Submitted to: EPA Region I Boston, Massachusetts Storm Water Quality Control in the Merrimack River Basin September 30, 1992 & Eddy J Ftc, BOSTON, MA O22o3-2 1 1 ------- Metcalf & Eddg An Air & Water Technologies Company September 30, 1992 Mr. Robert Morehouse United States Environmental Protection Agency, Region I JFK Federal Building Bostn, Massachusetts 02203 Subject: EPA Work Assignment 2-15: Storm Water Quality Control in the Merrimack River Basin Dear Mr. Morehouse: We are pleased to transmit the report entitled “Storm Water Quality Control in the Merrimack River Basin.” This report contains an overview of storm water and nonpoint source pollution issues, a review of control practices, a review of controls in four Merrimack River basin communities, recommended control practice improvements, and a summary assessment procedure for communities to follow in investigating their current storm water and nonpoint source controls. Thank you for the opportunity to work on this project. Very truly yours, David R. Bingham 30 Harvard Mill Square Wakeheld. MA 01880 Mailing Address. P0 Box 4043. Woburn MA 01888-4043 617-246-5200 FAX 617-245-6293 ------- TABLE OF CONTENTS Page LIST OF TABLES ii PURPOSE 1 OVERVIEW OF STORM WATER AND NPS POLLUTION ISSUES 2 Hydrologic Changes 2 Increased Pollutant Discharge 3 REVIEW OF CONTROL PRACTICES 9 Regulatory Controls 12 Source Controls 15 Structural Controls 18 EXISTING CONTROLS IN FOUR MERRIMACK RIVER BASIN COMMUNITIES 23 Regulatory Controls 24 Source Controls 36 Structural Controls 38 STRENGTHS AND WEAKNESSES OF IMPLEMENTATION 38 Flood Control 40 Storm Water Quality 40 General Site Development 41 RECOMMENDED IMPROVEMENTS 41 Regulatory Controls 42 SUMMARY OF ASSESSMENT PROCEDURE 46 Investigate Existing Regulatory and Source Control Measures 46 Investigate Recent Land Development 48 Assess Water Resources 49 Strengthen Controls 50 REFERENCES 51 I ------- LIST OF TABLES Page Table 1. Summary of NPS Pollutants, Sources, and Effects 4 Table 2. Pollutants of Concern for Various Water Resources 5 Table 3. Urban Storm Water Runoff Pollution Controls 10 Table 4. Storm Water and NPS Control References 11 Table 5. Existing Regulatory Controls 26 Table 6. Existing Source Controls 37 Table 7. Site Evaluation Checklist 39 11 ------- STORM WATER QUALiTY CONTROL IN THE MERRIMACK RIVER BASIN PURPOSE Storm water runoff and nonpoint source (NPS) pollution have been found to cause problems in water resources . throughout the United States. Because of the site specific nature of these problems and the ability of communities to control such pollution, effective solutions can come from actions taken at the local level. The purpose of this document is to provide municipal officials with information on storm water and NPS pollution control and how to improve existing regulations and practices to better accomplish such control. The document provides: • Background information on the effects of land development on storm water hydrology and pollution and their impact on various receiving water resources • A brief description of various types of control measures used to prevent and remove pollution from storm water runoff • A descnption of the current regulations and practices that address storm water pollution in four Merrimack River basin communities • Recommendations to strengthen regulatory requirements and source controls for storm water pollution control • A summary of the assessment procedure used so that other communities may investigate and strengthen their storm water control regulations and practices. In developed areas it is difficult, expensive, and time-consuming to construct pollution controls once a storm water pollution problem already exists. It is more cost-effective to prevent potential pollution problems prior to the occurence of development or to implement controls during redevelopment. This document, therefore, emphasizes the importance of implementing storm water pollution controls as regulatory requirements rather than having to correct problems after the fact in existing developments. 1 ------- OVERVIEW OF STORM WATER AND NPS POLLUTION ISSUES Storm water and NPS pollution is derived from diffuse or widespread sources, is usually associated with rainfall, snow melt runoff, or percolation, and may lack an easily identifiable point of entry. To fully attain the beneficial uses identified for a community’s water resources, implementation of effective storm water and NPS pollution controls is often necessary. NPS and storm water pollution are inherently difficult to address because of the large number and types of sources, the quantity and impacts of which are difficult to assess. The best solutions stress management (rather than treatment) techniques, with reIiance on local control measures. At the federal level, EPA is starting to address storm water runoff pollution through the National Pollution Discharge Elimination System (NPDES) permit program. Municipal storm water runoff is now a permitted point source if it is derived from medium or large municipalities (greater than 100,000 population); however the trend is to regulate storm water runoff from smaller and smaller communities. Within existing regulatory authority, communities already have the ability to control impacts from storm water and NPS pollution. This is because land development and intensive land uses lead directly to many of the problems associated with storm water and NPS pollution control. These problems can be divided into two basic categories: hydrologic changes and increased pollutant transport. Hydrologic Changes When precipitation contacts the ground surface, it can take several paths. These include returning to the atmosphere by evaporation or evapotranspiration, infiltration into the ground surface, retention on the ground surface (,ponding), and traveling over the ground surface (runoff). Altering the surface that precipitation contacts alters the fate and transport of the water. Land development replaces permeable surfaces with impervious surfaces (roof tops, roads, sidewalks, parking lots, etc.) designed to remove rainfall as quickly as possible. Increasing the proportion of paved areas decreases the infiltration and evapotranspiration paths of precipitation, thus increasing the amount of precipitation leaving the area as runoff. In 2 ------- addition, the intensity of runoff is magnified by urban development and increases in impervious surfaces. When overland flow through natural vegetation is replaced by storm drainage systems, the time it takes for storm water to travel to a receiving water is reduced. Changes to hydrology expected for a moderately developed watershed include (Shueler, 1987): • Increased peak discharges and frequency of high flows • Increased volume of storm runoff • Decreased time for runoff to reach the receiving water • Increased frequency and severity of flooding • Reduced flow during periods of prolonged dry weather • Greater runoff and water velocity during storm events Each of these changes leads to increased pollutant transport and loading to receiving waters. As peak discharge rates increase, erosion and channel scouring become greater problems. The eroded sediments also carry nutrients, metals, and other pollutants associated with them. In addition, increases in runoff volume result in greater discharges of pollutants. These and other effects result in increasing pollution problems as increased development occurs. Increased Pollutant Discharge In addition to the effects of hydrologic changes on storm water pollution loads, land development leads to an increase in pollutant loadings in runoff. The increased pollutant loadings result from a combination of higher total and peak runoff volumes caused by the hydrologic changes discussed above, and an increase in the concentrations and amounts of pollution associated with developed land. Table 1 (EPA, 1992) lists the primary categories of pollutants that result from urban runoff, parameters typically monitored for each category, potential pollutant sources, and associated potential effects. 3 ------- TABLE 1. SUMMARY OF NPS POLLUTANTS, SOURCES, AND EFFECTS ; ;: j CATE( O Y . PARAMEI RS BL SO R9 Solids Organic and Inorganic . TSS Turbidity Dissolved Solids Urban/Agricultural Runoff CSOs Turbidity Habitat Alteration Recreational & Aesthetic Loss Contaminant Transport Navigation/Hydrology Nitrate Nitrite Ammnnia Organic Nitrogen Phosphate Total Phosphonis Urban/Agricultural Runoff Landfills,Septic Fields Atmospheric Degradation Erosion Surface Waters Algal Blooms Ammnnia Toxicity Groundwater Nitrate Toxicity Total Coliforms Fecal Coliforms Fecal Streptococci Viiuses Urban/Agricultural Runoff Septic Systems CSOs Boat Discharges Domestic/Wild Animals Ear/Intestinal Infections Shellfish Bed Closure Recreational/Aesthetic Loss BOD COD TOC Urban/Agricultural Runoff CSOs Landfihls,Septic Systems DO Depletion ‘Odors Fish Kills Toxic Trace Metals Toxic Organics Pesticides/Herbicides Underground Storage Tanks Hazardous Waste Sites Landfills Illegal Oil Disposal Industrial Discharges Lethal and Sublethal to hnmnnc and other organisms 4 ------- The predominant sources of runoff and NPS pollution include urban storm-generated runoff, construction, and agricultural activities. Additional sources include atmospheric deposition, material storage, highway and bridge maintenance, illegal dumping or disposal, auto salvage yards, vehicle washing and processing areas, snow dumping areas, utility right-of-ways, surface runoff from ifiling stations, sediments (either through resuspension or through release of pollutants from undisturbed sediments), sewer system leaks, domestic and wild animals, litter from natural vegetation, and non-storm water discharges to separate storm drainage systems (Morehouse, 1988). For municipalities, urban storm-generated runoff in industrial, commercial, and residential areas as well as construction activities represent the most prevalent sources. Outlying agricultural activities can also play a role in some areas. The effects of storm water and nonpoint source pollutants are different for different water resource types. The pollutants of concern to a given municipality will, therefore, depend on the types of water resources present in that community and the desired uses of those waters. Table 2 indicates the water resources that are potentially impacted by various runoff and nonpoint source pollutants. TABLE 2. POLLUTANTS OF CONCERN FOR VARIOUS WATER RESOURCES Drinking Water Stream River Wetland Lake Estuary Suspended Solids and Sediment • • • I S • Nutrients S I S S I Pathogens S I I I Oxygen Demanding Substances I I S S Toxics I S I S I I Sodium and Chloride S 5 ------- Suspended Solids Suspended solids (sediment) are made up of particulate matter that settles and fills in the bottoms of ditches, streams, lakes, rivers, and wetlands. Sediment loading occurs primarily from soil erosion and runoff from construction sites, urban land, agricultural areas, and stream banks. Although some sedimentation is natural, construction, farming, and urbanization can accelerate the process by increasing the rates of storm water runoff, by removing cover vegetation, and by changing slopes and affecting soil stability. Increased runoff from developed areas transports solids from various sources, including soil erosion, deposition from wind erosion, litter (both manmade and naturally produced), and road sanding. These solids also carry nutrients, metals, and other substances that can impact the water resource and aquatic life. Sedimentation can have substantial biological, chemical, and physical effects in receiving waters. Suspended solids can make the water look cloudy or turbid, diminishing the aesthetic and recreational qualities of the water body while reducing the growth of algae and submerged aquatic vegetation. Once the solids settle out and become deposited as sediment, they can smother bottom dwelling species and act as a sink for pollutants which can later resuspended. Since solids can cause problems in either the suspended or deposited state, they impact all water resource types. Nutrients The nutrients that are of primary concern to water quality and that are present in high concentrations in storm water are nitrogen and phosphorus. Nutrients are associated with agricultural and urban runoff, atmospheric deposition, leachate from landfills and septic systems, and erosion. Nutrient additions can .result in eutrophication, or.over enrichment of receiving waters, which can cause excessive algal growth. In many cases, nutrients contributed from urban runoff originate from chemical fertilizers and thus are in a dissolved form readily utilized by algae in the receiving waters. Phosphorus is generally the most important nutrient in freshwater because it is growth-limiting, while nitrogen tends to limit growth in marine waters. 