Statistical method?

MOSSAD

The following is a protocal which the Forest Service demands must be followed in order to assess the suitability of a site for afforestation. Four water samples must be taken between Februrary and May, at least a week apart. If the CaCo3 measures> 15mg/l, afforestation will be grant aided. If any one test falls below this, afforestation will in almost all cases be refused.

This sensitivity of the water to acidic inputs is determined by the measurement of alkalinity.
Sampling and analysis shall be carried out on a minimum of four occasions at intervals not greater
than four weeks in the period February to May inclusive. The analysis will be carried out by a
laboratory, independent of the applicant, and currently participating in relevant national or
international intercomparison exercises. Samples and measurements should be taken from all
watercourses shown on Ordnance Survey 6" Maps within the area of the proposed afforestation.
Samples should be taken as indicated in the procedure on page 137.
Alkalinity should be measured using the Gran Titration Method.
The minimum acid-sensitivity measured in the above manner will determine the overall sensitivity
of the site.
There will be no afforestation approved in areas where the minimum alkalinity of the run-off water,
measured in the above manner, is <8 mg CaCO3 l-1.
Where the minimum alkalinity of the run-off water, measured in the above manner, is in the range
8 – 15 mg CaCO3 l-1, full, partial or no afforestation may be allowed following discussion and
agreement between the Environmental Protection Agency, the Forest Service of the Department of
the Marine and Natural Resources and the Regional Fisheries Board.
Afforestation will be allowed in areas where the minimum alkalinity of the run-off water, measured

in the above manner, is >15 mg CaCO3 l-1.

Can this protocol be considered a correct interpretation of what might be happening on the site? I know of one site where three of the tests were, 20, 25 and 23 mg CaCO3/l and one was 10mg. The nsite was refused based on the low figure. Subesquent testing the next year gave four tests well above 15mg/l, but the site was refused based on the first four tests.
Am I alone in thinking that this is a misuse/abuse of the sampling process?

LeixlipRed

Hmm, you'd need to take more samples to know if the small values are statistically significant or not. Seems like a kind of thrown together process. I don't know anything about water alkalinity though so there could be some valid reason for exclusion based on one low reading.

MOSSAD

Ok will do some more checking on the alkalinity stuff, thanks.

conor86

MOSSAD wrote: »

Ok will do some more checking on the alkalinity stuff, thanks.

I am currently preparers to carry out a water quality assessment on a river.
As far as I known alkalinity is water with a ph above seven
CaCO3 is lime which increase the ph., rain water has a low ph and we get a lot of rain between February and May,, I'm only guessing
What document are you pulling this form?