4 FINAL REPORT
Little Neshaminy Creek & Bradford Lake Watershed Assessment
June 30, 2005
Prepared by:
Aqua Link, Inc.
P.O. Box 605 Ph: 215.230.9325 Doylestown, PA 18901 www.aqualinkinc.com
Little Neshaminy Creek & Bradford Lake Watershed Assessment
FINAL REPORT
Little Neshaminy Creek & Bradford Lake Watershed Assessment
Prepared for:
PA Dept. of Environmental Protection Bureau of Watershed Conservation P.O. Box 8555 Harrisburg, PA 17105-8555
Bucks Co. Conservation District 1456 Ferry Road, Suite 704 Doylestown, PA 18901
Prepared by:
Aqua Link, Inc.
P.O. Box 605 Doylestown, PA 18901
Ph: 215.230.9325 www.aqualinkinc.com
Prepared by Aqua Link, Inc. ii Little Neshaminy Creek & Bradford Lake Watershed Assessment
TABLE OF CONTENTS
Section No. Page
ACKNOWLEDGEMENTS ...... viii EXECUTIVE SUMMARY ...... ix 1. INTRODUCTION...... 1 1.1. PROJECT FUNDING AND ADMINISTRATION...... 3 1.2. PAST STUDIES AND INVESTIGATIONS ...... 3 2. LAKE AND WATERSHED CHARACTERISTICS...... 6 2.1. LAKE CHARACTERISTICS ...... 6 2.1.1. Lake Morphological Characteristics...... 6 2.1.2. Lake Uses...... 10 2.2. WATERSHED CHARACTERISTICS ...... 11 2.2.1. Hydrology ...... 12 2.2.2. Topography...... 12 2.2.3. Geology and Soils ...... 12 2.2.4. Land Use ...... 18 3. OVERVIEW OF THE LAKE AND WATERSHED ASSESSMENT...... 23 3.1. PRIMER ON LAKE ECOLOGY AND WATERSHED DYNAMICS...... 23 3.2. STUDY DESIGN AND DATA ACQUISITION...... 26 3.2.1. Lake Water Quality Monitoring Program ...... 26 3.2.2. Lake Bathymetric Survey ...... 27 4. LAKE ASSESSMENT DATA AND RESULTS...... 28 4.1. LAKE WATER QUALITY DATA ...... 28 4.1.1. Temperature and Dissolved Oxygen...... 28 4.1.2. pH, Alkalinity & Hardness...... 31 4.1.3. Specific Conductance...... 33 4.1.4. Total Suspended Solids ...... 34 4.1.5. Transparency ...... 34 4.1.6. Nutrient Concentrations ...... 35 4.1.6.1. Phosphorus...... 36 4.1.6.2. Nitrogen ...... 37 4.1.6.3. Limiting Nutrient...... 38 4.1.7. Plankton and Chlorophyll-a ...... 40 4.1.7.1. Phytoplankton ...... 40 4.1.7.2. Chlorophyll-a ...... 41 4.1.8. Trophic State Index...... 43
Prepared by Aqua Link, Inc. iii Little Neshaminy Creek & Bradford Lake Watershed Assessment
4.2. AQUATIC MACROPHYTES...... 44 4.3. SUMMARY OF LAKE ASSESSMENT DATA ...... 46 5. WATERSHED ASSESSMENT DATA AND RESULTS...... 48 5.1. STREAMS MONITORING PROGRAM...... 48 5.1.1. Study Design and Data Acquisition...... 48 5.1.2. Stream Water Quality Data and Results...... 51 5.1.3. Stream Macroinvertebrate Data...... 52 5.1.4. Stream Data Summary ...... 56 5.2. WATERSHED INVESTIGATION...... 57 5.2.1. Description of the Bradford Lake Watershed...... 57 5.2.2. Major Nonpoint Sources of Pollution...... 59 6. HYDROLOGIC AND POLLUTANT BUDGETS...... 66 6.1. HYDROLOGIC BUDGET...... 66 6.1.1. Major Tributaries ...... 67 6.1.2. Direct Drainage...... 68 6.1.3. Precipitation and Evaporation ...... 68 6.1.4. Hydrologic Budget Summaries ...... 69 6.1.5. Lake Hydraulic Residence Time ...... 69 6.2. POLLUTANT BUDGETS ...... 70 6.2.1. Point Sources ...... 70 6.2.2. Land Uses...... 71 6.2.3. Atmospheric Inputs ...... 72 6.2.4. On-Lot Septic Systems ...... 72 6.2.5. Waterfowl...... 73 6.2.6. Internal Release via In-Lake Sediments...... 73 6.2.7. Pollutant Budget Summaries ...... 74 6.3. PHOSPHORUS MODELING ...... 74 7. EVALUATION OF RESTORATION ALTERNATIVES & PRACTICES ...... 77 7.1. IN-LAKE MANAGEMENT PRACTICES ...... 80 7.1.1. Sediment Dredging ...... 80 7.1.2. Aeration ...... 82 7.1.3. Phosphorus Inactivation...... 84 7.1.4. Algal Control Using Algaecides ...... 85 7.1.5. Aquatic Plant Control Methods ...... 87 7.1.5.1. Aquatic Herbicides...... 88 7.1.5.2. Mechanical Harvesting...... 88 7.2. WATERSHED BEST MANAGEMENT PRACTICES ...... 90 7.2.1. Bank Stabilization & Protection...... 90 7.2.1.1. Streambank Stabilization...... 90 7.2.1.2. Riparian Buffers...... 92
Prepared by Aqua Link, Inc. iv Little Neshaminy Creek & Bradford Lake Watershed Assessment
7.2.2. Stormwater Retrofits...... 93 7.2.3. Conservation & Nutrient Management Plans ...... 96 7.3. INSTITUTIONAL ...... 97 7.3.1. Establishing a Watershed Organization...... 97 7.3.2. Land Acquisition & Protection...... 97 7.3.3. Ordinances for Protecting Water Quality ...... 98 7.3.3.1. Riparian Corridor Protection ...... 98 7.3.3.2. Stormwater Management Ordinance ...... 98 7.3.3.3. Lawn Fertilizer Ordinance...... 99 7.3.4. Point Source Discharges ...... 100 7.3.5. Education ...... 100 7.3.6. Water Quality Monitoring ...... 101 8. COMPREHENSIVE LAKE AND WATERSHED MANAGEMENT PLAN...... 102 8.1. IN-LAKE RESTORATION ...... 102 8.2. WATERSHED BEST MANAGEMENT PRACTICES ...... 103 8.3. INSTITUTIONAL ...... 104 8.4. FUNDING SOURCES ...... 105 9. LITERATURE CITED ...... 108
1005-04 Bradford.rpt.doc
Prepared by Aqua Link, Inc. v Little Neshaminy Creek & Bradford Lake Watershed Assessment
Appendices
Appendix A GPS Coordinate Data and GIS Metafile Data Appendix B Land Use and Soils Data Appendix C Glossary of Lake and Watershed Management Terms Appendix D Bathymetric Survey Data Appendix E Lake Water Quality Data – Summarized by Aqua Link, Inc. Appendix F Original Lake Water Quality Data – Reported by Laboratory Appendix G Stream Water Quality & Discharge Data – Summarized by Aqua Link, Inc. Appendix H Original Stream Water Quality Data – Reported by Laboratory Appendix I Macroinvertebrate Data & Report Appendix J Hydrologic Budget Information & Calculations Appendix K Pollutant Budget and Modeling Calculations
Cover Page
Photographs (from left to right): Bradford (Warrington Lake) on a calm summer morning in 2002. Boat with monitoring equipment at Bradford Lake. Measuring Secchi disk transparency (water clarity) during a survey of Bradford Lake. Gretchen Schatschneider, Watershed Specialist of the Bucks County Conservation District, collecting macroinvertebrates (aquatic organism) in the Little Neshaminy Creek in 2004. All photographs taken by Ed Molesky of Aqua Link, Inc.
Prepared by Aqua Link, Inc. vi Little Neshaminy Creek & Bradford Lake Watershed Assessment
List of Tables
Table No. Page
Table 2.1 Morphologic Characteristics of Bradford Lake...... 10 Table 2.2 Major Soil Series in the Bradford Lake Watershed...... 14 Table 2.3 Land Uses in the Bradford Lake Watershed...... 19 Table 2.4 Percent Land Use in the Bradford Lake Watershed ...... 21 Table 4.1 Annual Mean pH, Alkalinity and Hardness in Bradford Lake in 2002...... 33 Table 4.2 Annual Mean Specific Conductance Values in Bradford Lake in 2002...... 34 Table 4.3 Annual Mean Suspended Solids Concentrations in Bradford Lake in 2002 ...... 35 Table 4.4 Annual Mean Phosphorus Concentrations in Bradford Lake in 2002...... 37 Table 4.5 Annual Mean Nitrogen Concentrations in Bradford Lake in 2002 ...... 38 Table 4.6 Annual Mean Nitrogen to Phosphorus Ratios in Bradford Lake in 2002...... 39 Table 4.7 Mean Carlson’s TSI Values in Bradford Lake in 2002 ...... 43 Table 5.1 Descriptions of Stream Monitoring Stations ...... 48 Table 5.2 Mean Nutrient and Solids Concentrations for All Stream Stations...... 51 Table 5.3 Mean Nutrient and Solids Loadings for All Stream Stations ...... 52 Table 5.4 Macroinvertebrates Identified at all Stream Stations ...... 53 Table 5.5 Calculated Macroinvertebrate Metrics for all Stream Stations ...... 56 Table 6.1 Hydrologic Characteristics of the Little Neshaminy Creek near Neshaminy...... 67 Table 6.2 Hydrologic Characteristics of Major Tributaries to Bradford Lake ...... 68 Table 6.3 Hydrologic Budget for Bradford Lake ...... 69 Table 6.4 Point Source Discharges in the Bradford Lake Watershed ...... 71 Table 6.5 Nutrient Loadings by Point Source Discharges...... 71 Table 6.6 Nutrient and Solids Loadings for Major Subwatersheds...... 72 Table 6.7 Pollutant Budget for Bradford Lake ...... 74 Table 8.1 Recommended Best Management Practices...... 106
Prepared by Aqua Link, Inc. vii Little Neshaminy Creek & Bradford Lake Watershed Assessment
List of Figures
Figure No. Page
Figure 1.1 Political Boundaries of the Bradford Lake Watershed...... 2 Figure 2.1 Bathymetric Map of Bradford Lake ...... 7 Figure 2.2 Topographic Base Map of the Bradford Lake Watershed...... 8 Figure 2.3 Orthophoto Map of the Bradford Lake Watershed ...... 9 Figure 2.4 Soils in the Bradford Lake Watershed ...... 15 Figure 2.5 Land Uses in the Bradford Lake Watershed ...... 20 Figure 2.6 Percent Land Uses in the Bradford Lake Watershed ...... 22 Figure 3.1 Aquatic Food Chain...... 25 Figure 4.1 Temperature Profiles in Bradford Lake (Station WL1) in 2002 ...... 30 Figure 4.2 Dissolved Oxygen Profiles in Bradford Lake (Station WL1) in 2002...... 30 Figure 4.3 Phytoplankton Biomass in Bradford Lake in 2002 ...... 42 Figure 4.4 Phytoplankton Densities in Bradford Lake in 2002 ...... 42 Figure 4.5 TSI Index Values in Bradford Lake in 2002 ...... 44 Figure 5.1 Photographs of the Stream Monitoring Stations ...... 49 Figure 5.2 Location of Photographs in the Bradford Lake Watershed...... 60 Figure 5.3 Photographs of the Bradford Lake Watershed ...... 61
Prepared by Aqua Link, Inc. viii Little Neshaminy Creek & Bradford Lake Watershed Assessment
Acknowledgements
The Little Neshaminy Creek and Bradford Lake Watershed Assessment would not be possible without the financial support of the Pennsylvania Department of Environmental Protection. Funding for this assessment was provided through the state’s Growing Greener Grant Program.
Aqua Link, Inc. and the Bucks County Conservation District would like to thank the County Commissioners and the District Board of Directors for their support of the Little Neshaminy Creek and Bradford Lake Watershed Assessment Project, thereby allowing the District to serve as the Project Sponsor. Aqua Link commends their strong commitment for protecting and restoring the water resources of Bucks County.
Special thanks are extended to the Bucks County Department of Parks and Recreation, Warrington Township and their Environmental Advisory Council, Aqua Pennsylvania, the Montgomery County Conservation District and U.S. Department of Agriculture Natural Resources and Conservation Service (NRCS) for their support of this most noteworthy project.
Aqua Link also would like to thank Mr. John Thomas and Mr. Frederick Groshens, District Manager and Former District Manager, and Ms. Gretchen Schatschneider, Watershed Specialist, of the Bucks County Conservation District for all their hard work and assistance through the entire duration of this project. Lastly, special thanks are extended to Reggie Pena of Warminster for assisting the District in implementing the stream monitoring program for this assessment project.
Edward W. Molesky, CLM President Aqua Link, Inc.
Prepared by Aqua Link, Inc. ix Little Neshaminy Creek & Bradford Lake Watershed Assessment
Executive Summary
Bradford Lake, also known as Warrington Lake and Floodwater Retarding Dam PA-611, is a 22- acre impoundment located off County Line Road in Warrington Township, Bucks County, Pennsylvania. The impoundment was created in 1975 by constructing an earthen dam across the Little Neshaminy Creek. Bradford Lake was primarily built to alleviate flooding along the Little Neshaminy and the Neshaminy Creeks. Secondary uses of this lake include fishing and aesthetics. In addition, visitors use the surrounding 280-acre parkland for walking, hiking and nature watching.
The Bradford Lake watershed, which is the focus of this assessment, is the portion of the Little Neshaminy Creek that drains into the lake. From the lake, the Little Neshaminy Creek travels easterly and eventually discharges into the Neshaminy Creek near Rushland and Wrightstown. The majority of the Bradford Lake watershed lies within Warrington Township in Bucks County and Horsham and Montgomery Townships in Montgomery County.
This report describes the findings of a comprehensive assessment of the Bradford Lake watershed, which includes Bradford Lake and its major tributaries. The lake receives streamflow via the Little Neshaminy Creek and two unnamed tributaries. Aqua Link, Inc. prepared this report for the Bucks County Conservation District. The District served as the project sponsor for this assessment and funding for the project was provided by the Pennsylvania Department of Environmental Protection (PA DEP) through the Growing Greener Grant Program. As part of this assessment, a lake and watershed management plan was developed to improve and further protect the water quality of Bradford Lake and its tributaries.
The lake and watershed management plan was developed using watershed-specific data and information. Watershed data and information were compiled, analyzed and mapped using GIS (Geographical Information System) software. Stream and lake data were collected from April 2002 through May 2005 and subsequently analyzed. Hydrologic and pollutant (nutrients and sediment) budgets were determined for the lake and field investigations were performed in order to identify major sources of nonpoint pollution throughout the entire watershed.
By way of this assessment, Bradford Lake is classified as a very shallow, hypereutrophic impoundment or reservoir. The summer mean Carlson TSI values for total phosphorus, chlorophyll-a and Secchi disk transparency were 73, 58 and 65, respectively. During the study period, the lake contained high concentrations of nutrients, which resulted in large algal blooms (high levels of phytoplankton biomass) and the depletion of dissolved oxygen. In turn, these algal blooms significantly decreased water clarity (Secchi disk transparency) and apparently resulted in taste and odor problems at a water treatment facility near Langhorne. In addition, low dissolved oxygen levels allowed for the buildup of potentially toxic ammonia nitrogen and exacerbated the internal release of nutrients from in-lake sediments. Low levels of dissolved oxygen in conjunction with
Prepared by Aqua Link, Inc. x Little Neshaminy Creek & Bradford Lake Watershed Assessment
elevated ammonia nitrogen concentrations likely impaired the aquatic biota including the lake’s fishery.
Bradford Lake also contains very dense stands of aquatic vegetation that are adversely impairing its recreational uses. By far, the most dominant aquatic plant is water chestnut (Trapa natans). Water chestnut is a highly invasive, exotic plant that has little value as a food source and habitat for native wildlife. Dense mats of water chestnut frequently shade out native plant species, which can significantly impact threatened and endangered species. Decomposition of dying plants can often result in dangerously low dissolved oxygen levels in the fall, thereby creating even more stressful conditions for aquatic life.
The pollutant budgets determined that the major sources of pollution to the lake are classified as nonpoint source (NPS) pollution. By far, most of the nutrients and suspended solids (sediments) to the lake are derived from urban lands that are used for residential housing, commercial shopping centers and manufacturing. Overall, urban lands (the combination residential, commercial, manufacturing and parking) accounted for 65, 50 and 64 percent of all of the phosphorus, nitrogen and sediment loadings to Bradford Lake.
On a subwatershed basis, the pollutant budgets illustrate that the Little Neshaminy Creek subwatershed contributes the highest nutrient and sediment loadings to the lake. The Little Neshaminy Creek delivers approximately 74, 76 and 82 percent of the total phosphorus, nitrogen and suspended solids lake loadings. A significant portion of the nutrient loadings to this stream is related to three, upstream wastewater treatment facilities. These facilities represent about 23 and 14 percent of the phosphorus and nitrogen loadings to the Little Neshaminy Creek.
Stream water quality and hydrologic data strongly indicate that the concentrations and loadings for both nutrients and suspended solids (sediments) increased dramatically during storm events. During storm events, the Little Neshaminy Creek subwatershed contributes significantly more nutrients and sediment (suspended solids) to the lake than the other subwatersheds combined.
The Bradford Lake watershed largely consists of medium density residential lands with some commercial lands that are intermixed with woodlots, fields and agriculture. The majority of the residential homes are located within housing developments and agriculture is generally limited to crop production. The watershed investigation revealed that the most serious threat to lake water quality is land development (active and post construction). Overall, pollutant export during the construction phase can be significant. Pollutant export (sediments with attached nutrients) increases dramatically both during and shortly after construction. Initial clearing and grading operations during construction expose much of the surface soils. Unless adequate erosion controls are installed and maintained at the site, enormous quantities of sediment along with attached nutrients and organic matter are delivered to streams. After construction has been completed, increased stormwater volumes enriched with nutrients are quickly delivered to surface waters from impervious areas, which can result in scouring of streambeds and increased sediment loadings to surface waters.
Prepared by Aqua Link, Inc. xi Little Neshaminy Creek & Bradford Lake Watershed Assessment
The primary goal of the lake and watershed management plan is to reduce nonpoint source pollutants, namely nutrients and sediments, to streams and subsequently the lake itself. This plan consists of key recommendations (in-lake, watershed and institutional best management practices) to improve and further protect stream and lake water quality. Recommended in-lake restoration techniques include sediment dredging, diffused-air aeration, the use of aquatic algaecides and herbicides to control nuisance levels of algae and aquatic vegetation, and mechanical weed harvesting. Recommended watershed best management practices include streambank stabilization; establishing riparian buffers; performing a stormwater retrofit assessment and preparing conservation and nutrient management plans for active farms. Lastly, recommended institutional best management practices include establishing a watershed organization, land acquisition and protection, adopting ordinances for water quality protection, establishing lower phosphorus limits for NPDES point source discharges, environmental education and water quality monitoring of the lake and its tributaries.
Prepared by Aqua Link, Inc. xii Little Neshaminy Creek & Bradford Lake Watershed Assessment
1. Introduction
Bradford Lake, also commonly known as Warrington Lake and Floodwater Retarding Dam PA-611, is a 22-acre impoundment located in Warrington Township, Bucks County, PA. The lake was created in 1975 by constructing an earthen dam across the Little Neshaminy Creek. Documents indicate that the surface area (sediment pool surface area) in 1975 was 28 acres. Bradford Lake was built by the Bucks County Soil and Water Conservation District and the Montgomery County Soil and Water Conservation District with the assistance of Bradford Lake - View from the U.S. Department of Agriculture Soil Dam towards Inlet Conservation Service under the Watershed Protection and Flood Prevention Act. Presently, the conservation and water conservation districts are known as conservation districts and the Soil Conservation Service is known as the Natural Resources and Conservation Service (NRCS). Bradford Lake was primarily constructed to alleviate downstream flooding along the Little Neshaminy Creek and the Neshaminy Creek.
Bradford Lake lies within a 280-acre tract of land owned by the Bucks County Department of Parks and Recreation. The lake and its surrounding parkland are leased to Warrington Township and maintained by both the Township and County. Visitors can gain access to the lake and its surrounding parkland by way of Bradford Road, which is a secondary roadway along County Line Road.
The Bradford Lake watershed, which is the focus of this assessment, is the portion of the Little Neshaminy Creek that drains into the lake. From the lake, the Little Neshaminy Creek travels easterly for about 7.5 miles before it flows into the main stem of the Neshaminy Creek near Rushland and Wrightstown. Park Creek, a major tributary to the Little Neshaminy Creek, empties into the stream about 1 mile downstream the Bradford Lake dam. The Bradford Lake watershed largely lies within Warrington Township in Bucks County and Horsham and Montgomery Townships in Montgomery Townships. Only a small portion of the watershed falls within New Britain Township as shown in Figure 1.1.
Over the years, the water quality and aquatic habitats in Bradford Lake have degraded as a consequence of high loadings of nonpoint source (NPS) pollution. High NPS loadings of nutrients and sediments have resulted in shallowness, dense stands of rooted aquatic plants and massive algal blooms during the summer recreational season. It has generally been assumed that the symptoms of lake eutrophication are associated with high sediment and nutrient loadings from the Little Neshaminy Creek, which is the major tributary to the lake.
Prepared by Aqua Link, Inc. 1 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 1.1 Political Boundaries of the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 2 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Due to the recent water quality concerns, the Bucks Conservation District with the full support of the USDA Natural Resources and Conservation Service (NRCS) and Warrington Township had applied for funding to develop a comprehensive watershed management plan to restore and further protect the Little Neshaminy Creek, Bradford Lake and subsequently the Neshaminy Creek. Funding for this project was provided by PA DEP through the state’s Growing Greener Grant Program.
This report describes the findings of the Bradford Lake watershed assessment that was performed by Aqua Link, Inc. As part of this report, a comprehensive lake and watershed management plan was developed to improve and further protect the water quality of Bradford Lake and its tributaries. The comprehensive lake and watershed management plan for this project was developed using watershed-specific data and information. Watershed data and information were compiled, analyzed and mapped using GIS (Geographical Information System) software. Stream and lake data were collected and subsequently analyzed. Hydrologic and pollutant (nutrients and sediment) budgets were determined for the Bradford Lake watershed. Water quality modeling was performed to corroborate the accuracy of the calculated pollutant budgets and a watershed investigation was performed to identify major sources of NPS pollution to the study lake and its tributaries.
The final product of the Bradford Lake watershed assessment is this detailed report, which assesses the water quality of Bradford Lake and its major streams throughout the watershed. This report also identifies major nonpoint sources (NPS) of pollution to these waters and prioritizes the major subwatersheds on a NPS loading basis. The final report also contains a comprehensive lake and watershed management plan that was developed to reduce NPS pollution to the lake and its tributaries and ultimately the Neshaminy Creek.
1.1. Project Funding and Administration
In March 2001, the Bucks County Conservation District applied for state and federal funding to develop a comprehensive lake and watershed management plan for the Bradford Lake watershed. Aqua Link, Inc. prepared and submitted this grant application on behalf of the District. The Pennsylvania Department of Environmental Protection (PA DEP) later approved the project for funding through the state’s Growing Greener Program. Thereafter, Aqua Link and the District began working on the project in March of 2002. The project was completed in June 2005.
1.2. Past Studies and Investigations
This is the first time the water quality and ecological condition of the Bradford Lake and its tributaries have been extensively assessed. The closest stream water quality monitoring stations are located below the dam along the Little Neshaminy Creek and the Neshaminy Creek. USGS (United States Geological Survey) Station No. 01464907 is part of the National Water Quality Assessment Program and is located about 2 miles downstream of Park Creek and 1.1 miles east of Neshaminy. Station No. 01464907 has been in operation since November 1998 and is monitored for
Prepared by Aqua Link, Inc. 3 Little Neshaminy Creek & Bradford Lake Watershed Assessment
instantaneous discharge, turbidity, dissolved oxygen, pH, specific conductance, temperature, alkalinity, chloride, sulfate, nutrients and pesticides. In addition, USGS Station No. 01465500 is located significantly further downstream near Langhorne. This station, which has been in operation since October 1934, is routinely monitored instantaneous discharge, turbidity, dissolved oxygen, pH, specific conductance, temperature, hardness, alkalinity, ANC, solids, calcium, magnesium, sulfate, nutrients, organic carbon, copper, iron, lead, manganese, nickel and zinc.
In 2003, PA DEP completed a total maximum daily load (TMDL) assessment for the entire Neshaminy Creek Watershed (PA DEP 2003). The Neshaminy Creek TMDL report can be viewed and obtained at the PA DEP website: www.dep.state.pa.us. This assessment was conducted in order to improve the water quality of all the impaired stream segments listed on the State’s 303(d) List of Impaired Streams, which includes the entire main stem of the Little Neshaminy Creek and its primary tributary, Park Creek. Some important facts and findings presented and discussed in the TMDL assessment report are listed below:
• A total maximum daily load (TMDL) sets an upper limit on incoming pollutant loads so that streams and lakes can attain their designated water quality standards.
• The Clean Water Act requires states to list all waters that do not meet their water quality standards. For these waters, the state must calculate how much of a substance can be put in the water without violating the standard. The TMDL assessment report for the Neshaminy Creek includes waste load allocations for point sources and load allocations for nonpoint sources.
• The Clean Water Act requires states to submit their TMDLs to U.S. EPA for approval. If a state does not develop the TMDL, the Clean Water Act states that U.S. EPA must do so.
• In 1996, PA DEP included Neshaminy Creek, two unnamed tributaries to Neshaminy Creek, Little Neshaminy Creek, Park Creek, Cooks Run, West Branch Neshaminy Creek and an unnamed tributary to West Branch Neshaminy Creek on the federal Clean Water Act, Section 303(d) List of Impaired Waters for aquatic life impairments due to nutrients, suspended solids and siltation (sediments).
• More specifically, sources of water quality impairments for aquatic life uses for the Little Neshaminy Creek are urban runoff/stormwater sewers and municipal point sources. It is suspected that urban runoff/storm sewers are causing water/flow variability and siltation. Conversely, municipal point sources are resulting in excessive nutrient in levels in the
Prepared by Aqua Link, Inc. 4 Little Neshaminy Creek & Bradford Lake Watershed Assessment
stream.
• Based upon this assessment, much of the Neshaminy Creek watershed is considered a point source-dominated system. On an annual basis, municipal wastewater treatment facilities contribute about 25 percent of the total phosphorus load.
• During critical low-flow period, effluent discharges from municipal wastewater treatment plants comprise over 90 percent of the total streamflow in many reaches of the Neshaminy Creek.
• Upland erosion from developing areas, agriculture and streambank erosion are other major sources of phosphorus and sediment throughout the Neshaminy Creek watershed. Municipal point sources (wastewater treatment facilities) are also significant sources of nutrients (phosphorus and nitrogen) throughout the Neshaminy Creek watershed.
• The TMDL assessment report provides calculations of the stream’s total capacity to accept phosphorus and sediments. Algae growth in the water bodies is fueled by excess nutrients in the water column. It has been determined that phosphorus is the nutrient limiting productivity in Neshaminy Creek and its tributaries. Therefore, the TMDL report addresses phosphorus to remedy the nutrient impairments. Additionally, sediment loads delivered by stormwater runoff and streambank erosion are impairing the streams in the Neshaminy Creek watershed.
Prepared by Aqua Link, Inc. 5 Little Neshaminy Creek & Bradford Lake Watershed Assessment
2. Lake and Watershed Characteristics
This section primarily discusses the physical characteristics of Bradford Lake and its surrounding watershed. The information provided below is frequently cited throughout the remainder of this report.
