Groundwater Math Math for Water Technology MTH 082 Lecture 2 Well Drawdown, Well yield, Specific...

Groundwater MathGroundwater MathMath for Water Technology

MTH 082

Lecture 2

Well Drawdown, Well yield, Specific Capacity, Well Disinfection

Course Reader Week 2

Chapter 8 Water Sources and Storage (Price).

Well Casing Disinfection (Pg 174-177)

Oregon Department of Human Services

Coliform Bacteria and Well Disinfection

Disinfection Section 02675. AWWA

Oregon State University. How To Disinfect A Well and Water System

Math for Water TechnologyMTH 082

Lecture 2

Well Drawdown, Well yield, Specific Capacity, Well Disinfection

Course Reader Week 2

Chapter 8 Water Sources and Storage (Price).

Well Casing Disinfection (Pg 174-177)

Oregon Department of Human Services

Coliform Bacteria and Well Disinfection

Disinfection Section 02675. AWWA

Oregon State University. How To Disinfect A Well and Water System

ObjectivesObjectives

1. Well Drawdown (static and pumping water levels)

2. Well Yield (drawdown test)

3. Specific Capacity

4. Well disinfection

1. Well Drawdown (static and pumping water levels)

2. Well Yield (drawdown test)

3. Specific Capacity

4. Well disinfection

Reading assignment: Chapter 8 Water Sources and Storage (Price). Well Casing Disinfection (Pg 174-177)Oregon Department of Human Services Coliform Bacteria and Well DisinfectionDisinfection Section 02675. AWWA Oregon State University. How To Disinfect A Well and Water System

Reading assignment: Chapter 8 Water Sources and Storage (Price). Well Casing Disinfection (Pg 174-177)Oregon Department of Human Services Coliform Bacteria and Well DisinfectionDisinfection Section 02675. AWWA Oregon State University. How To Disinfect A Well and Water System

Well ProblemsWell Problems• Drawdown ft = pumping water level – static water level ft

• Well yield = Flow gallons

duration of Test, min

-small wells = (gpm, gph) Large wells= (ft3/sec or m3/sec)

• Specific capacity, gpm/ft = (Well yield gpm) (Drawdown ft)

• Well casing disinfection

lbs= (dose mg/L Cl2)(water in well casing MG)(8.34 lb/gal)

Chlorine lbs = chlorine lbs

% available chlorine

100

• Drawdown ft = pumping water level – static water level ft

• Well yield = Flow gallons

duration of Test, min

-small wells = (gpm, gph) Large wells= (ft3/sec or m3/sec)


• Well casing disinfection




100

Static H2O TableStatic H2O Table

Well screenGravel Pack

Grout Sealminimum 10 ft

Drawdown

Pumping water levelCone of Depression

Well casing

Submersible Well pump

Well slab

Sanitary SealSanitary Seal

Pump House1. Electricity 2. Disinfection

Given

Formula

Solve:

Given

Formula

Solve:

The static water level for a well is 89 ft. If the pumping water level is 97 ft, what is

the well drawdown??

The static water level for a well is 89 ft. If the pumping water level is 97 ft, what is

the well drawdown??

186

ft -8

ft 8

ft 9

7 ft

25% 25%25%25%

Static WL= 89 ft, Pumped WL=97 ft

Drawdown ft = pumping water level – static water level ft

Drawdown = 97 ft- 89 ftDrawdown = 8 ft




1. 186 ft

2. -8 ft

3. 8 ft

4. 97 ft

1. 186 ft

2. -8 ft

3. 8 ft

4. 97 ft

Given

Formula

Solve:

Given

Formula

Solve:

Before the pump is started the water level is measured at 140 ft. The pump is then started. If the pumping water level is determined to be 167 ft, what is the

drawdown in ft?

Before the pump is started the water level is measured at 140 ft. The pump is then started. If the pumping water level is determined to be 167 ft, what is the

drawdown in ft?

307

ft

-27

ft 2

7 ft

0 ft

0% 0%

83%

17%







1. 307 ft

2. -27 ft

3. 27 ft

4. 0 ft

1. 307 ft

2. -27 ft

3. 27 ft

4. 0 ft

Given

Formula

Solve:

Given

Formula

Solve:

The static water level for a well is 105 ft. If the pumping water level is 128 ft, what

is the well drawdown??

