How Do We Improve Urban Streams?

Things MSD is Doing

Floodplain Ordinance:  In September 1997, Jefferson County adopted the revisions to Article 13 of the Land Development Code concerning floodplain management. The new ordinance governs the management of floodplain lands throughout Jefferson County. The intent of the ordinance is as follows:

• To minimize the health and safety risks associated with flooding.
• To minimize the potential for damage to existing properties, as well as properties to be developed in the future.
• To meet the requirements of the newly revised portions of the National Flood Insurance Program Act and to maintain the integrity of the local floodplain management program.
• To account for the unique hydrology. To preserve the landscape of Jefferson County by attempting to balance floodplain management and economically valuable growth.
• To minimize the financial impact that floodplain management will have on Jefferson County taxpayers.

The administration and enforcement of the Floodplain Ordinance is the responsibility of MSD.

Flood Compensation Banking:   A Flood Compensation Bank is a storm water basin that is used for storm water storage and floodplain storage compensation. The basin’s volume may be purchased to offset the effects of new development or the effects of increasing impervious area. A development may purchase storage volume from the Bank to compensate for floodplain encroachment or to satisfy storm water management requirements.

A private flood Banking system provides an additional tool to minimize the effects of new development in the watersheds of Jefferson County. This tool has several advantages over the traditional smaller basin approach. Larger basins offer a better solution to MSD’s overall storm water management effort. Developers have an alternative to the regional facility fee that they are currently required to pay. Sites that are not currently developed may be used for Banks and therefore preserve existing green space.

Storm Water Management BMPs:   On November 16, 1990, the U.S. Environmental Protection Agency (EPA) required all municipalities with a population of at least 100,000 residents to obtain coverage under a National Pollutant Discharge Elimination System (NPDES) permit. This permit requires that the municipality develops, implements, and enforces a storm water management program designed to reduce pollutants and protect water quality. On February 1, 1994, Louisville and Jefferson County (with MSD designated as the lead agency) were issued the first NPDES permit within the Commonwealth of Kentucky.

One requirement of the Kentucky Pollutant Discharge Elimination System (KPDES) permit is the implementation of practices that eliminate or reduce the pollution entering the streams. Whether the pollution is point source (from a pipe discharging into a stream), or non-point source (from runoff from a construction site, a parking lot or a backyard), all require some type of remediation. Since the permit implementation, MSD has established a number of programs aimed at identifying and reducing/eliminating the sources of pollution. These "best management practices" (BMPs) include the Student Outfall Program which identifies and eliminates point source discharges to the streams, the Erosion Prevention and Sediment Control (EPSC) BMPs (established to reduce the amount of soil leaving a construction site), and the establishment of no-mow zones along streams. Future MSD best management practices will include: requiring developers of large sites to treat the runoff from their development before it leaves the site, and an education program aimed at pollution prevention for herbicides and pesticides. Some of these current and future BMPs are discussed in more detail throughout this paper.

EPSC (Erosion Prevention and Sediment Control):  For the past two years a task force has been working on the development of a local Erosion Prevention and Sediment Control Ordinance as part of the 2020 Comprehensive Plan Update. All construction activities within Jefferson County will be held to higher planning, design and construction standards. In 1997, MSD offered two five-week training workshops on Erosion Prevention and Sediment Control (EPSC). The objective of the workshops was to raise the awareness of why EPSC is important in helping to reduce the environmental impact on streams from construction sites. This workshop was designed to introduce engineers, developers and contractors to old and new EPSC technologies, and to prepare the community for the coming ordinance.

Sewering (removing package plants and septic tanks):  MSD’s emphasis in the 1980s and 1990s has been the expansion of sanitary sewers. Though most of the City of Louisville was sewered in the early 1980’s, a large portion of Jefferson County remains unsewered. Booming development within the county occurred faster than MSD could expand sewer service to these developments. MSD, with involvement from the Environmental Protection Agency, developed and started implementing plans to provide sanitary sewer service to unsewered portions of watersheds within Jefferson County. To date, sanitary sewer expansion is still of primary importance, with much of the Mill Creek Watershed still unsewered. Emphasis has been placed on extending sewers to this portion of the county, as well as filling in the unsewered "holes" that remain within other watersheds.

Over the years, approximately 200 wastewater treatment plants have been eliminated through MSD’s sanitary sewer expansion program. Small treatment plants were once considered a "temporary" solution to pollution prevention, but became a "long-term" solution when MSD was unable to expand sanitary sewers to meet the needs of development. Though small treatment plants offer a better solution to pollution prevention than septic tanks and seepage pits, they are still considered point sources of pollution. With MSD’s efforts to provide sanitary sewer service throughout Louisville and Jefferson County, 175 of the small treatment plants have been eliminated. Future expansion of sanitary sewers will eliminate many more.

Until sanitary sewers can eliminate septic tanks, proper septic tank maintenance is important. A system should be inspected and emptied every three to five years. Malfunctioning and overflowing septic tanks release bacteria and nutrients into the water table by contaminating nearby groundwater, lakes and streams. Septic systems must be constructed in porous soil that allows the sewage to filter through it. Also, septic systems should be located away from trees because tree roots can crack pipes or obstruct the flow of wastewater through the drain lines.