2.1. Lake Characteristics
Bradford Lake (40.2298270o N, 75.1610523o W), which is presently a 22-acre impoundment, was created in 1975 by constructing an earthen dam across the Little Neshaminy Creek in Warrington Township, Bucks County, Pennsylvania (Figures 2.1, 2.2 and 2.3). According to PA DEP’s Chapter 93: Water Quality Standards (December 15, 2001), the main stem of the North Branch Neshaminy Creek and its tributaries are classified as WWF (warmwater fishes) and MF (migratory fishes). Therefore, by default, Bradford Lake is also Bradford Lake – View of Main classified as WWF & MF. Access Point to the Lake
2.1.1. Lake Morphological Characteristics
The morphological characteristics of Bradford Lake are shown in Figure 2.1 and presented in Table 2.1. The morphological data were obtained by performing a bathymetric survey of the lake on November 16, 2004. The bathymetric survey is discussed in detail in Section 3.2 – Study Design and Data Acquisition.
Based upon the bathymetric survey, Bradford Lake is considered a very shallow, elongated reservoir or impoundment with its deepest pocket of water located in the vicinity of the dam (Figure 2.1). The surface area of the lake was determined to be 22.2 acres with mean (average) and maximum water depths of 2.4 and 8.2 feet, respectively. The mean sediment depth was 2.5feet and sediment thickness ranged from 1.3 to 3.6 feet along the centerline of the impoundment. The lake receives water from one major and two minor unnamed tributaries The major tributary to the lake is the Little Neshaminy Creek as shown in Figures 2.1 and 2.2. During this assessment, a very large sediment bar was located at the mouth of the Little Neshaminy Creek.
Prepared by Aqua Link, Inc. 6 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 2.1 Bathymetric Map of Bradford Lake
Prepared by Aqua Link, Inc. 7 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 2.2 Topographic Base Map of the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 8 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 2.3 Orthophoto Map of the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 9 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 2.1 Morphologic Characteristics of Bradford Lake
Parameter Bradford Lake
Lake Surface Area (Ao) 22.2 ac (9.0 ha)
Lake Volume 52.3 ac-feet (2.28 x106 ft3 or 6.45 x104 m3)
Mean Water Depth (Z mean) 2.4 ft (0.7 m)
Maximum Water Depth (Z max) 8.2 ft (2.5 m)
Length of Shoreline 1.14 miles (1.83 km)
Historical information recorded on a plaque at the lake states that Bradford Lake (Floodwater Retarding Dam PA-611) has floodwater retarding storage of 2,264 acre-feet. The dam height is 43 feet and has a fill volume of 212,000 cubic yards. Based upon the USDA SCS (1973), the permanent (sediment) pool has a surface area of 28 acres and a storage volume of 110 acre-feet. These values are considerably higher than the values reported in Table 2.1. The more recent, lower values are likely due to the accumulation of sediments in the reservoir over the past 30 years.
2.1.2. Lake Uses
Bradford Lake was primarily built to alleviate flooding along the Little Neshaminy and the Neshaminy Creeks. Secondary uses of the lake include fishing and aesthetics. Boating is prohibited on the lake and the lake’s fishery is not actively managed by the Township, the County or the Pennsylvania Fish and Boat Commission (PA FBC). Visitors also use the surrounding 280 acres of parkland for walking, hiking and nature watching. Bradford Lake – Dense Stands of Overall, the lake and its surrounding Aquatic Vegetation near the parkland are considered highly underused by Access Road the public. This is largely due to the lack of adequate signage along County Line Road and at the parking lot in the vicinity of the dam. In addition, the parkland lacks a trail system to encourage visitors to walk around the lake. The lake also becomes choked with nuisance aquatic vegetation (macrophytes) during the summer
Prepared by Aqua Link, Inc. 10 Little Neshaminy Creek & Bradford Lake Watershed Assessment
recreational season. Dense beds of macrophytes virtually make it impossible to fish the lake during the months of July through September.
Lastly, Aqua Pennsylvania (formerly Philadelphia Suburban Water Company) observed taste and odor problems in 2003 at their water treatment facility near Langhorne, Pennsylvania. This water provider attributed the taste and odor problems to elevated Geosmin concentrations in the Neshaminy Creek. Geosmin is a metabolic by-product that is released by some algae and can result in musty, moldy and earthy taste and odor problems for water supply companies. By way of independent testing, Aqua Pennsylvania claimed that the source of the Geosmin was benthic blue- green algae, namely Oscillatoria, growing along the lake sediments. This water supply company also has claimed that the lake is "seeding " the Little Neshaminy with Oscillatoria, which is allowing for its growth in the downstream in the Little Neshaminy Creek.
In 2004, Aqua Pennsylvania chemically treated the lake with copper sulfate and alum to control elevated, nuisance levels of Geosmin. All chemical treatments were performed under a permit obtained from the PA Fish and Boat Commission. The water provider has claimed that the Geosmin concentrations lowered as a consequence of the chemical treatments and a rainy Spring and Summer. Aqua-Pennsylvania also plans to treat the lake with copper sulfate in 2005 on an as needed basis.
2.2. Watershed Characteristics
Specific data (hydrology, topography, roadways, soils and land use) for the Bradford Lake watershed were obtained from a variety of sources. These data were then analyzed using ArcView GIS (geographical information system) Version 3.2a software with the Spatial Analyst module. For more information about all GIS data sets, refer to the metafile data files included in Appendix A.
The Bradford Lake watershed is approximately 11.0 square miles (7,062 acres) based upon the PA DEP Small Watersheds data file (Figures 2.2 and 2.3). As noted in Section 1.1, the Bradford Lake watershed largely lies within Warrington Township in Bucks County and Horsham and Montgomery Townships in Montgomery County. Only a small portion of the watershed lies within New Britain Township in Bucks County (Figures 1.1 and 2.2). The major roadway that dissects the watershed is County Line Road, which runs in a northwest-southeasterly direction.
For the purposes of this assessment, the Bradford Lake was subdivided into four subwatersheds: the Little Neshaminy Creek (LNC), Unnamed Tributary A (UNTA), Unnamed Tributary B (UNTB) and the direct drainage area (Figure 2.2). The direct drainage area primarily consists of adjacent lands to the lake that discharge surface runoff directly into the lake.
The above subwatersheds are frequently referenced throughout the remainder of this report. In addition, Figure 2.2 shows the locations of the lake and stream monitoring stations. Lake and stream data are discussed extensively in Sections 3 through 5 of this report.
Prepared by Aqua Link, Inc. 11 Little Neshaminy Creek & Bradford Lake Watershed Assessment
2.2.1. Hydrology
The Little Neshaminy Creek (LNC) is by far the most significant tributary to Bradford Lake. This stream drains over 77 percent of the Bradford Lake watershed as illustrated in Figure 2.2. The headwaters of LNC are located in the vicinity of Upper State Road and Route 309 in Montgomeryville. This portion of the watershed is considered highly urbanized. From its headwaters, LNC travels in an easterly direction and eventually discharges into the northwestern end of the lake. The two minor tributaries, Unnamed Tributaries A and B (UNTA and UNTB), drain the northeastern and southeastern sections of the watershed, respectively. Both of these minor tributaries discharge into the upper one-third of the lake as shown in Figure 2.2.
From the lake, the Little Neshaminy Creek travels easterly for about 7.5 miles before it flows into the main stem of the Neshaminy Creek near Rushland and Wrightstown. Park Creek, a major tributary to the Little Neshaminy Creek, empties into the stream about 1 mile downstream of the Bradford Lake dam. The Bradford Lake watershed largely lies within Warrington Township. Lastly, the Neshaminy Creek travels southeasterly from Wrightstown and eventually discharges into the Delaware River near Bridgewater in Lower Bucks County.
2.2.2. Topography
The Bradford Lake watershed is completely contained within the Gettysburg-Newark Lowland Section of the Piedmont Providence. This topographic relief in this section is best described as low to moderate. The dominant topographic forms of this section are rolling lowlands, shallow valleys and isolated hills.
The elevation of Bradford Lake is 246 feet above MSL (mean sea level) as shown in Figure 2.2. The highest elevation, which is 500+ feet, is located in the western portion of the watershed in Montgomeryville.
2.2.3. Geology and Soils
As noted in Section 2.2.2, the Bradford Lake watershed entirely lies within the Gettysburg- Newark Lowland Section of the Piedmont Providence. This section consists mainly of rolling low hills and valleys developed on red sedimentary rock. There are also isolated higher hills developed on diabase, baked sedimentary rock (hornfels) and conglomerates. Almost all of the underlying sedimentary rock dips to the north or northwest and many of the smaller drainageways are oriented normal to the direction of dip so that some of the topography has a northeast-southwest linearity. However, the basic drain-age pattern is dendritic. Soils are usually red and are often have a visually striking contrast to the green of vegetation. Relief is generally in the area of 100 to 200 feet, but locally is up to 600 feet on some of the isolated hills. Elevation in the Section ranges from 20 to 1,355 feet. The Section is made up of sedimentary rocks that were deposited in a long, narrow, inland basin that formed when the continents of North America and Africa separated more than 200
Prepared by Aqua Link, Inc. 12 Little Neshaminy Creek & Bradford Lake Watershed Assessment
million years ago (PA DCNR 2005).
The surficial geology of the Little Neshaminy Creek watershed primarily consists of sandstone of the Stockton formation (66 percent) and the Lockatong shale formation (33 percent). The Stockton formation is the best source for water supply wells in the area although the yields vary considerably. Soils are mostly sandy and very erodible (PA DEP 2003).
~
The Gettysburg-Newark Lowland Section of the Piedmont Providence occurs in southeastern Pennsylvania and extends from the Pennsylvania-Maryland boundary in Adams County across parts of York, Dauphin, Lancaster, Lebanon, Berks, Chester, and Montgomery Counties to the Delaware River in Bucks County. The section is crossed by many roads, which allow the character of the section to be easily viewed. Selected routes are: US Route 30 west and east of Gettysburg; US Route 15 from Dillsburg to Maryland; Pennsylvania Route 94 within the Section; Interstate 76 (Pennsylvania Turnpike) from Harrisburg to Morgantown; US Route 422 from Reading to King of Prussia; and Pennsylvania Route 309 from Emmaus to Fort Washington (PA DCNR 2005).
Prepared by Aqua Link, Inc. 13 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Nineteen different soil types (series) are located throughout the Bradford Lake watershed as shown in Figure 2.4. Of this total, the top ten series represent nearly 96 percent of all soils within the watershed. The top ten frequently occurring soils in the Bradford Lake watershed along with their corresponding percentages are listed in Table 2.2.
Information about the ten most abundant soils in the Bradford Lake watershed is presented below. Soil descriptions were obtained at the USDA NRCS National Soil Survey Center website (www. ortho.ftw.nrcs.usda.gov). For more information about the soils in the watershed, refer to Appendix B of this report.
Table 2.2 Major Soil Series in the Bradford Lake Watershed
Soil Series Percent
Abbottstown 23.9 Doylestown 21.2 Croton 19.7 Reaville 8.4 Bowmansville 6.7 Lansdale 3.9 Chalfont 3.7 Readington 3.6 Lawrenceville 2.5 Buckingham 2.3 Total 95.7
Abbottstown Series
Soils are classified as deep, somewhat poorly drained soils. These soils are on nearly level to sloping concave upland flats, depressions and drainageways. Slopes range from 0 to 15 percent. These soils formed in residuum weathered from noncalcareous red shale, siltstone, and fine-grain sandstone. Soils associated with these soils are Bucks, Chalfont, Croton, Doylestown, Klinesville, Lawrenceville, Penn, Readington and Reaville soils. Drainage and permeability is somewhat poorly
Prepared by Aqua Link, Inc. 14 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 2.4 Soils in the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 15 Little Neshaminy Creek & Bradford Lake Watershed Assessment
drained. Permeability is moderate above the fragipan and slow in and below the fragipan. Runoff class is medium on nearly level slopes, high on gentle slopes and very high on strongly sloping or moderately steep areas. Approximately 85 percent of the Abbottstown soils are used for cropland and pasture. Wooded areas consist of mostly hardwoods, mainly hickory and oak.
Bowmansville Series
Soils are classified as very deep, poorly and somewhat poorly drained. These soils formed in recent alluvial deposits derived from upland soil materials weathered from dolerite or basalt. They are on floodplains with smooth slopes of 0 to 3 percent. Permeability is moderately slow above stratified sand and gravel. Soils associated with these soils are Bermudian, Linden, Roland and the competing Holly soils are on adjacent floodplains. Abbottstown, Bucks, Cheshire, Croton, Holyoke, Klinesville, Lansdale, Lawrenceville, Penn, Readington, and Reaville soils are on nearby uplands. Birdsboro, Branford, Hartford, Manchester, and Raritan soils are on nearby terraces. Bermudian, Birdsboro, Branford, Bucks, Cheshire, Hartford, Lansdale, Linden, Manchester, and Penn soils are all well drained. Abbottstown, Croton, Lawrenceville, Raritan, and Readington soils all have fragipans. Approximately 60 percent of the Bowmansville soils are in pasture. Wooded areas are in mixed hardwood trees.
Buckingham Series
The Buckingham series consists of very deep, somewhat poorly drained soils on head slopes, in drainage ways and U-shaped valleys on hills. These soils are formed in colluvium derived from weathered gray and red shale, siltstone and sandstone materials. Permeability is moderate above the fragipan and slow to moderately slow in the fragipan. Slope ranges from 0 to 8 percent. These soils are commonly associated with Readington, Abbottstown, Croton, and Doylestown soils. Approximately 20 percent of the Buckingham soils are in cropland, 30 percent are in pasture or hayland and 50 percent are in woodland or idle reverting to woodland. Wooded areas are mixed hardwoods.
Chalfont Series
The Chalfont series consists of deep and very deep, somewhat poorly drained soils occurring on nearly level to sloping uplands. These soils formed in a loess mantle overlying a weathered residuum of shale and sandstone. Chalfont soils are associated with the well-drained Duncannon, moderately well drained Lawrenceville, and the poorly drained Doylestown soils. Abbottstown, Chester, Croton, Lansdale, Penn, and Readington are associated soils, which do not have the loess mantle. Most areas with Chalfont soils have been cleared and are used for cropland, hay and pasture. Wooded areas are mixed hardwoods, principally of oaks and yellow poplar.
Prepared by Aqua Link, Inc. 16 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Croton Series
The Croton series consists of deep, poorly drained soils on nearly level and sloping upland flats. These soils formed in medium textured materials mainly over sandstone, siltstone, or shale. Slopes are 0 to 8 percent. These are the better drained than Abbottstown, Readington and Chalfont soils which are on the more sloping areas adjacent to the Croton soils on level areas or depressions. Overall, Croton soils are poor in drainage. Runoff is slow and permeability is slow in the fragipan. Excess water is perched above the fragipan in late winter and early spring but this has been used or has evaporated by summer. These soils are often associated with pin oak, white oak, ash, beech and red maple. Cleared areas are used mostly as pasture, hayland or are idle. A small part is used for growing corn.
Doylestown Series
Soils are classified as deep and poorly drained. The permeability of these soils is moderate in the upper part of the solum and slow to moderately slow in the lower part. These soils are located along foot slopes and toe slopes of nearly level to gently undulating drainageways and broad basins. The parent materials of these soils are silty materials, presumably loess, over soil materials weathered from a variety of parent materials, but principally red shale. Slopes range from 0 to 8 percent and these soils are often associated with Chalfont, Lawrenceville, Bowmansville, and Buckingham, Fountainville, Duncannon, Nockamixon and Amwell soils. Approximately 50 percent of the Doylestown soils are in cropland and the remainder in woodland, pasture or nonfarm uses. Wooded areas consist of water tolerant mixed hardwoods.
Lansdale Series
The Lansdale series consists of deep and very deep, well drained soils on rolling uplands. These soils formed in residuum weathered from sandstone and/or conglomerate. Slopes are 0 to 25 percent. Lansdale soils are often associated with Bucks, Chalfont, Penn, Quakertown, Readington and Steinsburg soils in the same landscape. Chalfont soils have fragipans, Penn and Readington soils are more silty. Lansdale soils are well drained. Runoff is moderate. Permeability is moderate or moderately rapid. These soils are used mostly to grow grass, legumes, small grains, soybeans and corn. They are also extensively used for urban purposes. Wild vegetation is mixed hardwood, chiefly oaks, hickories and yellow poplar.
Lawrenceville Series
Soils are classified as moderately deep to fragipan to very deep and moderately well drained. The permeability of the soils is considered moderate. These soils are located on the side slopes of
Prepared by Aqua Link, Inc. 17 Little Neshaminy Creek & Bradford Lake Watershed Assessment
upland areas. The parent material of the soils is loess from shale-siltstone material over residuum from shale siltstone material. The slopes range from 0 to 15 percent and these soils are often associated with soils of the Duncannon, Chalfont, Readington, Fountainville, Brownsburg, Buckingham and Doylestown series. Largely cleared and in cropland. Woodland areas are oak- hickory mixed hardwoods.
Readington Series
The Readington series consists of deep and very deep, moderately well drained soils occurring on concave, nearly level to sloping lower hillsides, upland flats, drainage ways, and stream heads. The soils formed in medium textured residuum largely from reddish noncalcareous shale, siltstone, and fine-grained sandstone. Slopes range from 0 to 15 slopes. Permeability is moderately slow. Readington soils are in the same landscape as the Abbottstown, Athol, Bucks, Chalfont, Croton, Doylestown, Klinesville, Lansdale, Lawrenceville, Lewisberry, Penn, and Reaville soils. Approximately 85 percent of these soils are used as cropland. Woodland areas are oak-hickory mixed hardwoods.
Readington Series
The Reaville series consists of moderately deep, moderately well, and somewhat poorly drained soils formed in residuum weathered from red Triassic, interbedded shale, siltstone, and fine-grained sandstone. Slopes range from 0 to 15 percent. Permeability is slow. Surface runoff is medium to slow. Soils associated with Reaville soils include Abbottstown, Croton, Klinesville, Lansdale, Penn, Readington and Teas series. Moderately well and somewhat poorly drained. Most of the Reaville soils are cleared and cultivated. Hay, small grain, and corn are the principal crops, and some areas are in pasture. General farming and dairy farming are the main enterprises. The native vegetation was mixed hardwoods, predominantly oaks.
2.2.4. Land Use
The Bradford Lake watershed is best described as an urbanized watershed intermixed with forest and agricultural lands as shown in Table 2.3 and Figure 2.5. Over the past decade, high land development pressures have resulted in the creation of more residential and commercial land uses at the expense of agricultural and forested lands. Presently, residential and commercial land uses (including those land uses associated with land development such as community services, manufacturing, military, parking, transportation, utility, mining) account for 49.9 percent of all land uses in the watershed. Forest (wooded), agriculture and vacant lands only represent 18.6, 17.3 and 7.1 percent of all watershed land uses, respectively.
Prepared by Aqua Link, Inc. 18 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 2.3 Land Uses in the Bradford Lake Watershed
Land Use Area (acres) Percent
Agriculture 1,222 17.3 Wooded 1,317 18.6 Residential 2,692 38.1 Commercial 208 2.9 Community Services 155 2.2 Manufacturing 81 1.1 Military 109 1.5 Parking 188 2.7 Recreation 399 5.6 Vacant 503 7.1 Transportation 10 0.1 Utility 93 1.3 Mining 26 0.4 Water 59 0.8
Total 7,062 100.0
Land use data for the four major subwatersheds are shown in Figures 2.5 and 2.6 and presented in Table 2.4. As noted in Section 2.2, the four major subwatersheds are the Little Neshaminy Creek (LNC), Unnamed Tributary A (UNTA), Unnamed Tributary B (UNTB) and the direct drainage area (Figure 2.2). The direct drainage area primarily consists of adjacent lands to the lake that discharge surface runoff, minor streamflows and shallow groundwater directly into the lake.
By far, the largest subwatershed is the LNC subwatershed as presented in Table 2.4 and shown in Figure 2.5. The LNC subwatershed is 5,453 acres and represents 77 percent of the entire watershed. Conversely, the remaining three subwatersheds (UNTA, UNTB and direct drainage) range from 288 to 852 acres in size. Based upon percentages, most of the residential land uses occur within the LNC and UNTA subwatersheds (Table 2.4 and Figure 2.6). The direct drainage area contains the highest
Prepared by Aqua Link, Inc. 19 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 2.5 Land Uses in the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 20 Little Neshaminy Creek & Bradford Lake Watershed Assessment
percentages of forest (wooded), water and vacant land uses. This is primarily because the direct drainage area contains Bradford Lake and its surrounding parkland. The highest percentages of recreation lands occur within the UNTA and UNTB subwatersheds (Table 2.4 and Figure 2.6). This is due to the occurrence of several golf courses within these subwatersheds.
Table 2.4 Percent Land Use in the Bradford Lake Watershed
Percent Land Use (%) Type of Land Use
LNC UNTA UNTB Direct Agriculture 19.1 2.2 15.4 31.9 Wooded 17.7 18.3 22.7 30.6 Residential 38.6 56.3 15.5 12.9 Commercial 3.0 4.3 1.0 0.7 Community Services 2.5 0.7 3.0 0.0 Manufacturing 1.5 0.0 0.0 0.0 Military 2.0 0.0 0.0 0.0 Parking 3.1 1.8 0.6 0.2 Recreation 2.4 10.3 37.0 1.8 Vacant 7.9 2.1 3.7 13.3 Transportation 0.1 0.9 0.0 0.0 Utility 1.3 2.8 0.0 0.0 Mining 0.5 0.0 0.0 0.0 Water 0.5 0.3 1.1 8.6
Total (Percent) 100.0 100.0 100.0 100.0 Total (Acres) 5,453 852 469 288
Prepared by Aqua Link, Inc. 21 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Percent Land Use
60.0
50.0
40.0
30.0
Percentage (%) 20.0
10.0
0.0 Entire Watershed LNC UNTA UNTB Direct
Agriculture Wooded Resdential Commercial Community Services Manufacturring Military Parking Recreation Vacant Transportation Utility Mining Water
Figure 2.6 Percent Land Uses in the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 22 Little Neshaminy Creek & Bradford Lake Watershed Assessment
3. Overview of the Lake and Watershed Assessment
3.1. Primer on Lake Ecology and Watershed Dynamics
A glossary of lake and watershed terms is provided in Appendix C (U.S. EPA 1980). This glossary is intended to serve as an aid to understanding this section and contains many of the technical terms used throughout this report.
The water quality of a lake is often described as a reflection of its surrounding watershed. The term lake collectively refers to both reservoirs (man-made impoundments) and natural lake systems. Water from the surrounding watershed enters a lake as streamflow, surface runoff and groundwater. The water quality of these water sources is greatly influenced by the characteristics of the watershed such as geology, soils, topography and land use. Of these characteristics, changes in land use (e.g., forested, agriculture, silviculture, residential, commercial, industrial) can significantly alter the water quality of lakes.
Nutrients (e.g., phosphorus, nitrogen, carbon, silicon, calcium, potassium, magnesium, sulfur, sodium, chloride, iron) are primarily transported to lakes via streamflow, surface runoff and groundwater, while sediments are mainly conveyed by streamflow and surface runoff. As streamflow and surface runoff enter a lake, their overall velocity decreases, which allow transported sediments to settle to the lake bottom. Many of these incoming nutrients may be bound to sediment particles and subsequently will also settle to the lake bottom. Very small sediment particles such as clays, may resist sedimentation and subsequently pass through the lake without settling.
Once within the lake, water quality is further modified through a complex set of physical, chemical and biological processes. These processes are significantly affected by the lake’s morphological characteristics (morphology). Some of the more important morphological characteristics of lakes are surface area, shape, depth, volume and bottom composition. In addition, the hydraulic residence time (i.e., the lake’s flushing rate) also greatly affects these processes and is directly related to the lake’s volume and the annual volume of water flowing into the lake.
With respect to nutrients, phosphorus and nitrogen are generally considered the most important nutrients in freshwater lakes. Phosphorus and, to a lesser degree, nitrogen typically determine the overall amount of aquatic plants present. Aquatic plants adsorb and convert available nutrients into energy, which is then used for additional growth and reproduction. In lakes, aquatic plants are mainly comprised of phytoplankton (free-floating microscopic plants or algae) and macrophytes (higher vascular plants). The most readily available form of phosphorus is dissolved orthophosphate (analytical determined as dissolved reactive phosphorus), while ammonia (NH3-N) and nitrate (NO3- N) are the most readily available forms of nitrogen.
Prepared by Aqua Link, Inc. 23 Little Neshaminy Creek & Bradford Lake Watershed Assessment
The transfer and flow of energy in lakes is ultimately controlled by complex interactions between various groups of aquatic organisms (both plants and animals). A simplistic diagram of these interactions among aquatic organisms is shown as Figure 3.1. In Figure 3.1, algae (phytoplankton) and aquatic macrophytes (plants) capture energy from the sun and convert this energy into chemical energy through the process known as photosynthesis. During photosynthesis, carbon dioxide, nutrients, water and captured sunlight energy are used to produce organic compounds (chemical energy), which are then used to support further growth and reproduction.
Energy continues to flow upward through the food chain. Algae are primarily grazed upon by zooplankton. Zooplankton are tiny aquatic animals that are barely visible to the naked eye. Next, zooplankton serve as prey for planktivorous (plankton-eating) fish and larger invertebrates (macroinvertebrates). In turn, plankitvores are consumed by piscivorous (fish-eating) fish. Overall, these aquatic organisms (zooplankton, macroinvertebrates and fish) derive energy by breaking down organic matter through the process known as respiration. During respiration, organic matter, water and dissolved oxygen are converted into carbon dioxide and nutrients.
At the bottom of the food chain (Figure 3.1), particulate organic waste products (excrement) from aquatic organisms along with dead aquatic organisms settle to the lake bottom and are subsequently feed upon by other organisms. Organisms that live or reside along the lake bottom are referred to as benthivores. After settling to the lake bottom, dead organic materials and organic waste products are now called detritus. Some benthivorous fish (catfish and carp) and microorganisms (bacteria, fungi and protozoans) feed upon detritus. Aquatic organisms that feed upon detritus in lakes are referred to as decomposers. Decomposers obtain energy by breaking down detritus (dead organic matter) via the process of respiration. During decomposition, some of the nutrients are recycled back into lake water and can now once again be used by algae and aquatic plants for growth and reproduction. Any unused detritus will accumulate and eventually become part of the lake sediments, thereby increasing the organic content of these sediments.
Ultimately, the amount of nutrients in lakes controls the overall degree of aquatic productivity (Figure 3.1). Lakes with low levels of nutrients and low levels of aquatic productivity are referred to as oligotrophic. Oligotrophic lakes are typically clear and deep with low quantities of phytoplankton and rooted aquatic plants. In these lakes, the deeper, colder waters are generally well-oxygenated and capable of supporting coldwater fish such as trout. Conversely, lakes with high nutrient levels and high levels of aquatic productivity are referred to as eutrophic. Eutrophic lakes are generally more turbid and shallower due to the deposition of sediments and the accumulation of detritus. If deep enough, the bottom waters of eutrophic lakes are generally less oxygenated or may be devoid of dissolved oxygen (anoxic). Eutrophic lakes are often capable of supporting warmwater fish such as bluegill and bass. Mesotrophic lakes lie somewhere in between oligotrophic and eutrophic lakes. These lakes contain moderate levels of nutrients and moderate levels of aquatic productivity.
Prepared by Aqua Link, Inc. 24 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Zooplankton plus others: macroinvertebrates (clams, snails & aquatic insects) & grazing minnows
Phytoplankton (def) : microscopic free-floating algae
Plus, microorganisms like bacteria, fungi & protozoans
Figure 3.1 Aquatic Food Chain
In some instances, the flow of energy through the food web may be disrupted. In hyper-eutrophic (highly eutrophic) lakes, aquatic productivity is extremely high and is dominated by very large numbers of a few, undesirable species. The phytoplankton community is typically comprised largely by blue-green algae during the summer months. Many species of blue-green algae are not readily grazed upon the zooplankton community. Under these conditions, the blue-green algae community is allowed to flourish due to the lack of predation, while the zooplankton community collapses.
