Neepsend Redevelopment Detailed Design Report – Techni Consultants

Associated Documents Main Report Detailed Design Report

Appendix A Ground Model

Appendix B Contamination

Appendix C Foundations and Substructure

Appendix D HQ Superstructure

Appendix E Terminus Superstructure

Appendix F Bridge Superstructure

Appendix G Drainage

Appendix H Project Management, Team Management and Construction Management

Table of Contents ASSOCIATED DOCUMENTS ................................................................................................................................... 2

TABLE OF FIGURES ............................................................................................................................................... 4

0. EXECUTIVE SUMMARY .................................................................................................................................. 1

1. INTRODUCTION ............................................................................................................................................ 1

2. SITE CONSIDERATIONS .................................................................................................................................. 2

2.1. EXISTING GAS PIPE .................................................................................................................................................. 2

2.2. RETAINING WALL ..................................................................................................................................................... 2

2.3. LIVE SERVICES ......................................................................................................................................................... 2

2.4. EXISTING TRANSPORT LINKS ...................................................................................................................................... 3

2.5. MINING ................................................................................................................................................................. 3

2.6. ENCLOSURE WALL ................................................................................................................................................... 4

2.7. FLOOD RISK ............................................................................................................................................................ 4

3. CONTAMINATION ......................................................................................................................................... 5

3.1. SOURCE-PATHWAY-RECEPTOR ANALYSIS ..................................................................................................................... 5

3.2. CONCEPTUAL SITE MODEL ........................................................................................................................................ 5

3.3. IDENTIFYING CONTAMINATION .................................................................................................................................. 6

3.3.1. Identification ................................................................................................................................................ 6

3.3.2. Soil Guideline Values .................................................................................................................................... 6

3.3.3. Identifying Contaminated Areas ................................................................................................................... 6

3.4. REMEDIATION STRATEGY .......................................................................................................................................... 7

3.4.1. PH and SVOC Remediation ........................................................................................................................... 7

3.4.2. Heavy Metals ................................................................................................................................................ 7

3.4.3. Water Soluble Chlorides and Sulphates ........................................................................................................ 8

3.4.4. Groundwater Remediation ........................................................................................................................... 8

3.5. REMEDIATION TIME LAPSE PROCESS ........................................................................................................................... 9

4. GROUND MODEL ........................................................................................................................................ 10

4.1. BOREHOLES .......................................................................................................................................................... 10

4.1.1. Borehole Data Summary ............................................................................................................................ 10

4.1.2. Ground Section Locations ........................................................................................................................... 10

4.2. RESULTS .............................................................................................................................................................. 10

4.3. FURTHER SITE INVESTIGATION ................................................................................................................................. 11

4.3.1. Boreholes and Trial Pits .............................................................................................................................. 11

4.3.2. Testing ........................................................................................................................................................ 11

5. SELECTED SITE LAYOUT ............................................................................................................................... 14

5.1. SITE LAYOUT SELECTION ......................................................................................................................................... 14

5.1.1. Selected Site Layout – Plan Overview ......................................................................................................... 14

5.1.2. Site 3D Model ............................................................................................................................................. 15

5.1.3. Selected Site Layout – Sections ................................................................................................................... 15

6. HEADQUARTERS BUILDING ......................................................................................................................... 16

6.1. SUPERSTRUCTURE .................................................................................................................................................. 16

6.1.1. Structure Overview ..................................................................................................................................... 16

6.1.2. Atrium ......................................................................................................................................................... 16

6.1.3. Double Glazed Glass Façade ....................................................................................................................... 16

6.1.4. Structural Detailing .................................................................................................................................... 17

6.1.5. Floorplan ..................................................................................................................................................... 17

6.2. CONSTRUCTION SEQUENCING .................................................................................................................................. 18

6.3. DESIGN PROCESS ................................................................................................................................................... 18

6.4. FOUNDATIONS ...................................................................................................................................................... 19

7. TERMINUS .................................................................................................................................................. 21

7.1. STRUCTURE OVERVIEW .......................................................................................................................................... 21

7.1.1. Roof Structure ................................................................................................................................................ 21

7.1.2. Steel Frame .................................................................................................................................................... 21

7.1.3. Lateral Stability .............................................................................................................................................. 22

Below Roof Level...................................................................................................................................................... 22

At Roof Level ............................................................................................................................................................ 22

7.2. CONSTRUCTION SEQUENCING .................................................................................................................................. 22

7.3. FOUNDATIONS ...................................................................................................................................................... 23

8. BRIDGE AND SUPERTRAM ........................................................................................................................... 24

8.1. SUPERSTRUCTURE .................................................................................................................................................. 24

8.1.1. Structure Overview ..................................................................................................................................... 24

8.2. CONSTRUCTION SEQUENCE ..................................................................................................................................... 25

8.3. FOUNDATIONS ...................................................................................................................................................... 26

8.4. TRAM ROUTE........................................................................................................................................................ 27

8.4.1. Route .......................................................................................................................................................... 27

8.4.2. Route Foundations ..................................................................................................................................... 27

9. ASSOCIATED DRAINAGE .............................................................................................................................. 28

9.1. DRAINAGE OVERVIEW ............................................................................................................................................ 28

9.1.1. Drainage Masterplan ................................................................................................................................. 28

9.2. SUDS SELECTION RATIONALE .................................................................................................................................. 29

9.3. DRAINAGE DESIGN ................................................................................................................................................ 29

9.3.1. Filter Strips and Swales ............................................................................................................................... 29

9.3.2. Green Roof .................................................................................................................................................. 30

9.3.3. Storm Tank ................................................................................................................................................. 30

9.3.4. Balancing Pond ........................................................................................................................................... 31

Pond Runoff ............................................................................................................................................................. 31

9.4. FINAL RUNOFF ...................................................................................................................................................... 32

10. EMBODIED CARBON CONTENT .................................................................................................................. 33

10.1. Headquarters .............................................................................................................................................. 33

10.2. Terminus ...................................................................................................................................................... 34

10.3. Supertram Bridge ........................................................................................................................................ 34

11. PROGRAMME AND PHASING .................................................................................................................... 35

11.1. PHASING ............................................................................................................................................................ 35

11.2. PROGRAMME ..................................................................................................................................................... 38

12. COSTING ................................................................................................................................................... 40

12.1. FULL COST BREAKDOWN ...................................................................................................................................... 40

12.2. EXPENDITURE THROUGHOUT THE PROJECT .............................................................................................................. 41

12.3. PHASE COSTS ..................................................................................................................................................... 41

13. RISK ASSESSMENT ..................................................................................................................................... 42

13.1. OPERATIONAL AND FUTURE RISKS .......................................................................................................................... 42

14. EVALUATION ............................................................................................................................................ 43

14.1. MAJOR ASSUMPTIONS ......................................................................................................................................... 43

14.2. MEETING OF THE BRIEF ........................................................................................................................................ 43

14.3. FURTHER DETAILED DESIGN REQUIRED ................................................................................................................... 43

15. CONCLUSION ............................................................................................................................................ 44

16. BIBLIOGRAPHY ......................................................................................................................................... 45

Table of Figures Figure 1: Retaining wall section ................................................................................................................................................. 2

Figure 2: Existing Transportation routes ................................................................................................................................... 3

Figure 3: Mining details in Sheffield, Source: (Coal Authority, 2015) ....................................................................................... 3

Figure 4: Flood plan, Source: (Environment Agency, n.d.) ........................................................................................................ 4

Figure 5: Site conceptual model ................................................................................................................................................ 5

Figure 6: Aliphatic & Aromatic Compounds contamination areas ............................................................................................ 6

Figure 7: Heavy metals contamination areas ............................................................................................................................ 6

Figure 8: In-situ thermal desorption using wells procedure, Source: (TerraTherm, 2016) ....................................................... 7

Figure 9: Soil washing process (FRTR, n.d.) ............................................................................................................................... 8

Figure 10: In-Situ Flushing Process (Reddy, 2008) ..................................................................................................................... 8

Figure 11: Remediation phasing ................................................................................................................................................ 9

Figure 12: Borehole locations sections .................................................................................................................................... 10

Figure 13: Ground model of site .............................................................................................................................................. 10

Figure 14: Borehole locations for further site investigation ................................................................................................... 11

Figure 15: Selected site layout ................................................................................................................................................ 14

Figure 16: 3D model of the site ............................................................................................................................................... 15

Figure 17: Ground sections with structures ............................................................................................................................ 15

Figure 18: Headquarters building ............................................................................................................................................ 16

Figure 19: Grid layout views .................................................................................................................................................... 17

Figure 20: Plan view of Ground Floor ...................................................................................................................................... 17

Figure 21: Construction phasing of the HQ ............................................................................................................................. 18

Figure 22: Longitudinal section axial force diagram ................................................................................................................ 18

Figure 23: HQ foundations ...................................................................................................................................................... 19

Figure 24: Pile alignment ......................................................................................................................................................... 19

Figure 25: Plan view of headquarters foundations ................................................................................................................. 20

Figure 26: Ground bearing slab concept drawing ................................................................................................................... 20

Figure 27: Terminus building ................................................................................................................................................... 21

Figure 28: Terminus steel frame .............................................................................................................................................. 21

Figure 29: Terminus axial forces .............................................................................................................................................. 21

Figure 30: Construction phasing of terminus .......................................................................................................................... 22

