UNDERSTANDING AND MANAGING PLANT AND ANIMAL INTRUSIONS IN EMBANKMENT DAMS

Transcription

1 UNDERSTANDING AND MANAGING PLANT AND ANIMAL INTRUSIONS IN EMBANKMENT DAMS GREG ZAMENSKY, PE 1 AGENDA Introduction Plant Intrusions Q&A Animal Intrusions Q&A Closing 2 ABOUT THE INSTRUCTOR GREG ZAMENSKY 23 years of concentrated experience in dam engineering New dams and rehabilitations Investigation, evaluation, design and construction phase services Projects located throughout the U.S. Black & Veatch s Americas Practice Leader for Dams and Flood Control 3 1

2 WHAT ARE WE TALKING ABOUT? EMBANKMENT DAM OR LEVEE 4 A WORD ABOUT LEVEES Many of the images and discussion focus on embankment dams Levees are equally susceptible to plant and animal intrusions Levees can have other intrusions New Orleans, LA, 2007 (above) Cap au Gris Levee, MO, 2008 (below) 5 HOW SERIOUS CAN THIS STUFF BE? Survey conducted in 1999 of state dam safety agencies (48 responding states) Area Systemic Problem Contributedto Dam Failure Woody Vegetation 100% 64% Animal Intrusion 95% 52% According to NPDP, 59 incidents between with 24 failures 6 2

3 7/14/2015 KELLY BARNES DAM (TOCCOA FALLS), GA 40 ft tall, 400 ft long earthen embankment Failed in 1977, killing 39 Failure investigation indicated: Localized slide on downstream slope Loss of freeboard Piping Excessive vegetation identified as contributing factor 7 KELLY BARNES DAM (TOCCOA FALLS), GA Downstream slope before failure, 1973 Dam breach looking downstream, 1977 Downstream slope and left side of breach, OBJECTIVE OF THIS WEBINAR Provide practical understanding of plant and animal intrusions in embankment dams and levees Effects Inspection & Evaluation Management & Control 9 3

4 GENERAL DAM/LEVEE LIFE SPAN Failure always possible Plant and animal intrusions occur with more mature structures Targeted maintenance can eliminate these as a failure mode 10 SIGNIFICANT TECHNICAL RESOURCES FEMA 534 -Technical Manual for Dam Owners Impacts of Plant on Earthen Dams FEMA 473 Technical Manual for Dam Owners Impacts of Animals on Earthen Dams ASDSO Northeast Regional Seminar Woody Vegetation and Wildlife on Earthen Dams 11 UNDERSTANDING AND MANAGING PLANT INTRUSIONS IN EMBANKMENT DAMS 12 4

5 OVERVIEW Effects of Plants on Earthen Dams Identification and Evaluation Controlling Vegetation Dam Repair Fiscal Considerations 13 DOES YOUR DAM LOOK LIKE THIS? 14 ROOT OF THE PROBLEM Trees (all types and sizes) Bushes and shrubs Vines (Kudzu) Desert plants (cacti, sagebrush) 15 5

6 WHAT DO PLANT INTRUSIONS LOOK LIKE? 16 WHAT DO PLANT INTRUSIONS LOOK LIKE? 17 WHAT DO PLANT INTRUSIONS LOOK LIKE? This is an emergency room visit waiting to happen 18 6

7 THE ROOT OF THE ISSUE: TREE ANATOMY Trunk indicative of root system size Rootball mass directly below trunk Lateral root system roots spreading asymmetrically from the trunk Tap root deep root 19 THE ROOT OF THE ISSUE: BIGGER IS WORSE, MUCH WORSE Trunk Diameter, in Rootball Diameter, ft Root System Diameter, ft 4 to to 12 8 to to to to to to to to 90 OllalaDam (1998) 20 POTENTIAL NEGATIVE IMPACTS OF WOODY VEGETATION Facilitate water movement along root penetration Decaying roots lead to voids and threaten structural integrity Attractive habitat for burrowing animals Loosens soil matrix 21 7

