The following is a map unit description from the "Soil Survey of Norfolk and Suffolk Counties, Massachusetts (Peragallo, 1989)"
MnB-Merrimac-Urban land complex, 0 to 8 percent slopes. This map unit consists of nearly level and undulating Merrimac soil and similar soils and areas of Urban land on broad plains. The Merrimac soil is very deep and somewhat excessively drained, A typical map unit is 45 percent Merrimac soil, 40 percent Urban land, and 15 percent other soils. The Merrimac soil and areas of Urban land are in such an intricate pattern on the landscape that it was not practical to separate them at the scale used for mapping. Areas of this map unit are rectangular or irregular in shape and range from 10 to 1,000 acres.
Typically, the surface layer of the Merrimac soil is dark brown fine sandy loam about 9 inches thick. The subsurface layer is about 14 inches thick. It is yellowish brown fine sandy loam in the upper part and yellowish brown loamy sand in the lower part. The substratum is light yellowish brown, stratified very gravelly coarse sand to a depth of 60 inches or more. In areas of this soil in the Boston Basin, the subsoil and the substratum are mostly olive colored and, by volume, 50 to 75 percent of the coarse fragments are dark, flat shale and slate.
Urban land consists of areas where the original soil has been covered with impervious surfaces, such as asphalt, concrete, and buildings. In many places the underlying soil has been cut away or covered by fill from adjacent areas.
Included with this unit in mapping are small areas of Hinckley and Windsor soils in landscape positions similar to those of the Merrimac soil. Also included are areas of Sudbury soils that are in low areas and depressions and that have a seasonal high water table. Included areas make up about 20 percent of the map unit.
Soil properties of the Merrimac soil:Permeability: Moderate or moderately rapid in the
surface layer and the subsoil and rapid or very rapid in the
substratum.
Available water capacity: Moderate.
Soil reaction: Very strongly acid to moderately acid
throughout.
Depth to bedrock: More than 60 inches.
Depth to the seasonal high water table: More than 6
feet.
Hydrologic group: A.
The mapped areas of this complex are in residential and commercial uses. The Merrimac soil has no major limitations for building site development or for local roads and streets. If the soil is used as sites for septic tank absorption fields, ground water pollution is a hazard. Because of rapid or very rapid permeability, the soil readily absorbs but does not adequately filter the effluent.
The Merrimac soil is well suited to lawns,landscaping, and vegetable gardens. Moderate irrigation is needed during dry periods because the soil is droughty.The Merrimac soil has not been assigned to a capability subclass.
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