Draft Notes on HMS Presentation on June 20, 2012

Re Low Impact Development

Purpose - Introduction

▪a tool in meeting water quality goals in our urban sector

▪while we have always had water quality goals, need intensified with Chesapeake Bay Restoration

▪in restoration effort, urban storm water identified as a major source of pollution, third behind sewage treatment plants and agriculture

▪of more concern than just numbers is the fact that pollution from storm water is on the increase, while the others are decreasing. The increase is due to population increase and expanded development in urban areas. Further, urban storm water is largely generated in developed areas, meaning

1. have to work around existing structures-buildings, roads, etc.

2. when opportunity presents itself, must take remedial actions

under development

Stormwater - surface water flowing across land after hydrologic events eventually ending up in water bodies unless otherwise captured, evaporated or infiltrated into the soil.

  1. In urban areas, most storm water is unable to soak into the ground because of hard surfaces such as roads, parking lots, driveways, sidewalks and rooftops discharging accumulated water directly to impervious areas.
  1. Traditional drainage systems concentrate runoff from these surfaces and remove it as quickly as possible by gutters, curbs, pipes and channels.
  1. From these conveyances,the runoff rushes off impervious surfaces and is channeled to local streams, creeks, rivers, and ultimately Chesapeake Bay. (Two exceptions – 1) the portion of Worcester County draining to the Atlantic Coastal Bays or the Atlantic Ocean, and 2) that portion of Garrett County draining to the Ohio River Basin.)

Impact of Stormwater Runoff

  1. Declining water quality - storm water brings pollutants and sediment into water bodies.
  1. Diminishing groundwater recharge and quality - development creates impervious surfaces that prevent natural recharge. Net decrease in groundwater recharge rates can be expected in urban watersheds. During prolonged periods of dry weather, streamflow sharply diminishes. Urban land uses and activities can degrade groundwater quality if storm water runoff is directed into the soil without adequate treatment. Certain land uses and activities are known to produce higher loads of metals and toxic chemicals - designated as "stormwater hot spots."
  1. Degradation of stream channels - after development,bothfrequency and magnitude of streamflows increases dramatically. Stream bed and banks exposed to highly erosive flows more frequently and for longer periods, resulting in severe bank erosion and habitat degradation.
  1. Increased over bank flooding - flood events that exceed the capacity of the stream channel spill out into adjacent floodplains. Termed “overbank floods”and can damage property and downstream drainage structures e.g. culverts, swales.
  1. Flood plain expansion- flooding can be very destructive and can pose a threat to property and human life. Floodplains are natural flood storage areas and help to alleviate downstream flooding.

Relevancy to Maryland a growing State – Projected growth will result in about 670,000 new Maryland households between 2000 and 2030. If land is developed under current land-use patterns, more than 650,000 acres (about 10% of Maryland's total land area) could be converted from farm, forest and other rural uses to residential and other urban uses. As more development occurs, there is a greater risk of encroachment on water supply sources because of the greater impervious cover.

More important for this discussion, development of increasing amounts of impervious surfaces reduces recharge, degrades water quality and impairs streams. Smart Growth principles of development could reduce amount of acreage lost to about 150,000 acres, about a third of what is projected under current land use patterns. (For purposes of this exercise, Smart Growth means planning development to optimize use of public fund and protection of environment. An example would be siting a new development within an area served by existing water and wastewater treatment facilities. As opposed to developing an area now in agriculture or forest that must be serviced by wells and on site treatment facilities. Public funding in generally available to expand the existing facilities.)

ADDENDUM (what I left out)

Common pollutant found in storm water runoff

▪Nutrients, especially phosphorus, e.g. excessive lawn fertilizer

▪Suspended solids from wash off of particles that are deposited on impervious surfaces and erosion of stream banks and construction sites.

▪Organic-carbon from organic matter decomposing

▪Bacteria – causing closure of beaches and shellfish beds; also increasing cost of treating drinking water, e.g. pet waste, geese

▪Hydrocarbon – vehicles leaking oil and grease

▪Trace metal – cadmium, copper, lead, zinc

▪Pesticides

▪Chlorides (salt)

▪Trash

Definition of floodplains - level areas bordering streams and rivers. Generally defined as the land area within the limits of the 100 year storm water elevation. Maryland law states that the 100 year floodplain is considered "waters of the State". an important management and regulating tool not only for regulating development, but also for establishing flood insurance rates by the Federal Emergency Management Agency (FEMA). Floodplains are natural storage areas and help to alleviate downstream flooding. Floodplains are very important habitat areas, encompassing riparian forests, wetlands, and wildlife corridors. All local jurisdictions in Maryland now restrict or even prohibit new development in the 100-year floodplain. Development sharply increases the peak discharge rates associated with the 100-year design flows. As a consequence, elevation of a stream's 100-year floodplain becomes higher and the boundaries of the floodplain expand. In some instances, property and structures that had not previously been subject to flooding are now at risk. The 100 year storm means the size storm that statistically has a 1% chance of occurring in any given year. In this area a storm of about 7.5 inches in 24 years. In comparison a 1 year storm statistically has a 100 % chance of occurring in a given year, in this area a storm of about 2.7 inches in 24 hours. Important – we are talking about statistical principles used for planning purposes – in reality, we can have back-to-back 100 year storms.

