The sediment TMDLs in this TMDL document have been superseded by the Kiskiminetas-Conemaugh River TMDL completed by EPA on January 29, 2010.

Transcription

1 The sediment TMDLs in this TMDL document have been superseded by the Kiskiminetas-Conemaugh River TMDL completed by EPA on January 29, The TMDL can be viewed by following the link The nutrient TMDLs in this document are still applicable.

2 Nutrient and Sediment Total Maximum Daily Loads For Unnamed Tributary to Conemaugh River Stream Code Indiana County, PA (18-D) Prepared by Southwestern Regional Office Pennsylvania Department of Environmental Protection August 2004 i

3 TABLE OF CONTENTS I. TMDL OVERVIEW...1 II. EXECUTIVE SUMMARY...2 III. INTRODUCTION...3 A. Watershed Description Location and General Description Topography and Geology Land-use...5 B. Nature of Impairment and Water Quality Standards...8 C. Pollutant Backgrounds, Linkage Analysis, and Endpoints Nutrients Sediment...14 IV. TMDL DEVELOPMENT METHODS...15 A. Reference Watershed Approach: Setting the Standard...15 B. Watershed Assessment Approach and Modeling Reference Watershed Loading Rate Total Maximum Daily Load Margin of Safety and Load Allocation Adjusted Load Allocation and Loads Not Reduced Load Allocation Distribution and Required Reductions...16 C. Quality Assurance Consideration of Critical Conditions Consideration of Seasonal Variation...17 V. TMDL RESULTS...18 A. Reference Watershed Selection...18 B. Pollutant Loads and Reference Watershed Loading Rates Pollutant Loads Reference Watershed Loading Rates...21 C. Total Maximum Daily Loads...22 D. Margins of Safety...22 E. Load Allocations...22 F. Adjusted Load Allocations and Loads Not Reduced...23 G. Load Allocation Distribution and Required Reductions...24 ii

4 VI. REASONABLE ASSURANCE...25 VII. PUBLIC PARTICIPATION...26 VIII. REFERENCES...21 IX. APPENDICIES...27 Appendix A. AVGWLF Model Overview & GIS-Based Derivation of Input Data...27 Appendix B. Equal Marginal Percent Reduction Method...30 Appendix C. GWLF Output for Unnamed Tributary Appendix D. GWLF Output for Unnamed Tributary Appendix E. Equal Marginal Percent Reduction Calculations for Unnamed Tributary (SEDIMENT)...33 Appendix F. Equal Marginal Percent Reduction Calculations for Unnamed Tributary (PHOSPHORUS)...34 Appendix G. TMDL Information Sheet For Unnamed Tributary Appendix H. Best Management Practices (BMPs) Information Sheets Runoff Management System Streambank and Shoreline Protection Grassed Waterway Nutrient Management...49 iii

5 I. TMDL Overview The TMDL development process is a nationwide effort to inventory and improve the health of our waters. Each water body in Pennsylvania has water quality standards that define the amount of substances with pollution-potential that can exist therein. The attainment of these standards is essential to ensure that the quality of each water body can support its protected use. Water quality may be protected to support coldwater fishes, recreational activities, potable water, or many other protected uses. When the water quality standards of a water body are not met, the water is classified as being impaired. Section 303(d) of the Clean Water Act requires all impaired waters to be identified and documented. Consequently, the Pennsylvania Department of Environmental Protection is assessing all of its water bodies, and listing those that are impaired on its own 303(d) list. Furthermore, regulations require that a TMDL study must be completed for each impaired water body on this list. The goal of such a study is to determine how to restore impaired water bodies. Identifying and eliminating all sources of the pollutant would of course be the optimal method of restoration; however, this is rarely feasible or possible. Instead, a TMDL study is directed at determining the total maximum daily load of a pollutant that a water body can assimilate (uptake) and still maintain its water quality standards. Once a TMDL is determined in terms of a pollutant load (e.g., lbs nitrogen/yr), this value is compared to the existing load. In general, the difference between the TMDL and the existing load constitutes the targeted load reduction. To reach this targeted load, reductions from the loads of both point (e.g., sewage treatment facility discharge) and non-point (e.g., farmland runoff) sources are considered. Pollutant contributions from non-point sources often comprise the majority of the total load. To reduce these loads, Best Management Practices (BMPs) are reviewed and recommended to land owners. Stream-bank stabilization and vegetated buffers are examples of BMPs. Proper implementation of these land management strategies can cause substantial reductions of pollutants, and consequently can have a meaningful and positive effect on the health of our waters. Figures 1 and 2 (left to right). Photographs of areas where BMPs have been implemented to reduce nutrient leaching. Fig. 1 Riparian buffer strip, and Fig 2. Contour buffer strip. 1

6 II. Executive Summary This TMDL was developed for unnamed tributary to the Conemaugh River, Indiana County (18-D). It is listed as being impaired by agriculture in Pennsylvania s d list, whereby nutrients and sedimentation were stated to be the causes of impairment. However, a reassessment revealed that the current cause of sediment and nutrient pollution is runoff from development and transitional land, i.e., land that is currently being developed. Using AVGWLF, a watershed that currently attains its water quality standards, and has several relevant similarities with the impaired watershed was found: tributary to Blacklick Creek. This watershed is adjacent to the impaired watershed, and is similar except that it has vast areas of trees and grasses that buffer the flow of runoff from development and transitional land. Using the GWLF model, the existing loads of sediment and phosphorus from non-point sources were determined for both the impaired and reference watersheds; no point sources exist within either watershed. Based upon this data, the loading rate of the reference watershed was used to determine an acceptable load for the impaired watershed, and this acceptable load was then allocated among the various non-point pollution sources. The required pollutant reductions were then determined (Table i). Reductions could be attained by implementing Best Land Management Practices (BMP). Proper implementation of BMPs can cause substantial reductions of pollutants. Based on the causes of impairment of this watershed, the following BMPs were recommended: 1) Runoff Management System, 2) Streambank and Shoreline Protection, 3) Grassed Waterway, and 4) Nutrient Management. Information sheets about each of these BMPs are included in the appendices of this report. Table i. Parameters of the TMDL development and required load reductions of unnamed tributary determined using existing land-use conditions. Parameter Sediment (tons/acre) Phosphorus (lbs/acre) Reference Loading Rate Total Daily Maximum Load Margin of Safety (10%) Load Allocation Loads Not Reduced Adjusted Load Allocation Required Reduction (%) Low Intensity Development 29 - High Intensity Development 25 - Transitional Land Golf Course Streambank 27 - Groundwater - 21 Hay/Pasture

