2011-11-15 Knock Airport Public Water Supply

E>,\LL I NII C I V I C Orr I CE.S, AKK,\N F LIICL E> ALLlI\A CO. M AYO .
..
MEMO
To:
Paddy Mahon, Director of Services
From:
Eddie Munnelly, Senior Executive Engineer
Re:
Knock Airport Public Water Supply - EPAAudit
Date:
15th November, 2011
Ref:
DW20l0/145
The Environmental Protection Agency carried out an audit of Knock Airport Public
Water Treatment Plant on the 8 th October, 2010. This audit was carried out to assess
the performance of the local authority in providing clean and wholesome drinking
water via the Knock Airporl Public Water Supply.
The EPA has outlined numerous recommendations to improve operations at the
Knock Airport Treatment Works and has requested Mayo County Council to report
on actions to address these recommendations.
RECOMMENDATIONS &ACflONS
Source Protection
Recommendation
a. The Water Service Authority (WSA) should cany out a walk-over survey
of the source intake area and its surrounds to ensure there is no illegal
dumping on the sand and gravel quany sites and to identify any farms
within the source catchment.
Action
A walk-over survey of the site was conducted and no evidence of illegal
dumping was found. However as a precautionary measure the WSA are
looking into erecting a higher security fence around the site boundary to
protect the PWS source from illegal dumping.
The agricultural acLivily in the immediate vicinity of the source intake is
not intensive in nature and there is no history of land spreading or
farmyard manure storage in this area. However, the area is being
continuously monitored and the landowners are aware of the requirements
of European Communities (Good Agricultural Practice for the Protection of
Waters) Regulations. All other lands within the source catchment are
predominantly disused sand and gravel sites.
Timeframe:
6 months
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09& 7 6 1;;8/76 1 99
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Recommendation
b. The WSA should liaise with Tobin Consulting Engineers Ireland in
determining the Zone of Contribution (ZOC) f or this supply and confirm
whether the supply is groundwater or spring source.
Action
The EPA has delineated the ZOC for the Knock Airport Public Water
Supply source under the National Groundwater Monitoring Programme
dated August 2011 which was obtained from the EPA websile. This report
described the site and source as "a former sand and gravel pit where the
water in the pit is essentially a groundwater seep whereby the water in the
pit is a representation of the groundwater table in the surrounding sand
and gravel aquifer (which is higher than the excavated depth of the pit).
The standing water in the pit therefore represents groundwater, plus
rainwater". From this definition the WSA has interpreted the source to be a
Groundwater.
Timeframe:
Complete
Recommendation
c. The WSA may aLso consider the amendment of the buffer zone (by way of
formal agreement with the EPA) once the EPA's ZOC report is issued to
theWSA.
Action
The WSA will consider amending the buffer zone on further EPA
instructions once the EPAs ZOC report for this site has been made available
to the WSA from the EPA.
Timeframe:
Ongoing
Recommendation
d. The WSA shall inform farmers about the buffer zones and set-back
distances as outlined in the European Communities (Good Agricultural
Practices for the Protection of Waters) Regulations 2006 (SI No . 378 of
2006 and any subsequent amendments that are made to these buffer
zones.
Action
The WSA will inform farmers within the buffer zones once they have been
agreed formally with the EPA.
Timeframe:
Ongoing
Fhone:
09676 100/ :'& 101
Pa~c2or 9
F ax:
096 7' 6 198 /
76 I 99
5AI I INA C.IVIC: OFFIc:r S, ARRAN F I AC:f, 5 Al I I I\A, C.O. MAYO.
MEMO
Recommendation
e. Once the' source is detennined (i.e. Spring or Groundwater source) the
WSA should ensure thatfuture Drinking Water Returns data is updated to
reflect any amendments.
Action
The relevant personnel have been advised that the source is a Groundwater
as defined in the Cb) above. The WSA can confirm that the necessary
change has already been made in EDEN.
Timeframe:
Complete
Recommendation
The WSA should cap the abandoned groundwater well next to the source
intake area and should ensure that the source intake area is made secure.
f
Action
A concrete cap will be constructed over the top of the abandoned well. This
capping will be constructed in such a manner so as no concrete will enter
the abandoned well during construction.
Timeframe:
1 month
o Chlorination and Disinfection
Recommendation
a. The WSA should review the contact time for chlorine disinfection to
ensure that the correct dose and time (0-5 mg/lfor at least 30 minutes) is
being achieved as recommended by the World Health Organisation. The
WSA should submit a calculation of the contact time to the Agency.
Action
Raw water is pumped from Lhe source approximately l.Skm to a 36m3 clear
water tank. It is upon leaving this tank, in the outlet rising main, that the
raw water is dosed with Sodium Hypochlorite 14/1S%, by flow proportional
chlorine pumps Cduty/standby). The chlorinated water is then further
pumped to a 400m3 reservoir situated within the boundary of Knock
airport.
