A Study in Emergency Well Disinfection in Response to Flooding from

Hurricane Floyd, North Carolina

Stuart SmithGround Water ScienceUpper Sandusky, Ohio USA

Crucial contributions: MikeVaught, EGIS, Chapel Hill NC

Impacts of H. Floyd, 1999Hurricane Floyd flood

altitude, Cape Fear River, Pender County

Hurricane Fran

Boat landing, end of Whitestocking Rd., Near Burgaw

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

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.

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

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.

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).

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

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.

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).

Application or modification

Total group

MGWC + Special VA

NC SC NC EH

Premixed 56 26 7 5 10 8

Applied in well 36 20 3 2 8 3

pH is modified 34 19 1 3 9 2

Hose circulation

49 23 9 4 6 7

Spot applied 29 17 2 3 6 1

Mechanical development

43 24 7 5 6 1

Pumping to clear debris

37 18 6 4 7 2

Contact < 6 hr 3 2 0 0 1 0

Contact 6-12 hr 11 9 1 0 1 0

Contact 12-24 hr

29 10 5 3 6 5

Contact 24+hr 32 9 7 3 8 5

Category 50 100 200 200-500

500-1000 >1000

Total group 15 25 12 14 12 6

Special + MGWC

4 6 7 8 4 4

VA contractors 4 6 3 1 2 0

NC contractors 0 2 0 3 3 0

SC contractors 5 6 1 0 2 1

NC EH people 2 5 1 2 1 1

Chlorine concentration use reported

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.

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

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)

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 – we’ve 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

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.

Location choices

• Burgaw area, Pender County: ID’d 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

Bored wells

Typically finished with concrete cap and well seal in a well house

Well “Bogey D”

2-in. jet pump well

Rare 4-in. diameter well with submersible pump

New “birdhouse

well” modifications post-Floyd, Cape Fear

River basin

Well sampling phase

Contacting well owners

Croomesbridge Road, Burgaw

Looked at wells and sampled

Croomesbridge Rd., Burgaw,Pender County

Buy-back property wells open almost 3 years

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

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

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

Out of picture:weed whacker, generator

Hanna multi-parameter instrument for ORP, uS/cm, pH, temperature

Hach DR870 colorimeter (Fe, Mn, Cl, etc.)

Flow meter

Mike’s compact set up

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.

Sampling taps were not ideal, but tap influences minimized

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).

Shallow well jet pump sampling assembly for wells without pumps

Suction line

Purge line

sampling

Data collection

This IS organized in its own way

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”)

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

Surprise benefit: Hearing the experiences of people with an

unprecedented disaster

Sand Hill A.M.E. Church, Pender Co. – Cape Fear R. immersed to the roof line (well in sign foreground) - now restored

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

Bogey A – near sampled wells and Bogey C

Bogey D to west on this property

Bogey C, near sampled wells and Bogey A

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

Pender well treatment testing (Ballard 1)

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

Brushing and recirculation used in bored wells

Air-powered displacement initially tried on 2-in Bogey C – Chlorinated water went out screen at top – did not reach bottom

Na hypochlorite must be tremied to bottom and surged back

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,

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.

5. The treatment program was conducted successfully using off-the-shelf equipment and solutions, and mimicked the disaster-relief scenario, but

6. Expertise and time are required to assemble the proper equipment and solutions, and to apply them to make these procedures work.

7. It is time-consuming to do even a few wells properly.

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.

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.

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

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

Questions?