From the GMA Techline
Subject: Cost estimate data In 2006, we completed a 30-acre pond (depth, approximately 30 ft.), and now we want to estimate the cost for a pond of similar size for a construction start in November 2007.
For estimating purposes, are you able to suggest a percentage increase that we should use in estimating material costs for the geosynthetic liner?
Reply: After the hurricanes struck the U.S. Gulf Coast [in August 2005], resin prices jumped significantly … thus, the price of geomembranes rose accordingly (about 20-25%). Since then, they have slid back to the point where I would estimate a 10-20% increase.
Rather than using these numbers, however, I would suggest calling the vendor of your 2006 material and getting a better unit cost. Most manufacturers are cooperative in this regard.