33 13 00 – DISINFECTION OF WATER UTILITY DISTRIBUTION

Herbert, Rowland & Grubic, Inc. 33 13 00 - 1 009280.0426

SECTION 33 13 00 – DISINFECTION OF WATER UTILITY DISTRIBUTION

PART 1 - GENERAL

1.1 SUMMARY

A. Section Includes:

1. Disinfection of potable water distribution system.

2. Testing and reporting of results.

1.2 REFERENCE STANDARDS

A. American Water Works Association:

1. AWWA B300 - Hypochlorites.

2. AWWA C651 - Disinfecting Water Mains.

1.3 SUBMITTALS

A. Section 01 33 00 – Submittal Procedures: Requirements for submittals.

B. Disinfection Procedure:

1. Submit description of procedure, including type of disinfectant and calculations indicating quantities of disinfectants required to produce specified chlorine concentration.

2. Submit locations of sampling points.

C. Product Data: Submit manufacturer information for proposed chemicals and treatment doses.

D. Certify that the final water complies with disinfectant quality standards of the Owner.

1.4 JOB CONDITIONS:

A. Environmental Requirements:

1. Testing and disinfection of water mains will not be performed if the air temperature is expected to fall below 35o F or as directed by the Owner/Engineer.

1.5 PRODUCT DELIVERY, STORAGE, AND HANDLING

A. Transport, handle and store disinfection products specified herein in a manner recommended by the respective manufacturers to prevent contamination and deterioration of products.

B. When handling disinfection products, due caution is advised. Wear gloves, an apron, goggles, and a suitable vapor mask.

1.6 CLOSEOUT SUBMITTALS

A. Section 01 77 00 – Closeout Procedures: Requirements for submittals.

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B. Disinfection Report: The report should contain the following information:

1. Type and form of disinfectant used.

2. Date and time of disinfectant injection start and completion.

3. Test locations.

4. Name of person collecting samples.

5. Initial and 24-hour disinfectant residuals in treated water in mg/L for each outlet tested.

6. Date and time of flushing start and completion.

7. Disinfectant residual after flushing in mg/L for each outlet tested.

1.7 QUALITY ASSURANCE

A. Perform Work according to AWWA C651.

PART 2 - PRODUCTS

2.1 GENERAL

A. Disinfection chemicals shall be NSF 60 approved/certified.

B. Products in contact with potable water shall be NSF 61 approved/certified.

2.2 DISINFECTION CHEMICALS

A. Chemicals:

1. Sodium hypochlorite: Comply with AWWA B300.

2. Calcium hypochlorite:

a. Comply with AWWA B300.

b. Must contain approximately 65% available chlorine by weight.

c. Use of calcium hypochlorite is not permitted for use to disinfect HDPE pipe.

PART 3 - EXECUTION

3.1 PREVENTIVE AND CORRECTIVE MEASURES DURING CONSTRUCTION

A. The interiors of pipes, fittings, and valves shall be protected from contamination. Prevent surface water runoff from entering trench. Remove visible foreign material or debris.

Minimize soil contamination from equipment:

1. Openings in the pipeline shall be closed with watertight end caps, plugs, or other protective device when pipe laying is stopped at the close of the day’s work or for other reasons. Rodent-proof plugs may be used when watertight plugs are not practicable and when thorough cleaning will be performed by flushing or other means. Maintain coverings until pipes are joined.

2. Pipe delivered for construction shall be strung along the proposed pipe alignment to minimize the entrance of foreign material.

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B. Joints of pipe in the trench shall be completed before work is stopped. If water accumulates in the trench, the plugs shall remain in place until the trench is free of standing water and mud that may enter the pipe.

C. Yarning or packing material shall consist of molded or tubular rubber rings, rope of treated paper, or other approved materials. Materials such as jute or hemp shall not be used. Packing material shall be handled in a manner that avoids contamination.

D. No contaminated material or any material capable of supporting growth of microorganisms shall be used for sealing joints. Sealing material or gaskets shall be handled in a manner that avoids contamination. The lubricant used in the installation of sealing gaskets shall meet the requirements of NSF 61 and shall be free of odors. It shall be delivered to the job in closed containers and shall be kept clean and applied with dedicated, clean applicator brushes.