6 ------- Nutrient enrichment cai result in severe algal blooms, either in the water column or in stream and lake beds, that can cause unpleasant odors and otherwise detract from aesthetic value. High densities of certain algal species can result in taste and odor problems in drinking water from reservoirs. More seriously, some marine algal species contain toxins that can be harmful to humans eating affected fish or shellfish. Also, eutrophication can result in depletion of dissolved oxygen in the water column. Generally, nutrients cause problems in slow moving waters that allow for the development of algal blooms, such as lakes, coastal areas, large rivers, and wetlands. Therefore, they are generally not considered a problem in fast moving urban streams, except as such streams contribute nutrient loading to other water resources. Pathogens Pathogens are bacteria, protozoa, and viruses that can cause disease in humans. Although not pathogenic themselves, the presence of indicator bacteria, such as coliform, fecal coliform or fecal enterococci are used as indicators of pathogens and of potential risk to human health. Potential health risks are associated with primary and secondary contact recreation, such as swimming, and with consumption of contaminated fish and shellfish in areas affected by urban runoff. Bacterial and viral pathogens are for the most part attributed to livestock in agricultural areas and runoff in urban areas. Other sources of these organisms can include failed septic systems, landfills, or combined sewer overflows and unauthorized sanitary sewer cross connections in storm drains. Like nutrients, pathogens generally cause water quality degradation in slow moving waterways and resources used by humans for primary and secondary contact recreation or sheilfishing. Pathogens are, therefore, primarily considered pollutants of concern in drinking waters, slow moving rivers, lakes, and estuaries; Pathogen contaminated discharges to wetlands or fast moving urban streams are typically less important due to the lack of recreational and fishing uses of such waters. 7 ------- Oxygen-Demanding Matter As discussed above, microorganisms consume organic matter that is deposited in water bodies by storm water runoff. In the process, oxygen is removed from the water. Organic enrichment is caused by agricultural and urban runoff, combined sewer overflows, and leachate from septic tanks and landfills. A sudden release of oxygen-demanding substances into a waterbody during a storm can result in the total depletion of oxygen and in fish kills. Organic enrichment can also have long-term effects on sediment quality, increasing organic content and the tendency of sediments to deplete surface waters and benthos of oxygen (referred to as sediment oxygen demand (SOD]). The solid and dissolved organic content of water and its potential to deplete oxygen is measured by its biochemical oxygen demand (BOD). This oxygen demanding matter is primarily a concern in waterbodies that support aquatic life, such as rivers, lakes, and estuaries. It is, therefore, generally a less important considerations for fast moving urban streams and wetlands. Toxic Pollutants Toxic pollutants include trace metals and organic chemicals. Heavy metals in urban runoff can result from the breakdown of products such as trash cans and car bumpers, fallout from automobile emissions, and other metal products. Potential sources of toxic pollutants include vehicular residues, industrial areas, landfills, hazardous waste sites, leaking underground and aboveground fuel storage tanks, and agricultural areas at which chemicals are used. Other potentially toxic compounds in storm water and NPS pollution include oil and grease from vehicles and construction equipment. These compounds are generally in runoff from roads, parking lots, service areas, and construction sites, and can be a constituent of landfill leachate. Oil and grease products can be adsorbed to sediment particles and be deposited in the bottom sediments. These compounds can be toxic to aquatic organisms and can bioaccumulate in fish and shellfish, potentially resulting in toxic effects to humans eating this tainted food. Because of the potentially acute and chronic effects of toxic pollutants, efforts should be made to appropriately limit their discharge to all water resource types. 8 ------- Sodium and Chloride Discharges of sodium and chloride to surface waters result primarily from road sailing operations during winter months and snowmelt during the early spring thaws. These discharges can affect the taste of drinking water supplies and be harmful to people on low sodium diets. Of secondary importance is its potential impact on salt intolerant plant species. However, the concentrations of sodium and chloride in runoff are typically small enough to not cause serious problems, especially in resources with continuous flushing (rivers and streams). Sodium and chloride discharges are, therefore, of concern in drinking water supplies and lakes. REVIEW OF CONTROL PRACTICES Because of the lack of funding for storm water pollution control activities as well as the difficulty in implementing controls for multiple source types at many locations with intermittent (rainfall-driven) discharges, the emphasis of storm water pollution control measures is typically on nonstructural controls and low-cost structural controls designed to prevent pollution. Nonstructural controls include regulatory measures that prevent NPS pollution problems by controlling land development, and source controls that seek to reduce pollutant buildup or lessen its availability for wash-off during rainfall. Low-cost structural controls remove pollutants from runoff by using natural processes, such as settling, filtering, biological breakdown, or uptake by vegetation, or using small facilities with no mechanical or electrical equipment, such as water quality inlets and oil and grease traps. Depending on the pollutant control mechanisms they use, storm water runoff and NPS pollution control practices are divided into the following categories: • Regulatory (land use) controls • Source controls • Structural controls - Detention facilities - Infiltration facilities 9 ------- - Vegetative practices - Filtration practices - Water quality inlets Table 3 lists the most commonly used urban storm water controls. This section provides a brief description of some of the more important controls. More detailed references, such as those shown in Table 4, should be consulted before selecting, designing, and implementing controls. TABLE 3. URBAN STORM WATER RUNOFF POLLUTION CONTROLS Regulatory Controls Detention Facilities Land Use Regulations Extended Detention Dry Ponds Protection of Natural Resources Wet Ponds Land Acquisition Constructed Wetlands Source Controls Infiltration Facilities Street Sweeping Infiltration Basins Catch Basin Cleaning Infiltration Trenches/Dry Wells Fertilizer and Pesticide Management Porous Pavement Animal Waste Removal illicit Connection Identification and Removal Vegetative Practices Solid Waste Management Reduced Roadway Sanding and Salting Grassed Swales Filter Strips Filtration Practices Filtration Basins Sand Filters Water Quality inlets 10 ------- TABLE 4. STORM WATER AND NPS CONTROL REFERENCES Document Title Author Controls Induded Information Available Controlling Urban Runoff: A Schueler Detention General Descriptions Practical Manual for Planning and Infiltration Effectiveness Designing Urban BMPs, 1987 Vegetative Design Filtration Use Limitations Quality Inlets Maintenance Cost Examples Protecting Water Quality in Urban MPCA Source Control General Descriptions Areas, 1989 Detention Effectiveness Infiltration Use Limitations Vegetative Maintenance Quality Inlets Cost Examples Guide to NPS Control, 1987 EPA Source Control General Descriptions Detention Effectiveness Infiltration Cost Water Resource Protection Urban Land Source Control General Descriptions Technology: A Handbook of Institute Detention Effectiveness Measures to Protect Water Infiltration Design Resources in Land Development, Vegetative Use Limitations 1981 Quality Inlets Maintenance Cost Urban Storm Water Management EPA Source Control General Descriptions and Technology: An Assessment, Collection System Design 1974 Storage Maintenance Treatment Use Limitations Coastal Nonpoint Source Control EPA Source Control General Descriptions Program: Management Measures Infiltration Effectiveness Guidance - Draft, 1992 Vegetative Design Filtration Use Limitations Quality Inlets Maintenance Cost Examples 11 ------- Regulatory Controls Urbanization increases the amount of impervious land area, which, in turn, leads to increases in storm water runoff with its associated pollutants. Municipalities can prevent or reduce many of these pollution problems by implementing regulatory controls designed to reduce the amount of impervious area and to protect valuable resources. The major categories of regulatory controls include: • Implementing land-use regulations • Restricting development in valuable natural resource areas • Acquiring parcels of land or buffer zones to prevent development Following is a discussion of some common municipal regulatory practices that can be used to control storm water and NPS pollution. Estimates of pollution control that can result from implementing these controls are contained in a number of documents, such as those listed in Table 4. One table from a recent publication has been reproduced in Appendix A as an example of the type of information that is available. Land Use Regulations Land-use regulations can be used to encourage development patterns compatible with storm water runoff and NPS pollution control objectives. Land-use regulations can include zoning ordinances, subdivision and site plan regulations and review requirements, and environmental resource regulations such as wetlands protection. Zoning. Zoning ordinances specify the density and type of development that can occur. in given areas. Zoning density controls acreage requirements for certain land uses and associated setback, buffer, and lot coverage requirements. Zoning use directly and indirectly affects what types of pollutants may be stored or used on the site. Pollutant intensive uses can be restricted or eliminated in sensitive zones or allowed only under special permit approval. Zoning 12 ------- regulations can serve to address both the hydrologic and pollutant discharge concerns involved in new development. Examples of types of zoning practices designed to protect water bodies include: • Cluster Development : allowing structures in developments to be constructed close together to preserve open space. • Down-Zoning changing an established zone to a use that allows a lower level of density. • Phase-in Zoning : changing the zoning of a specific area over time, usually as inappropriate sites reach the end of their useful life. • Large Lot Zoning : requiring greater minimum acreage for development in certain locations • Conditional Zoning : allowing certain types of activities only under specified conditions that protect water quality. • Overlay Zoning : placing additional zoning requirements on an area that is already zoned for a specific activity or use. • Open Space Preservation : protecting open space and buffer zones in the community near waterbodies. • Performance Standards : permitting certain land uses, usually industrial activities, only if they meet specific performance criteria. Communities can utilize these zoning practices to ensure that land uses in specified areas of the municipality are appropriate given their proximity to nearby water resources. Implementing special zoning restrictions in especially sensitive areas, such as a water supply watershed, can serve to reduce development in the watershed and ensure that any development taking place is appropriate. Subdivision Review. When land is divided into separate parcels for development, communities, under Massachusetts State Law, require the developer to go through a subdivision review process. Parcels that have sufficient frontage on an approved public way are classified as 13 ------- “Approval Not Required” and do not go through preliminary and definitive plan review. All other proposed subdivisions must go through this review. During this review, municipalities can include requirements for drainage, grading, and erosion control and provisions for buffer areas, open spaces, and maintenance. In this way, municipalities can ensure that proper practices are designed into the development. Site Plan Review. Prior to development of certain activities, municipalities may require a site plan review process to ensure compliance with zoning, environmental, health, and safety requirements. In this review, developers are usually required to consider how site development will affect such concerns as traffic circulation, air quality, and ambient noise levels. Developers may also be required to submit information on the natural drainage characteristics of the site and plans for erosion control, the retention and protection of wetlands and water resources, and the disposal of construction-related wastes. However, criteria which can impact storm water and NPS pollution are not often specified in the site plan review regulations. Protection of Natural Resources. Municipalities can also protect water resources by restricting development in lands, such as floodplains, wetlands, stream buffers, steep slopes, and wellhead areas. By implementing special development restrictions in these areas, the potential for storm water and NPS pollution can be reduced. These protection practices usually take the form of special protection districts or overlay zones. Land Acquisition In addition to zoning and resource protection, municipalities can purchase land or obtain conservation easements within a watershed to control land development. In this way, valuable -. resources can be protected from the effects of development. Municipalities can acquire land to convert to parks or to maintain as open space; however, this can be a very expensive approach. 