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Constantine Yapijakis and Maria Terasa Llorente The Cooper Union, School of Engineering, New York, NY 10003, USA Abstract Precipitation of all types falls on industrial sites and, in so doing, transports chemicals and inert solids to other parts of the environment. Any industrial facility will have some contamination on all surfaces, including roof, parking lots, storage facilities, roads, sidewalks, and dirt or grassy areas. Because all substances are soluble, to some extent, in water, any chemical substances in either liquid or solid form will become dissolved and will either percolate into the ground or be carried with the rainfall runoff. Some particles that are not dissolved will be carried along with the runoff, and some amount of gases will be dissolved in the runoff. Most, if not all, of that which percolates into the ground will eventually join the groundwater. The quality and, in some cases, the quantity of the water that leaves the industrial site, whether via overland flow to surface waters or via percolation into the groundwater, is of importance in the context of compliance with environmental regulations. More to the point, the quality and quantity of the stormwater management, as it relates to a pollution prevention program, the design of collection and treatment facilities, and regulatory compliance monitoring. Federal regulation of stormwater originated with the "1987 Clean Water Act" amendments that established the authority for the U.S. EPA to develop a phased approach to stormwater discharge permitting and management. Two stormwater rules followed in 1990 and 1992: the "stormwater application rule" and the "stormwater implementation rule". The stormwater application of November 1990 identified the types of facilities subject to permitting under the National Pollutant Discharge Elimination System (NDES) program (found at "CFR Part 122"), and the stormwater implementation rule of April 1992 described the requirements for NPDES permits. Introduction Precipitation of all types of falls on industrial sites and, in so doing, transports chemicals and inert solids to other parts of the environment. Any industrial facility will have some contamination on all surfaces, including roofs, parking lots, storage facilities, roads, and sidewalks and dirt or grassy areas. Because all substances are soluble, to some extend, in water, any chemical substances in either liquid or solid form will be come dissolved and will either percolate into the ground or be carried with the rain fall runoff. Some particles that are not dissolved will be carried along with the runoff, and some amount of gases will be dissolved in the runoff. Most, if not all, of that which percolates into the ground will eventually join the groundwater. The quality and, in some cases, the quantity of the water that lives industrial site, whether via overland flow the surface waters or via percolation into the groundwater, is of importance in the context of compliance with environmental regulations more to the point, the quality and quantity of the storm water runoff before it lives the site is the subject of the storm water management, as it relates to a pollution prevention program, the design of the collection and treatment facilities, and regulatory compliance monitoring. Federal Storm Water Regulations Federal regulation of storm water originated with the 1987 Clean Water Act amendments that established the authority for the U.S. EPA to developed a phased approach to storm water discharge permitting and management. To storm water rules follow in 1990 and 1992: The "Storm water application rule" and the "storm water implementation rule". The storm water application rule of November 1990 in identified the types of facilities subject to permitting under the National Pollutant Discharged Elimination System (NPDES) program (found at 40 CFR Part 1229), and the storm water implementation rule of April 1992 describe the requirements of NPDES permits. Phase I of the storm water application rule applicable to heavy industrial discharges, as well as large and medium municipal separate storm sewers and operators of large construction sites. Industrial facilities are required to comply with the storm water rules if they meet the following criteria:
· If the facility falls within one of the following categories Either engaged in industrial activity; Already covered under an NPDES permit; Identified by the EPA as contributing to a water quality violation
· Discharges of storm water to municipal sewer systems that are combined storm water and sanitary sewers; · Discharges the storm water to ground water. Multi-Sector General Permit The Multi-Sector General Permit (MSGP) is the simplest from of NPDES permit coverage that industrial facilities can obtain, although there are circumstances that would cause a facility to be ineligible for MSGP coverage. Industrial facilities that have activities covered under one or more of the industrial sectors in the MSGP are eligible for coverage. To obtain MSGP coverage, the facilities must submit a Notice of Intent (NOI) for coverage and prepare and implement a Storm Water Pollution Prevention Plan (SP3). The MSGP contains industrial-specific requirements for storm water monitoring, reporting, and best management practices (BMP's) to minimize contamination of runoff. Individual Permit The Individual Permit requires the preparation and submittal of NPDES forms 1 and 2F, which request specific information about the facility, the industrial operations, and the results of storm water sampling, analysis, and flow measurement. A facility-specific Individual permit is issued by NPDES permitting authority and typically contains discharges limits, monitoring, reporting requirements, and may require implementation of BMP's or pollution prevention measures. Because of the backlog of applications and lengthy application review and permit writing process for Individual permits, permitting authorities typically recommend that discharges seek coverage under the MSGP. Construction General Permit The Construction General Permit is applicable to construction projects at industrial facilities that disturb one or more acres of land area. The permitting process is the same as for the MSGP: submittal of an NOI for coverage an implementation of an SP3 that focuses BMP's during construction. Storm Water Pollution Prevention Plan (SP3) Amount the important requirements of the MSGP is the development and implementation of an SP3. The goal of the Sp3 is to reduce or eliminate the amount of pollutants in storm water discharges from an industrial site. The SP3 must be developed with input from a designated Pollution Prevention Team. The SP3 must identify all potential pollutant sources and include descriptions of control measures to eliminate or minimize contamination of storm water. The SP3 must contain the following:
· Identification of the manufacturing or other activities that take place within each area; · Identification of the potential sources of pollutants within each area; · An inventory of materials that can be exposed to storm water; · An estimate of the quantity and type of pollutants likely to be contained in the storm water runoff; · A history of spills or leaks of toxic or otherwise hazardous material for the past three years. Best Management Practices (BMP's) must be identified. BMP's should include good housekeeping practices, structural control measures, a preventive maintenance program for storm water control measures, and procedures for spill prevention and response. As needed, traditional storm water management controls, such as oil/water separators and retention/equalization devices must also be included.
