ESRM311/SEFS507
Organic Soil Development and Use
Stop 1.
Mercer Slough. Mapped as Seattle series. We will enter a business part off of I-405 (8th Street
Exit) built on wetland soils associated with Mercer Slough. This wetland has come under intense
development recently because of its proximity to I-5 and I-405...the perfect business location.
There is reason why this land is among the last to be developed in this region. In particular note
local stream levels, the condition of building foundations, evidence of soil and building
movement, etc.
Stop 2.
Larsen Lake. Mapped as Seattle series. Glacial action has created the many freshwater bodies
in the state of Washington. Sedimentation has filled many in (i.e. Mercer Slough). Larsen Lake
is a formerly much larger lake that has not completely filled in. Note the present uses of the
areas directly around the lakes. Where does the lake use change substantially?
Stop 3.
Issaquah constructed wetland. This site is a constructed wetland. There was some wetland
area that was expanded to mitigate construction on wetlands in nearby areas. Compare this
wetland with the natural wetlands you’ve seen. Think about what makes a wetland functional. Is
the wetland you see functioning as a wetland?
Things to think about:
1) Take a guess at the depth of organic matter in the region of stop 1. What would you
prescribe as a solution to the present problem? How would you avoid such a problem
in the future, but still develop the area?
How would this site develop without any further disturbance?
2) How is Larsen Lake different than Mercer Slough? What are the primary differences
between them? What about restrictions to development of this area?. Has the present
use of the site affected it greatly? Are the uses appropriate? Do they affect surrounding
areas?
SEATTLE SERIES
The Seattle series consists of very deep, very poorly drained organic soils formed in herbaceous and woody deposits in
depressions in river valleys and glacial till plains. Slopes are 0 to 1 percent. Average annual precipitation
is about 40 inches. Mean annual temperature is about 50 degrees F.
TAXONOMIC CLASS: Euic, mesic Hemic Haplosaprists
TYPICAL PEDON: Seattle muck, pasture. (Colors are for moist soil unless otherwise noted.)
Oap--0 to 11 inches; black (5YR 2/1) muck, black (10YR 2/1) dry; about 10 percent fibers, less than 1 percent rubbed; strong
fine granular structure; hard, very friable, nonsticky, nonplastic; many roots; strongly acid (pH
5.4); clear smooth boundary. (10 to 13 inches thick)
Oe--11 to 17 inches; dark reddish brown (5YR 2/2) mucky peat, black (10YR 2/1) and dark brown (10YR 4/3) dry; about 60
percent fibers, 25 percent rubbed; laminar structure; very hard, very friable, nonsticky, nonplastic;
common roots; strongly acid (pH 5.1); clear smooth boundary. (3 to 12 inches thick)
Oa1--17 to 21 inches; black (5YR 2/1) muck, black (5YR 2/1) dry; about 5 percent fibers, less than 1 percent rubbed; massive;
very hard, very friable, slightly sticky, slightly plastic; few roots; very strongly acid (pH 4.8);
clear wavy boundary. (0 to 6 inches thick)
Oa2--21 to 35 inches; very dark brown (7.5YR 2/2) muck, very dark grayish brown (10YR 3/2) and pale brown (10YR 6/3) dry;
about 45 percent fibers, 15 percent rubbed; massive, very hard, very friable, nonsticky,
nonplastic; few roots; moderately acid (pH 6.0); clear smooth boundary. (12 to 17 inches thick)
O'e--35 to 60 inches; dark brown (7.5YR 3/4) mucky peat, very dark brown (10YR 2/2) and brown (10YR 5/3) dry; about 70
percent fibers, 35 percent rubbed; massive; very hard, very friable, nonsticky, nonplastic; few
roots; moderately acid (pH 5.8 water).
TYPE LOCATION: King County, Washington; 200 feet east, 500 feet north of center sec. 2, T.24N., R.5E.
RANGE IN CHARACTERISTICS: The organic deposits range in depth from 51 inches to more than 40 feet. Mean annual soil
temperature is 47 to 52 degrees F. The difference between mean winter and mean summer
soil temperature is 15 to 30 degrees F. Fibers are mostly from sedges but some pedons are up to 25 percent wood fragments. The
subsurface and bottom tiers (12 to 51 inches) contain 10 to 25 inches of hemic material. The
soils are very strongly acid or moderately acid.
