Appendix 3 Soiltechnics Soil Permeability Test Report...(BRE) Digest 365 (2007) “Soakaway...

Appendix 3

Soiltechnics Soil Permeability Test Report

Soiltechnics Limited

Registered in England 2680759

Registered office: Cedar Barn, NN6 9PY

Cedar Barn

White Lodge

Walgrave

Northamptonshire

NN6 9PY

t: 01604 781877

f: 01604 781007

e: [email protected]

w: www.soiltechnics.net

Dear Emma,

Re: Hall Lane, Kettering

Further to your instructions, we confirm completion of investigations at the above site and can now provide

the following report.

Objectives

We confirm our brief was to carry out investigations to determine the infiltration rate of the soils within the

grounds of the former Our Lady’s Convent School. The scope of fieldwork activities and position of exploratory

points were defined by your good selves.

This report has been prepared for the sole benefit of our above named instructing client, but this report, and

its contents, remains the property of Soiltechnics Limited until payment in full of our invoices in connection

with production of this report.

Brief description of the site and geology of the area

The site lies is a predominantly residential area of Kettering, Northamptonshire and is currently occupied by a

number of buildings; formerly used as a school and convent, surrounded by extensive overgrown gardens

including an orchard and pond, and former playing fields. The site slopes to the east by approximately 12m

across the site.

Inspection of the geological map of the area indicates the local topography of the area is formed in deposits of

Northampton Sand Formation (clay, silt, sand and gravel) overlying Whitby Mudstone Formation (formerly

Upper Lias Clay) (mudstone) at depth.

Emma Skelley

Wardell Armstrong LLP

Sir Henry Doulton House

Forge Lane

Etruria

Stoke on Trent

ST1 5BD

Date:

Your Ref:

Our Ref:

27.02.2013

L-STK2404U-002

STK2404U-L002 Page 2 of 3 27th

February 2013

Fieldwork

Fieldwork was carried out on 27th

February 2013 and comprised the formation of four trial pits. Trial pits

TP101 to TP104 were excavated to a maximum depth of 1.56m using a rubber tyred excavator. Logging was

carried out as trial pit excavations proceeded but were not entered at depths exceeding 1.2m. The excavations

were backfilled with excavated material compacted using the back of the excavator bucket. Whilst we

attempted to reinstate the excavation to its original condition some short-term settlement of the backfilling

materials may occur. A Geotechnical Engineer supervised the excavations. The positions of the exploratory

points are recorded on Drawing 101 (attached).

Soil infiltration tests were carried out in trial pits TP101 to TP104 at depths of between 0.84m and 1.56m. The

infiltration tests were carried out following the procedures described in the Building Research Establishment

(BRE) Digest 365 (2007) “Soakaway Design”. The position of previously undertaken exploratory excavations

and recent infiltration tests are shown on Drawing 101, appended.

Ground conditions encountered

The trial pit excavations encountered a similar profile of soils considered to be Topsoil, Northampton Sand

Formation overlying Whitby Mudstone Formation.

Topsoil consisting of medium dense dark brown sand and stiff orange brown clays with varying proportions of

gravel including sandstone and quartzite and extended to a maximum depth of 0.5m.

Northampton Sand Formation consisting of medium and high strength light brown orange sandy clay and

extended to a maximum depth of 1.3m.

Whitby Mudstone Formation generally comprised high strength light brown mottle light grey becoming grey

with depth slightly silty clay and extended beyond the termination depth of the trial pits.

No groundwater inflows were observed in any of the exploratory excavations.

Infiltration Potential

Infiltration testing was attempted to be undertaken following procedures described in BRE Digest 365

Soakaway design 2007. Water either failed to dissipated or dissipated insufficiently to derive an accurate

infiltration rate. On this basis we are of the opinion that the soils are effectively impermeable. Records of

infiltration testing undertaken are appended.

STK2404U-L002 Page 3 of 3 27th

February 2013

We trust this report provides you with the information you require, however, should you have any queries

please do not hesitate to contact us.

Yours sincerely,

Ross Carrington BSc (Hons), MSc, CSci, AIEMA

Geo-environmental engineer for Soiltechnics Limited

Reviewed by

Dr Matthew Hooper B.Sc. (Hons)., M.Sc., Ph.D., M.I.Env.Sc.

Senior Geo-environmental Engineer for Soiltechnics Limited

Encs Drawing 101 – Existing site layout and position of exploratory points

Trial pit / infiltration records

Standard Key to trial pit records

Key to legends (extract from BS5930 table 11)

Soils Sedimentary rocks

Topsoil Chalk

Made ground Limestone

Boulders & Cobbles Sandstone

Gravel Siltstone

Sand Mudstone

Silt Shale

Clay Coal

Peat/Organic clays Conglomerate

Composite soil types are signified by combined symbols.