8 POTENTIAL NEGATIVE IMPACTS OF WOODY VEGETATION Windthrowof trees can lead to major damage Surface erosion along roots Clogging of drains systems Reduces dense grass cover Add load to slip surface decreasing factor of safety 22 POTENTIAL NEGATIVE IMPACTS OF WOODY VEGETATION Alter flow regime across dam crest and spillways 23 POTENTIAL NEGATIVE IMPACTS OF WOODY VEGETATION Damage to concrete structures Hinders effective inspection 24 8

9 HOW COMMON IS THE PROBLEM? As reported by state regulators (2000), about ½ of state-regulated dams have excessive woody vegetation growth 100% of states report vegetative growth is problematic 64% of states report vegetation has caused dam safety problems 25 NOT ALL TREES ARE CREATED THE SAME The size, location and frequency of the tree population are all important Well-defined inspection and evaluation methodology will establish priorities 26 DAM REPAIR / INSPECTION ZONES HELP DEFINE PRIORITIES 27 9

10 CONDITIONS ALL TOO COMMON 28 MAINTENANCE BECOMES DAM REMEDIATION THROUGH COMPLACENCY Early treatment of woody vegetation is generally considered maintenance As the tree population grows in number and size, maintenance turns into remediation 29 MAINTENANCE RULES FOR EMBANKMENT DAMS. AND LEVEES, MAYBE Existing trees should be removed and not permitted to mature Tree or shrubbery should never be planted Existing trees should be observed regularly until removed Grasses and shallow-rooted native vegetation are the most desired surface covering 30 10

11 NO CONSENSUS FOR TREATMENT - STATE OF PRACTICE FRAGMENTED No trees are allowed on embankment All trees and stumps must be removed, but roots may be left in place Cut trees to ground level Small caliper trees okay, large caliper trees must be removed Case-by-case 31 WHERE CAN WOODY VEGETATION EXIST ON YOUR EMBANKMENT DAM 32 TYPICAL MAINTENANCE APPROACHES Provide a hostile environment for sustaining woody vegetation Mowing, cutting Herbicides 33 11

12 REGULAR MAINTENANCE A LITTLE GOES A LONG WAY Mowing, cutting and weed-whacking should be completed at least twice per year Consider existing vegetation and location to determine optimal frequency Spring mowing close to the ground cutting of all vegetation Fall mowing longer cutting to prevent surface erosion 34 NO JOB TOO SMALL, BIG, OR.. Spider Mower (Dvorak, Quartrak(slopemoving.com) Slope Master (KutKwickCorp) 35 MAINTENANCE FOR THOSE HARD TO REACH AREAS Selective use of herbicides may be necessary in locations where mowing is not practical Overuse or improper application can have detrimental effects on surrounding vegetation Solicit the nearest USDA/NRCS representative to ensure proper selection 36 12

13 MAINTENANCE FOR THOSE HARD TO REACH AREAS Numerous products available depending on delivery method Foliage spraying Tree injection Frill or girdle treatment Basal back spraying Cutting tree/poisoning stump Soil treatment 37 APPLICATION OF HERBICIDES Method of Application Time Period Considerations Cutting of trees and poisoning stumps Injection Foliage spraying Frill treatment(trees > 4 inch caliper) Basal spraying(trees <6 inch caliper) Growing season EPA & State regs. Drift (offsite and Anytime Last 2 months of growing season Anytime Growing season onsite) Dosage Placement Retention time Follow manufacturer directions 38 DAM REMEDIATION Large trees can effect significant portions of an embankment dam improper treatment can do more harm than good Owners should consult a professional engineer in these situations 39 13

14 INTELLIGENT DESIGN PRACTICES NOT JUST GOOD IDEAS Placement of engineered fill Proper compaction: >95% Standard Proctor Proper moisture condition: -2 to +3% of optimum Use of seed mix to establish site appropriate grasses Installation of filter and drain materials, if considered necessary given zone 40 GENERAL CONSIDERATIONS WHEN TACKLING LARGE SCALE TREATMENT Repair Zone Procedure Zone 1 Remove all trees, stumps, rootballs, and root systems (> ½ in dia) Backfill with engineered fill Install wave protection system 41 GENERAL CONSIDERATIONS WHEN TACKLING LARGE SCALE TREATMENT Repair Zone Procedure Zone 2 Downstream sideof crest, cut trees<12 in dia flush to ground and treat with waterproof sealant Completely remove trees >12 in dia Backfill with engineered fill Reseed with proper mix 42 14

