Otarawairere/West End Project FAQs
Following the July 2004 flood event and landslips in Otarawairere/West End area, the Council initiated investigations into measures that could be taken to reduce and minimise the risk of landslip occurring in the future.
Below are some Frequently asked questions and answers about the Otarawairere/West End project.
FREQUENTLY ASKED QUESTIONS
What is the Council trying to achieve?
Reduce the risk of danger to both people and property by reducing the risk of further landslips at the Otarawairere/West End escarpment.
Will the proposed works prevent further landslips?
Recent serious landslips were triggered by ground saturation from wastewater infiltration and stormwater from developed areas (properties and roads) on the escarpment. By removing this stormwater and wastewater away from the escarpment, the proposed works will minimise and/or eliminate the trigger mechanisms thereby significantly reduce the risk of further landslips.
The risk of landslips will not be completely eliminated, due to factors such as earthquakes, soil weathering and natural stormwater flow over pervious (e.g. vegetated) land.
What about stormwater discharged from undeveloped land?
It is not proposed to control the natural flow of stormwater from undeveloped land such as farmland or reserves.
Is the water discharged from the roading network proposed to be managed?
Yes. Stormwater from Cliff/ Brown Road and from Otarawairere Road that contributes to the instability of the escarpment and adjacent areas will be controlled of as part of the proposed works
Has the proposal been peer reviewed?
No. However, the Tonkin and Taylor team working on the project for the Council includes experienced geotechnical, drainage, water, environmental engineering and planning staff with a combined experience of almost 100 years. The company’s Project Manager (Costas Chryssafis) is a Chartered Professional Engineer and a Chartered Environmentalist and is a Member of both New Zealand and British professional institutions. Mr Chryssafis has almost 30 years experience in water, wastewater and stormwater projects.
Under the company’s ISO 9001 certified project and contract management systems projects of this sort are design reviewed and checked at concept, preliminary and detailed design stages.
The project design has been identified after detailed investigations of the recent landslip and after considering the real threat of further instability posed by the stormwater and wastewater issues described above.
What other options have been considered?
A total of five options were considered at the concept design stage in terms of their technical merit and cost. The options were described during the public meeting at the council offices on 6 May 2005. The option selected presented the best technical merit and cost benefit.
Was the “do nothing” option considered if so why was it dismissed?
Yes the “do nothing” option was considered and dismissed because of the significant risk of further landslips due to stormwater and wastewater from developed areas on the escarpment
Is it proposed to reticulate the wastewater (sewerage) from Otarawairere?
Yes. The original proposal was to retain the function of existing septic tanks and to pipe away the semi-treated wastewater from the tanks. The proposal at this stage is to render the septic tanks inoperative and to pipe away the raw wastewater from the properties included under the project.
Who will pay for the connection of private stormwater/wastewater to the public system?
The cost of the private connections and the reinstatement of private properties are factored into the project cost, and the costs of the project will be attributed as per the Hazard Mitigation Funding Policy.
How much discharge does one person create?
• Stormwater
The flow rate and volume of stormwater discharged from each property depends on the area of roof and hard surfaces such as a driveway on the property. It also depends on the return frequency of rainfall events adopted for the design. Given the serious implication of landslips, rainfall frequencies of 1 in 20 years, 1 in 50 years and 1 in 100 years are being considered in the project.
For example, a property with 200m2 of roof and 150m2 of paved area would generate a peak flow of about 12 litres/second in a 1 in 50 year short, intense storm. In a 1 in 50 year storm lasting a full day, a runoff volume of over 60m3 can be expected to be generated from this roof and paved area.
• Wastewater
The design average wastewater discharge per person in a normal residential home is typically 200 litres/day. A peak flow of five times this amount is allowed for in design to cover wastewater flow at peak times of the day and to cover stormwater inflow and infiltration into the sewer pipes.
Although wastewater flow is much less than stormwater flow it is still a serious contributor to ground instability in this case because it is currently being disposed of in septic tanks which saturate and destabilise the ground
When is the physical work planned to occur?
The Council will consider the design and the community feedback at a meeting to be held in February 2007. Subject to approval from the Council, a Resource Consent will be lodged with Environment Bay of Plenty and Whakatane District Council, concurrent with the resource consent process the detailed design work, and the Tender process will proceed.
Dependent on the outcome and the time taken to obtain a Resource Consent, the physical work could commence this summer. If the resource consent is notified and/or there are objectors the process would be delayed.
If work commences this year, it may be divided into two phases with urgent work carried out this construction season and other work undertaken in the 2007/2008 construction season,
How will my property be affected?
Properties in Otarawairere/Cliff Road/Brown Road will be connected to the public wastewater/stormwater system. The inconvenience to private land owners will differ depending on the location and condition of existing pipes to septic tanks, and to discharge outlets for stormwater.
A typical example will be that a drain will be dug from the septic tank to the road. Any fence, driveway or gardens in the path will need to be disturbed, however they will be re-instated and wherever possible works will be planned to avoid landscaped areas. No buildings will be affected.
Two private properties on West End Road will be affected with earthworks required to connect the wastewater pipes to the reticulated systems.
On site meetings will be held with property owners prior to the works being undertaken. The contractors will be present at these meetings.
Work on private properties will not be carried out before 8am or after 5pm without prior approval of the affected property owner.
All care will be taken to minimise impact on individual properties, work will also be required in the road reserve and in other reserve areas.
Works along road reserves could affect traffic flow and temporarily restrict access to private properties.
Timelines will differ but an estimate would be that work undertaken on individual properties will take no longer than two or three weeks
Am I able to subdivide my property?
The design proposals caters for the current number of properties in the affected area. Catering for subdivisions could increase the cost of the project as the pipe capacities have to be increased to carry flows from properties developed on the subdivisions.
There is capacity in this design for further development however, conditions of subdivision consents may require any developer to include wastewater systems.
The Policies, objectives, and rules of the Proposed Whakatane District Plan will need to be observed, further advice can be sought from Council Planners
What will happen to trees and other vegetation on the escarpment?
Most of the trees and vegetation will not be affected as underground drilling techniques will be used to install the drainage lines which will run down the escarpment.
The Council is also working with a local arborist to ensure that the best possible options are reached to protect any other significant vegetation that might be affected.
Who will pay for this work, and how much?
The Council’s Hazard Mitigation Policy identifies who pays for the Hazard Mitigation works
The Council had budgeted $2 million for this work, based on the estimates available at the concept design stage.
The Council has received advice that the costs of the project have increased to $2,99 million including contingency. The main reason for the increase is attributed to an escalation in construction costs.
These costs are based on the above mentioned budget and costs, and are subject to change. Click on link to view spreadsheet identifying the cost per property.
What action can I take if I disagree with the Council’s Hazard Mitigation Policy?
The Funding Policy on how the mitigation works is funded was consulted on during the Long Term Council Community Plan 2006 – 2016, and was adopted by the Council last year.
A written submission can be made to the Council requesting it to a re-consider the policy as part of the 2007/08 Annual Plan consultation process. The Council will consider whether or not it is appropriate to vary the Policy.
A submission in support of the policy can also be made.
For more information or to get an update you can email Projects Manager-Community Projects or you can phone on 07 306 0500.