14 ------- Source Controls Source controls include nonstructural practices that can reduce the availability of storm water runoff and NPS pollutants. Some of the more common practices in current use in many municipalities use include: • Street sweeping and catch basin cleaning • Reduced fertilizer, pesticide, and herbicide use • Animal waste removal • Illicit connection identification and removal • Solid waste management • Reduced roadway sanding and salting Although effectiveness of these practices can be difficult to predict, the table shown in Appendix A indicates the general removal effectiveness expected from urban housekeeping (street sweeping and catch basin cleaning), fertilizer control and household hazardous waste collection. Street Sweeping and Catch Basin Cleaning Frequent street sweeping and catch basin cleaning can prevent the accumulation of dirt, debris, and their associated pollutants, and the subsequent deposition of these pollutants in storm drains and waterways. In most municipalities, these tasks are conducted at scheduled intervals. It has been shown that street sweeping results in significant pollutant reductions only if an intensive schedule (once or twice per day) is adhered to consistently. It is, however, not practical for communities to maintain this level of Street sweeping. In addition, catch basin cleaning has not been shown to result in significant pollutant reductions. Cleaning rates of twice per year are generally recommended. Although neither of these practices results in significant pollutant eii ival,regulai sfreet sweeping and catch basin cleaning can remove some of the large floatable litter that is unsightly in urban surface waters. 15 ------- Reduced Fertilizer. Pesticide. and Herbicide Use Fertilizers, pesticides, and herbicides washed off the ground during storms can contribute to water pollution. Generally, agricultural land uses are primarily responsible for these pollutants. However, some communities use these chemicals on park lands, and homeowners utilize them on their lawns. These can be sources of pollutants in urban areas. Controlling the use of these chemicals on municipal lands and educating the public can, therefore, help reduce nutrient and toxics concentrations from these fertilizers and pesticides. However, unless existing practices include significant fertilizer or pesticide use near waterbodies, minimal nutrient load reductions would occur. Animal Waste Removal Domesticated and wild animal wastes represent a source of bacteria and other pollutants that can be washed into surface waters by storm water runoff. These pollutants can be reduced by reducing the animal waste on paved surfaces. Municipalities can enact and enforce leash laws and pet waste cleanup ordinances. The effectiveness of these programs in reducing pollutant loads is difficult to assess and to implement, since it depends on voluntary actions by private citizens. It is anticipated that minimal pollutant load reduction would occur form this practice, except perhaps where large concentrations of pets exist. Illicit Connection Identification and Removal Unauthorized and inappropriate connections in drainage systems can cause continuous dry weather discharges of sewage or toxic materials and can exist for many different reasons. In the past, connector pipes between sanitary sewers and storm drains. migh.t h ve• been installed to relieve surcharging of the sewer system and prevent backups of sewage into homes and businesses. Connections from residential sanitary sewers or commercial and industrial floor drains also exist. Cross connections are common in municipalities that have undergone sewer separation. As new construction occurs, accidental connections to the wrong system can also 16 ------- occur. Because these cross connections are not typically documented, pollution resulting from them can be difficult to locate. Municipalities can, however, develop a program to locate and eliminate these connections. These programs are similar to infiltration/inflow studies conducted by municipalities on sanitary sewer systems. Detailed information on locating and eliminating these cross connections is available in a draft EPA document entitled “Assessment of Non-Storm Water Discharges into Separate Storm Drainage Systems” (Pitt, 1990). Solid Waste Management Most communities have programs to collect and dispose of solid waste in an effort to maintain clean streets and provide a service for local residents and businesses. Some communities provide added services during particularly high waste times. For example, some municipalities in the northern United States provide extra collection services during the fall to collect leaves. These waste collection practices, although designed for aesthetic reasons, can help to reduce pollutant discharge to surface waters. Actual reductions in loads, however, are difficult to predict. In general, any solid waste that is picked up and disposed of in a controlled manner will be less likely to enter a drainage system. Reduced Roadway Sanding and Salting In areas with freezing road conditions, sand and salt are used to improve driving conditions in the winter months. These can be washed off the roadways, however, and pollute receiving waters. The problem is exacerbated during spring snow melt and early spring rainstorms when most of these pollutants are available for transport. Limiting the use of chemicals for snow and ice control to the minimum necessary for public safety and utilizing proper equipment can reduce these problems. Also, deicing alternatives,such as calcium magnesium acetate (CMA), cãn be used in some cases, although they are expensive. 17 ------- Structural Controls Structural controls can be used to remove pollutants from runoff. In highly developed areas, regulatory controls are instituted mainly during the redevelopment process and source control practices may not be sufficient. In these cases, it may be necessary to retrofit structural controls into existing developments. In addition, structural controls can be implemented in undeveloped areas through regulatory requirements that specify their use. The approximate pollutant removals for various structural controls is indicated in the table in Appendix A. Similar tables and information are contained in the references cited in Table 4. Structural controls seek to remove pollutants from runoff through natural processes, such as settling, filtration, and vegetative uptake. Proper functioning of these practices depends on following strict design criteria and maintenance schedules. It is important that structural controls be regularly inspected and maintained. Common maintenance practices include replanting and mowing vegetation, removing accumulated sediment, and unclogging outlet structures. Detailed information on the design and maintenance of the following structural controls are contained in the documents listed in Table 4. Detention Facilities One of the most common structural methods for controlling storm water runoff is through the construction of ponds or wetlands to collect runoff, detain it, and release it to receiving waters in a controlled manner. Pollution reduction during the period of temporary runoff storage results primarily from settling of solids and their associated pollutants (nutrients, metals). Extended Detention Dry. Ponds. Many development projects have involved constructing dry ponds to control peak runoff. These ponds can also be used for pollution control, where the ponds are designed with structures to restrict the velocity and volume of runoff discharges. Dry ponds detain the runoff so that heavier particles settle, removing suspended solids. Vegetation in the dry ponds also provide pollutant removal through filtering and vegetative uptake. 18 ------- Although dry ponds remove suspended solids and their associated pollutants, they are less effective at removing dissolved pollutants and microorganisms. Wet Ponds. The design of wet ponds is similar to that of dry ponds except that a permanent pooi of water is maintained in the ponding area. Once the capacity of a wet pond is exceeded, collected runoff is discharged through an outlet structure or an emergency spillway. While the runoff is detained, settling of solids takes place. In addition, many wet ponds are vegetated with plant species, which can often remove pollutants, such as nutrients, from the runoff before it is discharged to the receiving water. The continuous ponding of water in wet ponds improves the pollutant removal process over that found in dry ponds. Constructed Wetlands. Artificially constructed wetlands may be effective in removing urban storm water pollutants and in flood attenuation. Proper design of artificial wetlands, including their configuration, proper use of pretreatment techniques to remove sediments and petroleum products, and choice of vegetation, is crucial to the functioning of the systems. Wetland systems also reduce runoff velocity, thereby promoting settling of suspended solids. Plant uptake accounts for nutrient removal as well as removal of a portion of the oil and grease and metals from runoff. In addition, plant material can serve as an effective filter medium, and denitrification processes can serve to remove nitrogen. Infiltration Facilities Unlike detention facilities that capture and eventually release storm water runoff to a surface water body, infiltration facilities permanently capture runoff so that it discharges into the ground water. Pollutant removal occurs primarily through filtration, which is effective at removing solids, those pollutants that adhere to solids; and bacteria. Infiltration is less effective at removing dissolved pollutants, such as nutrients and some metals. Infiltration Basins. Infiltration basins are similar to dry ponds, except that infiltration basins are designed to permanently capture all or part of the incoming flow. Flow entering an 19 ------- infiltration basin travels to the ground water through the soil. Infiltration basins provide storm water pollutant removal through both filtration and settling, but the primary pollutant removal mechanism is filtration. Infiltration basins are particularly effective in removing bacteria, suspended solids, insoluble nutrients, oil and grease, and floating wastes. They are, however, less effective at removing dissolved nutrients, some toxics, and chlorides. Infiltration Trenches/Dry Wells. These practices differ from inifitration basins because they are located below ground and usually must be built “off line” (only a specific volume of runoff enters an infiltration facility with the balance continuing along another path) because of the limited storage area they provide. Subsurface infiltration systems can consist of precast concrete structures with holes in the sides and bottom surrounded by washed stone. These structural controls use filtration as the primary pollutant removal mechanism, much like onsite wastewater treatment systems used in many communities. They effectively remove suspended sediments and floating debris, as well as bacteria, which are difficult to remove without disinfection. Infiltration practices are generally less effective at removing dissolved nutrients, such as nitrogen or other soluble contaminants, which can travel through ground water and be discharged to the receiving water. Porous Pavement. Paved roads and