Prepared by Aqua Link, Inc. 25 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Decreases in zooplankton biomass in a lake may in turn adversely affect the lake’s fishery. In addition, shallow lake areas may be completely infested with dense stands of aquatic macrophytes and dominated by common carp, catfish or other rough fish.
3.2. Study Design and Data Acquisition
Bradford Lake was intensely studied in 2002 as part of this watershed assessment project. The study design and how data were acquired are described below. For additional information, the approved Quality Assurance – Quality Control Plan for the Warrington (Bradford) Lake and Little Neshaminy Creek Watershed Assessment Project dated April 28, 2002 (Aqua Link, Inc. 2002) should be consulted. This document provides a thorough discussion of the study design along with the rationale behind the study. In addition, this document provides specific information regarding the protocols used to collect field data and the analytical methods used by the contract laboratory.
3.2.1. Lake Water Quality Monitoring Program
One monitoring station for this assessment Measuring Secchi was established at Bradford Lake as shown in Depth Transparency Figures 2.1 and 2.2. Station WL1 (represents at Bradford Lake Warrington Lake also known as Bradford in April 2002 Lake) was located within the deepest section of the lake near the dam. The maximum water depth at this station was 2.3 meters (7.5 feet) during the study period. Station WL1 was monitored once a month during the months of April through September in 2002. All lake water quality samples were collected by boat, which was equipped with an electric motor and a gas-powered outboard motor.
On each of the study dates, surface and bottom water samples were collected at Station WL1. The depths for the collection of surface and bottom samples were defined as one meter below the lake surface and above the lake sediments, respectively. All lake water samples were collected using a Kemmerer vertical water sampler unit. Immediately after collection, water samples were transferred into bottles supplied by the contract laboratory and preserved accordingly in the field. The contract laboratory analyzed all collected lake water samples for alkalinity, total phosphorus, dissolved reactive phosphorus (often referred to as soluble reactive phosphorus or orthophosphorus), total Kjeldahl nitrogen (TKN), ammonia nitrogen, nitrate, nitrite nitrogen, total suspended solids and chlorophyll-a (surface water only). All samples for dissolved reactive phosphorus analysis were filtered in the field using 0.45 micron, 47 mm diameter filter paper.
In addition, dissolved oxygen, temperature, pH, conductivity, specific conductance and
Prepared by Aqua Link, Inc. 26 Little Neshaminy Creek & Bradford Lake Watershed Assessment transparency were monitored in the field on each study date. Dissolved oxygen, temperature, conductivity and specific conductance were measured in the field at 0.5 to 1.0 meter intervals throughout the water column using a YSI 600XL Sonde with a 610D data logger. Transparency was measured in the field using a 20 cm (8 inch diameter) freshwater Secchi disk, which was quartered black and white. The YSI unit was calibrated immediately prior to the collection of any field data for the above water quality parameters.
Lake samples for phytoplankton identification and enumeration were collected on each study date at Station WL1. For phytoplankton samples, three discrete water samples were collected throughout the photic zone of the lake. The photic zone in this study was defined as a depth of two times the Secchi disk depth. Discrete samples were collected using a Kemmerer vertical water sampler unit at the upper, mid-point and lower end of the photic zone and then composited together for analysis. All phytoplankton samples were preserved in the field and subsequently analyzed by Dr. Kenneth Wagner of Wilbraham, Massachusetts.
3.2.2. Lake Bathymetric Survey
On November 16, 2004, Aqua Link performed a preliminary bathymetric survey of Bradford Lake. The survey was performed at various points along transects using a boat equipped with an outboard motor. The locations of all points were recorded in the field using a hand held GPS unit (Garmin Model GPS 76S). For this survey, Aqua Link collected water depth data at 45 different sampling points, which were generally located along 6 different transects (Appendix D). At each point, the location of the boat was accurately determined using the Garmin GPS unit. Next, a calibrated surveying rod was slowly lowered to the lake bottom and this value was recorded as TS, (top of sediment). Therefore, the TS values are equivalent to water depth measurements at each of the sampling point locations.
The depth of unconsolidated sediments in the lake was also estimated during this survey. At six different sampling points along the centerline of the lake, the TS values was recorded and then the calibrated rod was manually forced through the unconsolidated sediments until consolidated materials were struck. Next, these values were recorded and designated as BS (bottom of “unconsolidated” sediment). Thereafter, the depth of unconsolidated sediment was estimated by subtracting the TS values from the BS values (Appendix D).
Data acquired during the bathymetric survey were subsequently analyzed in order to determine key morphological characteristics (e.g., surface area, the mean and maximum water depths, mean depth of unconsolidated sediments and water volume) of Bradford Lake as presented in Section 2.1.1. The lake water volume was determined using the truncated cone methodology (Wetzel 1983), which is presented in Appendix D. The bathymetric data were also used to develop a bathymetric lake map, which was previously shown as Figure 2.1 in Section 2.1.1.
Prepared by Aqua Link, Inc. 27 Little Neshaminy Creek & Bradford Lake Watershed Assessment
4. Lake Assessment Data and Results
Section 4 provides an in-depth discussion of all lake assessment data gathered and analyzed as part of the Bradford Lake watershed assessment. The 2002 lake data are presented and discussed extensively in Section 4.1. Section 4.2 provides an overview of the aquatic macrophyte (higher vascular plants) community in the lake during the study period and Section 4.3 briefly summarizes Sections 4.1 and 4.2 of this report.
As previously discussed in Section 3.2, water quality data for the 2002 study period were collected at Station WL1 (Warrington Lake also referred to as Bradford Lake) as shown in Figures 2.1 and 2.2. In many instances, lake water quality data are presented for different monitoring depths. Surface waters refer to sampling depth of 1.0 meter below the lake’s surface (WL1-S) and bottom waters refer to a sampling depth of 1.0 meter above the lake’s sediments (WL1-B).
For a complete listing of all data acquired and analyzed as part of this lake assessment, refer to Appendices E and F. Refer to Section 3.2 for more information about the study design and data acquisition for this project.
4.1. Lake Water Quality Data
4.1.1. Temperature and Dissolved Oxygen
In late spring or the beginning of summer, many moderately deep to deep temperate lakes develop stratified layers of water. Under stratified conditions, warmer and colder waters are near the lake's surface (epilimnion) and the lake's bottom (hypolimnion), respectively. As the temperature differences become greater between these two water layers, the resistance to mixing increases. During lake stratification, the epilimnion is usually oxygen-rich due to photosynthesis and direct inputs from the atmosphere, while the hypolimnion may become depleted of oxygen due to the respiration of aquatic organisms. As previously discussed, aquatic organisms (e.g., bacteria, fungi, protozoan, zooplankton, macroinvertebrates, fish) consume dissolved oxygen in order to metabolize prey or detritus (U.S. EPA 1980, U.S. EPA 1990 and U.S. EPA 1993).
Conversely, shallow temperate lakes may only become weakly stratified during the summer months or some lakes may never stratify at all. The overall degree and duration of stratification in weakly stratified lakes are largely dependent upon local wind conditions and the morphological characteristics of the lake itself. During windy days, surface wave action may be sufficient to partially or completely destratify (mix) a lake. Conversely, a shallow lake may become partially stratified on windless days.
Overall, water temperatures and dissolved oxygen concentrations are very important with regards to a lake’s fishery. In general, the optimal water temperature for salmonid fish (i.e., trout) is
Prepared by Aqua Link, Inc. 28 Little Neshaminy Creek & Bradford Lake Watershed Assessment
55 to 60 EF (12.8 to 15.6 EC). Trout may withstand water temperatures above 80 EF (26.7 EC) for several hours, but if water temperatures exceed 75 EF (23.9 EC) for extended periods, high trout mortality is expected (Pennsylvania State University). Conversely, non-salmonid fish such as golden shiners, bass, bluegills, can grow well even when water temperatures exceed 80 EF (26.7 EC). In general, safe minimum dissolved oxygen concentrations for adult salmonid and non-salmonid fish are 5.0 and 3.0 mg/L, respectively. When dissolved oxygen concentrations fall below these concentrations, production impairment of the lake’s fishery can be expected.
In addition to impacting the lake’s fishery, low dissolved oxygen levels in the bottom waters of a lake will often accelerate the release of nutrients such as soluble orthophosphorus (analytically measured as dissolved reactive phosphorus) and ammonia nitrogen, from anoxic (oxygen depleted) in-lake sediments. In particular, the accelerated release rates of nutrients (referred to as internal loading) can represent a substantial portion of all incoming nutrients to a lake. Increased nutrient loadings via in-lake sediments may further degrade lake water quality by increasing the production of both phytoplankton and aquatic macrophytes (vascular plants).
Bradford Lake
The 2002 water temperature and dissolved oxygen profile data for Bradford Lake are graphically presented in Figures 4.1 through 4.2, respectively. The maximum water depth at Station WL1 was only 2.3 meters (7.6 feet). Overall, Bradford Lake is considered a very shallow impoundment (reservoir) with its deepest section located near the dam.
Water temperatures in the lake were very uniform in April, August and September as shown in Figure 4.1. Uniform water temperatures indicate that the lake was actively mixing or turning over. By May, the lake was strongly, thermally stratified and remained stratified through July (Figure 4.1). The greatest degree of thermal stratification was observed in May. On May 30th, the surface (epilimnion) and bottom (hypolimnion) water temperatures were 23.6o C (74.5o F) and 14.0o C (57.2o F), respectively. Overall, this degree of thermal stratification is quite unusual for such a shallow lake system.
Dissolved oxygen concentrations were strongly stratified when the lake was thermally stratified during the months of May, June and July (Figure 4.2). In June and July, the dissolved oxygen levels typically fell below 1.0 mg/l for water depths exceeding 1.5 meters (4.9 feet). The highest dissolved oxygen levels for the epilimnion was recorded in May when phytoplankton biomass peaked during the study period (refer to Section 4.1.7). Excessively high dissolved oxygen levels on the May study date are attributed to extremely high rates of photosynthesis by phytoplankton and aquatic plants in the lake. Conversely, dissolved oxygen levels were very low and uniform throughout the water column in August and September. The dissolved oxygen concentrations ranged from 0.25 to 0.96 mg/L and 2.38 and 2.82 mg/L on the August and September study dates, respectively (Figure 4.2). These uniform, low dissolved oxygen concentrations may be related to low streamflow, thereby reducing
Prepared by Aqua Link, Inc. 29 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Temperature Profiles in Bradford (Warrington) Lake
Temperature (Degrees Celsius) 10.0 15.0 20.0 25.0 30.0 0.0
0.5
1.0
1.5 Depth (meters)
2.0
2.5
4/30/2002 5/30/2002 6/26/2002 7/31/2002 8/22/2002 9/26/2002
Figure 4.1 Temperature Profiles in Bradford Lake (Station WL1) in 2002
Dissolved Oxygen Profiles in Bradford (Warrington) Lake
Dissolved Oxygen Concentration (mg/l) 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 0.0
0.5
1.0
1.5 Depth (meters)
2.0
2.5
4/30/2002 5/30/2002 6/26/2002 7/31/2002 8/22/2002 9/26/2002
Figure 4.2 Dissolved Oxygen Profiles in Bradford Lake (Station WL1) in 2002
Prepared by Aqua Link, Inc. 30 Little Neshaminy Creek & Bradford Lake Watershed Assessment
the overall hydraulic residence time (flushing rate) of the reservoir. Under such conditions, it is plausible that upstream point sources (i.e., wastewater treatment facilities) may be exerting a high biological oxygen (BOD) demand on the lake.
Based on the above data, Bradford Lake is classified as a very shallow, polymictic lake. Polymictic lakes are those lakes that can thermally stratify and destratify (mix) throughout the growing season (May through September). Overall, water temperature and dissolved oxygen data for the study period indicate that the lake will result in stressful conditions and production impairment for salmonid (coldwater) game fish species like trout. Low dissolved oxygen levels in August and September also suggest extremely stressful conditions and production impairment for non-salmonid (warmwater) game fish species such as largemouth bass and bluegills.
Low dissolved oxygen levels at the lake water-sediment interface in June through August 2002 suggest that in-lake sediments are promoting the internal release of nutrients. Low dissolved oxygen concentrations also are allowing for the buildup of hydrogen sulfide gas and the formation of toxic ammonium nitrogen. The release of soluble nutrients via sediments and the formation of hydrogen sulfide and ammonium nitrogen dramatically increase when dissolved oxygen levels in lake bottom waters are less than 1.0 mg/L.
4.1.2. pH, Alkalinity & Hardness
The pH and alkalinity of water are directly related to one another. In general, as alkalinity increases, the pH of the water also increases. The acidity or basicity of a solution is most often expressed as pH. The term pH is defined as the logarithm of the reciprocal (or its negative logarithm) of the hydrogen ion concentration. Therefore, a one unit change in pH represents a ten- fold increase or decrease in the hydrogen ion concentration (as pH decreases, the hydrogen ion concentration increases). The pH scale ranges 0 to 14 standard units where a value of 7 indicates neutral conditions. Water becomes more acidic when pH values fall below 7 and more basic when pH values rise above 7. In general, most natural waters usually have a pH values between 6.5 and 8.5.
Aquatic life in lakes can be adversely impacted when pH levels drop too low in lakes. When pH concentrations fall below 6.0 standard units, there is a greater risk to increase the concentration of heavy metals, in particular aluminum. High concentrations of hydrogen and aluminum ions are known to adversely affect the ion regulation of aquatic organisms, a condition referred to as "osmoregulatory failure". When osmoregulatory failure occurs, high hydrogen and aluminum concentrations induce the leaching of sodium and chloride ions from the body fluids of fish and other aquatic organisms (U.S. EPA, 1990). As summarized by J. Baker, pH values ranging from 5.5 to 6.0 standard units can result in the loss of sensitive minnows and dace, which may be important as forage fish for game fish. In addition, the pH levels below 6.0 are also known to adversely affect the reproductive success rates of game fish, such as walleye (U.S. EPA, 1990). Alkalinity refers to the capacity of water to neutralize (or buffer against) acid inputs. Alkalinity
Prepared by Aqua Link, Inc. 31 Little Neshaminy Creek & Bradford Lake Watershed Assessment
- - of natural waters is due primarily to the presence of hydroxides (OH ), bicarbonates (HCO3 ), 2- carbonates (CO3 ) and occasionally borates, silicates and phosphates. Therefore, the carbonate– - 2- bicarbonate equilibrium system (CO2 - HCO3 - CO3 ) is the major buffering mechanism in freshwater lakes (Wetzel 1983).
Alkalinity is typically expressed in units of milligrams per liter (mg/l) of CaCO3 (calcium carbonate). Waters having a pH below 4.5 contain no alkalinity. Low alkalinity is the main indicator of susceptibility of aquatic organisms to acidic inputs (e.g., acid rain and acidic dry fallout). Waters - with pH values ranging from 6 to 9 are largely comprised of bicarbonate (HCO3 ). At higher pH = values, carbonate (CO3 ) plays a more important role in the buffering capacity of the water. Lakes with watersheds that contain sedimentary carbonate rocks are high in dissolved carbonates (hard- water lakes). Conversely, lakes in granite or igneous rocks are low in dissolved carbonates (soft water lakes). In the Northeastern U.S., the alkalinity of natural surface waters typically ranges from 5 to over 200 mg/L as CaCO3.
Hardness is the amount of dissolved calcium and magnesium and to a lesser extent, other divalent and trivalent metallic elements such as iron, manganese and aluminum. The term hardness was originally derived to describe waters that were hard to wash clothing, thereby referring to the soap washing properties of water. Hardness prevents soap from lathering by causing the development of an insoluble precipitates in the water. Hardness typically causes the buildup or “scaling” of precipitates in pipes and water heaters and can cause numerous problems in laundry, kitchen, and bath facilities. Overall, dissolved calcium and magnesium salts are primarily responsible for most scaling problems. Hardness is often described as soft, slightly hard, moderately hard, hard and very hard. Soft water is less than 17 mg/L as calcium carbonate (CaCO3). Slightly hard water is greater than 17 to 60 mg/L as CaCO3. Moderately hard water is greater than 60 to 120 mg/L as CaCO3. Hard water is greater than 120 to 180 mg/L as CaCO3, while very hard water is above 180 mg/L as CaCO3.
Bradford Lake
The 2002 annual mean pH values for surface and bottom waters are presented in Table 4.1. Overall, the surface and bottom waters are considered moderately basic and near neutral. The higher mean values for the surface waters were due to increased levels of photosynthesis by phytoplankton in the epilimnion (surface waters).
The 2002 annual mean alkalinity concentrations for surface and bottom waters are shown in Table 4.1. Lower concentrations in the surface waters were attributed to the higher consumption rates of dissolved carbon dioxide (CO2) by phytoplankton during photosynthesis. Higher concentrations in the bottom waters (hypolimnion) were likely due to alkaline enriched groundwater inputs and the production of dissolved carbon dioxide (CO2) during respiration by benthic organisms. In general, the alkalinity concentrations in the lake are considered moderately high and are thereby sufficient to regulate or maintain stable pH levels. Furthermore, the lake is not highly
Prepared by Aqua Link, Inc. 32 Little Neshaminy Creek & Bradford Lake Watershed Assessment
susceptible to acidic inputs such as, acid rain, acidic runoff from snowmelt and acidic dry deposition. When acidic inputs are episodically high, it is expected that pH levels in the lake will remain stable, thereby protecting acid intolerant aquatic organisms.
The mean hardness concentrations are similar for both surface and bottom waters as shown in Table 4.1. The hardness concentrations indicate that the surface and bottom lake waters are classified as hard.
Table 4.1 Annual Mean pH, Alkalinity and Hardness in Bradford Lake in 2002
pH Alkalinity Hardness (standard units, s.u.) (mg/l as CaCO3) (mg/l as CaCO3) Station Surface Bottom Surface Bottom Surface Bottom
WL1 7.50 6.86 144 163 151 162
4.1.3. Specific Conductance
Conductivity is a measure of the ability of water to conduct an electric current and is dependent on the number of dissolved ions in solution. Although directly correlated to the total amount of dissolved solids, conductivity provides no indication with regards to the relative quantities of the various types of dissolved solids present. Observed conductivities in lake waters vary widely and are largely a function of the geology and the soils in the watershed. Conductivity varies significantly with temperature and to a lesser extent with the nature of the individual ions present. Because temperature has a relatively large effect on conductivity, conductivity is typically corrected to 25EC and reported as specific conductance (in micro Siemens, uS/cm @ 25EC) to allow direct comparison of values that were measured at different temperatures.
Bradford Lake
The 2002 annual mean specific conductance values for surface and bottom waters are presented in Table 4.2. Overall, these values are very high and strongly suggest hypereutrophic lake conditions. The highest values were observed in the bottom waters, thereby indicating higher amounts of dissolved solids, which includes soluble forms of nutrients like phosphorus and nitrogen. The higher concentrations in the bottom waters may be attributed to the decay of organic matter including dead phytoplankton, the release of nutrients from anoxic (oxygen depleted) in-lake
Prepared by Aqua Link, Inc. 33 Little Neshaminy Creek & Bradford Lake Watershed Assessment
sediments and higher alkalinity concentrations. The release of nutrients from anoxic sediments dramatically increases when the lake is thermally stratified. Under such conditions, the mixing of surface and deep lake waters is suppressed, thereby allowing the bottom waters to remain isolated and undergo anoxic (oxygen depleted conditions).
Table 4.2 Annual Mean Specific Conductance Values in Bradford Lake in 2002
Specific Conductance (µS/cm) Station Surface Bottom
WL1 629 713
4.1.4. Total Suspended Solids
The concentration of total suspended solids in a lake is a measure of the amount of particulate matter in the water column. Suspended solids include both organic matter including phytoplankton and inorganic materials like soil particles.
Bradford Lake
The 2002 annual mean total suspended solids concentrations in the lake are presented in Table 4.3. The concentrations for surface and bottom waters are considered very high, respectively. These concentrations are typical for productive lake systems and are indicative of high levels of aquatic productivity in the form of phytoplankton and/or high sediment loadings from the surrounding watershed.
4.1.5. Transparency
The transparency, or clarity, of a lake is most often reported as the Secchi disk depth. This measurement is taken by lowering a circular black-and-white disk, which is 20 cm (8 inches) in diameter, into the water until it is no longer visible. Observed Secchi disk depths range from a few centimeters in very turbid lakes to over 40 meters in the clearest known lakes (Wetzel, 1983). Although somewhat simplistic and subjective, this field monitoring method probably best represents those lake conditions that are most often perceived by lake users and the general public.
Prepared by Aqua Link, Inc. 34 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 4.3 Annual Mean Suspended Solids Concentrations in Bradford Lake in 2002
Total Suspended Solids (mg/l) Station Surface Bottom
WL1 16.8 12.8
Secchi disk transparency is related to the transmission of light in water, and depends on both the absorption and scattering of light. The absorption of light in dark-colored waters reduces light transmission. Light scattering is usually a more important factor than absorption in determining Secchi depths. Scattering can be caused by water discoloration or by the presence of both particulate organic matter (e.g., algal cells) and inorganic materials (e.g., suspended clay particles).
In general, a lake is classified as oligotrophic, mesotrophic, eutrophic and hypereutrophic when Secchi disk transparency values are greater than 4.0 meters, 2.0 to 4.0 meters, 1.0 to 1.9 meters and less than 1.0 meter, respectively (Nurnberg 2001).
Bradford Lake
The 2002 annual mean Secchi disk transparency value for Bradford Lake was 0.75 meters. Based upon Nurnberg (2001), the lake is classified as hypereutrophic. Secchi disk transparency values ranged from 0.21 to 1.45 meters for all study dates. It should be noted that the lowest transparency values occurred when the highest phytoplankton biomass levels were recorded in the lake as discussed in Section 4.1.7.
4.1.6. Nutrient Concentrations
Phosphorus and nitrogen are major nutrients required for the growth of phytoplankton (free floating, microscopic plants) and macrophytes (aquatic vascular plants) in lakes. The lake monitoring program for this study included the analysis of lake samples for both total and dissolved inorganic forms of both nutrients. The dissolved inorganic nutrients, namely dissolved reactive phosphorus, nitrate, and ammonia nitrogen, are regarded as the forms most readily available to support aquatic plant growth, while the total nutrient amounts provide an indication of the maximum growth potential that could be achieved in lakes.
Prepared by Aqua Link, Inc. 35 Little Neshaminy Creek & Bradford Lake Watershed Assessment
4.1.6.1. Phosphorus
Total phosphorus represents the sum of all forms of phosphorus. Total phosphorus includes dissolved and particulate organic phosphates (e.g., algae and other aquatic organisms), inorganic particulate phosphorus as soil particles and other solids, polyphosphates from detergents and dissolved orthophosphates. Soluble (or dissolved) orthophosphate (determined analytically as dissolved reactive phosphorus) is the phosphorus form that is most readily available for algal uptake. Soluble orthophosphate is usually reported as dissolved reactive phosphorus because laboratory analysis takes place under acid conditions and may result in the hydrolysis of some other phosphorus forms. Total phosphorus levels are strongly affected by the daily phosphorus loadings to a lake, while soluble orthophosphate levels are largely affected by algal consumption during the growing season.
Based on criteria established by Nurnberg (2001), a lake is classified as oligotrophic, mesotrophic, eutrophic and hypereutrophic when surface total phosphorus concentrations are less than 0.010 mg/l as P, 0.010 to 0.030 mg/l as P, 0.031 to 0.100 mg/l as P and greater than 0.100 mg/l as P, respectively.
Bradford Lake
The 2002 annual mean total phosphorus concentrations for surface and bottom waters were 0.120 and 0.130 mg/l as P (Table 4.4). Total phosphorus concentrations ranged from 0.070to 0.180 mg/l as P for surface waters and 0.100to 0.160 mg/l as P for bottom waters. Based upon the above criteria, the mean annual total phosphorus concentrations for surface waters suggest that Bradford Lake is classified as hypereutrophic in 2002.
The 2002 annual mean dissolved reactive phosphorus concentrations for surface and bottom waters were 0.022 and 0.034 mg/l as P (Table 4.4). Dissolved reactive phosphorus concentrations ranged from less than 0.005 to 0.055 mg/l as P for surface waters and from 0.010 to 0.067 mg/l as P for bottom waters. The detection limit for dissolved reactive phosphorus as reported by the contract laboratory was 0.010 mg/l as P. Although low, the presence of dissolved reactive phosphorus in the surface waters suggest excessive available amounts of phosphorus for primary production. In most instances, lakes contain very low dissolved reactive phosphorus concentration (at or below the detection limit) because this form of phosphorus is rapidly used by phytoplankton as soon as it becomes available. Conversely, slightly higher concentrations in the bottom waters suggest that the internal release from anoxic sediments may be significant source of phosphorus to the lake.
Prepared by Aqua Link, Inc. 36 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 4.4 Annual Mean Phosphorus Concentrations in Bradford Lake in 2002
Total Phosphorus Dissolved Reactive Phosphorus Station (mg/l as P) (mg/l as P)
Surface Bottom Surface Bottom
WL1 0.120 0.130 0.022 0.034
4.1.6.2. Nitrogen
Nitrogen compounds are also important for the growth and reproduction of phytoplankton and - aquatic macrophytes. The common inorganic forms of nitrogen in water are nitrate (NO3 ), nitrite - + (NO2 ) and ammonia (NH3). In water, ammonia is present primarily as ammonium (NH4 ) and undissociated ammonium hydroxide (NH4OH). Of these two forms, undissociated ammonium hydroxide is toxic and its toxicity increases as pH and water temperature increase. Overall, the most dominant form of inorganic nitrogen present in lakes depends largely on the dissolved oxygen concentrations. Nitrate is the form usually found in surface waters, while ammonia is only stable under anaerobic (low oxygen) conditions. Nitrite is an intermediate form of nitrogen, which is generally considered unstable. Nitrate and nitrite (referred to as total oxidized nitrogen) are often analyzed together and reported as NO3 + NO2-N, although nitrite concentrations are usually insignificant as noted previously. Total Kjeldahl nitrogen (TKN) concentrations include ammonia and organic nitrogen (both soluble and particulate forms). Organic nitrogen can be easily estimated by subtracting ammonia nitrogen from total Kjeldahl nitrogen concentrations. Total nitrogen is calculated by summing the nitrate-nitrite, ammonia and organic nitrogen fractions together.
According to Nurnberg (2001), lakes with surface total nitrogen concentrations less than 0.350 mg/l as N are classified as oligotrophic, from 0.350 to 0.650 mg/l as N are classified as mesotrophic, from 0.651 to 1.200 mg/L are classified as eutrophic and greater than 1.2000 mg/l as N are classified as hypereutrophic.
Bradford Lake
The 2002 annual mean total nitrogen, total Kjeldahl nitrogen (TKN), nitrate plus nitrite nitrogen and ammonia nitrogen concentrations for surface and bottom waters are presented in Table 4.5. Overall, the mean total nitrogen concentration for the surface waters was slightly higher than the
Prepared by Aqua Link, Inc. 37 Little Neshaminy Creek & Bradford Lake Watershed Assessment
mean concentration for the bottom waters. This slightly higher value is likely attributed to higher levels of phytoplankton in epilimnion. This is because the TKN values in the surface waters were greater than the bottom waters and the nitrate + nitrite and ammonia concentrations were similar for both surface and bottom waters. Therefore, the surface waters contained slightly higher amounts of organic nitrogen, which is largely comprised of phytoplankton in lake systems.
Table 4.5 demonstrates another interesting point with respect to ammonia. Ammonia concentrations were measured in both the surface and bottom waters of Bradford Lake. This is very unusual, especially for the surface waters, since most shallow lakes are generally well mixed and oxygenated, thereby not allowing ammonia to form. The elevated levels of ammonia in Bradford Lake is likely due to its release via anoxic in-lake sediments and point source loadings from upstream wastewater treatment facilities. The persistent of ammonia levels in the surface waters is attributed to very low dissolved oxygen in the epilimnion as discussed in Section 4.1.1.
