Napa County Construction Site Runoff Control Requirements
In an effort to comply with Bay Area Regional Water Quality Control Board regulations, the Napa County Public Works Department proposed new construction site erosion control regulations for approval by the Board of Supervisors.
NVLSA, invited to comment during the preparation of the new regulations, argued that they would be little more than costly window dressing, doing vanishingly little to improve water quality at great expense to property owners.
NVLSA pointed out that Napa County already had erosion control requirements for construction sites and that the new regulations would impose significant new costs on property owners, far in excess of any benefit.
At any one time, construction sites in the unincorporated area occupy between 5 and 50 acres (that is, between 1/1000 of 1% and 1/100 of 1% of the total County land area). According to the Regional Water Quality Control Board’s own figures, carelessly managed construction sites can suffer erosion that contributes up to 100 times as much sediment as from a similar undisturbed area, while stringent controls can reduce this to about 15 times the natural erosion rate until permanent erosion control measures are installed, grass re-established, etc.
NVLSA argued that previously required erosion control measures (Best Management Practices) had already reduced construction site erosion to about 20 times the natural background erosion rate or less, and therefore the gains from the new more stringent regulations would be miniscule.
Doing the math for the worst case, reducing sediment from 20 times down to 15 times the natural rate over 1/100 of 1% of the County land area would reduce the total sediment produced in the county by only 5/100 of 1%, an immeasurably small amount, not worth the cost.
NVLSA estimated the cost to property owners of complying with the new regulations would be on the order of $10,000 to $100,000 per ton of sediment reduction, while the RWQCB, in its TMDL for the Napa River, estimates that the cost of reducing sediment from existing dirt roads should only be about $25 per ton.
Obviously, scarce resources should first be allocated to the most efficient ways of reducing sediment, but despite this blatant breach of cost-effectiveness, the Public Works Department proceeded with the new requirements, agreeing only to make the application process a bit simpler for smaller projects.
The Board of Supervisors approved the new regulations and they are now in effect. (More recently, an article in the San Francisco Chronicle indicates that even prior to development of the TMDL and all the ensuing regulations, the bay had 10 years ago spontaneously recovered from turbidity caused by Gold Rush era sediment, all of which has finally been washed out to sea. The article goes on to say that the new higher water clarity is now a threat to many fish species, including the endangered Delta smelt, which rely on turbidity to hide from predators.)