The static water level for a well is 105 ft. If the pumping water level is 128 ft, what

is the well drawdown??

133

ft

128

ft 2

3 ft

105

ft

25% 25%25%25%







1. 133 ft

2. 128 ft

3. 23 ft

4. 105 ft

1. 133 ft

2. 128 ft

3. 23 ft

4. 105 ft

Given

Formula

Solve:

Given

Formula

Solve:

A sounding line is used to determine the static water level in a well. The air

pressure applied is 4.5 psi and the length of the sounding line is 150 ft. If the

pumping water level is 168 ft, what is the drawdown?

A sounding line is used to determine the static water level in a well. The air

pressure applied is 4.5 psi and the length of the sounding line is 150 ft. If the

pumping water level is 168 ft, what is the drawdown?

168

ft

28.

4 ft

139

ft 1

8 ft

25% 25%25%25%

Static WL= ? ft, Pumped WL= ft 4.5 psi (2.31 ft/1 psi) = 10.4 ft

WL in well ft = length of sounding line,ft– Water depth in sounding line, ftWL in well ft =150 ft- 10.4 ftWL in well ft = 139 ft

Drawdown = 168 ft-139.6 ft = 28.4 ft

Static WL= ? ft, Pumped WL= ft 4.5 psi (2.31 ft/1 psi) = 10.4 ft

WL in well ft = length of sounding line,ft– Water depth in sounding line, ftWL in well ft =150 ft- 10.4 ftWL in well ft = 139 ft

Drawdown = 168 ft-139.6 ft = 28.4 ft1. 168 ft

2. 28.4 ft

3. 139 ft

4. 18 ft

1. 168 ft

2. 28.4 ft

3. 139 ft

4. 18 ft

H2O TableH2O TableDepth to WaterDepth to Water

(hp) Pressure Head: pressure (density )(gravity)

(hp) Pressure Head: pressure (density )(gravity)

Total Head (h):

(z) + pressure

(density )(gravity)

Total Head (h):

(z) + pressure

(density )(gravity)Z = elevation of base of piezometer above or below some datum (Sea Level)

Z = elevation of base of piezometer above or below some datum (Sea Level)

Depth of Piezometer Depth of Piezometer

Fluid Pressure Practice ProblemFluid Pressure Practice ProblemA B CA B C

Elevation at surface (m) 225 225 225Depth of Piezometer (m) 150 100 75Depth to water 80 77 60(m below surface)

Elevation at surface (m) 225 225 225Depth of Piezometer (m) 150 100 75Depth to water 80 77 60(m below surface)

What is hydraulic head at A, B, C?=elev. of H20 in piezometer

What is pressure head at A, B, C?=height of H20 above piezometer

What is elevation head at A, B, C?=height @ BOTTOM of piezometer (ABOVE/BELOW REFERENCE)

What is hydraulic head at A, B, C?=elev. of H20 in piezometer

What is pressure head at A, B, C?=height of H20 above piezometer

What is elevation head at A, B, C?=height @ BOTTOM of piezometer (ABOVE/BELOW REFERENCE)

Hydraulic HeadPressure HeadElevation Head

Hydraulic HeadPressure HeadElevation Head

145 148 16570 23 1575 125 150

Well YieldWell Yield• Well Yield: Is the rate of water withdrawal that a well

can supply over a long period of time.

• Well yield = Flow gallons duration of Test, min

Small wells = (gpm, gph)

Large wells= (ft3/sec or m3/sec)In the U.S. most building or health departments who must approve a private well

water supply when issuing a final certificate of occupancy for new construction want to see 3 to *5* gallons per minute or 3-5 gpm.

• Well Yield: Is the rate of water withdrawal that a well can supply over a long period of time.

• Well yield = Flow gallons duration of Test, min

Small wells = (gpm, gph)

Large wells= (ft3/sec or m3/sec)In the U.S. most building or health departments who must approve a private well

water supply when issuing a final certificate of occupancy for new construction want to see 3 to *5* gallons per minute or 3-5 gpm.