Table 4.5 Annual Mean Nitrogen Concentrations in Bradford Lake in 2002
Total Total Kjeldahl Nitrate + Nitrite Ammonia Station Nitrogen Nitrogen (mg/l as N) (mg/l as N) (mg/l as N) (mg/l as N)
Surface Bottom Surface Bottom Surface Bottom Surface Bottom
WL1 0.56 0.36 0.43 0.28 0.13 0.08 0.08 0.08
Based upon the Nurnberg criteria (2001), the annual mean total nitrogen concentrations for surface waters are moderately high and thereby suggesting that Bradford Lake was classified as highly mesotrophic in 2002.
4.1.6.3. Limiting Nutrient
Phytoplankton growth depends on a variety of nutrients. This includes macronutrients (phosphorus, nitrogen and carbon) as well as trace nutrients (iron, manganese and many others). According to Liebig's law of the minimum, biological growth is limited by the substance that is present in the minimum quantity with respect to the needs of the organism. Nitrogen and phosphorus are usually the nutrients limiting algal growth in most natural waters.
Depending on the species, algae require approximately 15 to 26 atoms of nitrogen for every atom
Prepared by Aqua Link, Inc. 38 Little Neshaminy Creek & Bradford Lake Watershed Assessment
of phosphorus. This ratio converts to 7 to 12 mg of nitrogen per 1 mg of phosphorus on a mass basis. A ratio of total nitrogen to total phosphorus of 15:1 is generally regarded as the dividing point between nitrogen and phosphorus limitation (U.S. EPA, 1980). Identification of the limiting nutrient becomes more certain as the total nitrogen to total phosphorus ratio moves farther away from the dividing point, with ratios of 10:1 or less providing a strong indication of nitrogen limitation and ratios of 20:1 or more strongly indicating phosphorus limitation.
In many instances, inorganic nutrient concentrations provide a better indication of the limiting nutrient because the inorganic nutrients are the forms directly available for algal growth. Ratios of total inorganic nitrogen (TIN = ammonia, nitrate, and nitrite) to dissolved reactive phosphorus (DRP) greater than 12 are indicative of phosphorus limitation, ratios of TIN:DRP less than 8 are indicative of nitrogen limitation, and TIN:DRP ratios between 8 and 12 indicate either nutrient can be limiting.
Bradford Lake
The annual mean total phosphorus to total nitrogen (TN:TP) and the total inorganic nitrogen to dissolved reactive phosphorus (TIN:DRP) ratios for the lake are presented in Table 4.6. The mean TN:TP ratio was 4.8 and values ranged from 1.5 to 11.0. Conversely, the mean TIN:DRP ratio was 12.9 and values ranged from 3.7 to 32.0 (Table 4.6).
Table 4.6 Annual Mean Nitrogen to Phosphorus Ratios in Bradford Lake in 2002
Nitrogen to Phosphorus Ratios Station TN:TP TIN:DRP
WL1 4.8 12.9
The mean TN:TP and TIN:DRP ratios suggest that the lake was nitrogen and phosphorus limiting, respectively, during the 2002 study period. When there is a disagreement, lake managers often side with the mean TIN:DRP ratio, which generally classifies Bradford Lake as a phosphorus limiting system. Conversely, the individual TIN:DRP ratios, as reported for the six different study dates, indicate that the lake is occasionally phosphorus limiting and at other times, its nitrogen limiting.
Prepared by Aqua Link, Inc. 39 Little Neshaminy Creek & Bradford Lake Watershed Assessment
4.1.7. Plankton and Chlorophyll-a
The quantity of phytoplankton (free floating, microscopic aquatic plants commonly referred to as algae) and macrophytes (vascular aquatic plants) are primary biological indicators of lake trophic conditions. Small aquatic animals, namely zooplankton and macroinvertebrates, graze upon algae and fragments of aquatic plants. Larger invertebrates and fish then consume the above grazers and to a lesser extent, some aquatic plants.
Information about the plankton community composition and succession is extremely useful when attempting to gain a better understanding about various lake problems. For example, eutrophic lakes often support unbalanced phytoplankton communities characterized by very large numbers of relatively few species. The number of larger zooplankton will tend to decrease during periods when blue-green algae are dominant. Conversely, oligotrophic lakes and acidic lakes often have smaller populations of both phytoplankton and zooplankton, which typically consist of fewer species.
4.1.7.1. Phytoplankton
Phytoplankton are free floating, microscopic aquatic plants that have little or no resistance to currents and live suspended in open water. Their forms may be unicellular, colonial or filamentous. As photosynthetic organisms (primary producers), phytoplankton form the base of aquatic food chain and are grazed upon by zooplankton and herbivorous fish.
A healthy lake should support a diverse assemblage of phytoplankton, in which many algal species are represented. Excessive growth of a few species is usually undesirable. Such growth can result in dissolved oxygen depletion during the night, when the algae are respiring rather than photosynthesizing. Dissolved oxygen depletion also can occur shortly after a massive “algal bloom” due to increased levels of respiration by bacteria and other microorganisms that are metabolizing dead algal cells. Excessive growth of some species of algae, particularly members of the blue-green group, may cause taste and odor problems, release toxic substances to the water, or give the water an unattractive green soupy or scummy appearance.
Planktonic productivity is commonly expressed in terms of density and biomass. Phytoplankton densities are most frequently expressed as cells per milliliter (cells/ml). Biomass is commonly expressed on a mass per volume basis as micrograms per liter (µg/l). Of the two, biomass provides a better estimate of the actual standing crop of phytoplankton in lake systems.
Bradford Lake
The phytoplankton community in 2002 was represented by genera from six different taxa: Bacillariophyta (diatoms), Chlorophyta (green algae), Chrysophyta (golden-brown algae), Cryptophyta (cryptomonads), Cyanophyta (blue-green algae) and Euglenophyta (euglenoids). The
Prepared by Aqua Link, Inc. 40 Little Neshaminy Creek & Bradford Lake Watershed Assessment
phytoplankton biomasses in Bradford Lake ranged from 1,071 to 5,787 ug/l (micrograms per liter) as shown in Figure 4.3. The highest phytoplankton biomass values were reported in May and July 2002. In general, phytoplankton biomasses below 2,500 ug/l are considered low, ranging from 2,500 to 7,500 ug/l are moderately low to moderately high, ranging from 7,500 to 10,000 ug/l are high and above 10,000 are considered very high. Biomasses often exceeding 5,000 ug/l are considered often perceived by many as “algal bloom” conditions.
In April, the phytoplankton biomass was high and was largely dominated by diatoms (Bacillariophyta) as shown in Figure 4.3. The most prevalent diatoms were Navicula, Nitzschia and Surirella. Cryptomonads (Cryptophytes) and diatoms (Bacillariophytes) were most prevalent in May. Most of the May biomass consisted of Cryptomonas (Cryptophytes) and Cyclotella (Bacillariophyte). In June, Cryptomonads (Cryptophytes) along with green algae (Chlorophyta) were represented the bulk of the phytoplankton biomass. The most dominant green algae in June were comprised of Scenedesmus, Coelastrum and Oocystis. In July, the highest biomass levels were recorded and largely consisted of green algae (Chlorophyta) namely, Crucigenia and Scenedesmus. Green algae continued to be dominant in August and by September. The golden-brown algae (Chrysophytes), namely Mallomonas, was the most abundant in September (Figure 4.3).
In addition, the phytoplankton assemblage is also presented on a density basis in Figure 4.4. Similarly to biomass, the highest phytoplankton densities occurred in May and July 2002. In contrast, the phytoplankton density in May was dominated by blue-green algae (Cyanophytes), namely Oscillatoria. Phytoplankton density in July largely consisted of Crucigenia, which is a form of green algae (Chlorophyta).
4.1.7.2. Chlorophyll-a
Chlorophyll-a is a pigment that gives all plants their green color. The function of chlorophyll-a is to convert sunlight to chemical energy in the process known as photosynthesis. Because chlorophyll- a constitutes about 1 to 2 percent of the dry weight of planktonic algae, the amount of chlorophyll-a in a water sample is an indicator of phytoplankton biomass. According to Nurnberg (2001), a lake is generally classified oligotrophic, mesotrophic, eutrophic and hypereutrophic when chlorophyll-a concentrations are less than 3.5 ug/l, 3.5 to 9.0 ug/l, 9.1 to 25.0 ug/l and greater than 25.0 ug/l (micrograms per liter), respectively.
Bradford Lake
The 2002 annual mean chlorophyll-a concentration in Bradford Lake was 16.4 ug/l. Chlorophyll- a concentrations ranged from 9.8 to 22.0 ug/l during the study period. According to the Nurnberg criteria, the annual mean chlorophyll-a concentration indicates highly eutrophic conditions.
Prepared by Aqua Link, Inc. 41 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Phytoplankton Biomass in Bradford (Warrington) Lake
6,000
5,000
4,000
3,000
Biomass (ug/l) 2,000
1,000
0 4/30/02 5/30/02 6/26/02 7/31/02 8/22/02 9/26/02
BACILLARIOPHYTA CHLOROPHYTA CHRYSOPHYTA CRYPTOPHYTA CYANOPHYTA EUGLENOPHYTA PYRRHOPHYTA RHODOPHYTA
Figure 4.3 Phytoplankton Biomass in Bradford Lake in 2002
Phytoplankton Densities in Bradford (Warrington) Lake
14,000
12,000
10,000
8,000
6,000 Density (cells/ml) 4,000
2,000
0 4/30/2002 5/30/2002 6/26/2002 7/31/2002 8/22/2002 9/26/2002
BACILLARIOPHYTA CHLOROPHYTA CHRYSOPHYTA CRYPTOPHYTA CYANOPHYTA EUGLENOPHYTA PYRRHOPHYTA RHODOPHYTA Figure 4.4 Phytoplankton Densities in Bradford Lake in 2002
Prepared by Aqua Link, Inc. 42 Little Neshaminy Creek & Bradford Lake Watershed Assessment
4.1.8. Trophic State Index
The Trophic State Index (TSI) developed by Carlson (1977) is among the most commonly used indicators of lake trophic state. This index is actually composed of three separate indices based on measurements of total phosphorus concentrations, chlorophyll-a concentrations and Secchi disk depths for many lakes. Total phosphorus was chosen for the index because phosphorus is often the nutrient limiting for phytoplanktonic growth in lakes. Chlorophyll-a is a plant pigment present in all algae and is used to provide an indication of the biomass of phytoplankton and Secchi disk depth is a common measure of lake transparency.
As part of this study, TSI values were determined for total phosphorus, chlorophyll-a, and Secchi depth data for each of the study dates. Total phosphorus concentrations, chlorophyll-a concentrations, and Secchi disk depths were logarithmically converted to a trophic state scale ranging from 1 to 100. Increasing values for the Trophic State Index are indicative of increasing lake trophic states. In general, index values less 35 to 40 are indicative of oligotrophic conditions, while index values greater than 50 to 55 are indicative of eutrophic lake conditions. The Pennsylvania Department of Environmental Protection (PA DEP) classifies lakes according to the following: oligotrophic (less than 40), mesotrophic (40 to 50), eutrophic (50 to 65) and hyper- eutrophic (greater than 65) as noted in its 2002 PA Water Quality Assessment 305(b) Report.
Bradford Lake
The calculated 2002 mean TSI values for Secchi depth, chlorophyll-a and total phosphorus are presented in Table 4.7. In addition, the individual TSI values for all study dates and the mean TSI values for the 2002 study period are graphical presented in Figure 4.4.
Table 4.7 Mean Carlson’s TSI Values in Bradford Lake in 2002
Station Trophic State Index (TSI) Values
Secchi Depth Chl-a Total P
WL1 64 58 73
Note: TSI values based upon the mean values for each parameter during April – September 2002
Prepared by Aqua Link, Inc. 43 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Carlson's TSI Values for Bradford (Warrington) Lake
100
90 82.5 79.1 80 76.4 73.2 73.2 70.6 70.0 70.6 70 64.5 65.4 64.2 63.8 62.7 60.4 60.9 57.8 57.5 58.0 60 56.2 54.6 53.0 50
TSI Value 40
30
20
10
0 4/30/2002 5/30/2002 6/26/2002 7/31/2002 8/22/2002 9/26/2002 2002 Study Period* Study Date Secchi Depth Chl-a Total P * TSI values for 2002 Study Period based upon mean values for each parameter Figure 4.5 TSI Index Values in Bradford Lake in 2002
Overall, the lowest and highest mean TSI values were determined for chlorophyll-a and total phosphorus, respectively. This divergence between the mean values is likely due to the fact that nitrogen is sometimes the limiting nutrient and the lake has a very rapid flushing rate (refer to Sections 4.1.6.3 and 6.1.5, respectively). In any event, during the 2002 study period, the lake was classified as highly eutrophic based upon the mean TSI values for Secchi depth and chlorophyll-a. Conversely, the mean total phosphorus TSI value suggests that the lake is classified as hypereutrophic.
4.2. Aquatic Macrophytes
During the 2002 study period, Bradford Lake contained an over abundant quantity of aquatic macrophytes (higher aquatic vascular plants). By August and September, it was estimated that nearly 70 percent of the surface area of lake was choked with aquatic vegetation. By far, the most dominant aquatic plant in Bradford Lake was water chestnut. These dense beds of water chestnut were intertwined with dense mats of filamentous algae. Water chestnut nearly occupied all shallow water depths ranging from 0 to 4 feet (Figure 2.1), thereby severely restricting anglers from using this water resource during the summer recreational season.
Prepared by Aqua Link, Inc. 44 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Water chestnut (Trapa natans) is a highly aggressive plant that is spreading from New England north and south. This plant is not the same species of edible water chestnut used in Asian cooking. Originally from Eurasia, it was introduced and cultured in the US in the late 1870's and first invaded the Charles River in Massachusetts. It is now found in Quebec, Massachusetts, New York (a huge problem in Lake Champlain), Vermont, Maryland, as well as Pennsylvania. In Pennsylvania, it is not yet widespread across the state, but it has increased its presence in the last 2 years. It is presently recorded in 6 waterbodies in 4 counties in Pennsylvania: Bradford Reservoir (also known as Warrington Lake) in Bucks County; a pond in Lower Paxton Township, Dauphin County; Lake Maskenozha, Lehman Lake and Minks Pond in Pike County and a backwater area of the Delaware River near Milanville in Wayne County (PALMS 2004a).
Water Chestnut identified Spiny seed (nutlet) produced in Bradford Lake in 2002 by Water Chestnut
Water Chestnut has a rosette of floating leaves that encompass about 6 to 8 or more inches around. The underwater stem and roots can reach 16 ft in length. The plant is an annual and produces 15 to 20 seeds, which are fairly large (about an inch in diameter) and have 4 nasty points (spines) on the shell. They can inflict a nasty stab wound if stepped on. Seeds (but not plants) can survive the winter and germinate the next spring, and if conditions are not right for sprouting, they can remain viable for up to 12 years. One acre of these plants can produce enough seeds to cover 100 acres the following year (PALMS 2004a).
Water chestnut grows in calm, shallow, nutrient-rich freshwater areas with soft, muddy bottoms. Mats of these plants can severely limit boating, fishing and lake access. It has the potential to infest wetlands and critical habitats. Furthermore, this invasive exotic plant has little value as a food source and habitat for native wildlife. Mats shade out native plant species, reduce biodiversity, and can impact threatened and endangered species. Decomposition of dying plants in the fall causes low dissolved oxygen levels and can further stress the aquatic environment (PALMS 2004a).
The main methods used for control of this aquatic floater are hand pulling and mechanical harvesting. The herbicide 2,4-D is also successful for control. Biological control organisms are
Prepared by Aqua Link, Inc. 45 Little Neshaminy Creek & Bradford Lake Watershed Assessment
being researched by Cornell University. Control practices are required over a period of at least 5 years to be successful to deplete the seed bank in the sediment (PALMS 2004a).
4.3. Summary of Lake Assessment Data
Bradford Lake is classified as hypereutrophic in 2002. The mean Carlson TSI values for total phosphorus, chlorophyll-a and Secchi disk transparency were 73, 58 and 65, respectively. During the study period, the lake contained high concentrations of nutrients, which resulted in algal blooms (high levels of phytoplankton biomass). In turn, these algal blooms significantly decreased water clarity (Secchi disk transparency), thereby adversely impacting the overall aesthetics of the lake. In addition, the low dissolved oxygen levels allowed for the buildup of potentially toxic ammonia nitrogen and exacerbated the internal release of nutrients from in-lake sediments.
Water temperature data indicates that Bradford Lake is classified as a very shallow, polmictic impoundment (reservoir or lake). Polymictic lakes are those lakes that mix or destratify throughout the growing season (May through September). In this assessment, Bradford Lake was thermally stratified in May through July and destratified in August and September. Dissolved oxygen data for the study period indicate that the lake will result in stressful conditions and production impairment of both coldwater (i.e., trout) and warmwater (i.e., largemouth bass and bluegill) game fish species.
Dissolved oxygen concentrations were strongly stratified when the lake was thermally stratified during the months of May, June and July. In June and July, the dissolved oxygen levels typically fell below 1 mg/l near the lake bottom. Conversely, dissolved oxygen levels were very low and uniform throughout the water column in August and September. The dissolved oxygen concentrations were below 1 mg/L and 3 mg/L in August and September. These uniform, low dissolved oxygen concentrations may be related to low streamflow, thereby reducing the overall hydraulic residence time (flushing rate) of the reservoir. Under such conditions, it is plausible that upstream point sources (i.e., wastewater treatment facilities) may be exerting a high biological oxygen (BOD) demand on the lake.
Low dissolved oxygen levels at the lake water-sediment interface in June through August 2002 suggest that in-lake sediments may promote the internal release of nutrients from sediments. Low dissolved oxygen concentrations also are allowing for the buildup of hydrogen sulfide gas and the formation of toxic ammonium nitrogen. The release of soluble nutrients via sediments and the formation of hydrogen sulfide and ammonium nitrogen dramatically increase when dissolved oxygen levels in lake bottom waters are less than 1.0 mg/L.
Lastly, Bradford Lake contained an over abundant quantity of aquatic macrophytes (higher aquatic vascular plants) in 2002. By late summer, nearly 70 percent of the surface area of lake was choked with aquatic vegetation. By far, the most dominant aquatic plant in Bradford Lake was water
Prepared by Aqua Link, Inc. 46 Little Neshaminy Creek & Bradford Lake Watershed Assessment
chestnut. These dense beds of water chestnut were intertwined with dense mats of filamentous algae. Water chestnut nearly occupied all shallow water depths ranging from 0 to 4 feet, thereby severely restricting anglers from using this water resource during the summer recreational season.
Water chestnut (Trapa natans) is a highly aggressive plant that is spreading from New England north and south. Furthermore, this invasive exotic plant has little value as a food source and habitat for native wildlife. Mats shade out native plant species, reduce biodiversity, and can impact threatened and endangered species. Decomposition of dying plants in the fall causes low dissolved oxygen levels and can further stress the aquatic environment.
Prepared by Aqua Link, Inc. 47 Little Neshaminy Creek & Bradford Lake Watershed Assessment
5. Watershed Assessment Data and Results
The stream monitoring program and the watershed investigation for the Bradford Lake watershed assessment project are discussed below in Sections 5.1 and 5.2, respectively.
5.1. Streams Monitoring Program
The stream monitoring program for this project extended from March 2003 through May 2005. In Section 5.1.1, the study design and how stream data were acquired are briefly discussed. In addition, stream data and results are presented in Section 5.1.2. For additional information about the stream monitoring program, refer to the approved Quality Assurance – Quality Control Plan for the Warrington (Bradford) Lake and Little Neshaminy Creek Watershed Assessment Project dated April 28, 2002 (Aqua Link, Inc. 2002) and the Stream Monitoring Manual: the Little Neshaminy Creek and Warrington (Bradford) Lake Watershed Assessment Project (Aqua Link, Inc. 2003).
5.1.1. Study Design and Data Acquisition
In March 2003, Aqua Link and the Project Sponsor, the Bucks County Conservation District, established four stream stations throughout the Bradford Lake watershed (Figure 2.2). Written descriptions of these stations along with photographs are provided below in Table 5.1 and Figure 5.1, respectively. At these stations, staff gages were installed and cross sections were selected. These cross sections were used to collect and record incremental stream velocity and water depth data during the time of stream sample collection.
Table 5.1 Descriptions of Stream Monitoring Stations
Station Stream Description
LNC1 Little Neshaminy Creek Little Neshaminy Creek at Lower Nike Park. Little Neshaminy Creek upstream of Kenas Road bridge LNC2 Little Neshaminy Creek crossing. Station located at pedestrian bridge. Unnamed tributary to lake along northern shoreline. Within UNTA Unnamed Tributary walking distance of Station LNC1. Unnamed tributary to lake along southern shoreline. UNTB Unnamed Tributary Downstream of County Line Road.
Prepared by Aqua Link, Inc. 48 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 5.1 Photographs of the Stream Monitoring Stations
Prepared by Aqua Link, Inc. 49 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Aqua Link provided stream monitoring training to District personnel and several local volunteers. Thereafter, the trained individuals were responsible for implementing the stream monitoring program for this assessment project. Copies of the stream monitoring manual that was developed by Aqua Link were provided to the District and the volunteer monitors. This manual provided a comprehensive set of instructions ranging from collecting field data and water samples to shipping the samples to the contract laboratory for analysis.
The four stream stations were monitored four times during baseflow (low flow) and three times during stormflow (high flow) conditions from June 2003 through December 2004. During a sampling event, discrete water samples were collected and subsequently shipped to the contract laboratory for analysis. All collected stream samples were analyzed for total phosphorus, total Kjeldahl nitrogen, nitrate nitrogen, nitrite nitrogen and total suspended solids. At the time of sample collection, staff gage readings were recorded on designated field data sheets. Lastly, incremental stream water depths and velocities were measured and recorded at the established cross sections at all stream stations. All stream water quality and calculated discharge data are included in Appendices G and H of this report.
Aqua-Link and the District also collected macroinvertebrate (aquatic insects and other aquatic organisms) samples at the four different stream stations (Figure 2.1). A two-man crew collected the macoinvertebrate samples using a kick net. The samples were sorted in the field and preserved accordingly. Sampling was completed when more than 100 aquatic organisms were collected at a given stations. All sorted and preserved macroinvertebrate samples were shipped to Aquatic Resource Consulting of Stroudsburg, Pennsylvania for identification and enumeration.
Macroinvertebrate organisms were identified according to Peckarsky et al, 1990 using a Bausch and Lomb 0.7x-3x stereomicroscope. They were enumerated, and assigned a pollution tolerance value if known (Environmental Analysts 1990). Taxa richness, modified EPT index, percent modified mayflies, percent dominant taxon and Hilsenhoff biotic index values were calculated for each station to apply Pennsylvania Department of Environmental Protection (PA DEP) Central Office’s most recent guidance for use with special protection and antidegradation studies (PA DEP 1999). Shannon-Weiner diversity index was also calculated for all samples (Weber 1973).
Prepared by Aqua Link, Inc. 50 Little Neshaminy Creek & Bradford Lake Watershed Assessment
5.1.2. Stream Water Quality Data and Results
The mean concentrations of total phosphorus (TP), total nitrogen (TN, sum TKN and nitrate- nitrite nitrogen) and total suspended solids for all stream stations during both baseflow and stormflow conditions are summarized in Table 5.2. For ease of comparison, a numerical ranking system was applied for each water quality parameter. For example, mean total phosphorus concentrations during baseflow conditions were ranked from 1 to 5 (best to worst in terms of water quality). The same ranking system was applied to total nitrogen and total suspended solids. The assigned points were tallied and evaluated for all stream stations.
The water quality at the four stream stations was similar during baseflow conditions as shown in Table 5.2. The best and worst water quality was observed at Stations UNTB and LNC1, respectively (refer to Table 5.1 and Figure 2.2). Station LNC2 was very similar to the water quality at Station LNC1. It should be noted that the total phosphorus values were high at Station UNTB and very high at Stations LNC1 and LNC2. The total nitrogen concentrations were high at Stations UNTA and UNTB and, once again, very high at Stations LNC1 and LNC2. Very high nutrient concentrations in the Little Neshaminy Creek are likely due to point source loadings from wastewater treatment facilities. Conversely, the high nutrients in Unnamed Tributary B may be related to an upstream golf course.
Table 5.2 Mean Nutrient and Solids Concentrations for All Stream Stations Flow TP TN TSS Ranking Station Regime (mg/l as P) (mg/l as N) (mg/l) Total Pts TP TN TSS LNC1 Base 0.089 1.79 6.3 3 4 3 10 LNC2 Base 0.097 1.35 5.8 4 3 2 9 UNTA Base 0.032 0.81 11.0 1 2 4 7 UNTB Base 0.078 0.74 5.0 2 1 1 4
LNC1 Storm 0.453 2.13 226.0 4 4 4 12 LNC2 Storm 0.253 2.09 181.3 2 2 3 7 UNTA Storm 0.193 1.44 51.3 1 1 1 3 UNTB Storm 0.287 2.12 175.3 3 3 2 8
The nutrient (total phosphorus and total nitrogen) and suspended solids concentrations significantly increased during storm events at all four stations (Table 5.2). The greatest increases were observed at Station LNC1, which is the station closest to the lake. As shown in Table 5.2, the best and worst water quality during storms was observed at Stations UNTA and LNC2, respectively (refer to Table 5.1 and Figure 2.2).
Prepared by Aqua Link, Inc. 51 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Next, Aqua Link determined the instantaneous loadings of total phosphorus, total nitrogen and total suspended solids for all four streams stations as shown in Table 5.3. These loadings were determined by utilizing both water quality data reported by the contract laboratory and calculated instantaneous discharge data collected under baseflow and stormflow conditions. Aqua Link determined the instantaneous discharges using field data (incremental stream velocity and water depth data) that were measured and recorded by volunteer monitors during the time of stream sample collection (refer to Appendix G). The instantaneous loadings for total phosphorus, total nitrogen and total suspended solids were calculated for the individual study dates and subsequently averaged together in order to obtain mean loading values as presented in Table 5.3. These mean loading values reported in this table are expressed on a mass per day basis (kilograms per day, kg/d).
As expected, the nutrient and suspended solids loadings increased dramatically during stormflow conditions as shown in Table 5.3. This is attributed to increased streamflow volumes and concentrations during storm events. The highest nutrient and suspended solids loadings during both baseflow and stormflow conditions occurred at Station LNC1 followed by Station LNC2.
Table 5.3 Mean Nutrient and Solids Loadings for All Stream Stations Flow Mean Q TP TN TSS Ranking Station Regime (cfs) (kg/d as P) (kg/d as N) (kg/d) TP TN TSS Total Pts LNC1 Base 5.5 1.18 25.0 80 4 4 4 12 LNC2 Base 1.5 0.49 9.6 20 3 3 3 9 UNTA Base 0.3 0.03 0.9 5 1 2 2 5 UNTB Base 0.3 0.09 0.8 4 2 1 1 4
LNC1 Storm 203.2 332.53 1095.9 182,779 4 4 4 12 LNC2 Storm 91.9 84.26 545.0 70,412 3 3 3 9 UNTA Storm 31.9 19.59 133.3 6,131 2 2 2 6 UNTB Storm 5.8 5.29 31.3 3,512 1 1 1 3
5.1.3. Stream Macroinvertebrate Data
Aqua-Link collected macroinvertebrate samples at the four stream monitoring stations on May 18, 2005.The locations of the stream stations are shown in Figure 2.1. All preserved samples were sent to Aquatic Resource Consulting (ARC) of Stroudsburg, Pennsylvania for macroinvertebrate identification, enumeration and data analysis. The original report as prepared by ARC is presented in its entirety in Appendix I. For more information about sample collection and laboratory methods, refer to Section 3.2.2 and Appendix I.
