# Presentation: 000133

## Alexandria Boehm
Stanford University

- A Tiered Approach for the Identification of a Human Fecal Pollution Source at a Recreational Beach

- Alexandria Boehm
- Stanford University

- Image from www.catalina.com

## The Problem

- Avalon Beach had high levels of fecal indicator bacteria (FIB), especially enterococci (ENT)
- City officials could not readily identify and remediate the problem.
- Possible sources
- treated sewage effluent
- nuisance runoff
- bird and wild animal feces
- leaking sewer pipes
- boat sewage collection tanks

## Our Approach

- Tier 1. Use FIB analyses to document spatiotemporal variability and identify hot spots
- Nearshore bay survey: conducted during a flood tide, at night
- Cross-shore transect: sediment and water tested
- 24 hour study: document sunlight and tide effects
- Month long, twice daily shoreline survey
- Tier 2: Use FIB analyses to document potential sources
- Grab samples of runoff, feces, subsurface waters, cooling water discharge, leaking pipes under pier and wharf
- Intensive sampling of subsurface waters
- Tier 3: Use novel, human-specific indicators to determine if human sewage contributes to FIB.
- Hot spots and sources assayed for *Bacteroides/Prevotella* DNA (Bernhard and Fields) and enterovirus genomic RNA (Monpoeho et al.)

## Slide 4

## Tier 1: Nearshore bay survey

- 1900 to 2100 h 19 Sept 2001

- MPN/100 mL

## Tier 1: Cross shore survey

## Tier 1: 24 h survey

- MPN/100 mL

- Distinct diurnal/semi-diurnal signal at S11

## Tier 1: Month long survey (1)

|  | Visitors | Tide Range | Littoral current |
| --- | --- | --- | --- |
| Log mean TC | 0.19 | -0.43 | -0.19 |
| Log mean EC | 0.25 | -0.34 | 0.03 |
| Log mean ENT | 0.23 | -0.11 | -0.26 |

- None significant at 95%

## Tier 1: Month Long Survey (2)

## Tier 2: Source investigations-runoff, bird feces, pipe discharge

- MPN/100 mL

## Tier 2: Source investigations -subsurface waters

- MPN/100 mL

## Tier 3: Bacteroides/Prevotella (HF) & Enterovirus (HV) testing

_**Detection Limits**_
- HV: 1 pfu per volume filtered (2-20 L)
- HF: 1 μg fecal matter per volume filtered (1-4 L)

## Interpreting negative results...

- “Because DNA tests have positively ruled out humans
- as the source of bacteria in the bay, we suspect that
- large populations of birds around our bay are the
- probable source.”
- --Avalon Bay Water Quality pamphlet handed out to tourists exiting boats _*prior to our study*_.

## Implications

- FIB at Avalon Beach are from sources inside the bay, from the land side of the beach.
- Nearshore bay survey, cross shore survey, ebb tide signal (24 hour study, month long survey)
- At least a portion of the pollution is from human sewage
- Extraordinarily high levels of FIB in groundwater
- HF and HV markers found at every shoreline site (except middle) and in a groundwater sample
- City of Avalon slip-lined their sewer lines adjacent to the beach in the winter of 2001/2002

## Has water quality improved?

- www.healthebay.org

## Are polluted sediments/groundwater impacting water quality at other locations?

- 61 beaches examined to determine if influenced by tides

## Data & Method

| Location | Data Duration | Frequency of data | Number of stations | Data |
| --- | --- | --- | --- | --- |
| Santa Monica (I) | 9/1/87 -7/4/94 | Daily | 17 | ENT & tide level / range |
| Santa Monica (II) | 7/5/94 -12/31/99 | Daily to weekly | 18 | ENT & tide level / range |
| Whites Point | 12/1/91 -12/28/99 | Daily to weekly | 18 | ENT & tide level / range |
| Huntington Beach | 6/1/98 -8/30/01 | 5 d per wk | 8 | ENT & tide level / range |

- Compare ENT levels at each station measured during
- 	• ebb vs. flood
- 	• spring vs. neap

## Difference in ENT between tidal conditions

## Which beaches have strongest tidal signal? 

- Not related to proximity to a surficial watershed outlet, slope of input, beach slope, or beach direction
- Tidal signals wide-spread at beaches away from watershed outlets
- Results suggests that tidally-forced sources other than land-based surficial runoff are widespread. Potential sources include:
- Sand
- bird feces
- wrack near the high water line
- groundwater within the beach aquifer

## Acknowledgements

- Funding from
- The City of Avalon
- Los Angeles Regional Water Quality Control Board
- State of California Clean Beaches Initiative Prop 13
- UPS Foundation
- Clare Boothe Luce Professorship
- Colleagues
- Steve Weisberg, Stanley Grant, Jed Fuhrman, Robert Mrse, Ryan Reeves, Cynthia Jensen-McMullin, Mark Bachman, Lisa Gilbane, Burt Jones

## Tide range and stage both important at most beaches