POND CONSTRUCTION. Woodland Steward Series

Transcription

1 POND CONSTRUCTION Woodland Steward Series

2 BOB TWOMEY DISTRICT CONSERVATIONIST USDA NATURAL RESOURCES CONSERVATION SERVICE

3 COURSE OUTLINE DEFINITION OF A POND OR LAKE TYPES OF PONDS GEOLOGIC CONSIDERATIONS TOPOGRAPHIC CONSIDERATIONS SOILS CONSIDERATIONS PERMITS & REGULATIONS SAFETY & LIABILITIES DESIGN & ENGINEERING TOUR CRADLE OF FORESTRY POND

4 DEFINITION OF A POND A WATER IMPOUNDMENT MADE BY CONSTRUCTING AN EMBANKMENT ACROSS A CHANNEL OR BY EXCAVATING A PIT OR DUGOUT. IT IS EITHER AN EMBANKMENT POND, AN EXCAVATED POND, OR A COMBINATION OF BOTH.

5 PONDS CONSTRUCTED BY BOTH EXCAVATION AND EMBANKMENT INSTALLATION ARE CALLED EMBANKMENT PONDS IF THE DEPTH OF WATER AGAINST THE EMBANKMENT (DAM) IS 3.0 FEET OR DEEPER

6 EXCAVATED POND EXCAVATED POND

7 EMBANKMENT POND DAM

8 COMBINATION POND SMALL DAM EXCAVATED AREA

9 WHETHER YOU HAVE A BIG LAKE

10 OR JUST A SMALL FARM POND

11 YOU MUST HAVE A CLEAN, DEPENDABLE SOURCE OF WATER

12 QUALITY PONDS COME FROM PROPER PLANNING, SITE SELECTION, SURVEY & DESIGN, & CONSTRUCTION

13 GEOLOGY AND PONDS LOOSE, FRACTURED OR FISSURED ROCK FORMATIONS UNDER A POND DON T HOLD WATER VERY WELL. NEITHER DO SCREEN DOORS ON A SUBMARINE. BEDROCK IS HARD TO BUILD A DAM UPON AND OBTAIN A WATER-TIGHT SEAL AT THE DAM/ROCK INTERFACE.

14 GEOLOGY CONT. ALL PONDS LEAK SOME, BUT IF THE LEAKAGE IS GREATER THAN ALL EVAPORATION & INFLOW(S).YOU RE GONNA HAVE A PROBLEM: ITS CALLED A MUDHOLE, AND IT COULD BE A CHRONIC MUDHOLE.

15 Leakage Problems POOR SOILS IN THE FILL AND/OR FOUNDATION, POOR COMPACTION OF SOIL, ROCKS AND ORGANIC MATTER IN THE EMBANKMENT FILL, RODENT ACTIVITY IN THE POND OR DAM, ROCK SUBSTRATA WITH FRACTURES.

16 TOPOGRAPHY AND PONDS

17 TOPOGRAPHY OR TERRAIN: CAN AFFECT SIZE, SHAPE & DEPTH OF A POND; AFFECT DAM/EMBANKMENT HEIGHT; AFFECT SPEED & INTENSITY OF RUNOFF INTO THE POND; GREATLY AFFECT COMPLEXITY OF DESIGN & CONSTRUCTION, THUS COST; DIRECTLY AFFECT SAFETY ISSUES.

18 UPLAND EMBANKMENT POND IN PASTURES, CREEK FED. WATER SOURCE

19 HIGH MOUNTAIN LAKE

20 SOIL CONSIDERATIONS SOILS AT POND SITE MUST BE FAIRLY IMPERVIOUS IN POND BOTTOM; SOILS TO CONSTRUCT A DAM MUST BE COMPACTABLE, THUS NOT SANDY AND NOT HIGH SILT-CLAY CONTENT; PREFERABLY SANDY CLAY, SANDY CLAY LOAM, CLAY LOAM TEXTURE.

21 AND NOT CONTAIN ROCKS, STUMPS, LOGS OR ORGANIC MATTER A LITTLE TOO MUCH ROCK IN DAM

22 FOREIGN DEBRIS IN POND/DAM SOILS: IS NOT COMPACTABLE; CAUSES PIPING THROUGH THE SOIL PROFILE; CAN SETTLE OR SHIFT OVER TIME CAUSING LEAKAGE; CAN BECOME A DAM SAFETY ISSUE; CAN CAUSE A POND/DAM TO FAIL.