Figure 31: Terminus Pile Cap Design ....................................................................................................................................... 23

Figure 32: Terminus Pile Cap 3D Model .................................................................................................................................. 23

Figure 33: Plan view of terminus foundations......................................................................................................................... 23

Figure 34: Bridge superstructure ............................................................................................................................................. 24

Figure 35: GSA Bridge model ................................................................................................................................................... 24

Figure 36: Moments on the bridge modelled in GSA .............................................................................................................. 24

Figure 37: Construction phasing of the bridge ........................................................................................................................ 25

Figure 38: Side and plan view of foundations ......................................................................................................................... 26

Figure 39: New tramlines ........................................................................................................................................................ 27

Figure 40: Network Rail Marlborough Road Strengthening, Source: (Millington, 2015) ........................................................ 27

Figure 41: Stone column installation, Source: (Roger Bullivant Limited, 2016) ...................................................................... 27

Figure 42: Drainage masterplan .............................................................................................................................................. 28

Figure 43: Site section with stormwater tank and balancing pond levels shown ................................................................... 28

Figure 44: Swale & Filter Strip ................................................................................................................................................. 29

Figure 45: Storm tank catchment ............................................................................................................................................ 30

Figure 46: Storm tank inflow vs outflow graph ....................................................................................................................... 30

Figure 47: Balancing pond dimensions .................................................................................................................................... 31

Figure 48: Balancing pond runoff graph .................................................................................................................................. 31

Figure 49: Site runoff before and after SuDS .......................................................................................................................... 32

Figure 50: Phase 1,2,3 of construction .................................................................................................................................... 35

Figure 51: Phase 4,5,6 of construction .................................................................................................................................... 36

Figure 52: Phase 7,8,9 of construction .................................................................................................................................... 37

Figure 53: Gantt chart ............................................................................................................................................................. 38

Figure 54: Gantt chart (continued) .......................................................................................................................................... 39

Figure 55: Cost VS Time graph ................................................................................................................................................. 41

Figure 56: Phase daily average cost analysis chart .................................................................................................................. 41

1

0. Executive Summary The following report outlines the detailed proposal for the redevelopment of Neepsend Gas Works, located at Neepsend

Lane, Sheffield by Techni Consultants. Neepsend was used as Gas Works from the 1880s until 1967 (“Neepsend Lane

Gasworks,” n.d.). In the early 1980’s the site was demolished and finally abandoned in around 1986 – since, it has been used

as an open storage area. The proposed development aims to rejuvenate the area, following previous investment along the

River Don in areas like Kelham Island.

With the site backing onto an existing (and functioning) railway, opening up the River Don with a public walkway, including

an extension of the Sheffield Supertram system terminating at Neepsend and containing extensive car parking facilities, it

is anticipated that Neepsend will become a thriving transport Hub.

With facilities including a new company headquarters, cinema complex, retail centre, large concourse and large amounts of

green space, the site will become a new centre for commerce and recreation alike.

Within this report is a summary of the detailed engineering design, which can be found in greater depth within the attached

appendices.

1. Introduction Techni Consultants has produced the following report outlining the detailed design for the redevelopment of Neepsend

Lane Gasworks site. By considering factors such as the site history, contamination, geotechnical/geographical location and

key site features, an in depth analysis has been undertaken to outline the challenges and potential opportunities the site

presents.

Neepsend is a heavily contaminated site. This is discussed at length, before remediation methods are proposed.

In terms of the site’s development, a retail and leisure building will be constructed, as well as a headquarters building. The

headquarters is a multi-storey building, with large cinema screens at its base and an atrium running down the top four

floors.

For the access to the site, new tramlines will be installed, crossing a bridge over the River Don and terminating at the

development’s concourse. Footpaths run across the bridge, before continuing along the river and into the site. A footbridge

connecting the buildings to the adjacent railway station is also recommended, but it is not within this scope of this document

to fully design it. An outdoor car park with 500 spaces has also been designed into the site layout.

The major gas pipe and its burial have been outlined in detail. The gas pipe will be re-routed to run under the bridge, below

the footpath. This removes the interface between the tram network and the gas pipe – a potential hazard in the long term

life of the site.

Other factors such as cost, programme, risk assessment and construction plan are also included within this report to allow

the reader to gain a full appreciation for the proposed project and its scale.

2

2. Site Considerations

2.1. Existing Gas Pipe The major gas pipeline, assumed to be still active, is the most obvious potentially problematic site feature from a site

walkover. It has been found to be a 36 inch, medium pressure gas main. (“Neepsend Lane Gasworks,” n.d.) Partially for

aesthetic reasons, but predominantly as a safety decision, it has been decided to bury the pipe, keeping the supply active

throughout. The process of how this will be done safely, following best practice, is outlined in detail in the construction plan.

After consultation with a gas engineering expert, it has been decided that the new pipeline will be straight wherever

possible, and made from 450mm medium density polyethylene (mdpe) rated to a 2 bar maximum operating pressure. This

will be buried at a depth of 1.0m.

By extending the bridge (outlined in Appendix F) beyond the extent of the river, the gas pipe has been designed to never

run directly underneath the tram line. In terms of phasing this means that the tram works will not be encroaching on the

gas pipe. It also mitigates the risk of the tram route damaging the gas pipe during operation – by either a major incident

making contact with the pipe, or through galvanization of the pipe due to the electric currents running along the tram tracks.

The gas pipe’s route, both old and new, can be found in the phasing section later in this report.

2.2. Retaining wall

Figure 1: Retaining wall section

A retaining wall is present on the North boundary of the site, supported partially by the mound, some of which has already

been excavated. The mound is to be used for levelling on the site. For the safety of the staff working on site during

construction and public using the site once active, the wall’s structural integrity must be considered - especially since the

buildings to be constructed are adjacent to the retaining wall.

Following a risk assessment, it has been decided that the mound will be removed from west to east (following the previous

removal on site, visible from a site walkover). As the wall is removed, an engineer with suitable experience and qualifications

will be on site to supervise the works and advise on any actions required. Soil samples will also be taken from the ground

above the wall to find the properties of the soil being held back.

Should the wall need strengthening, there are two courses of action – to strengthen the existing structure or demolish and

reconstruct the wall. Due to cost and practicality issues, the reconstruction of the wall has been excluded. Therefore, if the

wall requires action during excavation, it will be strengthened.

Two methods were explored in detail: soil anchors and counterforts. Dependent on the exact condition of the wall, one of

these methods is likely to be used. Considering the long design life of the development, it is highly likely that counterforts

will be installed to protect against the degradation of the wall in the longer term.

2.3. Live Services Undertaking heavy building works on this site requires the location of buried services to be known. Following research in

the concept design stage, it was found that this information costs upwards of £300 from ‘FIND’ – this information would be

required early on in the detailed construction planning to allow the full risk assessment to be carried out. Hence, it has not

been possible to obtain this data. Additional detection of services, given the age of the site, will also be undertaken in the

further site investigation as part of Phase 1.

3

2.4. Existing Transport Links The existing transport links

around the site can be seen in

Figure 2, formed as part of the

concept design stage. This

network is particularly relevant

to the current proposal as the

site layout has been designed

with transport in mind –

incorporating all transport

routes whilst not forming any

crossings within these. By

understanding the existing

routes, the final design was

able to incorporate all public

routes to the site in a safe and

organised way.

2.5. Mining Coal mines nearby or under the site could create a major hazard to the structure. Looking at the historic mining areas in

Sheffield, as seen in Figure 3, Neepsend is located near High Risk Areas for development. Furthermore, towards the north

of the site, a mine entry is located. Hence, as a risk mitigation method, the coal seam expected beneath the site (see Ground

Report, Appendix A) is to be grouted – allowing for the risk attached to building foundations to drastically decrease. Find

details in section Appendix C.

Figure 2: Existing Transportation routes

Figure 3: Mining details in Sheffield, Source: (Coal Authority, 2015)

4

2.6. Enclosure Wall The stone enclosure wall which is currently in place will be removed for the vast majority of the site. It will remain however

along the north west of the site, where it will bound the green space. This will provide a barrier between the current

industrial area surrounding the site, and the pleasant area being created on site. This has a safety feature of forming a

barrier between the road and the park space (a positive benefit for when being used, for example, by young children). It

also makes use of an original part of the gas works, maintaining some of the site’s heritage. Obviously, this stretch of wall

will undergo some remediation to restore it to its original condition (as well as to remove any potential contaminants).

2.7. Flood Risk Being in such close proximity to the River Don, flood risk is obviously a key issue for Neepsend as a site. The figure below

(Environment Agency, n.d.) shows the flood risk on site. The light blue area, which encroaches on a large portion of the site,

is the flooding from a 0.1% annual probability storm (i.e. on average, a storm event that occurs 1 in 1000 years on average).

The darker blue area represents the probability of a 1 in 100 year storm, or a 1% annual probability. Fortunately, this does

not affect much of Neepsend.

Figure 4: Flood plan, Source: (Environment Agency, n.d.)

By interpolating these two areas, it can be assumed that for a 100 year return period storm, or rarer (such a 0.5% annual

probability) the site would be somewhat affected. As such, since the south of the site is most prone to flooding, the main

structures have been constructed towards the north of the site, keeping SuDS and car parking in the higher risk areas.