Prepared by Aqua Link, Inc. 52 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 5.4 Macroinvertebrates Identified at all Stream Stations
TAXA STATIONS Biotic Index Value LNC1 LNC2 UNTA UNTB Ephemeroptera (mayflies) Stenacron interpunctatum - - 13 1 4 Caenis latipenis 3 - - - 6 Baetis flavistriga 20 6 9 1 4 Baetis Pluto - - 1 - 6 Trichoptera (caddisflies) Hydropsyche betteni - 2 - - 6 Cheumatopsyche sp. - 2 - - 6 Chimarra aterrima - 5 - - 4 Plecoptera (stoneflies) Perlesta placida - 19 - - 4 Amphinemura delosa - 1 - - 3 Coleoptera (beetles) Psephenus herricki 16 14 30 - 4 Stenelmis sp. - 17 - - 5 Berosus sp. 1 - - - 5 Odonata (dragon & damselflies) Argia sp. 1 3 1 - 6 Ophiogomphus sp. - 1 - - 6 Diptera (true flies) Simulium sp. 40 11 62 126 6 Chironomidae 20 9 - 3 6 Hemiptera (true bugs) Gerris sp. - - - 1 9 Isopoda (sowbugs) Caecidotea sp. 7 28 - 27 6 Amphipoda (freshwater shrimp) Gammarus sp. - 3 - - 4 Hirudinea (leeches) Myzobdella sp. - - - 1 8 Oligochaeta (aquatic earthworms) Lumbricina 2 1 - - 10 Turbellaria Macrostomum sp. 29 3 - 22 8 Bivalvia Pisidium sp. - - - 1 8
Prepared by Aqua Link, Inc. 53 Little Neshaminy Creek & Bradford Lake Watershed Assessment
The macroinvertebrate data for the four stations are listed in Table 5.4. This table also provides the biotic index (pollution tolerance) values for all identified taxa. The biotic index is a set of numerical values ranging from 0 (pollution intolerant) to 10 (pollution tolerant) and indicates an organism’s overall tolerance to water pollution.
ARC determined the following metrics for each of the samples collected at Stations CR1 through CR4: taxa richness, modified EPT index, percent modified mayflies, percent dominant taxon, and Hilsenhoff biotic index values were calculated for each station to apply PA Department of Environmental Protection (DEP) Central Office’s most recent guidance for use with special protection and antidegradation studies (PA DEP, 1999). In addition, the Shannon-Weiner diversity was also calculated for each sample (Weber, 1973). The above metrics are briefly described below and the calculated values are presented in Table 5.5:
1. Taxa Richness - is an index of diversity. The number of taxa (kinds) of invertebrates indicates the health of the benthic community. Generally, number of species increases with increased water quality. However, variability in natural habitat (stream order and size, substrate composition, current velocity) also affects this number.
2. Modified EPT Index - is a measure of community balance. The insect orders Ephemeroptera, Plecoptera, and Trichoptera (mayflies, stoneflies, and caddis flies), collectively referred to as EPT, are generally considered pollution sensitive. Thus, the total number of taxa within the EPT insect groups, minus those considered pollution tolerant (modified EPT index) is used to evaluate community balance. Healthy biotic conditions are reflected when these taxa are well represented in the benthic community.
3. Percent Dominant Taxon - measures evenness of community structure. It is the percent of the total abundance made up by the single most abundant taxon. Dominance of a few taxa may suggest environmental stress. However, the tolerance value of the dominant taxon must be considered.
4. Percent Modified Mayflies - is another measure of balance. Mayflies are considered one of the least tolerant orders to organic pollution and acidification. Undisturbed streams usually have an abundance of mayflies. Pennsylvania DEP uses the percent contribution of mayflies to the total number of organisms as an indication of water quality. The value is modified to exclude mayflies with a tolerance value greater than 5.
5. Modified Hilsenhoff Biotic Index - is a direct measure of pollution tolerance. Since many aquatic invertebrate taxa have been associated with specific values for tolerance to organic pollution, a biotic index is used to measure the degree of organic
Prepared by Aqua Link, Inc. 54 Little Neshaminy Creek & Bradford Lake Watershed Assessment
pollution in streams. The biotic index value is the mean tolerance value of all organisms in the sample. This metric has been modified to use more recent pollution tolerance values, which range from 0 to 10; the higher the value, the greater the level of pollution indicated.
Biotic Water quality Degree of Index Value Organic Pollution
0.00 – 3.50 Excellent None Apparent 3.51 – 4.50 Very Good Possible Slight 4.51 – 5.50 Good Some 5.51 – 6.50 Fair Fairly Significant 6.51 – 7.50 Fairly Poor Significant 7.51 – 8.50 Poor Very Significant 8.51 - 10.00 Very Poor Severe
6. Shannon-Weiner diversity measures the number of taxa present and evenness of distribution of organisms among the taxa (Weber, 1973). Diversity values in unpolluted waters generally range from 3 to 4. In severely polluted waters they are often less than 1.
Based upon the data presented in Tables 5.4 and 5.5 (ARC 2005), benthic macroinvertebrate samples from Little Neshaminy Creek and tributaries reflected impairment from organic pollution and/or habitat degradation. The benthic communities can be characterized as having had only moderate numbers of taxa with a predominance of pollution tolerant forms. The modified EPT index values ranged from 1 to 3 suggesting a lack of intolerant taxa (Table 5.5). Only a few organisms with a pollution tolerance value of less than 4 were collected from the four stations (Table 5.4). The modified Hilsenhoff biotic index values suggested “good” water quality at stations LNC2 and UNTA and fair water quality at stations LNC1 and UNTB (Tables 5.4 and 5.5).
Diversity values all fell below the range expected in unpolluted waters with the unnamed tributaries having poorer values than the Little Neshaminy Creek stations (Table 5.5). Benthic macroinvertebrate metrics suggest slightly more impairment at Station LNC1 on Little Neshaminy Creek than at Station LNC2. Station LNC2 had more taxa and modified EPT taxa than Station LNC1 and biotic index and diversity values superior to Station LNC1 (Table 5.5). However, Station LNC1 had a higher percentage of intolerant mayflies due to the greater number of Baetis flavistriga (Table 5.4). Differences between the unnamed tributary communities were subtle with the greatest contrast in the percent modified mayfly metric. Station UNTA had more Baetis and Stenacron mayflies
Prepared by Aqua Link, Inc. 55 Little Neshaminy Creek & Bradford Lake Watershed Assessment
while Station UNT B had only one of each (Table 5.4). Station UNTB also had slightly poorer biotic index, diversity and percent dominant taxa values than Station UNTA. Station UNT B, however, had the greater number of taxa (Table 5.5).
Table 5.5 Calculated Macroinvertebrate Metrics for all Stream Stations
Stations Metric LNC1 LNC2 UNTA UNTB Number of Organisms 139 125 116 183 Taxa Richness 10 16 6 9 Modified EPT Index 1 3 2 2 Percent Modified Mayflies 14.4 % 4.8 % 19.0 % 1.1% Percent Dominant Taxon 28.8 % 22.4 % 53.4% 68.8 % Hilsenhoff Biotic Index 5.95 5.13 5.19 6.26 Shannon-Weiner Diversity 2.68 3.36 1.75 1.45
5.1.4. Stream Data Summary
Overall, the streams contained high and very high nutrient (phosphorus and nitrogen) and suspended solids concentrations during baseflow (low flow) and stormflow (high flow) conditions, respectively. During baseflow conditions, the water quality at the four stream stations was somewhat similar. The best and worst water quality was observed at Stations UNTB and LNC1, respectively. It should be noted that the water quality at Stations LNC1 and LNC2 was nearly identical and are influenced by three upstream wastewater treatment facilities.
The nutrient and suspended solids concentrations significantly increased during storm events at all four streaming monitoring stations. The greatest increases were observed at Station LNC1, which is the station closest to the lake. The best and worst water quality during storms was observed at Stations UNTA and LNC1, respectively.
As expected, the nutrient and suspended solids loadings increased dramatically during stormflow conditions. This is attributed to increased streamflow volumes in conjunction with increased phosphorus, nitrogen and suspended solids concentrations during storm events. The highest nutrient and suspended solids loadings during both baseflow and stormflow conditions occurred at Station LNC1 followed by Station LNC2.
The benthic macroinvertebrate samples collected from Little Neshaminy Creek and tributaries reflected impairment from organic pollution and/or habitat degradation. The benthic communities can be characterized as having had only moderate numbers of taxa with a predominance of pollution
Prepared by Aqua Link, Inc. 56 Little Neshaminy Creek & Bradford Lake Watershed Assessment
tolerant forms. The modified Hilsenhoff biotic index values suggested “good” water quality at stations LNC2 and UNTA and fair water quality at stations LNC1 and UNTB.
5.2. Watershed Investigation
Aqua Link, Inc. toured the Bradford Lake watershed during the Spring 2005. The purpose of performing these tours was to gain first hand knowledge about the watershed and to identify major problem areas that may be contributing significant amounts of NPS (nonpoint source) pollution to the lake. Our investigation primarily focused on those NPS pollutants that are commonly responsible for accelerating the rate of lake eutrophication, namely nutrients (phosphorus and nitrogen) and sediments.
In the field, Aqua Link toured lake and stream riparian corridors via truck, therefore most of our field surveillance targeted those areas generally accessible by roads (paved or unimproved) and near bridge crossings. A GPS receiver (Garmin Model GPS 76S) linked to a portable notebook computer provided field personnel with real-time location and topographic data. Numerous photographs were taken to document the current land use characteristics of the major subwatersheds and any significant NPS watershed problems that were identified. The locations of all photographs are shown in Figure 5.2, while the actual photographs of the watershed are presented in Figure 5.3.
5.2.1. Description of the Bradford Lake Watershed
This section of the report provides a description of the entire Bradford Lake watershed and its major subwatersheds based upon field reconnaissance during our watershed investigation in the Spring 2005. The major subwatersheds of the Bradford Lake watershed are LNC (Little Neshaminy Creek), UNTA (Unnamed Tributary A), UNTB (Unnamed Tributary B) and the Direct Drainage Area. Refer to Section 2.2 for more information about the Bradford Lake watershed and its four major subwatersheds.
Overall, the Bradford Lake watershed largely consists of medium density residential lands with some commercial land uses that are intermixed with woodlots, fields (scrub/shrub) and agriculture. The majority of the residential homes are located within housing developments and agriculture is generally limited to crop production. There are no significant livestock operations occurring within the Bradford Lake watershed. Of the four major subwatersheds, most of the newer residential developments are located within the Little Neshaminy Creek (LNC) subwatershed. The Unnamed Tributary A (UNTA) subwatershed, which is highly developed, primarily consists of older residential homes interspersed with some newer developments. The Unnamed Tributary B (UNTB) subwatershed and the direct drainage area are considered more rural with respect to the other two major subwatersheds. In addition, the highest levels of active new home construction was observed in the lower section of the LNC subwatershed just west of Folly Road, the lower section of the UNTA subwatershed and the direct drainage area.
Prepared by Aqua Link, Inc. 57 Little Neshaminy Creek & Bradford Lake Watershed Assessment
By far, the highest densities of commercial land uses occur within the eastern and western sections of the Bradford Lake watershed. In the east, commercial lands generally occur in the UNTA subwatershed along the Route 611 corridor. Conversely, the majority of commercial lands in the western portion of the watershed lie within the Route 309, Upper State Road and Horsham Road (Route 463) corridors.
Direct Drainage Area
The direct drainage area includes Bradford Lake, its dam and all of the surrounding parkland, which is county-owned and leased to Warrington Township. Much of the lands within this subwatershed consist of fields and forested woodlots intermixed with some agriculture lands and rural residential homes. Most of the homes are located along County Line and Street Roads. At the time of our investigation, a large residential development, which overlooks the northern shoreline of the lake, was actively under construction.
Unnamed Tributary A
The Unnamed Tributary A (UNTA) subwatershed is highly developed. This subwatershed primarily consists of older residential homes interspersed with newer developments. Most of the undeveloped lands, namely grassy fields, agricultural lands and forested woodlots are located near the lake. A large number of homes are located around the Fairways Golf and Country Club. The unnamed tributary in this subwatershed flows directly through the golf course. Many of the streambanks at the golf course are severely eroding. Bank erosion is likely attributed to an inadequate riparian buffer along the stream and increased stormwater volumes as a result of increased levels of urbanization. Lastly, the eastern section of this subwatershed contains commercial lands within the Route 611 corridor. Some of the businesses in this section of the subwatershed are Stutz Candy and the Warrington Shopping Center. This shopping center is located at the intersection of Route 611 and Bristol Road.
Unnamed Tributary B
The Unnamed Tributary B (UNTB) subwatershed is far less developed than the UNTA subwatershed. It primarily consists of some rural residential homes intermixed with old fields, agricultural lands and forested woodlots. This subwatershed also contains an 18-hole golf course, Limekiln Golf Course, which is visible from Park Road and Limekiln Pike (Route 152). The headwaters of Unnamed Tributary B are located at the golf course. Based upon our watershed tour and a review of aerial maps (Section 2.2), it appears that most of the stream corridor for this unnamed tributary is forested.
Little Neshaminy Creek Subwatershed
Prepared by Aqua Link, Inc. 58 Little Neshaminy Creek & Bradford Lake Watershed Assessment
The Little Neshaminy Creek (LNC) subwatershed is the largest of the four subwatersheds. Land uses in the subwatershed range from highly rural to highly commercial. This subwatershed contains three wastewater treatments plants. Refer to Section 6.2.1 for a thorough discussion of these wastewater treatment facilities and their potential impact on Bradford Lake.
The most rural areas are located in the lower section of the subwatershed in the vicinity of Folly Road and Chestnut Lane. These two roadways are located in between Lower State Road and Bradford Lake. Several large parks (Lower Nike Park, Memorial Field, also known as Upper Nike Park, and Twin Oaks Park) and Illg’s Meats are located off of Folly Road, which in turn give this portion of the subwatershed a rural appearance.
During the watershed tour, two active construction sites for residential housing were observed near the intersection of Chestnut Lane and County Line Road. Both of the sites are located near the intersection of Folly and County Line Roads and are in close proximity to the Little Neshaminy Creek.
The overall degree of urbanization dramatically increases westward from Lower State Road to Upper State Road. The highest concentration of commercial lands is located in the most western portion of this subwatershed along the Route 309, Upper State Road and Horsham Road (Route 463) corridors. This area includes a portion of the Montgomeryville Mall, the Costco shopping center and the shopping centers containing Best Buy, Target and the Giant supermarket.
5.2.2. Major Nonpoint Sources of Pollution
The most apparent NPS problem identified during the watershed investigation was the severe streambank erosion occurring along the unnamed tributary in the UNTA subwatershed. This streambank erosion was observed at the Fairways Golf and Country Club. Bank erosion is likely attributed to an inadequate riparian buffer along the stream and increased stormwater volumes as a result of increased levels of urbanization. The remainder of Unnamed Tributary A, the Little Neshaminy Creek and Unnamed Tributary B were otherwise considered fairly stable at all major bridge crossings throughout the watershed.
The watershed investigation revealed that the most serious threat to lake water quality is land development (active and post construction). This includes active construction sites and those lands previously developed for both residential housing developments and commercial shopping centers. All observed active construction sites were for single-dwelling, residential housing and were located in the Unnamed Tributary A and the lower section of the Little Neshaminy Creek subwatersheds.
Prepared by Aqua Link, Inc. 59 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 5.2 Location of Photographs in the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 60 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Figure 5.3 Photographs of the Bradford Lake Watershed
Prepared by Aqua Link, Inc. 61 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Prepared by Aqua Link, Inc. 62 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Prepared by Aqua Link, Inc. 63 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Prepared by Aqua Link, Inc. 64 Little Neshaminy Creek & Bradford Lake Watershed Assessment
As noted by Schueler (1987), pollutant (nutrient and sediment) export during the construction phase can be significant. Pollutant export increases dramatically both during and shortly after construction. Initial clearing and grading operations during construction expose much of the surface soils. Unless adequate erosion controls are installed and maintained at the site, enormous quantities of sediment along with attached nutrients and organic matter are delivered to streams.
Many of the existing residential developments along with commercial areas (e.g., shopping centers) of the watershed appear to contain stormwater controls that address stormwater volume as opposed to water quality. In urban areas, pervious, vegetated land is converted to impervious, unvegetated land. Impervious areas such as rooftops, roads, parking lots, and sidewalks may cover 35 percent or less of the land area in lightly urbanized areas to nearly 100 percent of the land area in heavily urbanized areas. Imperviousness results in increased stormwater runoff volumes and altered hydrology. Urban stormwater runoff carries increased pollutant loadings to surface waters, typically without treatment.
In addition to increased stormwater volumes, stormwater runoff is delivered to surface waters from impervious areas much more quickly than from vegetated areas, which can result in scouring of streambeds and increased sediment loadings to surface waters. When combined with the increased runoff velocities during spring snowmelts and rain-on-snow events, floods can occur more frequently and with greater severity in urbanized areas. The high velocity of stormwater flow in urban areas allows little infiltration and groundwater recharge (U.S. EPA 1997).
Prepared by Aqua Link, Inc. 65 Little Neshaminy Creek & Bradford Lake Watershed Assessment
6. Hydrologic and Pollutant Budgets
Hydrologic and pollutant budgets were determined for the Bradford Lake watershed. Hydrologic information was used to determine the hydraulic residence time (HRT) of the study lake. HRT is an important variable that is used in phosphorus modeling and when evaluating various in-lake restoration techniques. The pollutant budgets were determined for nutrients and sediment, which are the focus of this study with respect to lake eutrophication. In addition, the pollutant budget data were used in the lake phosphorus modeling exercises.
6.1. Hydrologic Budget
A hydrologic budget balances the amount of water to and from a lake system. Water inputs to a lake are from tributaries, direct runoff from lands immediately surrounding the lake (i.e., the direct drainage area), precipitation to the surface of the lake and groundwater. Water outputs are via the lake's outlet, evaporation from the surface of the lake and groundwater. The hydrologic budget for any lake system is generally presented as an input-output type equation as listed below:
1. V outlet = V tributaries + V direct drainage + V precipitation – V evaporation ± V groundwater ± V storage
Where,
V outlet volume of water released from the lake at the outlet,
V tributaries volume of water entering the lake via major tributaries,
V direct drainage volume of water entering the lake from lands adjacent to the lake and unmonitored tributaries to the lake,
V precipitation volume of precipitation to the surface of the lake,
V evaporation volume of water evaporated from the surface of the lake,
V groundwater net volume exchange of groundwater through the lake bottom, and
V storage change in storage capacity of the lake.
In order to simplify this equation, the following assumptions were made for this report. Shallow groundwater to the lake is assumed to be included as part of the estimates for V tributaries and V direct drainage. The V groundwater variable is assumed to be negligible since the lakes have very large watersheds and subsequently most of the water to the lakes will be from inflowing tributaries. The V
Prepared by Aqua Link, Inc. 66 Little Neshaminy Creek & Bradford Lake Watershed Assessment
storage variable is assumed to be negligible since the study period extends for a one-year period. Based on these assumptions, Equation No. 1 is simplified to the following equation:
2. V outlet = V tributaries + V direct drainage + V precipitation – V evaporation
In the following paragraphs, each of these four variables in Equation No. 2 was determined. In addition, hydrologic budget summary for the lake was prepared and are discussed in the following sections.
6.1.1. Major Tributaries
The annual contribution of water from the Little Neshaminy Creek (LNC) and Unnamed Tributaries A and B (UNTA and UNTB) were estimated using historical stream discharge data as reported by the United States Geological Survey for a nearby stream monitoring station. For this assessment, USGS 01464907 for the Little Neshaminy Creek at Valley Road near Neshaminy was selected to estimate stream flow contributions via these three tributaries. Historical discharge data at this station were obtained via the Internet using the USGS NWIS-W Data Retrieval System. The annual mean discharge at this station was determined to be 47.2 cfs (cubic feet per second). The calculated mean discharge was next expressed on a cfsm (cubic feet per second per square mile) basis by dividing the above value by its total drainage area, which is 26.8 square miles. A summary of the above information is presented in Table 6.1.
Table 6.1 Hydrologic Characteristics of the Little Neshaminy Creek near Neshaminy
USGS Period of Mean Discharge Drainage Area Mean cfsm Ratio Station No. Record (cfs) (sq. mile)
01464907 1998-2004 47.2 26.81 1.76
Source: USGS. Water resources data obtained via internet @ http://waterdata.usgs.gov.nwis.
Using the cfsm value shown in Table 6.1, the mean discharge for the major tributaries to the lake were estimated. The annual mean discharge value was also expressed on an annual volume basis in billion gallons per year (Bgal/yr) as shown in Table 6.2 (refer to Appendix J).
Prepared by Aqua Link, Inc. 67 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 6.2 Hydrologic Characteristics of Major Tributaries to Bradford Lake
Tributary Basin Area* Annual Mean Annual (sq. miles) Discharge Volume (cfs) (Bgal/yr)
Little Neshaminy Creek 8.5 15.00 2.54 (LNC Subwatershed)
Unnamed Tributary A 1.3 2.34 0.55 (UNTA Subwatershed)
Unnamed Tributary B 0.7 1.29 0.30 (UNTB Subwatershed)
6.1.2. Direct Drainage
Similar to Section 6.1.1, the annual volume of water contributed by the direct drainage basin to the lake was estimated using the cfsm approach. The direct drainage basin (excluding Bradford Lake) is 0.4 square miles as shown in Figure 2.2. Based upon the above, the estimated annual water volume contributed by the direct drainage area is 0.17 billion gallons per year (Bgal/yr). For additional information, refer to Appendix J. As previously discussed Section 6.1, water contributions from the direct drainage area occur via streamflow by minor tributaries to the lake, overland flow and shallow groundwater.
6.1.3. Precipitation and Evaporation
The amount of precipitation and evaporation directly to and from the lake was estimated by using historical climatological data reported by the Pennsylvania State Climatologist (www.ems.psu.edu/pa_climatologist). The mean annual precipitation occurring for the City of Philadelphia is 41.41 inches per year. Evaporation from the lake was estimated using a mean annual open pan evaporation rate of 31.72 inches per year as reported for Landisville, PA. The data reported for Landisville represents the evaporation rates for the southeastern portion of the state. Based upon its surface area, Bradford Lake receives approximately 0.025 billion gallons of water due to precipitation and loses 0.019 billion gallons of water as a result of evaporation annually.
Prepared by Aqua Link, Inc. 68 Little Neshaminy Creek & Bradford Lake Watershed Assessment
6.1.4. Hydrologic Budget Summaries
The normalized hydrologic budget for Bradford Lake is presented below in Table 6.3. For more information, refer to Appendix J of this report.
The most significant source of water to the Bradford Lake is the Little Neshaminy Creek. This stream annually contributes 77.0 percent of all incoming water to the lake as shown in Table 6.3. Conversely, the direct drainage area contributes only 3.8 percent of the annual total water input to the lake.
Table 6.3 Hydrologic Budget for Bradford Lake
Annual Volume Input/Output Percent of Cubic Feet Billion Gallons Total Input 3 (ft ) (Bgal) Little Neshaminy Creek 472,914,104 3.54 77.0 Unnamed Tributary A 73,860,107 0.55 12.0 Unnamed Tributary B 40,639,134 0.30 6.6 Direct Drainage 23,077,256 0.17 3.8 Precipitation to Lake 3,337,066 0.02 0.5 Evaporation from Lake -2,556,188 -0.02 ---- Total 611,271,480 4.57 100.0
6.1.5. Lake Hydraulic Residence Time
The hydraulic residence time of Bradford Lake was estimated using lake water volume data presented in Section 2.1.1 and hydrologic data presented in Section 6.1.4. Based upon this information, the mean hydraulic residences time for the lake was estimated to be 1.4 days or 0.004 years. Therefore, the lake, if completely drained, would require this many days on average to refill with water.
The hydraulic residence time is considered extremely short. Bradford Lake has a total drainage area of 11.0 square miles (approximately 7,062 acres) and lake surface area of 22 acres. Therefore, the drainage area to lake surface area ratio for this lake is 321. Overall, ratios less than 25 are considered low, while ratios greater than 150 are classified as high. In general, lakes with the
Prepared by Aqua Link, Inc. 69 Little Neshaminy Creek & Bradford Lake Watershed Assessment
extremely low hydraulic residence times (i.e., extremely high drainage area to surface area ratios) function like “run-of-the-river” type lake systems. The water quality of these types of lake can rapidly degraded as a result of high pollutant loadings from their surrounding watersheds. Conversely, lakes with the extremely high hydraulic residence times (i.e., extremely low drainage area to surface area ratios) serve as efficient sinks for both incoming nutrients and sediment. The water quality of these types of lakes tends to degrade more slowly in response to high pollutant loadings from the surrounding watersheds.
6.2. Pollutant Budgets
Pollutant budgets for phosphorus, nitrogen and suspended solids (sediments) were determined for the Bradford Lake watershed. In general, sources of nutrients and sediments to lakes are either from point or nonpoint sources. Point sources of pollution are direct (piped) discharges to streams and lakes from industrial and wastewater treatment facilities. All point source discharges require a NPDES (National Pollution Discharge Elimination System) permit, which is issued by the appropriate state agency. These permits thereby allow approved facilities to discharge treated process waters to nearby surface waters. Conversely, nonpoint sources (NPS) of pollution to lakes generally consist of runoff from different types of land uses, septic systems, waterfowl, atmospheric deposition and the internal loading via in-lake sediments. NPS pollutant loadings are often estimated by using the unit areal loading (UAL) approach. For this approach, export coefficients from the literature are used to estimate pollutant loadings from various watershed sources. The UAL approach has been widely accepted to estimate both nutrient and sediment loadings to lakes where either no or limited stream monitoring data have been collected.
6.2.1. Point Sources
Based upon a recent TMDL assessment of the Neshaminy Creek (PA DEP 2003), three point source discharges are located within the Bradford Lake watershed (Table 6.4). All of these facilities discharge treated effluent into the Little Neshaminy Creek. It should be noted that none of the point source discharges are classified as major facilities. The U.S. EPA defines a major facility as having a permitted daily discharge greater than 1million gallons per day (MGD).
The annual phosphorus and nitrogen loadings for the three point sources are presented in Table 6.5. The nutrient loadings were obtained directly from the TMDL Assessment Report of the Neshaminy Creek as prepared by PA DEP (PA DEP 2003). In this report, the annual phosphorus and nitrogen loadings in 1999 were determined using flow and water quality data as reported by the approved dischargers in their submitted Discharge Monitoring Reports (DMR’s) to PA DEP. The most significant point source discharge within the Bradford Lake watershed is the Eureka WWTP, which is located about 1.5 miles upstream of the lake.
Prepared by Aqua Link, Inc. 70 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 6.4 Point Source Discharges in the Bradford Lake Watershed
Name Owner NPDES Discharge Receiving Basin No. (MGD) Water Montgomery Township Eureka WWTP PA0053180 0.75 LNC LNC Municipal Authority Orchard Montgomery Sewer PA0052094 0.15 LNC LNC Development STP Company North Penn North Penn PA0050881 0.006 LNC LNC School District School District
Table 6.5 Nutrient Loadings by Point Source Discharges
NPDES TP TN Name No. (kg/yr) (kg/yr)
Eureka WWTP PA0053180 290.8 1,780.5
Orchard Development STP PA0052094 122.6 246.2
North Penn School District PA0050881 1.2 4.6
Total 414.6 2,031.3
6.2.2. Land Uses
Pollutant export coefficients reported by Reckhow et al. (1980) and the U.S. Environmental Protection Agency (1980) were evaluated and the most applicable export coefficients were selected to estimate the annual loading of phosphorus, nitrogen, and suspended solids to the study lake. The following watershed characteristics were used in selecting the most applicable export coefficients: geography, topography, soil characteristics and precipitation characteristics (frequency, duration, intensity, and quantity).