The surface tier (0 to 12 inches) has hue of 10YR, 7.5YR, or 5YR, value of 1 to 4 moist, 2 to 6 dry, and chroma of 1 to 4 moist
or dry. It is sapric material, with 5 to 40 percent fibers, unrubbed, and less than 10 percent
rubbed. This tier has moderate or strong granular structure.
The subsurface tier (12 to 36 inches) has hue of 10YR, 7.5YR, or 10YR, value of 2 or 3 moist, 2 to 7 dry, and chroma of 1 to 5
moist or dry. It is more than one-half sapric material. It is sapric and hemic material with thin
layers of sedge peat. The fiber content ranges from 30 to 70 percent, 10 to 35 percent rubbed.
The bottom tier (36 to 51 inches) is similar in color to the subsurface tier and fiber content is generally higher than the subsurface
tier.
COMPETING SERIES: This is the Pinnebog series and the similar McMurray series. Pinnebog soils have a difference between
mean winter and mean summer temperature of more than 30 degrees F and the soil reaction of
Pinnebog soils are typically slightly alkaline. McMurray soils are dominantly hemic material in the subsurface tier.
GEOGRAPHIC SETTING: The Seattle soils are in depressions on glacial till plains and river terraces at elevations ranging from
near sea level to 1,000 feet. Seattle soils formed in organic materials. These soils occur in a
mild marine climate having cool dry summers and mild wet winters. The average annual precipitation is 25 to 50 inches. The
average January temperature is 38 degrees F, the average July temperature is 64 degrees F, and the
mean annual temperature is 50 degrees F. The average frost free season is 150 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alderwood, Buckley, Everett, and Shalcar soils. Alderwood,
Buckley, and Everett soils are all mineral soils. In addition, Alderwood soils are
loamy-skeletal. Everett soils are sandy-skeletal. Buckley soils are fine-loamy. Shalcar soils have a loamy substratum within 51
inches.
DRAINAGE AND PERMEABILITY: Very poorly drained; very slow to ponded runoff; moderate permeability.
USE AND VEGETATION: Most Seattle soils have been cleared and drained for use as cropland or pasture. Hay, corn silage,
blueberries, and truck crops are common crops. In the natural state the vegetation consists of
red alder, western red cedar, black cottonwood and Sitka spruce with an understory of sedge, rush, cattail, hardhack, trailing
blackberry, red elderberry, devilsclub, Siberian miners lettuce, trillium, salmonberry, and ladyfern.
DISTRIBUTION AND EXTENT: This series is of moderate extent in the Puget Sound Basin of Western Washington.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: King County, Washington, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are a surface tier from the surface to 12 inches that is
sapric material from 0 to 11 inches and hemic from 11 to 12 inches, a subsurface tier from 12 to 36
inches that is sapric for 18 inches and hemic for 6 inches, and a bottom tier from 36 to 51 inches that is hemic throughout.
SULTAN SERIES
The Sultan series consists of very deep, moderately well drained soils formed in recent alluvium on floodplains at elevations of
near sea level to 120 feet. Slopes are 0 to 3 percent. Average annual precipitation is about 45
inches. Mean annual temperature is 50 degrees F.
TAXONOMIC CLASS: Fine-silty, isotic, mesic Aquandic Dystroxerepts
TYPICAL PEDON: Sultan silt loam - pasture. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 9 inches; very dark grayish brown (10YR 3/2) silt loam, light brownish gray (10YR 6/2) dry; moderate medium granular
structure; hard, firm, moderately sticky, moderately plastic; many roots; slightly acid (pH
6.4); abrupt smooth boundary. (6 to 10 inches thick)
Bw1--9 to 21 inches; yellowish brown (10YR 5/4) silty clay loam, pale brown (10YR 6/3) dry; moderate fine subangular blocky
structure; hard, friable, moderately sticky, moderately plastic; many roots; slightly acid (pH
6.4); clear wavy boundary. (10 to 14 inches thick)
Bw2--21 to 24 inches; light olive brown (2.5Y 5/4) silt loam, pale yellow (2.5Y 7/4) dry; many medium prominent yellowish
brown (10YR 5/8) mottles; moderate medium subangular blocky structure; hard, very friable,
slightly moderately sticky, slightly plastic; common roots; neutral (pH 6.6); clear wavy boundary. (2 to 5 inches thick)
Bg--24 to 48 inches; grayish brown (2.5Y 5/2) silty clay loam, pale yellow (2.5Y 8/2) dry; many medium prominent yellowish
brown (10YR 5/8) mottles; moderate medium prismatic structure; slightly hard, very friable,
moderately sticky, moderately plastic; few roots; neutral (pH 6.6); clear wavy boundary. (20 to 30 inches thick)
Cg--48 to 66 inches; olive gray (5Y 5/2) very fine sandy loam stratified with medium sand, light gray (2.5Y 7/2) dry; common
fine prominent yellowish red (5YR 4/6) mottles; massive; slightly hard, very friable; few roots;
very strongly acid (pH 4.8).