Given

Formula

Solve:

Given

Formula

Solve:

During a five minute test for well yield, a total of 740 gallons are removed from the

well. What is the well yield in gpm?

During a five minute test for well yield, a total of 740 gallons are removed from the

well. What is the well yield in gpm?

67

gpm

148

gpm

370

0 gpm

0 g

pm

8%0%0%

92%

total = 740 gal, time = 5 minutes

Well yield = Flow gallons Duration of Test, min

Well yield = 740 gallons = 148 gpm 5 min



Well yield = 740 gallons = 148 gpm 5 min 1. 67 gpm

2. 148 gpm

3. 3700 gpm

4. 0 gpm

1. 67 gpm

2. 148 gpm

3. 3700 gpm

4. 0 gpm

Given

Formula

Solve:

Given

Formula

Solve:

During a test for well yield, a total of 835 gallons were pumped from the well. If

the well yield test lasted 5 minutes, what was the well yield in gph?

During a test for well yield, a total of 835 gallons were pumped from the well. If

the well yield test lasted 5 minutes, what was the well yield in gph?

148

gph

835

gph

417

5 gpm

10,

020

gph

25% 25%25%25%



Well yield =835 gallons = 167 gpm (60 min/1 hr) = 10,020 gph 5 min



Well yield =835 gallons = 167 gpm (60 min/1 hr) = 10,020 gph 5 min 1. 148 gph

2. 835 gph

3. 4175 gpm

4. 10,020 gph

1. 148 gph

2. 835 gph

3. 4175 gpm

4. 10,020 gph

Specific CapacitySpecific Capacity• Specific Capacity: Is the rate of well yield

per unit of drawdown.


• Specific Capacity: Is the rate of well yield per unit of drawdown.


Given

Formula

Solve:

Given

Formula

Solve:

It was determined that a well had a yield of 200 gpm after 25 ft of drawdown, What

is the wells specific capacity?

It was determined that a well had a yield of 200 gpm after 25 ft of drawdown, What

is the wells specific capacity?

15

gpm

per

1 f.

..

25

gpm

per

1 f.

..

200

gpm

per

1 ..

.

8 g

pm p

er 1

ft...

25% 25%25%25%

Well yield = 200 gpm Drawdown=25 ft

Specific Capacity = Well Yield (gpm) Drawdown (ft)

SC = 200 gpm = 8 gpm per 1 ft drawdown 25 ft

Well yield = 200 gpm Drawdown=25 ft


SC = 200 gpm = 8 gpm per 1 ft drawdown 25 ft 1. 15 gpm per 1 ft of drawdown

2. 25 gpm per 1 ft of drawdown







Given

Formula

Solve:

Given

Formula

Solve:

A well produces 1000 gpm, If the drawdown was 38.2 ft, what is the wells

specific capacity in gpm/ft?

A well produces 1000 gpm, If the drawdown was 38.2 ft, what is the wells

specific capacity in gpm/ft?

100

0 gpm

/ft

38.

2 gpm

/ft

26.

2 gpm

/ft

382

0 gpm

/ft

25% 25%25%25%

Well yield = 1000 gpm Drawdown=38.2 ft


SC = 1000 gpm = 26.2 gpm/ft 38.2 ft

Well yield = 1000 gpm Drawdown=38.2 ft


SC = 1000 gpm = 26.2 gpm/ft 38.2 ft 1. 1000 gpm/ft

2. 38.2 gpm/ft

3. 26.2 gpm/ft

4. 3820 gpm/ft

1. 1000 gpm/ft

2. 38.2 gpm/ft

3. 26.2 gpm/ft

4. 3820 gpm/ft

Well DisinfectionWell DisinfectionNew Wells: Well casing disinfection


Well casing Volume:( 0.785)(Diameter)(Diamter)(length)

Volume: ft3 to gallons (7.48 gal/1 ft3)

Volume: (1 gal) (1MG/1,000,000 gal)

NEW WELLS*****50 mg/L******

EXISTING WELLS*****100 mg/L



100

New Wells: Well casing disinfection


Well casing Volume:( 0.785)(Diameter)(Diamter)(length)

Volume: ft3 to gallons (7.48 gal/1 ft3)

Volume: (1 gal) (1MG/1,000,000 gal)

NEW WELLS*****50 mg/L******

EXISTING WELLS*****100 mg/L



100

What is the purpose of surging?What is the purpose of surging?