Significance of Imperviousness - Throughout discussion of management techniques, there is emphasis on minimizing impervious cover which is any material limiting the percolation of water into the sub surface. Generally, stream quality and watershed health diminish when impervious cover exceeds 10% and becomes severely degraded beyond 25%.

POINT, NON-POINTSOURCES OF POLLUTION

Point Source - any discernible, confined and discrete conveyance, including any pipe, ditch, channel, tunnel, etc. from which pollutants are or may be discharged. Examples include

  1. discharges from wastewater treatment plants.
  2. concentrated discharges from factories and industrial activities,
  3. discharges from confined animal feedlot operation,
  4. discharges from Municipal Separate Storm Sewer Outfall Systems (MS4s).

MS4 permits are applicable in heavily urbanized jurisdictions where discrete storm water conveyances exist. The Maryland Department of the Environment (MDE) has been issuing MS4 permits required under the National Pollutant Discharge Elimination System (NPDES) to 10 populated districts in the State (Anne Arundel, Baltimore, Carroll, Charles, Harford, Howard, Frederick, Montgomery, PG, Baltimore City, and to the Maryland State Highway Administration. Permit conditions include developing and maintaining programs to control storm drain system pollution (i.e. point source). Permits will require restoration of 20% of its impervious surface area not already treated to the maximum extent possible (MEP). This in addition to the 10% required in previous permits, brings the total retrofit target to 30% by 20l7. In the second phase of the program, the 20% restoration requirement will be applied to 65 smaller municipalities and State and federal properties. Estimate cost of $3+billion for the interim target strategy (2017) and $6+ billion for the final target strategy (2025).

Point sources are regulated through the NPDES Program under direction of EPA although much of the day-to-day work is delegated to the State.

Non-pointSource Pollution - contamination that occurs when rainwater, snowmelt or irrigation moves over surfaces picks up and carries away natural and human-made pollutants and deposits them into lakes, rivers, wetlands, coastal waters and ground water. Characteristics of non-point sources of pollution:

  1. Contributory contaminants and sources are diffuse and varied
  2. -Pollutants discharged over a relatively wide land area.

Important Point - When urban stormwater pollutants are being addressed under an MS4 permit, considered a point source. Otherwise considered a non-point source.

INSTITUTIONAL ASPECTS

Erosion and Sediment Control

  1. l. Law written in 1970 following earlier decision that sediment is a pollutant.
  2. Law requires preparation of erosion and sediment control plans,primarily in urban areas to avoid pollution during construction.
  3. Applicants must submit proposed development plans to Soil Conservation Districts (SCDs) for approval. SCDs are independent entitiesof State government. Local grading permits contingent on SCD approval of the erosion and sediment control plans.
  4. Projects under 5,000 square feet and most agricultural projects exempt.
  5. MDE enforces - has delegated authority to 14 counties, 8 municipalities, and the Washington Suburban Sanitary Commission.

Important - SCDs, traditionally dealing with agricultural activities, taking on a major urban activity

Stormwater Management

  1. Current state law enacted 2007. Implementation by local governments with MDE oversight.
  2. Most recent regulations (2009) provide for storm water management under Environmental Site Design - similar to Low Impact Development (to be discussed in more detail)

NPDES Permit governing Stormwater Management During Construction

  1. Federal requirement under Clean Water Act delegated to the State
  2. Required permit for almost all activities creating a land disturbance of more than one acre
  3. Includes requirements for erosion and sediment control during construction and a stormwater plan post construction.

ADDENDUM

Definition of stormwater management - manipulation of surface storm water runoff for the purpose of reducing or eliminating adverse impacts on water and land resources

DEVELOPMENT OF MARYLAND'S STORMWATER MANAGEMENT PROGRAM

The Stormwater Management Act of 2007: A State Perspective

Stormwater has received an enormous amount of attention over the last couple of years due in no small measure to increases in pollution to Maryland's water resources from new and existing development. Over the coming years, runoff, the pollution it carries, and the attention both garner will continue to increase due to the anticipated expansion of the State's population and the land changes that will accompany it. Managing increases in storm water, therefore, will be vital if the effects of this growth

on receiving streams, rivers, and Chesapeake Bay are to be mitigated. Ensuring that the storm water management associated with future development causes no increases in water quality impacts and at the same time improves current conditions seems quite insurmountable. Fortunately, Maryland has had a program in place"…to maintain after development, as nearly as possible, the predevelopment runoff characteristics."

