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Imperative 5: Net Positive Water

INTENT
To meet all water demands within the carrying capacity of the site and mimic natural hydrological conditions, using appropriately-sized and climate-specific water management systems that treat, infiltrate or reuse all water resources on-site.


REQUIREMENT
Project water use and release must work in harmony with the natural water flows of the site and its surroundings. One hundred percent of the project’s water needs must be supplied by captured precipitation or other natural closed loop water systems, and/or by recycling used project water, and must be purified as
needed without the use of chemicals.


All stormwater and water discharge, including grey and black water, must be treated onsite and managed either through reuse, a closed loop system, or infiltration. Excess stormwater can be released onto adjacent sites under certain conditions.

how the Living House complies

We started the LBC process trying to use the Natural Flow wormarator system (in conjunction with the Alo Aqua system mentioned above. Thus we were going to process our grey water separately from our black water. To treat waste water on site in New Zealand you need to have a resource consent. Our initial resource consent application (to subdivide) caused a fair bit of confusion within Auckland Council as they weren't 100% sure what we needed to do in terms of how they needed to review and approve this. The first response from them was that we needed to get our design peer reviewed by a Civil Engineer experienced in on site waste water treatment design. We did this and working through the design process with him resulted in many changes to the design to allow it to be in accordance with TP58 (which governs on site waste water treatment design in the Auckland  region).

However once the Regional Waste Water team from Auckland Council got hold of it they advised that we couldn't do this through our Sub Division Resource Consent as a permitted activity and that we would need to apply for a separate discharge consent. So we then had to write a new and separate application for a discharge consent, pay another $4,000 and submit this to Auckland Council. Following the initial review of the application we we then hit with another Section 92 request (which was not completely unexpected).

At the time that we received the Section 92 request from Auckland Council I also received a phone call from the lady dealing with the application. She said that we were pretty much trail blazers in this area and that since this was a first that they thought this would cost around an additional $5,000 to review and process (on top of the $4,000 that I had already paid - not to mention the $2,000 that we spent on the chartered civil engineer earlier). She also said that she thought fundamentally that our site was too small and that we couldn't meet the requirements of TP58 and therefore that the system would not get approved. 

However since on site water treatment is one of the key components of the Living Building Challenge (and quite frankly appears to be the hardest part to achieve) we were not willing to leave it there. So after working through all the issues that Auckland Council raised through the Resource Consent and then Discharge Consent process we moved towards the idea of installing composting toilets. 

 

The major reason for moving towards composting toilets was to reduce the L/day that we would need to discharge to the evapotranspiration beds. Our site is on the smallish side to do on site black and grey water treatment and discharge and therefore we needed to eliminate as much waste from the liquid water treatment process as possible.

 

 

After much consultation and deliberation our  application for a discharge consent was approved. Here is the final consent.

The Living House is located in Beachlands, Auckland. Beachlands is unique in Auckland in that it is completely without access to a town potable water connection. Therefore all properties in Beachlands (and Maraetai) must provide their own potable water. This is generally done with through the installation of rain water tanks, or through the use of a bore. 

 

The Living House is using two 25,000L concrete water tanks provided by Dart Concrete) to supply all of our potable water needs. This rainwater tank will collect rainwater from the roof of the main dwelling and store it for future use. 

Potable water
Storm water

The storm water design for the Living House has been very challenging. Not the least because we stupidly did not read the LBC technical manual very carefully and did not realise that  you were not allowed to connect to a council provided system and therefore submitted their Resource Consent application showing an overflow connection from the Living House rainwater water tanks to the council provided swale on First View Ave. This is not allowed but we only discovered this the day after Resource Consent approval was received. 

We then spent the next 5 months trying to come up with an alternate acceptable onsite stormwater design that is acceptable to Auckland Council . In attempting to deal with all of the site rainwater/stormwater onsite we have had to change the design of the roof from a traditional gabled roof to a flat green roof. We have also had to undertake incredibly detailed rainwater/stormwater calculations to try and determine how much - if any - overflow would occur from the 50,000L of rainwater tanks. To do this we downloaded 10 years of rainfall data from NIWA and then undertook a daily water balance calculations (see below spreadsheet) to try and determine when and by how much the rainwater tanks would overflow. 

This was quite a complicated process and the first thing it showed us was that we needed to change a large portion of the roof from a traditional roof to a green roof. From then it was a matter of trying to balance the relationship between the green roof and the traditional roof. 

In January 2017 we received approval from Auckland Council (Resource Consent team) on our Green Roof and its subsequent reduction in the quantity of stormwater that is going to be produced on site. HOWEVER they still require us to provide an overflow connection to a council provided system just in case future homeowners decide to remove the green roof.

 

We are therefore managed to get the following overflow design approved. This system basically works like this:

  1. A submersible sump pump with a high level float switch is located in the rainwater tanks. This pump will act as the potable water supply for the house but will also activate should the pump reach the high level

  2. The overflow from the tanks is connected via a 2 way valve

  3. The primary overflow is to the swimming pool. If the swimming pool is full it overflows to the soak away gravel that completely surrounds it (existing). The pool backwash is connected to a separate 1000L reuse tank.

  4. The second overflow connection is to a surface channel in the concrete ROW that is gravity fed to the swale on 119 First View Ave.

Grey water
Black water

We started the LBC process trying to use the Alo Aqua system to treat and reuse our greywater. Thus we were going to process our grey water separately from our black water. However one of the key components of the LBC is the Red List and Alo Aqua's supplier Matala were not willing to go through the process of proving that the Alo Aqua system was Red List free (PVC being the main issue). 

We therefore had to try and find another grey water system that we could use on site that was Red List compliant. This proved to be a major challenge. We even researched other LBC projects to see what systems they had used. We found one that had been used onthe Bertschi Living Building in Seattle  which was the Aqua2Use system so we contacted the Australian distributor who had never heard of the LBC. When he asked people further up the line they also had never heard of the LBC or the Red List. 

We're currently talking to Waterless Composting Toilets NZ (Dylan) who has been super helpful and who distributes in NZ on behald of Eco Flo. Eco Flo are willing to swap out any PVC part of their system for ABS which means that we think we have found a Red List compliant grey water filter system. The trick now is to get this system (called Nature Clear) past Auckland Council. 

 

ETS Beds

A major part of the Grey Water system is the evapotranspiration beds that the grey water discharges to.  Here are the steps to creating an ETS bed:

Step 1: Dig out 250mm deep into the soil (to the dimension size of the bed you are creating. It shouldn't be more than 1.5m wide and 13m long for each bed ideally.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Step 2:

Put 50mm of sand on the bottom of the excavated bed and then top that with 200mm of 20mm-40mm aggregate

Water