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SECTION 2 FORMER HOGGING PLANT INTERIM REMEDIAL ACTION than calcitic lime, calcium from gypsum penetrates soil farther than calcitic lime, minimizing the impacts of incomplete mixing of amendments into soil.Additionally,gypsum is a sulfate source.Sulfate can form a chemical complex with excess soluble aluminum,which is less toxic to plants than the uncomplexed aluminum ion.Over- application of gypsum is not expected to negatively affect tree growth. Common initial application rates for gypsum range from 2 to 4.5 tons per acre. Because of the anticipated positive effects of using gypsum as an amendment and the relatively low impact of over-application,a rate of 4 tons per acre,or 3 tons for the treatment area,will be used. 2.1.3 Carbon Source Adding a source of organic carbon,such as compost or mulch,could promote denitrification and modify the soil structure. In 1998,a pilot test using sugar and anola meal pellets as carbon sources was performed at the site to test in situ soil denitrification (CH2M HILL, 1998).The results of the pilot test were considered in the Feasibility Study Report(CH2M HILL, 2000b), in which it was concluded that there would be challenges for effective implementation of in situ denitrification.The challenges and the rationale for not selecting in situ denitrification as the soil remedy for the site included dd%n*y m maintaining saturated conditions.Saturated conditions are required to create conditions conducive to in situ denitrification. For this interim remedial action,the bent of amending the soil with organic carbon would be relatively minor. Therefore,the treatment area soil will not be awrndcd with organic carbon. 2.2 Field Procedures The treatment area is shown on Figure erim remedial action,existing trees and stumps in the treatment area will be removed,arnem. - oplied to the surface,the treatment area will be slip plowed and then graded, and new trees "Orr w,_ , The purpose of this approach is to amend and break up the soil to create conditions more condw.,%w 9v ve -mediation.The following subsections describe the details of implementing this interim remedial wal 2.2.1 Utility Clearance and Awn Underground Service Alert will be notifid at bast 4 burs before intrusive activities begin to mark subsurface utilities in the treatment area. In additWw a pnoaM utraty locator will perform utility locating in the treatment area. No permits are required for the soil amealawat and trete replanting described in this work plan. 2.2.2 Clearing and Grubbing All trees and stumps in the treatment area wA be removed so that the area is nearly free of obstructions to soil amendment and slip plowing(other than 1Monnonng well KP-3 and any utilities).Additional trees outside the treatment area might also need to be removed for epuipment to access the treatment area.The number of trees removed for equipment access will be mhnxnced to the extent practicable. 2.2.3 Slip Plowing Calcitic lime and gypsum will be applied to the ground surface at rates of 5 tons per acre and 4 tons per acre, respectively, as discussed in Section 2.1.After lime and gypsum have been spread on the ground surface, the treatment area will be slip plowed to a depth of approximately 6 feet bgs to break up the soil(including the clay layer observed during the 2012 investigation)and incorporate the amendments into the soil.Slip plowing is commonly used in the agriculture industry to break up deep soil layers that limit rooting or water movement.Slip plowing will be performed in two directions(north-south and east-west), and rows will be spaced approximately 2 feet apart.A small area around the perimeter of the treatment area will not be slip plowed to 6 feet bgs because of the operating constraints of the slip plow; a small amount of space is needed at the beginning of each row for the slip plow to advance to operating depth. Monitoring Well KP-3,which is in the treatment area,will be marked with traffic cones,or an equivalent marker, to minimize the potential for damage during slip plowing. If Monitoring Well KP-3 is damaged during 2-2 RDD/131490001(CAH5152.DOCX) E5052913233837