7409.11.40
Page 1 of 4
FOREST SERVICE HANDBOOK
MARK TWAIN NF (REGION 9)
ROLLA, MO
FSH 7409.11 – SANITARY ENGINEERING AND PUBLIC HEALTH HANDBOOK
CHAPTER 40 – DRINKING WATER SYSTEM DESIGN AND CONSTRUCTION
Supplement No.: 7409.11-2009-1
Effective Date: May 18, 2009
Duration: This supplement is effective until superseded or removed.
Approved: DAVID C. WHITTEKIEND
FOREST SUPERVISOR
Date Approved: 05/18/2009
Posting Instructions: Supplements are numbered consecutively by Handbook number and
calendar year. Post by document; remove the entire document and replace it with this
supplement. Retain this transmittal as the first page(s) of this document.
New Document
7409.11-2009-1
4 Pages
Superseded Document(s)
(Supplement Number and
Effective Date)
R9 Mark Twain 7409.11-2003-3
4 Pages
Digest: .
42 - Currency Review – Revises entire chapter. Makes technical and editorial changes
throughout the chapter. -
R9 MARK TWAIN SUPPLEMENT
EFFECTIVE DATE: May 18, 2009
DURATION: Effective until superseded or removed
7409.11.40
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FSH 7409.11 – SANITARY ENGINEERING AND PUBLIC HEALTH HANDBOOK
CHAPTER 40 – DRINKING WATER SYSTEM DESIGN AND CONSTRUCTION
42 – WATER TREATMENT
42.2 – Disinfection.
Disinfection of Wells and Water Systems. Wells and /or water systems shall be disinfected and
retested when any one of the following conditions occur:
-The test on the periodic water sample indicates contamination and two consecutive
samples confirm that water quality is unfit for human consumption (FSM 7421.26, Table 1).
--
Construction of a new well or water system.
--
Repairs made on an existing well or water system.
--
A seasonably operated water system is activated (storage tank and distribution lines shall
be disinfected).
42.21 - Chlorination.
Chlorinating Water Distribution Systems.
1.
Determine amount of water needed to fill all lines and storage tanks to be
chlorinated and allow for an excess of 10% to 20%.
2.
Prepare a chlorine solution of the quantity calculated in Step 1. Determine the
amount of chlorine compound from the chart under Item D (chlorine required for
100 ft. of 6-inch well casing is the same as required for the 150 gallons of water).
3.
Fill all the lines and storage tank with chlorine solution. To insure that all lines
are filled, each water outlet should be opened until water flows freely and chlorine
taste is present in the water (or the water tests 0.5 or more free chlorine).
4.
Let chlorine solution stand in lines and tanks at least 12 hours.
5.
Turn on main water supply. Thoroughly wash all lines and/or tanks until chlorine
taste is gone.
6.
Take water sample and test to insure chlorination was effective.
R9 MARK TWAIN SUPPLEMENT
EFFECTIVE DATE: May 18, 2009
DURATION: Effective until superseded or removed
7409.11.40
Page 3 of 4
FSH 7409.11 – SANITARY ENGINEERING AND PUBLIC HEALTH HANDBOOK
CHAPTER 40 – DRINKING WATER SYSTEM DESIGN AND CONSTRUCTION
Chlorinating Wells.
1.
Determine the amount of chlorine necessary to disinfect the well from the chart
under item D.
2.
Approximately 60% of the required chlorine should be added to the well in the
form of H.T.H. tablets dropped directly into the well.
3.
The Balance of the chlorine shall be in solution and poured into the well. Take
care to thoroughly wet the drop pipe and casing interior with the solution.
Powdered chlorine compounds should be well mixed and allowed to stand for
several minutes; undissolved particles will settle and should not be poured into the
well.
4.
Pump well until a chlorine taste or odor is clearly present in the water (or the
water tests 0.5 ppm or more free chlorine).
5.
Let chlorine solution stand in well for at least 12 hours.
6.
Pump well until chlorine taste is no longer present.
7.
Take water sample and test to insure chlorination was effective.
R9 MARK TWAIN SUPPLEMENT
EFFECTIVE DATE: May 18, 2009
DURATION: Effective until superseded or removed
7409.11.40
Page 4 of 4
FSH 7409.11 – SANITARY ENGINEERING AND PUBLIC HEALTH HANDBOOK
CHAPTER 40 – DRINKING WATER SYSTEM DESIGN AND CONSTRUCTION
Amount of Material Required to Chlorinate Each 100 Feet
Of Water in a 60-Inch Well or Each 150 Gallons of Water
MATERIAL
PERCENT CHLORINE IN
MATERIAL
AMOUNT OF MATERIAL
PUREX OR CHLOROX
(Liquid Laundry)
5¼
0.15 GALLONS
SODIUM HYPOCHLORITE
12
1 CUP
CHLORINATE LIME
POWDER
25
½ CUP
B-K POWDER
50
¼ CUP
H.T.H. OR PERCHLORON
70
1/6 CUP
Notes:
1.
2.
3.
1.16 tablespoons = 1 cup
H.T.H. tablets: Adjust required amount (powdered form) to compensate for table
form (instructions on tablet container).
Powdered forms: Mix with one gallon of water, allow solution to settle, do not pour
undissolved material into well.