Did you get the water tested? I am not sure of how you go from soil to water for conversion purposes but the water will generally reflect the soil. Having said that read below. You appear to have high calcium so see the [ ] part below. Here is the fact sheet link.

http://srac.tamu.edu/index.cfm?catid=25
see:
SRAC 460 Control of Clay Turbidity in Ponds


Although not nearly as effective

as alum, gypsum also can be used

to control turbidity but without

the loss of alkalinity. Gypsum

must be added to achieve a concentration

of 100 to 300 mg/L for

effective turbidity control. For

most ponds, gypsum application

rates will range from about 1,000

to 2,000 pounds per acre (Fig. 4).

[ In hard-water ponds (calcium

hardness greater than 50 mg/L),

the water is nearly saturated with

calcium and gypsum may be ineffective.

In that situation, alum will

be the only effective coagulant.]

All the coagulants mentioned can

remove phosphorus from water.

As phosphorus is an essential

plant nutrient, it may be necessary

to fertilize the pond after treating

it for turbidity.