7 III. Introduction A. Watershed Description 1. Location and General Description The watershed of tributary to the Conemaugh River is located in Blairsville, PA (Indiana County). It lies on the south-central border of Indiana County, within Burrell Township (USGS quadrangle Bolivar) (Figure 1). From the origin of its main branch, it flows northwesterly and then southwesterly through sub-basin 18D for about 0.7 miles before joining with the Conemaugh River. Tributary receives water from two tributaries, and all together its 0.64 mi 2 -watershed encompasses a total of 1.5 miles of stream. Figure 1. Illustration of the watershed of tributary (Indiana County, PA). 3

8 2. Topography and Geology The watershed of unnamed tributary lies within the Pittsburgh Low Plateau Section of the Appalachian Plateau Province. This section consists of a smooth undulating upland surface cut by numerous narrow and relatively shallow valleys. Elevation within the watershed ranges from 305 to 361 m above sea level. Rocks within the watershed are entirely interbedded sedimentary, and the sole underlying bedrock group is the Casselman Formation. The strata of this group vary by area, but typically consist of coal, claystone, limestone, shale, and sandstone. Soil associations within the watershed include Hazelton-Dekalb-Buchanan (93%), Monongahela-Philo- Atkins (6%), and Gilpin-Wharton-Ernest (1%). The following soil association descriptions were taken from and were authored by Dr. Beverly A. Chiarulli of Indiana University of Pennsylvania. Hazleton soils are found on ridges, hilltops, and upper sideslopes. The soils developed in material weathered from acid gray, brown, or red sandstone. Most Hazleton soils are in woodland of mixed oaks, maple, cherry and occasional conifers. Some areas have been cleared for pasture and cropland. Dekalb soils are on nearly level to very steep, uplands and ridges. Slopes are usually convex positions. The regolith weathered from gray and brown acid sandstone in places interbedded with shale and graywacke. Most Dekalb soils are in forests of mixed oaks, maple, and some white pine and hemlock. Smaller areas have been cleared for cultivation and pasture. Buchanan soils are on nearly level to very steep terraces and concave portions of mountain foot-slopes often extending well into the valleys along drainage ways. The Buchanan soils formed in colluvium from acid sandstone, quartzite, metarhyolite, siltstone and shale. Woodland is the major use. Some areas are cleared and used for pasture, small grain, and row crops. Wooded areas are mixed hardwoods of oak, maple and ash. Monongahela-Philo-Atkins are deep, moderately well-drained soils on terraces and floodplains. This association occurs along the larger streams of the area; about 45% of it contains Philo soils. These soils are frequently flooded. About 30% of the association consists of deep, moderately well-drained Monongahela soils. These soils are level to sloping. They have fragipan. About 20% of the association consists of deep, poorly drained Atkins soils that are frequently flooded. The remaining 5% consists of small areas of Tygart and Purdy soils, approximately two thirds of the association is woodland. Gilpin-Wharton-Ernest soils are moderately deep and deep, gently sloping to moderately steep, welldrained and moderately well-drained soils that formed in the uplands in residual and colluvial material. This association consists of areas of soils on moderately broad to narrow ridges on hills that are dissected by drainage ways. The Gilpin soils formed in residuum from acid shale and sandstone. The Ernest soils have a slowly permeable layer at a depth of 20 to 30 inches. They formed in colluvium from acid shale, siltstone, and sandstone. Ernest soils are on foot slopes of hills and ridges as well as in concave areas on ridge tops. Wharton soils are deep and well drained. They formed in residuum from acid clay, shale and siltstone. Most areas of this association are in cropland and woodland habitats. 4

9 3. Land Use According to the initial projections of the AVGWLF model (Appendix A), the majority of the landuse within the watershed was cropland and hay/pasture. However, a recent survey (March 2004) revealed that very little of either of these land-uses exists within the watershed. Instead, much of this land has been converted into low- or high-intensity development, and furthermore a large golf course has been built that covers a uniform 40% of the entire watershed (appropriate adjustments were made to the model). Figure 2 illustrates the watershed as it is currently. Land-use distribution for dominant categories is as follows: Low intensity development 42%, Golf course 40%, Hay/Pasture 7.5%, Forest 5.3%, Transitional - 3%, High Intensity Development 2.7%. Transitional Figure 2. Initial and current land-uses within the watershed of tributary 44769, Indiana County. Star indicates where a storm sewer discharge enters tributary Transitional refers to land that is currently being developed. 5

10 The main branch of tributary originates within the Chestnut Ridge Golf Course (Figure 3), where it is fed by a large pond that drains the eastern region of the golf course. From its origin, its travels northwesterly and is joined by two tributaries (tributaries and 44771) (Figure 4) and a storm sewer discharge (indicated by star on Figure 2) before crossing Strangford Road. Tributary originates just south of State Route 2002 (Figure 5), where it receives runoff from parts of a new shopping plaza that is being developed on the north side of Route It travels southwesterly crossing Strangford Road, and receives scattered runoff from low-intensity development before joining with tributary Tributary originates near the intersection of State Route 2002 (Figure 6) and the main entrance to the golf course. It also receives runoff from newly developed areas on the north side of State Route 2002, however receives much more surface runoff from the golf course (Figure 7) as it travels southwesterly before joining with tributary Upon receiving water from these tributaries, travels south and receives water from a storm sewer discharge located directly south of Heybert Drive (indicated by star on Figure 2). This discharge conveys water from some well-established development as well as some newly developed areas. Upon crossing Strangford Road, travels through a small section of forest before entering a culvert that directs its water into the Conemaugh River. Figure 3. Chestnut Ridge Golf Course, Indiana PA 6