parking areas are major contributors to storm water runoff problems in urban areas because they increase watershed imperviousness. Porous pavement, however, allows water to flow through a porous asphalt layer and into an underground gravel bed. Using this porous pavement can, therefore, reduce runoff volume and pollutant discharge. This practice is used in areas with gentle slopes and is generally designed into parking areas that receive light vehicle traffic. These systems are, however, designed to remove only fine grained particles because coarse particulate pollutants can clog the pavement. In these systems, pollutant removal primarily occurs after the runoff has inifitrated into the underlying soils.... Vegetative Practices Urbanization results in the elimination of vegetation and increases in impervious area. 20 ------- Vegetative practices can be implemented in urban areas to decrease the impervious area and promote runoff infiltration and solids capture. These practices provide moderate to low pollutant removal and can be used for pretreatment for the removal of suspended solids from runoff prior to more intensive treatment by other practices. Grassed Swales. Grassed swales are channels covered with vegetation used to replace catch basin and pipe network systems for transporting runoff to surface waters. Storm water runoff flows through the grassed swale reducing runoff velocity and promoting the removal of suspended solids. Grassed swales remove pollutants through filtering by the vegetation and settling of solids in low flow areas. However, infiltration of the runoff and associated pollutants is probably the most important pollutant removal process. Because of these pollutant removal mechanisms, swales are most effective at removing suspended solids and their associated pollutants. They provide little removal of dissolved pollutants. Filter Strips. Filter strips are similar to grassed swales. Runoff enters these systems as overland flow evenly distributed across the filter strip. Because these systems can accept only overland sheet flow, they are usually used in conjunction with level spreading devices. Filter strips are most effective at removing pollutants such as sediment, organic material, and some trace metals. They are less effective at removing dissolved pollutants. Filtration Practices Filtration practices provide runoff treatment through settling and filtering through a specially placed layer of sand or other filtration medium. Flow enters the structure, ponds for a period of time, and ifiters through the media to an underdrain that discharges to a surface water. These practices attempt to simulate the pollutaht removal of infiltration practices using less land area. Filtration Basins. Storm water runoff diverted to a filtration basin is detained, allowed to percolate through filter media, and collected in perforated pipes, that transport the filtered runoff to the receiving water. These systems have been used extensively in Austin, Texas, showing 21 ------- good pollutant removal efficiencies and low failure rates. Pollutant removal in filtration basins occurs because of settling during the initial ponding time and filtering through the soil media. Sand Filters. Sand ifiters are similar to the filtration basins outlined above but are designed to reduce the amount of land required by building them below ground. These systems consist of a basin for settling of suspended solids and a filtration chamber. Runoff enters the basin and collects to the basin capacity. It then overflows into a sand-filled chamber that provides filtration and is discharged through an outlet pipe in the bottom. The use of sand filters for storm water runoff treatment is still experimental and has been implemented in a demonstration in the state of Maryland. Sand filters use the same pollution removal mechanisms as filtration basins and will provide similar pollutant removal. Initial removal of suspended solids occurs through settling in the basin and further treatment is provided by ifitration through the sand-filled chamber. Sand ifiters are particularly effective at removing suspended solids their associated pollutants. Moderate removal of bacteria can be expected, but these systems cannot provide removal of soluble pollutants such as nitrogen. Water Ouality Inlets Water quality inlets, also known as oil and grit separators, are similar to septic tanks used for removing floatable wastes in onsite wastewater disposal systems. These inlets provide removal of floatable wastes and suspended solids through the use of a series of settling chambers and separation baffles. These systems have been designed and used for many years, but storm water pollutant removal efficiencies are generally unknown. Given the limited pollutant removal expected from water quality inlets, they are usually used in conjunction with other structural storm water quality controls as pretreatment devices. They can be fairly effective at removing coarse sediments and floating wastes and can be used to pretreat runoff before it is discharged to infiltration systems or detention facilities. In this way, some of the routine maintenance required of structural controls, such as sediment removal and unclogging of outlet structures, can be reduced. Water quality inlets also can serve to capture accidental spills or illegal discharges that could potentially enter other treatment structures or surface waters. 22 ------- EXISTING CONTROLS IN FOUR MERRIMACK RIVER BASIN COMMUNITIES This section reviews the existing regulatory, source, and structural controls implemented in four communities in the Merrimack River basin. The four communities are: • Lawrence • Methuen • Newburyport • North Andover The City of Lawrence is densely developed with only a few parcels on which new development could occur (MVPC,1991). Since little future new development will occur, improvements in storm water pollution control will primarily result from changes to the regulations that impact redevelopment and substantial renovations and from improved source controls. In addition to these considerations, Lawrence is primarily served by a combined sewer system. Combined sewer pollution control is being addressed through the NPDES permitting program. However, storm water runoff controls can assist in reducing CSOs by reducing runoff volumes and the storm water pollutant load component of the combined sewer overflows. Methuen is a moderately developed town, covering about 23 square miles of which approximately 40 percent is developed. Residential development dominates the land uses within the town, although there are smaller amounts of retail and industrial activity. The center of the town is somewhat densely populated while the outlying areas are less developed, and are not served by sewers. Management practices for storm water control would need to be reviewed as to how well they address both new development and redevelopment projects. Newburyport is a moderately developed city located at the mouth of the Merrimack River. Most of the city is residentially developed, with commercial development located downtown and in the vicinity of the Route 95 interchange. Industrial activity occurs along the waterfront and in the industrial park near Route 1 on the Newburyport/Newbury line. Most of the city’s developable land has been developed, with the exception of some parcels near the Artichoke 23 ------- Reservoir Watershed on the West Newbury border. North Andover is primarily a residential community of which 25% is developed and another 24% is potentially developable (MVPC, 1991). Most of the developed area is in residential use, while significant portions of the open land are in public, wetland, and agricultural use. These communities were chosen because they represent a variety of levels of existing development, perceived levels of environmental awareness, and water resources to be restored or protected. The information contained in this section will be used as a basis for recommendations that can be used by these and other municipalities in the Merrimack River basin and elsewhere to improve control of storm water pollution. Regulatory Controls Land development is a major cause of increased problems related to storm water runoff—both quantity and quality—in growing urban areas. Therefore, by controlling and directing land development through existing and new regulations, communities can reduce the impacts of storm water runoff. However, in practice, the level of control existing in a community is related to the perceived need to control or prevent pollution in particular water resources, and the ability or willingness of the responsible government agencies to use their authority. As discussed earlier, communities can control development and its associated storm water runoff problems through zoning. Most communities have residential, commercial, industrial, and other zoning districts established that specify the types of development allowed and dictate requirements for building density, setbacks, lot coverage, landscaping, and drainage. Communities permit certain activities as a right in the zoning districts and. may also specify that certain activities are allowed in specific zones under special permit review. In order for these zoning districts to provide runoff pollution protection, however, they must be appropriate for the types of nearby water resources. Changing zoning districts and requirements for each district may, therefore, present opportunities to improve storm water runoff pollution control. 24 ------- The appropriateness of these changes, however, is very site specific. The areas of local regulations that generally relate to runoff control and were reviewed for this project are: • Subdivision Regulations • Special Permit and Site Plan Review • Wetlands Protection • Earth Removal • Special Zoning Controls Existing provisions of these regulations for each of the four communities are outlined in Table 5. These regulations can be used by local government entities to require storm runoff controls, reduce the level of impervious area, require the preservation of natural features, reduce erosion, or require other important practices. The major aspects of these regulations that are important for storm water control are described in the following paragraphs. These major aspects are used to organize the matrices in Table 5 so that the specific provisions of the regulatory practices in each of the four communities can be summarized. Runoff Ouantity Control Regulations addressing runoff quantity control can be used to reduce the effects of land development on watershed hydrology. Hydrologic control in turn results in pollution control. This can be accomplished through a number of requirements: • Open Space : By maintaining specified levels of open space on a development site, the total area of impervious surface is reduced and inifitration of precipitation is increased. This leads to decreases in total pollutant dischaEge and potential downstream erosion by reducing total and peak runoff flows. 