SuDS and other hard civil engineering drainage solutions have been heavily implemented in the proposed solution to

maintain the runoff into the river equal to that of a greenfield site in its place. The detail of how this is achieved can be

found in section 9. This not only provides many features increasing the site’s overall amenity, but also goes some way to

address floodplain squeezing – something which was highlighted as an issue on the River Don in the Environmental Agency’s

report on the 2007 storms. (Environment Agency, 2007)

5

3. Contamination Within this section, the analysis of the contamination on site will be presented, followed by a detailed and justified

remediation strategy. The full contamination report can be found in Appendix B.

3.1. Source-Pathway-Receptor Analysis In order to be able to propose suitable remediation methods, source-pathway-receptor analysis has been used. This analysis

indicates which contaminants pose a risk to a receptor, most notably human health. If any of the three stages are interrupted

or removed, the contaminant cannot reach the receptor.

Source: any source of contaminants that pose a risk on any receptor

Pathway: the route any contaminant can follow to reach a receptor

Receptor: any living organisms, i.e. humans, river Don, flora and fauna etc.

Using this method, the following table is constructed.

Source Contaminants Pathway Receptor

Retort House TPH, Nickel Groundwater Vapour

Humans River Don

Condenser Heavy metals, Water Soluble Sulphates, pH

Groundwater Vapour

Humans River Don

Tar tanks Heavy metals, Water Soluble Sulphates, pH

Groundwater Vapour

Humans River Don

Purifier pH, PAH, Water Soluble Sulphates, Heavy Metals

Groundwater Vapour

Humans River Don

Gasholders pH, PAH, Heavy Metals Groundwater Vapour

Humans River Don

3.2. Conceptual Site Model Using the table above and the site history, the conceptual site model is formed as shown below. The model is simplified

with the River Don being the major receptor for pollution. However, naturally there are also other pathways.

Figure 5: Site conceptual model

6

3.3. Identifying Contamination

3.3.1. Identification A substance is classified as a contaminant when it exceeds the allowable value given from the soil guideline values. With

the data of the boreholes and trial pits, the main contaminants were identified and categorised as follows:

PH: ‘power of hydrogen’. The PH scale is used to measure the hydrogen ion concentration ranging from 2 to 13,

where 7 is the neutral state (General Chemistry, 2010). A solution with PH above 7 is considered ‘alkaline’ or ‘basic’,

while a PH below 7 is categorized as ‘acidic’.

PAH: Polycyclic aromatic hydrocarbons. PAH are a diverse class of organic compounds which are highly flammable

and have no color or odour (Toxicology Department, 2008).

BTEX: Benzene, Toluene, Ethylbenzene and Xylene (S. Mitra, P. Roy, 2011). It is one of the most common

contaminant found in food and water and must be treated when found near people.

Aromatic and Aliphatic Compounds

Heavy Metals

3.3.2. Soil Guideline Values The Soil Guideline Values are utilised in order to gain data where a substance does not pose a risk to any receptor. Any

contaminant exceeding these values is classified as ‘contamination’ and must be remediated. For further details and the

table of the soil guideline values regarding the substances identified on site, refer to appendix B.

3.3.3. Identifying Contaminated Areas From the concentration of the contaminants in each borehole and trial pit, and making use of the soil guideline values, maps

indicating contaminated areas are constructed. Examples are shown below - further maps can be found in appendix B.

Based on the location of contaminants on the site, a comprehensive but appropriate and cost-effective remediation strategy

was put in place.

Figure 6: Aliphatic & Aromatic Compounds contamination areas Figure 7: Heavy metals contamination areas

7

3.4. Remediation Strategy

3.4.1. PH and SVOC Remediation

Observations Aliphatic and aromatic compounds, BTEX and PHA can be categorized as SVOC, i.e. Semi-Volatile Organic Compounds. They

will be treated with the same remediation technique, alongside PH.

Remediation method The chosen remediation method is in situ thermal desorption using wells. The remediation technique was selected after

analysing the advantages and disadvantages of the methods available for the contaminants - a table showing this process

can be found in appendix B. Thermal wells are preferred to a thermal blanket because of the alluvium layer present on site

- using wells, it can be ensured that the contaminants will be treated in the vertical direction rather than the horizontal,

which will provide more effective results. Moreover, the in-situ method provides a number of advantages when compared

with the ex-situ technique. Ex-situ remediation requires excavation of the contaminated soil which adds to the cost and in

the case of clayey or silty soil it is not very effective.

Procedure Thermal wells will be installed throughout the site and

will be heated. The contaminants will be then vaporized

and removed from the soil through the extraction well.

Using a series of mechanisms, the treated vapour will

be released in the atmosphere as it no longer poses a

risk and the treated water will be discharged in the

river.

Maintenance & Monitoring Monitoring the procedure includes the recording of the

remediation rate of the site. In terms of maintenance,

the replacement of the heating elements may be

needed as well as the refuelling of the thermal oxidizer.

Health & Safety Utilising this technique implies high temperatures and the use of electrical power. The staff to be controlling the remediation

should be well equipped and educated. In addition, to avoid any injuries, the site to be remediated should be fenced. Masks

should be provided for all personnel near the extraction wells as toxic vaporized substances will be released.

3.4.2. Heavy Metals

Remediation method Once again the pros and cons of the methods are analysed (see table in appendix B) and the conclusion was that the most

suitable method to be used for the treatment of heavy metals is stabilisation. The chosen technique is cost effective and

can improve the soil’s strength characteristics. Stabilisation actually has two phases: stabilisation and solidification. In the

first phase, immobilizing agents are inserted in the contaminated soil so that the leachability and bioavailability of any toxic

substance is reduced (Soilutions, 2016). Following the stabilisation phase, solidification includes ‘locking’ the hazardous

substance where it cannot reach any receptor. As seen from the source-pathway-receptor analysis section, if one of the

three sections is blocked or does not exist, the substance does not pose a risk to any receptor. The detailed methodology

of the remediation process can be found in appendix B.

Maintenance & Monitoring Monitoring is essential in the long term to verify that the contaminants are permanently removed or destroyed. Maintaining

the process will require the replacement of the protective media used after remediation.

Figure 8: In-situ thermal desorption using wells procedure, Source: (TerraTherm, 2016)

8

Health & Safety Great attention should be given in the health and safety of this method. Using lime as an immobilizing agent could be

dangerous as lime reacts with the water which releases heat, causing burns. PPE including respiratory masks, protective

clothing and eye googles are essential. Moreover, in the case of strong winds, the remediation should not take place as the

lime could be transferred to nearby sites.

3.4.3. Water Soluble Chlorides and Sulphates

Remediation method The remediation method to treat water

soluble chlorides and sulphates is chosen to

be soil washing. Contaminated soil can be

transferred to be treated using water or water

mixed with chemicals. Throughout the

process, the water can be recycled and

disposed at the end of the remediation. For

more methods that could be used, refer to

appendix B.

Maintenance & Monitoring The treatment system’s optimisation must be

verified by the contractor. Some of the key

parameters to be monitored include

washwater PH and soil residence time in the

treatment units (ITRC, 1997). For the

verification of the effectiveness of the

treatment, a combination of soil verification sampling and mass balance calculations are needed.

No maintenance is required.

Health & Safety The remediation is performed ex-situ, hence the soil will be transferred to the treatment plant by trucks. Staff needs to be

familiar with the routes used by the trucks to avoid any injury.

3.4.4. Groundwater Remediation

The appropriate treatment for remediating

groundwater is found to be in-situ flushing.

With this method, flushing solutions are

injected in the ground via wells and by passing

through the groundwater, the contaminants are

either desorbed or flushed away. Extraction

wells located further down the site are used to

extract the toxic substances and the treated

water can be pumped again in the ground.

Figure 9: Soil washing process (FRTR, n.d.)

Figure 10: In-Situ Flushing Process (Reddy, 2008)

9

3.5. Remediation Time Lapse Process The remediation phasing is shown in a series of maps below. Following the completion of detailed design and site

investigation, contamination is the first major phase (see phasing detail in section 11. Remediation will be finished as soon

as possible within the programme, since it is part of the critical path. Looking at case studies, the time needed for the

remediation of the site is approximately 2.1 years. For the relevant GANTT chart, refer to appendix B or see the programme

later in this report.

Figure 11: Remediation phasing

Thermal Desorption

Stabilisation

Soil Washing

Groundwater

Remediation

10

4. Ground Model This section of the report investigates, assesses and compiles the contractor’s findings relating to the specific ground

conditions at the site and discusses the associated implications.

4.1. Boreholes

4.1.1. Borehole Data Summary Borehole logs have been provided for boreholes previously conducted across the site. These have been analysed and used

to create a ground model of the site and best understand the ground conditions. It is this ground model that has guided

foundation design over the course of the project.

Overall, the borehole data supports what would be expected for the site by showing a

fairly thick layer of made ground followed by a layer of alluvial deposits followed layers

of rock (PLCM) which are generally increasing in strength with depth. Some of the

deeper boreholes have picked up a thin coal layer, which was expected considering the

coal seam present on the geological map.

4.1.2. Ground Section Locations The location of sections created for design purposes can be seen in the figure to the

right. In total four sections were produced, shown by the two red lines and two dashed

green lines on the figure. These detailed drawings of these ground model sections are

located at the end of Appendix A, attached to this document. Some trial pit data was

also used to help produce the ground model sections and generally increase the

reliability of the model.