11 Figure 4. Union of tributaries and within the boundaries of the Chestnut Ridge Golf Course. Figure 5. Showing newly developed and transitional land north of SR 2002 that drains into tributary Figure 6. Culvert through which runoff from newly developed land north of SR2002 drains into tributary Figure 7. Pathway of tributary as it travels southwardly along the west edge of Chestnut Ridge Golf Course. 7

12 B. Nature of Impairment and Water Quality Standards Unnamed tributary is impaired, meaning that the health of its water does not meet the standards that have been established for its protected use: Warm Water Fishery. It was placed on Pennsylvania s d list, and both the non-point sources and causes of pollution are shown in table 1. No point sources of pollution, including MS4s (municipal separate storm sewer systems) and CSOs (combined sewer overflows), currently exist within the watershed. Burrell Food Systems held a permit (ID# PA ) in 1997; however, this permit has expired, and the company is currently connected to public sewage. Although storm sewer runoff is a source of impairment, Blairsville is not currently required to obtain MS4 permits; therefore, the load of the discharge will be accounted for in the nonpoint source loads calculated by GWLF (Appendix A). Table 1. Information taken from PA s (d) list showing impairments of tributary Stream Name Unnamed tributary to Conemaugh River Stream Code Source Cause Miles Urban Runoff/Storm Sewer Suspended Solids Agriculture Nutrients 0.7 Agriculture Suspended Solids Although no in-stream water quality criteria exist for these parameters, placement of tributary on the 303(d) list was supported by assessments conducted as a part of the Surface Water Monitoring Program (SSWAP). In this protocol, a biologist collects data to assess the conditions of water chemistry, in-stream as well as surrounding habitat, and invertebrate life. Based on the findings, a professional decision is made as to whether impairment exists to its aquatic life. All warm-water and cold-water fisheries within Pennsylvania are protected to support indigenous aquatic life, and if it is determined that aquatic life is degraded, the stream is deemed impaired. The assessment that deemed segment impaired was conducted many years ago, and subsequently the watershed has changed considerably. At the time when the stream was assessed, agricultural land-uses comprised 71% of the total area of the watershed. Since then, much of this land has been converted to development, and furthermore a large portion of it (40%) has been converted into a golf course (Figure 2). A qualitative re-assessment of the sources and causes of pollution was conducted in March This re-evaluation revealed that nutrient and sediment pollution is arising mainly from runoff from transitional and developed land, and surface runoff from the golf course is exacerbating the problem. Cropland no longer contributes to the pollution in this watershed, and runoff from hay/pasture contributes little. The majority of the sediment pollution appears to arise from 1) drainage from newly developed areas into tributary 44770, and 2) streambank scouring and collapse along all areas of the watershed caused by too high of water volume and velocity. Much of the drainage coming into from newly developed areas is captured by a settling basin located just north of state route 2002 (Figure 8). Upon leaving this basin, the water is joined by another channel of water that also drains areas of this 8

13 development; this channel is muddy, and its streambanks are highly unstable (Figure 9). At this point, there is another smaller settling basin that retains both the outflow from the large basin and the water from the channel previously mentioned. Prior to crossing state route 2002, the water is joined by a storm sewer discharge (Figure 10) that drains developed land in the northwestern section of the watershed. Combined, these waters cross under SR2002 (Figure 11), run south and then west crossing under Strangford Road. The formed stream then runs parallel to Strangford Road before spilling into a large pit (Figure 12). Figure 8. Settling basin that retains runoff from newly developed areas prior to releasing it into tributary Figure 9. Eroded stream channel that drains developed area. This eventually flows into tributary Figure 10. Channel of storm sewer ditch that eventually flows into tributary Figure 11. Outflow of drainage from developed areas north of SR2002 that enter tributary

14 The volume of water that is emitted into this large pit combined with elevation of the culvert pipe through which the water is emitted creates a splash effect that causes much erosion and suspended solids. As shown by figures 12 and 13, the streambanks at this point are highly unstable and eroded. Further downstream the stream s channel is narrowed into two culverts. This appears to accelerate the flow of the tributary, and consequently the streambanks are severely unstable and eroded. Shortly before coalescing with 44769, tributaries and flow through a small designated mitigation wetland. The retention time of the water traveling through the wetland appears to be minimal, and therefore these wetlands likely do not have a significant effect on the sediment load of the water. Moreover, the wetlands do little to slow the flow, as streambanks are severely eroded even downstream of the wetlands (Figure 14). Figure 12. Pit where tributary is drained after forming from drainage from development land. Figure 13. Collapsed streambank of tributary caused by scouring. Figure 14. Severe streambank erosion occurring downstream of where tributaries and travel through mitigation wetlands. 10

15 Pollution from nutrients arises from 1) drainage into tributaries and from newly developed areas, as well as established development, and 2) surface runoff from the golf course. Because the land on which the new development is being established was previously used for agriculture, the soils within are undoubtedly rich with nutrients that remain from years of fertilizing. As discussed earlier, a large amount of sediment is being transported from the areas of development into the stream, but in addition, nutrients that are bound to the sediment also enter the stream. The green tint (planktonic algae) of the water within the large settling basin on the north side of SR2002 that feeds tributary (Figure 8) indicates that nutrients in the runoff are ample, especially considering that the picture was taken in early March, during which time algal productivity is typically low. Although the settling basin serves to drop out sediment, it also serves to culture algae, as no surrounding riparian cover exists around the basin. Even prior to entering the golf course, the substrate of tributary is largely covered with attached algae (Figure 15); this further suggests that this tributary is a significant contributor of nutrient pollution. Tributary also receives water from settling a basin (located on the south side of SR2002) that holds water that comes from development located on the north side of SR2002. The water in this basin is also has a green tint (Figure 16), which suggests the runoff has ample nutrients. Surface runoff from the golf course undoubtedly exacerbates the nutrient impairments within tributary 44771, as this stream travels along the west edge of the course, and no barrier exists to impede surface runoff from entering the stream. Furthermore, the golf course is in direct contact with the lower section of tributary 44769, and this area of stream also has little buffer zone. Figure 15. Stream substrate of tributary covered with periphyton. Figure 16. Settling basin formed by runoff from developed land north of SR2002; basin feeds tributary