The State's storm water management program has evolved significantly since the original statute was passed in 1982. What began as a smaller scale flood control program using dry ponds and mandated infiltration has in 30 short years (1982-2012), developed into a rather complex science replete with complicated designs, specialized construction techniques, and a want for sophisticated monitoring schemes. In this time period much has been learned regarding how best to administer an effective stormwater management program. Some lessons came through research, monitoring, and experience; others came from the hindsight gained by mistakes made. Examples are numerous.

Increases in runoff volume, peak discharge, and velocity occur after development. The original storm water management program included the construction of traditional flood control detention basins to provide storage and a slow release of excess storm water to receiving stream stems. Detention basins were designed initially to mitigate the flooding impacts from large rainfall events like the 2-year and 10- year frequency storms. Unfortunately, time and experience proved this strategy to be flawed because stream channels were exposed to prolonged erosive flow conditions and the basins themselves provided little or not pollutant removal.

Programmatic weaknesses taught additional valuable lessons. Well-intentioned regional storm water policies failed due to unmanaged development runoff above large facilities that sometimes never got built. Also, the need for better construction plan quality and more vigilant initial and follow up inspections of stormwater management systems became apparent. The systems constructed were being left in the hands of homeowners' associations who were then strapped with expensive, long-term maintenance obligations. These have all pushed Maryland's storm water management program to become more effective both technically and administratively.

Significant changes have been made to the State's law, regulations, and policies to address the knowledge gained as implementation has progressed. High infiltration practice failure, varied and misused local storm water management waiver policies, and nonspecific water quality requirements caused major revisions to the original regulations and the development of the "2000 Maryland Stormwater Design Manual" (Manual). While serving as a national template for guiding program administration, the Manual altered design philosophies to encourage managing runoff based on capturing more frequent, channel-defining storm events. Also developed were groundwater recharge and water quality volume control obligations based on project imperviousness and soil conditions. Finally, the Manual introduced nonstructural or low impact techniques to be used as credits toward the runoff volumes required to be contained by more conventional facilities like ponds and wetlands. These changes have forced the State's storm water community to consider runoff control as part of initial site planning and design. Moreover, the Manual and accompanying regulations helped further refine a rather well established storm water management program.

Presently, another opportunity exists to improve Maryland's storm water management program came about with the passage of the Stormwater Management Act of 2007. Among other things, the Act requires that regulations be developed to promote "environmental site design" as much as possible. This in effect will not only expand on the techniques and credits first introduced in the Manual in 2006, but also alter design philosophies once again. Environmental site design will increase attention on how best to "…maintain after development…the predevelopment runoff characteristics." It is yet another step in the evolution of Maryland's storm water management program. With the Stormwater Management Act of 2007, Maryland mandated that all new development be designed under principles of Low Impact Development (termed Environmental Site Design or ESD)

Clarification of Terminology - The Maryland Stormwater Program, as mentioned previously, is built around the principle of Environmental Site Design to the Maximum Extent Possible (ESD to the MEP). In other jurisdictions, the terminology Low Impact Development is the Terminology used. While not identical terms, for purposes of this exercise, consider the two terms interchangeably. Since Pennsylvania is the host State for this year's National Environthon, and it uses LID, we will use that terminology.

LOW IMPACT DEVELOPMENT

LID Comprises a set of approaches and practices that are designed to reduce runoff of water and pollutants from the site at which they are generated. By means of infiltration evapotranspiration, and reuse of rainwater, LID techniques manage water and water pollutants at the source and thereby prevent or reduce the impact of development on rivers, streams, lakes, coastal waters, and ground water.

LID is an approach to land development (and re-development) that works with nature to manage storm water as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing imperviousness to create functional and appealing drainage practices that treats storm water as a resource rather than a waste product. There are many practices that have been used to adhere to these principles such as bioretention facilities, rain gardens, vegetated rooftops, rain barrels, and permeable pavements. By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed. Applied on a broad scale, LID can maintain or restore a watershed's hydrologic and ecological functions.

Goal of LID - using small scale storm water management practices, non-structural techniques and better site planning, to mimic natural hydrologic runoff characteristics and minimize the impact of land development on water resources includes;

  1. Optimizing conservation of natural features (drainage patterns, soil, vegetation)
  2. Minimizing impervious surfaces;
  3. Slowing down runoff to maintain discharge timing and to increase infiltration and evapotranspiration - maintain 100% of the average annual predevelopment groundwater recharge volume;
  4. Minimize pollutants in storm water runoff from both new development and redevelopment; and
  5. Using non structural practices or innovative technologies approved by MDE.

LID (ESD) Practices, Techniques