02511_Chlorination_and_Dechlorination_2026.pdf

02511-1 2026

STANDARD SPECIFICATIONS

SECTION 02511

CHLORINATION AND DECHLORINATION

PART 1 GENERAL

1.1 DESCRIPTION

A. Section includes requirements for chlorination and dechlorination procedures for water mains.

B. For purposes of this specification, water that has been super chlorinated is considered “wastewater” and all activities associated with the treatment prior to placing the main in service with potable water is also considered wastewater.

C. For purposes of this specification, water discharged into the environment means the discharging of any water to a place other than a sanitary sewer. The environment includes, but is not limited to, storm drains, drainage swales, and/or state waterways.

1.2 QUALITY ASSURANCE

A. Commission employees will collect bacteriological samples and Commission laboratories will perform bacteriological testing for all potable water.

B. Contractor shall collect samples and conduct tests for all treated super chlorinated wastewater or other wastewater discharges to the environment to ensure all discharges made by the contractor are in compliance with all permits, regulations, and laws.

C. Requirements for Contractors before delivery.

1. Contractor shall identify a foreman/crew chief and alternate to complete WSSC

Water Pollution Prevention Plan training. The training will focus on requirements for reporting discharges when working with WSSC and is not a substitute for other training that may be required by other jurisdictional authorities.

1.3 SUBMITTALS

A. Qualifications and Methodology.

1. Qualifications and experience of personnel under whose supervision chlorination or dechlorination is to be performed when using pressurized liquid chlorine described in AWWA B301 or other pressurized chemicals.

2. Method of Construction to include method of chlorination, type and quantity of chemicals, source of water for disinfection, discharge locations of chlorinated water or, if required, method of treating chlorinated water.

3. Method of testing of treated super chlorinated discharges or other waste water created by the contractor which are discharged into the environment. Methods should include the method of testing, the name and address of any laboratories performing field testing as well as the qualifications and experience of personnel

02511-2 2026 for all personnel collecting samples and performing field testing. Methods must be in compliance with all jurisdictional requirements, including but not limited to the permit requirements of MDE permit 17HT and EPA’s - "Guidelines Establishing Test Procedures for the Analysis of Pollutants" (40 CFR 136).

4. Calibration records, maintenance records, and procedures for all monitoring and analytical instrumentation necessary for performing field testing of treated super chlorinated discharges or other wastewater created by the contractor which are discharged into the environment.

B. Test Reports submitted by Contractor.

1. Sampling results at the Commission’s discretion, the contractor may be required to enter information into online system as provided by the Commission.

2. Completed Visual Inspection Form (provided by the Commission) as specified within this specification. At the Commissions discretion, the contractor may be required to enter information into online system as provided by the Commission.

3. Original monitoring data from flow measuring devices or other continuous monitoring instrumentation.

PART 2 PRODUCTS

2.1 MATERIALS: Follow Section 02510, AWWA standards, and specified herein.

A. Dechlorination Tablets: LPD-CHLOR™ Sodium Sulfite, Bio-Max Sodium Sulfite, or VITA-D-CHLOR (ascorbic acid).

B. Bag: 16-inch (top opening) by 8 inch nylon.

C. Diffusers:

1. For flow rates up to 120 gpm: Use 4-inch circular strainer to hold bag with sodium sulfite or ascorbic acid tablets, attach to fire hydrant or fire hose using adapter.

2. For flow rates from 31 to 1250 gpm: Use Pollard LPD-250 or LPD-250A Diffusing

Dechlorinator.

a. Low Flow Inserts: For flow rates from 31 to 200 gpm.

D. Rubber Bands: Heavy duty to fit around nylon bag.

E. Fire Hose: Standard 2 1/2 inch.

F. Adapters: To connect 4-inch circular strainer to fire hydrant or fire hose.

G. End Wall Cap: Threaded for use with standard fire hose.

H. Protection Equipment: See LPD-CHLOR™ tablet Material Safety Data Sheets (MSDS).

I. Chlorine Field Test Kit (Hach Colorimeter).

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PART 3 EXECUTION

3.1 WORK PERFORMED BY THE COMMISSION

A. Take bacteriological samples within 3 working days after receipt of written notification from Contractor that chlorination is complete. Results of sample analysis will be available within 3 calendar days after sampling.