25 ------- TABLE 5. EXISTING REGULATORY CONTROLS SUBDIVISION CONTROL Lawrence Methuen Newbul7port North Andover Scope of Regulations As required under MGL all lots being subdivided come under Subdivision Regulations. Lots on an accepted public way and having sufficient frontage are classified as “Approval Not Required” As required under MGL all lots being subdivided come under Subdivision Regulations. Lots on an accepted public way and having sufficient frontage are classified as “Approval Not Required” As required under MGL all lots being subdivided come under Subdivision Regulations. Lots on an accepted public way and having sufficient frontage are classified as “Approval Not Required” As required under MGL all lots being subdivided come under Subdivision Regulations. Lots on an accepted public way and having sufficient frontage are classified as “Approval Not Required” Runoff Quantity Control Open Space Post-Development Flow Control Runoff Recharge - Requires due regard for maintaining natural features and open space - None specified - None specified - Requires that efforts be made to maintain natural features and open space - Requires calculations showing no increase in peak flow during 100 year storm - None specified - Requires that efforts be made to maintain natural features and open space - None specified - None specified - Requires that efforts be made to maintain natural features and open space - Requires calculations showing pm and post- construction peak flows and total volumes for 2, 10, and 100 year storms - Requires that storm water shall be recharged rather than piped to surface waters to the maximum extent feasible Solids Control - None specified - Requires the development of a runoff control plan that minimizes erosion - None specified - Requires the development of an erosion control plan both during and after construction Other Pollution Control - None specified - None specified - None specified - None specified 26 ------- TABLE 5 (Continued). EXISTING REGULATORY CONTROLS SPECIAL PERMIT AND SITE PLAN REVIEW Lawrence Methuen Newburyport North Andover Scope of Coverage Site Plan Review Special Permit - Required for all new construction except 1 and 2 family residences - Required for all uses requiring a special permit - Requirements depend on district - Required for nonresidential buildings over 5,000 ft 2 and two buildings on sime lot - Required for all uses requiring a special permit - Required for specific listed uses - Required in specially designated waterfront zones - Required for residential use exceeding 9 units - Required for new industrial and commercial uses - Required for specific listed uses - Required for development or additions >2000 ft 2 except single family dwellings - Required for specific listed uses - Runoff Quantity Control Open Space Post-Development Flow Control Runoff Recharge - None specified - Requires drainage plan for 10 year storm - Requires on-site infiltration wherever practical - Review boards have the authority to impose special conditions for buffers and planting strips - None specified - None specified - Required boundary landscaping equivalent to 5 ft’/lOO ft 2 of parking - None specified - None specified - None specified - Requires plan showing drainage control structures to eliminate increases in peak and total flow from 2, 10, and 100 year storms - Detailed hydrology study including potential downstream impacts - None specified Solids Control - Requires the development of an erosion control plan & minimal grading - None specified - None specified - None specified Other Pollution Control - None specified - None specified - None specified - See special zoning controls- Watershed Protection District 27 ------- TABLE 5 (Continued). EXISTING REGULATORY CONTROLS LOCAL WETLANDS PROTECTION’ Lawrence Methuen Newburyport North Andover Scope of Regulations - No local ordinance; State standards (MGL Ch 131 Sec 40) apply - Local wetland protection bylaw; State standards (MGL Cl i 131 Sec 40) also apply 2 - No local ordinance; State standards (MGL Cl i 131 Sec 40) apply - Local wetland protection bylaw; State standards (MGL Ch 131 Sec 40) also apply 2 Runoff Quantity Control Open Space Post-Development Flow Control Runoff Recharge - Restrictions on amount of tree cutting allowed - Compensatory storage must be provided for all inland flood volume lost within same reach of water body - Must provide drainage calculations for the 10 and 100-year storms - None specified None in addition to state standards - None in addition to state standards - None in addition to state standards - Restrictions on amount of tree cutting allowed - Compensatory storage provided for all inland flood volume lost within same reach of water body - Must provide drainage calculations for the 10 and 100-year storms - None specified - Provides for 25 ft no disturb zone and 50 ft no build zone - Hydrologic analysis required for mean annual 10 and 100-year storms - No net increase in rate of aunoff allowed - Standards established for long-term design and operation of basins - Infiltration, leaching catch basins, and drainage dry wells recommended. 1 Specific performance standards are established in the state regulations for each type of coastal and inland resource area. Communities must refer to regulations (310 CMR 10) for guidance. The listed standards apply to all resource areas, as noted 2 These communities must also comply with the requirements of the Massachusetts Wetlands Protection Act. Requirements listed are contained in local regulations. See Lawrence and Newburyport for state standards applying to these communities. 28 ------- TABLE S (Continued). EXISTING REGULATORY CONTROLS LOCAL WETLANDS PROTECTION (Continued)’ Lawrence Methuen Newbwyport North Andover Scope of Regulations - No local ordinance; state standards (MGL Ch 131 Sec 40) apply - Local wetlands protection bylaw; state standards (MGL Ch 131 Sec 40) also apply 2 - No local ordinance; state standards (MGL Ch 131 Sec 40) apply - Local wetlands protection bylaw; state standards (MGL Ch 131 Sec 40) also apply 2 Solids Control - Agricultural maintenance and improvement activities must be in accordance with SCS guidelines - Utility lines permitted if erosion control plans are developed - None in addition to state standards . Agricultural maintenance and improvement activities must be in accordance with SCS guidelines - Utility lines permitted if erosion control plans are developed . Erosion control plan required including temporary and permanent ground cover and specific erosion control measures Other Pollution Control - Application of herbicides to public and utility structures must be in accordance with USDFA management plans - Must provide an estimate of pm. and post- development water quality conditions - None in addition to state standards - Application of herbicides to public and utility structures must be in accordance with USDFA management plans - Must provide an estimate of pre and post- development water quality conditions - Wetlands approved for fill must be replaced or restored in accordance with state and local standards Specific performance standards are established in the state regulations for each type of coastal and inland resource area. Communities must refer to regulations (310 CMR 10) for guidance. The listed standards apply to all resource areas, as noted 2 These communities must also comply with the requirements of the Massachusetts Wetlands Protection Act. Requirements listed are contained in local regulations. See Lawrence and Newbuiyport for state standards applying to these communities. 29 ------- TABLE S (Continued). EXISTING REGULATORY CONTROLS EARTH REMOVAL Lawrence Methuen Newburyport North Andover Type of Regulations - Zoning Bylaw & Earth Removal Bylaw - Soil Removal Ordinance - Building Regulations - Zoning Bylaw Exemptions - Construction of a building or road for which a permit has been issued - Approved subdivisions - Projects with approved building permits - Normal farm, garden, and orchard activities - Public use, cemeteries, roads, and utilities - Construction with an approved building permit and for which a plan has been filed with the Soil Removal Board - On-site road construction - Waiver process for sites < 1 acre or removal <500 cubic yards - Removal incidental to on- site development - Less than 50 cubic yards of soil to be removed . Runoff Quantity Control Open Space Post-Development Flow Control Runoff Recharge - None specified - None specified - None specified - Provide 100 foot natural buffer to a public way or wetland None specified - None specified - None specified - None specified - None specified - None specified - Hydrogeologic study required specifying downstream impacts of removal - None specified Solids Control - The impact of removal on runoff must be determined - Determine effect of removal on storm water runoff - Provide 100 foot natural buffer to a public way or wetland - Describe potential impacts to nearby surface waters - The plan must be approved by the Soil Conservation Service if> 1 acre in size - Siltation basins are required - No more than 5 acres of soil removal can take place at one time Other Pollution Control - None specified - None specified - None specified - None specified 30 ------- TABLE 5 (Continued). EXISTING REGULATORY CONTROLS SPECIAL ZONING CONTROLS Lawrence Methuen Ncwbui rport North Andover Runoff Quantity Control Open Space Post-Development Flow Control Runoff Recharge - None specified - None specified - None specified Planned Unit and Cluster Cluster Development - Minimum requirement of 30% open space - Hydrologic analysis is required before development Setback - Setback requirement for development near open streams and the Merrimack River Floodplain District - Development prohibited in floodway unless no increase in flooding can be proven - None specified Planned Residential and Development Districts Develonment - Minimum requirement of 30% open space Floodplain District - No increase in flood discharge in Zone A - None specified - Required minimum 30% open space for planned residential districts and 20% for planned development districts Special Protection District’ - Specifies protection zone between 100 and 325 feet of the high water mark Floodolain District - No development in floodway unless no increase in 100 yr flood - None specified Solids Control - None specified - None specified - None specified Special Protection District’ - Agricultural use allowed only with proper controls Other Pollution Control - None specified - None specified Performance Standards - Materials that could contaminate a ninning stream cannot be discharged Special Protection District’ - Nitrogen levels in groundwater are less than 10 mgll at property line - Determine phosphorus concentrations - Prohibits potential pollution causing activities LaKe LocnlcnewlcK watersuen 31 ------- Post-development Flow Control : Many development regulations require that peak runoff conditions from a site be calculated before and after construction. These requirements specify that the conditions after construction must reflect the conditions before construction. This is typically accomplished through the use of detention facilities, which can reduce peak runoff discharge rates, thereby decreasing downstream erosion problems. Through these regulations the desired outcome is specified but the approach for ensuring that outcome is determined by the developer. • Runoff Recharge Regulations may specify that storm water runoff be recharged on site. Such regulations can reduce the runoff leaving the site, thereby reducing development-induced hydrologic changes and pollutant transport. By directly promoting infiltration, peak and total runoff rates can be decreased and pollutant discharges and downstream erosion can be reduced. Solids Control Regulations addressing solids control may take the form of requirements for implementing erosion control practices during and after construction. Construction activities can greatly increase the level of suspended solids in storm water runoff by removing vegetation and exposing the topsoil to erosion during wet weather. Most communities, therefore, have requirements for implementing erosion control practices on construction sites. These requirements are generally overseen and enforced by the Conservation Commission when development occurs in or near wetland areas. Fewer communities have requirements for erosion control after construction is complete. Other Pollution Control Land development increases the concentrations of nutrients, pathogens, oxygen demanding substances, toxics, and salt in storm water runoff. Development regulations, therefore, could be used to address some of these specific pollutants. These regulations might take the form of special requirements for limiting nutrient export in special protection districts or setting performance standards for known problem pollutants. 