A Study in Emergency Well Disinfection in Response to Flooding from Hurricane Floyd, North Carolina

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A Study in Emergency Well Disinfection in
Response to Flooding from Hurricane Floyd, North
Carolina
Stuart Smith Ground Water Science Upper Sandusky,
Ohio USA Crucial contributions Mike Vaught,
EGIS, Chapel Hill NC
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Impacts of H. Floyd, 1999
Hurricane Floyd flood altitude, Cape Fear River,
Pender County

• Thousands of homes made uninhabitable
• 48 people died 100,000s livestock
• Potential fecal and pathogenic bacterial
  contamination of wells by immersion by flood
  waters
• 12,000 affected wells, over 2000 showed total
  coliform positive (unsafe) results
• Many remained positive after multiple
  disinfection tries
• Many people fended for themselves - overwhelming

? Hurricane Fran
Boat landing, end of Whitestocking Rd., Near
Burgaw
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To improve response to such large-scale flooding
events in the future

• The U.S. Federal Emergency Management Agency
  (FEMA) identified the need to develop procedures
  and protocols for emergency well disinfection
  that it can recommend to state and local
  emergency management agencies.

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To improve response to such large-scale flooding
events in the future, develop plans and
recommendations

• To develop these plans and recommendations
• 1. A literature review and survey of
  practitioners about disinfection methods and
  information relevant to the NC well flooding
• 2. A field evaluation of well disinfection
  methods in NC wells affected by Floyd

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Literature Review

• There is an extensive literature on well
  disinfection
• On the balance, published advice tends to be
  based on the incidental experience of case
  histories.
• Little research basis for efficacy.
• Recently, Illinois and Michigan work resulted in
  first published systematic studies of well
  disinfection.

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Literature Review

• Recommendations and improvements
• Sodium hypochlorite is best
• Calcium hypochlorite is best
• Acidification to maintain pH in range that
  hypochlorous acid is major ion in solution
• Need for agitation and contact
• Well disinfection requires mechanical action
  as well as chlorine dosage (Michigan).

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Survey of practitioners

• North Carolina Environmental Health personnel
• NC, SC, Virginia well contractors
• National (NGWA) Master Ground Water Contractor
  list
• Experts list of people known to authors
  flood-experienced contractors and researchers

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Survey results

• Most affected NC counties reported multiple
  treatments were needed to achieve
  coliform-negative results.
• Still, respondents expressed confidence in
  procedures despite multiple failures.
• Two counties reported that water well contractors
  assisted with disinfection while 8 counties
  reported that they did not.

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Survey results

• Among the contractor, expert and health personnel
  respondents, a wide range of method chemistry and
  application was reported
• There also seemed to be wide differences in
  actual knowledge of techniques.
• Experienced well contractors were aware of and
  used disinfection improvements (acidification,
  well development).

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Chlorine concentration use reported
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Causes of failure

• Mechanical or other well faults strongly chosen
  as causes by all groups, including all responding
  environmental health professionals.
• Vulnerable well location was selected by all the
  groups at nearly the same rate.
• Experts emphasized not clearing wells of
  debris and large-scale contamination.
• Among "other" responses were rust or biofouling,
  fecal matter or flesh in wells, unused and other
  exposed wells.

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Survey results Many comments

• Emphasizing contact requirement mixing and
  distribution as well as time
• Specific situations require specific procedures
• Many comments on inadequate well standards and
  oversight (NC and nationally).
• Getting pumps moving a priority

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Survey results Many comments

• Two inch and bored wells our types of interest
  NOT viewed with much optimism
• Most 2-in wells are impossible to disinfect
  without removing the drop pipe assy. (MGWC)
• Problems recur in a short time Dug and bored
  wells
• Our state (NC) needs mandatory well regulations
  (public health respondent)

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Survey results Many comments

• If we cannot for whatever reason mechanically
  develop until chlorine demand is met, the outcome
  is not favorable.
• Problem Adding too much chlorine weve been
  adding too much for years.
• Needed Contractor expertise and elbow grease.
• Some state regs preclude proper disinfection
• Comments about lack of knowledge of state regs,
  proper chemistry, and methodology

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Field Evaluation

• Sampling candidate wells, and testing treatment
  methods on selected candidate wells was
  undertaken in spring and summer 2002.
• A sampling of representative wells mostly
  shallow bored wells and shallow-to-deep 2-inch
  drilled wells for area information and to
  identify candidates for disinfection testing.
• A subset of wells selected for disinfection
  testing Bored and 2-in. wells in a cluster in
  Edgecombe County and a cluster of 2-in. wells in
  Pender County.

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Location choices

• Burgaw area, Pender County IDd as having a
  selection of flood-affected wells
• Edgecombe County Clusters of mixed types of
  wells near Tarboro and Princeville
• Mixed socio-economically, known problems
• Clusters permit practical testing and treatment

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Bored wells
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Typically finished with concrete cap and well
seal in a well house
Well Bogey D
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2-in. jet pump well
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Rare 4-in. diameter well with submersible pump
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New birdhouse well modifications post-Floyd,
Cape Fear River basin
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Well sampling phase
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Contacting well owners
Croomesbridge Road, Burgaw
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Looked at wells and sampled
Croomesbridge Rd., Burgaw, Pender County
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Buy-back property wells open almost 3 years
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Sampling and analysis methods objectives

• Identifying parameters present that may affect
  chlorination efficacy
• Testing means of distinguishing well sources by
  quality differences
• Microbial ecology and HPC impacts on
  chlorination and coliform occurrence
• TC, N-N efficacy of disinfection

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Sampling and analysis

• Onsite pH, conductivity, ORP (redox potential),
  temperature
• Onsite Fe (total and ferrous)
• Onsite (approximate) hardness and alkalinity
• Samples for BART microbial analysis
• Samples for lab TC, HPC, N-N