15 GENERAL CONSIDERATIONS WHEN TACKLING LARGE SCALE TREATMENT Repair Zone Procedure Zone 3 Cut trees < 6 in diaflush to ground and treat with waterproof sealant Completely remove trees > 6 in dia Backfill with engineered fill Reseed with proper mix 43 GENERAL CONSIDERATIONS WHEN TACKLING LARGE SCALE TREATMENT Repair Zone Procedure Zone 4 Cut trees < 4 in diaflush to ground and treat with waterproof sealant Completely remove trees > 4 in dia Install filter / drain system (sand & gravel) Backfill with engineered fill Reseed with proper mix 44 GENERAL CONSIDERATIONS WHEN TACKLING LARGE SCALE TREATMENT Repair Zone Zone 5 and at least 25 beyond downstream toe Procedure Completely remove trees > 4 in dia Install major filter / drain system to lower the phreatic surface Backfill with engineered fill on slope Backfill cavities downstream of toe with weighted filter and drain system Reseed with proper mix 45 15

16 WHAT KEEPS OWNERS FROM DEALING WITH VEGETATION Financial limitations by owners Environmental regulations (use of herbicides) Legal issues Threatened/endangered species Aesthetics 46 FINANCIAL CONSIDERATIONS Costs vary widely Work force availability Project size and scope (clearing, grubbing, chipping) Vegetation type and density Range of <$1,000 to >$10,000/ac is common depending on issues Mowing -$50 to $100/ac Herbicide applications - $100 to $1,000/ac Clear trees and grub stumps -$3,000 to $5,000/ac 47 DEVELOPMENT OF A VEGETATION CONTROL PROGRAM Treatment of all vegetation issues may be daunting to some owners Work with state regulators and professional engineers (as necessary) to develop a sequential management plan 48 16

17 A FEW LEVEE THOUGHTS Woody vegetation in levees in very common This vegetation has been shown to have contributed to failure Management is extremely difficult given longevity and shear volume Winfield-PinoakLevee, Missouri (2008) 49 A FEW LEVEE THOUGHTS A well maintained levee survived overtopping due to: Lack of woody vegetation (and other thing) Well established grass cover BrevatorLevee, Missouri (2008) 50 LEVEES USACERESEARCH ON EFFECTS OF WOODY VEGETATION USACE conducted research initiated in 2007 Conclusions developed in November 2011 Cap au Gris Levee, MO (could be anywhere in US) 51 17

18 LEVEES USACERESEARCH ON EFFECTS OF WOODY VEGETATION Published a four volume manual documenting the investigation, analysis, and conclusions Conclusions Trees can help levees Trees can damage levees Levee sections should be evaluated on a case-by-case basis 52 QUESTIONS & ANSWERS 53 UNDERSTANDING AND MANAGING ANIMAL INTRUSIONS IN EMBANKMENT DAMS 54 18

19 OVERVIEW Effects of Wildlife on Earthen Dams Identification of Nuisance Wildlife Dam Repair and Prevention through Design Mitigation Fiscal Considerations 55 ANIMAL INTRUSIONS ARE A SIGNIFICANT PROBLEM More than 50% of state dam safety regulators indicated that animal intrusions as a cause of dam failure or serious incident Only 9 states provide guidance on the effects of animal burrows 56 MORE THAN A CONCERN -REPORTED INCIDENTS Case Date Description SidWhite Dam, WA 1971 Seepage through burrows. Caused downstream dam to fail. Waters Edge Dam, OH BeefProcessor Waste Pond, WA PischieriPond Dam, OH 1992 Water flow through rodent holes and burrows 1993 Uncontrolled seepage through burrow 1999 Forensic study of failed structure revealed voids consistent with burrows Truckee Canal, NV 2008 Woody vegetationand burrow identified in forensic reporting Pin Oak Levee, MO 2008 Burrows suspected in incident(muskrat, others) 57 19