The selected export coefficients for total phosphorus, total nitrogen, and total suspended solids and the land use data, as presented in Section 2.2.4, were used to determine pollutant loadings for the
Prepared by Aqua Link, Inc. 71 Little Neshaminy Creek & Bradford Lake Watershed Assessment major subwatersheds. As noted in Section 2.2, the major subwatersheds in the Bradford Lake watershed are the Little Neshaminy Creek (LNC), Unnamed Tributary A (UNTA), Unnamed Tributary B (UNTB) and the direct drainage area (Figure 2.2). The direct drainage area consists of minor tributaries and adjacent lands that discharge directly into the lake. The total phosphorus, total nitrogen and total suspended solids loadings for the major subwatersheds are presented in Table 6.4. For a complete listing of all land use export coefficients and calculations, refer to Appendix K of this report.
The most significant source of nutrients and sediment (suspended solids) to Bradford Lake is the Little Neshaminy Creek (LNC) subwatershed (Figure 2.2). The least significant source of nonpoint source pollution to the lake is from the direct drainage subwatershed. Overall, the estimated nutrient and suspended solids loadings in Table 6.4 agree well with the determined loadings in Section 5.1.2. In Section 5.1.2, nutrient and suspended solids loadings were determined from stream water quality and hydrologic data that were collected as part of this study. Good agreement between the two different methods corroborates the accuracy of the selected export coefficients for various land uses.
Table 6.6 Nutrient and Solids Loadings for Major Subwatersheds
Total Load (kg/yr) Subwatershed Area (ha) TP TN TSS Little Neshaminy Creek (SW LNC) 2,207 1,409 10,560 1,179,044 Unnamed Tributary A (SW UNTA) 345 230 1,630 184,680 Unnamed Tributary B (SW UNTB) 190 76 843 55,034 Direct Drainage (SW Direct Drainage) 117 42 446 24,075 Totals 2,858 1,758 13,479 1,442,834
6.2.3. Atmospheric Inputs
The phosphorus and nitrogen loadings from the atmosphere to the study lake were estimated using the selected export coefficients of 0.25 kilograms per hectare per year (kg/ha/yr) for phosphorus and 10.0 kg/ha/yr for nitrogen (U.S. EPA 1980). These export coefficients account for nutrient loadings for both wet (precipitation) and dry fallout. Based on the above export coefficients and the lake surface area, Bradford Lake receives 2 and 101 kilograms per year of phosphorus and nitrogen, respectively.
6.2.4. On-Lot Septic Systems
Prepared by Aqua Link, Inc. 72 Little Neshaminy Creek & Bradford Lake Watershed Assessment
On-lot septic tanks can be a significant source of nutrients to lakes. In general, on-lot septic systems are assumed to impact lakes if these systems are within 100 meters (328 feet) of their shorelines. Nutrient inputs to lakes are often estimated by using appropriate export and soil retention coefficients.
No homes are located within 100 meters of the Bradford Lake therefore on-lot septic systems do not directly influence the lake.
6.2.5. Waterfowl
Large quantities of waterfowl on a lake can become problematic. Excessive amounts of droppings near the lake may become a nuisance and adversely affect the lake’s aesthetics. Furthermore, droppings that are washed into the lake can also adversely affect lake water quality. Waterfowl droppings, which are high in nutrients and fecal coliform bacteria, may accelerate the process of lake eutrophication and can result in unhealthy lake conditions for contact recreational activities such as swimming.
Phosphorus and nitrogen loadings for waterfowl were estimated by using loading coefficients cited by Bland (1996). These values are 0.44 and 1.43 grams per waterfowl-use day for phosphorus and nitrogen, respectively. In order to provide loading estimates for waterfowl, it was assumed that 25 geese reside at the lake the entire year and an additional 200 geese use the lake for a 3-month period during migration seasons. Based upon the above, phosphorus and nitrogen loadings that are contributed by waterfowl are estimated at 12 and 39 kg/year (kilograms per year).
6.2.6. Internal Release via In-Lake Sediments
In-lake sediments release nutrients, namely dissolved reactive phosphorus and ammonia nitrogen, to the overlying lake waters. The internal release of these nutrients dramatically increases when dissolved oxygen concentrations fall below 1 mg/l near the sediments. Under such conditions, phosphorus and nitrogen are released and then consequently become available for increased production of aquatic plants (i.e., phytoplankton, filamentous algae and macrophytes).
As discussed in Section 4.1, Bradford Lake is a shallow impoundment that was moderately thermally stratified in May through July in 2002. Conversely, the dissolved oxygen levels for the bottom waters (the hypolimnion) of the lake fell below 1 mg/l in June through August in 2002. Phosphorus concentrations (total and dissolved reactive phosphorus) in the surface and bottom waters were similar suggesting that any internally released phosphorus from in-lake sediments diffused quickly into the overlying surface waters. The above water quality data were carefully evaluated when selecting appropriate export coefficients for internal loadings for Bradford Lake.
The internal release of phosphorus via aerobic and anaerobic (anoxic) lake sediments was estimated by using export coefficients cited in the literature. The selected export coefficients for the
Prepared by Aqua Link, Inc. 73 Little Neshaminy Creek & Bradford Lake Watershed Assessment internal release of phosphorus from in-lake sediments were 5 and 20 mg/m2/day for aerobic and anaerobic conditions, respectively. The selected export coefficients for the internal release of nitrogen were 22 and 32 mg/m2/day for aerobic and anaerobic conditions, respectively (Thomann and Mueller 1987). It was assumed that the bottom waters of the lake were anoxic for 90 days and remained aerobic for 275 days. Based upon the above, the estimated phosphorus and nitrogen loadings from in-lake sediments were 285 and 802 kg/yr for Bradford Lake.
6.2.7. Pollutant Budget Summaries
The annual pollutant budget summaries for the Bradford Lake watershed are presented in Table 6.6. These budgets were estimated based upon the calculations presented in Sections 6.2.1 through 6.2.6.
The most significant source of nutrients and sediments to Bradford Lake is the Little Neshaminy Creek as shown in Table 6.5. This stream and its surrounding subwatershed contribute 74, 76 and 82 percent of the phosphorus, nitrogen and suspended solids to the lake (refer to Appendix K). A significant portion of the nutrient loadings to the Little Neshaminy Creek are attributed to three, upstream wastewater treatment facilities. These three facilities, as discussed in Section 6.2.1, represent about 23 and 14 percent of the phosphorus and nitrogen loadings to the Little Neshaminy Creek. Other significant sources of nutrients to the lake are Unnamed Tributary A and internal loading via in-lake sediments.
Table 6.7 Pollutant Budget for Bradford Lake
Pollutant (kg/yr) Source TP TN TSS
Little Neshaminy Creek (SW LNC) 1,824 12,591 1,179,044 Unnamed Tributary A (SW UNTA) 223 1,630 184,680 Unnamed Tributary B (SW UNTB) 76 843 55,034 Direct Drainage (SW Direct Drainage) 42 446 24,075 Atmospheric 2 101 ------Waterfowl 12 39 ------Internal Release by Sediments 285 802 ------Total 2,464 16,451 1,442,834 External Load Only (TP Model) 2,179
6.3. Phosphorus Modeling
Prepared by Aqua Link, Inc. 74 Little Neshaminy Creek & Bradford Lake Watershed Assessment
The water quality data collected during this study (Section 4.1) indicates that phosphorus is generally the "limiting" nutrient in Bradford Lake. As noted in Section 4.1.6.3, Bradford Lake sometimes contained extremely very high phosphorus concentrations, therefore it is likely that the lake occasionally became nitrogen limiting in 2002. When phosphorus is limiting, it is assumed that phosphorus generally controls the overall degree or level of eutrophication in the lake. Hence, if phosphorus concentrations were to decrease, the overall water quality of the lake is expected to improve.
Simply stated, the amount of phosphorus in the lake is a function of the amount of phosphorus flowing into the lake minus the amount of phosphorus flowing out of the lake minus the amount of phosphorus settling to the bottom of the lake. This simple input-output principle has been used to develop a large number of models to predict the lake phosphorus concentration if the input (load) and the basin's hydrology are determined. The major difference between various models is in their method of calculating their sedimentation term. Since it is not practical to measure phosphorus sedimentation directly, it must be estimated empirically based on a lake's morphometric and hydrologic characteristics.
These models are most commonly used as a tool to predict changes in lake water quality. Lake managers commonly increase and decrease the external phosphorus loads (lake phosphorus inputs) in order to predict changes in lake water quality. In addition, lake managers frequently rely on models to corroborate the overall accuracy of selected export coefficients for various point and nonpoint sources.
Study Period
Lake and watershed data that were acquired as part of this assessment served as input variables for phosphorus modeling. First, phosphorus modeling was performed to predict the phosphorus concentrations in Bradford Lake. Next, predicted concentrations were compared to the actual mean in-lake concentration for the study period. Lastly, the selected model was rearranged in order to determine the necessary phosphorus loading reductions that would be required to achieve an in-lake phosphorus concentration of 0.048 mg/l as P. This phosphorus concentration corresponds to a Carlson TSI value of 60.0, which would then reclassify the lake as highly eutrophic. In 2002, the annual mean total phosphorus concentration was 0.120 mg/l as P. This extremely high phosphorus concentration corresponds to a Carlson TSI value of 73 and thereby indicates hypereutrophic lake conditions.
Numerous phosphorus models were evaluated for their applicability to the study lakes. The most critical stage in performing any modeling exercise is to select the most appropriate model. Models developed by Vollenweider (1969), Kirchner and Dillon (1975), Chapra (1975), Larsen and Mercier (1975), Jones and Bauchman (1975), Canfield and Bauchman (1981), Prairie (1988), Prairie (1989), Reckhow (1977) and Walker (1977) were evaluated as part of this assessment.
Prepared by Aqua Link, Inc. 75 Little Neshaminy Creek & Bradford Lake Watershed Assessment
After reviewing over fifteen different models, the Reckhow Quasi-General Model (1980) was selected as a suitable model for the study lake. This Reckhow Quasi-General model, which tends to be a rather robust model, is as follows:
TP = L/[11.6 + 1.2Qs]
Where,
TP = annual average phosphorus concentration (g/m3 or mg/l) L = areal phosphorus loading (g/m2-yr) Qs = areal water loading (m/yr) = Q/Ao Q = inflow of water to the lake (m3/yr) 2 Ao = lake surface area (m )
L was obtained from the phosphorus budgets that were developed and summarized in Tables 6.5. Q was obtained from the hydrologic budget that was developed and summarized in Tables 6.3 and the lake surface area was determined and presented in Table 2.1. For all modeling results, refer to Appendix K.
By substituting the appropriate values, the Reckhow model predicts in-lake concentration of 0.100 mg/l as phosphorus (P) for Bradford Lake. The actual mean phosphorus concentration in the lake for the study period was 0.120 mg/l as P. The actual mean concentration for Bradford Lake represents the mean concentration for surface (epilimnion) and bottom (hypolimnion) waters.
Based upon the above, the predicted and actual concentrations for Bradford Lake are in good agreement with one another. Therefore, the closeness of these values corroborates the accuracy of the selected export coefficients for determining the phosphorus budget for the lake.
The phosphorus loading reductions were determined in order to achieve an in-lake phosphorus concentration of 0.048 mg/l as P in the study lake. This phosphorus concentration corresponds to a Carlson TSI value of 60, which indicates moderate eutrophic lake conditions. The above equation was rearranged to solve for L when P was set equal to 0.048 mg/l as P. Based upon the above, it was estimated that calculated phosphorus loading to Bradford Lake would have to be reduced by 52 percent in order to achieve the targeted in-lake phosphorus concentration. As noted previously, the calculated external phosphorus loadings to Bradford Lake was 2,179 kg/yr. It should be noted that the external phosphorus loadings do not include any internal loadings from in-lake sediments.
Prepared by Aqua Link, Inc. 76 Little Neshaminy Creek & Bradford Lake Watershed Assessment
7. Evaluation of Restoration Alternatives & Practices
The primary goal of any lake and watershed management plan is to improve or protect the overall quality of incoming waters to a lake and to improve both the water quality and aquatic habitats of the lake itself. Management plans are typically developed by carefully evaluating all potential in-lake restoration alternatives, watershed management best management practices and institutional (non-structural) practices to achieve this goal.
Below is a list of restoration practices that are commonly evaluated when developing a comprehensive lake and watershed management plan:
In-lake Management Practices
1. Lake Aeration a. Aeration (destratification, hypolimnetic) b. Mechanical Circulation 2. Lake Deepening a. Sediment Dredging b. Water Level Drawdown for Sediment Consolidation c. Raise Lake Surface Elevation 3. Other Physical Controls a. Harvesting of Nuisance Aquatic Plant Biomass b. Water Level Fluctuation c. Habitat Manipulation (Improvements) d. Covering Bottom Sediments to Control Macrophytes 4. Chemical Controls a. Algicides b. Herbicides 5. Biological Controls a. Bio-Manipulation for Phytoplankton Control b. Insects for Nuisance Aquatic Vegetation 6. In-Lake Schemes to Accelerate Nutrient Outflow or Prevent Recycling a. Sediment Dredging for Nutrient Control b. Nutrient Inactivation/Precipitation c. Dilution and Flushing
Prepared by Aqua Link, Inc. 77 Little Neshaminy Creek & Bradford Lake Watershed Assessment
d. Biotic Harvesting for Nutrient Removal e. Selective Discharge from Impoundments f. Sediment Exposure and Desiccation g. Lake Bottom Sealing 7. In-Lake Deacidification a. Limestone Additions b. Base Material Injection into Sediments
Watershed Management Practices
1. Wastewater a. Upgrade Facilities to Improve Effluent Quality b. Diversion of Wastewater from Lakes or Watersheds c. Connecting On-Lot Septic Systems to Public Sewers 2. Land Management Practices a. Agriculture (Crop and Feedlot) b. Forest (Silviculture) c. Urban (Stormwater) d. Riparian Corridors 3. Stream and Lake Bank Stabilization & Restoration a. Soft Approach (Plant Materials Only) b. Soil Bio-Engineering Approach c. Natural Stream Channel Design (Streams Only) d. Hard Approach (Conventional Armoring) 4. Homeowner Management Practices a. Lawn Maintenance b. On-Lot Septic System Maintenance 5. Deacidification a. Watershed Liming b. Limestone Additions to Streams
Prepared by Aqua Link, Inc. 78 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Institutional Practices
1. Model Ordinances a. Stormwater Management b. Riparian and Sensitive Area Protection 2. Education a. Lake Ecology and Management b. Watershed Dynamics and Management c. Homeowner Best Management Practices 3. Establishing a Lake and Watershed Steering Committee 4. Water Quality Monitoring a. Lakes b. Streams
The following criteria should be considered when evaluating potential restoration practices (U.S. EPA 1980):
Effectiveness how well a specific management practice meets its goal
Longevity reflects the duration of treatment effectiveness
Confidence refers to the number and quality of reports and studies supporting the effectiveness rating given to a specific treatment
Applicability refers to whether or not the treatment directly affects the cause of the problem and whether it is suitable for the region in which it is considered for application
Potential for an evaluation should be made to insure that a Negative proposed management practice does not cause Impacts a negative impact on the lake ecosystem
Capital Costs standard approaches should be used to evaluate the cost-effectiveness of various practices
Prepared by Aqua Link, Inc. 79 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Operation and these costs should be evaluated to help determine Maintenance the cost-effectiveness of each management practice
Using the above criteria, various in-lake, watershed and institutional practices were carefully evaluated with respect to their overall applicability to the Bradford Lake and its surrounding watershed. Our evaluations relied heavily upon the lake and stream data that were collected and analyzed (Sections 4 and 5.1), field observations obtained during the watershed investigation (Section 5.2) and the calculated hydrologic and pollutant budgets for the study lake (Section 6).
7.1. In-Lake Management Practices
7.1.1. Sediment Dredging
The physical removal of lake sediments can be used to achieve one or more objectives. The most obvious advantage of dredging is the removal of accumulated sediments, thereby allowing for the deepening of the lake. Sediment dredging also removes virtually all of the aquatic plants along with their seeds and roots. The removal of aquatic plants, seeds and roots dramatically reduces the reoccurrence of nuisance aquatic vegetation. In addition, sediment removal can often lower in-lake nutrient concentrations and algal production by preventing the release of nutrients from the sediment.
The cost of dredging is considered expensive, but the benefits are often long-term. This is especially true if appropriate control measures are implemented to minimize the amount of sediment entering the lake. Cook et al. (1993) states that the costs associated with dredging are highly variable and largely depend upon a number of site-specific factors such as, type of equipment used, volume of sediment to be removed, disposal site availability, the density of the sediments, the distance to the disposal sites and the ultimate use of the removed materials. Cooke et al. (1993) summarizes dredging costs for 64 different projects that were originally reported by Peterson in 1981. The unit cost for these sediment removal projects ranged from less than $1.00 to $21.00 per cubic meter (less than $1.00 to $27.48 per cubic yard). Hydraulic dredging costs commonly ranged from $2.25 to $5.65 per cubic meter ($2.94 to $7.39 per cubic yard). Conversely, NALMS (2001) provides dredging costs on a per acre basis. The cost for dredging an average sediment depth of 2 feet ranges from $20,000 to $50,000 per acre. The cost per for dredging an average sediment depth of 5 feet ranges from $40,000 to $80,000 per acre. In other words, the unit cost of dredging typically ranges from $5 to $15 per cubic yard of sediment removed.
The PA Lake Management Society (PALMS 2004b) also notes that dredging costs vary greatly according to type and amount of material, dredging method, disposal site location, sediment contamination levels, season, location within the state and a variety of other factors. Based upon nine different projects, sediment removal costs may vary from approximately $9 per cubic yard for
Prepared by Aqua Link, Inc. 80 Little Neshaminy Creek & Bradford Lake Watershed Assessment
large projects (greater than 200,000 cubic yards) to approximately $150-200 per cubic yard for small projects (1,000-2,000 cubic yards). Costs for projects ranging from 10,000 – 250,000 cubic yards of sediment removed averaged approximately $16 per cubic yard.
Some of the problems associated with dredging are the re-suspension of sediments and nutrients, the disturbance of the benthic (lake bottom) community, and the disturbance of both fishery nesting and refuge areas. During the dredging operation, sediments and nutrients are often re-suspended, which may result in algal blooms, increased turbidity, and decreased dissolved oxygen concentrations. In removing in-lake sediments, many of the residing aquatic organisms will be physically removed or smothered by the settling sediments in areas adjacent to the actual operation. However, continued improvements of dredging equipment and dredging methods have helped to minimize these adverse impacts.
Lake sediments can be removed by mechanical or hydraulic methods. Mechanical dredging can be performed in-lake or after draining the lake. In-lake dredging is often performed using a clamshell bucket, which is operated from an on-shore crane or mounted to a barge. If a drawdown is utilized, lake sediments are excavated using bulldozers (or other excavation equipment) after lake sediments have been sufficiently de-watered. Once the sediment is removed, this material must be loaded into trucks and hauled to the disposal site. If sediments cannot be sufficiently dewatered on site, watertight trucks will be needed. This adds to the volume that must be transported thereby increasing hauling costs of the project. In hydraulic dredging, a dredging barge is unloaded from a trailer into the lake. The barge is equipped with a cutter head, which dislodges the sediments from the lake bottom. Dislodged sediments (as a slurry) are then pumped and piped from the barge to the disposal area. Overall, hydraulic dredging requires a larger disposal/de-watering area since the sediments are pumped as a slurry.
Bradford Lake
The upper end of Bradford Lake is extremely shallow due to heavy sediment loadings that are delivered via the Little Neshaminy Creek and two unnamed tributaries. A preliminary bathymetric survey as discussed in Sections 2.1.1 and 3.2.2 indicates the mean water depth and sediment thickness are approximately 2.4 and 2.5 feet, respectively. In addition, this survey suggests that the lake may have lost up to 6 acres in surface area since its creation in 1975 (Section 2.2.1). It is estimated that Bradford Lake contains about 89,540 cubic yards of unconsolidated sediments. This estimate is based upon a lake surface area of 22.2 acres and the mean sediment depth as determined during the preliminary bathymetric survey that was performed in May 2005.
At this time, the Bucks County and Warrington Township should retain a qualified consultant to perform a dredging feasibility study (Phase I Study) for Bradford Lake. At a minimum, the following tasks should be completed as part of this dredging feasibility study:
Prepared by Aqua Link, Inc. 81 Little Neshaminy Creek & Bradford Lake Watershed Assessment
• Perform a Detailed Bathymetric Survey • Evaluation of Various Dredging Methods • Host a Pre-application Meeting • Determine all Permitting Requirements • Determine Project Cost Estimates to Dredge the Lake
A bathymetric survey using a licensed surveyor must be performed in order to accurately determine the present water volume and volume of unconsolidated sediment in the lake. Information from this survey should be used to prepare water depths and sediment thickness contour maps. Various dredging methods (mechanical vs. hydraulic) should be evaluated for the proposed project. As part of this task, it will be necessary to identify suitable sites for staging all dredging equipment and dewatering dredged sediments.
Next, the County and the Township and its consultant should host a pre-application meeting with representatives of the Pennsylvania Department of Environmental Protection (PADEP), the U.S. Army Corps of Engineers (ACOE) and the Conservation District in order to discuss the project at length. The purpose of this meeting is to gain state and federal support for the project and to clearly identify all permits that must be prepared for the project. In addition, this meeting will identify any sediment testing requirements that may be required by PADEP and ACOE. Lastly, the consultant should prepare preliminary cost estimates for the remaining phases of the project: Phase II – Design and Permitting (includes sediment testing) and Phase III – Sediment Dredging and Supervision.
The estimated cost to perform a Phase I Dredging Feasibility Study for Bradford Lake is $15,000 to $18,000. During this assessment, the consultant should evaluate the possibility of constructing an in-lake sedimentation basin near the confluence of the Little Neshaminy Creek. The goal of this basin, if constructed, would be to remove significant quantities of sediments, thereby decreasing the amount of siltation occurring within the lake itself.
7.1.2. Aeration
Aeration has been widely used in the restoration of lakes, where summer hypolimnetic oxygen depletion and/or winter kill are of major concern. Aeration can be divided into two categories: (1) methods that destratify the lake water column thereby providing for complete recirculation of the entire lake, and (2) methods that only aerate the hypolimnion (deep water layer) without destratification. Both methods are based on the principle that increased dissolved oxygen concentrations will increase the availability of deep water habitats for fish while decreasing the release of phosphorus from the anoxic (low dissolved oxygen containing) sediments. The major difference between the two techniques is that destratifying aerators mix the entire water column resulting in uniform water temperatures from surface to bottom. Conversely, hypolimnetic aerators do not mix the entire lake, but instead only aerate the bottom waters (hypolimnion), thereby allowing
Prepared by Aqua Link, Inc. 82 Little Neshaminy Creek & Bradford Lake Watershed Assessment the lake to remain thermally stratified.
Aeration by destratification works by bubbling air from the lake bottom, thereby causing the water column to circulate. In order for complete mixing to occur the temperature difference from the top to the bottom of the lake should generally be less than 5 degrees Celsius. Hypolimnetic aerators operate by lifting and aerating hypolimnetic water in a closed chamber and circulating the aerated water back into the hypolimnion. When properly sized and installed, hypolimnetic aerators do not allow for lake mixing, thereby retaining stratified layers of water (warmer waters at the surface and colder waters near the bottom) through the summer months. One drawback to hypolimnetic aeration is that occasionally there is oxygen depletion within the metalimnion (between the epilimnion and hypolimnion). It is uncertain if this oxygen depletion creates a significant barrier for fish migration. In general, hypolimnetic aeration is more expensive and can be at least doubled the cost of destratification aeration.
Based on our experience, the typical unit cost per acre for destratification aeration is approximately $1,000 to $2,000. Hypolimnetic aeration is generally twice as expensive as aeration via destratification. The above cost estimates include installation but does not include the cost for bringing electric power to the lake, annual operational costs and any annual equipment maintenance costs.
Bradford Lake
Based upon the 2002 data (Section 4.1.1), a diffused- air aeration system should be installed in Bradford Lake Hydro Logic Products® AirPod XLTM with two in order to improve lake water quality. Very low EPDM Tube Diffusers dissolved oxygen concentrations during the summer months will result in very stressful conditions and production impairment for warmwater (non-salmonid) game fish species like bass and bluegill. Dissolved oxygen concentrations in the lake fell below 1.0 mg/l for water depths exceeding 1.5 meters (4.9 feet) in June and July. The lowest dissolved oxygen levels were very low and uniform throughout the water column in August and September. The dissolved oxygen concentrations ranged from 0.25 to 0.96 mg/L and 2.38 and 2.82 mg/L on the August and September study dates, respectively. Lastly, low dissolved oxygen levels at the lake water-sediment interface suggest that in-lake sediments are likely promoting the internal release of nutrients from sediments.
Based upon similar projects, it is estimated that the cost for purchasing and installing a diffused- air aeration system in Bradford Lake will range from $25,000 to $40,000. This cost does not include bringing electric power to the site or the cost for any services provided by a licensed electrical contractor. At a minimum, the system should include at least six air diffuser units and the air
Prepared by Aqua Link, Inc. 83 Little Neshaminy Creek & Bradford Lake Watershed Assessment
diffusers should be constructed of EPDM, tubular, rubber membranes.
7.1.3. Phosphorus Inactivation
Phosphorus inactivation is a lake restoration that initially removes phosphorus from the water column and then retard to release of phosphorus via in-lake sediments. Under the correct lake conditions, aluminum, iron and calcium salts when added to a lake will form precipitates (i.e., flocs). These precipitates have a tendency to bind-up with both soluble and particulate phosphorus. Eventually, these flocs gradually sink through the water column and then settle on the lake bottom. If enough material is added, a layer of floc may blanket the lake sediments and will subsequently bind with phosphorus that is released by in-lake sediments.
Of these three elements, aluminum is most often selected because it binds tightly with phosphorus and is not affected by low or zero dissolved oxygen levels. In most instances, alum (aluminum sulfate) is added to a lake via boat or barge. In the lake, alum undergoes hydrolysis and forms aluminum hydroxide at pH values between 6 to 8 standard units. Aluminum hydroxide, chemically expressed as Al(OH)3, which is an amorphous precipitate (i.e., floc) that gradually settles to the lake bottom. As this floc settles, both soluble and particulate forms of phosphorus absorbed. When alum is added, the pH of the lake will decline at a rate determined by the initial alkalinity of the water. In softer waters with lower alkalinities), only small doses of alum may be added to the lake before the alkalinity is used up and the pH falls below 6. At pH values between 4 and 6, soluble intermediate forms of aluminum hydroxide (Al(OH)2) and elemental forms of aluminum are the dominant forms. Both of these forms of aluminum can be toxic to the aquatic biota. Therefore, alum treatments are best suited for lakes that are more alkaline. If the pH of a lake is between 6.5 and 7.0, buffered alum (aluminum sulfate plus sodium aluminate) may be applied in order to avoid any adverse impacts to the aquatic biota.
Inorganic iron may exist in a lake as either oxidized ferric iron (Fe3+) or reduced ferrous iron (Fe2+). The solubility of iron is related the pH and the redox potential of the lake. Therefore when dissolved oxygen levels are high, ferrous iron is the most dominate form and can combine hydroxides to form insoluble ferric hydroxides. As a lake restoration technique, ferric chloride may be added to a lake to control in-lake phosphorus levels. Under oxygenated conditions, ferric ions associate with hydroxides to form ferric hydroxides, which will in turn bind with phosphorus. The sorption of phosphorus to ferric hydroxides is greatest when pH levels in the lake are between 5 to 7 standard units. Conversely, ferric hydroxides will become increasingly more soluble as dissolved oxygen concentrations decrease resulting in the release of phosphorus.
