LOCATION HELEMANO HIEstablished Series
TAXONOMIC CLASS: Very-fine, kaolinitic, isohyperthermic Rhodic Eutrustox
TYPICAL PEDON: Helemano silty clay - pasture. (Colors are for moist soils unless otherwise noted. All textures are "apparent field textures.")
Ap--0 to 10 inches; dark brown (2.5YR 3/4) dry and moist silty clay; moderate very fine and fine granular structure; hard, firm, sticky and plastic; many roots; many very fine interstitial pores; neutral (pH 6.6); abrupt smooth boundary. (6 to 10 inches thick)
Bo1--10 to 30 inches; dark reddish brown (2.5YR 3/4) paragravelly silty clay, dark red (2.5YR 3/6) dry; moderate fine subangular blocky structure; hard, friable, sticky and plastic; common roots; common tubular pores; 15 to 25 percent soft strongly weathered pebbles and stones; neutral (pH 6.6); clear smooth boundary. (12 to 20 inches thick)
Bo2--30 to 41 inches; dark reddish brown (2.5YR 3/4) dry and moist paragravelly silty clay; moderate fine and medium subangular blocky structure; hard, friable, sticky and plastic; few fine roots; common fine tubular pores; 15 to 25 percent soft strongly weathered pebbles and stones; neutral (pH 6.6); gradual smooth boundary. (8 to 12 inches thick)
Bo3--41 to 60 inches; dark red (10 R 3/6) very paragravelly silty clay red (10R 4/6) dry; moderate fine and very fine subangular blocky structure; hard, friable, sticky and plastic; few very fine roots; common fine and medium tubular pores; 25 to 50 percent soft strongly weathered pebbles and stones; slightly acid (pH 6.5). (10 to 20 inches thick)
TYPE LOCATION: Island of Oahu, Honolulu County, Hawaii; near Waipio Acres; from the intersection of Kamehameha Highway and the road to Kipapa School, proceed south on the Kam Highway 0.2 mile, turn northeast on road toward the Koolau Range. Proceed 1.35 miles, turn south toward Kipapa Gulch 0.7 mile; site is 50 feet north of the road; lat. 21 degrees 27 minutes 47 seconds N. and long. 157 degrees 59 minutes 59 seconds W. (Old Hawaiian Datum).
RANGE IN CHARACTERISTICS: Depth to highly weathered basalt is variable but ranges from 25 to more than 60 inches. Near the toe of slopes the solum is normally over 60 inches thick and commonly stony throughout.
The A horizon has hue of 2.5YR or 5YR. Effervescence in the A horizon ranges from none to slight.
The B horizon has hue of 2.5YR or 10R, value of 2 through 4, and chroma of 2 through 6 when moist.
COMPETING SERIES: (This needs updating.) These are the Kahana, Lahaina, Niu, and Wailuku series. Kahana soils have strong structure in the B horizon and effervescence with hydrogen peroxide throughout. Niu soils have weak structure in the A horizon and upper B horizon and effervesce with hydrogen peroxide in the control section. Wailuku soils have 5YR hue in the B horizon and effervescence with hydrogen peroxide throughout.
GEOGRAPHIC SETTING: Helemano soils are on sides of V-shaped gulches at elevations of 500 to 1,200 feet. Slopes range from 30 to 90 percent. The slopes are convex and are from 100 to 500 feet in length. These soils formed in colluvium and alluvium weathered from basic igneous material of the Koolau and Waianae Ranges. Mean annual rainfall is 30 to 60 inches. The mean annual temperature is about 72 degrees F.; average January temperature is about 69 degrees F.; and average July temperature is about 75 degrees F. Annual pan evaporation is 40 to 60 inches, and averages 50.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Leilehua, Manana, Molokai, Wahiawa soils and the competing Lahaina soils. Leilehua soils have an argillic horizon and are extremely acid throughout the solum. Manana soils have a thin panlike layer at depths of 15 to 50 inches and have an argillic horizon. Molokai soils have an aridic moisture regime and have weak structure in the A horizon. Wahiawa soils effervesce with hydrogen peroxide throughout the profile and have thin patchy clay films in the lower part of the Bo horizon.
DRAINAGE AND PERMEABILITY: Well drained; rapid or very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Pasture, woodland and wildlife. Natural vegetation is mainly of guava, Java plum, christmasberry, koa haole, Formosa koa, and bermudagrass.
DISTRIBUTION AND EXTENT: On Oahu in deep gulches and drainageways in the Wahiawa basin and foothills of the Koolau and Waianae Mountains. This series is of moderate extent with an area of about 28,000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Island of Oahu, Honolulu County, Hawaii, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon from the surface to 10 inches (Ap horizon).
FCC Classification: Cdik.
Edit Log: Horizon designations updated;
8/00 SN. Classification changed from Clayey, kaolinitic, isohyperthermic Tropeptic Haplustox due to changes in Taxonomy.