Northern Kentucky Takes Innovative, Watershed-Wide Approach Toward Stormwater Management

With a focus on highlighting the need for increased investment in the United States’ aging and decaying water infrastructure, The National Council on Public-Private Partnerships’ (NCPPP) Water Institute, with funding from the Chesapeake Bay Green Streets, Green Jobs, Green Towns Grant Program, visited Northern Kentucky’s Sanitation District No.1 (SD1) earlier this fall to learn more about and highlight its highly effective regional approach to managing and improving wastewater and stormwater management  in many communities along the Ohio River.

SD1 began as a small wastewater treatment utility serving the river cities in Campbell and Kenton counties. It now also manages the region’s stormwater and is the second largest wastewater utility in Kentucky, serving more than 30 local governments across Boone, Campbell and Kenton counties.

In 1995, SD1 took over ownership and maintenance of many Northern Kentucky city sanitary sewer systems and, in 2003, responded to new federal requirements by launching a regional stormwater management program to ensure that cities and counties in Northern Kentucky meet federal Clean Water Act requirements. Rather than issuing separate permits, state regulators issued one permit to SD1, which authorizes the district to manage the region’s stormwater regulatory compliance activities with city and county participation. These responsibilities entail:

  • Illicit Discharge Detection and Elimination
  • Construction Site Storm Water Runoff Control
  • Post-Construction Storm Water Management in New Development and Redevelopment
  • Pollution Prevention and Good Housekeeping for Municipal Operations
  • Public Outreach and Education
  • Public Participation

In 2005, SD1 entered into a consent decree with the U.S. Environmental Protection Agency (EPA) and the Kentucky Environmental and Public Protection Cabinet that required the district to develop plans to protect streams and rivers by preventing overflows of sanitary sewage.

SD1’s consent decree is unique in that it represents the first national enforcement action that specifically cited the use of an adaptive watershed management approach to meet Clean Water Act requirements. This approach acknowledges that sewer overflows are not the sole source of stream and river pollution; therefore, SD1’s watershed approach identifies the characteristics of individual watersheds and also considers other waterway polluting sources, such as runoff from urban development, along with other non-point and point sources, such as agricultural runoff and failing septic systems. SD1 has prepared the first in a series of watershed plans, as well as full-system solutions to comply with the consent decree.

As the regional storm and wastewater utility, SD1 recognizes the role it plays regarding the quality of life in northern Kentucky.  As such, SD1 developed a comprehensive monitoring program to ensure the activities described are effective.  In 2008, SD1 enhanced this monitoring program to include a flow alteration/channel stability or “hydromodification” component, recognizing the importance this plays in both stream integrity  and the protection of nearby infrastructure. Hydromodification occurs when natural flow patterns are altered through the addition of unmitigated impervious surfaces, which can lead to accelerated stream erosion and incision rates and destabilized stream beds.  These accelerated rates can expose nearby or buried infrastructure, as well as destroy aquatic habitat.  Through intensive data collection and analysis, SD1 identified a critical flow threshold, and is currently implementing a methodology based on this regionally calibrated flow rate, requiring that stormwater management facilities be designed to reduce and/or prevent future stream impacts.

An overview of SD1’s watershed approach:

  • Recognizes other pollutant sources and their relative impacts and puts combined (stormwater and waste water) sewer overflows (CSO) and sanitary sewer overflows (SSO) into context with those sources.
  • Provides a process to address and control the highest regional priorities first to offset controls on CSOs.
  • Uses an integrated approach of controls that will address both wet and dry weather sources of pollution and increase water quality and public health.
  • Identifies a flow threshold that reduces receiving stream impacts.
  • Directs funds to projects that provide the greatest benefits.

In addition to underground pipes that carry sewage from homes and businesses and stormwater collected from street-based catchment infrastructure, northern Kentucky relies on detention basins, swales (gently sloping channels planted with vegetation), wetlands and other stormwater controls to capture and absorb, channel or slow the flow of stormwater. Although SD1 maintains some of these structures, private property owners and homeowner associations are responsible for maintaining drainage features on private property, and cities and counties are required to maintain roadside ditches, culverts, curb and gutter systems and storm catch basin grates. Further, private developers and engineers also must apply for permits based on the types of projects they will build before construction begins to manage water runoff and prevent erosion. They must include stormwater controls in their construction plans and submit long-term maintenance agreements on them to meet post-construction best management practices either on- or off-site and can also earn credits on stormwater bills for development that reduces impact on the stormwater sewer system.