Calcium compounds such as, calcium carbonate (calcite) or calcium hydroxide, can be added to lakes to control phosphorus. When added to lakes with high alkalinities, a calcium carbonate precipitate is formed and binds phosphorus to form an insoluble hydroxyapatite. Hydroxyapatite, unlike aluminum hydroxides and ferric hydroxides, has its lowest solubility when pH values are greater than 9.5. The solubility of calcium carbonate and hydroxyapatite dramatically increase as
Prepared by Aqua Link, Inc. 84 Little Neshaminy Creek & Bradford Lake Watershed Assessment
pH and carbon dioxide concentrations increase.
Bradford Lake
At the present time, the use of alum, ferric chloride or calcite for phosphorus inactivation purposes is not recommended. This is primarily because any positive impacts resulting from any of these chemical additions will likely be very short lived. This is due to extremely high nutrient loadings (point and nonpoint sources) from the surrounding watershed and a very short lake hydraulic residence time (Sections 6.2 and 6.1.5, respectively). Furthermore, the nitrogen to phosphorus ratios in this study indicate that the lake is not always phosphorus limiting and can change on a monthly basis (Section 4.1.6.3). This is largely because the lake contains extremely high phosphorus concentrations with moderately high concentrations of nitrogen. Therefore, until incoming phosphorus loadings are substantially reduced, any chemical additions to inactivate phosphorus will have little to no effect on controlling algae if the lake is nitrogen limiting.
It should be noted that ferric chloride should only be applied to the lake after nutrient loadings are significantly reduced and a diffused-air aeration system is installed in the lake. Aeration for Bradford Lake was discussed at length in Section 7.1.3. As discussed in Section 7.1.3, aeration is required to ensure that ferrous iron remains oxygenated as ferric hydroxide, which is a precipitates that binds with phosphorus.
7.1.4. Algal Control Using Algaecides
Algaecides are chemicals applied to lakes to control excessive algal growth. Algaecides restrict algal growth by affecting the individual organism’s ability to photosynthesize. Once photosynthesis has been interrupted, the algae are no longer able to metabolize nitrogen and they die. Copper sulfate (CuSO4) is the most widely used algaecide. This chemical has been available as an algal control for many years and is known to many as “bluestone” (PALMS 2004b).
Algaecides are an effective, inexpensive method for controlling excessive algae growth. Results are often seen within days after the treatment and normal activities in the lake can quickly be resumed. In addition, no specific water use restrictions must be observed following the use of these products.
Although algaecides are an attractive, low-cost, quick fix option for many lakes, their usage does pose some disadvantages. Depending on nutrient concentrations in the lake, algae growth may begin again within days after a chemical algaecide treatment. Therefore, use of chemical algaecides should not be considered a restoration technique, but rather a short-term control for a symptom that has resulted from a much larger lake management problem.
Algaecides have been shown to be toxic to certain fish species. More specifically, species such as trout, grass carp and Koi cannot withstand concentrations of copper that are normally acceptable
Prepared by Aqua Link, Inc. 85 Little Neshaminy Creek & Bradford Lake Watershed Assessment
to other fish species. The potential toxicity of the copper to these species is reduced as water hardness increases.
Additionally, prolonged or excessive use of copper sulfate and/or one of its many formulations can result in the following adverse effects:
• Use of chemical algaecides to treat large areas of excessive algae growth will deplete dissolved oxygen concentrations, which may result in fish kills.
• Over time, copper can accumulate in the sediment, which may adversely affect the health of bottom-dwelling organisms that comprise the lower levels of the aquatic food chain.
• Accumulated copper in lake sediments can increase the cost of dredging projects since dredged sediments containing elevated copper levels may be considered hazardous materials.
• Certain species of blue-green algae can build up a tolerance to copper with prolonged use (PALMS 2004b).
Bradford Lake
Bradford Lake should be treated with copper sulfate in order to control nuisance algal blooms occurring during the growing season (May through September). Copper sulfate can either be tank mixed with water and applied as a liquid or broadcasted in a granular form. Overall, these chemical treatments are aimed at reducing high densities of blue green algae that may be adversely impacting water quality. As noted in Section 2.1.2, Aqua Pennsylvania (formerly Philadelphia Suburban Water Company) observed taste and odor problems at their water treatment facility near Langhorne, Pennsylvania in 2003. An independent investigation performed by the water company claimed elevated Geosmin concentrations in the Neshaminy Creek were caused by benthic blue-green algae in the lake. Geosmin is a metabolic by-product product that is released by some algae and may result in musty, moldy and earthy taste and odor problems for water supply companies. Other benefits include improved water clarity (transparency) by reducing the phytoplankton in the lake.
The estimated cost for applying copper sulfate to the lake is $750 to $1,000 per treatment. All treatments must be performed by a Pennsylvania licensed commercial applicator. In order to proceed, a permit application must be completed and sent to the PA Fish and Boat Commission for applying any aquatic algicides or herbicides in a pond or lake. This includes all ponds and lakes even if the water body is fully contained on the owner’s property and has no outlet. Thereafter, aquatic chemical treatments can only be applied to lakes and ponds once you have received an approved permit.
Prepared by Aqua Link, Inc. 86 Little Neshaminy Creek & Bradford Lake Watershed Assessment
It is recommended that a diffused-air aeration system be installed prior to applying any aquatic pesticides (algaecides or herbicides) to the lake. Overall, aquatic pesticides kill vegetation, which then decays and consumes dissolved oxygen during the process. In some cases, dissolved oxygen in ponds may fall below 3 milligrams per liter (mg/l) throughout the water column and subsequently can result in a fish kill. In addition, dissolved oxygen concentrations less than 1 mg/l near the sediments will promote the internal release of nutrients from these sediments. As noted in Section 4.1.1, Bradford Lake already has very low dissolved oxygen levels and in some instances these concentrations fell below 1 mg/l in 2002.
7.1.5. Aquatic Plant Control Methods
The major methods for controlling nuisance levels of aquatic vegetation (macrophytes) can be grouped according to their modes of action. The four major modes of action are physical, biological, chemical and habitat manipulation. Physical controls, which often require the use of specialized equipment to remove or damage all or a portion of the plants, include a wide variety of lake management techniques such as mechanical harvesting, hydroraking and rototilling. Hand pulling is another physical technique that is generally limited to the removal of smaller, isolated stands of nuisance aquatic plants. Biological controls involve the stocking of aquatic organisms to consume and damage nuisance stands of aquatic vegetation. Common biological controls are the use of grass carp and aquatic insects (aquatic weevil). Chemical controls, the oldest and widely most widely used of all the methods, involve the use of aquatic pesticides (herbicides) to kill nuisance aquatic plants. Lastly, habitat manipulation involves altering the environment, thereby making the lake less desirable for the growth of aquatic vegetation. Common management techniques associated with this mode of action are water level drawdown and the use of benthic barriers.
Based upon this assessment, about 70 percent of the surface area of Bradford Lake was choked with nuisance aquatic vegetation in the late summer of 2002. By far, the most dominant aquatic plant in Bradford Lake was water chestnut Water chestnut (Trapa natans). This very invasive and aggressive plant is impacting the recreational value of the lake. For example, dense stands of water chestnut severely restrict fishing from the shoreline during the summer recreational season. Also, the decomposition of large dense stands of water chestnut are likely to result in dangerously low dissolved oxygen levels, thereby adversely impacting aquatic life as discussed in Section 4.2.
The two most practical methods for controlling water chestnut in Bradford Lake is the use of aquatic herbicides and mechanical harvesting. These plant management control practices will need to be implemented for at least 5 years in order to successfully to deplete the seed bank within the lake sediments. Thereafter, the lake should be inspected annually and isolated stands of water chestnut can be hand pulled or chemically treated. Conversely, neither the use of aquatic herbicides or mechanical harvesting will be required if the lake is deepened by dredging as discussed in Section 7.1.1.
Prepared by Aqua Link, Inc. 87 Little Neshaminy Creek & Bradford Lake Watershed Assessment
7.1.5.1. Aquatic Herbicides
Aquatic herbicides are chemicals specifically formulated for use in water to kill or control aquatic plants (macrophytes). Herbicides approved for aquatic use by the United States Environmental Protection Agency have been reviewed and considered compatible with the aquatic environment when used according to label directions. However, individual states may also impose additional constraints on their use.
Aquatic herbicides are sprayed directly onto floating or emergent aquatic plants or are applied to the water in either a liquid or pellet form. Systemic herbicides are capable of killing the entire plant. Contact herbicides cause the parts of the plant in contact with the herbicide to die back, leaving the roots alive and capable of regrowth. Non-selective herbicides will generally affect all plants that they come in contact with. Selective herbicides will affect only some plants (often dicots, broad leafed plants, like Eurasian watermilfoil will be affected by selective herbicides whereas monocots like Brazilian elodea are not affected).
Bradford Lake
If dredging is not performed, stands of water chestnut in Bradford Lake may be controlled using an appropriate aquatic herbicide. Herbicides with the active ingredients of either 2,4-D (Navigate or AquaKleen) or imazapyr (Habitat) have successfully been used to treat water chestnut. These chemicals should be applied to the lake in the spring or early summer before this plant produces seeds. It is estimated that the cost to chemically treat the lake is between $7,500 and $12,000 annually.
Similarly to algaecide treatments, a permit must be obtained from the Pennsylvania Fish and Boat Commission before the herbicide can be applied to any public or private waterway. There is no fee for the permit, but it must be renewed annually. In addition, if the herbicide will be applied to a public waterbody, a licensed commercial applicator must perform the treatments (PALMS 2004b).
7.1.5.2. Mechanical Harvesting
Mechanical weed harvesting is performed by using a large barge equipped with cutting blades mounted on the front of a harvester or barge. The cutting blades are used to clip off the stems of the aquatic plants below the water surface. As the cut plants float to the surface they are collected on a conveyor and stored on the harvester. When the harvester is full, it returns to the shoreline where it uses the conveyor to unload the harvested plant material onto trucks for transport to a disposal site.
Mechanical weed harvesting is one of the most widely accepted methods for the control of rooted aquatic plants. Harvested areas are immediately available for use without any water-use restrictions, and the ecological effects that sometimes occur following weed harvesting are minor in comparison to the overall benefit to the lake community.
Prepared by Aqua Link, Inc. 88 Little Neshaminy Creek & Bradford Lake Watershed Assessment
With limited exceptions, mechanical harvesting can be accomplished in almost any lake that is experiencing excessive plant growth. However, mechanical harvesting is best suited for use in six to eight feet of water where the cutter can effectively reach the lower portions of the plant stem. At shallower depths, the harvester is not able to move effectively, often getting hung up on the lake bottom or submerged objects. In deeper water, the plant stems tend to Mechanical Harvester be pushed away from the cutter and the maximum amount Source: PMC Aquatic Equipment Web: www.pmcproduction.com of material is not removed on each pass.
Accessibility to the lake is a major consideration in planning the use of a mechanical weed harvester. If access to the lake is limited, mechanical harvesting may not be a practical management consideration. Harvesters are large bulky pieces of equipment, and often times a crane is needed to lift the harvester from its transport trailer and place it in the lake. In addition, plant material collected by the harvester is typically unloaded directly onto trucks at the launch site. Therefore, the launch area should be in close proximity to a roadway and be stable enough to support the movement of heavily loaded vehicles (PALMS 2004b).
Mechanical weed harvesting can have minor negative effects on the lake’s fishery. Juvenile fish that become trapped in the harvested plant material are inadvertently removed from the population. When this occurs in successive years, the fish population can become unbalanced. However, this problem can be avoided or at least minimized by controlling when and where specific areas of the lake are harvested.
Another disadvantage is that certain species of plants, especially Eurasian watermilfoil, can become established in new areas of the lake when fragments not collected by the harvester are re- distributed by wind and wave action. This can result in the spread, rather than control, of the nuisance plant species that the weed harvesting program was targeting (PALMS 2004b).
Bradford Lake
Stands of water chestnut in Bradford Lake should be mechanically harvested annually if the lake is not dredged and aquatic herbicides are not applied to the lake. This is largely because water chestnut is a good candidate for harvesting since it does not reproduce via plant fragmentation but
Prepared by Aqua Link, Inc. 89 Little Neshaminy Creek & Bradford Lake Watershed Assessment
only by seed. One limiting factor in using this technique is that the barge may have difficult maneuvering in the upper section of the lake due to extreme shallowness (Figure 2.1). Once harvested, cut plant materials should be stock piled at the surrounding parkland and then allowed to compost.
The literature suggests that mechanical harvesting may cost anywhere from $200 to over $1,500 per acre depending upon local site conditions and how many acres actually will be harvested. Based upon this investigation, it was assumed that mechanical harvesting costs will likely range from $11,250 to $15,000 annually. This cost estimate assumes a treatment area of 15 acres and unit mechanical harvesting cost ranging from $750 to $1,000 per acre.
7.2. Watershed Best Management Practices
As discussed in Section 5.2, Aqua-Link performed a watershed investigation to identify significant sources of nonpoint pollution to Bradford Lake. In the paragraphs below, applicable best management practices were evaluated in order to reduce the pollutant loadings from streambank erosion, active land development and existing residential and commercial land uses.
7.2.1. Bank Stabilization & Protection
Bank erosion is a major source of nutrients and sediments to streams and lakes. Excessive nutrients may result in accelerated rates of eutrophication such as, algal blooms in lakes and depleted dissolved oxygen levels in both streams and lakes. Excessive sediments in streams and lakes will adversely affect aquatic life and their habitats. In addition, high levels of sedimentation in lakes will result in shallowness and the loss of lake water volumes, which will eventually impair desirable and/or designated lake uses.
7.2.1.1. Streambank Stabilization
Streambank protective measures generally can be grouped into three categories: vegetative plantings, soil bioengineered practices and structural techniques. Soil bioengineering is a system of living plant materials that are used as structural components for bank stabilization. Common soil bioengineered techniques for streams are brush mattresses, live stakes, joint plantings, vegetated geo-grids, branch packing and live fascines (USDA 1996). Structural techniques include placed rock or boulders, riprap, gabions and retaining walls. In many instances, these three categories are used in combination with one another when stabilizing eroding streambanks.
Marginal levels of streambank erosion are often stabilized using vegetative plantings such as, live stakes from willow (e.g., black willow, basket willow or purple osier willow) and dogwood trees. Live stakes should be about 24 inches long with a 3/8-inch minimum diameter at the butt end. Live stakes frequently are planted three-foot on center. Soil bioengineered techniques such as, live fascines, in conjunction with coir fiber logs and live stakes can be used to stabilize moderately
Prepared by Aqua Link, Inc. 90 Little Neshaminy Creek & Bradford Lake Watershed Assessment eroding streambanks. Live fascines (bundles of live branch cuttings generally from willow trees) may be installed along the lower third of the bank and at mid-bank, while coir fiber logs are often installed at the toe of the bank (edge of water) for additional support and stabilization. Typical costs for purchasing and installing live stakes and live fascines are $1 and $18 per stake and linear foot, respectively (King et al 1994). Costs for purchasing and installing coir fiber logs may range from $8 to $15 per linear foot.
Severely eroding streambanks are often stabilized using a combination of vegetative plantings, soil bioengineered techniques and structural practices. First, the streambanks are typically cut back and regarded to a 2:1 to 3:1 slope if possible. Rock with a geo-textile fabric is generally placed at the
Plan Views of Rock Cross Vane and J Hook Rock Vane
toe of the bank. The re-graded bank is seeded with desirable, erosion resistant grasses. Woody plant materials (as live stakes, seedlings or containerized plants), which are approved for soil bioengineering in riparian areas, are installed adjacent to the placed rock to the top of the bank. Live stakes from willow (e.g., black willow, basket willow or purple osier willow) and dogwood trees are installed in between the placed rocks for additional stability and enhancing the overall appearance of the project site. The installation of live stakes within placed rock is commonly referred to as “joint planting”. Also depending upon the length of the slope, live fascines may be installed along the lower third of the bank and at mid-bank for additional support and stabilization. Typical costs for purchasing and installing rock with live stakes is $80 per linear foot, respectively (King et. al. 1994).
Prepared by Aqua Link, Inc. 91 Little Neshaminy Creek & Bradford Lake Watershed Assessment
In addition, natural stream channel design (NSCD) structures, such as J hooks or rock vanes, can be installed along the outer bend of stream channels. The purpose of installing these structures is to further protect the bank by redirecting the streamflow towards the center of the channel (conversely, away from a eroding or recently stabilized bank) during bankfull conditions.
Prior to implementation, it will be necessary to obtain the proper permits from the Pennsylvania Department of Environmental Protection (PA DEP) for these projects. Under normal circumstances, a general permit (GP-3) is commonly issued for projects that are less than 500 linear feet and an Individual Permit for Small Projects is issued for projects greater than 500 linear feet. The proposed installation of any NSCD structures will require an individual permit regardless of the size of the project area.
Bradford Lake Watershed
It is recommended that the severe streambank erosion occurring at the Fairways Golf and Country Club (Photograph No. 6 in Figures 5.2 and 5.3) be stabilized using bioengineering practices. Banks with minor erosion can be stabilized by installing plant materials (live stakes and/or containerized plants) along with coir fiber logs. More severe bank erosion should be stabilized using placed rock. The placed rock should be joint planted using live stakes. Where needed, steep sided banks should first be cut back and regarded to a 2:1 slope if possible. All placed rock should be underlain with a geo-textile fabric. In addition to these bank stabilization measures, a riparian buffer should be established along the entire length of the stream at this golf course as described in Section 7.2.1.2.
7.2.1.2. Riparian Buffers
Riparian buffers are undisturbed vegetative strips that are adjacent to surface waters. Established vegetation along streams and lakes provide numerous benefits such as, filtering out sediments transported by surface runoff, nutrient uptake, wildlife habitat, shading and soil binding via plant roots. Grasses and herbaceous vegetation are best suited as filters, while woody vegetation (shrubs and trees) provide excellent protection against bank erosion.
Riparian buffers should consist of various layers of vegetation (grasses, herbaceous vegetation, shrubs and trees) to achieve optimal benefits. To provide an array of functions, riparian buffers are generally 35 to 100 feet in width. One approach used by the USDA Forest Service is to establish a three-zoned riparian buffer. Zone 1 is the nearest to the streambank and has a recommended fixed 15-foot width. Plants selected for this zone must exhibit excellent soil stabilizing characteristics and need to be capable of tolerating wet soil conditions and periodic flooding. Zone 2 is recommended to be at least 60-feet wide and is considered a managed forest. Within this zone, trees may be harvested to promote nutrient removal as newly planted trees take up more nitrogen. Zone 3 (if required) is recommended to be 20-feet wide and consists of dense grasses and forbs to convert concentrated water flow to uniform sheet flow (Alliance for the Chesapeake Bay 1998).
Prepared by Aqua Link, Inc. 92 Little Neshaminy Creek & Bradford Lake Watershed Assessment
The unit cost for establishing riparian buffers is quite variable and highly depends on the type of plant materials used. The least expensive approach is to use seedlings and bare root stock, while the more expensive approach is to install plants as balled and burlapped (B&B) or large container stock. Seedlings are typically planted at 6 to 10 feet spacing or roughly 700 seedlings per acre. Bare root stock are generally planted 14 to 16 feet apart or about 200 plants per acre when the bare root plants are several feet in height and around ¾ inches in diameter. Balled and burlapped or large containerized plants are planted 16 to 18 feet apart or approximately 150 plants per acre (Alliance for the Chesapeake Bay 1998).
For comparison, unit cost estimates to install the various materials are as follow: $120 to $ 495 per acre for seedlings, $575 to $1,500 per acre for bare root stock and $2,700 to $7,500 per acre for balled & burlapped (B&B) and container stock (Alliance for the Chesapeake Bay 1998). The above costs do not include any costs associated with developing a riparian design plan, fencing, tree shelters (tubes) and maintenance (mowing or herbicide treatments).
Bradford Lake Watershed
A riparian buffer should be established along the entire section of stream that meanders through the Fairways Golf and Country Club. The stream passing through the golf course is Unnamed Tributary A, which is located in the UNTA subwatershed. Typical views of this unnamed tributary are shown as Photograph Numbers 4 and 6 in Figures 5.2 and 5.3.
7.2.2. Stormwater Retrofits
Urbanization has a profound influence on stream and lake water quality. These impacts are more readily observed in older urban settings without any or inadequate stormwater controls as compared to newer urban areas (Schueler 1987). In general, stormwater management systems in older urban areas were designed to quickly capture surface runoff from impervious areas (roof tops, sidewalks, roadways, parking lots) and pipe it directly to receiving streams. In addition, increased imperviousness in a watershed subsequently results in less rainfall infiltration and percolation resulting in lower levels of groundwater recharge.
Urbanization allows for changes in watershed hydrology, changes in stream geometry, the degradation of aquatic ecosystems and pollutant export during construction and after site stabilization. Watershed hydrology is significantly altered after urbanization. Peak stream discharges are increased about 2 to 5 times higher than pre-development levels. The volume of stormwater runoff produced by individual storms is increased. For example, a moderately developed watershed many produce 50 percent more runoff than a forest watershed. The time required for runoff to reach a stream (time of concentration) is significantly decreased by as much as 50 percent. In addition, changes in watershed hydrology result in increased frequency and severity of flooding, reduced streamflow during prolonged periods of dry weather (due to decreased rates of soil infiltration) and
Prepared by Aqua Link, Inc. 93 Little Neshaminy Creek & Bradford Lake Watershed Assessment
greater runoff velocities during storm events (Schueler 1987).
Streams now must readjust (change in geometry) to the new hydrologic conditions in urban areas. The primary adjustment for increased stormwater volumes is channel widening. Stream channels may widen 2 to 4 times their original size if post-development runoff is not effectively controlled. The elevation of the stream’s floodplain also will increase to accommodate higher post- development peak discharge rates, therefore, property and structures not previously at risk to flooding now may be at risk. Streambanks are gradually undercut and slump into the stream channel. Trees that previously protected the banks are now exposed at the roots and sometimes become windthrown, thereby triggering a second phase of bank erosion. Eroded soils from streambanks and upland areas are temporarily stored in the stream channel as sand bars and other sediment deposits. Gradually, these sediments migrate throughout the stream network as bedload, but unfortunately the stream channel will inevitably be covered by shifting deposited mud and coarse sands for many years to come (Schueler 1987).
In addition, urbanization adversely affects the overall composition of aquatic ecosystems. Increased levels of pollutants to receiving waters often result in lower levels of species diversity and the dominance of more tolerate, less desirable aquatic insects and fish. Pollutants are exported during construction and after site stabilization. There is a very high potential for large quantities of sediment with attached nutrients and organic matter to be transported to streams and lakes from active construction sites. This potential is greatly reduced when adequate erosion and sediment controls are properly installed and maintained. After construction, pollutants rapidly accumulate on impervious surface and are readily transported to receiving waters via stormwater runoff. These pollutants include sediments, nutrients, bacteria, oxygen consuming substances, oil and grease, metals, toxic chemicals and chlorides. In addition, increased temperatures of stormwater runoff (thermal pollution) will result in increased temperatures of receiving waters (Schueler 1987).
Land development (urbanization) prior to the 1970’s had little to no stormwater management practices. Stormwater systems were primarily built only to transport runoff rapidly to receiving waters. In the 1970’s, efforts began to address runoff induced flooding. Stormwater control structures including detention basins were generally designed to accommodate only peak rates of runoff. Therefore, these structures only held runoff for a few hours until it was deliberately discharged to receiving waters and did not address the loss of groundwater recharge, poorer runoff water quality or increased runoff volumes over pre-development conditions (Delaware Riverkeeper 2001).
The primary problem with the peak rate of runoff design for stormwater control structures (detention basins) is that receiving waters receive increased stormwater volumes for longer periods of time. Structures of this design throughout a watershed have a cumulative net effect of actually increasing the instream peak discharge rates and water volumes for extended periods. Therefore, the final result is that downstream flooding is exacerbated since flood flow is increased and extended (Delaware Riverkeeper 2001).
Prepared by Aqua Link, Inc. 94 Little Neshaminy Creek & Bradford Lake Watershed Assessment
In addition, most detention basins are designed to control only 10 to 100-year frequency storms and fail to impact the 2 to 5-year storms. Many detention basins are designed to pass these smaller storm runoff volumes directly to streams. In general, the 2-year storm in a natural watershed produces bankfull discharge. Bankfull discharge is that amount of flow that fills the stream to the top of its banks. In urban areas, smaller, more frequent storms can result in bankfull conditions because of increased runoff volumes. Bankfull discharge is considered the effective discharge for stream channel formation (channel widening, channel downcutting and bank erosion) as later described in Section 7.2.3.
Stormwater best management practices (BMP’s) that are later incorporated into existing developments and urban areas is referred to as stormwater retrofitting. Retrofitting may only require minor modifications to existing control structures like detention basins or the construction of new control structures or devices. The underlying goal of retrofitting is to correct many of the problems that were described above. Below is a list of common retrofits that may be employed for existing stormwater detention basins (CH2MHill et. al. 1998):
• Modifying the outfall to create a two-stage release to better control smaller storms while not significantly compromising the major detention required for flood control
• Eliminating paved low-flow channels and replacing them with meandering vegetated swales
• Eliminating low-flow bypasses
• Incorporating low berms to lengthen the flow path and eliminate short-circuiting
• Incorporating stilling and settling basin at inlets
• Regrading the basin bottom to create a wetland area near the outlet or revegetating parts of the basin bottom with wetland vegetation to enhance pollutant removal, reduce mowing and improve aesthetics
• Creating a wetland shelf along the periphery of a wet basin to improve shoreline stabilization, enhance pollutant filtering and enhance esthetic habitat functions
Prepared by Aqua Link, Inc. 95 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Bradford Lake Watershed
It is recommended that Warrington, Horsham and Montgomery Townships jointly perform a stormwater retrofitting assessment for all the lands lying within the Bradford Lake watershed. All existing detention basins and other significant stormwater controls should be identified and evaluated for retrofitting. The primary goal of these retrofits is to improve the water quality of stormwater runoff before it is discharged to nearby streams and Bradford Lake. Thereafter, all identified stormwater structures should be prioritized and upgraded when state or federal funding becomes available.
7.2.3. Conservation & Nutrient Management Plans
Conservation plans use a combination of land use and farming practices to protect and improve soil productivity and water quality, and to prevent deterioration of natural resources on all or part of a farm. These practices may include contour strips, crop rotation, conservation tillage diversions, grassed waterways, wind breaks, wildlife habitat, nutrient management manure storage, stream bank fencing and buffer strips. Plans are often prepared by the conservation districts and designed to meet the technical standards developed by the USDA Natural Resources and Conservation Service (NRCS). Financial assistance is available to farmers interested in implementing structural or land management practices.
Nutrient management plans are prepared to address water quality issues that can result from the misapplication of manure and fertilizer nutrients. The Nutrient Management Act, Act 6 of 1993, became effective in October 1997 and specifies that certain agricultural operations prepare and implement a nutrient management plan. Nutrient management plans are required for farms having two or more animal equivalent units (2,000 pounds live weight) per acre of farmland that receives manure. In addition to these concentrated animal operations (CAOs), the act encourages other dairy, livestock, and poultry operations to voluntarily prepare, submit for approval, and implement nutrient management plans that meet the specifications of Act 6. An approved nutrient management plan can provide economic benefits to most agricultural producers through better utilization of all crop production nutrients; can demonstrate responsible farming practices to nonfarm neighbors; and can provide limited protection for any participating livestock or poultry producer from civil actions, penalties, or damages resulting from nutrient misuse (The Pennsylvania State University).
Bradford Lake Watershed
It is recommended that the Conservation District develop and implement conservation and nutrient management plans for all farms located within the watershed. Based upon this assessment, farming is very limited and primarily is located within the lower Little Neshaminy Creek and Unnamed Tributary B subwatersheds.
Prepared by Aqua Link, Inc. 96 Little Neshaminy Creek & Bradford Lake Watershed Assessment
7.3. Institutional
7.3.1. Establishing a Watershed Organization
By definition, a watershed association is a group of citizens living and working within a watershed who are concerned with existing local issues. In most instances, the primary objective of a watershed association is to improve and further protect water quality and aquatic habitat. Ideally, watershed associations should have members with varied interests, such as agriculture, education, business, industry, professional organizations, civic and conservation groups, nature centers and local governments.