E. If dirt enters the pipe, it shall be removed, and the interior pipe surface swabbed with a minimum 1 percent free chlorine disinfection solution. If, in the option of the Owner, the dirt remaining in the pipe will not be removed using the flushing operation, the interior of the pipe shall be cleaned using mechanical means in conjunction with the application of a minimum 1 percent (1%) free chlorine disinfecting solution. The cleaning method used shall not force mud or debris into the interior pipe-joint spaces and shall be acceptable to the Owner.

F. If it is not possible to keep the pipe and fittings dry during installation, a scour flush at 3.0 ft/s or greater for a minimum of three pipe volumes followed by continuous-feed chlorination and bacteria testing before release is required.

G. If the main is flooded during construction, it shall be cleared of the floodwater by draining and flushing with potable water until the main is clean. The section exposed to the floodwater shall then be filled with a chlorinated potable water that, at the end of a 24-

hr. holding period, will have a free chlorine residual of not less than 25 mg/L. The chlorinated water may then be drained or flushed from the main. If chemical contamination occurs, the pipe sections exposed to the contamination should be replaced and not reused for potable water applications. After construction is completed, the main shall be disinfected using the continuous-feed method.

3.2 BASIC DISINFECTION PROCEDURE FOR NEW MAINS

A. Inspect materials to be used to ensure their integrity.

B. Prevent contaminating materials from entering the water main during storage, construction, or repair and noting potential contamination at the construction site.

C. Remove, by flushing or other means, those materials that may have entered the water main or appurtenances.

D. Prevent contamination of existing mains from cross-connection during flushing, pressure testing, and disinfection.

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E. Pressure test the water main to ensure that the main meets the allowable leakage rate.

Hydrostatic pressure tests should be conducted with potable water.

F. Chlorinate and adequately document the process used for disinfection:

1. Contractor will chlorinate the pipe and test free chlorine residual levels (must be between 25 and 50 mg/L):

a. Ensure that all valves, hydrants, blowoffs, and other pipeline appurtenances are thoroughly operated so that they maintain sufficient contact with the chlorine solution during the disinfection process.

2. 24-hour hold period.

3. Contractor will test for free chlorine residual. All sampling points must have a minimum residual of 10 mg/L).

G. If test results are acceptable, Contractor will flush the chlorinated water from the main in accordance with AWWA C655. Chlorine residual must be between 1.00 and 3.00 mg/L.

Contractor shall verify acceptable system levels at the end of flushing.

H. Determine the bacteriological quality of water samples collected from the pipe by laboratory test after disinfection. Refer to Paragraph 3.8. Both sets of bacteriological and water quality samples are to be taken by a third-party certified laboratory, at no additional cost to the Owner. Owner and Engineer must approve both sets of test results before the water main can be put into service.

I. Final connection of the newly disinfected water main to the active distribution system without sacrificing sanitary practices and conditions.

3.3 METHODS OF CHLORINATION

A. General: All water mains installed as part of this Work shall be disinfected by chlorination and shall be completed in accordance with AWWA C651.

B. The source of potable water used for disinfection and pressure testing shall be flushed prior to its use to ensure that contaminants or debris are not introduced into the new pipe. Adequate drainage must be provided during flushing. Drainage should take place away from the construction area. During the contact period, the valve isolating the new water main from the existing water system (if applicable) be tagged to prevent unintentional release of the elevated chlorine residual water into the existing water system.

C. Tablet Method:

1. General:

a. The tablet method consists of placing calcium hypochlorite tablets or granules in the water main during installation and then filling the main with potable water to create a chlorine solution with a minimum dose of 25 mg/L but shall not exceed 50 mg/L.

b. This method may be used only if the pipes and appurtenances are kept clean and dry during construction.

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c. This method will not be considered if pre-flushing or hydrostatic testing of the main will be performed before chlorination. However, the method will be considered if hydrostatic testing will be performed concurrent with chlorination.

d. Failure to meet the required minimum residual after a 24-hour hold or failure to obtain satisfactory bacteriological sample results after application of the tablet method will require the Contractor to switch to another available method.

2. Placement of calcium hypochlorite granules during construction: Calcium hypochlorite granules shall be placed at the upstream end of the first section of pipe, at the upstream end of each branch main, and at 500-ft. intervals. The quantities of granules at each location shall be as shown in Table 1.

