Special to The Gardner News
The average life span of a small reservoir dam is frequently estimated at 50 to 100 years, and maintenance matters. The dam at Gardner Lake has been classified as a high hazard dam as of 2018. The National Inventory of Dams bases classification on the extent of damage a failure would cause downstream, with high-hazard potential dams resulting in loss of life and significant economic losses.
In 2010, the dam looked good, said a safety inspection report by Terracon Consultants, but the spillway showed deterioration, including signs of cracking, scaling, and spalling. Spalling results from water entering concrete or natural stone, and it means the surface has flaked off, peeled, or popped out. In 2015, the spillway had degraded further, and by the most recent safety inspection report, was done in 2018 by Brent Johnson and Jacob Asgian of Olsson, an engineering firm with an office in Overland Park. The spillway was determined to be in poor condition, with exposed and corroded reinforcing steel. Vertical concrete drop structures along the spillway had been undermined or washed away, the inspection report noted.
“Concrete deteriorates as it ages,” Brent Johnson explained. “With the limestone bedrock there, the risk for erosion is low, but we recommend that the spillway be restored to its original elevation and height. Without intervention, the spillway will continue to deteriorate, lowering the lake level.”
Olsson did the dam and spillway inspections in 2015 and 2018, and the next one will need to be done in 2021, under the Stream Obstructions Act, which requires inspections every three years for high hazard dams.
“The city is looking to move forward with spillway repairs this fall, once funding can be found,” Johnson stated. “We hope to have minimal impact on homeowners. Contractors may have to draw down the lake, and the plans would need approval through the state bidding process.”
The city previously applied for FEMA High Hazard Dam Funding for planning and design of the dam embankment and spillway reconstruction, Kramer said. They did not get that grant. Kramer listed necessary work as:
• Modification of the service spillway to include adding the required detention storage
• Investigation of the water supply lines, control tower and left downstream groin area
• Removal of the trees and woody vegetation from the embankment and spillway channel
• Repair of the erosion area adjacent to the downstream toe
• Repair of the front slope riprap
• Update of the emergency action plan
• Modification of the downstream embankment slope
“Typically, the responsibility to care for, upgrade, and repair as needed falls onto the dam owner,” said Bobbi Luttjohan, chief of planning at the Kansas Water Office. “At this point it is really up to the City of Gardner to raise the funds to pay for what is needed. We will continue to pursue avenues to assist all dam owners across the state, but as for now we cannot offer further financial assistance to the City of Gardner.”
The funds budgeted for work to begin would come from debt proceeds, with repayment by the Gardner, Kramer said.
The cost estimate for the spillway was $766,053, according to Kramer. Gardner staff anticipates the project cost to increase due to additional work requested by the Kansas Department of Agriculture, Sharon Rose, Gardner city clerk, stated.
“The Kansas Division of Water Resources rejected the spillway plan submitted by the city because it did not include structural repairs to the dam itself that they deemed necessary to be done concurrently,” said Steve Shute, Gardner mayor. “Our engineers are working with DOWR to determine the next course of action. In the meantime, the 2019 funds for spillway repair are being held in abeyance in the General Fund until we get the go-ahead to move forward. More than likely, the spillway reconstruction will have to be done alongside dam repairs that are not currently budgeted. Our finance team is already working on alternate funding scenarios to complete any DOWR mandated repairs. (We are also examining any and all grant opportunities, including federal grants, that can defray the costs of dam repairs.)”
Gardner has worked diligently for several years to find funding from grant sources.
In addition to the FEMA High Hazard Dam funding, the city applied for grants from KDA (Division of Conservation, Kansas Department of Agriculture). State funding was denied. The lake is not a primary source for municipal water use.
“Hazard mitigation grants are few and far between with a high rate of competition when funds are available,” said Cary Gerst, assistant director of planning for Johnson County Emergency Management and Communications.
Spillway continues to deteriorate, repairs needed