Distance: 4.5 km (2.5 DOC hours) - Unmarked route, clear - Easy-moderate terrain
Altitude: 1174m to 1583m. Gain: 377m. Loss: 675m . Gradient: 14 deg (Moderate)
Skills:

Unmarked route, clear (7/9)
Unmarked route, follows obvious geography (river, spur, trail, etc)

Primary, unmapped (2/5)
Route not on maps, but is principal access to hut or along range / catchment

Moderate (difficulty: 3/5)
Occasional moderate climbs

Easy-moderate (difficulty: 2/5)
Tussock / river-gravel / open bush / cut track

Unknown (difficulty: 0/7)
Not specified

None (difficulty: 1/6)
No unbridged river crossings

Unknown (difficulty: 0/7)
Not specified

Climb the slope north of the smaller lake beside Lake Nerine to gain the ridge west of Point 1594. Drop down rocks to the next lake and go around it the gully to the northwest. Cross the head of the gully and sidle north, all the way to Park Pass. There is a cairned route along the eastern flank of the ridge as you traverse very steep tussock slopes and the odd scree slide, but the cairns are sporadic and there's no obvious grand trail. A trail picks up at the flat ground between 1220m and 1240m going through a boulder field, and crosses to the western side of the ridge. Drop down to tarns on Park Pass where there is exposed camping. (copied from duplicate entry by @Yarmoss)

Note: Described in the reverse direction to your journey

Pick up the footpad west of the tarn and climb the spur to the large cairn, 1.2km from the pass. Leave the spur, descend and negotiate a small shallow depression (outlined on the map by the 1220m & 1240m contours). The route is infrequently marked with cairns but it is a steeply rising sidle across tussock and scree - dangerous in adverse conditions. Aim to approach the marked stream above the 1400m contour and continue to climb (on the TL) to 1500m. You can travel above the tarn or around to it's outlet - both routes rejoin in the lower saddle (1600m). Continue through the saddle and down to the small tarn (close to the left rock wall is easiest) and proceed to the Lake.