Clamshell dredger Mallard II moving mud in San Francisco Bay

''Mallard II'' is a wooden-hulled clamshell dredger used to maintain

levees A levee ( or ), dike (American English), dyke (British English; see spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against fl ...

on the

San Francisco Bay Salt Ponds The San Francisco Bay Salt Ponds are a roughly part of the San Francisco Bay that have been used as salt evaporation ponds since the California Gold Rush era. Most of the ponds were once wetlands in the cities of Redwood City, Newark, and Hay ...

. ''Mallard II'' was constructed in 1936, and is "probably the oldest operating dredge in California"; she is owned and operated by Cargill Salt.

History

''Mallard II'' was built in 1936, and has maintained the levees of the salt ponds ever since, except for a brief period during

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

during which she was used to retrieve

artillery shells A shell, in a modern military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. A shell c ...

from the floor of the Bay near

Mare Island Mare Island (Spanish language, Spanish: ''Isla de la Yegua'') is a peninsula in the United States in the city of Vallejo, California, about northeast of San Francisco. The Napa River forms its eastern side as it enters the Carquinez Strait junc ...

and the Port Chicago Naval Magazine. Over time, she received extensive upgrades (including a modern engine, steel

A-frame An A-frame is a basic structure designed to bear a Structural load, load in a lightweight economical manner. The simplest form of an A-frame is two similarly sized Beam (structure), beams, arranged in an angle of 45 degrees or less, attached a ...

and boom). The steel frame was installed by Bethlehem Pacific's San Francisco shipyard in 1954, at which point she maintained levees on over of ponds in the South Bay as well as

Napa County Napa County () is a County (United States), county north of San Pablo Bay located in the Northern California, northern portion of the U.S. state of California. As of the 2020 United States census, the population was 138,019. The county seat i ...

. She has been described as a "floating wood-and-metal dinosaur", with a bucket capable of moving as much as of mud per day. While dredging, she is anchored by "spikes", and moves from place to place by "grabbing hold of the sea floor". ''Mallard II'' was used to construct such watercourses as North Creek; in 1972 she was briefly idled while the Leslie Salt Company sought dredging permits from the

United States Army Corps of Engineers The United States Army Corps of Engineers (USACE) is the military engineering branch of the United States Army. A direct reporting unit (DRU), it has three primary mission areas: Engineer Regiment, military construction, and civil wo ...

. Salt ponds on which ''Mallard II'' is used must be kept at a higher water level than they otherwise would be, owing to her

draft Draft, the draft, or draught may refer to: Watercraft dimensions * Draft (hull), the distance from waterline to keel of a vessel * Draft (sail), degree of curvature in a sail * Air draft, distance from waterline to the highest point on a v ...

. In 2002, she was used for the Eden Landing wetland restoration project, for which Cargill donated the use of the dredger and 400 man-hours of labor. As of 2007, she was the only wooden-hulled clamshell dredger operating in San Francisco Bay, as well as "probably the oldest operating dredge in California", responsible for maintaining of levees between Hayward,

Redwood City Redwood City is a city on the San Francisco Peninsula in the Bay Area of Northern California, approximately south of San Francisco and northwest of San Jose. The city's population was 84,292 according to the 2020 census. The Port of Redwo ...

and San Jose. She repairs and maintains approximately of levee per year. ''Mallard II'' can operate for more than two months without being refueled. As of December 2020, she was still operational.

Levees

The levees surrounding the

date to the late 1800s, and were mostly constructed to reclaim land for agricultural purposes; the area enclosed by them was later used for salt production. In addition to their role in operating the salt ponds, the levees protect

Bay Area The San Francisco Bay Area, commonly known as the Bay Area, is a region of California surrounding and including San Francisco Bay, and anchored by the cities of Oakland, San Francisco, and San Jose. The Association of Bay Area Governments ...

cities like San Jose from being flooded by high tides. Due to factors such as

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

and

subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...

