Instructions for observation of groundwater levels on housing sites

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C A N A D A

Ser

T r n

B92

no. 2

POL,

me l e v e l of water

in

key to many troubles encountered on housing sites--those

encountered by t h e householder as w e l l as the builder,

An excessively high water level may cause flooding sf

basements and o r a c k h g of house w a l l s , and impede t h e

fmct2on of septic tanks and drainage facilities,

An

unusually

low

some soils -th possible stmc-tural &image.

It

fn

groundwater level and

try

occur-

renoes

observat~ons

also

u s e f u l

under 0sPtai.n

conditions

in

plamlng design and construction detatls,

The purpose of this mote is to give instnactions

f o r m d d n g a simple ins%allatt;ion

In

sf which the groundwater l e v e l may be o b s e n e d , This

installation

consists essentially of

common

t

w e l l

a

screened

t o

e

vertical pipe and svnk in the ground f o r extracting

water

f r o m t h e

soil

connected to an open pipe trhioh extends above the ground surface, The w e l l point acts as a f f l t e r , keepfng out the sofl but allowfng

t h e goundwater l.levat1on Inside 2% t o change as fn t h e surrounding s o f l . The l e v e l of the water in t h e w e l l pofnt I s measured by

meens

of the open pfpe,

Equipment ( see Figure

I)

1 p o s t hole anger,

4

1 self-jettlrag w e l l point,

36

s u p p l f e r s of construct Lon eqqfpment ) with sharp drivfng

pafnt ( s f t n f l a r to S t a n g or G r l f f l n t y p e s ) .

1 standard galvanized i r o n p i p s , 1& inches

nomlnaX

[ s e e s e c t i o n '"~eliminary Work" f o p l e n g t h )

1 galvanized I r o n pipe cap, l & - h c h size, s m a l l hole d r i l l e d in one s i d e

1 cubic foot o f clean lrnffomn sand

3 pipe t e e 1%-fnch nomfnal d f m ~ l e r

2 _{pieces p i p e , 1)-inch nominal diameter, 6 inches l o n g} 1 pfpe cap, J.$-inch nomlnal d f a m e t e r

1 r e d u c i n g coupl5ng, 14 to 3/4-~nch nominal diameter

1 garden hose and f l t t f n g s Pre l f m l n a r y Wopk

The first a p e r a t i o n is to m a k e an auger borlng to see what

k i n d of s o i l f s present end to f i n d the approximate l e v e l of the

groundwater t a b l e . Choose a spat where the i n s t a l l a . a ; i ~ n wf ll be

convenient to read in summer and w i n t e r , but w i l l not be unsightly

or s u b j e c t to damage. If the s i t e is sloping, choose a l o c a t i o n

on the u p h i l l s l d e of t h e l o c a t f o n of any s t r u c t u r e , Et 1s no$ necessary to carry this bor2ng deeper than 10 or 12 feetB a%nce

if

the groundwater is below t h i s , I t Sa u n l i k e l y to have an e f f e c t

on

DurXns bor2ng o g e r z t l o n s , k a e p o ~ a : ~ o S u l rocord of tho

Ir";nd of aofl cnco~'a-Loi-cd n'r. v a r l d u 3 O ~ p t h o , noClns In p m C i c u l a r t h 3 dcpkh or any chc:lcoo. When @wuXId;~ake~ $3 cncountesod or t h o r e q u i r a d d c p t h of borTng f s ??@ached, 4 9 nocesaary t o w c L t u n t i l . t h o level of t h o r-rat02 _{b o c ~ ~ i ; z s s ~ o ~ d y in Qhc holo. T h l s may be a}

mae;toi. of mTnuJ~os in a sand er gravel. sofXB or days in a c l a y ' soil, At cny r a t e , chock " t h e %rater l e v a 1 in t h o , open bolo p e r * i o d i c a l l y

until.

no

The ~roundsaQar l e v o l may vary as much as 8 or 10 f e e t in

one location bo-k.rcon v m t and dry seaaens. In m o s t p a r t s o f Canada

f"2s u n u a l l g hlghsst batman November 'and A p r i l and lot10 s t ab.suk

September. Td:ilng i n t o account th3 t i m e of y e w at v ~ h i c h t h e

b o r i n g l o mado and tho obssr-isd g r o a n d w a t o r l e v e l , an estfmate of the dopth of borirr~ and l e n g t h of 1 s - l n c h pipe required may be m a d e ,

The c.:oZI. Zjoln-3, wh3n p l a c e d in t h o b-'t;tlorn o f the bore hole, should br c o m p l ~ t ~ 1 y below the groundtrster l e v e l at a l l tiniss of g e a r , and

the &-inch p i p a , w b n connected to"the t o p of the w a l l point, should

eatond 18 inches above t h o qurface o r t h e ground. The pipe may then

be cut to th9 requzrod l e n g t h and throadod at both ends. Ttro or

three short pipe sectiana may be prererable to one long z e c t l o n if

t h e assembly is to be driven d o m e

It

d e p t h and n u h e acme Lima keep t h e scrssn openings f r o m becoming

c l ~ g g ~ d by fino ~ 0 2 1 .