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Sampling and analysis methods choice objectives

• Onsite pH, conductivity, ORP (redox potential),
  temperature More realistic
• Onsite Fe (total and ferrous) and other chemical
  sampling Immediate information, a model for
  rapid response reconnaissance surveys, low cost
  per analysis many analyses (reproducible) for
  same money
• BART microbial analysis Microbial ecology
• Samples for lab TC, HPC, N-N health, safety and
  bacterial loading

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Hanna multi-parameter instrument for ORP, uS/cm,
pH, temperature
Flow meter
Hach DR870 colorimeter (Fe, Mn, Cl, etc.)
Out of picture weed whacker, generator
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Mikes compact set up
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Wells pumped until apparent stability of pH,
conductivity, and temperature, ORP in a stable
range. Values recorded at intervals. At
stability, Fe, etc., total coliform, N-N and
other samples collected.
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Sampling taps were not ideal, but tap influences
minimized
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2-in. deep well jet set up (well Bogey C) showing
jet pump, suction and return flow (jet) line,
purge line with totalizing meter (all flow was
metered).
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sampling
Purge line
Data collection
Suction line
Shallow well jet pump sampling assembly for wells
without pumps
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This IS organized in its own way
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Sampling phase results

• Baseline data collected for potential treatment
  sites basis of comparison
• Established that shallow sand water can be
  distinguished from deeper Castle-Hayne water
• Identification of potential wells for treatment
  testing
• All information supplied to well owners with
  advice as needed (fix the UV system)

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Sampling phase results

• Shallow sand wells in Edgecombe County study area
  were still pumping impaired water probably
  contaminated at an aquifer scale. Deeper
  Edgecombe and Pender County wells were not
  typically pumping impaired water.
• Deeper Castle-Hayne water was higher in TDS,
  cooler, lower ORP, similar (very low) Fe
• Identification of potential wells for treatment
  testing FEMA wells nearby tested home wells

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Surprise benefit Hearing the experiences of
people with an unprecedented disaster
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Sand Hill A.M.E. Church, Pender Co. Cape Fear
R. immersed to the roof line (well in sign
foreground) - now restored
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Disinfection treatment testing phase Edgecombe
locations
Well Diameter (in) Depth (ft) SWL (ft BTC) Yield
(gpm) Bogey A 24 24.7 10.3 7.57 Bogey
C 2 75 2.86 Bogey D 24 - 18 28 7.7 6.96
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Bogey D to west on this property
Bogey A near sampled wells and Bogey C
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Bogey C, near sampled wells and Bogey A
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Pender County locations

• Ballard 1 Shallow (depth?) 2-in. jet-pumped well
• Ballard 2 Shallow galvanized 2" with 1 1/4
  suction pipe with foot valve that failed and a
  3/4" pvc stuck down inside the 1 1/4 pipe. This
  is a standard cheap way to continue using this
  type well when the original 1 1/4 foot valve
  fails without pulling it.
• Elsie Davis place Deeper 2-in. PVC well

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Pender well treatment testing (Ballard 1)
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Disinfection Methodology

• Following literature and recommendations,
  provision to 1) mix at the surface, 2) acidify to
  favor HOCl, and 3) distribute in well
• Both Ca and Na hypochlorite tested in bored wells
  and Na hypochlorite in 2-in. wells
• As much as possible, off-the-shelf materials
  and equipment used

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Brushing and recirculation used in bored wells
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Air-powered displacement initially tried on 2-in
Bogey C Chlorinated water went out screen at
top did not reach bottom
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Na hypochlorite must be tremied to bottom and
surged back
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Disinfection methods selected and tested on both
shallow bored wells and 2-inch wells in Edgecombe
and Pender counties were generally successful
despite well faults   1.  Solutions made and
applied achieved disinfecting ORP levels.
Maintaining target total chlorine values in the
treated two-inch wells required repeated
treatment. 2.    Acidification aids in forming
optimal disinfecting solutions (favoring HOCl) in
ambient well water encountered. This was
accomplished with small amounts of acid, and can
be done safely by trained personnel. 3. Mixing
was required to distribute disinfecting solutions
through water columns,
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• 4.    Mixing in even a little too much Ca
  hypochlorite makes a solution very "hot." Sodium
  hypochlorite is easier to use in mixing
  solutions. Same is true of using HCl as
  acidifier.
• The treatment program was conducted successfully
  using off-the-shelf equipment and solutions, and
  mimicked the disaster-relief scenario, but
• Expertise and time are required to assemble the
  proper equipment and solutions, and to apply them
  to make these procedures work.
• It is time-consuming to do even a few wells
  properly.

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Recommendations

• For another large-scale disaster such as
  Hurricane Floyd, preparation would help
• Proper treatment requires sufficient numbers of
  trained people to respond properly
• Two-inch wells definitely require trained and
  equipped disinfection suppliers.

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Recommendations

• A Na hypochlorite solution, acidified and mixed
  at the surface at 100-200 ppm is effective.
• The solution has to be well mixed in the bore or
  stratification occurs
• Two-inch wells definitely require trained and
  equipped disinfection suppliers civil-defense
  type training of responders recommended
• Make part of an emergency management plan.

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A ready alternative for water supply is public
water if a combination of improved well
construction and disinfection after emergencies
fails to improve the situation
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Thanks and acknowledgments

• Mike Vaught and the people of his company, EGIS,
  and Ground Water Science colleagues
• The many helpful state and county people in North
  Carolina and survey respondents
• The good folks whose wells we sampled and
  disinfected
• Advisors and peer reviewers on this project
• The NGWA and its staff and our sponsor, the
  Federal Emergency Management Agency

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Questions?