, the levees require regular maintenance. Dredging material to increase the levees' height, the "least expensive technique available", consists of moving ''Mallard II'' into a salt pond through a set of locks and using her

clamshell bucket A bucket (also called a scoop to qualify shallower designs of tools) is a specialized container attached to a machine, as compared to a bucket adapted for manual use by a human being. It is a bulk material handling component. The bucket has an in ...

to remove material from a

borrow pit Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surface, usually soil, sand or rock on the surface of Earth. Digging is actual ...

; this material is then deposited atop the levee. When ''Mallard II'' is present in a salt pond, waterfowl hunting is not permitted. A December 2020 permit for a wetlands project issued by the

California Department of Fish and Wildlife The California Department of Fish and Wildlife (CDFW), formerly known as the California Department of Fish and Game (CDFG), is an American state agency under the California Natural Resources Agency. The Department of Fish and Wildlife manages ...

provided for maintenance of salt ponds to be carried out by the still-operational ''Mallard II'', using the existing system of dredge locks, referred to as "the most technologically and economically feasible method for solar salt production in south San Francisco Bay". While it would be possible to reduce some of the adverse impacts of levee maintenance (mostly caused by the existence of the dredge lock system) by using a "transportable dredge", it was found that such a dredge would require more frequent refueling (every two weeks, as opposed to every two months with ''Mallard II''), as well as the use of large trucks and cranes to reposition it; ''Mallard II'', therefore, was found to be the "most feasible alternative". A 2005 estimate of expenses for levee maintenance in the area put the cost of using ''Mallard II'' at approximately $50,000 per month.

References

{{Reflist, refs= {{cite news , url = https://www.newspapers.com/clip/86175918/leslie-salt-co-dredge-repaired/ , date = 1954-12-30 , page = 2 , title = Leslie Salt Co. Dredge Repaired , newspaper = The Napa Valley Register , location = Napa, California {{cite news , url = https://www.newspapers.com/clip/86176144/spy-in-sky-check-on-bay-fill/ , date = 1972-06-05 , page = 19 , title = 'Spy in Sky' Check on Bay Fill , newspaper = Oakland Tribune , location = Oakland, California {{Cite web , url = https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?referer=&httpsredir=1&article=2318&context=theses , title = Amphibious Architecture: Living with a Rising Bay , first = Heather , last = Anderson , date = June 2014 , publisher = California Polytechnic State University, San Luis Obispo , access-date = 2021-08-09 {{cite web , url = https://www.paloaltoonline.com/media/reports/1301329696.pdf , title = Cooley Landing: Cultural Resource Inventory and Assessment , first1 = R. Scott , last1 = Baxter , first2 = Rebecca , last2 = Allen , first3 = Mark G. , last3 = Hylkema , publisher = City of East Palo Alto , website = Palo Alto Online , date = August 2007 , access-date = 2021-07-06 , archive-date = 2021-04-22 , archive-url = https://web.archive.org/web/20210422173957/https://www.paloaltoonline.com/media/reports/1301329696.pdf , url-status = live {{cite web , url = https://research-benton.ced.berkeley.edu/he/?p=27 , first = Cris , last = Benton , publisher =

University of California The University of California (UC) is a public university, public Land-grant university, land-grant research university, research university system in the U.S. state of California. Headquartered in Oakland, California, Oakland, the system is co ...