Using both interpolation along with the inferior borehole logs of boreholes

314 and then 311, the two sections shown by the green dashed lines could

be produced. These sections were specifically desired as they are located

directly below the area of development in the planned site layout, found in

section 5 of this report. One of these sections is shown below, and its

development can be found later in the report.

4.2. Results For the purposes of this project the final results, shown below, shall be used as the design values of the different soil strata

for the design of any foundations and substructures. However, as has been stated, the project geotechnical engineer does

not believe that the Information provided within the borehole logs, trial pit logs and SI data document are sufficient enough

to provide the required level of understanding of the ground conditions to design safely. Therefore, advised supplementary

site investigation follows the results.

Figure 13: Ground model of site

MadeGround - 30.00 - - 20.00 0.18 - 6.00 - - - - - -Alluvium - 33.80 4.00 3.00 26.50 1.40 0.70 0.71 5.80 65.50 35.00 30.50 24.00 1.90

WeakPLCM 25.45 - - - - - - - - - - - - -

StrongPLCM 43.50 - - - - - - - - - - - - -

Natural

MoistureContent(%)

BulkDensity

(Mg/m3)CU(Kpa) ϕU(°) C'(Kpa) ϕ'(°)

mv

(m2/MN)

ms

(m2/MN)cv(m

2/yr) LL(%)LayerPlasticity

IndexPL(%)UCS(Mpa) E0(Mpa)

Figure 12: Borehole locations sections

11

4.3. Further Site Investigation Borehole and trial pit logs along with the SI data provided by Ace Explorations Company Ltd have allowed a better

understanding of the ground conditions of the Neepsend site. However, as has been expressed in Appendix A, the project

geotechnical engineer does not believe the information available to be of a sufficient quantity or quality to provide the level

of understanding required to design with a sufficient level of safety. In this section of the report the project geotechnical

engineer has outlined the preliminary details for recommended further site investigation and states that this would be

required to provide enough confidence for detailed designs to be finalised, with regards to foundations. This has been

included in the phasing and programme.

4.3.1. Boreholes and Trial Pits The figure on the right shows the recommended locations of boreholes and

trial pits to be conducted as part of the further site investigation. Particular

focus has been given to designing the further site investigation around the

proposed site layout, with the aim of significantly increasing knowledge of the

ground conditions directly below the proposed building locations. “Whenever

possible boreholes should be sunk close to the proposed foundations”.

(Tomlinson, 2001)

The planned further site investigation includes fifty-two 25m deep boreholes,

four 50m deep boreholes and 9 additional trial pits across the site. The layout

of the boreholes abides by minimum spacing requirements shown in table 13,

this will ensure an overlap between layers will be identified between

boreholes allowing the dips of strata and other conditions to be predicted with

increased accuracy.

4.3.2. Testing

4.3.2.1. Lab Tests Laboratory tests shall be conducted on the samples obtained from the

boreholes and trial pits across the site and at varying depths. This will allow

the determination of the properties of the different strata. A detailed

description of the processes can be found in Appendix A, which consists of the

following:

a) Visual Examination b) Natural Moisture Content

c) Liquid and Plastic limits d) Particle Size Distribution

e) Unconfined Compression f) Triaxial Compression

g) Shear Box h) Vane

i) Swelling and Suction j) Permeability

4.3.2.2. In-Situ Testing A combination of SPT, CPT and CBR testing shall be conducted across the site and using the relevant correlations the

properties of the strata can be found. The testing method that produces the most conservative results will be used to

determine final values, along with the laboratory tests. Justification can be found for this in Appendix A.

Figure 14: Borehole locations for further site investigation

14

5. Selected Site Layout

5.1. Site Layout Selection A detailed decision matrix was undertaken for the selection of the final site layout, following numerous proposals in the

concept design stage. The process undertaken was to use various important parameters, agreed and weighted before the

exercise was started, to judge and compare the potential designs. The chosen parameters were:

Meeting of the brief

Buildability

Transport Links

Use of Site

Complexity

Safety

Sustainability

Anticipated Cost

The chosen site layout was then optimised further following feedback from the client in the conceptual design phase. The

result is outlined below. To see the full selection process, please see Appendix H.

5.1.1. Selected Site Layout – Plan Overview

The site has been designed such that the transport

links running through it do not cross at any point,

improving safety and reducing associated logistical

problems. This was a key consideration when

optimising the site layout.

Neepsend Lane has been diverted – this both opens

up the river to the green space at the bottom of the

site, and also provides emergency access to the main

development.

Following several potential layouts, car parking has

been designed to use the space in the most effective

(but practical) way with two entrances / exits.

Consideration has been given to the building

orientation, with glass cladding on the south facing

areas.

The hatched areas (marked as filter strips) are the

most suitable areas for potential future development,

being on better ground conditions and further from

the flood plain.

Figure 15: Selected site layout

15

5.1.2. Site 3D Model

Figure 16: 3D model of the site

A site model was created in three dimensions to allow the design team to fully visualise the site. This was very useful in

allowing the team to see any potential problematic features before detailed design began.

5.1.3. Selected Site Layout – Sections Following on from the ground model, determined in section 4.1.2, the integrated site sections can be seen below. These

sections show the full extent of the integrated approach Techni has taken. The ground model, structures, levels, foundations

and drainage features are all evident – the project team took the approach early on of combining drawings to see any

potential crossover issues.

Figure 17: Ground sections with structures

16

6. Headquarters building

6.1. Superstructure

6.1.1. Structure Overview The brief required a Headquarters building to be

present on site, with low or zero embodied

carbon. To meet these requirements, the HQ

building is designed as a multi-storey building,

using local materials where possible in order to

reduce the embodied carbon. A double glazed

glass façade has been included in the design,

shown in the figure, to ensure that need for

heating and lighting will be minimised. The

inclusion of an atrium running down the

headquarters allows natural ventilation to cool

down the building, as well as letting light

permeate further into the structure.

The location of the HQ, makes it easily accessible

from all the transport links, such as the terminus

building, the bridge leading to the railway and the

car parking.

Underneath the HQ is a cinema with two 250 seat screens, and two 235 seat screens – this brings with it noise and space

requirements, outlined in Appendix D. Above the gym, which backs onto the cinemas, is a green roof, accessible from the

offices. There is 7287m2 of usable office and administrative space, in-keeping with the brief provided by the client.

6.1.2. Atrium A 30mx7m atrium runs down the centre of the headquarters building to the 2nd floor – an alteration from the concept design

stage. This brings with it several benefits. Light is allowed to permeate further into the building, meaning the HQ does not

simply rely on it’s outward facing façade. It also provides ventilation and heating benefits, allowing the building to be treated

as a whole system, rather than on a floor-by-floor basis.

6.1.3. Double Glazed Glass Façade Benefits of the glass façade include the natural lighting predominantly – reducing the need for artificial light and providing

a more pleasant work space for the staff in the building. It also allows solar gain, reducing heating costs. Combined with the

efficient ventilation system which the atrium allows, Techni anticipates a large reduction in energy costs/usage.

Figure 18: Headquarters building

17

6.1.4. Structural Detailing The layout of the headquarters building can be seen below. The column spacing is made up of a 7mx15m grid. Cross bracing

is shown in both the front and side sections – this provides lateral stability. For full detailing, see Appendix D.

6.1.5. Floorplan The floorplan shown gives an

example of the consideration given

to the building internal layout –

especially when open to the

general public.

Full floorplans for the building,

including the upper floors, can be

found in the relevant

superstructure appendix.

Figure 19: Grid layout views

Figure 20: Plan view of Ground Floor

18

6.2. Construction Sequencing Below, the construction methodology for the headquarters multi-storey building can be seen. The programme, which can

be found later in this document, outlines the time scales for the various construction phases. Follow on activities, shown as

overlapping tasks in the GANTT chart, help to save considerable construction cost. Prefabrication of bison hollow core slabs

saves time, energy and increases on-site safety. The steel is designed to come with shear studs and endplates pre-welded

before arrival to site, saving time and increasing weld quality.

Figure 21: Construction phasing of the HQ

6.3. Design Process Below is outlined the design process followed to design the headquarters building.

An example of the GSA modelling is shown alongside the process list – full modelling results can be found in Appendix D.

Evaluation of conceptual stage design

Improvements made to the design

Research into materials and design

methodologies

Building grid and layout / floorplans

Wind loading on the structure

GSA modelling

Verification of model using braced

member calculations

Designing braced members

Designing the columns and composite beams

Design of critical connections

Construction phasing

Costing Figure 22: Longitudinal section axial force diagram

19

6.4. Foundations After both qualitative analysis and preliminary quantitative analysis of the

ground model and SI Data, it has been decided by Techni’s geotechnical

engineer that a piled foundation solution is necessary for the HQ to transfer

the relatively large column loads to the stronger rock layers at depth. A

ground-bearing slab with sub-base has been deemed suitable for taking the

ground floor loads. It has been decided to found the piles on the strong PLCM

layer. As can be seen from the ground model sections in Appendix A, a layer

of thin coal runs close to the upper surface of this layer. As a result, it has been

specified that the piles will have to penetrate the coal layer by 0.5m to secure

a solid embedment into the strong PLCM below. Founding in the strong PLCM

above the coal layer would likely be catastrophic as the coal layer is incredibly

weak and the ‘zone of influence’ of the load from the piles would likely

penetrate into the layer, meaning that the layer would be effectively

supporting the load from the piles and would undoubtedly fail as a result. The

construction specification is therefore not a specific length for each pile but

rather that each pile must be embedded into a minimum of 0.5m of strong

PLCM, below the coal layer. After analysing the ground model, this suggests

that the piles will vary in length from 16.5m and 18.5m. Pile diameter was

optimised and selected via calculation, see Appendix C. The geotechnical

engineer decided that having a constant diameter for all piles would reduce

costs and improve construction efficiency, as the boring tool heads would not

need to be changed to bore different holes. Piles shall be installed using a

mechanical auger and casing, see Appendix C for more details.

