Guidance Manua pdf

 

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water (ca. 1:10 dilution) is necessary prior to application.  When Earthtec solution is 

added into the canal at one site, effective concentrations of copper (0.2-0.4 mg/l) may 

extend 5 to 6 miles downstream.  

5.3.1.4 

Calculation of Earthtec Dosing 

 

Prior to treatment it is important to accurately determine water flow rates.  Such data 

may be available from SRP headquarters.  If not, it may be necessary to estimate flow in 

the field.  To do this, estimate velocity by measuring off a short distance along the canal 

(e.g., 50 feet).  Then drop a floating object at the upper end of the measured section and 

record the time it takes for the object to reach the lower end of the section in seconds.  

The velocity is the distance traveled divided by the travel time.  The measurement should 

be repeated three times.  Flow may be calculated as follows: 

 

Flow, cfs = average width (feet) x average depth (feet) x velocity (feet/second) x 0.9  

 

Equation 5.3 

 

The amount of Earthtec needed to maintain the drip rate for a defined period of time can 

be calculated using the following formula:  

 

Drip rate (L/min) = 1699 L/min/cfs x Canal flow (cfs) x Targeted concentration in canal 

÷

 

Earthtec concentration 

Equation 5.4 

 

Where: Canal flow = CFS estimated with previous formula; Targeted concentration = 0.2-

0.5 mg/l; Earthtec concentration = 60,000 mg/l

.  

 

 

5.3.1.5 

Initial and Prolonged Treatment Effectiveness Interval 

 

The initial copper application may be applied to the canal system in early summer (June 

or July) when the growth of blue-green algae mats begins to accelerate and MIB 

concentrations approach 10 ng/L.  

 

Re-treatment of a canal section is necessary  when significant re-growth of blue-green 

algae mats begins to appear on the surfaces of the submerged canal walls. A four-week 

interval between consecutive treatments is usually sufficient.  Copper treatments appear 

to have an effective treatment length of about 5 to 6 miles. 

 

5.3.1.6 

Operational Issues  

 

A 2- to 3-day advance notice is required for the SRP crew to prepare for copper 

application.  Copper should be ordered by SRP two to four weeks prior to June to ensure 

its availability for application. 

 

 

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A 

B 

C 

D 

5.3.2  Canal Wall Brushing 

5.3.2.1 

Principle of Canal Wall Brushing 

 

The biological basis of canal wall brushing rests on the fact that most, if not all, T&O 

culprit organisms are periphyton, growing along with other microorganisms in microbial 

mats attached to the canal walls.  Although exact reasons are unknown, the culprit 

species usually exhibit slower growth rates compared to many non-producers, and thus 

represent minor populations within a complex microbial community.  Removing microbial 

mats from the canal walls by physical means, such as brushing, has proved to be an 

effective approach to prevent culprit organisms from proliferating, and to reduce the 

production of MIB and geosmin.  Microbial mats removed from the canal walls and 

floating downstream did not cause significant spikes of MIB/geosmin concentration at 

downstream sites.  

 

5.3.2.2 

Method of Canal Wall Brushing 

 

Brushing can be conducted by a SRP tractor-mounted custom-designed revolving metal 

brush, which measures 150 cm long and 80 cm in diameter and is operated at 60 rpm. 

An operator can clean both sides of the canal at a rate of about 1 to 2 miles/day (Figure 

5-5). 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 5-5.  Mechanical Brushing Arizona Canal walls with custom designed device developed by SRP (A, 

B).  Canal wall with algae mats before brushing (C) and canal wall without algae mats after 

brushing (D). 

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5.3.2.3 

Initial and Prolonged Effectiveness 

 

As with copper treatment, the initial brushing event should take place when periphyton 

appear as thin blue-green mats on the submerged canal walls.  This usually occurs in 

early summer months (June to July).  Brushing should be conducted on both sides of the 

canal, starting from the upper end of a treated section.  Some 70-80% of periphyton 

biomass may be removed from the canal walls by brushing, resulting in reduced 

production of MIB and geosmin.  

 

Periodic brushing will be needed to ensure the maximum effectiveness of the treatment. 

A recommended time interval between consecutive treatments is two to three weeks. 

 

5.3.2.4 

Limitations of Brushing 

 

There are a number of physical limitations to the brushing technique.  Brushing is not 

effective in canal sections where water depth is low (2 to 4 feet).  Brushing is also difficult 

at the head of the canal, where water velocities are high.  Water flowing at high velocity 

makes it difficult to maneuver the brush effectively because of the drag forces generated. 

Canal sections with elevated banks also make it impossible to reach the canal walls with 

the brushing arm.   For this reason, brushing cannot be done effectively at the upper end 

of the Arizona Canal. 

 

For canal brushing, two weeks advance reservation notice to SRP is required. Since a 

brushing unit can brush only 1 to 2 miles per day, the brushing procedure may be time-

consuming if large reaches of the canal are to be treated. 

 

5.3.3  Identification of hotspots 

 

It is critical to identify MIB/geosmin production hotspots and, ideally, hotspots of the 

culprit organisms along the canal system in order to maximize the effectiveness and 

efficiency of copper treatment and canal wall brushing.  Two reoccurring hotspots have 

been identified along the Arizona Canal: 

• 

between the Beeline Highway and Mesa Drive (Figure 5-6) 

• 

between the Squaw Peak and Deer Valley WTPs (Figure 5-7) 

 

Hotspots can be readily identified by weekly sampling along the length of the Arizona 

Canal and analysis for MIB/geosmin concentrations.  Rapid increases in MIB/geosmin 

over relatively short canal stretches represents “hotspots” of production. 

 

 

 

 

 

 

 

 

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