Restoration vs. Preservation:  MSD is interested in both stream preservation and restoration. Stream preservation is the goal in those areas not already negatively impacted by construction, channelization, runoff, discharges, etc. There are times when avoidance is not a practical alternative. In this event, MSD’s philosophy is to restore the environment as close to its original condition as possible.

Improving urban streams can be accomplished through a number of restoration techniques. These include: revegetation efforts using native plant species, creating greenways, modifying channels (including the reinserting meanders), creating more instream habitat, creating reaeration zones, floodwater retention for slow release, streambanks stabilization using soil bioengineering techniques, and creating no-mow zones around streams. Many of these restoration techniques are discussed in more detail throughout this publication.

Buffers between Sewers and Streams:   Most sanitary sewers within Louisville and Jefferson County are built as gravity flow sewers, which means that the sewage flows from a high point to a low point. In the past, MSD often constructed sanitary sewers within streambeds or directly adjacent to streams. Though design of sewers in or near the stream is perhaps the most cost effective design for sanitary sewer construction, it ignores the impact that construction has on the streams and on the impacted ecosystems. Currently, with the knowledge that these ecosystems are essential to the health of the environment, MSD has undertaken a more "environmentally friendly", less invasive approach to designing and constructing sanitary sewers. If the terrain allows, sanitary sewers are now designed to allow a buffer between the sewer and the stream. Sewer crossings are designed so that the impact to the stream by heavy construction equipment is minimized.

Greenways:  Greenways are generally regarded as a system of connected lands with a purpose of providing ecological and cultural benefits. Greenways are often located along creeks, streams and rivers, and connect places of interest within the community, such as parks, historic places, etc. Greenways have been used by communities to control flooding, improve water quality, protect wetlands, conserve habitat for wildlife, as a buffer for development, and for recreational trails. MSD, in cooperation with Jefferson County and the City of Louisville, has developed the Louisville and Jefferson County Multi Objective Stream Corridor/Greenway Program.

Habitat Enhancement:  MSD is involved in a variety of activities designed to enhance habitats and improve biodiversity. The more diverse and higher quality habitats tend to support a more diverse population of native plant and animal species. More diverse populations also tend to be healthier and have well established food webs. Impacted urban streams may have little diversity in plant and animal communities. Impaired habitats and/or water pollution provides a degraded environment in which "Pest" species dominate the ecosystem. Types of degradation include removal of vegetation from stream banks, the use or escape of invasive alien species of plants and animals, channelization of streams, dredging of substrates, and unnatural flows produced by increased impervious areas. The introduction of lawn chemicals can negatively impact stream quality by increasing the amount of algae in a stream, lowering the oxygen level within the water and frequently producing toxic reactions.

Various types of habitat enhancement are discussed in the following paragraphs:

• Reaeration Zones:  Many streams in Jefferson County have been channelized, and consequently they provide marginal to poor conditions for the support of aquatic life. One major problem with these streams, particularly during low flows, is elevated temperatures resulting in reduced dissolved oxygen levels and fish kills. MSD has begun the installation of reaeration structures. These structures resemble small waterfalls. The intent of the reaeration structures is to increase water turbulence, which then increases dissolved oxygen levels. Rocks are often used to create riffle areas above theses waterfall in order to enhance habitat and produce a more diversified fish community.

• No Mow Zones:  No mow zones are defined as areas adjacent to streams that are allowed to grow undisturbed. These no mow zones provide improved biodiversity, enhanced riparian habitat, improved dissolved oxygen levels, and increased bank stability. Allowing vegetation to grow naturally helps improve stream quality. With time, trees and other deeply rooted plants grow along the stream bank, providing bank stabilization as well as shade to the stream. More diverse plant communities along the stream banks promote diversity in animal populations within and around the streams.

Trees are of primary importance when assessing the health of the stream corridor. Trees not only provide bank stabilization and prevent soil erosion; they also provide a canopy over the stream and reduce the temperature of the water. Many of the streams in Jefferson County are exposed to excessive amounts of direct sunlight, resulting in water temperatures that are higher than many species of animals can tolerate. The tree canopy can reduce stream temperatures by 5 to 20 degrees Fahrenheit. Cooler water has more physical ability to retain oxygen. Reducing the amount and intensity of sunlight also aids in the reduction of harmful levels of nuisance algae that can cause oxygen depletion in the stream.

Property owners living adjacent to the stream can assist the stream’s development by allowing the area along the stream to grow naturally.

• Soil Bioengineering:  Soil bioengineering is a relatively new practice for stream bank stabilization and restoration. Bioengineering is the use of live plants in combination with other structures to stabilize the banks of streams. Traditional engineering practices have relied heavily on the use of concrete to provide this stabilization. This "hard" engineering practice eliminated habitat for wildlife, and also may act as a heat sink. The use of live plants produces a more attractive, natural, and diverse plant community along a stream corridor. The plants produce a stable stream bank, reduce sedimentation and erosion, and generally produce higher quality stream habitat.

Improving Urban Streams continued