Table 1: Weight of Calcium Hypochlorite Granules to be Placed at Beginning of Main and at Each 500 Foot Interval for a dose of 25 mg/L

Pipe Diameter (in.) Calcium Hypochlorite Granules

oz. (g)

4 1.7 48 6 3.8 108 8 6.7 190

10 10.5 298 12 15.1 428

3. Placement of calcium hypochlorite tablets during construction: Calcium hypochlorite tablets (5-g) shall be placed in the upstream end of each section of pipe to be disinfected, including branch lines. Also, at least one tablet shall be placed in each hydrant branch and in other appurtenances. Table 2 shows the number of tablets required. Calcium hypochlorite tablets shall be attached by an adhesive meeting the requirements of NSF 61 and used in accordance with the manufacturer’s instructions. There shall be adhesive only on the broadside of the tablet attached to the surface of the pipe. Attach tablets inside and at the top of the main. If the tablets are attached before the pipe section is placed in the trench, their positions shall be marked on the pipe exterior to indicate that the pipe has been installed with the tablets at the top.

Table 2: Number of 5-g Calcium Hypochlorite Tablets Required for Dose of 25 mg/L*

Length of Pipe Section, Ft.

Pipe

Diameter 13 or Less 18 20 40

Inches Number of 5-g Calcium Hypochlorite Tablets 4 1 1 1 1 6 1 1 1 2 8 1 2 2 4

10 2 3 3 5 12 3 4 4 7

*Based on 3.25-g available chlorine per tablet.

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4. Filling: When installation has been completed, the main shall be filled with water such that the full pipe velocity is no greater than 1 ft/s. fill rate must be carefully controlled to ensure tablets do not come loose from pipe or to prevent granules from being washed downstream before being dissolved. Precautions shall be taken to ensure that air pockets are eliminated.

5. Contact time: The chlorinated water shall remain in the pipe for at least 24 hours.

If the water temperature is less than 41 degrees F, the chlorinated water shall remain in the pipe for at least 48 hours. After the holding period in the main, there shall be a free chlorine residual of not less than 10 mg/L at each sampling point.

D. Continuous-Feed Method:

1. General:

a. The main should undergo hydrostatic testing before disinfection, if practical.

b. The continuous-feed method consists of completely filling the main with potable water, removing air pockets, flushing the completed main to remove particulates, and refilling the main with potable water that has been chlorinated to a minimum dose of 25 mg/L but shall not exceed 50 mg/L.

c. After a 24-hour holding period in the main, there shall be a free chlorine residual of not less than 10 mg/L.

2. Preliminary flushing: Before the main is chlorinated, it shall be filled with potable water to eliminate air pockets and flushed to remove particulates. The flushing velocity in the main shall not be less than 3.0 ft./sec. Table 3 shows the rates of flow required to produce a velocity of 3.0 ft/s.

Table 3: Required flow and openings to flush pipelines at 3.0 ft/s

Pipe Diameter

Flow Required to Produce 3.0 ft/s Velocity in Main

Size of Tap Used, in.

Number of Hydrant Outlets

1 1-1/2 2

in. gpm Number of Taps Required on Pipe 2-1/2 in. 4-1/2 in.

4 120 1 - - 1 1 6 260 - 1 - 1 1 8 470 - 2 - 1 1

10 730 - 3 2 1 1 12 1060 - - 3 2 1

* With a 40-psi pressure in the main with the hydrant flowing to atmosphere

3. Procedure For Chlorinating the Main:

a. Water supplied to the existing distribution system shall flow at a constant, measured rate into the newly installed water main. The main shall undergo hydrostatic testing prior to disinfection.

Herbert, Rowland & Grubic, Inc. 33 13 00 - 7 009280.0426

b. At a point not more than 10 feet downstream from the beginning of the new main, water entering the new main shall receive a dose of chlorine fed at a constant rate such that the water will have not less than 25 mg/L free chlorine concentration. To ensure that an appropriate concentration is achieved, the free chlorine concentration shall be measured at regular time intervals in accordance with the procedures described in the current edition of Standard Methods for the Examination of Water and Wastewater or AWWA M12 or using appropriate chlorine test kits. Table 4 gives the amount of chlorine required for each 100 ft. of pipe. Solutions with a minimum 1 percent chlorine concentration may be prepared with sodium hypochlorite or calcium hypochlorite. The latter solution requires 1 lb of calcium hypochlorite in 8 gal of water.

