June 29, 1998 552 



TO: GARY WILLIAMS, Silviculturist , Central Land Office 

 D.J. BAKKEN, Lead Forester, Helena Unit 

 BILL SCHULTZ, Supervisor, State Land MGT. Section 

 GEORGE MATHIEUS, Hydrologist 



FROM: JEFFRY COLLINS, Soil Scientist 



SUBJECT: GLADSTONE TIMBER SALE, Draft Soils Input 

 Sections 23,26,28 and 34, T15N, R5W 



EXISTING ENVIRONMENT Geology & terrain 



The sale area is located on moderate to steep slopes v;ith shallow 

 to deep soils v/eathering from varied bedrocks of primarily 1- 

 imestone, argillites and volcanics (see attached geology map). 

 The purple argillites and silttites of Spokane formation are well 

 fractured and easy to rip where bedrock is encoutered at shallow 

 depth. These rocks make excellant road construction material. 

 Some igneous rocks are uplifted in a band on the northeast corner 

 of section 34 forming some abrupt slopes above Gladstone Creek 



There are no espicially unusual or unique geologic features in 

 the proposed harvest area. Slopes are generally, stable and only a 

 few very localized areas of slope instability were observed wit- 

 hin the project area on section 27 and 28 which can be avoided or 

 mitigated for thru project design. Historic avalanche chutes on 

 the North slopes in the headwaters of Gladstone have lead to some 

 past debris flov;s that are currently stable. 



Primary soils v/ithin proposed harvest units of sections 23 and 26 

 are a complex of Mocmont/Tolex (unit 84F) on 25-60% slopes and a 

 dry map unit phase 63F. Tolex channerly loams occur on convex 

 slopes and ridges and are shallow (<20") with thin clayey 

 subsoils just over the fractured bedrock. Rock outcrops occur on 

 about 10-25% of the soil unit and can limit skid trail location 

 and equipment operations. Tolex soils are very droughty and 

 generally low fertility. Primary concern on both soils is 

 maintaining soil depth and avoiding displacement of the shallow 

 soils which can be mitigated by limiting ground based skidding to 

 slope less than 45%. Erosion can be controlled by installing 

 adequate drainage and grass seeding of main trails where needed. 

 Leaving slash can provide shade to enhance survival of seedlings 

 thru droughty periods . 



Soils in section 34 (proposed units 4,5,6 and access road to unit 

 3) are Trapps-V^arnecke channery loams (984F) forming in limestone 

 on forested mountain sideslopes of 25-60%. Trapps soils are 

 deeper very channery clay loams on concave slopes and swales. 

 Trapps soils are sensitive to rutting on and displacement if 

 operated on when wet. Slopes less than 40% are well suited to 

 tractor operations if skid trails are planned. Cable harvest is 

 required on steeper slopes to avoid sever erosion. 



