Laserfiche WebLink
The inventory was conducted as a "non-collection" inventory with field analysis/documentation of <br />all artifacts. <br />One historic site, the Hockett Farm granary (5RT519), is an eligible previously recorded <br />historic site. This site is in deteriorating condition and is recommended for BLM/OAHP Level II <br />historic documentation (Athearn 1990:26) prior to any mine related activities occurring nearby. The <br />other three eligible sites and eight need data sites are open prehistoric sites where the potential <br />effects from mine facilities and subsidence are not yet defined. Should any of these sites be <br />threatened by surface facilities, it is recommended that the surface facility be designed to avoid the <br />site, or that a treatment plan be implemented to fully evaluate and, if necessary, address "adverse <br />effects" to the site. <br />Some, if not all of the eligible or need data sites will be in areas where subsidence will occur. <br />To evaluate and address potential adverse effects resulting from subsidence, a pilot testing and <br />condition monitoring program is recommended. Implementation of this program would constitute <br />the first step in the longer term plan to determine effect, and if necessary in developing a treatment <br />plan to address the effects of subsidence. <br />EFFECTIVE ENVIRONMENT <br />This project is located at the north end of Twentymile Park and in the upper valley of <br />tributaries of Sage Creek in the foothills of the Williams Fork Mountains approximately two miles <br />south of the Yampa River in Northwest Colorado. The west margin of the project area lies at the <br />foot of the Williams Fork Mountains. The eastern portion of the survey area is marked by a <br />moderately rugged range of hills formed by the Tow Creek Anticline. In general the area is a high, <br />dissected plateau with rugged mountainous areas, broad river valleys, and rolling upland parks. The <br />area is drained by a dendritic pattern of seasonal drainages. Part of the project area drains into Fish <br />Creek on the south, a tributary of Trout Creek which flows north to the Yampa River. Most of the <br />project area is drained northerly by Scotchman's Gulch and Grassy Creek, both tributaries of Sage <br />Creek. These feed to the Yampa River about 2 miles north of the project area. <br />Quaternary deposition in the project area is largely alluvial with source proveniences in the <br />Flat Tops and Williams Fork Mountains to the west and south. Dark brown silts and sandy silts up <br />to several meters thick have accumulated in the drainage bottoms. Holocene deposits on the tops <br />and upper slopes of the low ridges are thin and consist of light to medium brown silty loams. Well <br />rounded quartzite cobbles and a few cobbles and small boulders of basalt litter the surface on the <br />tops and upper slopes of some ridges. The cobbles of quartzite are likely sources of toolstone for <br />the prehistoric inhabitants in the area. The rugged hilly areas surrounding Twentymile Park contain <br />thick colluvial deposits on the slopes and adjacent to drainage bottoms. Alluvium has accumulated <br />in the drainage bottoms and thin aeolian deposits have accumulated in the hills, especially on the <br />leeward sides of ridges. <br />The project area is situated at the west edge of a structural syncline underlain by Cretaceous <br />age Lewis Shales and sandstones, coal beds and shales of the Williams Fork Formation. The eastern <br />limb of the Tow Creek Anticline borders Twentymile Park on the north and west and small uplifted <br />blocks border it on the east (Tweto 1979). The tops of the high ridges, knobs and hills surrounding <br />2