SBCT Final EIS - Govsupport.us

Chapter 3 ⎯ Affected EnvironmentPreliminary Army Training and Testing Area Carrying Capacity (ATTACC) modeling results reportedin 2004 Transformation FEIS indicated that land condition at KTA is adversely affected bycurrent training activities and that soil loss exceeds sustainable rates (USAG-HI 2004).Kawailoa Training Area. The ROI for geologic resources within KLOA is contiguous with the ROIof the Drum Road portion of the alternative; therefore, the discussion on the Drum Road route includesthe portion of KLOA that would be affected by Alternative A for this EIS. The soils within thecorridor along Drum Road, which runs through KLOA, between KTA and Helemano Military Reservation(HMR), are summarized below.Drum Road follows narrow ridges between watersheds along most of its route, occasionally crossingsteep gulches to cross streams. The road is paved from Kamehameha Highway to just east of MountKawela. A project is underway to improve the road, including constructing tunnels in areas wheresharp curves on steep slopes are otherwise unavoidable, using bridges and viaducts to widen theroadway in narrow areas, installing box culverts designed to accommodate a 10-year storm, and realigningthe road to provide a maximum 9 percent grade (slope). The improved road would generallyfollow the existing alignment. The road surface would be gravel, with compacted gravel shoulders. Insome areas, it would be paved with asphalt to protect from erosion and formation of ruts (USAG-HI2004).Along the 6-mile segment where the road follows the northern boundary of KLOA, the road passesinitially over a small area of Paumalu silty clay, and then crosses quickly into Paumalu-Badland complex.Above an elevation of about 1,000 feet amsl, it is in Kapaa silty clay on 40 to 100 percent slopesand Helemano silty clay in many ridge top areas, steep sides of V-shaped gulches, and rock outcrops(USAG-HI 2004). The Paumalu series soils are well-drained, gently rolling, silty clays developed inold alluvium and colluvium, with runoff and erosion hazard increasing as slope increases. The Paumalu-Badlandcomplex occurs on 10 to 70 percent slopes and consists of 20 to 60 percent Badland.The erosion hazard is very severe (USAG-HI 2004). As described in the section on KTA, Kapaa siltyclay soils exhibit very rapid runoff and very severe erosion potential, with most of the surface soilhaving been removed by erosion. As described in the section on SBMP, Helemano silty clays aremoderately rapidly permeable, with rapid runoff and very severe erosion potential.The road continues south, following closely along the boundary of KLOA toward Puukapu, crossingHelemano silty clay soil to rock land, both described previously as having severe runoff and erosionhazard. After crossing the Kaiwikoele Stream, the road passes over some broader ridges underlain byPaaloa silty clay and Paaloa clay, used primarily for pasture and formerly for sugarcane. The Paaloasoils are well-drained, formed on narrow upland areas bounded by steep, smooth-sloped gulches, andexhibit moderately rapid permeability, slow to medium runoff, and slight to moderate erosion potential(USAG-HI 2004).As the road continues south, it passes again across rock land, alternating with Helemano silty clay on30 to 90 percent slopes. It also passes over a few narrow ridges underlain by Leilehua silty clay on 2to 6 percent slopes. The Leilehua soil is similar to the Paaloa soils in its occurrence on narrow ridgesbounded by steep gulches, but it is developed on a more gravelly substratum. Runoff is slow, permeabilityis moderately rapid, and the erosion hazard is slight.As the road continues south, it bends dramatically to avoid deep gulches and cultivated farmlands. Asa result, the road follows along the rim of the gulches, crossing over steep slopes underlain by Helemanosilty clay or rock land, alternating with gentler slopes on ridges underlain by Leilehua silty clay.It follows a course west along the north ridge of Opaeula Stream and dips down from the rim elevationof about 1,200 feet amsl into the stream gulch to cross the stream at an elevation of aboutFebruary 2008 3–12 2/25th SBCT Final EIS