32 ------- Strengths and Weaknesses of Existing Regulations The review indicates that none of the four communities surveyed in the study has a comprehensive program in place to address storm water and NPS pollution. Instead, each community addresses specific components of storm water management (i.e., soil erosion, flood control, or wetlands protection) to varying degrees. Below is a general discussion of the strengths and weaknesses of regulatory controls in the four communities. The controls investigated include: • Subdivision Control • Special Permit and Site Plan Review • Local Wetlands Protection • Earth Removal • Special Zoning Controls Subdivision Control. As previously noted, Massachusetts law requires that, with the exception of parcels having sufficient frontage on an accepted public way, all parcels being subdivided must undergo subdivision review. The four communities reviewed for this project require some level of storm water pollution control in the subdivision design and development process. However, the level of control required varies from community to community. In the area of runoff quantity control, all four communities have language encouraging the maintenance of open space and natural features. No specific requirements for open space, however, are given. For post-development flow control, Methuen and North Andover state specific design storms under which flow must be controlled. North Andover, however, is the only community that recognizes the importance of controlling smaller, more frequent storms rather than just the large storms that cause flooding. North Andover, is also the only community requiring the use of on-site runoff recharge to the “maximum extent feasible.” This requirement is not defined in terms of performance standards, however. Solids control is addressed by Methuen and North Andover. They require the development of a runoff control plan to minimize erosion during construction. North Andover also requires that the erosion control plan address the issue of post-construction runoff control. There are no additional provisions of the subdivision regulations in the 33 ------- communities designed to address additional pollutants, such as nutrients or toxics. Special Permit and Site Plan Review. All of the communities investigated for this review require special permits and a site plan review for certain specified developments. The developments not falling under these regulations are generally the single family and smaller nonresidential developments, including some types of agricultural activities. Within these permit and review processes, communities do not generally address storm water runoff control. Methuen and Newburyport require some landscaping on site; however, this is generally done for aesthetic reasons rather than to maintain open space. Some requirements are also in place to control post-development flow. The most comprehensive of these is in North Andover, where developers are required to control runoff from the 2, 10, and 100-year storms and determine the downstream impacts of development. Also, runoff recharge is required in Lawrence “wherever practical.” Once again, this requirement is not defined in terms of performance standards. Beyond these runoff quantity control measures, Lawrence requires the development of an erosion control plan. Other pollutants, such as nutrients and toxics, are not controlled in any of the communities by the special permit or site plan review processes. Wetlands Protection. The Massachusetts Wetlands Protection Act covers all wetlands in the state. However, communities have the option to implement wetlands protection bylaws that are more stringent than the statewide regulation. The state regulations control activities in each type of coastal and inland resource areas. The controls that apply across most or all of the different resources provide runoff quantity control and solids control through specifications for pre- and post-development flow control for the 10 and 100-year design storms and requirements for erosion control plans. They also specify that the use of herbicides and fertilizers be in accordance with state and federal laws. These statewide regulations provide a fairly complete -level of control on the effects of development. However, some communities, such as Methuen and North Andover, have instituted local wetlands protection bylaws to further protect wetland resources. The regulations in Methuen do not provide additional storm water runoff pollution controls. However, the regulations in North Andover address additional open space requirements, hydrologic analyses, and controls on runoff rate. In addition, the North Andover 34 ------- wetlands protection bylaw recommends the use of specific types of infiltration facilities. However, actual design standards or criteria are not specified. Earth Removal. The communities reviewed for this project all have earth removal regulations that specify requirements for approval of excavation activities. These regulations generally do not apply to removal of small amounts of soil or for removal under some other permitted conditions. The exemptions in Methuen are especially broad and include farm, garden, and orchard activities, as well as public uses and cemeteries. In areas where earth removal regulations do apply, there is typically little control of runoff quantity. There is a requirement in Methuen that a 100-foot buffer be maintained between earth removal activities and a wetland. Also, in North Andover, developers are required to determine the downstream impacts of the removal activities. However, the maximum level of impact allowed is not specified. Solids transport is the primary pollution problem associated with earth removal, and the communities generally address this issue. All of the communities require that developers determine earth removal activity impacts on downstream surface waters, although acceptable impacts are not defined This is further strengthened in Newburyport where activities involving more than one acre of soil removal must be approved by the Soil Conservation Service, and in North Andover where no more than five acres of removal can occur at once. Special Zoning Controls. In addition to the above regulations, communities can utilize special zoning tools to help in controlling storm water pollution problems. These include planned unit developments, cluster developments, special protection districts, floodplain districts, and performance standards. In all the communities investigated, except Lawrence, special development districts that require maintenance of 20 to 30 percent open space have been set up. Also, in Methuen, Newburyport, and North Andover restrictions have been set on developments in the floodway of the 100-year flood. Developments in these areas must show that there will be no increase in flood levels. Solids control is generally not specifically provided by these special zoning districts. The exception to this is the special protection district set up by North Andover in the Lake Cochichewick watershed that does not allow agricultural activities unless proper controls are in place. Some communities have also established tools to address other 35 ------- pollution problems, such as nitrogen and toxic control. Newburyport has developed a special performance standard in the waterfront district that prohibits the discharge of a material that could contaminate a running stream, although contamination is not defined in terms of specific criteria. Also, in the Lake Cochichewick watershed in North Andover, special requirements for the control of nitrogen and phosphorus are in place. These are the most comprehensive controls for these nutrients in the communities reviewed for this project. Source Controls In addition to the regulatory controls outlined above, a review of municipal control practices was èonducted in the four communities. These practices, which are shown in Table 6, can prevent storm water runoff from contacting pollutants and reduce the level of dry weather pollutant discharged to suthce waters. The purposes and relative effectiveness of each of these practices were outlined in the previous section. Strengths and Weaknesses of Existing Source Controls All four communities reviewed for this project have implemented source control practices that reduce the availability of pollutants, such as street sweeping, catch basin cleaning, and solid waste management. However, the greatest variation in the municipal programs exists in the area of roadway sanding and salting, which is reflected in the sand to salt ratio and the total annual tons per mile of salt used. Little consideration appears to have been given to the water quality effects of these practices. In addition, none of the communities has any program designed to locate and eliminate illicit cross connections. These can be a major source of dry weather pollution in highly developed urban areas or where combined sewer systems have been separated. 36 ------- TABLE 6. EXISTING SOURCE CONTROLS Lawrence Methuen Newburyport North Andover STREET SWEEPING Frequency Equipment (number) Once/2 days on 30 major streets and once/week on others Mechanical (3) Once/week in downtown and once/year in other areas Mech (1) Vacuum (3) Twice/year Mech (1) Once/year except Lake Cochichewick three/year and downtown twice/year Mech (2) CATCH BASIN CLEANING Frequency Equipment (number) Once/year Mechanical (I) Clamp Once/year Mech (1) Orange Peel Twice/year Once/year Mech (1) Orange Peel FERTILIZER AND PESTICIDE USAGE None used Fertilizer used on town ball fields None used Granular fertilizer used for sodding ANIM AL WASTE REMOVAL No Program No Program No Program No Program ILLICiT CONNECTION IDENTIFICATION AND REMOVAL No Program No Program No Program No Program SOLID WASTE MANAGEMENT Residential Commercial Recycling Program Once/week Twice/week Paper Fall Leaves Once/week Private collection Paper Once/week Twice/week None Once/week Once/week Paper Leaves/grass ROADWAY SANDING AND SALTING Sand-Salt Ratio Salt Used (Tons/Road Mile) Special Reduced Use Zones 4:3 11 None 1:1 12 None 4:1 3.5 None 7:1 6 None 37 ------- Structural Controls None of the communities investigated for this project require the use of specific structural controls on a widespread basis. Structural controls implemented in these communities are generally designed to meet some of the pre- and post-construction flow requirements of the subdivision and zoning regulations. While these regulations do not require specific types of controls, detention basins are typically used to ensure that post-construction flows equal pre- construction flows for the design storm or storms. The Town of North Andover, however, requires the use of structural practices in certain defined circumstances. As part of the wetlands protection bylaws, infiltration structures are recommended. The zoning bylaw requires the use of siltation basins if earth removal occurs. Also, there is a specific provision stating that proper controls must be used for agricultural practices in the Lake Cochichewick watershed. STRENGTHS AND WEAKNESSES OF IMPLEMENTATION Site visits were conducted at selected projects in Lawrence, Methuen, and North Andover to discuss storm water quality control issues with municipal officials. Regulatory and construction issues relating to storm water quality were reviewed and inspections were conducted at selected project sites. The evaluations considered compliance with regulatory requirements and recommended improvements. Specific information and typical evaluation criteria for each site are summarized in Table 7. The evaluations were conducted considering flood control, storm water quality, and general site development. 38 ------- TABLE 8. SITE EVALUATION SUMMARY Crescent Circle Worcester Street Griffin Brook Park Coventiy Estates New Castle Estates N. Andover Estates SITE FEATURES Location Development Type Topography Year Constrocted Lawrence Residential Hilly 1990 Methuen Residential Hilly 1989-1991 Methuen Industrial Flat 1980s N. Andover Residential Hilly 1980s N. Andover Residential Hilly 1991 N. Andover Residential Hilly Under Const DESIGN AND CONSTRUCTION FEATURES Flood Control Detention Used? Retention Used? Basin Operational? Evidence of Overflow/Erosion? Velocity Control? Water Qua1ity Freatment Grassed SwalesiFilter Strips? Filter Berm/Extended Detention? General Site Development/Erosion Control Slopes Stabilized? No No N/A N/A Yes No No Yes Yes No Yes No Yes No No Yes Not Evident No N/A N/A Yes Yes No Yes Yes No Yes No Yes No No Yes Yes No Yes No Yes No No Yes Yes No Under Const Under Coast Yes Yes Yes Under Coast N/A = Not Applicable 39 ------- Flood Control Developers typically comply with storm water flood control requirements by utilizing detention or retention basins. These basins contain the runoff for a particular storm event and either release the water at a slow rate or allow the water to infiltrate into the groundwater. Representatives of the communities acknowledged that flooding is a concern with existing and new projects. Crescent Circle and Griffin Brook Industrial Park were the only projects which did not include detention basins. No projects utilized retention basins for infiltration or runoff. All the basins evaluated appeared to be operational with little evidence of overflow from the containment berms. The Worcester Street project had excessive buildup of sediment and debris in the bottom. Runoff velocity controls prevent erosion and scouring and protect against downstream sediment contamination. All the projects reviewed included controls to prevent erosion near drainage outfalls. These controls vary from the use of a rip rap slope up gradient of the detention basin for the Worcester Street project to the development of a rip rap velocity reduction basin for the Crescent Circle project. Storm Water Quality Storm water quality protection has historically not been addressed by municipalities. North Andover is the only community which has undertaken a concerted effort to improve the quality of storm water discharge from new developments. Only Griffin Brook Industrial Park and the North Andover Estates project included the use of grassed swales and filter strips in the drainage design. The use of these controls in Griffin Brook Industrial Park was likely a result of the need to address other environmental issues such as flood plain management or erosion prevention. These controls also provide filtering of sediments. The North Andover Estates project included these controls to allow for the filtering of sediment and associated contaminants out of the runoff. 