23 IMPROPER SOILS, INADEQUATE COMPACTION CAN ALLOWS WATER TO PIPE THROUGH THE DAM, BARREL PIPE CAUSING EVENTUAL DAM FAILURE DAM WASHED-OUT THROUGH THE EMBANKMENT

24 SOIL FOR PONDS SHOULD BE CLOSE BY TO REDUCE TRANSPORT COSTS TO DAM SITE; BE FREE OF LARGE ROCKS OR EXCESSIVE AMOUNTS OF ROCKS; BE FREE OF STUMPS, LOGS, LIMBS OR HIGH ORGANIC MATTER CONTENT.

25 HIGH ORGANIC MATTER CONTENT, LIMBS, AND TOO MUCH ROCK CONTENT IN THIS EARTHEN DAM LED TO DAM FAILURE.

26 Rim Pond Issues Volume of water available/water table; Volume of leakage through the rim or the floor of the pond; Safety Liability, depth, side slopes; Over-flooding by nearby live stream during flood conditions; Clogged supplemental water intakes.

27 Embankment Pond Issues Volume of constant water supply Volume of storm runoff inflow Upstream water quality and sediment load Integrity of the Embankment structure Leakage through the Embankment Requires a through the dam drain pipe Requires a by-pass emergency spillway Safety and downstream Liability

28 Planning and Design Issues Drainage area of stream watershed; Water quality & adequate volume; Intended purposes objectives; Foundation soils; Embankment soils; Potential downstream damages, liability; Safety, slope of dam sides, depth, etc..

29 Problems Too Little Water = stagnant pool; Too Much Water = over-topping dam/esw Excessive Sediment = loss of pool area; Leakage from unsuitable soils in/around pond and/or dam; Drain Pipe Failure = pipe corrosion, damaged piping,

30 WHICH BRINGS US TO THE PERMITS & REGULATIONS DIFFERENT TYPES OF PONDS REQUIRE DIFFERENT PERMITS.

31 EMBANKMENT PONDS USUALLY HAVE A DAM ACROSS A LIVE STREAM; REQUIRE US ARMY CORPS OF ENGINEERS PERMIT(S); REQUIRE NC WILDLIFE RESOURCES COMMISSION REVIEW/CONCURRENCE USUALLY REQUIRE APPROVED NC DENR SEDIMENT & EROSION CONTROL PLAN

32 EMBANKMENT PONDS CONT. WILL REQUIRE NC DENR ENGINEERING CONSTRUCTION APPROVAL IF EITHER OF THE FOLLOWING APPLY: DAM IS 15 FT. HIGH OR HIGHER AS MEASURED FROM THE LOWEST DOWNSTREAM TOE OF THE DAM TO THE HIGHEST C/L OF THE DAM, OR

33 EMBANKMENT PONDS CONT. THE STORED WATER VOLUME BEHIND THE DAM IS 10.0 ACRE-FEET OR MORE. IF THE POND IS CONSIDERED A HIGH HAZARD DAM, NC DENR WILL REQUIRE A LICENSED ENGINEER TO DESIGN THE DAM & COMPONENTS & SUBMIT PLANS FOR NE DENR APPROVAL BEFORE CONSTRUCTION.

34 EMBANKMENT PONDS CONT. HIGH HAZARD DAMS, CLASS B & C DAMS, ARE THOSE DAMS SUCH THAT SHOULD CATASTROPHIC FAILURE OCCUR, THERE WOULD LIKELY BE A LOSS OF LIFE OR DAMAGE TO HOMES, ROADS, BRIDGES OR OTHER INFRASTRUCTURE DOWNSTREAM OF THE DAM.

35 EMBANKMENT PONDS CONT. HAZARD CLASS A DAMS ARE THOSE DAMS DEEMED LOW HAZARD SHOULD CATASTROPHIC BREACH OR FAILURE OF THE DAM OCCUR. HOWEVER, THIS IN NO WAY EVER RELIEVES A DAM OWNER FROM DAMAGES/LIABILITY SHOULD ANY DOWNSTREAM DAMAGE OCCUR.

36 EMBANKMENT PONDS CONT. SHOULD A LOW-HAZARD, CLASS A DAM EXCEED EITHER TWO CRITERIA MENTIONED ABOVE, i.e. DAM HEIGHT OR STORAGE VOLUME, A LICENSED ENGINEER MUST DESIGN/SIGN OFF ON THE DESIGN PLANS & SUBMIT SAME TO NC DENR FOR APPROVAL BEFORE CONSTRUCTION BEGINS.

