Official Information Request - 2 June 2020

Attachments:

• Appendix 1: Rotorua WWTP Discharge Consent 60739 - Annual Summary to 27 March 2018
• Appendix 2: Rotorua Wastewater Treatment Plant - Design Statement for Preferred Treatment Arrangement
• Appendix 3: Excerpt from Rotorua WWTP AEE Application
• Appendix 4: Current Resource Consent for the Rotorua Wastewater Treatment Plant

Response:

Thank you for your letter dated 2 June 2020. Following is our response to the information requested.

1.0 Confirmation of whether the Rotorua Wastewater Treatment Plant has the capacity to receive and treat the wastewater from the Lake Tarawera residence (i.e. how much of the capacity is currently being used). This includes details of what the Plant's current design capacity is, what volumes it is currently receiving and treating, what volumes it is predicted to receive and treat due to growth (and over what period) your estimation of whether infiltration and inflow reduction works will reduce the flows to the Plant.

The last upgrade to the Rotorua WWTP was completed in 2012 with the installation of a parallel (side stream) membrane bioreactor (MBR) that increased the capacity of the existing plant to treat the following flows up to 2051.

Average daily flow = 24,000m/day

Peak wet weather flow = 40,000m/day

(up to the current nutrient limits)

The nutrient removal capability of the plant was set to achieve the consent limits, as follows:

Total Nitrogen = 51 ton/annum at the outlet of the plant

Total Phosphorous = 4 ton/annum at the monitoring site in the Waipa Stream

Based on the latest annual report dated 27 March 2018 (Appendix 1), the average daily flow treated at the plant is 22,214m/day. With an estimated Average Daily Flow from Tarawera at 409m/day, there is sufficient capacity for the existing plant to handle additional flows from the Tarawera if it is connected to the existing Rotorua Urban Area Sewerage System.

Please note that the average daily flow measured in March 2018 already includes flows from new communities connected to the system such as Okere Falls/Otaramarae/Whangamarino, Mourea/Okawa Bay, Brunswick/Rotorua, Okareka and Hamurana/Awahou.

A sewer rehabilitation programme is in place to manage infiltration and inflow into the system to ensure that it does not significantly affect the capacity of the wastewater treatment plant.

2.0 In terms of the proposed upgrade to the Plant, how much will it increase the design capacity by and confirmation of whether the upgraded Rotorua Wastewater Treatment Plant has the capacity to receive and treat the wastewater from the Lake Tarawera residences? The same details for the upgraded Plant are sought as those set out in 1.0 regarding the existing Plant.

The proposed upgrade of the Rotorua Wastewater Treatment Plant has been designed to treat the following flows:

Average Daily Flow = 25,000m/day

Peak wet weather flow = 60,000m/day

The nutrient removal capability of the plant was set to comply with an expected higher consented limits, as follows:

Total Nitrogen = 32.4 ton/annum at the outlet of the plant

Total Phosphorous = 3 ton/annum at the outlet of the plant

The design of the proposed upgrade included the connection of the Tarawera community to the Rotorua urban area sewerage system through the Lake Okareka sewer trunk main.

Refer to Appendix 2 - Rotorua Wastewater Treatment Plant - Design Statement for Preferred Treatment Arrangement and Appendix 3 - Excerpt from Rotorua WWTP AEE Application - pages 23-24).

3.0 What is the estimated wastewater volume that will be received from Lake Tarawera residences?

The estimated wastewater volume that will be generated by the Lake Tarawera residences and facilities within the scheme area is 409m/day. The details of how this volume was estimated is shown on the following:

(a) Existing and Future Development

Table 1 below presents the current count of sections with dwellings and vacant sections in Lake Tarawera, including the extended area of benefit. The count is estimated in terms of housing unit equivalent (HUE).

Table 1 - Existing and Future HUE Estimates

(b) Flow Estimates

Tarawera Average Daily Flow (ADD)

• Average sewage flow per capita per day : 220L
• No. of persons per house : 3.1
• Average daily flow = 220 (3.1) (600) = 409,200 litres/day = 409m/day

4.0 Are any further resource consents required for the Rotorua Wastewater Treatment Plant to receive the wastewater from Lake Tarawera residences?

There are no further resource consents required for the Rotorua Wastewater Treatment plant to receive the wastewater from the Lake Tarawera community.

An earthquake consent may be required to manage the excavation of trenches for the pipeline. This is however considered as low risk.

5.0 A copy of the current resource consent for the Rotorua Wastewater Treatment Plant

Attached is a copy of the current resource consent for the Rotorua Wastewater Treatment Plant (Appendix 4).

6.0 An update of where the resource consent process is at for the proposed upgrade to the Plan, including whether there has been a decision by the Regional Council yet?

The application has been directly referred to the Environment Court for a decision.

Attached are links to the relevant documentations related to the application.

(a) Report and Recommendation of Consenting Authorities (Planning Reports)

https://atlas.boprc.govt.nz/api/v1/edms/document/A3538611/content

(b) Rotorua Lakes Council's Wastewater Treatment Plant Application which sits under

RM18-0508: Rotorua Lakes Council

https://www.boprc.govt.nz/environment/resource-consents/notifications

You have the right to seek an investigation and review by the Ombudsman of this decision. Complaints can be sent by email to info@ombudsman.parliament.nz, by fax to (04) 471 2254, or by post to The Ombudsman, PO Box 10152, Wellington 6143.

Publication of responses to LGOIMA requests
Please note: Our LGOIMA responses may be published on the Rotorua Lakes Council website after they have been responded to, with requesters' personal details withheld. If you have any concerns about this please contact the Council on info@rotorualc.nz.

Yours faithfully

Jean-Paul Gaston

Group Manager, Strategy / Privacy Officer