16 C. Pollutant Backgrounds, Linkage Analysis, and Endpoints Impairments within the watershed were addressed by targeting sediment and nutrient loading. Suspended solids, which is listed as a cause of impairment in the watershed, is simply a category of sediment pollution. This category refers to small particles of sediment that are carried within the stream flow, and usually originate from the erosion of land outside the channel. Because nutrients, especially phosphorus, are often adsorbed to sediment, an increase in sediment loading to a water body often correlates with an increase in nutrients (USEPA 1992, 1999). Thus, a reduction in sediment loading can address nutrient problems to some extent; however, the exact relationship between these two substances is not well defined, as many factors are involved in their relationship. Therefore, sediment will be addressed in addition to nutrients in this TMDL; although, land management practices that will be recommended to reduce nutrient loading will be similar to those for reducing sediment. 1. Nutrients Nutrients are essential components of any aquatic ecosystem. The two most recognized nutrients are nitrogen (N) and phosphorus (P), which fuel photosynthetic growth of aquatic vegetation such as aquatic plants and algae. The existence of aquatic vegetation is crucial, as it provides food and habitat for animals such as aquatic insects, fish, frogs, and waterfowl. More importantly, it provides (via photosynthesis) the key substance that most aquatic organisms must have to survive: dissolved oxygen. Among other elements, N and P play a direct role in governing growth of aquatic plants; a shortage of either can impede growth, and an excess can accelerate growth to undesirable proportions (Stickney 1994). Because of their ability to proliferate and out-compete aquatic plants, infestations of algae are typically more problematic and receive more attention than do aquatic plants. In most circumstances, however, algae are not problematic, but when nutrients become over-abundant, problems result. Construction activities on landscapes are often contributors of nutrients to nearby streams. These activities loosens soil directly, as well as indirectly by removing plants whose roots once held soil in place. During rainy events, loosened soil is directed toward nearby streams via surface runoff, and depending upon the density of vegetation along the stream bank, sediment enters into the water. Because nutrients are often bound to sediment, an influx of sediment into a stream is typically accompanied by and influx of nutrients (USEPA 1992, 1999). The concentration of added nutrients can be high, especially when development occurs on abandoned agricultural land. This process often occurs due to the practicality of using land that is already cleared and leveled. The soils within are rich in nutrients from decayed organic matter and years of fertilizing; therefore, the effects of this loose and nutrient-rich soil can be catastrophic to streams for many years in retrospect. 12

17 Golf courses have added potential to cause nutrient problems in streams. Plants in naturally vegetated land often have deep roots and grow into thick stands, and therefore are able to uptake a large amount of naturally occurring nutrients. Turf grasses grown within golf courses, however, are manicured meticulously throughout the summer, and have relatively shallow roots. Although their usual high density may sometimes compensate for their shallow roots in terms of nutrient uptake, they are often fertilized repeatedly throughout the summer. These manicured turfs have little ability to impede the flow of water across the surface, and therefore excess nutrients often are washed into nearby streams. Algae in the receiving waters exploit these nutrients, and their populations often explode sometimes engulfing all available substrate. Although they produce oxygen during the day via photosynthesis, algae uptake oxygen from the water during the night; this process is termed respiration. If the algal population becomes dense, dissolved oxygen levels can fall below the requirements of fish and other aquatic inhabitants during the night. Organisms that can directly withstand low levels of oxygen may survive temporarily, however face a constant diurnal fluctuation of dissolved oxygen that may prove to be lethal. In addition to directly causing dissolved oxygen shortages, dense aquatic plant establishments can also render habitat unsuitable for indigenous organisms by slowing the movement of water, which consequently increases thermal loading and decreases dissolved oxygen renewal. Although many short-term methods exist for controlling algae, the only true solution is to limit their food supply: nutrients. A reduction in both N and P can impede algal growth; however, a more practical approach is to reduce the nutrient that most limits growth. Phosphorus is essential to all living organisms, and is often the most growth-limiting element in freshwater ecosystems due to its limited supply (Horne and Goldman 1994). Unlike nitrogen, phosphorus has no gaseous phase, and therefore rainwater carries little or no phosphorus. Furthermore, the little P that is weathered from rocks is quickly absorbed by the root zone on land, or is adsorbed onto particles making it unavailable for uptake by aquatic plant. Although in some circumstances P may not be the limiting nutrient, our analysis shows that it is for this watershed. A common N:P ratio is 10:1, and an increase in this ratio indicates a limitation of P (Horne and Goldman 1994). The ratio for this watershed was determined to be 16:1, which indicates a limitation of P. When phosphorus is limited, a direct and linear relationship exists between the concentrations of P and algae (Horne and Goldman 19964). Therefore, our endpoint was the reduction in P required to render the watershed unimpaired. 13