B. Provide Visual Inspection Form.

3.2 CHLORINATION BY CONTRACTOR

A. Notify Engineer 3 working days before performing chlorination and dechlorination, or any wastewater sampling.

1. Provide blow off with sample point at end of each branch and end of main line.

2. All valves including fire hydrant lead valves within chlorinated section to be left open during chlorination.

B. Supply water for disinfection and filling mains from temporary jumper with approved backflow preventer.

1. When no source of water from existing main is available, provide potable water.

2. Pre-flush water source prior to chlorination until water has chlorine residual less than 2.5mg/L or no less than the residual chlorine level of the supply, but not more than 3.5 mg/L, and pH is less than 9.2. If flushing water is discharged to the environment, complete a visual inspection form, at least once daily.

C. Use continuous feed method or tablet method for chlorination following AWWA C651 for disinfecting water mains, except section 4.3.2., and as required herein.

D. Approved Forms of Chlorine: Liquid chlorine, sodium hypochlorite solution, and calcium hypochlorite granules or tablets following AWWA C651.

3.3 CHLORINATION METHODS

A. Continuous Feed Method.

1. Proportion mixture of chlorine solution and water so that minimum of 25 mg/L free chlorine concentration is placed into main and appurtenances to be chlorinated. See table below for guidelines regarding quantity of chlorine needed for initial feed.

2. Retain concentrated chlorinated water in main for 24 hour period.

3. At end of 24 hour period, treated water shall contain no less than 10 mg/L free chlorine throughout main.

4. Notify Engineer in writing in advance if flushing water will be discharged to the environment 96 hours before the start of the discharge.

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5. Flush out main at end of 24 hour period using jumper until water has chlorine residual less than 2.5 mg/L, or no less than the residual chlorine level of the supply, but not more than 3.5 mg/L total chlorine and pH less than 9.2.

6. Preliminary flushing of pipe required by AWWA C651 before chlorination is optional if interior is broom swept or in clean condition, as determined by Contractor.

B. Tablet Method.

1. Do not use this method unless interior of pipe, fittings, and valves can be kept clean and dry.

2. Average Chlorine Dose: Approximately 25 mg/L free chlorine.

3. Seal ends of pipelines that contain tablets or granules to prohibit entry.

4. Notify Engineer in writing in advance if flushing water will be discharged to the environment 96 hours before the start of the discharge.

5. Flush out main at end of 24 hour period using jumper until water has chlorine residual less than 2.5 mg/L or no less than the residual chlorine level of the supply, but not more than 3.5 mg/L, and pH is less than 9.2.

3.4 COMPLETION OF CHLORINATION

A. Notify Engineer in writing when chlorination is complete and ready to have bacteriological samples taken.

CONTINUOUS FEED METHOD

Pipe Diameter (inches)

LENGTH OF PIPE TO BE CHLORINATED

100' 200' 300' 400' 500' 600' 700' 800' 900' 1K 2K 3K 4K 5K 6K 7K

1.5 0.025 0.01 0.016 0.02 0.03 0.033 0.038 0.04 0.05 0.06 0.11 0.16 0.22 0.28 0.33 0.38

2 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.20 0.30 0.40 0.50 0.60 0.70

2.5 0.02 0.03 0.05 0.06 0.08 0.09 0.10 0.12 0.13 0.15 0.30 0.45 0.60 0.75 0.90 1.10

3 0.022 0.04 0.06 0.08 0.10 0.13 0.15 0.16 0.20 0.22 0.43 0.60 0.86 1.10 1.30 1.51

4 0.038 0.07 0.12 0.15 0.20 0.23 0.26 0.30 0.35 0.38 0.76 1.15 1.53 1.92 2.30 2.68

6 0.09 0.18 0.26 0.35 0.45 0.53 0.62 0.70 0.80 0.88 1.77 2.70 3.50 4.40 5.30 6.20

8 0.20 0.30 0.50 0.60 0.80 0.90 1.10 1.20 1.40 1.60 3.10 4.70 6.20 7.80 9.30 10.90

