Colorado State University Fort Collins. Circular 203-A (Revised) Cooperative Extension Service. Rocky. Sealing. Ditches. (o,i ~~)

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1 Colorado State University Fort Collins I I ' Circular 203-A (Revised) Cooperative Extension Service Sealing <v Rocky Ditches (o,i ~~)

This circular presents a summary of the methods that utilize locally available clays or bentonites for low-cost sealing of ditches or canals traversing rocky to gravelly materials.

This research has been sponsored by the Colorado Agricultural Experiment Station and the Colorado State University Research Foundation in cooperation with other organizations, including the Colorado

2 This circular presents a summary of the methods that utilize locally available clays or bentonites for low-cost sealing of ditches or canals traversing rocky to gravelly materials. This summary is based on the evaluation of data obtained from approximately 100 field trials (1961 ). Low-cost canal sealing with clay has been under study at Colorado State University since This research has been sponsored by the Colorado Agricultural Experiment Station and the Colorado State University Research Foundation in cooperation with other organizations, including the Colorado Water Conservation Board, the Southeastern Colorado Water Conservancy District, the U. S. Agricultural Research Service, the U. S. Bureau of Reclamation and many irrigation districts and private companies. Issued in furtherance of Cooperative Extension Work in agriculture and home economics Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lowell H. Watts, Director of Extension Service, Colorado State University. FORT COLLINS, COLORADO APRIL, M 4-62 Written by R. D. Dirmeyer, Jr., M. M. Skinner and R. T. Shen, Civil Engineering Department, Colorado State University. Illustrations by R. T. Shen.

? * Do you have a ditch or canal through rocky or

* Does it lose a lot of water and cause seep damage?

3 ? * Do you have a ditch or canal through rocky or gravelly material? * Does it lose a lot of water and cause seep damage? * How can you reduce this seepage at a cost you can afford? Your answer may be in locally available clay or bentonite! With a proper clay material and installation procedure: You can stop or reduce water loss! You can dry adjacent water-logged land! You can do this without special equipment and at low cost! o o~~<) -1-

4 ~00 tt 1()~ I * Certain (bentonitic) clays impede water passage. When applied properly, they will fill the voids in the ditch bed and reduce water loss. * They are available in processed form (granular or powdered). In many areas they are also available in natural deposits. * Low-grit clays are best for sealing sandy soils. Sanely to silty clays are best for sealing extremely rocky and gravelly materials. BEFORE SEALING SEALING

SANDY MATERIAL, the task is PENETRATION! In OPEN ROCK MATERIAL, the task is RETENTIOI For a lasting seal, the clay must fill the voids to at least a 3- inch depth.

Penetration is achieved easily but a grit-free clay may not stay in place. A gritty (but water-tight) clay material is more desirable. In some cases, a filler (such as sawdust) is added to the clay.

Before using locally available deposits, be sure they have good sealing characteristics. A low moisture content, which can be obtained by air-drying at the pit, is also important.

5 SANDY MATERIAL, the task is PENETRATION! In OPEN ROCK MATERIAL, the task is RETENTIOI For a lasting seal, the clay must fill the voids to at least a 3- inch depth. This may be achieved by mixing the clay into the sandy material by discing, harrowing, etc. A grit-free clay is advantageous for this use. Penetration is achieved easily but a grit-free clay may not stay in place. A gritty (but water-tight) clay material is more desirable. In some cases, a filler (such as sawdust) is added to the clay. * Remember all clays are not water-tight. Also the best local clays may have as much as 50 percent inplace moisture content. Before using locally available deposits, be sure they have good sealing characteristics. A low moisture content, which can be obtained by air-drying at the pit, is also important. * The amount of clay to use depends on the quality and moisture content of the clay and the nature of the ditch material. In past installations, it has varied: From l to 3 pounds of grit-free dry bentonite (layer Ys to Y2 inch thick) for each square foot of wetted area in sandy and gravelly ditches. To as much as 30 pounds of a local, moist, gritty clay (layer 3-4 inches thick) for each square foot of wetted area in extremely coarse rocky ditches. Experienced personnel (contractor, Extension Agent, or Soil Conservation Service technician) can help you choose the kind of clay you need and determine the amount to use

Rip-rap eroding areas of your ditch bed and banks.

6 ~~ foeeii fjod * Do maintenance and repair work before starting the clay sealing work. For lasting results the ditch must be stable. Rip-rap eroding areas of your ditch bed and banks. Clean ditch and remove willows and trees as much as possible. Build a ditch bank road if you can. Good results come from good preparation. -4-

* Obtain technical information necessary for a good sealing job: Compare inflow and

Map or photograph the extent of seep damage below the leaky zones.

Survey your ditch section to compute the wetted area below the high-water line.