20 PICTURES ARE INDEED WORTH A THOUSAND WORDS Ascalmore#11 failed in 2000 Built in 1959 Animal burrows cited as major factor 58 WHO ARE THE MAJOR CULPRITS? Twenty three wildlife species have been identified as causing damage to embankment dams Species States that Consider the Specie Having a Significant Effect, % Muskrats 71 Beaver 67 Livestock 25 Gopher 23 Badger 17 Ground Squirrel EXTENT OF POSSIBLE DAMAGE SHOULD NOT BE UNDERESTIMATED Muskrats Beaver Livestock Gopher Badger Species Typical Damage Typical Burrow Shape Active Side Ground Squirrel Large burrows that shorten seepage path Spillway and outlet structure damage Vegetation loss and irregularity in slope surface Mainly surficial damage and prey for badgers Dig for preyand construct large dens Several squirrels can create sig. loss in integrity Up to10 ftbelow water surface and 5-6 in dia 1-4 ftbelow water surface with dens 5-10 ft dia NA Horseshoe mounds, short burrows 5-30 ftlong burrows with 2-3 ftchambers 2-10 in diameter and 10 ft long (often found in clusters) Waterside Waterside Both Landside Landside Both 60 20

21 WHAT ARE WE TALKING ABOUT? 61 WHAT ARE WE TALKING ABOUT? 62 DAMAGE CAN COME IN DIFFERENT SHAPES AND SIZES Hydraulic alteration Structural integrity losses Surface erosion 63 21

22 HYDRAULIC ALTERATION CAN LEAD TO SEVERE PROBLEMS Burrows can shorten the seepage path through an embankment Significantly altering phreatic surface Effecting slope stability 64 HYDRAULIC ALTERATION CAN LEAD TO SEVERE PROBLEMS Shortened seepage paths result in increase exit gradients Increasing seepage quantities Increasing risk of piping and backwards erosion 65 LOSE OF STRUCTURAL INTEGRITY Burrow collapse often lead to sinkholes or depressions Localized slope stability Loss of freeboard 66 22

23 SURFACE EROSION CAN BE PROBLEMATIC WHEN LEFT UNATTENDED Loss of vegetative cover from grassing animals can lead to erosion paths and decreased soil retention Frequent trafficking along the downstream slope leads to irregular surface runoff and the formation of rills and gullies 67 DAM INSPECTIONS FROM TWO PERSPECTIVES Physical inspection guidelines are well developed and understood Observe each feature and record information including animal burrows However, all holes are not created equally Without proper training, the inspector may not be able to identify and therefore mitigate the nuisance animal When considering animal intrusions, the inspection should consider physical evidence as well as biological factors 68 DAM INSPECTION FROM TWO PERSPECTIVES Engineering and biological perspectives should be considered during the inspection Where did I see the burrow and what were it s characteristics? What is the likely culprit? Is the culprit a protected species (state, federal)? 69 23

24 ANIMAL INTRUSION CONSIDERATIONS Engineering What to look for? Burrow entrances Mounds of excavated material Debris (beaver) Cracks Depressions Erosion Sinkholes Paths and ruts Slides and scarps Biological What does the area offer? Temporary shelter Permanent shelter Food Water 70 EACH AREA HAS ITS PREFERRED TENANTS AND UNIQUE CHARACTERISTICS 71 ACCURATE IDENTIFICATION LEADS TO PROPER MANAGEMENT AND REMEDIATION APPROACHES Identification includes Directly observing the animal unlikely Consider habitat and home Think about range (can my area support this animal?) Tracks FEMA 473 Technical Manual provides very good summary for most common animals 72 24

