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

Objectives Percent Water Rate of Sediment Accumulation Phosphorus Analysis Percent Organic Matter

K-B Core Samples

Extruding 2 cm layers

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

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

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

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

Water content of soil

Organic Matter Content of soil

Phosphorus in the Sediment

Findings: 1. Surprisingly little sediment 2. High Phosphorus content

What can we do? Phosphorus loading is the problem 1.Deal with the phosphorus in the Lake already 2.Manage the source of phosphorus Some measures of removing phosphorus already within the Lake:

Sediment Removal

Mechanical Dredging (Not an option)

Suction dredging Controlled Removal of Sediment –High Volume Suction Pump

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)

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

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

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

Before draining Contact landowner below dam

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.

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.

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.

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

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.

Questions?