7 * Obtain technical information necessary for a good sealing job: Compare inflow and outflow records to determine the actual seepage loss for the section to be treated. Map or photograph the extent of seep damage below the leaky zones. Locate the highseepage sections that feed springs below the ditch. Survey your ditch section to compute the wetted area below the high-water line. Examine the bed and bank materials to determine the type of clay material needed. Consult your local Extension Agent or SCS technician for advice. -5-

As the first dam is overtopped by the ponded water, break the dam rapidly to make a clay slurry. ~ Repeat this operation for each dam.

8 ~ t '" ~ * The Multiple Dam Method is used when the ditch section can be easily reached by truck at most points: ~ Place the clay in the ditch to form dams, spacing them close enough so that water can be ponded to the high-water line. ~ Turn in a small flow of water. As the first dam is overtopped by the ponded water, break the dam rapidly to make a clay slurry. ~ Repeat this operation for each dam. Try to keep the slurry ponded for as long as possible behind each dam. Supplement the above method with clay (2 to 6 inches thick) in extremely high-loss zones, especially on the upper bank areas. -6 -

During a time of high seepage loss, add clay into the "flowing ditch water with a front-loader tractor or similar equipment.

9 * The Wash-In Method is used when many parts of the ditch sectic;m are not readily accessible or when the water in the ditch cannot be shut off. ~ Stockpile the clay near the head end of the section and, if possible, at a few other points along the upper half of the section. During a time of high seepage loss, add clay into the "flowing ditch water with a front-loader tractor or similar equipment. As the slurry flows downstream, replenish it by adding the rest of the stockpiled clay. Choose your method according to your conditions. In some instances, a combination of the multiple-dam, wash-in, and blanket methods may give best results. -7 -

$ffjl\!.~~ ~ * Sealing characteristics Select a clay of known sealing ability as demonstrated in nearby installations of clay sealing projects.$ ability. In-place clay may have as much as 50 percent moisture; air-drying at the pit can reduce the moisture content to as little as 10 percent.. ~ -"- '...., L"-..... ~ -~:~~-- ~.

ability. In-place clay may have as much as 50 percent moisture; air-drying at the pit can reduce the moisture content to as little as 10 percent.. ~ -"- '...., L"-..... ~ -~:~~-- ~.

10 ffjl\!.~~ ~ * Sealing characteristics Select a clay of known sealing ability as demonstrated in nearby installations of clay sealing projects. Without such a clay, selection should be based on results of laboratory tests of samples 1 * Moisture content Compare costs of clays on the basis of dry weight-provided they are equal in sealing ability. In-place clay may have as much as 50 percent moisture; air-drying at the pit can reduce the moisture content to as little as 10 percent.. ~ -"- '...., L" ~ -~:~~-- ~.. ~ 50 Yo Water :,,*''" ;.;;;j rf;:;:~~~;~,;~a 50% Clay If this clay costs $1 0 per ton, you are paying $20 per dry ton of clay. \~~~;~~ 25% Water If this clay costs $12 per ton, you are paying $16 per dry ton of clay. 1 For information on sampling and laboratory testing, write to Colorado State University (Clay Sealing Research Project). -8-

Why -With the passing of time, the initial sealing effect will be reduced by erosion, ditch cleaning, tree root penetration, freezing and thawing,

When -Clay material added once a year with the first run of water in the spring or during other high-loss periods insures good penetration into any

Greater or lesser amounts may be needed depending upon how well the original seal has performed.

11 Why -With the passing of time, the initial sealing effect will be reduced by erosion, ditch cleaning, tree root penetration, freezing and thawing, animal burrowing, etc. When -Clay material added once a year with the first run of water in the spring or during other high-loss periods insures good penetration into any leaky zones. How much -Usually 10 percent of the original amount of clay is recommended. Greater or lesser amounts may be needed depending upon how well the original seal has performed. Where -Generally the clay used for the follow-up treatment will be washed in at the upstream end of the treated section. It also may be applied directly to a known leaky section in the form of a blanket. Stockpile follow-up treatment clay at the head-end or other desirable points along the ditch so that it can be added as needed. Stockpiled material is not affected adversely by weather. -9-

Description of ditch Entire length treated-28,660 feet Variable soils--coarse gravel to sandy silt Maximum capacity at tipper end-70 cfs Average wetted perimeter-8 feet Description of installation

12 Description of ditch Entire length treated-28,660 feet Variable soils--coarse gravel to sandy silt Maximum capacity at tipper end-70 cfs Average wetted perimeter-8 feet Description of installation ~p~ Z)ttd - AN EXAMPLE OF THE MULTIPLE-DAM METHOD Date-August 1959 Quantity of bentonite-200 tons in 27 dams concentrated toward upper end. Total area treated-approximately 229,000 square feet Application rate-about 1.75 pounds of bentonite per square foot Total cost-approximately $1,500 Unit cost-6 cents per square yard Results According to Mr. Don Mumma, who is one of the land owners under the ditch, the treatment has extended late summer water supply. The savings for the summers of 1959, l 960 and 1961 are estimated below: Follow-up treatment Spring 1960 and 1961 with first water into ditch (20 tons first spring, 14 tons second spring) Year Est. Acre Ft. 5.00/ AF 5.00/ AF 300@ 1.00* I AF Est. Value 1,500 1, *Wet year value $3,300

13 Sat«ta, bentonite in each dam was piled as high as i: and the water was ponded slowly behind The dam was broken rapidly as the water overtopped it. e thick mixture of bentonite and water flowed down e rocky d itch and was caught behind the next dam. -11-

granite Maximum capacity at upper end-50 cfs Average wetted perimeter-13 feet Description of installation Date-July 27, 1960

per square foot Total cost-$612 Unit cost-11.