18 2. Sediment Like nutrients, sediment is an essential component of aquatic ecosystems, as it often contains minerals used by many aquatic organisms, and also provides habitat. Sedimentation is a natural process that is caused by the weathering of landscape, whereby wind and water erode the surfaces of rocks and soils creating small particles. When these particles enter streams, they may flow with the current (suspended solids), or be deposited on the stream-bed. Typically, natural inputs of sediment to streams do not cause problems; however, when landscape is modified whereby soils become unstable, excessive amounts of sediment can enter streams and cause undesirable effects (Bryan and Rutherford 1995). Construction activities on landscapes loosens soil directly, as well as indirectly by removing plants whose roots once held soil in place. During rainy events, loosened soil is directed toward nearby streams via surface runoff, and depending upon the density of vegetation along the stream bank, sediment enters into the water. Often much of the resulting land post-construction is impervious to water, i.e., parking lots, and consequently drainage from this land can be immense. As a result, heavy rains drained from these areas cause higher than normal stream flow that can result severe stream-bank erosion. Golf courses have added potential to cause sediment problems in streams. The roots of plants that exist within naturally vegetated land grow deep into the earth, and therefore are able to retain a large amount of water, and provide adequate stability to stream banks. Also, these plants often grow into thick stands that can impede the flow of water over the surface so that less runoff is available to erode the banks of nearby streams. Roots of turf grasses grown within golf courses are small, and have little bank stability and water retention ability. These grasses are manicured meticulously throughout the summer, and therefore do little to impede the movement of surface water, especially when grasses are often cut to the edge of a stream bank. Resultantly, stream banks near golf course are often steep, unstable, and eroded. Eroded sediment can cause numerous problems for aquatic organisms. Suspended sediment causes turbidity, which can interfere with predation efficiency; cause respiration problems by clogging gills of aquatic organisms (Horne and Goldman 1994); and also reduces sunlight penetration which affects plant photosynthesis (Waters 1995). Causing a higher magnitude of problems, deposited sediment can 1) suffocate eggs of fish and other organisms, 2) suffocate small organisms, 3) severely reduce habitat and habitat diversity, and 4) alter flow patterns (USEPA 1999). Therefore, our endpoint was the reduction in sediment required to render the watershed unimpaired. 14

19 IV. TMDL Development Methods A. Reference Watershed Approach: Setting the Standard The first step of this approach is to find a non-impaired watershed that is similar to the impaired watershed in terms of factors such as land-use, soil associations, drainage area, precipitation, physiographic province, and geology. If both the impaired and reference watershed are closely matched, our model should indicate that both have similar phosphorus and sediment loads. However, by default the model does not account for in-stream nutrient and sediment reductions that may be occurring in the reference watershed in response to existing land management practices. Implementation of these practices is often the reason why the reference watershed is not impaired, whereas the similarly natured impaired watershed is. Ultimately, once land management practices are identified within the reference watershed, the model is adjusted accordingly to reflect the actual loadings. Once an accurate loading rate is determined for the reference watershed, the objective becomes to reduce the loading rate of the impaired watershed to or slightly below that of the reference watershed B. Watershed Assessment Approach and Modeling 1. Reference Watershed Loading Rate The ArcView Generalized Watershed Loading Function (AVGWLF ) model version (described in Appendix A) was used to acquire pertinent information about the watersheds. This model was used to generate the total areas as well as non-point phosphorus and sediment loads of the reference and impaired watersheds. Adjustments were made within the model to account for the land management practices observed to be occurring in the reference watershed, and its loading rate was then determined by dividing its P or sediment load by the total area of its watershed. Reference Watershed Loading Rate = Total P Load (lbs) / Total Area (Acres) = Lbs P / Acre 2. Total Maximum Daily Load This resulting value was then multiplied by the total area of the impaired watershed. This value constitutes the total maximum daily load (TMDL) that the impaired watershed should be able to uptake and still maintain water quality standards, as it is proportional to the load of the reference watershed relative to total area. However, it does not represent the total allowable load; two steps of precaution were employed: a margin of safety (MOS) reduction, and loads not reduced (LNR) reductions. TMDL = Ref Watershed Loading Rate (lbs/acre) x Total Area Impaired Watershed (acres) 15

20 3. Margin of Safety and Load Allocation A margin of safety is a percent of the TMDL that will not be included in the total load that we will allocate among the various pollutant sources. This step is implemented to recognize and account for any uncertainty that may exist between the impairment and what we believe is causing it. Use of a 10% MOS is standard practice in most TMDL reports where water quality criteria are not explicitly defined for the targeted pollutant; this MOS level was used herein. When the MOS and WLA (wasteload allocation) are subtracted from the TMDL, the resulting value constitutes the load allocation (LA), which represents the total load that will be allocated to non-point sources of pollution. Conversely, the wasteload allocation represents the total load that will be allocated to point sources of pollution. MOS (Margin of Safety) = 0.10 x TMDL LA (load allocation) = TMDL (total max daily load) WLA - MOS (margin of safety) thus, TMDL (total max daily load) = LA + WLA + MOS (margin of safety) 4. Adjusted Load Allocation and Loads Not Reduced Loads not reduced (LNRs), are also precluded from the total allowable load. The loads of some pollution sources are uncontrollable; since we cannot control, i.e., reduce the sources load contributions, we must subtract them from the total load that we will allow other sources to emit. We also may preclude a load of a source because its contribution to the total load may be minute, and therefore implementing a land management practice to this source to achieve a load reduction would not be practical, or meaningful. If LNR reductions are implemented, the LA must be adjusted accordingly, consequently producing the ALA (adjusted load allocation). This value constitutes the total load that we will allow, and allocate among the various pollutant sources. ALA (adjusted load allocation) = TMDL MOS (margin of safety) LNRs 5. Load Allocation Distribution and Required Reductions The adjusted load allocation (ALA) was allocated among the pollutant sources using the Equal Marginal Percent Reduction (EMPR) spreadsheet. The computations within this spreadsheet determine the percentage of the ALA that the load of each source constitutes (percent reduction allocation). Each source s load reduction is then produced by multiplying its percent reduction allocation by the ALA. The source s load reduction is then subtracted from its initial load, and its allocated load is produced. For more detail, see Appendix B. 16

21 C. Quality Assurance 1. Consideration of Critical Conditions The AVGWLF model is a continuous simulation model that uses daily time-steps for weather data and water balance calculations. Monthly calculations are made for sediment and nutrient loads based upon the daily water balance accumulated to monthly values. Therefore, all flow conditions are taken into account for loading calculations. Because there is generally a significant lag time between the introduction of sediment and nutrients to a water-body and the resulting impact on beneficial uses, establishing these TMDLs using average annual conditions is protective of the water-body. 2. Consideration of Seasonal Variations The continuous simulation model used for this analysis considers seasonal variation through a number of mechanisms. Daily time steps are used for weather data and water balance calculations. The model requires specification of the growing season and hours of daylight for each month. The model also considers the months of the year when manure is applied to the land. The combination of these actions by the model accounts for seasonal variability. 17

