Laserfiche WebLink
soil (EC 4 -8). It must be noted that this reference is a plant recommendation list for <br />`horticulture /ornamental' sites. This is not an appropriate guide for use when establishing alfalfa <br />for `agronomic' purposes. More importantly, while alfalfa may be able to tolerate an EC of 6 (as <br />currently approved in the permit), the potential impacts to the level of yield that will result, is <br />not discussed or considered in the permit. In short, alfalfa's level of survival tolerance to EC is <br />one consideration; however the negative effect on alfalfa productivity due to elevated degrees of <br />EC, is quite another. Alfalfa productivity is usually classified as being moderately sensitive to <br />EC, along with other crops such as corn. Approving an EC threshold of 6 mmho /cm has <br />considerable potential to negatively affect yields for alfalfa and for corn, a rotational crop used in <br />the past on the Morgan property. While the NRCS did state that "EC up to 6 would not be <br />detrimental to grasses and alfalfa" in permit Attachment 2.05.4(2) (d) -1 (Walsh Report), the <br />acceptance of this statement to singularly determine the EC threshold criteria for prime farmland <br />is not appropriate since the impacts to the level of productivity that could be expected are not <br />addressed in the permit as being a key consideration in this determination. <br />For added perspective, based on the limited sampling data for the Morgan property, the A <br />horizon had an average EC of 1.0 mmhos /cm, the B horizon had an average of 1.8 mmhos /cm, <br />and the C horizon had an average EC of 1.0 mmhos /cm. To help determine the average EC <br />content for the Bench 1 overburden substitute material used in the place of the native B horizon <br />soils not salvaged for Zones 1 and 2, OSM reviewed the data from the 2009 Annual Reclamation <br />Report for the New Horizon Mine. The report includes data for 14 sampled locations on <br />regraded spoil (Bench 1 material). These locations confirm EC values ranging from 2.14 <br />mmhos/cm to 7.39 mmhos/cm. Many of the sampled locations exceed the EC suitability criteria <br />established under the TR -57 revision (4 mmhos/cm) as well as the PR -6 revision (6 mmhos /cm), <br />and both of these EC thresholds are much greater than the EC's present in the undisturbed native <br />soil. It is noteworthy that the suitability table in the Annual Reclamation Report is the same as <br />that approved in the TR -57 revision, except that the table shown in the reclamation report has an <br />EC of 6 mmhos /cm listed as the threshold criteria rather than the 4 mmhos/cm which was the <br />approved standard at the time the reclamation report was submitted to DRMS. Based on the <br />data available, the EC for the Bench 1 material is not within the chemical range of the growth <br />medium soils that existed prior to mining, and therefore has not been demonstrated to be a <br />suitable soil substitute on the Morgan Property. The NRCS's published guidelines for handling <br />prime farmland soils, include the following guidance regarding the use of soil substitutes for <br />prime farmland soils: <br />Specifications for Soil Removal <br />(b) Substitution of any material for naturally occurring prime farmland topsoil should be <br />approved by the RA, in consultation with the MRCS, only when the substitute material <br />will have a demonstrated productivity that is higher than the original topsoil. <br />Substitution of any material, or mixing of the existing layers, for a naturally occurring <br />9 Federal Register /Vol. 64, No. 124 /Tuesday, June 29, 1999. <br />16 <br />