Key to ‘test result’ columns

Column header Explanation

Type and depth Records depth that the test was carried out ie at 2.1m or between 2.1 and 2.55m

Result P – Pocket penetrometer result

V – Hand held shear vane result (KN/m2)

Carried out on

undisturbed samples or

in sides /base of trial pit

Key to ’sampling’ columns

Column header Explanation

From (m)

To (m)

Records depth of sampling

Type D – Disturbed sample

B – Bulk disturbed sample

J – Disturbed sample placed in sealed amber jar

W – Water sample

CBR Undisturbed sample in mould (California Bearing Ratio)

Water observations

Described at foot of log

Our Lady’s Convent School Hall Lane, Kettering

Title

Soil infiltration test (following principles of the Building

Research Establishment Digest 365 2007)

Co-ordinates

-

Trial pit number

TP101

Ground level

N/A

Date of excavation

27.02.2013

Groundwater observations

No groundwater encountered

Method of excavation

JCB 3CX

Location plan on drawing number

101

Report ref: STK2404U-002 Revision: 0

February 2013

Cycle number

1

Trial pit dimensions (width x length)

0.6m x 1.4m

Soil description and strata: Plot showing time against depth to water: Test observations:

0.870

0.870

0.870

0.865

0.850

0.840

TIME

(mins)

DEPTH TO

WATER (m)

Calculations:

Slight rise in water level over 252 minutes; soils considered effectively impermeable.

Brown sandy slightly gravelly clayey TOPSOIL. Gravel

consists of sandstone and quartzite.

Medium strength orange brown sandy CLAY.

(NORTHAMPTON SAND FORMATION)

High strength light grey mottled grey CLAY.

(WHITBY MUDSTONE FORMATION)

TRIAL PIT TERMINATED AT 1.21m DEPTH

Notes:

1. Trial pit side remained upright and stable

0.0

0.2

0.7

1.21

DESCRIPTION LEGEND DEPTH

(m)

0

16

60

92

143

252


Title



Co-ordinates

-

Trial pit number

TP102

Ground level

N/A

Date of excavation

27.02.2013




JCB 3CX


101


February 2013

Cycle number

1


0.6m x 1.4m


0.800

0.800

0.800

0.795

0.795

0.795

TIME

(mins)

DEPTH TO

WATER (m)

Calculations:

Slight rise in water level over 254 minutes; soils considered effectively impermeable.

Brown sandy clayey TOPSOIL.

Medium strength orange brown sandy CLAY.


High strength orange slightly sandy CLAY.


Light brown mottled light grey CLAY.



Notes:


0.0

0.15

0.45

1.0

1.07


(m)

0

28

69

101

152

254


Title



Co-ordinates

-

Trial pit number

TP103

Ground level

N/A

Date of excavation

27.02.2013




JCB 3CX


101


February 2013

Cycle number

1


0.6m x 1.4m


1.110

1.160

1.160

1.155

1.155

1.150

TIME

(mins)

DEPTH TO

WATER (m)

Calculations:

Initial infiltration into unsaturated soils then slight rise in water level over 254 minutes; soils considered effectively impermeable.

Brown sandy slightly gravelly clayey TOPSOIL. Gravel

consists of sandstone and quartzite.

Medium strength orange light brown slightly sandy CLAY.


High strength grey occasionally mottled light brown

CLAY.



Notes:


0.0

0.5

1.3

1.56


(m)

0

35

75

107

158

254


Title



Co-ordinates

-

Trial pit number

TP104

Ground level

N/A

Date of excavation

27.02.2013




JCB 3CX


101


February 2013

Cycle number

1


0.6m x 1.4m


0.840

0.870

0.880

0.890

TIME

(mins)

DEPTH TO

WATER (m)

Calculations:

Slight fall in water level over 111 minutes; insufficient data to calculate an infiltration rate.


Medium strength orange sandy CLAY.



Notes:


0.0

0.3

1.06


(m)

0

39

79

111


Title



Co-ordinates

-

Trial pit number

TP104

Ground level

N/A

Date of excavation

27.02.2013




JCB 3CX


101


February 2013

Cycle number

2


0.6m x 1.4m


0.710

0.720

0.745

0.760

0.770

0.790

0.795

0.800

TIME

(mins)

DEPTH TO

WATER (m)

Calculations:

Slight fall in water level over 149 minutes; insufficient data to calculate an infiltration rate.


Medium strength orange sandy CLAY.



Notes:


0.0

0.3

1.06


(m)

0

10

33

52

70

103

123

149

Appendix 4

Overland Flow Calculations

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Preliminary Attenuation Calculations

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Appendix 3 Soiltechnics Soil Permeability Test Report...(BRE) Digest 365 (2007) “Soakaway...

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