Table 4: Chlorine required to produce an initial 25-mg/L dose in 100 ft of pipe by diameter

Pipe Diameter 100% Chlorine 1% Chlorine Solution

in. lb (g) Gal 4 0.013 (5.9) 0.16 6 0.030 (13.6) 0.36 8 0.054 (24.5) 0.65

10 0.085 (38.6) 1.02 12 0.120 (54.4) 1.44

c. Chlorine application shall not cease until the entire main is filled with chlorinated water at a minimum dose of 25 mg/L. The chlorinated water shall be retained in the main for at least 24 hours, during which time valves and hydrants in the treated section shall be operated to ensure disinfection of the appurtenances. At the end of this 24-hour period, the treated water in all portions of the main shall have a residual of not less than 10 mg/L of free chlorine.

3.4 FINAL FLUSHING

A. After the applicable retention period, heavily chlorinated water should not remain in prolonged contact with pipe. In order to prevent damage to the pipe lining or prevent corrosion damage to the pipe itself, the heavily chlorinated water shall be flushed from the main, fittings, valves, and branches, or taps in the main installed at the Contractors expense, until chlorine measurements show that the concentration in the water leaving the main is no higher than that generally prevailing in the existing distribution system or that is acceptable for domestic use.

B. The environment to which the chlorinated water is to be discharged shall be inspected. If there is any possibility that the chlorinate discharge will cause damage to the environment, a neutralizing chemical shall be applied to the water to be discharged to thoroughly neutralize the residual chlorine. When necessary, federal, state, or local regulatory agencies should be contacted to determine special provisions for the disposal of heavily chlorinated water.

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C. All work involving chlorinated water discharges to the surface, such as but not limited to flushing of water mains and hydrants, water system disinfection, and hydrostatic testing shall be dechlorinated in accordance with PADEP regulations pertaining to the Planned and Unplanned Discharges of Chlorinated Waters to Surface Waters.

3.5 FINAL CONNECTION TO EXISTING MAINS

A. Water mains must be completely installed, flushed, disinfected, and satisfactory bacteriological sample results received prior to making permanent connections to the active distribution system. Sanitary construction practices must be followed during installation of the final connection so that there is no contamination of the new or existing water main with foreign material or groundwater:

1. Connections equal to or less than one pipe length (≤20 ft): Th new pipe, fittings, and valve(s) for the connection may be spray disinfect or swabbed with a minimum 1 percent solution of chlorine just before being installed if the total length of the connection from the end of a new main to the existing main is equal to or less than 20 ft.

2. Connections greater than one pipe length (generally >20 ft): The pipe required for connection must be set up aboveground and disinfected with bacteriological samples taken if the total length of the connection from the end of a new main to the existing main is greater than 20 ft. After satisfactory bacteriological sample results have been received for the predisinfected pipe, the pipe can be used in connecting the new main to the active distribution system. Between the time the satisfactory bacteriological sample results are received and the time that the connection piping is installed, the ends of the piping must be sealed with plastic wraps, watertight plugs, or caps.

3.6 DISINFECTION PROCEDURES WHEN CUTTING INTO EXISTING MAINS

A. Controlled pipe connection with depressurization after shutdown:

1. In this situation, after the repair site has been exposed and secured from trench soil/water contamination, the water main is depressurized by a shutdown to complete the repair. The repair site should be cleaned and disinfected by spraying or swabbing with a minimum 1 percent chlorine solution. The water main is then returned to service with flushing to scour the pipe and obtain three volumes of water turnover, making sure that the flushed water is visually clear. It is advisable to check for a typical system chlorine residual and, if it is not found, to continue flushing until residuals are restored to levels maintained in the distribution system by the Owner.

B. When the existing pipe has to be opened and the interior surfaces of the water system exposed to the environment, the following additional procedures need to be followed:

1. The existing pipe should be inspected and cleaned, utilizing flushing water into the trench where possible until the flush water runs visually clear.