25 ANIMAL MANAGEMENT TECHNIQUES Non-lethal control methods Lethal control methods Darwinian law in action. Unfortunately, the smarter ones live on. 73 NON-LETHAL CONTROL CAN BE DIFFICULT OR INEFFECTIVE Removal of food sources or cover can effectively achieve habitat modification Riprap protection along the upstream can prevent muskrat access Lower water levels temporarily Translocationof the animal to a distant site 74 NON-LETHAL CONTROL CAN BE DIFFICULT OR INEFFECTIVE Repellantscan be effective but are specific Beaver 90/10 solution of diesel fuel and creosote Gophers Sulfur based compounds (predator urine) Exclusionthrough fencing is only marginally effective Frightening devices to alter behavior 75 25

26 THERE ARE OTHER, MORE DRASTIC TECHNIQUES 76 LETHAL CONTROL METHODS BECOMING LESS ACCEPTED Toxicants can be highly effective, but. Highly regulated Hazard to humans and other animals Must use extreme caution 77 LETHAL CONTROL METHODS BECOMING LESS ACCEPTED Harvestingof animals through shooting is generally considered ineffective and dangerous Can be effective for a single animal, if done appropriately 78 26

27 LETHAL CONTROL METHODS BECOMING LESS ACCEPTED Trapping highly effective but time consuming and labor intensive Requires knowledge and experience 79 DAM REMEDIATION PREVENTATIVE AND RESTORATIVE Proper maintenance of the embankment will create an inhospitable environment Limit vegetation for food supply Remove tall vegetation to remove protective cover and shelter Maintain good erosion protection layer along upstream slope (e.g. riprap) 80 DAM REMEDIATION PREVENTATIVE AND RESTORATIVE Industry standard new dam design approaches incorporate preventative measures Relatively flat slopes (3H:1V or flatter) Upstream slope erosion protection Proper soil compaction 81 27

28 DAM REMEDIATION RESTORATION ACTIVITIES VARY WITH LOCATION The appropriate restoration method depends on the location and magnitude of damage A professional engineer should be consulted for most animal intrusion repairs 82 DETECTION THROUGH MODERN TECHNOLOGY Non-destructive methods for mapping of burrows has improved greatly Consult a knowledgeable professional when considering these technologies Method Gravity survey Resistivity methods Seismic reflection Ground penetrating radar Measured Parameter Density Electrical resistivity Seismic velocity Dielectric constant 83 IDENTIFICATION OF CULPRIT IMPORTANT Understanding the extent of possible damage Surficial or deeply intrusive Selecting the most appropriate remediation Hand tools to large excavators 84 28

29 REMEDIATION ZONE 1 Critical due to proximity to phreatic surface Several potential issues Muskrat Wave erosion Treatment measures Lower reservoir Excavation and backfill Slope hardening 85 REMEDIATION ZONES 2 AND 3 Not as critical, generally outside the phreatic surface, but important Burrows can be extensive, must identify culprit Remediation can vary Excavation, backfill Fill burrow with lean grout 86 REMEDIATION ZONES 4 AND 5 Phreatic surface effects possible, very possible Remediation of burrows should involve installation of filter/drain and conveyance 87 29

30 THERE IS NO TYPICAL REPAIR COST The cost to repair animal intrusions is dependent on: Extent of damage (surficial or deeply intrusive) Size of burrow(s) Horizontal and vertical location of burrow(s) Do not discount the importance of investing in proper repair and future mitigation 88 A FINAL WORD ON LEVEES Everything discussed today is applicable to levees In fact, levees are considered more susceptible to some types of damage given the construction materials and techniques used PinoakLevee, MO 89 WHEN TRYING TO FIGURE OUT WHAT TO DO Perform literature review Learn what you don t know Reach out to USDA, NRCS, USFWS personnel These folks know what they are doing Talk to engineers experienced in the remediation of animal intrusions 90 30

31 QUESTIONS & ANSWERS 91 FINAL THOUGHTS Plant & animal intrusions are very real problems Their presence will grow without increased diligence by dam owners 92 APPRECIATION ASDSO for sponsoring this webinar and many others 93 31

32 THANK YOU FOR PARTICIPATING 94 Post Event Evaluation & Quiz Please click the following link to take the Seminar Evaluation and Quiz: You must complete the Seminar Evaluation and Quiz to receive PDH credit hours 95 32