While the chlorine monitor is located close (approx. lOm) to the chlorine
dosing, the WSA believes that adequate contact time is being achieved as
the chlorinated water travels approximately 2osom in a 100mm rising
main to the airport reservoir. The volume of water in the rising main at any
one time is 16m3 and the average daily usage at thc Ajrport is ssmJ/d.
FhClnC' 096' ;6 100/ ;C: I O I
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MEMO
Therefore ample contact time is achieved in the nsmg mam prior to
entering the reservoir.
Timeframe:
Complete
Recommendation
b. The WSA should review the location of the continuous chlorine monitor
post disinfection and, in light of the outcome of investigations into
recommendation (a) above, shall ensure that the monitor is located after
the appropriate contact time has elapsed.
Action
The WSA are reviewing the layout of the entire scheme and on further
investigation and negotiations with the HSE, EPA and the Airport
Authority the locations of thc chlorine monitor can be reviewed at a further
date.
Timeframe:
3 months
Recommendation
c. The WSA should ensure there is automatic switch over between the duty
and standby chlorine pump in the event offailure of one of the pumps.
Action
The WSA has contacted the Mechanical and Electrical Department to carry
out works to ensure that there is automatic switchover of chlorine dosing
pumps in the event offailure of one of the pumps.
Timeframe:
3 months
Recommendation
d. The WSA should investigate the cause for low residual chlorine levels at
the kitchen sink tap in the Knock Airport Canteen and put in place
corrective action to ensure residual levels in the network ensure adequate
disinfection. The "WSA shall liaise with the HSE and Connaught Airport
Authority Ltd. in your investigations into this issue.
Action
The WSA carried out an investigation into the chlorine dosing regime at
Knock Airport PWS.
As part of this investigation the chlorine dosing was increased gradually
and the chlorine residual measured at various locations throughout the
r hont""
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terminal building. The following Table (Table 1) includes the WSA chlorine
residual resul ts.
Table 1 Chlorine Residual Results Table
T
I Ippte
onlinc chlorine
mOllitor
manual clllorine
Ground
e
(at pump house)
residual
(tap on Resermir)
Iw
rngfl
rug/ '
floor sink
in
Bar
rugfl
0.85
0·95
1. 2 9
1.06
1.06
0 .25
0.28
0 .27
:&/09/11
'lA/ 09/ 11
23/ 0 9 11
26/ 09, 11
'1:'7/ 09111
:!S/ 09 11
ag/ OQ, 11
LOS
;¥)/ 09 / n
<14/ 10/ 11
1.00
]-45
0.46
0-45
0-46
0·35
0·55
0 .65
0·35
0·38
I
I
Upstairs
Kitchen
sink
Upstairs
Sink in
Bar
rug/ '
mgfl
0.06
0.08
0.05
0.03
0.04
o.o~
0-43
0 .5 8
0.10
0.15
e
d
As can be seen from the Table 1 above there is a considerable discrepancy
between the ground floor and the first floor within the terminal building.
Upon initial investigations and informal discussions with the Airport
Authority it seems that there is a lime softening filter and a pressurised
tank supplying water to the kitchen and bar on the first floor, possibly
causing the low chlorine residuals.
The WSA are in the process of organising a formal meeting with the HSE
and Knock Airport Authority to find a solution to the above problem.
Timeframe:
2 months
Recommendation
e. The WSA should monitor residual chlorine levels post the reservoir at the
airport to ensure a satisfactory level of disinfection is provided for in this
PWS.
Action
The WSA are reviewing the layout of the entire scheme and on further
investigation and negotiations with the HSE, EPA and the Airport
Authority the locations of the chlorine monitor can be reviewed at a further
date.
Timeframe:
3 months
Fhone:
09676 100/ ;'6 10 1
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9 8 /76 199
~ALLlNA CIVIC OFFiCeS AKKAN f LACE., E>ALLlNf\
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MEMO
Recommendation
The WSA should review the low alarm settings on the continuous chlorine
monitor to ensure that adequate chlorine is maintained in the treated
water in order to provide sufficient disinfection in the network. Alarm
settings should be set having regard to the EPA's circular ofAugust 2008.
f
Action
The WSA has reviewed this and confonned to the EPA circular 2008. The
parameters at the dosing pump house have been adjusted from 0.2mg/1 l.smg/l to oAmg/l - l ·smg/1.
Timeframe:
Complete
Recommendation
g. The WSA should put in place a documented procedure on how to respond
to a chlorine alarm when it is triggered. This procedure shall include
names of persons responsible for responding to an alarm, actions to be
taken, a standard check sheet of items to be checked in the event of call out
and contact details for senior management in the Local Authority and the
HSE.