Length: 16.5m – 18.5m

Diameter: 0.45m

Figure 24: Pile alignment

As of this point, pile caps have only been designed to a preliminary stage, however, the geotechnical engineer believes that

the pile caps will pass stringent calculation tests since they have been designed following guidance from both (Tomlinson,

2001) and (IStructE, 2013, pp. 32-33)

Figure 23: HQ foundations

20

Figure 25: Plan view of headquarters foundations

As the diameter of the piles for the HQ is constant, the way to change the design for different loading conditions was to

alter the pile group sizes. As can be seen from figure 23, the internal columns use pile groups of 4 piles, whilst the edge and

corner columns of the HQ, which transmit lower loads to the foundations than the internal columns, are founded using pile

groups of 3 piles. Corner columns had the lowest loading of all columns and pile groups of 2 piles would have been sufficient

to withstand the axial loading, however, the geotechnical engineer decided to maintain the use of a minimum of 3 piles per

pile cap to ensure lateral stability of the group, otherwise some other form of specialist lateral restraint would have been

required. The full detailed drawings of the pile layout and pile caps can be found in appendix C.

Figure 26: Ground bearing slab concept drawing

The detailed design of the ground-bearing slab is beyond the scope of this report, however, the geotechnical engineer has

used the software ‘Tedds’ to conduct a preliminary design calculation and this showed that a 150mm thick ground-bearing

slab would be sufficient for supporting the ground floor loading of the HQ. The calculations are shown in section 7.3 of

Appendix C.

21

7. Terminus

7.1. Structure Overview The terminus must be capable of having four tram

lines for immediate use and room for additional four

in the future. Another criterion was the absence of

columns within the concourse. Looking at the

requirements, Techni chose to keep the following

design from the concept design stage, making some

alterations where possible. Regarding sustainability,

glulam arches are preferred than steel arches for the

roof. The following section explains in detail the

decisions made for the design and the phasing of the

construction.

7.1.1. Roof Structure Out of all of the structures put submitted in the

concept design phase, a solution that used tied glulam arches with struts running between the arch and the tie member to

form a truss was chosen to be taken forward into detailed design. The solution comprised of four of these arches arrayed

at 15m centres which span 50m across a floor area of 2250m2. Half of this floor area is taken up by the tram lines and

platforms and the other half is used as a concourse area.

The design was changed slightly after structural analysis had been carried out on GSA and it was realised that the truss

elements weren’t doing as much as hoped to reduce the maximum bending moments in the arch member. It was found to

be more economical to reduce the overall weight of the structure by getting rid of the struts in the middle of the truss and

designing the arch member to resist a slightly higher bending moment. So now it consists of a solid glulam arch section tied

with a steel rectangular hollow section.

7.1.2. Steel Frame The roof sits on top of a steel frame which has two main

functions:

To suspend the roof at a height above ground level.

To support the cladding around the terminus perimeter.

Because the roof arches only span in one direction, and the

spans are much smaller in the longitudinal direction, the

columns and beams on the sides of the tram structure are much

larger than those used for the front and back.

The columns and beams are all UC or UB sections

respectively.

xy

z

ANALYSIS LAYER

Scale: 1:378.0

Highlighted:

Coincident Nodes

Coincident Elements

xy

z

ANALYSIS LAYER

Scale: 1:378.0

Highlighted:

Coincident Nodes

Coincident Elements

Axial Force, Fx: 2000. kN/pic.cm

Case: A5 : Load case 2

Figure 27: Terminus building

Figure 28: Terminus steel frame

Figure 29: Terminus axial forces

22

7.1.3. Lateral Stability

Below Roof Level

Below roof level, lateral stability for the structure is provided by braced bays, which are 15x5m in the longitudinal direction

and 10x5m in the lateral direction. The bays are cross-braced with tension-only members. Lateral loads are carried from the

rest of the structure to the braced bays by tie beams at 5m and 10m height, who’s only other function is to support the

cladding on the vertical sides of the structure. Where columns are only laterally restrained in one direction, a strut has been

added between the column at 5m height and the ground 5m away from the column. This ensures that all members are

restrained laterally in both directions.

At Roof Level

At roof level, lateral stability in the lateral direction is provided by the arched trusses themselves. In the absence of bracing,

the critical mode of failure for lateral stability in the longitudinal direction is for the roof trusses to fall over to the side.

Therefore, bracing has been added from the top of two roof trusses to the bottom of the one between them to prevent this

from happening. The reason two bracing members have been used rather than one is so that the longitudinal horizontal

forces will cancel out at the bottom of the middle truss, meaning that a bending moment won’t be induced in the tie

member. The roof purlins have been designed so that they can resist the additional axial stresses required to carry the

longitudinal horizontal loads between the trusses.

7.2. Construction Sequencing The sequencing of the terminus construction can be seen below. By constructing the tied arches off site in tandem with

erecting the steel frame, construction time can be massively reduced – as well as labour hours on site. The construction

time is estimated to be 140 days and the cost estimation is £1.83 million.

Figure 30: Construction phasing of terminus

23

7.3. Foundations After both qualitative analysis and preliminary quantitative analysis of the ground

model and SI Data it has been decided by the project geotechnical engineer that

a piled foundation solution is optimal for the terminus building, to transfer the

column loads to the stronger rock layers at depth. A ground-bearing slab with sub-

base will be suitable for taking the ground floor loads, details of which can be

found in Appendix C. The tram track foundations and terminus foundations will

be independent, see section 8.3.2 of this report for tram track foundation

information. Having determined that a piled solution is necessary, the project

geotechnical engineer had to consider the different types of piles available and

determine which type is most appropriate for use at the Neepsend site. The first

choice the geotechnical engineer considered was whether to use some form of

displacement pile, such as driven or driven and cast-in place, or some form of

replacement pile. The process of assessing the options is outlined in section 2.1.1 of

Appendix C and the same conclusions apply to the terminus as for the HQ.

Replacement (bored and cast-in place) piles shall be used for the terminus. Piles

shall be installed using a mechanical auger and casing, see Appendix C for details.

Figure 7 shows the plan view of columns and piles for the terminus building. As can

be seen from the figure, all columns are founded using pile groups of 3 piles. This is

a result of the optimisation process along with the fact that the geotechnical

engineer decided to have a minimum of 3 piles per pile group to ensure lateral

stability.

Length: 10m

Diameter: 0.3m

Figure 31: Terminus Pile Cap Design

Figure 32: Terminus Pile Cap 3D Model

Figure 33: Plan view of terminus foundations

24

8. Bridge and Supertram

8.1. Superstructure

8.1.1. Structure Overview Out of all of the concepts generated in part

1, a tied arch suspension bridge was chosen

as the structural form to be taken to the

detailed design stage. This decision was

made using a decision matrix which put

particular emphasis on aesthetics,

buildability and cost. The dimensions of the

bridge were modified to suit site layout

which is different to the one it was originally

designed for, as were the foundations.

The main alteration to the design from the concept

stage is that the bridge is raised 3m above ground

level. The bridge is supported by abutments which

also act as retaining walls for the for part of the

mound removed from the top of the site. The mound

provides access to the raised bridge for both trams

and pedestrians. The reasons for having a raised

bridge are:

The tram line will no longer have to cross the gas pipe, meaning that maintenance on the pipe will be easier in the

future.

It allows for a pedestrian route into the site from the east which doesn’t have to cross the tram tracks

The deck consists of a main tram deck 7m wide which runs between the arches and two pedestrian decks 2.4m wide which

are cantilevered on the outside of the arches. There is a fence between the two decks so that pedestrians can’t wander in

front of the trams, and also a fence on the outer side of the pedestrian deck. The tram deck is made from a 300mm deep

reinforced concrete slab cast on a metal deck and the pedestrian decks are made formed by two 1200mm width hollowcore

planks side-by-side.

These decks span 5m between large beams which run in the transverse direction, and the beams are held by cables which

are attached to the arch member from above. The arch is held together at the bottom by a tie member. Both the arch and

the tie member are rectangular hollow sections (RHS).

There is a lateral stability system comprises of two

braced bays, which span between the arches in two

places. These have two roles in the structure:

Restrain the arch member from buckling about its minor axis, thereby reducing the effective buckling length and increasing the Euler buckling load.

Prevent wind loads from pushing the arches over.