10 0.24 0.48 0.70 1.00 1.20 1.50 1.70 2.00 2.20 2.40 4.90 7.30 9.70 12.20 14.60 17.00

12 0.35 0.70 1.10 1.40 1.80 2.10 2.50 2.80 3.20 3.50 7.00 9.00 14.00 17.50 21.00 24.50

16 0.60 1.30 1.90 2.50 3.10 3.70 4.30 5.00 5.60 6.20

18 0.80 1.60 2.40 3.20 4.00 4.70 5.50 6.30 7.10 7.90

20 1.00 2.00 2.90 3.90 4.90 5.90 6.80 7.80 8.70 9.70

24 1.40 2.80 4.20 5.60 7.00 8.40 9.80 11.20 12.60 14.00 CHART LIST POUNDS OF HTH (70% CHLORINE) TO BE USED TO CHLORINATE GIVEN SIZE PIPE FOR DESIRED PIPE LENGTH.

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B. Should residual and bacteriological analyses not be satisfactory to Engineer, rechlorinate main and notify Engineer in writing when rechlorination is complete and ready to have bacteriological sample taken.

C. Place mains in service when analysis is complete and approved by Engineer.

3.5 DISCHARGING CHLORINATED WATER

A. Methods.

1. Discharge into existing sanitary sewer manholes. This is a preferred option; discharge information and sampling is not required for discharges into sanitary sewers.

a. Maintain minimum 1 foot vertical air gap between end of discharge pipe and manhole frame.

b. Do not cause surcharge or disrupt sewer service.

c. Flow rate into the sanitary sewer may not exceed 0.25 mgd.

1) If flow rate is expected to exceed 0.25 mgd, disposal to sanitary sewer may be possible through coordination with WSSC Water’s Water/Wastewater Systems Assessment Division and/or the appropriate Production Department water resource recovery facility.

2. If a sanitary sewer is not available, an on-site tank or detention pond may be used to hold discharge water until chlorine naturally dissipates or can be treated with dechlorination chemicals.

a. Maintain 12-inches of freeboard above water level in the on-site tank or detention pond to prevent the on-site tank or detention pond from overflowing due to rainfall.

b. Tank or detention pond may not be emptied to the environment until chlorine residual tested within 15 minutes of sample collection from at least 3 representative locations in the tank or pond is non-detectable (<0.10 mg/L) as required by Appendix A (Discharge Category B, Narrative Requirement 2) of the General Discharge Permit, which can be found at https://mde.maryland.gov/programs/Permits/WaterManagementPermits/Documents /GDP-HT-Documents/17HT/17HT-Final-Permit.pdf.

The disinfectant water is still considered to be a wastewater and must be sampled before discharge to the environment, for the substances listed below in section 3.5.B.

3. When sanitary sewers and detention ponds are not available, dechlorinate chlorinated water, or store chlorinated water before discharging as specified below

B. Dechlorination or storage of chlorinated water before discharge.

1. Chemically dechlorinate water or store water until chlorine residual is non-detectable.

2. The discharge must meet all Maryland Department of the Environment (MDE) requirements as specified in General Discharge Permit number 17-HT, Part III.C and Appendix A, Discharge Category B (link included within this specification).

a. Contractor shall collect at least 3 grab samples evenly spaced over course of discharge.

https://mde.maryland.gov/programs/Permits/WaterManagementPermits/Documents/GDP-HT-Documents/17HT/17HT-Final-Permit.pdf https://mde.maryland.gov/programs/Permits/WaterManagementPermits/Documents/GDP-HT-Documents/17HT/17HT-Final-Permit.pdf

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b. Perform field tests to analyze samples for chlorine residual and pH.

c. Chlorine residual: Non-detectable (<0.10 mg/L) in all samples.

d. pH limits: Between 6.0 and 9.0.

e. If water is chemically dechlorinated (alternative to dechlorination tablets), dissolved oxygen (DO) must be measured as well in each of the 3 samples.

f. DO: 5.0 mg/L or greater for discharges to I, I-P, and II waters and 6.0 mg/L or greater for discharges to III, III-P, IV and IV-P waters.

g. Measure flow of the discharge (total volume divided by the duration of discharge).

h. Complete a visual inspection form, at least once daily when discharging to the environment.

i. Submit monitoring results of all chemical parameters to WSSC within 5 working days of completing the discharge, which the Commission will need for quarterly reporting of monitoring results submitted via NetDMR as specified in General Discharge Permit number 17-HT, Part IV.F.

