Page 137 - Kimihia Volume 2

SUBSIDENCE CONCERNS
Concern expressed by Kimihia School principal Mick Mather at apparent subsidence of the
school buildings at the end of 1988 prompted correspondence between architects and engineers.
Two of these letters clearly explain the situation.

17 January 1989 information of other shafts below school buildings.
ATTENTION: J W Enclosed is a plan of school showing
KELLAWAY REPORT ON relationships of photographs to buildings.
KIMIHIA SCHOOL R J PULLENGER 2/2/89
GROUND SUBSIDENCE
Mr Kellaway,
The entire building area with the exception of KIMIHIA SCHOOL GROUND
dental clinic, swimming pool and dressing SUBSIDENCE Refer to Mr Pullenger’s
sheds is showing evidence of a general report of 17/1/89
subsidence. Almost without exception, there is
visible evidence around base of buildings of an even So far, the degree of subsidence shown on the
subsidence of approximately 12 mm. photos does not appear to be cause for too much
The interesting fact is that the ground has concern. If it becomes worse I recommend that a
subsided so evenly throughout the entire length of consulting engineer specialising in soils and
all the permanent classrooms and admin block. foundations should be called in, as the origin of the
On the rear, side and front wall of rear c/ subsidence is not clear cut.
room block there is evidence of many cracks that For the record, earthworks were carried out
have been filled in with a thin mortar paint. 23 years ago. The building platform was
However, there are still portions of this 1.3 high constructed 146 ft long, of which the western
block foundation wall that shows newer cracks that section of about 30 ft comprised a wedge shape cut
run vertically from ground to floor level at centres with a maximum depth of 1½ ft and the eastern

as close as 200 mm apart. section of about 116 ft comprised a wedge shaped
I visited four private residence across the fill with a maximum depth of 5½ ft. There is no
road from school plus one at rear of school site and record of any unusual problems with compaction
1989 Staff found virtually no signs of any subsidence or underground water in the building area during
Rear: Heather Skelton, Alison Edward, Debbie Ellery, Jenny McRobbie. occurring. construction. Subsoil drainage had to be provided
Middle: Brenda Keats, Alison Mather, Linda Wright, Alan Somerville, Phillipa Rogers, The residential area 1/10th of a kilometre to later to drain wet areas in the playfields. The soil
Wiki Manaia. west of school on other side of Russell Road is is heavy clay.
Front: Tony Rogers, David Symes, Mick Mather, Lynley Chadwick, Max Carey. generally known to be riddled below with mine 1. Insufficient compaction of filling during
shafts. construction is not the reason for the subsidence
There is a coal mine approx. .75 of a because (a) subsidence has occurred as much over
kilometre NE of school building site. the cut area as the fill area (b) the dental clinic
All classrooms and administration block area has not subsided at all, although it is on
are constructed with permanent materials, eg the area of deepest fill (c) the principal states
continuous concrete or block foundations, and settlement on the area of greatest fill has
concrete floors. Note: all brick veneer walls above occurred only in the last 2 years - settlement of
floor level are not affected by cracks. poorly compacted soil is greatest immediately
All classrooms and admin are within the after completion of earthworks, reducing with the
subsidence area. passage of time and normally becoming negligible
The principal of school, Mr Robert Mather, within about 10 years (d) although the northern
told me that in his ten years of teaching at block was not constructed until 9 years after
Kimihia School that he has only noticed evidence the other buildings, the degree of subsidence is
of foundations cracking and subsidence occurring similar there to the rest of the building area.
during the past two years. During that time he 2. Shortcomings in building construction
showed me where the concrete paving had dropped seem unlikely to be the basic cause because of the

20 mm. widespread and relatively equal nature of the
The area he is referring to is in front of the 2 subsidence, even at the block which was
c/room block on east side of site. constructed later. (This block was constructed by
I believe that the ground at the rear of this the same builder who built the first buildings and
block has subsided considerably more than this. was not known as one of our best builders.)
Refer to photos 45, 46 also see photos 47 and 48 at 3. Slumping due to underground mining
rear of 4/class room west block. Mr Mather also operations is a possibility but does not seem likely
said that he knew of a mine shaft that runs north- given the widespread and generally even nature of
south across the main play field adjacent to the subsidence and the lack of subsidence on
the swimming pool. He did not know of any neighbouring properties and also at the