37 SAFETY & LIABILITY IN NORTH CAROLINA, DAM/POND OWNERS ARE LIABLE FOR DOWNSTREAM DAMAGES ATTRIBUTED TO FAILURE OF THE DAM

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39 SAFETY ISSUES EXIST BECAUSE A DAM HAS BEEN CREATED AND A POOL FORMED, BOTH OF WHICH POSSESS SPECIFIC HAZARDS. RELATIVELY STEEP DAM SLOPES AND DEEP POOL ON OTHERWISE BEAUTIFUL NEW POND.

40 WHEN THIS DAM FAILED, A LOT OF WATER WAS RELEASED INTO THE DOWNSTREAM AREA QUICKLY. ORIGINAL CREEK

41 DAM SLOPES THAT ARE STEEPER TO REDUCE WATER WEED GROWTH BECOME A SPECIAL HAZARD TO POND WADING, SHALLOW WATER ACTIVITIES, & CHILDREN/NON-SWIMMERS. THIS APPLIES TO DUG OR EMBANKMENT PONDS.

42 STEEP DAM SLOPES ARE A HAZARD TO MOWING MACHINERY (OVERTURNS, SLIPPAGE) ARE MORE DIFFICULT TO MAINTAIN; ARE MORE SUSCEPTIBLE TO SLIDES WHEN EXCESSIVELY WET.

43 DESIGN AND ENGINEERING THERE ARE CRITICAL ELEMENTS OF DAMS THAT MUST BE PROPERLY DESIGNED

44 IMPORTANT FEATURES PROPER DAM HEIGHT, WIDTH, SLOPES, WATER LEVEL AND CONTROL STRUCTURES; PROPER PIPING AND DRAINAGE SYSTEMS; ADEQUATE EMERGENCY SPILLWAYS; OPERATION AND MAINTENANCE PLANS.

45 EMBANKMENT DAMS MUST HAVE A PERMANENT WATER LEVEL CONTROL SYSTEM; MUST HAVE AN ADEQUATE EMERGENCY SPILLWAY SYSTEM; MUST HAVE ADEQUATE STORM STORAGE CAPACITY; SHOULD HAVE INTERNAL DRAINAGE SYSTEM IN DAM FOR EXCESS WATER.

46 WELL MAINTAINED DAM, GOOD VEGETATION, GOOD SLOPES & TOP WIDTH, LARGE WELL-SODDED EMERGENCY SPILLWAY

47 WELL MAINTAINED AREA AROUND POND REDUCES SEDIMENTATION INTO POND DOCK DRAIN VALVE & PSW UNIT

48 POND CHOKED WITH SEDIMENT AND WEEDS FROM EROSION IN WATERSHED ABOVE.

49 IMPROPERLY CONSTRUCTED DAM, TOO SMALL PSW PIPE SYSTEM, OVERTOPPED AND FAILED

50 PSW PIPE INLET CHOKED WITH WATERWEED GROWTH, REDUCING INTAKE EFFICIENCY.

51 POND WHERE DAM IS BEING USED AS A VEHICULAR ACCESS CROSSING. SUCH ROADWAYS ARE OK WHEN PROPERLY MAINTAINED

52 GOOD INTENTIONS NOT FOLLOWED THROUGH W/THE RIGHT ANTI-SEEP COLLARS, PIPE AND EMERGENCY SPILLWAY.

53 ALL METAL PIPE DRAIN SYSTEMS & RISER PIPES HAVE A USEFUL LIFE BEFORE THEY FAIL. ALL GOOD THINGS END.

54 THE AVERAGE LIFE OF CORRUGATED PIPE FOR RISER SYSTEMS IS YEARS.

55 WHEN DAMS FAIL SOME COSTLY DAM MISTAKES AS SEEN FROM DESIGN FLAWS OR OVERWELMING WEATHER CONDITIONS

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63 WELL PLANNED & CONSTRUCTED PONDS PROVIDE RECREATIONAL BENEFITS; CAN ENHANCE WILDLIFE AND FISHERY RESOURCES; CAN PROVIDE WATER SUPPLIES; CAN HELP RECHARGE GROUNDWATER AQUIFERS; CAN ENHANCE AESTHETICS; CAN PROVIDE IRRIGATION.

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