eDORG

A mind map for the eDORG project

Get Started. It's Free
or sign up with your email address
Rocket clouds
eDORG by Mind Map: eDORG

1. Manned entry (>36 inch diameter conduit)

1.1. M-Hands on provides better understanding

1.2. M-Safety precautions must be taken (confined space and bad air)

1.3. M-Small cores can be cut in concrete but need good repair.

2. Control Gates

2.1. Upstream Control

2.1.1. M-Caution - Underwater control gate has limited access for inspection or repairs unless reservoir is drained.

2.1.2. M-Upstream control gate allows complete dewatering and inspection of outlet conduit

2.1.3. Upstream control with sloping gate

2.1.3.1. M-Caution - Exposed gate stem is susceptible to damage (ice and erosion)

2.1.3.2. M- Upstream gate stem can be protected with concrete or riprap

2.1.3.3. M-Example 1

2.1.3.4. M-Example 3

2.1.4. Upstream control with intake tower

2.1.4.1. M-Access to gate can be difficult

2.1.4.2. M-Ice and debris may cause damage

2.1.4.3. M-Example 1

2.1.4.4. M-Example 2

2.1.5. M-Example 2

2.1.6. Hydraulic controls for upstream gate

2.1.6.1. M-Caution - leaks in hydraulic system can be very challenging to repair

2.1.6.2. M-Example 1

2.1.6.3. M-Example 2

2.2. Center Control

2.2.1. M- Graphic illustrations?

2.2.2. Wet Tower

2.2.2.1. M-Dual chamber with spillway splitter wall

2.2.2.2. M-Dual Chamber with dual slide gates

2.2.2.3. M- Example 1

2.2.2.4. M-Example 2

2.2.3. Dry Tower

2.2.3.1. M- Valves instead of slide gates

2.2.3.2. M-Example 1

2.2.3.3. M-Example 2

2.2.3.4. M- Caution - Maintaining dewatering of tower

2.3. Downstream Control

2.3.1. M- Graphic illustration?

2.3.2. M-Examples of Valves

2.3.3. M-Energy Dissipation

2.3.4. M-Caution- leak in the pressurized pipe at toe of dam could fail the dam

2.3.5. M-Caution- Energy dissipation is needed

2.4. Considerations

2.4.1. M-Dual Gates (operation & guard)

2.4.2. Gate Types

2.4.2.1. M-Slide Gates

2.4.2.2. M-Gate Valves

2.4.2.3. M-Butterfly Gates

2.4.2.4. M-Stoplogs??

2.4.3. Other Considerations?

3. Construction Considerations

3.1. Easier to bed conduit in concrete than in clay

3.1.1. Concrete more reliable

3.2. Stream Diversion (water control during construction)

3.2.1. Channel Diversion

3.2.1.1. Case Study/Example/Photos

3.2.2. Berm or Coffer Dam

3.2.2.1. Case Study/Example/Photos

3.2.3. Piped Diversion

3.2.3.1. Case Study/Example/Photos

3.2.4. Pumped Diversion

3.2.4.1. Case Study/Example/Photos

3.3. Dealing with mud/muck

3.3.1. Dewatering Wells

3.4. Filter Diaphragms

3.4.1. Compacting filter sand is important to prevent the filter from settling when it becomes saturated, but avoid overcompaction that could break down sand

3.4.1.1. If sands aren't compacted and/or wetted to eliminate bulking behavior, they will be loose in the trench and future saturation will cause collapse settlement, leaving a void above the sand.

3.4.1.1.1. In order to achieve maximum density of clean sands, filter layers should be flooded with clean water and vibrated just after the water drops below the sand surface. The filter material should be placed in lifts of no more than 12 inches.

