The following is a map unit description from the "Soil Survey of Barnstable County, Massachusetts (Fletcher, 1993)"
PxD-Plymouth-Barnstable complex, hilly,
extremely bouldery. These hilly and steep, very deep, excessively drained and well drained soils are on hills and ridges on moraines. Stones and boulders cover 3 to 15 percent of the surface. Slopes range from 15 to 35 percent. The soils make up about 3.4 percent (8,688 acres) of the survey area. They are mapped mainly in the Plymouth-Barnstable-Nantucket general soil map unit. Areas are irregular in shape and generally range from 20 to 700 acres in size. They are about 55 percent Plymouth soil, 20 percent Barnstable soil, and 25 percent other soils. The soils occur as areas so intricately mixed or so small that separating them in mapping is not practical.
Typically, the surface of the Plymouth soil is covered with an organic layer. This layer is about 1 inch of loose, undecomposed pine needles, leaves, and twigs and 1 inch of partly decomposed and well decomposed organic material. The surface layer is about 3 inches thick. It is black, very friable loamy coarse sand in the upper 1 inch and gray, loose coarse sand in the lower 2 inches. The subsoil is about 26 inches thick. In sequence downward, it is 1 inch of dark brown, very friable gravelly loamy coarse sand; 5 inches of strong brown, very friable gravelly loamy coarse sand; 10 inches of yellowish brown, very friable gravelly loamy coarse sand; and 10 inches of light yellowish brown, loose gravelly coarse sand. The substratum extends to a depth of 65 inches or more. It is light brownish gray, loose gravelly coarse sand in the upper 12 inches and pale brown, loose coarse sand in the lower part.
Typically, the surface of the Barnstable soil is covered with an organic layer. This layer is about 1 inch of undecomposed pine needles, leaves, and twigs and 2 inches of partly decomposed and well decomposed organic material. The surface layer is dark gray, very friable sandy loam about 1 inch thick. The subsoil is friable sandy loam about 22 inches thick. The upper 1 inch is dark brown, the next 7 inches is yellowish brown, and the lower 14 inches is olive brown. The substratum to a depth of 65 inches or more is light yellowish brown, loose coarse sand.
Included with these soils in mapping are small areas of Carver, Hinckley, and Nantucket soils and small areas where slopes are less than 15 percent. Also included are small, isolated areas where less than 3 percent of the surface is covered with boulders. Included soils make up about 25 percent of this unit.
Permeability is rapid in the subsoil of the Plymouth soil and very rapid in the substratum. Available water capacity is low. Depth to the seasonal high water table is more than 6 feet;
Permeability is moderately rapid in the subsoil of the Barnstable soil and rapid or very rapid in the substratum. Available water capacity is moderate. Depth to the seasonal high water table is more than 6 feet.
Most areas are used as woodland. These soils are unsuitable as cropland because the surface stones and boulders restrict the use of equipment. Erosion is a hazard because of the slope. The Plymouth soil is droughty during periods of low rainfall.
These soils are very poorly suited to hay and pasture because of the slope and the surface stones and boulders. The main management objective is the prevention of overgrazing, which reduces the hardiness and density of desirable plants. Proper stocking rates, timely grazing, and restricted use during wet periods help to maintain plant density and minimize surface compaction.
These soils are poorly suited to woodland. The use of equipment is restricted because of the slope and the boulders. The Plymouth soil is droughty. As a result, some seedling loss is expected. Thinning dense stands to standard stocking levels results in more vigorous tree growth. Removal or control of competing vegetation helps to obtain the best growth of newly established seedlings. The most common trees are pitch pine, white oak, scarlet oak, eastern white pine, and black oak.
The slope is the main limitation if these soils are used as sites for buildings. Extensive land shaping is generally needed. Buildings and lots should be designed so that they conform to the natural slope of the land. Erosion is a severe hazard during and after construction. Planting well suited grasses as soon as possible after the surface is disturbed minimizes the erosion hazard. The surface and subsurface boulders may interfere with site development.
These soils are poorly suited to septic tank absorption fields because of the slope and the rapid or very rapid permeability. The soils may not adequately filter the effluent. The poor filtering capacity may result in the pollution of ground water. The hazard of pollution increases with the density of housing. Installing the distribution lines on the contour or in areas that were graded during construction of the dwelling helps to overcome the slope. Precautionary measures may be necessary in some areas.
