After a particularly heavy rainstorm, a homeowner watched excess storm water back up from a backyard drain nearly to his lower level windows. After inspecting the drainage plan created by the original developer of KPVillas, the homeowner asserted that stormwater design elements not approved by St. Joseph County have contributed to the water woe.
The St. Joseph County (SJC) Office of County Surveyor/Drainage Board responded to the homeowner's inquiry in July 2019. The SJC Construction Supervisor noted that the existing storm water storage system connects a drywell in the homeowner's backyard to the curb inlets in the street. "Since this stormwater system has been significantly altered from the original subdivision drainage plan approved by the county, the county has no jurisdiction or responsibility for the design, function or maintenance of this stormwater system."
Contrary to how the system was originally designed, water instead drained from the street to the affected homeowner's yard, where it accumulated. The SJC Construction Supervisor could not determine if the existing stormwater system was built by the developer, the original home builder or modified by a previous homeowner.
After looking further into the developer's drainage plan, the homeowner cited multiple alleged shortcomings in the engineering, including drywells not being approved; retention ponds not being built; retention ponds being undersized; street sewers missing; and excavating and elevation grading issues.
KPVillas has experienced stormwater issues previously. A 2007 Stormwater Drainage Study (linked below) prepared for the County concluded the existing pond south of Oak Hill Blvd. had "insufficient storage capacity to retain the storm water flows, as designed...and overflow is contributing to an eroding channel downstream of the pond on adjacent property." Because excess stormwater was flooding the farmland, and County standards for storage of water from a 100-year 24-hour storm were not then met, the County purchased the farmland and built the Gumwood Road Expansion Retention Pond to the south.
After the new homeowner experienced problems in 2019 and raised concerns about the developer's departure from County drainage recommendations, the County revisited the stormwater issue. After conducting a survey of the grounds, a local engineering firm proposed additional changes to the drainage configuration in the St. Joseph County Storm Water Drainage Study- Knollwood Park Villas January 2021 (linked below).
The 2021 study made two recommendations that most impact KPVillas. First, it suggests the County plug the storm sewer that flows to the noted drywell. Rather than have stormwater flow out of the sewer into the backyard at the drywell (which is already contrary to the original design's intent), that pipe would be sealed off and stormwater from uphill would bypass the inlet at the intersection of King's Crossing and Oak Hill Blvd.
The County has since put a temporary plug in place, though the integrity of the plug is not certain. This article cannot address that action.
The 2021 study notes the plug, while alleviating the flooding issue upstream, would increase flow to the KPVA pond downstream. However, "according to the model, the rest of the stormwater conveyance network within the subdivision, including the ponds, appear to be performing adequately."
That said, turbulent water discharging into the KPVA pond might be compromising the system, as recorded here.
Additional seasonal pressure may occur on the drainage system in ensuing years per Purdue University's Aquatic Ecosystems in a Shifting Indiana Climate: A Report from the Indiana Climate Change Impacts Assessment. Under the Amount and Timing of Water, the report notes, "Observations show that annual, spring, summer, and winter average streamflows are increasing at the majority of locations across Indiana, while average fall streamflows are generally decreasing (10). Future projections indicate that streamflows are expected to increase from January through May in Indiana and decrease in the summer and fall (10)."
The 2021 study's second recommendation is to expand the Gumwood Road Retention Pond by 128,500 cubic feet and make other improvements to it in order to facilitate drainage of the collected water. While the retention pond has always been water-filled, the original intent was for the water to filter through the top layers, which proved less permeable than desired. Three proposed new drywells would punch through that dense upper layer to allow the retention pond to drain. A riprap boundary would lessen the soil washing into the basin, for the added silt decreases the holding capacity over time.
One item to clarify is the riprap channel along which the water flows between the KPVA pond and the larger Gumwood Road Retention Pond. The 2021 study's Field Investigation states, "The riprap does not appear to be performing as intended due to erosion. See accompanying photographs in Appendix C." Only the first of those two quoted sentences is accurate.
The photographs provided in the study do not align with their locations on Figure 3 of the topography map taken from the 2007 study. There is less sense of urgency if the erosion is in the middle of the large pond, as depicted. However, when the placement is corrected (image below), one can see the erosion is happening on KPVA property, within several feet of the edge of the KPVA pond. Again, erosion at the pond spillover is shown in an image in the Turbulent Water blog post.
As of this writing in April 2022, the County has not publicly moved forward on the 2021 study's proposed changes. However, a St. Joseph County Drainage Board technician suggested the County would give engineering advice and split the cost of correcting the spillover problem. The bulk of the spillway is on SJC property, with KPVA owning only a small swath of land on the south side of the KPVA pond.