40 ------- The development of “extended detention” basins allows for the settlement of sediment and other pollutants. This process involves restricting outflow from the basins for smaller storms such as the one year event. EPA studies have shown that high levels (i.e., 90 percent) of the pollutants in storm water runoff are captured by controlling smaller storm events. North Andover Estates’ detention basin includes a baffle to extend the detention time for the runoff in the basin, but does not include detaining the one-year storm event. None of the other basins were designed to detain such smaller storms. Many of the basins had evidence of sediment buildup in the streams or wetlands down-gradient of the outlet. This buildup indicates that the debris is not settled out in the basin but is passed through the outlet. General Site Development Projects have typically included some means to control runoff and sediment during construction. These measures were probably included to conform to the requirements of the Wetlands Protection Act; local officials; or for safety or aesthetic reasons. All the projects have stabilized slopes and some still have erosion controls in place. While the use of the erosion controls and slope stabilization techniques has not been driven primarily by water quality issues, they do generally offer protection from sediment contamination. RECOMMENDED IMPROVEMENTS Based on the review of regulatory and source control practices implemented in four communities in the Merrimack River basin, some general conclusions can be reached about storm water and NPS pollution control practices. None of the communities investigated has systematically used its existing regulations to prevent storm water and NPS control problems, although North Andover has made the best attempt. The communities all have regulations that, jf strengthened, could provide improved pollution control. However, these regulations have been developed over a number of years and have had purposes largely unrelated to runoff pollution control. Therefore, they need to be reexamined in light of their ability to control storm water runoff and NPS pollution. Community source control practices appear generally adequate, except for 41 ------- exercising caution by limiting use of salt for deicing, and developing a program to remove cross- connections and illegal discharges. Below are some of the more important recommendations for strengthening the regulatory and source controls investigated for this project. Regulatory Controls The following measures that would result in more effective control of storm water and NPS pollution of surface waters: Site plan, special permit, and subdivision criteria should be more specific with regard to proper storm water runoff control in the areas of open space, post-development flow control, and solids control. The criteria could be presented in the form of a checklist that the special permit granting authority or planning board could use to insure that each new development or redevelopment is meeting appropriate standards. Among the criteria that could be included are: Open Space • Requirement of a minimum 100-foot vegetated buffer to any surface water body or wetlands area (Pitt, 1991 - Quoted from Birmingham Proposed Watershed Protection Ordinance). Size of the buffer can be related to the size of the development. A 100-foot buffer may not be appropriate for a small parcel. • Requirement for designs including “disconnected impervious areas” such as the following: - roof drains discharge to pervious areas - driveways slope to pervious areas - elimination of curbs where they are not needed to allow runoff to flow overland to pervious areas Post-Development Flow Control • Requirement for control of runoff from the 2 and 10 year storm events, such that post-development peak and total flows are no greater than pre-development peak and total flows (Pitt, 1991 - Quoted from State of Maryland Model Stormwater 42 ------- Management Ordinance). A smaller storm, such as a 1-inch depth rainfall event, should also be included. Runoff Recharge • Requirement for onsite recharge on sites with groundwater more than four feet below the bottom of the recharge structure and soils with infiltration rates greater than or equal to 0.27 in/hr (Washington State Department of Ecology, 1991). On-site recharge can be defined as a percentage of runoff volume from a design event (i.e., recharge 90% of the runoff from a two-year storm). Solids Controls • Requirement for preparation of an erosion control plan that addresses control of both temporary construction and long-term runoff. Based on requirements in other communities, the plan should include the following: - location of areas to be stripped of vegetation and other exposed or unprotected areas - a schedule of operations to include starting and completion dates for major development phases, such as-land clearing and grading, street, sidewalk, and utility installation, and sediment control measures - specifications for diverting water from upsiope areas so it does not flow over disturbed land - seeding, sodding, or revegetation plans and specifications for all unprotected or unvegetated areas - location and design of structural sediment control measures, such as diversions, grade stabilization structures, debris basins, etc. - information relating to the implementation and maintenance of the sediment control measures Other Pollution Control • Specific standards should be developed where particular pollutants are known to cause pollution problems. This is a community-specific issue that is a function of the particular water resources being protected. 2. Consistent standards should be applied across regulations, where possible. For example, baseline design storm requirements should be the same for required calculations in subdivision, special permit, earth removal, and wetlands protection regulations. In Table 5, good criteria used in one regulation were often not applied as part of other regulations, 43 ------- although they were applicable. 3. Specific requirements should be set for periodic post-construction inspection of a site. Inspections should be conducted after at least one major storm event per year (Maryland DNR, 1985). The post construction inspections should be done by staff of the town or by the agent of the planning board or special permit granting authority at the expense of the developer. The fees for these inspections should be added to the fees normally assessed to the developer during the review and construction phases of the project. Post construction inspections and resulting maintenance are critical to the performance of storm water facilities’ ability to remove pollutants. 4. For those communities that have nonresidential development situated adjacent to critical water bodies, overlay districts should be implemented for the protection of water quality. Any new or substantial rehabilitation of nonresidential activities should be required to obtain a special permit. The requirements of the special permit must be designed to protect the type of water body in each of the overlay districts, and thus there might be slightly different discharge limitations depending on whether the water body is a wetland, a low- flow stream, a fast- flowing river, or a recreational lake. Development of new residential or nonresidential activities should be curtailed in areas adjacent to drinking water bodies. 5. The types of exemptions for special permit, site plan review, or earth removal should be narrowed. For example, in many communities agricultural activities are exempt from review. However, all commercial agricultural activity, any residential agricultural activity greater than 5000 square feet of a surface water body should be subjected to special review and standards. for limiting the amount of nutrients added to soil (Pitt, 1991 - Quoted from State of Maryland statewide storm water control regulations). Any earth removal activity of over 2000 sf or greater than 400 cy should undergo special permit review (Pitt, 1991 - quoted from Proposed Birmingham Watershed Protection Ordinance). For those activities that would remain exempt, a set of standard storm water 44 ------- control practices should be added to that part of the zoning bylaw authorizing such activity. These standards should include requirements for maximum slope, revegetation, and prohibitions on any direct discharge to any surface water body or to adjacent properties. Water quality impacts could be caused by the cumulative effects of small development that is currently exempt from most of the existing controls. 6. The standard storm water control provisions noted above in Item 3 should also be made applicable to those projects filing for “Approval Not Required” under the Subdivision Control Law. The developer would not be required to submit a preliminary or definitive plan as required for those projects requiring subdivision approval, however, the developer would be required to comply with standard erosion and runoff control measures. 7. A requirement for preparation of an Environmental and Community Impact Analysis should be incorporated into subdivision control regulations. Based on requirements in other communities, any submission of a residential subdivision creating over 15 lots, and all non-residential subdivisions, should be accompanied by such an Impact Analysis. The Planning Board may require that the analysis be conducted for smaller residential subdivisions, if the proximity to sensitive resources warrants it. Among the issues addressed in the Impact Analysis should be Water Quality. The impact of storm water run-off on adjacent and downstream surface water bodies and sub-surface ground water should be evaluated. The evaluation should address the dangers of flooding as a result of increased downstream runoff, especially peak runoff; the potential for downstream water quality degradation; and the potential for short-and long-term erosion. The impact analysis must address the direct and indirect water quality impacts, and must identify measures to be used to minimize any adverse water quality impacts. The state water quality standards can serve as performance standards for assessing water resource impacts. 45 ------- SUM1 1ARY OF ASSESSMENT PROCEDURE Land development in communities is one of the primary causes of storm water and NPS pollution problems. These problems can, however, be difficult to address once water resources have been affected. Therefore, it is more appropriate and effective for communities to prevent these pollution problems through efforts to control and guide land development. Since municipalities generally develop regulations and undertake source control practices for reasons other than runoff pollution control, improvements may be made by assessing current regulations and source control practices for their ability to address these runoff pollution problems. This section outlines the steps that can be used to assess and strengthen runoff pollution controls. This assessment emphasizes implementing regulatory and source control practices as a first step in addressing storm water runoff and NPS pollution problems. In order to implement a more complete program involving retrofitting specific structural control practices in existing developments, a more complex and time-consuming process must be undertaken. The steps in this regulatory and source control review process include: • Investigate Existing Regulatory and Source Control Measures • Investigate Recent Land Development Projects • Determine Water Resources • Strengthen Controls Investigate Existing Regulatory and Source Control Measures Few communities have implemented comprehensive storm water pollution control ordinances because of the lack of recognition that storm water can be a pollution problem, the difficulties inherent in developing such regulations, and potential duplication of effort with other existing regulations. In order to strengthen existing regulations and practices, it is necessary to first summarize the aspects of existing regulations and source controls that address storm water runoff pollution. Existing regulations should be summarized in a matrix similar to Table 5 in this report. The regulations that should be investigated include: 46 ------- • Subdivision Regulations • Special Permit and Site Plan Review Procedures • Wetlands Protection • Earth Removal • Other Special Protection Regulations - Special Protection Districts - Planned Residential and Development Districts - Cluster Developments - Floodplain Districts - Performance Standards These regulations can be used to reduce storm water runoff pollution through the maintenance of open space, control of post-development flow, recharge of runoff, control of solids discharges, and control of other pollutants. For other Merrimack River basin and Massachusetts communities, a comparison can be made with the four communities summarized in this report. Developing a matrix with this information can allow a community to identify the areas of control that may be weak. For example, the communities investigated for this project generally have regulations that control peak runoff rates from large storms. However, since runoff pollution is primarily the result of smaller storms, little quality control is provided. Also, few of the regulations existing in these communities provide specifications and criteria for the construction and maintenance of structural control practices. A similar matrix can be developed for outlining existing source control practices (see Table 6). The practices that should be included in this review include: • Street Sweeping • Catch Basin Cleaning • Fertilizer and Pesticide Usage • Animal Waste Removal • illicit Connection Identification and Removal • Solid Waste Management • Roadway Sanding and Salting • Important considerations include the frequency of actions and the conditions under which the actions are taken. Most communities conduct these activities to maintain the aesthetic qualities 47 ------- of an area, with runoff pollution control being a secondary consideration. In the areas of street sweeping, catch basin cleaning, and solid waste management, frequencies that maintain the aesthetic qualities of an area are typically sufficient to address some of the runoff pollution control considerations. However, reduced roadway sanding and salting and illicit connection identification and removal may be controls that a community does not currently undertake that could be valuable in reducing storm water runoff pollution. The development of a matrix outlining this information can help the community more fully identify the areas of potential improvement. Investigate Recent Land Development Projects Investigating existing development regulations can indicate the areas where storm water runoff pollution control is weak. However, in order to fully assess existing regulatory controls, the implementation of these controls at recent developments can be investigated. Communities should investigate developments that have gone through the existing regulatory reviews in the past few years. Conducting site visits can indicate how well the existing regulations are being implemented. This is the true test of the effectiveness of regulations and the review process. Site investigations should be conducted with the existing regulations serving as a guide. Factors, such as on-site structural controls, percent open space, erosion controls, and landscaping features, as ouffined in Table 7, should be considered. Other than the existence of structural controls, the site should be evaluated to determine whether maintenance is being performed. Structural controls designed to reduce pollutant discharges become less effective as sediment accumulation, vegetative growth, and outlet clogging occur. Regular maintenance of the controls is necessary to ensure that they continue functioning as designed. A site evaluation matrix, similar to that shown in Table 7, can be utilized in the review of recent developments. Areas of discrepancy between regulatory requirements and actual implementation can indicate a failure to properly enforce existing controls. These can be addressed through improved education of review board members or increased requirements for plan submission. However, if a site has problems beyond those typically controlled by regulations, the community 48 ------- may be required to strengthen existing controls. In either case, a number of sites should be investigated on a regular basis to ensure that regulations are providing a sufficient level of runoff pollution control. Assess Water Resources The level of storm water and NPS pollution control required in a community is influenced by the existing water resources. For example, protection of a surf ce water drinking supply is more critical than protection of a small urban creek. Therefore, in this step, communities should make a determination of existing water resources and their value. Information should be gathered on the existing conditions throughout the watershed and in the water body. Watershed information includes land use, topography, soil type, and other physical features. In addition, water quality and sediment quality data should be compared to classification standards and criteria to give an indication of the quality of the resource. The information required for a watershed and receiving water review are: • Watershed Data Description - Environmental Data - Infrastructure Data - Municipal Data - Potential Sources/Existing Pollution Control Data - Miscellaneous Data • Receiving Water Data Description - Physical/Hydrologic Data - Chemical Data - Biological Data - Water Quality Standards and Criteria - Miscellaneous Data • Summary of Data Gaps and Needs These data can impact the level of benefit expected from implementing controls, and are necessary for a community to be able to make specific changes to regulatory and source control practices. 49 ------- Strengthen Controls Once existing regulatory and source control practices have been reviewed, implementation of those regulatory control practices has been investigated, and the water resources in the community have been assessed, the regulatory and source control practices can be strengthened. In this step, recommendations, similar to those outlined in the previous section, can be implemented. This involves analyzing each regulatory control practice to determine the potential level of control it can provide. Consideration must be given to the scope of the regulations. In some cases, existing regulatory control is not provided and new regulations, such as overlay zones, performance standards, or special protection districts, will have to be developed. However, in other cases, existing subdivision, zoning, or earth removal regulations will only have to be strengthened to address an identified problem. In addition, the water resources existing in a community will impact the level of control desired. More comprehensive controls will be required in a surface water supply watershed than in an urban stream watershed. Issues that must be considered in this step include the authority and the ability of local review boards to implement some regulations, input from the regulated public (including support and opposition), and budget restriction. However, the assessment process, which reveals existing weaknesses and identifies key resources for protection, will allow communities to establish priorities for implementing necessary storm water control measures. 50 ------- REFERENCES Florida Department of Environmental Regulation, 1992. “The Florida Development Manual: A Guide to Sound Land and Water Management.” Maryland Department of Natural Resource, Water Resources Administration, Sediment and Stormwater Division, 1985. “Inspector’s Guide Manual for Stormwater Management Inifitration Practices.” Morehouse, Robert, 1988. “Ready Reference Guide to Non Point Source Pollution; Sources, Pollutants, Impairments; Best Management Practices for the New England States,” detailed from U.S.D.A. Soil Conservation Service to U.S. EPA, Region I. Merrimack Valley Planning Commission, 1991. “A Survey of Urban Runoff Programs in Selected Communities in the Merrimack Valley Region.” Minnesota Pollution Control Agency, 1989. “Protecting Water Quality in Urban Areas.” Pitt, R., 1991. “Source Loading and Management Model: An Urban Nonpoint Source Water Quality Model. Volume I: Model Development and Summary.” Pitt, R., M. Lalor, M. Miller, G. Driscoll, 1990. “Assessment of Non-Stormwater Discharges into Separate Storm Drainage Systems. Draft.” Storm and Combined Sewer Control Program, US EPA. Schueler, T.R, 1987. “Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMPs.” Metropolitan Washington Council of Governments Publication 87703. Urban Land Institute. 1981. “Water Resource Protection Technology: A Handbook of Measures to Protect Water Resources in Land Development.” US EPA. 1974. “Urban Storm Water Management and Technology: An Assessment.” 51 ------- REFERENCES (Continued) United States Environmental Protection Agency, 1987. “Guide to Nonpoint Source Control.” United States Environmental Protection Agency, 1992. “Coastal Nonpoint Source Control Program: Management Measures Guidance - Draft.” United States Environmental Protection Agency, Center for Environmental Research Information, 1992. “Planning Process for Storm Water and Nonpoint Source Control - Draft.” Washington State Department of Ecology, 1991. “Storm Water Management Manual for the Puget Sound Basin.” 52 ------- APPENDIX A ------- G.n.ral Effectiven... of Various Nonstructural Control Practices S ZU £ 5 £ • C — s-. 5 •U WZa ! — U C S E • I • Eu •O S 1; E c O U • c 5 ! •u SO 0 • u C . C • C’ • 1 • a . 1 E • Eu Ou 04 . . ‘h V EOe u •C .,wE • .1 • O• uo • .; 2 •u •OO U..aO I • SE e . E a .! •! 05 •a : . — . & DENSITY ZONES 11.1. 0 0 0 0 0 0 0 ® 0 0 0 0 0 0 R stZ.a.s 0 0 0 0 0 0 0 ® 0 0 0 0 0 0 ProtsotIseZon.s 0 0 0 0 0 ._ 0 0 0 0 0 Ov.rSey Z.ø.. 0 0 0 0 0 . _ ® 0 0 0 0 0 0 P.,(o,m.n..Z.nlng 0 0 0 0 0 • 0 ® 0 0 0 0 0 0 EIERVIS SF•SUSUISIU 0 W.tIwidBufI.rs 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O_ — — — 0 Cs.ut.IUufI.ru Q .4. 0 0 0 • 0 0 0 0 . . Espsnd.dIuIIis 0 •_O_0 0 0 0 0 0 O _O 0 0 0 FI..d$.mLke t. 0 0 0 0 0 0 • 0 0 •_ 0 • 0 0 0 St..p$.N.Lk, t. 0 0 0 0 0 Q_ 0 0 0 0 0 S t$.ibit. 0 0 0 0 ® 0 0 0 0 0 0 0 0 W.*I.nd Prst..tI.n 0000 Hsbltst Pr.t..%I .ø 0,.., $ps.• Pv.t.stI., , () 00 00 0 000 0• 00 0 . 0 0 0 0 0 0 0 . 0 0 0 0 0 0 00 0 0 0 0 0 0 0 I 3 t 3! 1 o !! :t ! ; s_s I S... :izi • £ 1 !ft • i1 •ooe .oos 0 0 . 0 C D S . Ii II i fl a s !I flI! ! i! fl )!! s ! !t IIH : !ft; iI f !I! I iIi III i i i! 8 ; ! II • ! ! ;i ! liii .oo •oo. •oo. •ooe •oo •oo. •oo •ooe •ooe •oo. •oo® •oo •ooe soos Source: Metropolitan Washington Council of Governments, 1991 (Draft) ------- (continued) III. SITE PLANNING CIu.I.r Q • Q .e a 0 0 P.,Iorm.nc•CrIt.rI. • • • • • • 0 0 0 0 0 Q_ 0 0 0 0 I .thnIz. lmp.rvlousn.ss J D c D c D • : . IRO$ION A SEDIMENT CONTROL . TI,n./A,..DI.turb.na. 0 0 S 0 ® 0 5 5 5 • 0 5 0 5 0 • V. POST DEVELOPMENT . UrbsnHou..k..pIn 0 0 0 0 0 5 0 0 0 0 p p F.rtIIIi.r Control 0 0 ® ® ® 0 0 0 0 0 0 0 0 0 S.ptIoMsInI.nsno. 0 • 0 ® ® ® S 0 0 0 0 0 0 0 0 w..t. 0 ® 0 ® Q cJ 0 0 0 0 0 0 0 Ii i 0:0 :. ! P1 loll gEg’ •ooe !J fin .ooe a L 11i iJI .ooe j r 0 11 .. SI •ooe ‘J ii Ini .ooe !I fi!l •ooe I 11 I till e00e ‘ I I1 121 •ooe I. i l1 m •oo• Phi .oo. S 1 ;- .1! : : Hf: .oo. lu •ooe !i1i •ooe J !Ili •oo. 1111 .oo. : . I 1 I £.t H IlI •ooi — 11 £ C 2 J :J C 2 — U f S • ii S cS • — 1! U C .• H J —c S Eu ou U . . C co1 U ft SCE w_ • — O •0 OS u • — C S E 0 C :; • P 000 e10 C 2 — S _ 5E 2 — j .E 3 . 5 • 3 C • Sourc•: Metropolitan Washington Council of Gov•rnments, 1991 (Draft) ------- Comparative Pollutant Removal Of Urban BMP Designs FILTER STRIP GRASSED SWALE DESIGN 10 DESIGN II DESIGN 12 DESIGN 13 DESIGN 14 oooo ® 00000® oc o MODERATE MODERATE lION MODERATE MODERATE NIGH MODERATE HIGH NIGH LOW LOW MODERATE LOW LOW 1 1EV; o (3 20T040%REMOVAL J 4OT000SREMOvAL •OTOIO%REMOVAL • ( INSUFFICIENT KNOWLEDGE Design 1: First-flush runoff volume detained for 6-12 hours. Design 2: Runoff volume produced by 1.0 inch, detained 26 hours. Design 3: As in Design 2, but with shallow marsh in bottom stage. Design 4: Permanent pool equal to 0.5 inch storage per impervious acre. Design 5: Permanent pool equal to 2.5 (Vr); where Vrmean storm runoff. 1i sign 6: Permanent pool equal to 6 0 (Vr); approx. 2 weeks retention. Design 7 Facility exfiltrates first-flush; 0.5 inch runoff/;mper. acre. Design 8: Facility exfiltrates one inch runoff volume per l eper. acre. Design 9: Facility exfiltrates all runoff, up to the 2 year design Storm. Design 10: 600 cubic feet wet storage per impervious acre. Design 11: 20 foot wide turf strip Design 12: 100 foot wide forested strip, with level spreader. Design 13: High slope swales, with no check dams. Design 14: Low gradient swales with check dams. Source: Shueler, 1987 BMP/design EXTENDED DETENTiON POND DESIGN I DESIGN Z DESIGN 3 WET POND • ( 3) ® • •c DESIGN 4 DESIGN 5 DESIGN a INFILTRATION TRENCH DESIGN 7 DESIGN S DESIGN S INFILTRATION DASIN •)) • DESIGN 7 DESIGN S DESIGN S POROUS PAVEMENT • ••• MODERATI HIGH NIGH DESIGN 7 DESIGN S DESIGNS WATER OUALITY INLET • . •• MODERATE HIGH HIGH O®®®®® ------- |