Estimating the Number of Trees

Per-Acre Method

Pay is relatively easy to determine when pay is based on acreage planted. Pay will equal the bid price per acre times acreage completed less deductions for poor quality, wasted trees, and so forth. The contractor may dispute the number of acres within the unit, requiring the Government to retraverse the unit. The contract may state the range of trees that must be planted per acre or the total number of trees that are expected to be planted. The Government may need to negotiate a price adjustment if the contract was incorrect.

Actual Tree Quantity Method

When the pay is based on numbers of trees planted, there is more room for dispute. You cannot assume that all trees that were issued to the contractor and not returned to the Government were actually planted. A statistical approach supplements the inspection plots with additional plots where you count only the number of trees per plot. The statistical confidence of the estimated number of trees planted depends on the variability of the number of trees planted in different plots and other factors of the plots.

The most defensible method of estimation is to determine whether the number of trees issued is within the 95 percent confidence of the statistical range of the number of trees counted in plots. If so, payment is based on the number of trees issued. If not, the COR should be checking a larger sample of planted trees or looking for stashed or lost trees. In any case, the COR should be comfortable that the Government is paying for services that actually were provided.