It is recommended that a watershed association be formed for the Bradford Lake watershed. This association should be comprised of individuals representing the Bucks County Department of Parks and Recreation, local municipalities (Warrington, Horsham and Montgomery Townships), the conservation district and local conservation organizations such as the Heritage Conservancy. Other potential members should include local students, individuals from local sportsmen groups, local farmers and other interested residents. The primary goal of this association should focus on improving and further protecting the water quality and aquatic habitats of Bradford Lake and its tributaries. The association can work towards this goal by implementing various key components of the recommended management plan in Section 8 of this report.
Information on how to form a watershed association can be obtained from the Pennsylvania Organization for Watersheds and Rivers (POWR) at the following website: www.pawatersheds.org..
7.3.2. Land Acquisition & Protection
There are a number of ways that local municipalities and conservation organization can protect environmentally sensitive areas in order to further protect the water quality of nearby streams and lakes. Two of the more common methods are land acquisition and conservation easements.
Land acquisition is used in select cases when willing landowners want to conserve their land by selling or donating it outright to a public agency or land conservation organization. This mechanism allows the public agency to have full control over a property's future (1000 Friends of Minnesota at www.1000fom.org).
A conservation easement is a legal agreement between a landowner and a land trust that permanently protects open space by limiting the amount and type of development that can take place, but continues to leave the land in private ownership. A conservation easement can also be negotiated between a landowner and a government
Prepared by Aqua Link, Inc. 97 Little Neshaminy Creek & Bradford Lake Watershed Assessment
agency (Land Trust Alliance at www.lta.org).
When a conservation easement is donated or sold to a land trust, the landowner can continue to live on or work the land in accordance with the easement's provisions. The landowner can sell the land or pass it on to heirs. Donating the easement can result in reduced income and estate taxes (Land Trust Alliance a at www.lta.org). In addition, conservation easements allow municipalities to stretch their open-space preservation dollars to help protect scenic areas and farmlands and, preserve and buffer streams and other environmentally sensitive areas, such as wetlands.
Bradford Lake Watershed
Local municipalities and the conservation district with the assistance of the Heritage Conservancy should work on protecting and enhancing more stream buffers by either acquiring these lands or securing conservation easements.
7.3.3. Ordinances for Protecting Water Quality
7.3.3.1. Riparian Corridor Protection
Riparian corridors are those areas immediately surrounding surface waters. When properly maintained, riparian corridors aid in protecting water quality by filtering out pollutants from surface runoff and overland flow, stabilizing streambank and lake shoreline areas from erosion, providing shade to adjacent waters, providing critical habitats for wildlife and enhancing aesthetics.
More information about model ordinances for riparian buffers can be found at the Stormwater Manager’s Resource Center (SWMRC) at www.stormwatercenter.net. This site is maintained by the Center for Watershed Protection (CWP) and their website address is www.cwp.org. Also, Doylestown Township in Bucks County may be contacted in order to obtain a copy of their riparian corridor protection ordinance (www.doylestownpa.org).
Bradford Lake Watershed
It is recommended that all municipalities (Warrington, Horsham and Montgomery Townships) develop and adopt a riparian corridor protection ordinance. The ordinance should be based upon establishing a riparian corridor conservation district, which applies to all lands that are adjacent to waterways in the municipalities. The district may consist of several different zones, where permitted uses are specified for each zone.
7.3.3.2. Stormwater Management Ordinance
In accordance with the Pennsylvania Stormwater Management Act 167, counties are required to manage stormwater runoff on a watershed-wide basis rather than on a site-by-site basis.
Prepared by Aqua Link, Inc. 98 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Historically, individual municipalities have managed stormwater runoff by reviewing subdivision and land development plans in light of established ordinances. A key component of Act 167 is that municipalities manage stormwater runoff using newly created ordinances. These ordinances are developed using a model stormwater ordinance that was specifically created for an entire watershed. In general, watersheds are divided into stormwater management districts and these districts are assigned individual development and predevelopment runoff rates.
Currently, the Bucks County Planning Commission is updating the 1996 Stormwater Management Plan for the Little Neshaminy Creek. The updated plan is being prepared by being prepared by Borton-Lawson (Wilkes-Barre, PA) and is expected to be completed in next year or so. The original 1996 plan focused on peak rate controls for stormwater runoff. Conversely, the updated plan will address both peak rate control and provide standards for water quality. Once completed, the planning commission will be encouraging all municipalities to adopt the stormwater management model ordinance of the updated Act 167 Stormwater Management Plan.
Bradford Lake Watershed
It is recommended that all municipalities (Warrington, Horsham and Montgomery Townships) in the Bradford Lake watershed eventually adopt the stormwater management model ordinance of the updated Act 167 Stormwater Management Plan for the Little Neshaminy Creek.
7.3.3.3. Lawn Fertilizer Ordinance
Some municipalities have developed ordinances to eliminate or reduce the use of phosphorus containing fertilizers on residential lawns. The purpose of developing and adopting a lawn fertilizer ordinance is to protect stream and lake water quality. This of course is accomplished by reducing phosphorus loadings to nearby surface waters from maintained lawn areas.
Example of the lawn fertilizer ordinances that were adopted by the City of Owatoona in Minnesota (www.ci.owatonna.mn.us) and the Dane County Lakes and Watershed Commission (DCLWC) located in Madison, Wisconsin (www.co.dane.wi.us/commissions). The last ordinance was adopted as a countywide ordinance for all of Dane County.
Bradford Lake Watershed
It is recommended that all municipalities (Warrington, Horsham and Montgomery Townships) in the Bradford Lake watershed consider adopting a lawn fertilizer ordinance to protect the water quality of Bradford Lake.
Prepared by Aqua Link, Inc. 99 Little Neshaminy Creek & Bradford Lake Watershed Assessment
7.3.4. Point Source Discharges
Point source discharges require a NPDES (National Pollution Discharge Elimination System) permit to discharge treated wastewater effluent or process waters to waters of the Commonwealth. According to their NPDES permits, point source dischargers are monitored frequently and must comply with flow and water quality criteria, as established by the PA DEP, or be fined for noncompliance. By way of this assessment, it was determined that three point sources are located in with the Little Neshaminy Creek subwatershed in the Bradford Lake watershed. For more information, refer to Section 6.2.1 entitled Point Sources.
Bradford Lake Watershed
In 2003, PA DEP completed a total maximum daily load (TMDL) assessment for the entire Neshaminy Creek Watershed (PA DEP 2003) as discussed in Section 1.2. This assessment was conducted in order to improve the water quality of all the impaired stream segments listed on the State’s 303(d) List of Impaired Streams, which includes the entire main stem of the Little Neshaminy Creek and its primary tributary, Park Creek. Based upon this TMDL assessment, PA DEP will likely require the three point source dischargers to lower their phosphorus effluent concentrations in order to improve the water quality of the Little Neshaminy Creek and subsequently Bradford Lake.
7.3.5. Education
The newly formed watershed association (Section 7.3.1) should develop educational materials about homeowner best management practices and the results of this assessment. These materials can be developed as tri-fold brochures (fact sheets) and distributed at the conservation district and municipal government offices. In addition, these educational materials can be bulk mailed to all residents throughout the watershed.
Some suggested homeowner best management practices that may be presented are:
• Proper Lawn Mowing Methods • Proper Maintenance of On-Lot Septic Systems • Use of Low or No Phosphorus Lawn Fertilizers • Establishing Low Maintenance Landscapes • Limiting the Use of Pesticides • Establishing & Maintaining Riparian Buffers • Use of Rain Barrels to Collect Roof Top Runoff • Creating Rain Gardens • Illegal Disposal to Storm Sewer Drains
Prepared by Aqua Link, Inc. 100 Little Neshaminy Creek & Bradford Lake Watershed Assessment
7.3.6. Water Quality Monitoring
Baseline water quality monitoring programs for both lakes and streams are often implemented after a comprehensive assessment has been completed. Newly acquired data are routinely entered into the existing water quality database and analyzed. The comparison of newly acquired data to past data is commonly referred to as “water quality trend analysis”. Water quality trend analysis is an invaluable tool in assessing water quality improvements or degradation over time. Hence, water quality trend analysis provides water resource professionals and watershed stakeholders the opportunity to carefully evaluate the overall success of any implemented in-lake and watershed restoration measures.
Aqua Link strongly recommends that the water quality of the streams and the lake continue to be monitored annually. Monitoring should be performed at the established stream and lake monitoring stations that were used during this assessment. All stream stations should be monitored once again during both baseflow and stormflow conditions. All lake and stream samples should be collected and analyzed for the same parameters as described in Section 3.2 by a certified laboratory. It is highly recommended that the certified laboratory use the same analytical procedures and detection limits as cited in the U.S EPA approved Quality Assurance – Quality Control Plan for the Warrington (Bradford) Lake and Little Neshaminy Creek Watershed Assessment Project dated April 28, 2002 (Aqua Link, Inc. 2002).
Prepared by Aqua Link, Inc. 101 Little Neshaminy Creek & Bradford Lake Watershed Assessment
8. Comprehensive Lake and Watershed Management Plan
A lake and watershed management plan was prepared to improve and further protect the water quality of Bradford Lake and its tributaries. This management plan was developed by carefully evaluating all of the lake and watershed information and data that were acquired and analyzed as part of this project.
Based upon this assessment, the primary goal of the Bradford Lake and watershed management plan is to reduce nonpoint source pollutants, namely nutrients and sediments, to streams and subsequently the lake itself. This plan consists of key recommendations in order to improve and further protect stream and lake water quality. These key recommendations (categorized as in-lake, watershed and institutional best management practices) are summarized in Sections 8.1 through 8.3 and Table 8.1.
Table 8.1 provides a priority ranking of all recommendations by category and identifies the most appropriate watershed stakeholders that should implement these recommendations. Many of these recommendations will require a high level of technical expertise; therefore, various watershed stakeholders will likely require the professional services of a qualified environmental consultant. Many of the recommendations should be implemented by maximizing (where possible) the use of local volunteers including students. In addition, Table 8.1 lists the sections of this report where each of the recommendations was previously discussed in greater detail along with any associated costs.
8.1. In-Lake Restoration
Recommended in-lake restoration techniques for Bradford Lake are (refer to Section 7.1 and Table 8.1):
• Sediment Dredging • Aeration using Diffused-Air • Algae Control using Algaecides • Aquatic Plant Control using Herbicides • Aquatic Plant Control via Mechanical Harvesting
As noted in Section 7.1.1, the upper end of Bradford Lake is extremely shallow due to heavy sediment loadings that are delivered via the Little Neshaminy Creek and two unnamed tributaries. A preliminary bathymetric survey indicates that the lake has a mean water depth and sediment thickness of approximately 2.4 and 2.5 feet, respectively. In addition, this survey suggests that the lake may have lost up to 6 acres in surface area since its creation in 1975. At this time, the Bucks County and Warrington Township should retain a qualified consultant to perform a dredging feasibility study (Phase I Study) for Bradford Lake. The estimated cost to perform a Phase I Dredging Feasibility Study for Bradford Lake is approximately $15,000 to $18,000.
Prepared by Aqua Link, Inc. 102 Little Neshaminy Creek & Bradford Lake Watershed Assessment
A diffused-air aeration system should be installed in Bradford Lake in order to improve lake water quality and ecological health of this reservoir. This in-lake best management practice should be implemented regardless of whether the lake is dredged or not. Based upon this assessment, very low dissolved oxygen concentrations during the summer months will result in very stressful conditions and production impairment for warmwater fish species like bass and bluegill. In addition, anoxic in-lake sediments may promote the internal release of nutrients from sediments and low dissolved oxygen concentration allow for the buildup of hydrogen sulfide gas and the formation of toxic ammonium nitrogen. Based upon similar projects, it is estimated that the cost for purchasing and installing a diffused-air aeration system in Bradford Lake will range from $25,000 to $40,000. This cost does not include bringing electric power to the site or the cost for any services provided by a licensed electrical contractor. At a minimum, the system should include at least six air diffuser units and the air diffusers should be constructed of EPDM, tubular, rubber membranes.
Bradford Lake should be treated with copper sulfate in order to control nuisance algal blooms occurring during the growing season (May through September) on an as-needed basis. Copper sulfate can either be tank mixed with water and applied as a liquid or broadcasted in a granular form. Overall, these chemical treatments are aimed at reducing high densities of blue green algae that may be adversely impacting water quality in the lake and diminishing the quality of the Neshaminy Creek as a source of drinking water (Section 2.1.2). The estimated cost for applying copper sulfate to the lake is $750 to $1,000 per treatment. The lake may need to be treated 2 to 6 times per year and the cost of these treatments should be fully or partially paid for by Aqua Pennsylvania, who owns and operates the water treatment facility in Langhorne.
Nuisance stands of water chestnut in Bradford Lake should be controlled either using aquatic herbicides or mechanical harvesting equipment if dredging is not performed. Aquatic herbicides with the active ingredients of either 2,4-D (Navigate or AquaKleen) or imazapyr (Habitat) have been used successfully to kill water chestnut. These chemicals should be applied to the lake in the spring or early summer before this plant produces seeds. It is estimated that the cost to chemically treat the lake is between $7,500 and $12,000 annually. Conversely, mechanical harvesting will cost about $11,250 to $15,000 annually. Both aquatic plant management techniques will need to be implemented at least for five years to gain control of this highly invasive aquatic plant.
8.2. Watershed Best Management Practices
Watershed best management practices (BMPs) that are recommended for the Bradford Lake watershed are listed below (refer to Section 7.2 and Table 8.1):
• Streambank Stabilization • Establishing Riparian Buffers • Performing Stormwater Retrofit Assessments • Preparing Conservation & Nutrient Management Plans
Prepared by Aqua Link, Inc. 103 Little Neshaminy Creek & Bradford Lake Watershed Assessment
By way this assessment, severe streambank erosion occurring at the Fairways Golf and Country Club should be stabilized using bioengineered techniques including live stakes and/or containerized plant materials, coir fiber logs and placed rock. In addition, this segment of Unnamed Tributary A requires a riparian buffer to filter out pollutants transported via surface runoff and to help stabilize highly vulnerable streambanks containing maintained lawn.
A stormwater retrofitting assessment should be performed for the entire Bradford Lake watershed. The municipalities (Warrington, Horsham and Montgomery Townships) should select a qualified consultant to perform this assessment. As part of this assessment, all existing detention basins and other significant stormwater controls should be identified and evaluated for retrofitting. The primary goal of these retrofits is to improve the water quality of stormwater runoff before it is discharged to nearby streams and Bradford Lake. Thereafter, all identified stormwater structures should be prioritized and upgraded when state or federal funding becomes available.
The Conservation District along with the USDA Natural Resources and Conservation Service (NRCS) should identify all active farms throughout the Bradford Lake watershed. Thereafter, the conservation district should develop conservation and nutrient management plans for the most significant farms in order to reduce NPS loadings to nearby streams. Based upon this assessment, farming is very limited in this watershed and it appears that most of the active farms are located within the lower portions of the Little Neshaminy Creek and Unnamed Tributary B subwatersheds.
8.3. Institutional
Recommended institutional practices for the Bradford Lake watershed are (refer to Section 7.3 and Table 8.1):
• Establishing a Watershed Organization • Land Acquisition & Protection • Adopting Ordinances for Protecting Water Quality • Establishing Lower Phosphorus Limits for Point Sources • Environmental Education • Lake & Stream Water Quality Monitoring
It is recommended that a watershed association be created for the Bradford Lake watershed. At a minimum, this association should be comprised of individuals representing the Bucks County Department of Parks and Recreation, local municipalities (Warrington, Horsham and Montgomery Townships), the conservation district and the Heritage Conservancy. This newly created organization can work collectively towards this goal by implementing various key components of the recommended management plan.
The local municipalities and the conservation district with the assistance of the Heritage
Prepared by Aqua Link, Inc. 104 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Conservancy should work on protecting and enhancing more stream buffers by either acquiring these lands or securing conservation easements. The local municipalities should also consider adopting lawn fertilizing and riparian corridor protection ordinances for those lands falling within the watershed boundary. In addition, the local municipalities are encouraged to adopt the stormwater management model ordinance of the updated Act 167 Stormwater Management Plan. It is expected that the Stormwater Management Plan for the Little Neshaminy Creek will be completed sometime next year.
The nutrient effluent concentrations for three wastewater treatment plants located in the Little Neshaminy Creek subwatershed should be significantly lowered to improve lake water quality. PA DEP recently completed a total maximum daily load (TMDL) assessment for the entire Neshaminy Creek Watershed (Section 1.2). Based upon this TMDL assessment, PA DEP will likely require these three point source dischargers to lower their phosphorus effluent concentrations.
The newly formed watershed association should provide educational materials to residents and businesses throughout the Bradford Lake watershed. Educational materials about homeowner best management practices and the results of this assessment should be developed and distributed at the conservation district and municipal government offices. In addition, these educational materials can be bulk mailed to residents and businesses throughout the watershed.
The water quality of Bradford Lake and its tributaries should continue to be monitored on an annual basis. Newly acquired data should be entered into the existing water quality database and analyzed. Water quality trend analysis for the lake and streams will provide a useful tool in evaluating the overall success of any implemented in-lake and watershed restoration measures. All lake and stream samples should be collected and analyzed for the same parameters as described in the PA DEP Quality Assurance – Quality Control Plan for the Warrington (Bradford) Lake and Little Neshaminy Creek Watershed Assessment Project.
8.4. Funding Sources
Many of the recommendations offered in the comprehensive management plan are eligible for state or federal funding. Federal funding may be obtained through the Nonpoint Source (Section 319) Program. State funding may be obtained through the Pennsylvania Department of Environmental Protection’s Growing Greener Grant Program.
Federal funding may be obtained through U.S. Environmental Protection Agency’s Section 319 (Nonpoint Source) Program; National Oceanic and Atmospheric Administration (NOAA) Coastal Zone Management Program; the Delaware Estuary Program; USDA Farm Service Agency’s Conservation Reserve Program (CRP) and Conservation Reserve Enhancement Program (CREP);
Prepared by Aqua Link, Inc. 105 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Table 8.1 Recommended Best Management Practices
Category Recommendations Lead Priority Ranking Section(s) Stakeholder Participating Stakeholders Dredging (Lake Deepening) 1 2 8 7.1.1 In-Lake Aeration (Diffused-Air Aeration System) 2 2 8 7.1.2 Algal Control using Algaecides 2 2 8 7.1.4 Aquatic Plant Control using Herbicides 2 2 8 7.1.5 Aquatic Plant Control via Mechanical Harvesting 2 2 8 7.1.5
Streambank Erosion BSB BS RBH RBW 1 1 3 7.2.1 Watershed Perform Stormwater Retrofit Assessments 2 4 3 7.2.2 Prepare Conservation/Nutrient Management Plans 3 1 6 7.2.3
Establishing a Watershed Association 1 1 All 7.3.1 Institutional Land Acquisition & Protection 2 5 ---- 7.3.2 Ordinances for Protecting Water Quality 3 4 ----l 7.3.3 Lowering Limits for Point Source Discharges 2 7 ---- 7.3.4 Environmental Education 2 3 All 7.3.5 Water Quality Monitoring 1 2 8, 3 7.3.6
Note(s): Recommendations per Category are priority ranked from highest priority (1) to lowest priority (3).
Many of the recommendations will require the professional services of a qualified environmental consultant(s).
Stakeholders: Bucks Co. Conservation District (1) Heritage Conservancy (5) Bucks Co. Dept. Parks & Recreation (2) USDA NRCS (6) Watershed Association (3) PA DEP (7) Municipal Governments (4) Warrington Township (8)
Watershed Best Management Practices:
Exclusionary Fencing (EF) Nutrient Management Plan (NMP) Protected Stream Crossing (PSC) Riparian Buffer – Woody (RBW) Off-Stream Water Source (OSWS) Riparian Buffer – Herbaceous (RBH) Bank Stabilization – Structural (BS) Dirt/Gravel Road Improvement (DGRI) Bank Stabilization – Vegetative Plantings only (BSP) Bank Stabilization – Bioengineered (BSB) Flow Deflecting Structure (FDS)
and USDA Natural Resources Conservation Service’s (NRCS) Environmental Quality Incentives
Prepared by Aqua Link, Inc. 106 Little Neshaminy Creek & Bradford Lake Watershed Assessment
Program (EQIP). Nearly all of the recommendations of the management plan can be funded under the Nonpoint Source program, the Coastal Zone Management Program, the Delaware Estuary Program, while agricultural best management practices and riparian buffers are eligible for funding under the CRP, CREP and EQIP programs.
CREP is an offspring of the USDA Farm Service Agency’s CRP Program. CREP is a voluntary program for agricultural landowners. Unique state and federal partnerships allow landowners to receive incentive payments for installing specific conservation practices. Through the CREP, farmers can receive annual rental payments and cost-share assistance to establish long-term, resource conservation covers on eligible land.
EQIP is funded by the USDA Natural Resources Conservation Service (NRCS). EQIP offers financial and technical help to assist eligible farmers in order to install or implement structural and management practices on eligible agricultural land.
If funding is not available, the watershed stakeholders are strongly encouraged to implement some of the recommendations using their own financial resources. This type of watershed stakeholder commitment is viewed highly by the above agencies and can greatly improve the success of receiving state and federal funding in the future.
Prepared by Aqua Link, Inc. 107 Little Neshaminy Creek & Bradford Lake Watershed Assessment
9. Literature Cited
Alliance for the Chesapeake Bay. 1998. Stream Releaf Forest Buffer Toolkit. Funded by U.S. EPA and PA DEP. Section 319 NPS Program.
Amand, A. S. and K. W. Wagner. 1999. Collection, Identification and Ecology of Freshwater Algae. 19th Annual Symposium for Lake and Reservoir Management. North American Lake Management Society. Madison, WI.
American Public Health Association. 1985. Standard Methods for the Examination of Water and Wastewater (16th Edition). American Public Health Association. Washington, DC.
Aqua Link, Inc. 2000. Quality Assurance – Quality Control Plan for the Little Neshaminy Creek and Warrington (Bradford) Lake Watershed Assessment Project. Prepared for PA DEP.
Aqua Link, Inc. 2002. Stream Monitoring Manual for the Little Neshaminy Creek and Warrington (Bradford) Lake Watershed Assessment Project. Prepared for Bucks Co. Conservation District.
Bland, J.K. 1996. A Gaggle of Geese…or Maybe a Glut. LakeLine Vol. 16 No. 1. North American Lake Management Society. Madison, WI.
Carlson, R. E. 1977. A trophic state index for lakes. Limnol. Oceanogr. 22:361-369.
Carlson, R. E. 1980. International Symposium on Inland Waters and Lake Restoration. EPA 440/5/81/010.
Cooke, G. D., E. B. Welch, S. A. Peterson, and P. R. Newroth. 1993. 2nd Edition. Restoration and Management of Lakes and Reservoirs. CRC Press, Inc. Boca Raton, Florida.
Delaware Riverkeeper. 2001. Stormwater Runoff, Lost Resource or Community Assest? A Guide to Preventing, Capturing and Recovering Stormwater Runoff. Washington Crossing, PA.
Georgia Soil and Water Conservation Commission. Guidelines for Streambank Restoration. Prepared for the U.S. Environmental Protection Agency.
Goldman, C.R. and A.J. Horne. 1983. Limnology. McGraw Hill, Inc. New York, New York.
Prepared by Aqua Link, Inc. 108 Little Neshaminy Creek & Bradford Lake Watershed Assessment
King, D.M., C.C. Bohlen and M.L. Kraus. April 1994. Stream Restoration: The Costs of Engineering and Bio-Engineered Alternatives. University of Maryland, Center for Environmental and Estuarine Studies. Chesapeake Biological Laboratory, Solomons Island, MD. EPA Agreement No. CR-818277-C1.
North American Lake Management Society (NALMS). 2001. Third Edition. Managing Lakes and Reservoirs. Prepared for the U.S. EPA. Office of Water, Assessment and Watershed Protection Division, Washington, D.C.
North Carolina University. River Course: Natural Stream Processes (Fact Sheet No. 1). North Carolina Stream Restoration Institute.
Nurnberg, G. 2001. Eutrophication and Trophic State. Lake Line, Vol. 21, No. 1. North American Lake Management Society (NALMS), Madison, WI.
Pennsylvania Department of Conservation and Natural Resources (PA DCNR). 2005. Physiographic Providence Information obtained at the PA DCNR Website at www.dcnr.state.pa.us/topogeo.
Pennsylvania Department of Environmental Protection. 2003 (revised). Total Maximum Daily Load (TMDL) Assessment for the Neshaminy Creek Watershed in Southeast Pennsylvania. Available at the PA DEP Website at www.depweb.state.pa.us.
Pennsylvania Lake Management Society (PALMS). 2004a. Look Out Pennsylvanians – Water Chestnut is Invading Our State. PALMS Newsletter What’s Wet. Available at the PALMS Website at www.palakes.org.
Pennsylvania Lake Management Society (PALMS). 2004b. PA Lake Management Handbook. Prepared for PA DEP. Available at the PALMS Website at www.palakes.org.
The Pennsylvania State University. Pennsylvania Fish Ponds. The Pennsylvania State University, College of Agriculture, Cooperative Extension Service. University Park, Pennsylvania.
Reckhow, K. H., M. N. Beaulac, and J. T. Simpson. 1980. Modeling phosphorus loading and lake response under uncertainty: A manual and compilation of export coefficients. Report No. EPA-440/5-80-011. U. S. EPA, Washington, D.C.
Schueler, T.R. 1987. Controlling Urban Runoff: A Practical Manual for Planning and Designing Urban BMP’s. Washington Metropolitan Council of Governments. Washington, DC.
Thomman, R.V. and J.A. Mueller. 1987. Principles of Surface Water Quality Modeling and Control. Harper and Row Publishers, Inc. New York, New York.
Prepared by Aqua Link, Inc. 109 Little Neshaminy Creek & Bradford Lake Watershed Assessment
United States Department of Agriculture, Natural Resources and Conservation Service. 1985. Soils Survey of Snyder County, PA.
United States Department of Agriculture, Natural Resources and Conservation Service. 1996. Engineering Field Handbook – Chapter 16: Streambank and Shoreline Protection.
United States Department of Agriculture, Soil Conservation Service. June 1973. Erosion and Sediment Control Plan for Neshaminy Creek Watershed – Site PA-611.
U.S. EPA. 1980. Clean lakes program guidance manual. Report No. EPA-440/5-81-003. U.S. EPA, Washington, D.C.
U.S. EPA. 1990. The Lake and Reservoir Restoration Guidance Manual, Second Edition. Report No. EPA-440/4-90-006. U.S. EPA, Washington, D.C.
U.S. EPA. 1993. Fish and Fisheries Management in Lakes and Reservoirs - Technical Supplement to Lake and Reservoir Restoration Guidance Manual. Report No. EPA-841-R-93-002. U.S. EPA, Washington, D.C.
Wetzel, R. G. 1975. Limnology. W.B. Saunders Company. Philadelphia.
Prepared by Aqua Link, Inc. 110 Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX A
GPS Coordinate Data & GIS Metafile Data
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX B
Land Use & Soils GIS Data
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX C
Glossary of Lake and Watershed Management Terms
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX D
Bathymetric Survey Data
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX E
Lake Water Quality Data Summarized by Aqua Link, Inc.
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX F
Original Laboratory Lake Water Quality Data Reported by Laboratory
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX G
Stream Water Quality & Discharge Data Summarized by Aqua Link, Inc.
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX H
Original Stream Water Quality Data Reported by Laboratory
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX I
Macroinvertebrate Data & Report
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX J
Hydrologic Budget Information & Calculations
Prepared by Aqua Link, Inc. Little Neshaminy Creek & Bradford Lake Watershed Assessment
APPENDIX K
Pollutant Budget & Modeling Calculations
Prepared by Aqua Link, Inc.