A hydraulic debarker is a machine removing bark from

wooden log Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...

s by the use of water under a pressure of or greater. Hydraulic debarking can reduce soil and rock content of bark, but may increase the water content. Debarking water may be recycled after effective settling, but suspended solids may increase wear on high-pressure pumps. Hydraulic debarking has declined where water quality problems have arisen.

History

Bark on mature

redwood Sequoioideae, popularly known as redwoods, is a subfamily of coniferous trees within the family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affini ...

trees of coastal

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

can vary from in thickness. Redwood bark is thick, stringy and tough; and can cause

sawmill A sawmill (saw mill, saw-mill) or lumber mill is a facility where logs are cut into lumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes (dimensi ...

machinery to malfunction. Men called peelers removed bark from fallen trees in the woods through the early 20th century, but the process was dangerous and

labor intensive Labor intensity is the relative proportion of Labour (economics), labor (compared to Capital (economics), capital) used in any given process. Its inverse is capital intensity. Labor intensity has been declining since the onset of the Industrial Re ...

. In the mid-20th century hydraulic barkers were built at several large sawmills including the Union Lumber Company at

Fort Bragg, California Fort Bragg, officially the City of Fort Bragg, is a city along the Pacific Coast of California along Shoreline Highway in Mendocino County. The city is west of Willits, at an elevation of . Its population was 6,983 at the 2020 census. Fort ...

, the Northern Redwood Company at

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, and the

Pacific Lumber Company The Pacific Lumber Company, officially abbreviated PALCO, and also commonly known as PL, was one of California's major logging and sawmill operations, located 28 miles (45 km) south of Eureka and 244 miles (393 km) north of San Francisc ...

Scotia, California Scotia, formerly known as Forestville until 1888, is a census-designated place in Humboldt County, California. It is located on the Eel River along U.S. Route 101, southeast of Fortuna and north of San Francisco. Scotia has a population of 85 ...

. The last was featured in a popular sawmill tour.

Operation

Although less expensive mechanical debarkers were adequate for smaller logs harvested from young trees on redwood tree farms, hydraulic barkers remained in operation until all

old growth An old-growth forestalso termed primary forest, virgin forest, late seral forest, primeval forest, or first-growth forestis a forest that has attained great age without significant disturbance (ecology), disturbance, and thereby exhibits un ...

trees had been harvested from company timberlands. The

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...

published hydraulic barking category effluent limitations in the 1970s. Wastewater discharged from debarking could average no more than 2.5 pounds of

biochemical oxygen demand Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) needed (i.e. demanded) by aerobic biological organisms to break down organic material present in a given water sample at a certain temperature over a specific time period. T ...

(BOD) and 12 pounds of

total suspended solids Total suspended solids (TSS) is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus known as sintered glass crucible. TSS is a water qua ...

(TSS) per thousand board feet of lumber produced (0.5 kg BOD and 2.3 kg TSS per cubic meter of lumber). Daily waste discharge rates could be three times as high as 30-day averages, but pH was required to remain between 6 and 9.40CFR429.21(b)
Accessed 2012-09-13

References

* Carranco, Lynwood ''Redwood Lumber Industry'' Golden West Books, San Marino, California (1982)

Notes

{{Forestry tools Sawmill technology Forestry equipment