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USDA criteria for prime farmland state that the total topsoil plus subsoil depth most equal or exceed <br />40 inches. These criteria were used to modify the soil suitability criteria table (Table 2.04.9 -2) in the <br />DRMS permit. <br />All soil samples during the March 5 sampling event were within suitable ranges for selected analytes <br />and field parameters. The upper two feet of subsoil was investigated, but there was no change <br />observed to the total soil pit depth in any soil pit, suggesting that the soil suitability criteria would be <br />met in the three to four feet of observed subsoil ai all or most sampling locations. <br />Re- sauapling for pH and Eiech Conducrivizy <br />Comments from the DRMS in a letter dated May 28, 2008 revealed that the March 5 subsoil analyses <br />utilized 1.1 extract f'or the soil pH and electrical conductivity (EC), rather than the permit- reeluired <br />paste method for these. analytes. Walsh discussed the situation with DRMS and NRCS personnel and <br />determuned that there is a proportional relationship between 1!1 extract and paste extract EC results. A <br />published formula was applied to the 1:1 EC results, and revealed that up to four sample points may <br />exceed the paste EC criteria of 4.0 (samples 21, 26, 32, and 33). Based on this, the eight sample points <br />that had 1:1 EC higher than 1.2 were resampled and analyzed for paste EC (Table 2). WPC personnel <br />resampled soil at the original sampling points using a 2" hand auger for a total depth of 24 ". A <br />fraction of extracted sample was placed in a zip -loc bag and shipped to Servi -Tech Labs of <br />Hastings, Nebraska. The sampling points were located with a survey -grade GPS to match the March 5 <br />2608 sampling points. The sampled areas had not yet had topsoil placed at the time of sampling. <br />Of the eight samples obtained, two exceeded the topsoil permit criteria of 4. 'These were sample 21 <br />with a paste EC of 4.34 and sample 32 with a paste EC of 7.33. 'The sample 32 location is near a top- <br />soil pile, which may have affected this location. The samplers noted that as many as five attempts <br />were made at sample 32 to get a complete hole due to refusal of the hand auger. This suggests that <br />sample 32 may not be representative of the subsoil io the area. <br />Discussiarx <br />The original soil survey (Intermountain Resource Inventories, hc., 1998) performed laboratory <br />analyses on three soil profiles within the prime farmland unit south of BB Road. Of these three, four <br />individual soil horizons from the approximately 24 -48 inch subsoil interval were analyzed. Paste EC <br />ranged from 0.7 to 3.8, with an average of 1.9_ Percent CaCO3 ranged from 3 to 36 %, with an average <br />of 1?;0_ No cobbles, stones, or boulders were observed in the horizons, and lab analysis of gravel <br />ranged from 9.1 to 31.5' with an average gravel content of 20.7 %. This indicates drat the <br />replacement subsoil has higher average paste EC (3.1 %), lower CsCO3 (2 % -4%), and lower coarse <br />fraction (1 1 .790) than the Original tested subsoil. Sample averages are shown on tables 1 and 2. <br />Walsh discussed the impact of EC on crops with Mr. Dave Dearstyne of the MRCS, who indicated that <br />crops are more sensitive to elevated EC in topsoil than in subsoil. Elevated EC in subsoil can impact <br />established crops but not establishing crops, and established crops are generally more tolerant of <br />elevated EC than establishing crops. Mr. Dearstyue stated that subsoil with a paste EC up to 6 would <br />not be detrimental to grasses or alfalfa. As such, establishing a paste EC criterion of 6 for subsoil in <br />prime farmland for the permit may be appropriate. <br />tiV. <br />Sh <br />Environmet[a7 'k,c.nsts and Engineers, LLC <br />Revised September 2010 (PR 06) Attachment 2.05.4(2)(d) -1 -4 <br />