C. Safety Procedures:

1. Commission health and safety programs.

3.6 DISCHARGING POTABLE WATER (0 – 4 milligram per liter [mg/L] Chlorine)

A. Discharge potable water as specified in 3.5 A.

B. When sanitary sewers, tanks, or detention ponds are not available at project site, dechlorinate potable water, store, or discharge specified herein. Contractor to complete a visual inspection form, at least once daily when discharging to the environment.

1. Safety Procedures: LPD-CHLOR™ MSDS and the Commission health and safety programs.

2. To treat flow rates up to 120 gpm: Use fabricated diffuser of 4-inch strainer and adapter.

a. Place 8 tablets in 8-inch by 16 inch (top opening) nylon bag with 4 tablets pushed to each side of bag.

b. Fold bag over tablets, twisting in center.

c. Secure with rubber bands and position firmly inside fabricated diffuser.

d. Estimated time to replenish tablets: 3 days for flows of 1 to 30 gpm and 15 hours for flows of 31 to 120 gpm.

3. To treat flow rates from 31 – 1250 gpm: Use Pollard LPD-250 or LPD-250A

Diffusing Dechlorinator with low flow insert for flow rates from 31-200 gpm.

a. Minimum tablets: 10 for every discharge.

b. Carefully stack tablets in column chamber of LPD unit.

c. Estimated discharge duration for Pollard diffuser.

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Number of Tablets

Estimated Discharge Duration (in hours) that Can Be Treated by the Pollard LPD-250 Low flow (1 – 30 gpm)

Medium flow (31 – 150 gpm)

High flow (151 – 300 gpm)

Very High flow (301 – 1250 gpm)

Do not use for flows < gpm

8 4 1/2 11 9 4-1/2 1/2 12 10 5 1/2 13 10-1/2 5-1/2 1/2 14 11-1/2 6 1/2 15 12-1/2 6 1/2 16 13 6-1/2 1 17 14 7 1 18 15 7-1/2 1 19 16 8 1 20 16-1/2 8 1

4. Number of tablets used during a given discharge: Dependent on various factors such as flow rate and water temperature.

5. Chlorine residual: Non-detectable (<0.10 mg/L)

6. Before being released into the environment, test treated water to assure complete dechlorinization has been achieved. Report sample test results to WSSC within 5 working days.

7. Discharging from fire hydrant:

a. Attach fabricated diffuser directly to either 2 1/2 inch side or 4 inch side of fire hydrant using appropriate adapters or attach 2 1/2 inch hose to 2 1/2 inch side of hydrant and to fabricated diffuser using appropriate adapter.

b. Pollard LPD-250A Diffusing Dechlorinator: Attach directly to 2 1/2 inch side of hydrant or attach 2 1/2 inch hose to hydrant and diffuser.

c. Pollard LPD-250 Diffusing Dechlorinator:

1) Attach to 1 end of 2 1/2 inch hose and attach other end of hose to fire hydrant.

2) Do not attach directly to hydrant.

d. Direct flow so discharge does not cause erosion or disrupt traffic.

8. Discharging from blowoff or pump:

a. Use standard fire hose and appropriate adapters and position diffuser so discharge does not cause erosion, using filter geotextile or tarp when necessary.

b. When discharging from end wall-type blowoffs, replace the standard end wall cap with a modified cap equipped with 2 1/2 inch or 4 inch threaded connection.

3.7 CONNECTION BETWEEN EXISTING AND NEW MAINS

A. Clean and spray or swab new pipe, fittings, and valves with minimum 1 percent solution of chlorine just before installation.

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PART 4 MEASUREMENT AND PAYMENT

4.1 Providing for and complying with requirements in this Section will not be measured for payment, but cost will be considered incidental to Contract.

A. WSSC will not charge the Contractor for water used in support of work covered in this

Specification Section. However, the Contractor is responsible for any equipment needed to transport the water as required by site specific conditions (ex: bypass connections, truck, etc.).

**WSSC**