I do not like to make assumptions about the load bearing capacity, without the aid of soil borings in the immediate vicinity. That said, if the pile driver is using a drop hammer, the load bearing capacity at the time of driving can be estimated when the pile hits refusal. For example, a drop hammer exerting 40,000 ft/lbs could give a capacity of 50,000 lbs. and higher when refusal is reached, but for the purposes of the builder, I would use the energy of the hammer as the capacity at refusal. Depending on the soil, this number may increase dramatically as the soil sets around the pile and increases skin friction (1.5 times to more than 2 times). For example, a 12" diameter pile ordinarily has a capacity of 50,000 to 80,000 lbs. at the time of driving when driven to refusal - but this would be in dense clay and not silt or organic material.