Solving an urban drainage problem

When you buy a new section in a swanky new development you expect you will get a safe place to live with a useable section. The terrain is flat and grassed. T1 ground, so not prone to liquifaction during earthquakes and too far from the sea for tsunamis. It's a town known for good drainage and you think, " Well,  it should be good for gardening." 

The covenants are onerous and owners are expected to spend quite a bit of money on landscaping to increase the amenity of the subdivision.  Council charges high rates for the privilege of living in Selwyn. The general area was a farm. My part of the subdivision used to be, I have discovered, an orchard.

Since late 2018 the back half of my section has been getting progressively damper, to the point of serious surface flooding. A large part became totally unusable. All my plants had died and it was impossible to get a trowel in to dig out weeds. Each time it rained I felt incredibly stressed as the water crept across my section, rotting my raised beds and compost bins.

Clearly, the soil would not drain. One neighbour wasn't having problems such as this but the other was, though to a much lesser extent. They had lost trees and plants too, tried to dig out their beds to a depth of 1m and replace the shitty soil with compost but to limited good effect. What to do? 

I went in person to the Selwyn District Council to see what the problem could be and what to do about it. At first they did not want to deal with it, telling me to simply send an email with some photos. Yeah, right! Knowing I would be fobbed off if I did that I stood my ground and asked to speak to an engineer. Eventually, after a bit of nervousness on council staff's part they agreed. After a wait, a stormwater engineer spoke with me saying Council don't give advice and that anything on my section is MY problem. They only care about what's on the street. I pointed out there was clearly a problem with my section and the council was in partnership with the developer. I also pointed out I am a pensioner with everything I have, sunk into my home. Could there be a problem relating to the sewer crossing my property? The engineer said he would get back to me.

Later that day I was pleased to see a council contractor drive up to take a look. He agreed it was not normal but we could not smell effluent. He felt the ground was the problem, as did I, but he decided he would check the sewer manhole further down the road to see if levels had dropped. I did not hear back from Council for 10 days so I rang and left a message. It was not returned. Clearly, they had only shown some interest in case a public health scandal was looming. Yet again I had to go in and front up. Not good enough SDC. The engineer said he had been too busy to get back to me or return my call. I told him I paid my rates and had worked for a council in the past so I understood all about service. It was better service where I had worked than what I was receiving from SDC, that you do NOT just ignore a ratepayer or customer. It takes little effort to send a quick email to say exactly when I could expect info. He then said he would send me an email regarding the matter. He never did.

With yet more rain falling in winter I was getting desperate, worried for my plants and expensive landscaping so I contacted the subdivision developer (but not the person I had had such unpleasant dealings with during the possum affair). I was pleased he took my problem seriously and he sent a couple of employees around to check it out. They agreed it was not normal and not my fault. They took pictures and it all seemed like a useful and productive meeting. They would discuss and find a solution.

They came back a few days later with a slightly different attitude, looking for a way out of what was clearly their responsibility. They admitted the ground was not good quality but said I must take some responsibility for the problem. You what? Well, apparently they had now decided it was the fault of my lawn. 

They had looked online and found the manufacturer and the description that said when laid it would help germination by conserving 30% of the humidity applied at the time. With spades and crowbars they started digging parts of my lawn up to prove a point. I was shocked and not convinced. What I saw was good root growth and a lot of impermeable soil underneath.

I contacted the lawn manufacturer to let him know what was being said about his product. He was shocked and gobsmacked. They've been in business many years, have never had a drainage problem because it's a biodegradeable product which disappears within months once it is laid. Still, I felt shaken, having to now defend my lawn which couldn't drain because the soil underneath could not absorb water, water could not flow away. 

Eventually the developer agreed to remediate the drainage after a friend had put me in contact with the Council Development Engineer via a roundabout route. (see, it's who you know) He was very familiar with the development, of course, very nice and popped over to take a look. He told me what could help the drainage. I wrote a detailed instruction and drew a diagram for the developer to plan the repairs. Small modifications to the relocation on my compost bins were necessary to avoid digging down and distrubing the sewer (there's an easement above it).

A hydrovac machine arrived behind the back of my property. A big sucky truck and waterblaster were used to break up the compacted ground, rocks, silt and clay. It was a hell of a job, even for that machine. It took hours longer than planned as my section was full of tree roots. Clearly the development contractor had not prepared my section properly, scaped the shit off the other sections in my street and dumped it and compacted it on my lot. The soil used was clay and silt with rocks, not at all what should have been laid down. There's nothing I can do about that but I am so disappointed.

I do appreciate that the developer has tried to give some drainage relief because I do not have the resources to try to fix something that should never have happened. They found a solution (proposed by the council development engineer) to cause the least damage to my urban property as machinery cannot access my section now.

A trench was dug, a narrow soakpit constructed. Filter fabric was laid around novacoil drainage pipe to be set and connected to a perforated pipe in the middle of the soakpit. The pipe in the soakpit has a lid so it could be inspected in future or silt sucked out if neccessary. They had to go down 2m to get past the hard pan and would have liked to go deeper but the rocks in the bottom were too big for the hydrovac to remove.

Fine gravel was then tipped in followed by larger gravel. I was told I would not be getting gravel that matched my paths alongside as it was too expensive. It's ugly as hell that part of my section, but at least the trench drains. Twenty centimeters away from it the soil does not drain, of course, so I will always have a problem, though lessser than what it has been. 

They have screwed plywood to the bottom of my compost bins to stop soil getting into the gravel. OK but useless for a compost bin so a neighbour has drilled holes in the bottom and I have laid weedmat to stop soil working down into the gravel and trench, yet allowing rainwater to drain away. The Council engineer had said I could not plant anything in the gravel nor have a raised bed on top. The council development engineer never replied to my project report and photos and request for  confirmation that what had been suggested and done was OK. Folks tell me Council will be distancing itself from my problem.

Through no fault of my own I cannot use part of my section as I would like. It was supposed to be a bushwalk. Now it just resembles the Waimakariri riverbed with sludge sprayed all over my fences and veges. I need to find a way to make it more aesthetic. Money, money.

Waterblasting does not remove the sludge so I have had to buy paint to repaint my fences. Part of my lawn has been destroyed. It's disappointing. It could have been worse but should have been better. Thank goodness the developer pitched in. I hope they have learnt something but they insisted to the end my lawn was to blame though parts nearby not in grass are still sopping wet. I can see I will have to do more drainage work myself in future, to save my potager beds.

It's hard on your own as a pensioner to deal with powerful organisations and businesses who may or may not want to play fair. It's really stressful and you always have to stick to your guns as a minimum but that is no guarantee of resolution. I could not have got very far without a little help from those who know 'the system'. I hope those of you with drainage problems find the construction details useful. I also hope past problems with possums and water are the last problems with my section.