In sand cmd _{p,ravol ~ 0 1 1 , t h e bore hole may n o t s t a y open}

below the water l e v e l , ~i'tok t h e ~1011 polnt and 1;-inch plpe ars

Slrmly c a m e c f ; ~ d mrl loprased i n t o t h e hole, ft w111 therefor0 h e l p if a garden hose is a t t a c h e d to t h e top of the p i p e ( s o s j e t t i n g assom'oly in F l g u r e I), and the w a t e r pressure turned on f u l l . . Due

to the b a l l valve of a self

-

f o r c e d out twough the apen9ngs In t h e nose of the w a l l pofntg

l o o s e n i n g tho soil belot-re At the same tims the assembly should be

pushed or h ~ m m z r a d dorm

u n t i l

l e v e l . If l a r g e stones a r e e n c o u n t e ~ e d I t may n o t be p o s s i b l e t o

do t h i s , m d m o t h e r hole may have t o b e t r i o d , Heavy driving with

a hanmcr s h o u l d be done w i t h care. F h S l e d r l v i n g , it is ak~rays

b e s t to keep thg p9pe czp in p l a c e and use a h a r d ~ m o d or plywood

cushion betr-men t h e p i p e cap and harnrrzr. When tine Installalion is

c o n p l a t e , t h o hole is b 2 c l ; f i l l e d I-rith tg~nped s o i l , a snail amount

of which is heapcd up arollpld the pipe at t h e ground suri'aco,

In clCg o r s o f t soil, the s i d e s of $he bore hole ~ ~ 1 1 1 u s u a l l y

however, th5 s o l 1 may shpreas over the screen openinga in t h e t . ? e l l

point, p r e v e n t i n g water f r o m flowfng in or ou% r e a d f l y , After t h e

bore bole 5 s carr9ed to the r e q u f r e d depth agld the well p o f n t m d

pfpe are l o w e m d f n t o p l a c e , ~ b e r e f l o ~ s ~ clean uniform sand should

be dropped d a m the hole to s e t t l e

fn the

the w e l l pofnt sereeri a d t b sup~oundlng sofl, If e h f a sand carm

be tamped f Prnly with a l o n g vroodan rod, b e s t r e s u l t a wf 11 be

o b t p f n e d , The sand b a e k f l l l a h o d d extend to withan 2 or

3

of the g ~ o u n d s u ~ f a o e , Above thPs, the sofl rarnosred f ~ o m the hole

by the auger should be tamped f l m l y back Snto p l a c e , le avfng a

s m a l l amount of excess at t h e ground s n r f k e , If g a l l o n of clean

w a t e ~ Is thgn p o y e d 'dam t h e p i p e , t h f s ~1111 f l u s h o u t the screen

and Improve the parfosmance o f t b fnstallatfon,

The water I s v e l witbfn ths pipe m a y be mad s u f f i c i e n t l y

accurately by meana of m e t a l l i c aurveging or o t h e r canvas tape

which wP11 n o t s t r e t c h ~ p p r z e $ a h ~ y o Cloth tape or p i e c e a of s t r i n g

are unsuitable and snould nwt be ~ s s d ~

A smalz weight sueh as a f fshfng sfraker should be fastened

t o the end of t h e tape, If the tape %a then whitened for a s h o r t

distance f r o m t h e end w f t h common chalk, ths l e v e l of" t h e p r a t e r G f l l show c l s a ~ l y , If the tape f s l s ~ % r e d t o rn _{even foot mark at}

the t o p of the pfpe, the w8tted length may be s u b t r a c t e d f r o m thf s

reading to g i v e &he depth of water, Readings should be taken to

the nemest

114

e v e ~ y raadf ng,

The, elevatSon of the t a p of the p%pe should be r e l a t e d t o

a bench m a ~ k in the a ~ e a ,

In

water may be recoydad at mekPy f n t e ~ v a l s , along

wf

p a l nrall, temperatura md snow condl t Xon5,

The DPvisSon of Bufldllng Research w i l l be fntemsted to h e a r of

unusual groundwater conditions or to o r f e ~ advice 3f t r o u b l e I s 'ncountered in the E n s t a l l a t f o n of equfpmenk sueh as that

Equipment f OF Groundwater Table Observation Pips

L e f t t o r i g h t :

4

Well polnt w i t h p i p e attached