1. To clean mineral deposits from well screens.

2. To remove blockages from the distribution system.

3. To backwash filters rapidly.

4. To prepare pump motors for erratic power supplies.

1. To clean mineral deposits from well screens.

2. To remove blockages from the distribution system.

3. To backwash filters rapidly.

4. To prepare pump motors for erratic power supplies.

A new well has been disinfected according to the standard operating procedure, but a fecal

coliform sample taken after disinfection still

shows colony growth. The operator should

A new well has been disinfected according to the standard operating procedure, but a fecal

coliform sample taken after disinfection still

shows colony growth. The operator should

Dis

infe

ct th

e ...

Pla

ce th

e wel

l...

Pla

ce th

e wel

l...

Aban

don the

we.

..

25% 25%25%25%

1. Disinfect the well again without skipping any steps.

2. Place the well into service anyway. It will be fine after a couple of hours.

3. Place the well into service, but maintain twice the normal residual chlorine concentration for a few days.

4. Abandon the well. If it isn't clean now, it never will be.

1. Disinfect the well again without skipping any steps.

2. Place the well into service anyway. It will be fine after a couple of hours.

3. Place the well into service, but maintain twice the normal residual chlorine concentration for a few days.

4. Abandon the well. If it isn't clean now, it never will be.

Chlorine is an effective treatment for well screens. It helps to

remove this material.

Chlorine is an effective treatment for well screens. It helps to

remove this material.

Slim

e fro

m ir

o...

Bio

film

s fro

m ..

.

Iron a

nd m

anga.

..

Cal

cium

car

bon...

25% 25%25%25%

1. Slime from iron-oxidizing bacteria

2. Biofilms from ammonia-oxidizing bacteria

3. Iron and manganese oxides

4. Calcium carbonate deposits

1. Slime from iron-oxidizing bacteria

2. Biofilms from ammonia-oxidizing bacteria

3. Iron and manganese oxides

4. Calcium carbonate deposits

What concentration of residual chlorine should be maintained

for 24 hours in a newly constructed well?

What concentration of residual chlorine should be maintained

for 24 hours in a newly constructed well?

50

mg/L

50

ug/L

25

mg/L

25

ug/L

25% 25%25%25%

1. 50 mg/L

2. 50 ug/L

3. 25 mg/L

4. 25 ug/L

1. 50 mg/L

2. 50 ug/L

3. 25 mg/L

4. 25 ug/L

After a routine repair to an existing well, how much chlorine residual is required in the well to ensure adequate disinfection?

After a routine repair to an existing well, how much chlorine residual is required in the well to ensure adequate disinfection?

100

mg/L

200

mg/L

400

mg/L

100

0 m

g/L

25% 25%25%25%

1. 100 mg/L

2. 200 mg/L

3. 400 mg/L

4. 1000 mg/L

1. 100 mg/L

2. 200 mg/L

3. 400 mg/L

4. 1000 mg/L

Given

Formula

Solve:

Given

Formula

Solve:

A well casing contains 550 gal of water. If 0.5 lbs of chlorine were used in the disinfection, what was the

chlorine dosage in mg/L?

A well casing contains 550 gal of water. If 0.5 lbs of chlorine were used in the disinfection, what was the

chlorine dosage in mg/L?