22 V. TMDL Results A. Reference Watershed Selection Using GIS imagery through ArcView, a closely matched reference watershed was found: Tributary to Blacklick Creek, Indiana County (Figure 17). Pennsylvania s 303(d) list indicates that this stream is not impaired. No point sources of pollution, including MS4s (municipal separate storm sewer systems) or CSOs, currently exist within the watershed. Its watershed is adjacent to the watershed of tributary The boundaries of its watershed lie within Burrell Township (USGS quadrangle Bolivar). Its watershed is part of State Water Plan 18-D, and has a total drainage area of 0.42 mi 2. Its water flows for approximately 0.8 miles before joining with tributary to Blacklick Creek Figure 17. Location of the reference watershed (tributary to Blacklick Creek), and the impaired watershed (tributary to Conemaugh River), Indiana County, PA. 18

23 Both GIS imagery through ArcView, and a physical survey indicate that the watershed of tributary is similar to that of tributary Table 2 illustrates the similarities between the watersheds. Because the watershed of tributary was determined to be impaired mainly by runoff from transitional and developed land, it was important to find a reference watershed in which development and transitional land existed. Figure 8 illustrates the distribution of the land-uses within the watersheds. Although the reference watershed does not encompass a golf course as does the impaired watershed, it does encompass substantial cropland. Because the land where the golf course exists was formerly used for agriculture, the underlying soils are suspected to be similar to that of the cropland land in the reference watershed; this is supported by the similar groundwater loads of phosphorus between the watersheds (Table 3). Although the loading rates of sediment and phosphorus for the cropland in the reference watershed are somewhat higher than those of the golf course in the impaired watershed, the differences should be considered minimal and acceptable considering the enormous loads being produced by transitional land in the impaired watershed. Table 2. A comparison of the attributes used to deem tributary a suitable reference watershed to be used in the TMDL development of unnamed tributary ATTRIBUTE Physiographic Province Unnamed Tributary State Water Plan 18D Stream Code Appalachian Plateau Province (Pittsburgh Low Plateau Section) WATERSHED Unnamed Tributary State Water Plan 18D Stream Code Appalachian Plateau Province (Allegheny Mountain Section) Drainage Area (mi 2 ) Land-use Distribution Development 44% Golf Course 40% Hay/Pasture 8% Forested 5% Transitional 3% Development 41% Cropland 18% Hay/Pasture 22% Forested 10% Transitional 8% Geology Interbedded Sedimentary (100%) Interbedded Sedimentary (100%) Soil Associations Hazelton-Dekalb-Buchanan (93%) Monongahela-Philo-Atkins (6%) Gilpin-Wharton-Ernest (1%) Hazelton-Dekalb-Buchanan (93%) Monongahela-Philo-Atkins (6%) Gilpin-Wharton-Ernest (1%) Dominant Hydro Soil Group C C 15-Year Average Rainfall (in) Year Average Runoff (in) Although both the impaired and reference watersheds are similar, runoff from development and transitional land in the reference watershed runs through vast areas of vegetation prior to entering tributary This buffer zone contains a dense formation of grasses, but also consists of thick stands of trees (Figures 18 and 19). This strip acts as a buffer zone, and appears to significantly impede 19

24 the movement of runoff from adjacent land into the stream. Resultantly, although the loads of sediment and nutrients that are produced by both watersheds may be similar, the amount that enters tributary is lesser. This is likely why tributary has been found to not be impaired, whereas tributary was found to be impaired. Figure 18. Illustrating buffer zones of grass impeding the flow of urban runoff into tributary Figure 19. Illustrating buffer zones of trees impeding the flow of urban runoff into tributary

25 B. Pollutant Loads and Reference Watershed Loading Rates 1. Pollutant Loads Table 3. Pollutant loads of sources within watersheds of unnamed tributary 44769, and unnamed tributary (Indiana County). Unnamed Tributary Unnamed Tributary Pollutant Source Area (Acres) Sediment (Tons/yr) Total P (Pounds/yr) Area (Acres) Sediment (Tons/yr) Total P (Pounds/yr) Hay/Pasture Cropland Conif_forest Mixed_forest Decid_forest Transitional Golf Course Low_Dev High_Dev Streambank Groundwater Point Source Septic Sys TOTAL Reference Watershed Loading Rates Reference Watershed Loading Rate = Total P Load (lbs) / Total Area (Acres) = Lbs P / Acre 1. (Sediment) = tons / Acres = tons/acre 2. (Phosphorus) = lbs / Acres = 0.85 lbs/acre 21

26 C. Total Maximum Daily Loads TMDL = Ref Watershed Loading Rate (lbs/acre) x Total Area Impaired Watershed (acres) 1. (Sediment) = tons/acre/yr x 409.9Acres = tons/yr 2. (Phosphorus) = 0.85 lbs/acre/yr x Acres = lbs/yr D. Margins of Safety MOS (Margin of Safety) = 0.10 x TMDL 1. (Sediment) = 0.10 x tons/yr = tons/yr 2. (Phosphorus) = 0.10 x lbs/yr x= lbs/yr E. Load Allocations LA (load allocation) = TMDL (total max daily load) WLA - MOS (margin of safety) 1. (Sediment) = tons/yr 0 tons/yr tons/yr = tons/yr 2. (Phosphorus) = lbs/yr 0 lbs/yr lbs/yr = lbs/yr 22

27 F. Adjusted Load Allocations and Loads Not Reduced Table 4. Loads of pollutant sources that will not be reduced (LNRs). Loads Not Reduced (LNRs) Sediment (Tons/yr) Total P (Pounds/yr) Conif_forest Mixed_forest Decid_forest Hay/Pasture 0.84 High_Dev Low Int Dev Reduced 3.28 Streambank Reduced 0.95 TOTAL ALA (adjusted load allocation) = TMDL MOS (margin of safety) LNRs 1. (Sediment) = tons/yr tons/yr 0.87 tons/yr = tons/yr 2. (Phosphorus) = lbs/yr lbs/yr 5.21 lbs/yr = lbs/yr 23