· A certification of Non-storm water discharges. The facility must have piping diagrams that confirm no Non-storm water connections to the storm sewer. Otherwise, all outfalls must be tested to insure that there are no connections of sewers that carry other them storm water. · A record keeping system must be developed maintained, as well as effective program for training employees in matters of controls and procedures for pollution prevention. Measures and facilities to prevent contamination of groundwater should be developed concurrently with those that have the purpose of protecting against surface water contamination. The most important are listed below:
· Installation of fool-proof automatic shut-off devices to prevent spills from overflowing tanks; · Alarms; · An aggressive preventive maintenance program to prevent occurrence of leaks; · Control of particulate and aerosol emissions and routine cleaning of all surfaces on the industrial site Stormwater Segregation, Collection and Retention The collection system for contaminated runoff consists of rain gutters, catch basins, pumping stations, open channels, and pipes. This system must always be well maintained, clean, and free of leaks. Easy access to the collection system for sampling and analysis should be designed and built into the system. It's volume should be minimized by careful segregation from uncontaminated storm water since this water undergoes retention and treatment. Careful segregation will also maximize the concentration of contaminants because the quantity of contaminants at a given industrial site at given time is fixed by the circumstances and events that have occurred before the storm event. Therefore, the smaller the amount storm water in which the contaminants are dissolved or suspended, the more concentrated they will be. Control of the quantity of the storm water discharges is possible only if effective segregation, collection, retention, and treatment facilities are in use. The effectiveness from both acostand physical perspectives depends on proper design. Opportunities for segregation of clean runoff from contaminated runoff should be exposed as the first step in developing and effective storm water management program. Source segregation can be effective in reducing the volume of runoff to be collected and treated. The sizes of the collection, retention and treatment facilities are derived from precipitation records and selection of a design storm. It is also necessary to include within the design of the storm water management facilities provisions to prevent damage the those facilities or violations of permits since the concept of a design storm event implies periodic failure. Design Storm The 25-year, 24-hour storm event has been shown to be an appropriate design basis for storm water management facilities for an industrial plan when conventional pollutants are the only substances of concern. A 50-year or 100-year storm would be more appropriate in situations where PCB's or other toxic substances are potential pollutants. The capacity of the retention device is determined by the total volume of runoff calculated by the rational method or another more sophisticated runoff modeling procedure. The peak runoff rate is used to size the collection and piping, ditching, pumping, or other conveyance facilities. In any given year, there is a 4% probability that the 25-year storm will be exceed. A type of risk assessment or alternatives analysis should be carried out the determine if the benefits of designing for a storm event that would yield a greater volume and/or peak flow rate outweigh the risk of an overflow and, potentially, a permit exceedance. Factors to be considered in such a risk assessment include the water quality standards of the receiving water, the discharge permit limits, and the potential enforcement consequences. Storm Water Retention Storm water retention facilities retain contaminated storm water until it can be treated to concentration limits specified in the appropriate discharge permit or to quality characteristics required for use of the process makeup water in the industrial plant. Retention can be accomplished in lined, earthen basin or in above or belowground concrete or steel tanks. An industrial plant in a non-urban location having large areas of unused land would consider the cost effectiveness of a lined, earthen basin first. On the other hand, a plant in urban location with limited available unused land might first consider an above-or belowground concrete basin. Additional factors that must be included in sizing the storm water retention facility are the following
· The rate at which water is taken out of the basin as it related to the probability of another storm event taking place very soon after the design storm has occurred. References . ASCE Journal of Water Recourses Planning and Management . "Hydrologic Mitigation Using On-Site Residential Storm-Water Detention". Christopher P. Konrad and Stephen J. Burges MAR/APR 2001 Vol. 127, No 2. . "Determining Urban Storm Water BMP Effectiveness" Eric W. Strecker, Marcus M. Quigley, Ben R. Urbonas, Jonathan E. Jones, and Jane K. Clary. MAY/JUNE 2001 Vol. 127, No 3 . "Are Best-Management-Practice Criteria Really Environmental Friendly". Larry A. Roesner, Brian P. Bledsoe, and Robert W. Brashear. MAY/JUE 2001 Vol 127 No 3. . "Field Test of Grassed-Swale Performance in Removing Runoff Pollution". Shaw L. Yu, Jan-Tai Kuo, Elizabeth A. Fassman, and Henry Pan. MAY/JUN 2001 Vol. 127, No 3. . Woodard, F. Industrial Wastes Treatment Handbook. Pollution Engineering B. H. Publishing. 2001 |