Dormer Construction

SCIRT Corbel Repairs

October, 2016

SCOPE

The scope of this contract was to construct new reinforced concrete jackets around 6 old manholes for the Christchurch Northern Sewer Relief Trunk Main that had been damaged during the earth quake.

The issues that we had to overcome were, de-watering the sheet pile pit, stopping the ground water from entering the pit from the surrounding areas, while not pumping out silt from the surrounding area so that the manhole did not sink, plus sealing up the cracks in the manhole and pipes to allow for a dry pit for the concrete jacket to be constructed. We managed all these processes on all 6 separate manholes, much to the delight of the customer, as the previous contractor could not achieve this.

Extra over this work was considerable sewer bypass pumping of excessive sewer flows on the Northern Relief Sewer Line, to complete certain sections of this contract aa well as over pumping of structures allowing pipelining and repairs.

There was considerable in-situ concrete works and reinforcing placement, as the existing structures were encapsulated as part of the works to maintain high sewer flows.

PERFORMANCE

Environment

We had no Environmental issues. There was a very high standard required due to Large volumes of raw sewerage being handled and over pumped.

Health and Safety

We had no H&S issues, plus we scored 100% on 2 Fletcher H&S audits.

Programme

We completed the work on schedule.

Cost/Budget

We completed the works on budget.

Pump Station Civil Construction

June, 2015

Pump Station Pump Station

EXPERIENCE

Dormer Construction Ltd takes pleasure in completing construction of deep structures especially sewer and storm water pump stations.

We as a company have constructed pump stations all over New Zealand. From Central Otago to the top of the Coromandel Peninsula in the North Island.

Dormer Construction has extensive experience in the construction and installation of pump stations (sewer, storm water, fresh water), including installation of all pipework, valving, instrumentation and electrical work, and all commission and testing. Our installation method of casions has been by the sinking down by the top down method and or sheet piling, dewatering and full excavation construction.

Much of the work is associated with large subdivision developments and council infrastructure. In the recent period Dormer Construction have worked for SCIRT under the rebuild of the Christchurch City Council and have built an area wide scheme of pump stations and lift stations where we built them to the new standard and code.

Working in difficult ground conditions (water levels and material types) is second nature to us – with effective planning, preparation and sound methodologies we are able to mitigate delays and subsequent costs often experienced in these situations by others. Working safely and with care produces the level of quality and functionality determined by the specifications and workmanship sought by clients. Please see below our portfolio of pump stations completed over the past 25yrs;

Project

6m deep pump station
7.5m deep pumps stations x 2
7m deep pump stations x 2
5.5m deep pump stations x 2
7m deep pump stations x 7
6m deep x 2.4m dia pump station
5m deep x 1.8m dia pump station
9m deep x 3m dia pump station (into solid rock)
7m deep x 1.8 dia pump station
7m deep x 2.4m dia pump station
6.5m deep pump station x 2
6m deep pump station
8.5m deep x 1.8m dia pump station
6.5m deep pump station x 2
4.5m & 5m deep pump stations

Client/Purpose

CCC SCIRT works Cranmer Square
CCC, Groynes Subdivision
WDC, Sovereign Palms Subdivision
CCC SCIRT works Shirley
CCC SCIRT works South Brighton
Selwyn DC, Springston
Queenstown DC, Arthurs Points Subdivision
Kaikoura DC Ocean Ridge Subdivision
WDC, Moorcroft Subdivision, Kaiapoi
WDC, Northbrook Waters Subdivision, Rangiora
WBOP DC, Waihi Beach
Selwyn DC Claremont Subdivision, Templeton
CCC Ellington Subdivision
CCC SCIRT works, Bromley
WDC Sneyd & Charles Street Kaiapoi Pump Stations

 

Kaiapoi Sewer Pump Stations

June, 2015

SCOPE

Dormer Construction won the invited tender to build 2 sewer pump stations in Kaiapoi for the Waimakariri District Council.

This consisted of one pump station in Sneyd Street with the wet well and valve chamber that needed to be constructed in the footpath, and the electrical cabinet in a separate enclosure behind the foot path.

The critical items for this installation was locating the lids inside the existing kerb line and matching the footpath level, while keeping the inconvenience to the residents to a minimum.

The second pump station was in Charles Street, this was a relatively complex build, with a architecturally designed Switch Board Building. The building had exposed aggregate concrete panels with purple heart timber battens attached in the resemblance of the Waimakariri River tributaries.

There were very high water tables that where required to dewater for the duration of the works. That included installing 2100 Diameter wet wells at 6.5m deep, along with associated valuing, rising mains and electrical components.

PERFORMANCE

Environment

The issues that needed to be addressed was to work with the residents to keep interruption to them to a minimum.

Health and Safety

No personal harm incidents accrued during the construction of both pump stations.

Programme

The customer had no issues with the construction programme timing.

Cost/Budget

The contract was under budget, with no major variations required to complete either pump station.

Box Culvert Underpass

June, 2015

This contract was for the installation of a 3mx2m x22m long cattle underpass  and 40m wide and 22m long approach race, under a public road crossing. Site conditions involved a high water table, alluvial shingle, and artesian water pressures. In managing the site conditions, particularly the water table and soil type, Dormer installed global dewatering around the whole site, then sheet piled half of the road crossing at a time, then repeated the sheet piling process for the other half of the road crossing. 11KV overhead power lines hazard, within the work zone, was managed and controlled to eliminate risk of injury.

To achieve watertight solutions, the underpass section was wrapped on Volclay Voltex and Swelltite and the approach races had either hydrophilic seal strip or Rearguard Waterbar installed at each construction joint . In addition to all the waterproofing there was also anti-flotation beams poured to the structure to stop it from floating.

Northbrook Waters Subdivision, Pump Station

May, 2015

In 2004, Dormer Construction Ltd constructed and completed for the Waimakariri District Council a 2.4mtr in diameter by 7mtr deep Pump Station.

DCL designed the creek bypass. To create a dry work area for the creek crossing sheet pile coffer dams were used. DCL used eight of their 6″ pumps for the bypass and dewatering. Two excavators were used, one on each side of the stream, allowing the work to be conducted quickly and efficiently.

Job was completed under a very tight time frame for the Waimakariri Council.

 

 

Waihi Beach, Pump Stations

May, 2015

In 2000, Dormer Construction Ltd constructed and completed 2 Pump Stations for the Western Bay of Plenty Council.

Waihi Beach was undergoing major construction of sewer reticulation and civil works at the time. It was the largest in New Zealand that had taken place in the last 10yrs during the year 2000.

During the contract DCL completed over 8km of sewer pipe lines. This included 150 manholes, 2km of well point dewatering and 2 pump stations.

The Pump Stations were all built to design and standards that were specified in the contract. The pump stations involved dewatering to depths of 5mtrs and excavations to depths of 5mtr to install the emergency storage chamber and wet wells. The bottom of the wet wells were at least 4mtrs below the high tide mark within the sand dunes.