installing drywells would likely eliminate the need for extensive dewatering."
The County's 2023 August meeting minutes conclude with Next Steps:
Final Plans and Specifications –
LFA will provide an exhibit that identifies the area to be acquired in order to expand the basin per the recommendation from the 2020 report.
LFA will design a typical section of the area north of the basin to serve as an emergency overflow from Knollwood Villas. Considerations for it being traversable by pedestrians will be incorporated.
LFA will gather pricing estimates for different construction alternatives in order to compare them to the cost of acquiring the Fox property to the east.
The City (sic) will investigate the cost and feasibility of purchasing the Fox property.
[Blog post updated October 19, 2023.]