"And that bridge is access to just two paddocks, 5ha of land, but it just goes to show our commitment in cleaning up the stream," he told the Dannevirke News.
"We've also fenced the main two streams on the property."
Other investments include putting a stirrer into their pond and increasing their effluent capture area to twice it's size.
"Because of those efforts we gained our Horizons One Plan consent without modifications," he said.
"But we're going to drop another eight units of N [nitrogen], by wintering less cows, which will mean less effluent."
Currently the Fields milk 260 cows, a drop of 50 from the 310 wintered last year.
"This spring we had a very compacted calving and because I'm getting older the way I like to farm isn't as a business farmer, but for the lifestyle, so fewer cows benefits me and the environment," David said.
"In time I'd like to do more riparian planting, but there's only so much you can do, especially with the dairy payout dropping even lower."
The bridge, long and with tin sides ensuring no effluent can flow into the stream, has been in a year and is appreciated by his dairy cows.
"The cows don't defecate on the bridge and we're also quite happy with what we've done with fencing and planting and we'd like to do some more. The trees have started self-seeding now as well, which is great because it gives the cows some added shelter."
The effluent pond also provides a return, with the average dairy cow producing roughly $25 worth of nutrients each year as farm dairy effluent.
By capturing and reusing it farmers can achieve a solid reduction in their fertiliser bill.
Fonterra area manager for the Hawke's Bay, Tony Haslett, said while there are only a handful of dairy farms in the catchment, they have all gone to extraordinary lengths in recent years to ensure the water quality in the Mangapapa Stream is sustainably improved.
Over the past 10 years the stream's dissolved inorganic nitrogen levels have fallen by more than 13 per cent a year.
The Fields have been farming the property for 11 years, but going back 17 years David recalls sharemilking there and the improvements since then have been dramatic.
"Then the creek wasn't fenced, it was one whole paddock and the cows had no water troughs and drank out of the creek," he said.
"We've made a big effort to protect our waterways and having clean streams is an important part of our farming philosophy."