28 G. Load Allocation Distribution and Required Reductions Table 5. Current and allowable loads and loading rates of SEDIMENT for pollutant sources. Pollutant Source Current Loading Rate (tons/yr) Current Load (tons) Allowable Loading Rate (tons/yr) Allowable Load (tons) Percent Load Reduction Low Int Dev % High Int Dev % Transitional % Golf Course % Streambank % TOTAL Average = 32% Table 6. Current and allowable loads and loading rates of PHOSPHORUS for pollutant sources. Pollutant Source Current Loading Rate (lbs/yr) Current Load (lbs) Allowable Loading Rate (lbs/yr) Allowable Load (lbs) Percent Load Reduction Hay Pasture % Golf Course % Transitional % Groundwater % TOTAL Average = 26% 24

29 VI. Reasonable Assurance and Recommendations Required reductions of sediment and phosphorus loads for non-point pollutant sources in the watershed of unnamed tributary are shown in tables 5 and 6, respectively. If these reductions were attained, the loading level of sediment and phosphorus would become similar to that of the watershed of tributary 44043, which is currently meeting its water quality standards. Reductions of pollutants from non-point sources can be attained by implementing Best Management Practices (BMPs). These land management practices are techniques that can be employed by land owners to either reduce the production of a pollutant, or prevent a pollutant from entering a water body. Each BMP is equipped to handle a unique type of pollutant; although, implementation of a single BMP can sometimes address multiple pollutant problems. Nevertheless, each has its own reduction efficiency, and the optimal BMP is a consideration of its efficiency as well as the feasibility of employing it. Information sheets describing the implementation procedures of BMPs that could be used in the restoration process of this watershed can be found in appendix H. DEP will support local efforts to develop and implement watershed restoration plans based on the reduction goals specified in this TMDL. Interested parties should contact the appropriate Watershed Coordinator in the Department s Southwestern Regional Office ( ) for information regarding technical and financial assistance that is currently available. Individuals and/or local watershed groups interested in the reclamation of the watershed of unnamed tributary are strongly encouraged to exploit funding sources available through DEP and other state and federal agencies (e.g., Growing Greener or 319 Program). 25

30 VII. Public Participation VIII. References USEPA (United States Environmental Protection Agency) TMDL case study: Sycamore Creek, Michigan. EPA841-F U.S. Environmental Protection Agency, Office of Water, Assessment and Watershed Protection Division, Washington, DC USEPA (United States Environmental Protection Agency). 1999a. Protocol for developing nutrient TMDLS. EPA841-B U.S. Environmental Protection Agency, Office of Water, Assessment and Watershed Protection Division, Washington, DC. USEPA (United States Environmental Protection Agency). 1999b. Protocol for developing sediment TMDLS. EPA841-B U.S. Environmental Protection Agency, Office of Water, Assessment and Watershed Protection Division, Washington, DC. Byran, C.F. and D.A. Rutherford Impacts of warmwater streams: Guidelines for evaluation (2 nd Edition). Southern Division, American Fisheries Society, Little Rock, Arkansas. 285 p. Evans, B.M and K.J. Corradini (In Review). BMP pollution reduction guidance document. Environmental Resources Research Institute, Pennsylvania State University, State College, PA. 15p. Horne, A.J. and C.R. Goldman Limnology (2 nd Edition). McGraw-Hill Inc, New York, New York. 576 p. Stickney, R.R Principles of aquaculture. John Wiley & Sons, Inc, New York, New York. 502 p. Waters, T.F Sediment in streams: Sources, biological effects, and control. American Fisheries Society Monograph 7. American Fisheries Society, Bethesda, Maryland. 251 p. 26

31 XI. Appendices Appendix A. AVGWLF Model Overview & GIS-Based Derivation of Input Data. TMDLs for the watershed of unnamed tributary were developed using the Generalized Watershed Loading Function or GWLF model. The GWLF model provides the ability to simulate runoff, sediment, and nutrient (N and P) loadings from watershed given variable-size source areas (e.g., agricultural, forested, and developed land). It also has algorithms for calculating septic system loads, and allows for the inclusion of point source discharge data. It is a continuous simulation model, which uses daily time steps for weather data and water balance calculations. Monthly calculations are made for sediment and nutrient loads, based on the daily water balance accumulated to monthly values. GWLF is a combined distributed/lumped parameter watershed model. For surface loading, it is distributed in the sense that it allows multiple land use/cover scenarios. Each area is assumed to be homogenous in regard to various attributes considered by the model. Additionally, the model does not spatially distribute the source areas, but aggregates the loads from each area into a watershed total. In other words, there is no spatial routing. For sub-surface loading, the model acts as a lumped parameter model using a water balance approach. No distinctly separate areas are considered for sub-surface flow contributions. Daily water balances are computed for an unsaturated zone as well as a saturated subsurface zone, where infiltration is computed as the difference between precipitation and snowmelt minus surface runoff plus evapotranspiration. GWLF models surface runoff using the Soil Conservation Service Curve Number (SCS-CN) approach with daily weather (temperature and precipitation) inputs. Erosion and sediment yield are estimated using monthly erosion calculations based on the Universal Soil Loss Equation (USLE) algorithm (with monthly rainfall-runoff coefficients) and a monthly composite of KLSCP values for each source area (e.g., land cover/soil type combination). The KLSCP factors are variables used in the calculations to depict changes in soil loss erosion (K), the length slope factor (LS) the vegetation cover factor (C) and conservation practices factor (P). A sediment delivery ratio based on watershed size and transport capacities based on average daily runoff are applied to the calculated erosion to determine sediment yield for each source area. Surface nutrient losses are determined by applying dissolved N and P coefficients to surface runoff and a sediment coefficient to the yield portion for each agricultural source area. Point source discharges can also contribute to dissolved losses to the stream and are specified in terms of kilograms per month. Manured areas, as well as septic systems, can also be considered. Urban nutrient inputs are all assumed to be solid-phase, and the model uses an exponential accumulation and washoff function for these loadings. Sub-surface losses are calculated using dissolved N and P coefficients for shallow groundwater contributions to stream nutrient loads, and the sub-surface submodel only considers a single, lumped-parameter contributing area. Evapotranspiration is determined using daily weather data and a cover factor dependent upon land use/cover type. Finally, a water balance is performed daily using supplied or computed precipitation, snowmelt, initial unsaturated zone storage, maximum available zone storage, and evapotranspiration values. 27