14 1()~ Ltde?e«Wt ANOTHER EXAMPLE OF THE MULTIPLE-DAM METHOD Description of ditch Length treated-3,800 feet Ditch material-disintegrated granite Maximum capacity at upper end-50 cfs Average wetted perimeter-13 feet Description of installation Date-July 27, 1960 Quantity of bentonite-37 tons in 15 dams Total area treated-approximately 49,000 square feet Application rate-i V2 pounds per square foot Total cost-$612 Unit cost-11.5 cents per square yard Follow-up treatment 9 tons July 1961 (dry canal) Results Mr. Lester Morris, superintendent at wellington Lakes, estimates that during the first season after sealing (1961 ) approximately 520 acre feet of water were saved by the treatment. This, according to Mr. Morris, was worth about $2,

15 - Each dam consisted of about 2112 tons of bentonite. A small flow of water was introduced. Each dam was broken and the slurry was ponde< hind the next dam. -13-

~ ~ t)ttd - AN EXAMPLE OF A MODIFIED MULTIPLE-DAM METHOD Description of ditch Length treated:_17,500 feet Ditch

produce erosion and damage the bentonite seal).

Application rate-3 pounds per square foot T otal cost-about $3,900 Unit Cost-25 cents per square yard Follow-up

Jim Hoge, manager of one of the ranches under the ditch, the second cutting of hay has been made possible almost

16 ~ ~ t)ttd - AN EXAMPLE OF A MODIFIED MULTIPLE-DAM METHOD Description of ditch Length treated:_17,500 feet Ditch material-cobbles, gravel, and sand Maximum capacity at upper end-15 cfs recommended (flows, greater than 15 cfs may produce erosion and damage the bentonite seal). Description of installation Date-July 1961 Quantity of bentonite-210 tons Total area treated-140,000 square feet Application rate-3 pounds per square foot T otal cost-about $3,900 Unit Cost-25 cents per square yard Follow-up treatment Treatment is planned. Results Late summer water supply has been extended. According to Mr. Jim Hoge, manager of one of the ranches under the ditch, the second cutting of hay has been made possible almost entirely by the bentonite treatment (80 acres of hay worth $1,600). Flume measurements indicate a savings of about 660 acre feet of water to date. The value of the water saved, especially the late summer part, will vary with the season

17 Sealing action was evaluated by flumes wi con ti nu ous recorders. Material was added at the upper end of the ditch. The material mixed readily with the flow to produce a milky slurry. -15-

~ 'Ja,un ~ate/eat AN EXAMPLE OF THE WASH-IN METHOD Description

Maximum capacity-approximately 9 ds Average wetted perimeter-7

bentonite-12 tons in 8 dams Total area treated-9,240 square feet

5 pounds per square foot Total cost-approximately $170 Unit

According to Mr. Willard Hays of the Adolph Coors Co.

the ditch now remains dry during the irrigation season.

18 ~ 'Ja,un ~ate/eat AN EXAMPLE OF THE WASH-IN METHOD Description of ditch Length treated-1,320 feet Ditch material-gravelly sand Maximum capacity-approximately 9 ds Average wetted perimeter-7 feet Description of installation Date-August 1959 Quantity of bentonite-12 tons in 8 dams Total area treated-9,240 square feet Application rate-2.5 pounds per square foot Total cost-approximately $170 Unit cost-17 cents per square yard Follow-up treatment Results According to Mr. Willard Hays of the Adolph Coors Co., the estimated water savings amount to about $560 to date. (See Table below.) Also the previously iim p assable road on the south side of the ditch now remains dry during the irrigation season. I ~ ~ None as yet Est. Year Est. AF Saved Value days (11 4 AF / Day (11 $4.00/ AF days (11 4 AF / Day ( / AF days (Ii 4 AF/ Day (i1 4.00/ AF 160 Total $

- Bentonite was placed in the dry ditch in 1.

19 - Bentonite was placed in the dry ditch in 1.5-ton piles about 160 feet apart A V-ditcher was pulled through the bentonite piles to mix the bentonite into the soil. Closer spacing of piles can reduce the number of passes necessary to obtain satisfactory mixing.

Sealing Leaking Ponds

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