2013-02-04_REVISION - C1981008 (3)

Home Browse Search

JoEllen Turner Borth Environmental Pollution Consulting, LLC sulfate/gypsum levels. I don't know if the coal dust could contain high enough sulfate concentration to cause this pollution. 970 - 864 -7682 p.18 October 2, 2012 From Ayer and Westcot, 1985: http:// www. fao. org /docrep /003/T0 Gypsum occurs naturally in many soils in arid climates [Colorado is semi -arid] and some soils will contain gypsum in sufficient quantity to affect interpretations of both soil salinity (ECe) and sodicity (exchangeable sodium), and require a correction both to the measured soil salinity (ECe) and to the reported SAR which is frequently used to estimate the soil exchangeable sodium percent (ESP). For example, a gypsiferous soil has a measured ECe of 6 dS /m, a soil salinity which is expected to reduce yields of many salt sensitive crops. Since 2 dSlm of the reported ECe can be attributed to the gypsum, the ECe safely can be discounted by 2 dS /m and the corrected ECe now becomes ECe = 4 dS /m, an amount much less hazardous to sensitive crops. As an example of the problem in interpretation, a strongly gypsiferous soil, but with high salinity, may have an ECe of 12 dStm, of which 2 dS /m can be attributed to the gypsum. If all the other salts are sodium, there should be, in the saturation extract, Na = 100 met and Ca not more than 30 melt, yielding a calculated SAR of 26. Such a. soil, having ECe = 12 dS /m and SAR of the saturation extract equal to 26, is normally classified as a saline- alkali soil which requires extensive reclamation by a massive gypsum application plus extensive leaching before cropping. This is an incorrect interpretation. The soil is moderately saline (ECe = 12 dS /m) but it is not sodic because the gypsum provides a steady supply of calcium. Since the reclaimed soil has to be equal or better than the native soil the substitute soil needs to have a measured EC lower than 2.6 dS /m. 7.3 Organic Matter See my comment above about the problems (e.g., decreased crop yield, less soil aggregation, less water holding capacity, less nutrient retention, etc) related to low organic matter concentrations. In addition, figure 5 in Mr. Dejoia's report clearly shows that the organic matter content is - 300% higher in the undisturbed soil than the stockpiled Lift A. The Dejoia report does not provide evidence to establish that the organic matter content can be returned to — 2.5% within the 10 year reclamation cycle mandated by the regulations. 7.4 Additional Soil Physical and Chemistry Parameters It is clear that the salt levels in the stockpiles are higher than in those found in the native Barx soils, indicating that the stockpiles were contaminated with salt, most likely due to the use of 17 Page PLTF 002491 Undisturbed soil (n=49) Substitute soils (n =6) A lift (n =67) B lift (n =90) Mixed "C' (n =52) Average Gypsum (Ca504 * 2H m eq/100g 3.0 (258 mg /100g (or 025%)) 6.0 (517 mg /100g (or 0.5%)) 5.9 7.1 5.9 JoEllen Turner Borth Environmental Pollution Consulting, LLC sulfate/gypsum levels. I don't know if the coal dust could contain high enough sulfate concentration to cause this pollution. 970 - 864 -7682 p.18 October 2, 2012 From Ayer and Westcot, 1985: http:// www. fao. org /docrep /003/T0 Gypsum occurs naturally in many soils in arid climates [Colorado is semi -arid] and some soils will contain gypsum in sufficient quantity to affect interpretations of both soil salinity (ECe) and sodicity (exchangeable sodium), and require a correction both to the measured soil salinity (ECe) and to the reported SAR which is frequently used to estimate the soil exchangeable sodium percent (ESP). For example, a gypsiferous soil has a measured ECe of 6 dS /m, a soil salinity which is expected to reduce yields of many salt sensitive crops. Since 2 dSlm of the reported ECe can be attributed to the gypsum, the ECe safely can be discounted by 2 dS /m and the corrected ECe now becomes ECe = 4 dS /m, an amount much less hazardous to sensitive crops. As an example of the problem in interpretation, a strongly gypsiferous soil, but with high salinity, may have an ECe of 12 dStm, of which 2 dS /m can be attributed to the gypsum. If all the other salts are sodium, there should be, in the saturation extract, Na = 100 met and Ca not more than 30 melt, yielding a calculated SAR of 26. Such a. soil, having ECe = 12 dS /m and SAR of the saturation extract equal to 26, is normally classified as a saline- alkali soil which requires extensive reclamation by a massive gypsum application plus extensive leaching before cropping. This is an incorrect interpretation. The soil is moderately saline (ECe = 12 dS /m) but it is not sodic because the gypsum provides a steady supply of calcium. Since the reclaimed soil has to be equal or better than the native soil the substitute soil needs to have a measured EC lower than 2.6 dS /m. 7.3 Organic Matter See my comment above about the problems (e.g., decreased crop yield, less soil aggregation, less water holding capacity, less nutrient retention, etc) related to low organic matter concentrations. In addition, figure 5 in Mr. Dejoia's report clearly shows that the organic matter content is - 300% higher in the undisturbed soil than the stockpiled Lift A. The Dejoia report does not provide evidence to establish that the organic matter content can be returned to — 2.5% within the 10 year reclamation cycle mandated by the regulations. 7.4 Additional Soil Physical and Chemistry Parameters It is clear that the salt levels in the stockpiles are higher than in those found in the native Barx soils, indicating that the stockpiles were contaminated with salt, most likely due to the use of 17 Page PLTF 002491