, 1870-12-09
DEEPENING THE CANAL,

we u4ve peeo ~! eM - FAa.:1A So
the contract and specifications for 'aeepen
ing the illinois and Michigan: :osnal fr9m
:Bdd9epprt 70 ~Lockpso1tts The .Sp1ect Of
liz liz. sender of: ths document, .we: suppose;
isto shdw that the better; Of the canal |
amer n j dug down, to the5propeE dspth. |
shhaail ,npt be less than forty feet, INSTEAD e
'thiia;issik thiiraay-sik feet, soa1 ;senaFks
-vratsrdav- .x.:..ssHl ->.a<! :,.-a *is: .
: Let Id examine the contract. ), The s;:t atst
specification sets forth That, Ths canal
ahau be 30 constructed it shall be fro:a
eight to tens:fsst deepes than ,;the
presant canal. snds=,st: .stha> lowest |
stage Of Lake Michigan: tho wster' sheil !,
be At 1esst aii1 feet ii depth below STANDARD
How water e. the, snrfaoe. Of tho lake.,
That is to say, that tha bottom OF :the /
canal sh III be si1 feet below tha: Ordinary
surface IT the Chicago Riref. From See 9;
! don Nd l to Section 7No: 16, Inclusive, re-,
I ths bo.tbm Of thes canal ahal be fofty.four
feet vidk, and the' alopes' one and q halt
feet 6 oee. On the remainder ofss the dis
tapoa, ,ths bottom shall NOT. be less than
forty feet in width. There are other pro; i
visions il regard. taszoek excavation, :ver-s
teal walb Hp-zap watlg slope vi, etc:, not
affecting the general width q 2! depth Of the
ditch, which we omit. :; :.
*@From lthese p1eyisions, Il Will be seen
that the Board Of Public Works, On behalf
of the city of Chicago have undertaken
10 defy the laws of nature, which prescribe
an aneietot fozty-dvs degrees for smbauk-
ments or slopes of earth excavations. The
coutract!calls for an angle Of fifty eight to
si1ty dsgreee,' below tho water surface.
Will an excavation in earth stand at such
an angle7 The present cut, below the
natural level, will average, say, nine feet,
six of il being filed with water: The
width Of the water: surface ia sixty feet.
The natural slopes would reduce the pres
; ent bottom to forty-eight Feet, calculated
!: On an, angle Of forty-6ee degrees What
= ever the original bottom width might Be IN
!, a1cess Of forty-eight feet, the inevitable
and constant effect Of time has been 70 re-
= duce it 10 forty-e'ght fest. -, ::
The contractors commence. on the pres.
, ent bottqm and Gnk it eight to ten feet
: deeper: TO comply with The specifications
: they are obliged 70 cut back into the ole
. slopes considerably to preserve forty-foul
+ OF forty feet 1t the neR, bottom. For, re
: / member That the new bottom win be ft
: tesn to sixteen feet Below the present auz
= face Of tha csuaL 4 depth Of fifteen fee
:: Of eazth excavation requires according +
! tbs laws pf nature, . slope. from the vert
-, cal of fffeen feet on each ;.sido, or thirt
! fest On bdth, which would reduce the ne'
=: bottom width to thirty, :feat:;, :; .Th
+ 4ontractoFs, under 81, orda1s Of ;';th
= hoard;, have cut steep sides, q
% t. ii secure forty 81 foity fest Il bV
~ =, tom iwid,b, when their job Is completed
- But, before they havea1 removed the
:, d1eages, the eazth from: above will begl
(: Ito elide dbwn into the bottom, and narro
= Il, and:xin continue doing 80 until It
-; - reduced. ito not more than Thirty fee
a. a. ! Eve1yIlaain, every thaw Of frozen" grour
= ormelt9d snow every. spring than fint
:: it's vAYi into this deep trench, will lsbof
a. reduce its width, and throw down deposl
~ and create bara on the bottom. -Alread
a.. We afe'infotmed, the work Of reduction b
., actively commented, in the. e1cavat
= part, and large quantities Of earth hare a
m down the nearly perpendicular sides a
AZ nar1oved! the channes IN many place
,;n There Is ho help OF remedy for: this to
IT, IT, deney, except BY walling, up the sides
~ 3 tho ditch with stone, which would c.
a milliana The very earth deposited nj
snd The margin Of the canal viii furnish I
lan l spring 1t6ne, when the frost is leaving
the ground,, abundance Of soft mud to 4
;on into the ditch and do~n its steep ban
b1te biz which viii, in turn, afford lucrative j,
,all tor contractors 10 tenose.
,sr s OF pruae4ce aud eonrnon sense, and i
CO., three million drainage job. can only be
garded asa blunder Of huge propo1tio