The height of the lateral stability system is governed by a desire to keep it well out of the way of the electric cables used by

the tram. They clear the deck surface by 7m, which leaves a 2m clear height over the cable. This will vastly reduce the chance

x

yz

Scale: 1:198.4

Highlighted:

Coincident Nodes

Coincident Elements

xy

z

Scale: 1:158.7

Highlighted:

Coincident Nodes

Coincident Elements

Moment, Myy: 1.000E+6 Nm/pic.cm

Case: A5 : Half Loaded ULS

Figure 34: Bridge superstructure

Figure 35: GSA Bridge model

Figure 36: Moments on the bridge modelled in GSA

25

of a loose cable blowing in the wind and making contact with the steel member. Because of this height restriction, the

effective buckling length of the bottom parts of the arch is quite long, and caused buckling to be the critical mode of failure

for that part of the arch. However, because buckling at the bottom was critical, this meant that there was no requirement

for extra restraint at the top of the arch.

The whole structure is raised 3m above ground level and sits on abutments which act as retaining walls for the raised ground

used for access to the bridge.

8.2. Construction Sequence For a full description of the bridge’s construction sequence, see appendix F. A short summary is given below:

1. Piles installed

2. Retaining walls constructed

3. Embankment construction

4. Tied arches assembled with lateral stability system.

5. Tied arches lifted into place.

6. Transverse beams attached to arches with cables.

7. Hollowcore planks and steel decks attached between transverse beams.

8. RC slabs cast starting from the outside, working towards the centre.

Figure 37: Construction phasing of the bridge

26

8.3. Foundations After both qualitative analysis and preliminary quantitative analysis of the ground model and SI Data it has been decided

that a piled foundation solution is necessary for the bridge, to transfer the relatively large column loads to the stronger rock

layers at depth. The bridge embankment, shown in the figure below, will act as both a pile cap for the piles and retaining

wall to withstand the horizontal embankment loading. Having determined that a piled solution is necessary, the project

geotechnical engineer had to consider the different types of piles available and determine which type is most appropriate

for use for the bridge at the Neepsend site. The first choice the geotechnical engineer considered was whether to use some

form of displacement pile, such as driven or driven and cast-in place, or some form of replacement pile. The process of

assessing the options is outlined in section 2.1.1 of Appendix A and the same conclusions apply to the bridge as for the HQ

and Terminus building. Replacement (bored and cast-in place) piles shall be used for the Bridge.

For the same reason as specified for the HQ, it has been chosen that the piles will have to penetrate the coal layer by 0.5m

to secure a solid embedment into the strong PLCM below. The construction specification is therefore not a specific length

for each pile but rather that each pile must be embedded into a minimum of 0.5m of strong PLCM below the coal layer.

After analysing the ground model this suggests that the piles will be approximately 20m in length. Pile diameter was

optimised and selected via calculation, see Appendix C for an example pile calculation. The bridge piles shall be installed

using a mechanical auger and casing system.

Depth: 20m

Diameter: 0.6m

Figure 38: Side and plan view of foundations

27

8.4. Tram Route

8.4.1. Route The new tramline route, initially proposed in the concept design stage,

has not been altered. The tramlines pass along Infirmary Road, Bedford

Street and then go through the open storage area near river Don. Using

the bridge, the tram crosses the river Don and finally stops at the

terminus building on site. The only restriction to this tram route is the

fact that the open storage area located near river Don must be purchased

in order for the tramlines to pass through it.

8.4.2. Route Foundations Where foundations for the tram tracks are necessary, especially for the

bridge embankments, small scale piling (micro-piling) has been selected

as the most viable option.

A Network Rail project at Marlborough Road, Near

Gloucester, made effective use of micro-piling:

“Piling was proposed to reinforce the upper layers of

the embankment and reduce stresses within the

core. Piling between the sleepers will transfer the

load to deeper layers and reduce lateral and vertical

stresses within the trackbed and core.” (Millington,

2015) Although here micro-piling is being used for a

rail system being strengthened, the principles of

maintaining stability and reducing stresses is

consistent with the tram route.

Vibro stone columns are used underground in order to absorb vibration induced by vehicles, limiting the overall and

differential settlement (Roger Bullivant Limited, 2016). By using this technique, the load bearing capacity of the soil is

improved with capacities ranging from 50 kN/m2 to

150 kN/m2. In addition, the risk of liquefaction is

mitigated (Vibro Menard, 2016). In this project,

vibro stone columns will be located underneath the

tramlines, hence vibration caused by the trams will

not be affecting the soil in terms of settlement as

the vibration will be absorbed by the piles. For the

installation of the pile, the vibrating probe is forced

in the ground to the designed depth forming a void.

The probe is removed and the gap is filled with

stone which is compacted with the probe. A

granular inclusion with high stiffness, good

drainage propertied and high shear strength is

formed by repeated compaction (Roger Bullivant

Limited, 2016).

Figure 40: Network Rail Marlborough Road Strengthening, Source: (Millington, 2015)

Figure 41: Stone column installation, Source: (Roger Bullivant Limited, 2016)

Figure 39: New tramlines

28

9. Associated Drainage This section explains the proposed drainage solution, made as to attenuate the site runoff sufficiently. Outlined are the

main design solutions, a rationale for their selection and a justification using modelled results. Full drainage details can be

found in Appendix G.

9.1. Drainage Overview

9.1.1. Drainage Masterplan

The main SuDS features being implemented are swales, a storm tank, a balancing pond, filter strips and a green roof.

The swales can be seen running along the west of the site and to the south of the car park. The green roof is located on the

HQ. The storm tank is located next to the buildings, allowing for enough head to reach the pond running down the site.

Water flows from the filter strips, into the swales and finally into the pond. Water from the roofs run via pipes into the

storm tank and then to the pond through a smaller pipe which acts as an orifice from the storm tank. The levels can be seen

in the figure below, allowing gravity flow without the need for pumps.

The pipes under the car park have been designed as to allow future development to join the existing stormwater attenuation

system. Potential future pipe layouts are shown as red dotted lines on the diagram. The storm tank is oversized, taking this

into consideration.

Figure 42: Drainage masterplan

Figure 43: Site section with stormwater tank and balancing pond levels shown

29

9.2. SuDS Selection Rationale Although hard engineering techniques can successfully be used to attenuate and retain stormwater, the use of sustainable

methods is preferred – both in terms of planning permission and amenity.

“The use of SuDS for stormwater storage SuDS are aimed at addressing both treatment and hydraulic management of

stormwater runoff. It is stressed that the Floods and Water Management Act 2010 requires the use of SuDS. Although

storage can also be provided using underground storage systems, the Environment Agency very much prefer the use of

surface level, vegetative systems to be used for conveyance and temporary storage (swales, basins and ponds etc) if

possible.” (Kellagher, 2013)

9.3. Drainage Design

9.3.1. Filter Strips and Swales Filter strips are “uniformly graded and gently sloping strips of grass or other dense vegetation that are designed to treat

runoff”. (“SuDS Manual 2015,” n.d.) They have been selected for the site to both provide green space for the general

amenity of the site, but also to slow down the runoff from the site feeding into the swales.

“Swales are shallow, flat bottomed, vegetated open channels designed to convey, treat and often attenuate surface water

runoff.”(“SuDS Manual 2015,” n.d.) Essentially, the swales on site at Neepsend will be used to slowly convey water from the

bulk of the site to the balancing pond at the south of the site.

The swales are in place to attenuate the flow from the green space, tram tracks and the southern half of the car park. They

have been designed with a base width of 0.5m and a slope of 3:1. By allowing a maximum height of 0.25m, the capacity of

the swales is 85.84L/s velocity of 0.27m/s (below the allowable velocity of 0.3m/s). The flow speed was calculated using

Manning’s equation for open channel flow. 𝑈 = 𝑅

23𝑆0

12

𝑛 using an n value of 0.1 for the swales due to the system being

designed for a large storm event. (Shucksmith, 2016)

The two sections of green space have been designed to act as filter strips, attenuating the flow from these areas into the

swales before being conveyed. For these sections, the manning’s n selected was 0.35, since flow should run sub-soil. This

was in accordance with the case study in the SuDS manual (Appendix C). (“SuDS Manual 2015,” n.d.) The ground will be

landscaped to a slope of 1% and made up of topsoil, lightly compacted permeable subgrade and an impermeable

geomembrane layer. The topsoil will be a depth of 0.15m and the engineered soil 0.35m (as shown below in the section).

Figure 44: Swale & Filter Strip

30

9.3.2. Green Roof Green roofs are installed on the top of buildings for aesthetic, ecological and environmental reasons, as well as to retain

some of the runoff which would otherwise join the drainage network. A green roof has been provided on one of our buildings

to provide a pleasant outdoor area for workers in the HQ, as well as reducing the runoff from a significant percentage of

the site. It was decided to not put green roofs on all the buildings for practical reasons

(either the roofs not being flat, or not being accessible for use beyond water

retention). The decision was made that our green roof would be made up of several

plant types, increasing biodiversity.

The green roof retention was calculated by estimating the porosity of the soil and a

percentage coverage of the roof, as 0.3 and 70% respectively. By finding the volume

of porous soil, the capacity could be calculated as 48.3m3 of storage. By finding the

total rainfall falling on the area, the percentage of the rainfall which is conveyed as

runoff was found. For each of the synthetic design storms, the retention can be seen

in Appendix G in the form of pie charts.

9.3.3. Storm Tank A storm tank located under the car park at a shallow depth allows temporary storage

of surface water before controlled release (via an orifice outflow). The storm tank has

been designed as an underground concrete tank with the dimensions 20mx10mx1m.

The inflow is from the roofs of the main buildings, as well as the northern half of the

car park (see catchment diagram).