Action
There is a procedure currently in place at every plant throughout the
County,
Timeframe:
Complcte
Recommendation
h, The WSA should take a daily manual chlorine residual test post the
contact time and record the result. The WSA should also record the
residual chlorine readout from the online chlorine monitor at the same
time the manual sample is taken . An investigation should be undertaken if
there is a discrepancy (e.g. >10-20%) between the residual chlorine
readings on the chlorine monitor and the results from the manual
residual chlorine test carried out daily at the plant.
Action
The WSA carried out an investigation into the chlorine dosing regime at
Knock Airport PWS.
As part of this investigation the chlorine dosing was increased gradually
and the chlorine residual monitor at various locations throughout the
P:ure 60f9
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terminal building. The following Table (Table 1) includes the WSA chlorine
residual results.
Table 1 Chlorine Residual Results Table
I Date
,
onllllc ch lurine
manual chlorine
monitor
(at pump house)
residual
(tap on Rescryoir)
mg/l
mg/I
0.85
0 ·95
1.29
1.06
1.06
0.25
20/09/11
21 09/11
23 09 11
26 091 11
I 271 091 11
, 28 091 11
291 091 11
30 09 11
04. 10 11
1.05
1.45
1.00
0.28
0,46
0·45
0,46
0·35
0·55
0.65
Ground
tloor sink
m
Bar
mg/I
I
Upstairs
Kitchen
sink
mg/I
Upstairs
Sink in
Bar
mg/I
0.06
-
0.2;7
,f
0·35
0.3 8
I
0-43
0.58
0.08
0 .05
0.03
().03
0.04
0.10
I
0.15
As can be seen from the results there is a discrepancy of >10-20% between
the residual chlorine readings on the chlorine monitor and the manual
residual chlorine.
The reason for this is that the capacity of the reservoir is 420m3 and usage
at the Airport is an average of 50m3/d.
A solution to this problem would be to supply the Airport Terminal directly
from the rising main bypassing the Reservoir if necessary. This will have to
be discussed further with the EPA, HSE and the Airport Authority.
The WSA arc in the process of organising a formal meeting with the HSE
and Knock Airport Authority.
Timeframe:
2 months
Recommendation
i. The WSA should ensure that the chlorine monitor and/or handheld
analyser are regularly maintained and calibrated in accordance with the
manufacturer's instructions. The WSA should ensure calibration
certificates are filed and available/or review during any subsequent EPA
audits or inspections.
Action
This is currently being carried out and certificates are filed and available
for review on request from the Ballina Civic Offices.
Timeframe:
rhone,
09676100/76101
P3II,C 7of9
E>ALLlI'\A C I VI C OFF i CeS. ARRAN f LACe. E> ALLlNA. Co. M AY O .
MEMO
Complete
o
Distribution System
Recommendations
a. The WSA should ensure that the service reservoir is inspected and cleaned
out on a regular basis and any maintenance and repairs completed as
soon as possible after the need has been identified.
b. The WSA should ensure that all vents on the reservoir are secured against
ingress of animals or deliberate introduction of any contaminant or acts
of vandalism.
Action to a & b
The WSA are in the process of organising a formal meeting with the HSE
and Knock Airport Authority at which time the WSA will affirm the duties
of the Airport Authority in relation to the reservoir.
Timeframe:
2 months
Recommendation
c. The WSA should ensure that there is complete mixing (i.e. no preferential
flows through the tank) in the reservoir and that no stagnant areas exist.
Action
This is currently being investigated.
Timeframe:
3 months
Recommendation
d. The WSA should ensure that sealed and lockable hatches are installed on
all inspection points and valves access points where there is access to
treated water.
Action
The WSA are in the process uf urganising a furmal meeting with the HSE
and Knock Airport Authority at which time the WSA will affirm the duties
of the Airport Authority in relation to the reservoir.
Timeframe:
2 months
Phone,
09676 100/ ;6 10 1
Poae 80f9
F <lX:
09 b 76 I 98 /
1 tJ 1 99
E:> ALLlNA C I VIC OFF i CeS. ARKAN F LACC, E:> ALLlNA, Co. M AYO.
MEMO
o
Management and Control
The WSA shall carry out regular raw water monitoring on this PWS source
and analyze any tends in the raw water quality. Such monitoring for E. Coli
bacteria, as an indicator of trends in assessing water quality and to
determine whether the degree of treatment and controls in place in this
supply are adequate.
Action
The relevant personnel have been advised of this requirement and a
moniloring regime for the raw waler is currenlly being pUl in place.
Timeframe:
Ongoing
Trusting this is the information you require.
Yours sincerely
Martin O'Grady AE
Mayo County Council
rhone:
09676 100/76101
P':II~e
90f9
Fax: 09676198/76 1 ,/9