SD1 has developed a variety of cost-share and technical assistance programs to provide regional stormwater services in cooperation with its partner cities and counties (co-permittees). For example, SD1 provides funding to help co-permittees install additional drainage systems, as well as repair or replace culverts that are associated with a dedicated right-of way. The district also has a three-way partnership with co-permittees and private property owners to address drainage problems and related infrastructure on private property. In addition, SD1’s technical assistance program provides engineering and planning-level assistance (i.e., concept-level studies) to co-permittees that need help in identifying problems or potential solutions to storm-related challenges.

At the residential level, SD1 initiated the Downspout Redirection Infiltration Program (DRIP), which provides homeowners with step-by-step guides they can use to manage stormwater runoff in their yards and neighborhoods. Residents learn how to cut off a segment of a downspout to redirect water runoff flow from a roof to a rain barrel or rain garden.

SD1 also actively encourages community members and stakeholders to participate in its work by joining the Storm Water Advisory Committee, which meets annually to discuss and provide feedback on its infrastructure management and regulatory compliance activities and plans.

SD1 is fortunate to have active watershed groups within the service area.  SD1 collaborates with these groups to achieve shared water quality goals through projects such as detention basin retrofits, wetlands and monitoring efforts to better determine the source of water quality impairments. 

SD1 has conducted a variety of innovative community projects that are designed to reduce or prevent stormwater from flooding combined sewer systems while enhancing the natural environment. These projects also provided cost effective solutions ranging in $0.05 to $0.27 per gallon of CSO volume reduction, which compares favorably with the typical gray infrastructure costs of $0.50 per gallon of CSO volume reduction at the time of construction. Three examples are described below.

Fort Wright Detention Basin Project


SD1 reconstructed and improved a detention basin on the Kentucky Transportation Cabinet (KYTC) property to absorb and slow the flow of stormwater runoff. The existing detention basin was modified and reinforced to hold additional storm water runoff and significantly reduce the rate at which the runoff enters the combined sewer system. Additionally, a small nature park was constructed on the city of Fort Wright’s property to provide access to the basin, which contains two shallow vernal pools to collect stormwater, a prairie area planted with native plants and grasses that that slow and filter runoff and reforested areas to provide new wildlife habitat. Boxes positioned in the trees around the vernal pools attract bats that help control mosquitoes and other insect pests. Based on monitoring, this project reduces the annual CSO volume by more than 20 million gallons during a typical year of rainfall at the unit cost of $0.05 per gallon of CSO volume reduction.

Terraced Reforestation Project


This project entailed the construction of a series of vegetated, terraced berms in the I-71/I/75 right-of-way in the city of Covington to reduce the flow of stormwater and improve natural aesthetics along a busy thoroughfare. Twelve linear, earthen terraces were built featuring compacted embankments that prevent runoff from flowing downhill and a permeable soil mix to improve runoff absorption. More than 40 shrubs and 280 trees, along with eight acres of native plant seeding were planted to absorb rainwater. Based on a typical year model, CSO volume is reduced by approximately 5.6 million gallons annually at the unit cost of $0.17 per gallon of CSO volume reduction.

12th Street Green Improvement Project


Working with the city of Covington and KYTC, SD1 ensured that stormwater best management practices were incorporated into the expansion of the 12th Street corridor to reduce stormwater runoff. Four bioretention planter boxes (cells of vegetation, mulch and soil) placed intermittently in the sidewalk catch and retain stormwater runoff from 0.5 acres of impervious roadway. A biofiltration swale containing native flowers and shrubs was also built in the open space behind the planter boxes to receive overflow from the planter boxes,surrounded by up to an acre of hillside and residential space. An interpretive park on one block features signage about historic 12th Street elements and information about SD1’s integrated stormwater initiatives in the area. Based on modeling of a typical year of rainfall, the bio retention planter boxes and bio filtration swale together reduce combined sewer overflow (CSO) volume by 300,000 gallons annually at a unit cost of $0.27 per gallon of CSO volume reduction.

For more information about SD1’s watershed management approach to stormwater management, visit the district’s website at http://sd1.org/

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