Water wells and groundwater supplies : the protection of water quality in bored and dug wells

3 Pages·1994·0.61 MB·English

10/1B/95 16:24:66 —) 314 0541 I1.O.E.E. Page 002
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Ministry ot Environment and Energy
üg
1994
Wells and Groundwater Supplies: The
Protection of Water Quality In Bored and Dug
Wells
Iiiiproper well construction and the failure to carry and dug weUs
out routine preventative maintenance on wells NOTE: Further information on the following topics
results in contamination of a well supply and is available from various government agencies
the subsequent creation of a hazard to both public upon request:
health and safety. Because bored and dug wells • Wells and domestic water treatment devices:
are particularly susceptible to deterioration of their contact the nearest regional or district ott ice of
sanitary integrity, maintenance on these types of Environment and Energy Ontario
wells is especially important. Drilled wells, • Private well water quality sampling and
because of differing technology, are referred to in a standards: contact the local medical officer of
sepai'ate tact sheet. health
Ontario Regulation 903, section 20 pertaining • Pesticide and other agriculture chemical use
to water well construction iii Onlario, states Ilial, id 1 tax dli ig: coi ita ct [lie local agricultural or
"The well owner shall maintain the well at all district office of the Ministry of Agriculture
Liii ies after Ilie coutple lioi i date ii L a II MiLl iCE Food and Rural Affairs (OMAFRA)
sufficient to prevent the entry into the well of
surface water or other foreign materials."
FACTORS CONTRIBUTING TO THE
'l'he purpose of this information sheet is to
assist those people relying on bored or dug wells DETERIORATION OF WELL WATER QUALITY
as a source of water in maintaining or upgrading A poorly maintained or constructed well can result
the well supply and the quality of the well water to in the bacterial and/or chemical contamination of
acceptable standards, While in some instances the
the well water, The rn oaF corn ii Ca ise of these
upgrading work can be done by the owner, the well water quality problems is poor-quality soil
em ploy iii en F Ci a cam pete nt well cciii tractor seepage and sunta'.e waters iii the
advisable.
immediate vicinity of the well having direct access
to the well. Bored wells in Ontario are usually
WELL REGULATIONS constructed by a bucket or auger-type rotary
machine whose boring operations produce holes of
C)nta rio Rec;i i lath-in 903 under the Onta rio Water 7b centimetres or more in diameter and which are
Resources Act provides for the licensing of water usually cased or lined with a concrete pipe having
well contractors a nil well technicians by the an inside diameter of 60 centimetres or more.
Ministry of Environment and Energy. This Large diameter wells are also constructed with
regula Lion prescribes the coi istructior i stax ida na other types of equipment, such as backhoes. Good
that all contractors, including private homeowners, sealing around the casing or liner in these types of
must adhere to in the construction of all wells. The wells is ha to achieve a nil maIntain heca use
attached figures illustrate the minimum sealing the potential for setflgjn,ent of both seal and casing.
requirements of Ontario Regulation 903 for 10 LEGISLATIVE UBRARY
tFore4NT#
RECEIVED
Ontario 0C1181995
4
— 3
1
0CT107995
C
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Iridicalors thai lIw well sealing is ii should be replaced iii iltedid tel au ice it will
and that surface contamination is gaining access to give contaminants direct access to the well.
the well include: b) The well casing cap should be a minimum of 30
1.) the presence of coliform bacteria in counts centimetres above ground surface and should
exceeding recommended limits set by health not he cut off and buried.
authorities; c) No unsealed openings should exist in the wall
2) changes in the quality of the water such as or along the joints of cement-tile casing above
turbidity, color, taste, or odor, especially after the water level in the well, If any are found
a rainstorm or snow melt; they should be made watertight with a durable
3) rapid or large changes in the water level in the sealing material applied preferably from the
well especially after a rainstorm or snow melt; outside the casing. Subsidence, corrosion or
4) cascading or seej 'iiig ol water and br staining other cdii occur and will allow surface
along casing above the water level in the iccll; waters or shallow seepage waters to enter
5) the presence of biological material such as directly into the well.
animals or roots in the well; d) The circular space outside the casing should be
o) the presence ot unsealed or parted joints or tilled with a suitable sealant, such as Portland
cracks in the casing well or cover; cement grout, concrete, bentonite or equivalent
7) the settlement of soils around the well to or commercial slurry or clay slurry to prevent
below ground surface; surface water runoff form seeping directly into
8) the presence of roof drainage pipes in the well; the well around the casing! Where settlement
9) the absence of a watertight cover set at an of the sealant has occurred, the area around the
appropriate height above the ground surface; casing should be excavated and backfilled with
10) 1-ha nges in the chew ical q I 11 tv of the well a well —coni pat-ted, sin tafil e gin ii ti rig or sea I 'S
water as detected through laboratory analysis. material.
e) If the general land surface around tIe uell is
PREVENTATIVE MAINTENANCE MEASURES depressed or susceptible to flooding, it should
be raised and regraded so that it slopes away
There are sonic inca si I res that t'a n he taken in the from the well. The land surface around the
care and maintenance of a well that the well casing should be at least tS centimetres
Iioiiieowiier should be aware of, which will help lo above ground level.
provide good quality water. These measures U If the well casing had settled, it may be
iziclucle: necessary to extend the well casing and regrade
the general land surface away from the well.
g) The well water's surface should be inspected.
1) WELL LOCATION
and any debris found floating on the surface of
To safeguard a well supply from contamination, the water reninved froni the well
ito activity that could resull iii the well's h) The connections at the well casing for pump
contamination should be performed within the and electrical lines slioukl be ii dde w atertiglil
area of a well It is advisable that refuse, manure, and properly sealed. The casing may have to
petroleum products, salt, fertilizers, pesticides are be excavated to replace the seal it it has tailed.
other potential contaminants not be stored, used or i) All wells that have been repaired should be
disposed olin the vicinity of the well. When chlorinated and tested for potability
mixing pesticides, the water supply line from the immediately after the work has been
pressure system should he equipped with a completed.
backflow prevention device. j) All abandoned wells must be sealed in
accordance with Ontario Regulation 903.
2) WELL CONSTRUCTION
a) the well casing should he securely in place
and watertight. It damaged or cracked, it
2