3.4.2. Diagram showing typical filter extents (e.g., extend diaphragm into cut slope, min cover over diaphragm, extend up to normal pool elev)

4. Energy Dissipation

4.1. Energy Dissipation Structures

4.1.1. Riprap

4.1.1.1. M - Riprap most common for small dams. Graphic?

4.1.1.2. M- Example 1

4.1.1.3. M - Example 2

4.1.2. Gabions

4.1.2.1. M-Graphic?

4.1.2.2. M-Examples

4.1.3. Concrete

4.1.3.1. M-Example headwall & apron

4.1.3.2. M-Example impact basin

4.1.3.3. M-Example jump basin

4.1.4. Plunge Pool

4.1.4.1. M -Examples

5. Evaluate Existing Conditions

5.1. Pipe Deterioration

5.1.1. CMP

5.1.1.1. Note: Corrugated metal pipe is typically steel, but can be aluminum.

5.1.1.2. M- Coatings include galvanizing, bituminous or plastic

5.1.1.3. Rate of Deterioration

5.1.1.3.1. M - Compromised coating leads to rapid deterioration

5.1.1.3.2. M- Perforations in pipe exposes steel to corrosion

5.1.1.3.3. M-Concrete encasement of CMP often prevents corrosion and provides extra strength.

5.1.1.4. M - Pipe may collapse from overload or loosing strength

5.1.1.5. Joints and Connections

5.1.1.5.1. M-Connection at CMP Riser often is weak link

5.1.1.5.2. M-CMP Pipe joints often leak

5.1.1.5.3. M- Openings can cause erosion of embankment into pipe

5.1.1.6. M- Gravel & sand in outlet flow can abrade coating and steel over time

5.1.1.7. M-Older CMP with bituminous coating may be in good condition if coating is not compromised.

5.1.2. Concrete

5.1.2.1. M-Longitudinal cracks are due to over-stressed pipe (top/bottom and springline)

5.1.2.2. Joints & Connections

5.1.2.2.1. M-Grouted joints may need repair

5.1.2.2.2. M-Openings at joints may cause erosion of embankment into pipe

5.1.2.2.3. M-An offset joint implies movement in foundation or embankment

5.1.2.3. M-Surface deterioration that exposes rebar is a serious concern.

5.1.2.4. M-Different kinds of damage to Concrete

5.1.2.5. M-Good concrete can provide a very long design life

5.1.3. Steel

5.1.3.1. M-Smooth steel is much thicker than CMP and requires deeper corrosion to fail.

5.1.3.2. M-other??

5.1.4. Masonry

5.1.4.1. M-Some outlets were built of grouted stone.

5.1.4.2. M- Loss of grout and stones allows soils to erode into masonry pipes

5.1.5. Plastic

5.1.5.1. M-Kinds of plastic pipe (pvc, hdpe, solid wall, corrugated, etc.

5.1.5.2. M-Plastic may become brittle with aging

5.2. Joints & Connections (could be separate from Pipe Deterioration??)

5.3. Gates & Controls

5.3.1. Condition

5.3.1.1. M- Damage and wear to gate seats causee leaks

5.3.1.2. M-Corrosion can fail steel gates

5.3.1.3. M-Cavitation is caused by inadequate venting.

5.3.2. Operation

5.3.2.1. M-Gate stems exposed on face of dam often are damaged

5.3.2.2. M-Stem threads and operators need lubrication.

5.3.2.3. M-Bent gate stems buckle closing gate

5.3.2.4. M-Access to gate operator can be a problem

5.4. Seepage & Piping

5.4.1. M-Look for evidence of seepage at downstream exit area

5.4.2. M-Seepage along pipe can cause failure

5.4.3. M-Seepage into pipe can cause failure

5.5. Erosion/Energy Dissipation

5.5.1. M-Headcuts in stream can lead to failure

5.5.2. M-Erosion that cuts into the toe of dam can cause embankment instability

5.5.3. M-Concrete freeze-thaw deterioration

5.5.4. M- other?

5.6. Investigation Methods

5.6.1. M-References/links?

5.6.1.1. "CMP Conduit Inspection Techniques" WDE Technical Note Issue 1 Vol 5

5.6.2. Camera Inspections

5.6.2.1. M-Push a Go-Pro

5.6.2.2. M-CCTV

6. Rehab or Replace

6.1. Rehab

6.1.1. Slipline

6.1.1.1. M-Slipline inserts new pipe inside existing and grouts space

6.1.1.2. M-Slipline Examples

6.1.1.2.1. M-slipline Example 2

6.1.1.2.2. M-slipline Example 1

6.1.1.3. M-Cellular Grout is good for filling annular space.

6.1.1.4. M-Slipline Cautions

