| Slide 1 |
| Presentation Overview |
| Introduction | |
| Water Quality Analysis | |
| Land Use Analysis | |
| - Intermission - | |
| GIS Analysis and Models | |
| Future Predictions | |
| Remediation Measures | |
| Recommendations |
| Slide 3 |
| Slide 4 |
| Bathymetry Map |
| Important for identifying sub-basins and water sampling sites, | |
| computing lake volume, and predicting the occurrence of | |
| organisms in Webber Pond |
| Bathymetry Map |
| Slide 7 |
| Slide 8 |
| Slide 9 |
| Slide 10 |
| Slide 11 |
| Slide 12 |
| Slide 13 |
| Slide 14 |
| Slide 15 |
| GIS, Phosphorus Model, and Future Predictions |
| Erosion Potential Model |
| Inputs | |
| Soil Map | |
| Land Use Map | |
| Slope Map | |
| Weighted Overlay | |
| Soil Map |
| K values represent a soilÕs erodibility | |
| K values were reclassified to range from 1 to 9 | |
| 9 represents the most erodible soil types and 1 represents the least | |
| Land Use Map |
| Erosion Risk Values | |
| Mature Forest - 1 | |
| Wetlands - 1 | |
| Transitional Forest - 3 | |
| Reverting Land - 4 | |
| Pasture - 7 | |
| Golf Course - 7 | |
| Cleared Residential | |
| Land - 8 | |
| Cleared Land - 9 | |
| Crop Land - 9 | |
| Commercial / | |
| Municipal - 9 | |
| Roads - 9 |
| Slope Map |
| Weighted Overlay |
| Combines 1-9 erosion risk value for each input | |
| Factors in the percent importance of each input for the model | |
| Slope - 50% Land Use - 25% | |
| Soil Type - 25% | |
| Erosion Model Inputs |
| Final Erosion Potential Map |
| Water Budget |
| Calculation |
| Slide 26 |
| Slide 27 |
| Creating the Model |
| Area of input categories | |
| Export coefficients | |
| Surface area of lake | |
| Annual total water inflow | |
| Number of capita years | |
| - Lower for seasonal residences | |
| - Higher for year-round residences |
| Examples |
| Calculated Phosphorus Concentrations |
| Slide 31 |
| Historical Population Trends and Future Population Predictions |
| 1950 - 2000: 1.26% annual pop. growth | |
| 1990 - 2000: 10% growth in population | |
| Webber Pond watershed population growing at about same rate as Vassalboro population | |
| Projected growth: 0.7% annual increase for next 25 years | |
| Projected 2022 population: 4,698 | |
| Future Development Predictions for Webber Pond Watershed |
| Predicted Land Use Changes with Increase in Residential Land in 2022 |
| Mature Forest 602.54 acre increase | |
| Shoreline Residential 10.50 acre increase | |
| Non-Shoreline Residential 212.00 acre increase | |
| Transitional Forest 610.60 acre decrease | |
| Reverting Land 52.19 acre decrease | |
| Agriculture 145.57 acre decrease | |
| Cleared Land 10.00 acre decrease |
| Phosphorus Loading Model Predictions |
| Increased Residential Land | |
| 2002 phosphorus concentration: 23.35 ppb | |
| 2022 phosphorus concentration estimate: 23.52 ppb | |
| 0.17 ppb increase | |
| No Increase in Residential Land | |
| 2002 phosphorus concentration: 23.35 ppb | |
| 2022 phosphorus concentration estimate: 22.82 ppb | |
| 0.53 ppb decrease |
| Remediation Techniques and Recommendations |
| Melanie Newton |
| Remediation |
| Problem- Reducing phosphorus loading | |||
| Direct Control - Decreasing amount of phosphorus that enters the watershed | |||
| Point source diversion | |||
| Erosion control | |||
| Nutrient Control - Reducing sediment release of phosphorus | |||
| Water Drawdown | |||
| Phosphorus inactivation | |||
| Hypolimnetic withdrawal | |||
| Point Source Diversion |
| Diverting tributaries or point sources high in nutrients | |
| Nutrient Interception |
| Erosion carries sediment, nutrients, pesticides, and pathogens into the watershed | |||
| Methods to control erosion: | |||
| Maintenance of roads | |||
| Control of shoreline erosion | |||
| Construction of vegetated buffers | |||
| Agriculture BMPs | |||
| Ideal Road |
| Constructed of proper | ||
| materials | ||
| Graded and Crowned | ||
| Diversions, turnouts, | ||
| buffers, and ditches | ||
| Road Surface |
| Larger gravel for base, finer gravel on top | |
| A crown should be 1/4 inch high for each foot of road width | |
| Grading uses a steel blade to level the soil material on the roadÕs surface. | |
| Grading should be done often and crowning should be done annually | |
| Ditches |
| Flat bottom and surface | |
| Gradually graded sides | |
| Trapezoidal or parabolic in | |
| cross-section | |
| Stone-lined or vegetated | |
| Sufficiently wide and deep |
| Culverts |
| Convey water under road surface | |
| Discharge water into ditch or vegetated buffer area | |
| Should be adequately sized and have a 2% slope | |
| At least a foot of soil covering | |
| Vegetated Buffers |
| Remove sediments, nutrients from runoff water | ||
| Forests: | ||
| - Uneven surfaces obstruct flow | ||
| - Roots promote absorption | ||
| Seeding and mulching is beneficial where forests have been removed | ||
| Shoreline Erosion |
| 914 m (6%) are high risk | |||
| shoreline | |||
| Several residents have | |||
| taken action by constructing | |||
| Concrete walls | |||
| Log crib | |||
| Riprap | |||
| Riprap |