120

9 m

g/L

109

mg/L

1 m

g/L

0. 5

mg/L

25% 25%25%25%

550 gal = 0.000550 MGLbs/day= (mg/L)(MG)(8.34 lb/gal)

0.5 Lbs/day= (X mg/L)(.000550 MG)(8.34 lb/gal) X= 0.5/(0.00050 MG)(8.34)X= 109 mg/L

1. 1209 mg/L

2. 109 mg/L

3. 1 mg/L

4. 0. 5 mg/L

1. 1209 mg/L

2. 109 mg/L

3. 1 mg/L

4. 0. 5 mg/L

MINDBENDERS!MINDBENDERS!• Proceed at your Own RISK• Proceed at your Own RISK

Given

Formula

Solve:

Given

Formula

Solve:

A new well is to be disinfected with chlorine at a dosage of 50 mg/L. If the well casing diameter is 6

inches and the length of the water filled casing is 120 ft, how many lbs of chlorine will be required?

A new well is to be disinfected with chlorine at a dosage of 50 mg/L. If the well casing diameter is 6

inches and the length of the water filled casing is 120 ft, how many lbs of chlorine will be required?

2 lb

s

0.0

7 lb

s

5.7

0 lb

s

1.7

0 lb

s

25% 25%25%25%

D=6 in=0.5 ft Well =120 ft220 ft - 100 ft = 120 ft water in well(0.785)(D2)(H) = ft3

(mg/L)(MG)(8.34 lb/gal)

(0.785)(0.5 ft)(0.5 ft) (120 ft)(7.48 gal/ft3)= 176 gal(50 mg/L)(.000176 MG)(8.34 lb/gal)= 0.07

D=6 in=0.5 ft Well =120 ft220 ft - 100 ft = 120 ft water in well(0.785)(D2)(H) = ft3

(mg/L)(MG)(8.34 lb/gal)

(0.785)(0.5 ft)(0.5 ft) (120 ft)(7.48 gal/ft3)= 176 gal(50 mg/L)(.000176 MG)(8.34 lb/gal)= 0.07

1. 2 lbs

2. 0.07 lbs

3. 5.70 lbs

4. 1.70 lbs

1. 2 lbs

2. 0.07 lbs

3. 5.70 lbs

4. 1.70 lbs

Given

Formula

Solve:

Given

Formula

Solve:

How many lbs of calcium hypochlorite (65% available chlorine) is required to disinfect a well if the casing is 18 inches in diameter and 220 ft long, with water level at 100 ft from the top of the well? The desired dose is

50 mg/L?

How many lbs of calcium hypochlorite (65% available chlorine) is required to disinfect a well if the casing is 18 inches in diameter and 220 ft long, with water level at 100 ft from the top of the well? The desired dose is

50 mg/L?

2 lb

s

1 lb

s

.02

lbs

0.6

5 lb

s

7%14%

0%

79%

Cl= 65/100 D=18 in=1.5 ft Well 220-100 =120 ft220 ft - 100 ft = 120 ft water in well(0.785)(D2)(H) = ft3

(0.785)(1.5 ft)(1.5 ft) (120 ft)(7.48 gal/ft3)= 1585 gal(50 mg/L)(.001585 MG)(8.34 lb/gal) = 1.01lbs 65/100

Cl= 65/100 D=18 in=1.5 ft Well 220-100 =120 ft220 ft - 100 ft = 120 ft water in well(0.785)(D2)(H) = ft3

(0.785)(1.5 ft)(1.5 ft) (120 ft)(7.48 gal/ft3)= 1585 gal(50 mg/L)(.001585 MG)(8.34 lb/gal) = 1.01lbs 65/100

1. 2 lbs

2. 1 lbs

3. .02 lbs

4. 0.65 lbs

1. 2 lbs

2. 1 lbs

3. .02 lbs

4. 0.65 lbs

Today’s objective: To practice math associated with Well Drawdown, Well yield, Specific

Capacity, and Well Disinfectionhas been met?

Today’s objective: To practice math associated with Well Drawdown, Well yield, Specific

Capacity, and Well Disinfectionhas been met?

Stro

ngly A

gree

Agre

e

Neu

tral

Dis

agre

e

Stro

ngly D

isag

ree

86%

14%

0%0%0%

1. Strongly Agree

2. Agree

3. Neutral

4. Disagree

5. Strongly Disagree

1. Strongly Agree

2. Agree

3. Neutral

4. Disagree

5. Strongly Disagree

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Groundwater Math Math for Water Technology MTH 082 Lecture 2 Well Drawdown, Well yield, Specific...

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