6.1.1.4.1. M-Caution (may reduce flow capacity)

6.1.1.4.2. M-Cautions (i.e. soil voids around pipe)

6.1.1.5. M-It may be similar cost with more reliability to replace on small dams

6.1.2. CIPP

6.1.2.1. M-CIPP cures a liner inside existing

6.1.2.2. M-CIPP Example 1

6.1.2.3. M-CIPP Example 2

6.1.2.4. M-CIPP works well for smaller conduits

6.1.2.5. M-It may be similar cost with more reliability to replace conduit on small dams

6.1.3. Filter Diaphragm

6.1.3.1. M-Filter Diaphrams are very important protection from erosion along pipe. Rehabs should include this feature.

6.1.3.2. M-Develop graphic of configuration

6.1.3.3. M-Example 1

6.1.3.4. M-Installing filter diaphragm may require replacement of the downstream end of pipe or extension of the pipe.

6.1.3.5. M-It may be similar cost with more reliability to replace conduit on small dams

6.1.4. Internal Sleeve (WECO)

6.1.4.1. M-Internal repair of isolated damage (joint)

6.1.4.2. M-Example 1

6.1.4.3. M-Example 2

6.1.5. References

6.1.5.1. NRCS Guide

6.1.5.2. Other Sources/Guides

6.1.5.3. Contech web link?

6.2. Replace

6.2.1. CMP

6.2.1.1. M-CMP generally not recommended due to history of corrosion problems

6.2.1.2. M-Modern corrosion protection options

6.2.2. Concrete

6.2.2.1. M-Precast Concrete Pipe can work well on small dams

6.2.2.2. M-Cast-in-place Concrete is often used on larger dams

6.2.2.3. M-Example 1, etc

6.2.2.4. M-Caution - Pipe bedding is very important.

6.2.3. Plastic

6.2.3.1. M-Different Types of plastic pipe

6.2.3.2. M-Example 1

6.2.3.3. M-Example 2

6.2.3.4. M-Caution - Plastic pipe needs very good support

6.2.3.5. M-Caution - Pipe bedding is very important.

6.2.4. Bedding

6.2.4.1. M-Soil erosion along pipes is a common failure mode. Proper bedding is key issue.

6.2.4.2. M-It is very difficult to compact clay in the haunch and concrete cradle may be similar cost with better reliability.

6.2.4.3. M-Example 1

6.2.4.4. M-Example 2

6.2.5. Filter Diaphragm

6.2.5.1. M-Filter Diaphrams are very important protection from erosion along pipe. Include this feature.

6.2.5.2. M-Develop graphic of configuration

6.2.5.3. M-Example 1

6.2.5.4. M-Installing filter diaphragm may require replacement of the downstream end of pipe or extension of the pipe.

6.3. Factors

6.3.1. Pipe Condition

6.3.1.1. M-When pipe is in bad condition, be worried about voids in embankment.

6.3.1.2. M-In-place rehab can be an efficient repair

6.3.2. M-Displacement of existing conduit is reason to replace

6.3.3. M-Installing filter diaphragm typically requires replacement of the downstream end of pipe or extension of the pipe.

6.3.4. M-Connections may make replace easier/cheaper than rehab

6.3.5. Voids in Embankment

6.3.5.1. M-Voids adjacent to conduit is generally reason to replace

6.3.5.2. M-You don't always know that there are not voids.

6.3.6. M-Installing internal rehab may reduce pipe capacity.

6.3.7. M-It may be similar cost with more reliability to replace conduit on small dams

7. Seepage Control

7.1. Erosion along conduit

7.1.1. Filter Diaphragm

7.1.1.1. M-Filter Diaphrams are very important protection from erosion along pipe. Include this feature.

7.1.1.2. M-Develop graphic of configuration

7.1.1.3. M-Example 1

7.1.1.4. M-Installing filter diaphragm may require replacement of the downstream end of pipe or extension of the pipe.

7.1.2. M-Seepage Collars are not good practice

7.2. Erosion into conduit

7.2.1. M- Leaks into conduit can create voids

7.2.2. M-Example 1 (Tin Cup?)

7.2.3. M-Example 2

7.2.4. M-It is important to control leaks into conduit

7.3. Erosion from leak downstream of diaphragm (pressure conduit)

7.3.1. M-Caution- leak in the pressurized pipe at toe of dam could fail the dam

7.3.2. M-Redundant measures to prevent leaks (encasement, pipe-in-pipe, etc.

7.3.3. M-Examples