| Prevents erosion and allows nutrient-rich runoff to be absorbed by shoreline first. | |
| Grade of slope should be reduced 2:1 | |
| Base of bank should be stabilized with gravel blanket and rock riprap | |
| Slope covered by vegetation |
| Water Drawdowns |
| Purpose: | ||
| Remove water high in nutrients | ||
| Kills some nuisance macrophytes | ||
| Benefits: | ||
| Low cost | ||
| Facilitate other remediation techniques | ||
| May increase spawning areas for bass | ||
| Drawbacks: | ||
| Could facilitate growth of some macrophytes | ||
| Interferes with recreational activities | ||
| Could kill planktivorous fish | ||
| Removes only water from surface | ||
| DEP Drawdown Management Plan |
| Presented in 1991 to Webber Pond Association | ||
| Water Quality Manager, Dam Manager | ||
| Water Level Coordinator | ||
| Bi-weekly transparency readings | ||
| Algal bloom before July, no drawdown | ||
| Algal bloom late August, drawdown | ||
| as soon as possible | ||
| Drawdown 1.5 ft. below spillway by | ||
| Labor Day | ||
| Drawdown no later then September 3rd | ||
| Compromise |
| Residents | |
| Recreational use of Webber Pond | |
| Swimming, Boating, Fishing, until Labor Day | |
| Natanis Golf Course | |
| Draws water from Webber Pond to | |
| maintain holes | |
| Best Biological Practice | |
| Drawdown occur as soon as possible after algal | |
| bloom, when nutrient levels are highest |
| Phosphorus Inactivation Process |
| Al2(SO4)3 and sodium aluminate added to water, bind with phosphorus forming AlPO4 | |
| Falls as floc onto sediment | |
| Aluminum best in anaerobic conditions | |
| pH must be between 6-8. pH below 6 forms toxic Al(III) |
| Phosphorus Inactivation as Remediation |
| Purpose | |
| To reduce internal phosphorus | |
| Benefits | |
| Very effective | |
| long-term benefits | |
| Drawbacks | |
| Costly. Estimates for Webber Pond | |
| from $180,000-$890,000 | |
| Potentially toxic | |
| Increase in macrophyte growth |
| Hypolimnetic Withdrawal |
| Purpose | |
| To remove nutrient-rich, deoxygenated | |
| water from hypolimnion | |
| Benefits | |
| Cheap | |
| Effective reduce from | |
| 200 mg/L to 91 mg/L | |
| Drawbacks | |
| Where will water go? |
| Possible Collaboration with Natanis Golf Course |
| Golf Course uses approximately 1 million gallons of water from Webber Pond each year | |
| If golf course could extend pipe deeper than 6 m into hypolimnion, it could drain nutrient-rich water | |
| Golf course could use this in irrigation and possible fertilization | |
| Remove nutrients from Webber Pond | |
| Recommendations |
| The primary problem at Webber Pond is cultural eutrophication | ||
| Nutrient run-off from agriculture, roads, residential, and commercial land uses | ||
| Historical cultural eutrophication created the problem in high internal phosphorus recycling levels | ||
| Remediation must address both of these issues | ||
| Monitoring Suggestions |
| Bi-weekly transparency readings from | ||
| May through August | ||
| Test surface and epicore samples for phosphorus yearly | ||
| DEP Site (Site 1) | ||
| Green Valley Campground (Site 6), | ||
| Natanis Golf Course (Site 9), | ||
| Dam (Site 10). | ||
| Transparency and Dissolved Oxygen profile | ||
| at Site 1 monthly May-September | ||
| Regulatory Measures |
| Agriculture | |
| Increase use of BMPs in agriculture | |
| Better monitoring of these farms | |
| Forestry | |
| Restrict future timber harvesting | |
| If harvesting occurs follow a BMP | |
| Roads | |
| Conduct road surveys frequently | |
| to identify trouble spots | |
| Repair Trouble Spots | |
| Residential Measures |
| Encourage addition and enhancement of vegetated buffers and riprap | |
| Encourage road improvements and maintenance by residents | |
| Limit use of lawn fertilizers | |
| Reduce shoreline alteration | |
| Nutrient Control Measures |
| Continue the yearly drawdown, investigate the possibility of drawing water down from hypolimnion not just surface | |
| Investigate the possibility of using nutrient-rich hypolimnetic water in irrigating the Natanis golf course | |
| Investigate the possibility of phosphorus inactivation |
| Educational Measures |
| Encourage the availability of this report to the general public | |
| Work closely with the China Region Lake Alliance | |
| Develop and distribute pamphlets to homeowners (road repair, riprap, vegetated buffers, detergents, and water level drawdown) | |
| Involve local schools in monitoring Webber Pond |
| Acknowledgements |
| Peter Abello Kelly Karter | |
| Roy Bouchard Jim Lucas | |
| Bob & Julie Brown Kevin Michaud | |
| Russell Cole Judy Moody | |
| Gene Field Peter Mosier | |
| Dale Finesth Rebecca Manthey | |
| David Firmage Edward Noel | |
| Betsy Fitzgerald Frank Richards | |
| Nate Gray Bruce Rueger | |
| David Halliwell Dan Tierney | |
| Vassalboro Town Office Staff | |
| Maine Department of Environmental Protection Staff | |
| Maine Department of Inland Fisheries and Wildlife Staff | |
| Maine Soil and Water Conservation Staff | |
| Green Valley Campground |
| Questions |