Figure 45: Storm tank catchment

Figure 46: Storm tank inflow vs outflow graph

31

9.3.4. Balancing Pond A large balancing pond at the south of the site provides the final attenuation measure before runoff flow is allowed off the

site. Flow from the swales, storm tank and surrounding green space make the pond quite large. Surrounded by green space,

located near the river and new walkway under the bridge, it is hoped that the area around the pond will become a major

factor in improving the site’s amenity.

The balancing pond has been designed to

take the inflow from the storm tank, swales

and surrounding green space. The outflow is

in the form of an orifice (0.17m diameter) at

a height of 0.5m. The equations used were

the same as in the storm tank, but with a

changing surface area.

The design of the balancing pond can be seen

to the right. The pond is lined with a

geotextile layer to remove the risk of

infiltration due to the contaminated soil

history. Its base dimensions are 10x20m and

the slopes are of a 3:1 ratio (for safety and

maintenance purposes.

Pond Runoff On the graph, the

inflows can be seen

from the previously

calculated SuDS

mechanisms as finer

lines on the plot. The

total inflow is shown

in red, and the

outflow from the

pond in blue.

Figure 48: Balancing pond runoff graph

Figure 47: Balancing pond dimensions

32

9.4. Final Runoff The final runoff was found by summing the runoff from the road and the outflow from the pond. Since the vast majority of

the site is attenuated using SuDS, the decision was made to allow the roads to drain immediately. As can be seen on the

outflow graph, this efficiently removes a large portion of the site’s rainfall whilst keeping total outflow below greenfield

runoff.

The SuDS methods have been designed to keep runoff below greenfield level whilst allowing the site to drain fast enough

that a supplementary follow-up storm would not flood the site.

Figure 49: Site runoff before and after SuDS

33

10. Embodied Carbon Content Sustainability is a key issue when designing a structure. The term ‘embodied carbon’ refers to the carbon emissions in the

mining, manufacturing and transporting materials to the site as well as the construction phase and the end of life emissions

(demolition). In this section, the overall embodied carbon ‘Cradle to Site’ for each structure designed for this project will be

outlined. For the transportation energy, the assumption that the materials will be collected from local factories is made –

this is something the design team is committed to delivering, to boost the local economy and reduce overall carbon

emissions.

Embodied Carbon for materials used:

Concrete (standardized mix): 79.4 kg CO2/tonne (Concrete Industry, 2012)

Steel:

Plate: 919 kg CO2/tonne (Galvanizers Association, 2016)

Sections: 762 kg CO2/tonne (Galvanizers Association, 2016)

Purlins & rails: 1100 kg CO2/tonne (Galvanizers Association, 2016)

Glulam: 700 kg CO2/tonne (Purnell, 2013)

Thermal Glass Cladding: 0.003 kg CO2/tonne

Embodied Carbon due to transportation:

Using a 32 tonne truck: 1.37 MJ/tonne per mile (Cannon Design, 2016)

Concrete: 2.6 miles away

Steel: 2.5 miles away

Glass: 2.6 miles away

Glulam: 10 miles away

10.1. Headquarters Embodied Carbon due to materials used

Material Quantity (tonnes) Embodied Carbon (tonnes CO2)

Concrete 4056.3 322

Steel 683.2 520

Glass 95.8 0.3 x 10-3(negligible)

TOTAL 3245.9 716 Table 1: Embodied carbon due to materials used for headquarters

Embodied Carbon due to transportation to site

Material No. of rides Embodied Carbon (MJ)

Concrete 254 872.7

Steel 44 150.7

Glass 6 21.4

TOTAL 204 1044.8 Table 2: Embodied carbon due to transportation of headquarters materials to the site

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10.2. Terminus Embodied Carbon due to materials used

Material Quantity (tonnes) Embodied Carbon (tonnes CO2)

Concrete 1164.3 92.4

Steel 125 95.3

Glulam 35 24.5

TOTAL 1324.3 212.2 Table 3: Embodied carbon due to materials used for terminus

Embodied Carbon due to transportation to site

Material No. of rides Embodied Carbon (MJ)

Concrete 74 263.6

Steel 8 27.4

Glulam 4 54.8

TOTAL 85 345.8 Table 4: Embodied carbon due to transportation of terminus materials to the site

10.3. Supertram Bridge Embodied Carbon due to materials used

Material Quantity (tonnes) Embodied Carbon (tonnes CO2)

Concrete 382 30.3

Steel 111 84.6

TOTAL 493 114.9 Table 5: Embodied carbon due to materials used for bridge

Embodied Carbon due to transportation to site

Material No. of rides Embodied Carbon (MJ)

Concrete 24 85.5

Steel 8 27.4

TOTAL 32 112.9 Table 6: Embodied carbon due to transportation of bridge materials to the site

35

11. Programme and Phasing

11.1. Phasing The programme has been split into 9 phases. These phases are outlined below. Each phase has been allocated a colour –

these colours are also used in the programme and costing to allow easy correlation and analysis of the phases.

Phase 1 - 270 days:

Phase one encapsulates the work required before major works can commence. The phases are broken down

Concept Design

Detailed Design + Tender Submission

Planning Permission

Road Closures

Supplementary Site Investigation

Phase 2 – 780 days:

Phase two sees the contamination remediation of the site, outlined in further detail in both section 3.4 and in the

programme, which follows. To spread the deliverables, and subsequent cost/resources, the decision was made that in this

time the bridge and tram route would also be constructed.

Contamination Remediation

Bridge

Tram Route

Phase 3 – 33 days:

The gas pipe is to be buried at a depth of 1m using a 450mm diameter pipe and follow the new route, as shown in the phase

diagram in blue. Details of this can be achieved whilst maintaining flow can be found in the programme.

Gas Pipe Works

Phase 1 Phase 2 Phase 3

Figure 50: Phase 1,2,3 of construction

36

Phase 4 – 42 days:

The fourth phase predominantly involves the levelling of the site. This is through both relocating the mound and levelling

the soil where green space is to be included for drainage. Geotextiles will be installed at this stage underneath the green

spaces, and the storm tank put in place.

Mound Relocation

Initial Drainage Works

Phase 5 – 116 days:

The fifth phase is the foundation installation for the main superstructures on site. Since much of the equipment used for

piling and pouring concreting will be shared across structures, it was decided to do all structures in parallel to minimise cost.

Foundation Installation - HQ, Terminus, Retail/Leisure

Phase 6 – 550 days:

The sixth phase, naturally following the foundations work, is the erecting of the superstructures.

Structure Errection

o HQ

o Terminus

o Retail/Leisure

Figure 51: Phase 4,5,6 of construction

Phase 4 Phase 5 Phase 6

37

Phase 7 – 67 days:

Phase seven sees the construction of the ground level hard infrastructure – this incorporates the car parking, roads, and

extending the supertram route from the bridge into the terminus.

Car Park

Roads

Tram track on site

Phase 8 - 42 days:

The eighth phase is the formation of the green spaces and SuDS. The shape / levels will have been mainly done in phase 4,

so this phase is more about finishing the SuDS with appropriate vegetation. This is done last so the other site activity doesn’t

damage the greenery.

SuDS Finishing

Landscaping

Phase 9 – 42 days:

The final stage involves testing and commissioning the site, followed by the contractor moving off site and the project being

officially over. The operators of the various structures/infrastructure will then move on to site and finalise Neepsend

redevelopment for opening to the general public.

Testing and Commissioning

Contractor Leaves Site

Handover

Figure 52: Phase 7,8,9 of construction

Phase 7 Phase 8 Phase 9

38

11.2. Programme To allow total time scales to be determined, a GANTT chart was created. The GANTT chart can be seen to break down the

project into phases, main tasks and sub-tasks. Access to the GANTT chart is available to the client upon request.

Figure 53: Gantt chart

39

Figure 54: Gantt chart (continued)

40

12. Costing

12.1. Full Cost Breakdown Below can be found a costing of the main 24 tasks within the 9 phases. Within Appendix H, a more comprehensive costing

can be found in which these main tasks are broken down into their 118 constituent parts.

Table 7: Costing of phases

41

12.2. Expenditure Throughout the Project By attributing a cost to each of the tasks on the programme, and finding the cumulative total as time progressed, a cost

profile for the project has been generated. The cost of an activity is assumed to be incurred at its scheduled completion

date.

On the graph, the end of the phases have also been included to give an idea of the total cost each carries comparatively

with the whole project cost. The time (x-axis) is in days and begins at the start of the project. However, years have been

marked on the graph for clarity of timescale.

A 20% contingency has been built in, and 2% as an assumed profit margin. This is the cost as broken down in the GANTT

chart.

For the purpose of charging the client, there will also be a 3% monthly retention, half of which will be paid upon completion,

and the other half paid 6 months after the completion of the project. This is to ensure client satisfaction with the finish and

to ensure the contractor corrects or pays for any defects.

Figure 55: Cost VS Time graph

12.3. Phase Costs Some phases are vastly costlier than others, as

can be seen on the graph above. However, as

the daily average cost analysis shows, when

duration of works is considered, the phases are

by no means equal in their expenditure. The gas

pipe burial is estimated to be the most money

intensive task – this can be put down to the

expertise and external contractors required.

Figure 56: Phase daily average cost analysis chart

42

13. Risk Assessment With this project being on such a large scale, there is obviously an associated level of risk across many different categories.