Berkeley , title = The Mallard II , date = 30 September 2005 , website = Hidden Ecologies , access-date = 6 July 2021 , archive-date = 9 July 2021 , archive-url = https://web.archive.org/web/20210709185131/https://research-benton.ced.berkeley.edu/he/?p=27 , url-status = live {{cite web , url = https://bcdc.ca.gov/planning/reports/SaltPonds_Jun2005.pdf , title = Staff Report: Salt Ponds , publisher = San Francisco Bay Conservation and Development Commission , date = October 2005 , access-date = 2021-07-06 , archive-date = 2021-07-09 , archive-url = https://web.archive.org/web/20210709183519/https://bcdc.ca.gov/planning/reports/SaltPonds_Jun2005.pdf , url-status = live {{cite web , url = http://aquaticcommons.org/1878/1/South_Bay_Salt-Ponds_Full_Report.pdf , title = Feasibility Analysis: South Bay Salt Pond Restoration, San Francisco Estuary, California , first1 = Stuart W. , last1 = Siegel , first2 = Philip A.M. , last2 = Bachand , date = 2002 , publisher = Wetlands and Water Resources , access-date = 2021-07-06 , archive-date = 2021-07-09 , archive-url = https://web.archive.org/web/20210709184322/http://aquaticcommons.org/1878/1/South_Bay_Salt-Ponds_Full_Report.pdf , url-status = live {{cite web , url = http://www.cargill.com/sf_bay/tour_3.htm , title = Virtual Tour , author = Cargill , access-date = 2021-07-17 , archive-date = 2008-09-07 , archive-url = https://web.archive.org/web/20080907212344/http://www.cargill.com/sf_bay/tour_3.htm , url-status = live {{cite web , first = Wendy , last = Philips , title = Dredger sculpting Hayward wetlands , newspaper =

Oakland Tribune The ''Oakland Tribune'' was a daily newspaper published in Oakland, California, and a predecessor of the '' East Bay Times''. It was published by the Bay Area News Group (BANG), a subsidiary of MediaNews Group. Founded in 1874, the ''Tribune'' ...

, date = 2002-07-21 , url = https://www.southbayrestoration.org/news/articles/article5.html {{cite web , first = John , last = Krist , date = 2002-07-21 , url = https://www.southbayrestoration.org/news/articles/article11.html , newspaper =

Ventura County Star The ''Ventura County Star'' (Marked online as VC Star) is a daily newspaper published in Camarillo, California and serves all of Ventura County. It is owned by Gannett, the largest publisher of newspapers in the United States. It is a successor t ...

, title = Restoration of wetlands will take money, time {{cite web , url = https://www.southbayrestoration.org/sites/default/files/documents/2003.007.03edenlanding2020.12.18_bcdcoriginal_1.pdf , title = BCDC PERMIT NO. 2003.007.03 , author = San Francisco Bay Conservation and Development Commission , publisher = California Department of Fish and Wildlife , date = 2020-12-18 {{cite web , url = https://www.southbayrestoration.org/monitoring/2007%20EDEN%20B%20ASMR.pdf , first = John , last = Krause , publisher = California Department of Fish and Game , date = 2007 , title = 2007 Self-Monitoring Report: Baumberg Complex – Hayward, California, Eden Landing Ecological Reserve {{cite web , url = https://www.southbayrestoration.org/pdf_files/monitoring/Baumberg%20Self-monitoring%202005%20(Feb%202006).pdf , first = John , last = Krause , publisher = California Department of Fish and Game , date = 2005 , title = 2005 Self-Monitoring Report: Baumberg Complex – Hayward, California, Eden Landing Ecological Reserve {{cite web , url = https://www.southbayrestoration.org/pdf_files/Flood_Management_Existing_Conditions.3.30.05.pdf , author = Philip Williams & Associates, Ltd. , publisher = South Bay Restoration , date = 2005 , title = Flood Management and Infrastructure Existing Conditions Report {{cite web , url = https://www.fws.gov/uploadedFiles/Region_8/NWRS/Zone_2/San_Francisco_Bay_Complex/Don_Edwards_San_Francisco_Bay/Sections/Visit/Visitor_Activities/Waterfowl_Hunting/2019-20%20Hunting%20Regulations_7-31-19%20revised.pdf , title = Don Edwards San Francisco Bay National Wildlife Refuge: 2019 -2020 Waterfowl Hunting Regulations , author = U.S. Fish & Wildlife Service , date = July 2019 , access-date = 2021-08-09 Dredgers 1936 ships Cargill San Francisco Bay Salt production