2. The repair site should be accessible, and the trench adequately dewatered so that the repair site can be cleaned and disinfected by spraying or swabbing with a minimum 1 percent chlorine solution.

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3. Additionally, any accessible upstream and downstream interior of the existing pipe should be disinfected by swabbing or spraying with a minimum 1 percent chlorine solution.

4. The water main may then be returned to service after flushing to scour the pipe and obtain three volumes of water turnover. The flushed water should run visually clear, have a measurable chlorine residual if the system operates with a residual, and be checked with bacteriological testing. The pipeline may be returned to service before obtaining bacteriological results.

3.7 TEMPORARY SERVICE LINES

A. Temporary water service lines to customers during main repair activities shall be disinfected before use. Materials shall meet the NSF 61 certification for potable water use. Disinfection should be accomplished by the procedures in Paragraph 3.3 followed by scour flushing at 3.0 ft/s or greater for a minimum of three pipe volumes (see Table 3), or until the water runs visually clear and preferably a measurable chlorine residual is restored.

3.8 SAMPLING

A. Sampling procedure:

1. Samples for bacteriological analysis shall be collected in sterile bottles treated with sodium thiosulfate, in accordance with Section 9060 – Samples of Standard Methods for the Examination of Water and Wastewater.

2. Contractor is required to receive approval from the Owner and Engineer if they desire to use a fire hydrant for the collection of samples:

a. If approved, cleaned fire hydrants that have been cleared of standing water and/or other sanitized sampling apparatus may be used.

3. There should be no water in the trench up to the connection for sampling. The sampling pipe must be dedicated, clean, disinfected, and flushed before sampling. A corporation cock may be installed in the main with a copper-tube gooseneck assembly. After samples have been collected, the gooseneck assembly should be removed, and the corporation cock should be capped. Sample corporation cocks shall be placed in the 2 o’clock or 10 o’clock position.

B. At least one set of samples shall be collected from every 1,200 feet of the new water main, plus one set from each end of the line, including the injection site, and at least one set from each branch, greater than one pipe length. Chlorine residual and bacteriological sample requirements must be met at all designated sample locations.

C. After disinfection and final flushing such that typical system chlorine residuals are present, samples shall be collected as follows. For new mains, the Contractor has two options for the bacteriological testing for total coliform analysis:

1. Option A: Before approving a main for release, take an initial set of samples and then resample again after a minimum of 16 hours using the sampling site procedures outlines. Both sets of samples must pass for the main to be approved for release.

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2. Option B: Before approving a main for release, let it sit for a minimum of 16 hours without any water use. Then collect, using the sampling site procedures outlined and without flushing the main, two sets of samples a minimum of 15 minutes apart while the sampling taps are left running. Both sets of samples must pass for the main to be approved for release.

D. Sampling results:

1. Samples shall be tested for bacteriological quality in accordance with Standard

Methods for the Examination of Water and Wastewater and shall show the absence of total coliform bacteria and E.coli.

E. If trench water has entered the new main during construction or if excessive quantities of dirt or debris have entered the new main, bacteriological samples shall be taken at intervals of approximately 200 feet, at locations coordinated with the Owner and Engineer. Samples shall be taken of water that has stood in the new main for at least 16 hours after final flushing has been completed.

F. If sample results from the lab indicate a measured HPC greater than 500 colony-forming units (cfu) per mL, flushing should resume (and redisinfection if required by the Owner and Engineer) and another set of HPC and coliform samples collected until no coliform are present and the HPC is less than 500 CFU/mL.

G. The record of compliance shall be the bacteriological test results certifying that the water sampled from the new water main is free of coliform bacteria contamination and is equal to or better than the bacteriologic water quality in the distribution system.

H. If the water main is not promptly put into service, the Owner and Engineer will evaluate to determine if the water quality may have been impacted and if additional testing and further action, such as but not limited to flushing and redisinfection, is warranted at no additional cost to the Owner.

3.9 REDISINFECTION

A. If the initial disinfection fails to produce satisfactory bacteriological results or if other results indicate unacceptable water quality, the main may be reflushed and then shall be resampled. If check samples also fail to produce acceptable results, the main shall be rechlorinated by the continuous-feed method until satisfactory results are obtained.

END OF SECTION 33 13 00