For the purpose of this report, the operational and future risks have been outlined – the construction based risks are

extensively outlined, as well as the following risks, in appendix H. This uses a likelihood-severity multiplication to form a

hazard score. Mitigation measures are then put in place to reduce this score. Ownership of the risk and mitigation method

is also defined.

13.1. Operational and Future Risks In this section, the future risks that may arise through the operation and future use of the site are outlined, and mitigation

ways are suggested for each risk. A full breakdown of these risks in a matrix format can be found in Appendix H.

10% Future Development at South of Site - Of the 25% of the site reserved for potential future development, 10%

is located in the flood plain at the south of the site. Since the southern part of the future development is located in

the flood plain (see section 2.7) it is suggested that any major future development being considered should be built

in the north-west of the site first, which is currently reserved as green space as part of the drainage attenuation.

Additionally, the south of the site suffers from a thicker band of alluvium, making for poor structural foundations.

Tram Switches and Crossings - The tram lines running through the site pose the most serious operational risk. As

discussed in 5.1.1, the transport routes have been laid out such that they do not cross at any point. The section of

tram tracks which contains switches and crossings for the access of platforms should not be accessible by the public

as a safety precaution. For this reason, fencing will be erected around this portion of the tram tracks.

Gas Pipe, Future Development - When constructing in the areas of future developments in the north west of the

site, the contractors and workers must be made aware about the location of the gas pipe. This will help mitigate

the risk of hitting the pipe during excavation.

Future Drainage - A large portion of the site is attenuated using green space, acting as filter strips, which then run

into swales. Future development on these green spaces, although allowed for in terms of the storm tank sizing and

pipe locations, would remove a significant percentage of the attenuation the current drainage network offers.

Gas Pipe Failure – Although installed by professionals, the unprovoked failure of the gas pipe running under the

site is of course a major hazard. A full evacuation plan should be put in place by the operators of the site, all staff

briefed for emergency action and the emergency services should be informed of this risk.

Pond Hazard- The pond is located in the southern-most part of the site. Despite the shallow slopes and shallow

water, there is a risk of drowning – especially for young children. Hence, low fencing will be erected around the

pond to restrict access.

Vehicle-Structure Interface - Car parking spaces are located in front of the façade of the retail building. Bollards are

to be installed immediately in front of the building at a regular spacing, designed as to be capable of stopping a

HGV travelling at high speeds (as common in airports). This also removes the capability of a car bomb to be left at

the base of the building.

Rail-Link Bridge – The bridge running from the retail area to the newly renovated train station is 9m high and runs

over the diverted Neepsend Lane. Falling from such height will lead to injury or death. Hence, the bridge will be

designed with sufficiently high barriers.

Tram/Pedestrian Bridge – Running over the River Don, and with trams down the bridge’s main passage, this bridge

poses a major hazard to pedestrians walking along the cantilever walkways. Again, protective railing will be

designed in to a safe height, and the pathway will not allow access onto the tram tracks.

43

14. Evaluation An individual evaluation is given in each appendix in order to make the client fully aware of the current design’s limitations

and future progression. This section aims to briefly summarise the effectiveness of the whole site solution, taking into

account the integrated parts of the design.

14.1. Major Assumptions Contamination remediation has been selected based on assumed contamination location – once remediation is complete

for a particular contaminant, if testing reveals that the thresholds are still broken, further (costly) remediation would be

required.

To create the ground models in line with the structural layout, the borehole data has been extrapolated. Also, the soil

conditions at the locations of the historical gas tanks has been assumed to be made ground. As outlined in Appendix A,

further site investigation is required to finalise the detailed design of foundations.

Structurally, when forming the GSA models, section sizes were assumed. This has been rectified within the design process.

Additionally, the bridge model assumes point loads along the arch in place of the ties. This has been discussed in depth in

Appendix F.

In terms of drainage, the critical duration storm, calculated using the proper formulae, has been used in the design of all

the stormwater infrastructure. Further analysis should be undertaken to confirm that the designed solution is suitable for a

larger range of design storms – potentially using more complex software. However, all the SuDS allow for climate change

and are designed with an additional factor of safety (supplementary to the required levels) so Techni is confident that the

solution is valid.

14.2. Meeting of the Brief Techni’s design team is confident that the proposed development presented in this document meets the brief specified by

the client. The only alteration that has been made is to the required number of car parking spaces, with the client’s

permission. This design decision has been justified within this document. Alterations have been made to the conceptual

design chosen by the project team to comply fully with the stipulations given by the client. Techni is committed to producing

the highest possible quality of work, and therefore any overlooked specifications will be rectified immediately, following

discussion with the client.

14.3. Further Detailed Design Required The detailed design outlined in this set of documents extensively presents the design for three of the major superstructures

with associated foundations, a detailed contamination remediation strategy, the site’s stormwater system and a

construction plan. However, as detailed design continues, there are other aspects which must be designed.

The other structures (retail centre, gym, swimming pool and train link bridge) are not designed to the same level of detail

within this report. When designed, it is suggested to include solar panels on the retail centre’s roof. It is anticipated that

foundations would be similar to the terminus foundations due to the loadings. The link to the train station is a key part of

the site’s masterplan, and so this should be installed before the site opens.

44

15. Conclusion Four main design features were targeted throughout detailed design: site integration, architectural merit, sustainability and

commercial interest.

The proposed solution sees the main development predominantly inhabiting the northern portion of the site - a decision

made to alleviate the flood risk and to take advantage of the better ground conditions. It also brings the supertram terminus

and the rest of the complex close to the existing railway, allowing an integrated transport hub. The site layout was designed

such that the transport links don’t cross, for safety and logistical reasons. Open spaces, high ceilings and natural lighting has

been included in every aspect of the development, as well as the addition of an atrium in the headquarters building to

improve ventilation and further natural light to permeate the building.

Discussions have been held throughout the concept design stage with the client, and all feedback has been taken on board

when continuing engineering work. This is evidenced within the specific appendices. A thorough risk assessment has been

undertaken for the construction, project and site’s future operation/development, including mitigation measures. Through

doing this, Techni is confident that construction can be carried out in a safe manner.

By progressing the conceptual design into a feasible integrated design solution, with associated construction planning, it is

the design team’s opinion that Neepsend if taken on by the client, has the potential to become a thriving transport, social

and recreational hub which would revitalise the area.

45

16. Bibliography Cannon Design. (2016). Material Life - Embodied Energy of Building Materials. Retrieved May 19, 2016, from

https://upstyleindustries.files.wordpress.com/2014/08/materiallife-embodied-energy-of-building-materials.pdf

Coal Authority. (2015). Coalfield plans: Sheffield City Area. Retrieved March 9, 2016, from https://www.gov.uk/government/publications/coalfield-plans-sheffield-city-council-area

Environment Agency. (n.d.). What’s in your backyard? Retrieved March 7, 2016, from http://maps.environment-agency.gov.uk/wiyby/wiybyController?value=S10+1PJ&submit.x=0&submit.y=0&submit=Search%09&lang=_e&ep=map&topic=floodmap&layerGroups=default&scale=10&textonly=off#x=435366&y=388486&lg=1,2,10,&scale=10)

Environment Agency. (2007). Review of 2007 summer floods. Retrieved March 7, 2016, from http://publications.environment-agency.gov.uk/PDF/GEHO1107BNMI-E-E.pdf

Galvanizers Association. (2016). Steel – Embodied Carbon. Retrieved May 19, 2016, from http://www.galvanizing.org.uk/sustainability/case-for-steel/steel-embodied-carbon/

Kellagher, R. (2013). Rainfall runoff management for developments. Retrieved May 5, 2016, from http://evidence.environment-agency.gov.uk/FCERM/Libraries/FCERM_Project_Documents/Rainfall_Runoff_Management_for_Developments_-_Revision_E.sflb.ashx

Millington, S. H. N. (2015). Trackbed Stabilisation, 2–4.

Neepsend Lane Gasworks. (n.d.). Retrieved March 7, 2016, from http://www.vhe.co.uk/remediation/recycling/neepsend-lane-gasworks.php

Purnell, P. (2013). The carbon footprint of reinforced concrete. Advances in Cement Research, 25(6), 362–368. http://doi.org/10.1680/adcr.13.00013

Roger Bullivant Limited. (2016). Vibro Stone Columns. Retrieved May 18, 2016, from http://www.roger-bullivant.co.uk/downloads/brochures/brochure_gi_vibro.pdf

Shucksmith, J. (2016). A Guide to Advanced Drainage Design.

Soilutions. (2016). Stabilisation. Retrieved May 20, 2016, from http://www.soilutions.co.uk/services/soil-remediation/stabilisation-solidification/

SuDS Manual 2015. (n.d.). Retrieved May 4, 2016, from file:///C:/Users/cutberto/Downloads/C753 Part B Chapter 1 (hi).pdf

TerraTherm. (2016). In Pile Thermal Desorption. Retrieved May 20, 2016, from http://terratherm.com/thermal/tch/index.htm

Tomlinson. (2001). Foundation Design and Construction. Retrieved May 16, 2016, from https://www.scribd.com/doc/129581419/Tomlinson-Foundation-Design-and-Construction

Vibro Menard. (2016). Stone Columns. Retrieved May 18, 2016, from http://www.vibromenard.co.uk/techniques/stone-columns/