TYPE LOCATION: King County, Washington; 2,140 feet west, 250 feet north of southeast corner of sec. 9, T. 25 N., R. 7 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is estimated to range from 47 to 52 degrees F. These soils are
usually moist, but are dry in all parts between depths of 3 and 12 inches for 45 to 60
consecutive days during the summer. The particle-size control section averages less than 5 percent coarse fragments, less than 15
percent coarser than very fine sand, and has 20 to 35 percent clay.
The Ap horizon has value of 3 or 4 moist, 5 or 6 dry, and chroma of 2 or 3 moist and dry. It has moderate to weak structure.
Reaction is slightly acid or neutral.
The Bw horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, 6 or 7 dry, and chroma of 3 or 4 moist or dry. Texture is silt
loam or silty clay loam. It has moderate or weak structure. Reaction is slightly acid or neutral.
The Bg horizon has hue of 5Y or 2.5Y, value of 4 to 7 moist, 5 to 8 dry, and chroma of 1 or 2 moist or dry. Textures is silt loam,
very fine sandy loam, or silty clay loam. Reaction is slightly acid or neutral.
The Cg horizon has hue of 5Y or 2.5Y, value of 4 to 7 moist, 5 to 8 dry, and chroma of 0 to 2 moist or dry. Texture is stratified
and ranges from silt loam to sand. Reaction ranges from very strongly acid to neutral.
COMPETING SERIES: These are Belle and Queets series in other families. Belle soils have 10YR hue throughout and are very
strongly acid and strongly acid. Belle and Queets soils have a cambic horizon and a udic
moisture regime.
GEOGRAPHIC SETTING: The Sultan series are in the parts of river valleys that have slightly undulating microrelief at
elevations ranging from near sea level to 120 feet. They formed in stratified loamy alluvium. The
climate is marine. Average January temperature is 38 degrees F, average July temperature is 64 degrees F, and mean annual
temperature is 50 degrees F. The average annual precipitation ranges from 35 to 55 inches and most
of it falls as rain during winter. Snow is infrequent. The frost-free season ranges from 150 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Nooksack, Pilchuck, Puget, Puyallup, and Woodinville soils.
Nooksack soils are coarse-silty and have a mollic epipedon. Pilchuck soils are sandy.
Puyallup soils have a mollic epipedon and are coarse-loamy over sandy or sandy-skeletal. Woodinville soils have an aquic
moisture regime and thin lenses of organic material within the series control section.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow runoff; moderately slow permeability.
USE AND VEGETATION: Most of the Sultan soils have been cleared and are used for growing seeded grass pasture or row
crops. Native vegetation consists of Douglas-fir, red alder, and western redcedar with an
understory of Douglas spirea, trailing blackberry, salmonberry, thimbleberry. Oregon-grape, willow, western swordfern, vine
maple, and tree seedlings.
DISTRIBUTION AND EXTENT: The series is of moderate extent in the Puget Sound Basin of Western Washington.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Snohomish County, Washington, 1937.
REMARKS: Classification updated 3/94 and 1/00 because of amendments to Soil Taxonomy. Diagnostic horizons and features
recognized in this pedon are an ochric epipedon from the surface to 9 inches, a cambic horizon
from 9 to 24 inches, a particle-size control section that is assumed to have an irregular decrease in organic carbon and the soil is
assumed to have more than 0.2 percent organic carbon from 50 to 60 inches. Base saturation is
less than 60 percent (NH4Oac) from 10 to 30 inches and is based on lab data from the associated Puget series.