Best Hills Ranch Lake Sediment Investigation

1. Best Hills Ranch Lake Sediment Investigation Danelle Russell Josh Peterson Chris Foster Sarah Richardson

2. Objectives • Percent Water • Rate of Sediment Accumulation • Phosphorus Analysis • Percent Organic Matter

4. K-B Core Samples

5. Extruding2 cm layers

6. Percent of Water in Sediment • An estimate for amount of sediment to remove by suction dredging • Weigh 1 tsp. wet sediment from each layer • Dry the sediments at 50ºC for 24 hrs in a oven • Reweigh each dried sample • (wet weight - dried weight) = water content

7. Sediment Accumulation • 2 cm / 12 years = 0.167 cm / year • (300 cm = deepest point in pond) 300 cm / 0.167 = 1796 years for pond to fill in!

8. Phosphorus Analysis • P is often a limiting nutrient in aquatic systems (Shindler, 1977) • Plants that root in sediment primarily uptake P from the sediments (Bristow, 1975; Gabrielson et al., 2984) • Combined K persulphate, deionized water, soil, pressure, and heat (autoclaved) to detached P from the sediment and put into solution. • Measured P from each layer of solution using a light spectrophotometer

9. Organic Matter in Sediment • OM includes: plants, algae, fungi • Primary source of nutrients for aquatic vegetation (Wetzel, 2001). • Use dry sediment • muffle furnace at 550ºC for 3-4 hours Dry weight – ash weight = organic matter

10. Water content of soil

11. Organic Matter Content of soil

12. Phosphorus in the Sediment

13. Findings: Surprisingly little sediment High Phosphorus content

14. What can we do? • Phosphorus loading is the problem • Deal with the phosphorus in the Lake already • Manage the source of phosphorus Some measures of removing phosphorus already within the Lake:

15. Sediment Removal

16. Mechanical Dredging • (Not an option)

17. Suction dredging • Controlled Removal of Sediment • High Volume Suction Pump

18. De-water the lake Drain during summer months Use 3” portable gas pumps (2) 16 days to de-water lake $800 to rent 2 pumps (Sun Rentals)

19. Sweep After sediment dries sweep to one end $50 per day for rental (A-Z Rentals)

20. Remove Sediment • Haul sediment away • Cost depends on amount of sediment • Also depends on disposal • Possibly find someone to use sediment • 300 m³ of sediment if top 2 cm are removed. • Dried sediment should be less due to water content

21. Issues • Waterless lake for an amount of time • Weather • Depends on how much rain • Well output • Unknown if well can refill lake alone

22. Before draining • Contact landowner below dam

23. Barley Straw • Use after sediment removal. • Considered a more natural, organic approach. • Used to decrease the algal growth in water. • Chemical properties of decomposing barley are thought to inhibit the growth of algae. • May act as a carbon source for microbes. An increase of microbes causes phosphorus to be limited for algal growth.

24. Barley Straw • Barley straw must be installed in March or April, before algal growth occurs. • Takes approximately 6 weeks to decompose. • Barley stuffed loosely into mesh bags. • Anchored in 2 to 5 feet of water with rocks in bottom of bags. • Suspended in water column with floats in top of bags.

25. Barley Straw • Distribution of straw must be uniform across the lake. • Good for about 6 months and is taken out of the system in the fall. • Taking straw out is crucial so as not to add nutrients to the lake.

26. Amount and Price • It takes about 225 lbs of straw per acre. • 3.7 acres x 225 lbs = 833 lbs • Average price for ½ ton of barley straw is $22.00

27. Pros and Cons • Pros • Inexpensive • Can get high school or college groups to install/remove it. • Reduction of algae without chemicals. • Cons • Could promote macrophyte growth. • Labor intensive. • Disposal of used straw messy.

28. Questions?