32 All of the equations used by the model can be viewed in GWLF Users Manuel, available from the Department s Bureau of Watershed Conservation, Division of Assessment and Standards. For execution, the model requires three separate input files containing transport-, nutrient-, and weather-related data. The transport (TRANSPRT.DAT) file defines the necessary parameters for each source area to be considered (e.g., area size, curve number, etc.) as well as global parameters (e.g., initial storage, sediment delivery ratio, etc.) that apply to all source areas. The nutrient (NUTRIENT.DAT) file specifies the various loading parameters for the different source areas identified (e.g., number of septic systems, urban source area accumulation rates, manure concentrations, etc.). The weather (WEATHER.DAT) file contains daily average temperature and total precipitation values for each year simulated. The primary sources of data for this analysis were geographic information system (GIS) formatted databases. A specially designed interface was prepared by the Environmental Resources Research Institute of the Pennsylvania State University in ArcView (GIS software) to generate the data needed to run the GWLF model, which was developed by Cornell University. The new version of this model has been named AVGWLF (ArcView Version of the Generalized Watershed Loading Function). In using this interface, the user is prompted to identify required GIS files and to provide other information related to non-spatial model parameters (e.g., beginning and end of the growing season, the months during which manure is spread on agricultural land and the names of nearby weather stations). This information is subsequently used to automatically derive values for required model input parameters, which are then written to the TRANSPRT.DAT, NUTRIENT.DAT and WEATHER.DAT input files needed to execute the GWLF model. For use in Pennsylvania, AVGWLF has been linked with statewide GIS data layers such as land use/cover, soils, topography, and physiography; and includes location-specific default information such as background N and P concentrations and cropping practices. Complete GWLF-formatted weather files are also included for eighty weather stations around the state. The following table lists the statewide GIS data sets and provides an explanation of how they were used for development of the input files for the GWLF model. 28

33 Censustr County Gwnback Land-use5 Majored MCD Npdespts Padem Palumrlc Pasingle Physprov Pointsrc Refwater Soilphos Smallsheds Statsgo Strm305 Surfgeol T9sheds Zipcode Weather Files DATASET GIS Data Sets DESCRIPTION Coverage of Census data including information on individual homes septic systems. The attribute usew_sept includes data on conventional systems, and sew_other provides data on short-circuiting and other systems. The County boundaries coverage lists data on conservation practices, which provides C and P values in the Universal Soil Loss Equation (USLE). A grid of background concentrations of N in groundwater derived from water well sampling. Grid of the MRLC that has been reclassified into five categories. This is used primarily as a background. Coverage of major roads. Used for reconnaissance of a watershed. Minor civil divisions (boroughs, townships and cities). A coverage of permitted point discharges. Provides background information and cross check for the point source coverage. 100-meter digital elevation model. This used to calculate landslope and slope length. A satellite image derived land cover grid that is classified into 15 different landcover categories. This dataset provides landcover loading rate for the different categories in the model. The 1:24,000 scale single line stream coverage of Pennsylvania. Provides a complete network of streams with coded stream segments. A shapefile of physiographic provinces. Attributes rain_cool and rain_warm are used to set recession coefficient Major point source discharges with permitted N and P loads. Shapefile of reference watersheds for which nutrient and sediment loads have been calculated. A grid of soil Phosphorus loads, which has been generated from soil sample data. Used to help set phosphorus and sediment values. A coverage of watersheds derived at 1:24,000 scale. This coverage is used with the stream network to delineate the desired level watershed. A shapefile of generalized soil boundaries. The attribute mu_k sets the k factor in the USLE. The attribute mu_awc is the unsaturated available capacity., and the muhsg_dom is used with land-use cover to derive curve numbers. A coverage of stream water quality as reported in the Pennsylvania s 305(b) report. Current status of assessed streams. A shapefile of the surface geology used to compare watersheds of similar qualities. Data derived from a DEP study conducted at PSU with N and P loads. A coverage of animal densities. Attribute aeu_acre helps estimate N & P concentrations in runoff in agricultural lands and over manured areas. Historical weather files for stations around Pennsylvania to simulate flow. 29

34 Appendix B. Equal Marginal Percent Reduction Method The Equal Marginal Percent Reduction (EMPR) allocation method was used to distribute Adjusted Load Allocations (ALAs) between the appropriate contributing non-point sources. The load allocation and EMPR procedures were performed using MS Excel and results are presented in Appendix E for sediment and in Appendix F for phosphorous. The 5 major steps identified in the spreadsheet are summarized below: Step 1: Calculation of the TMDL based on impaired watershed size and unit area loading rate of reference watershed. Step 2: Calculation of Adjusted Load Allocation based on TMDL, Margin of Safety, and existing loads not reduced. Step 3: Actual EMPR Process. a. Each land use/source load is compared with the total ALA to determine if any contributor would exceed the ALA by itself. The evaluation is carried out as if each source is the only contributor to the pollutant load of the receiving water-body. If the contributor exceeds the ALA, that contributor would be reduced to the ALA. If a contributor is less than the ALA, it is set at the existing load. This is the baseline portion of EMPR. b. After any necessary reductions have been made in the baseline, the multiple analyses are run. The multiple analyses will sum all of the baseline loads and compare them to the ALA. If the ALA is exceeded, an equal percent reduction will be made to all contributors baseline values. After any necessary reductions in the multiple analyses, the final reduction percentage for each contributor can be computed. Step 4: Calculation of total loading rate of all sources receiving reductions. Step 5: Summary of existing loads, final load allocations, and % reduction for each pollutant source. 30

35 Appendix C. GWLF Output for Unnamed Tributary