Pipeline Odyssey Multi-Cache

To ensure sufficient water supply, Singapore imports water from Malaysia via water piping running across the Johor–Singapore Causeway. The Pipeline Trail traces the passage of these pipelines from Woodlands to Bukit Timah Nature Reserve. From there the pipes continue underground, and may end at Pearl's Hill Reservoir at Chinatown.

Popular among hikers for the challenging terrain and distance, several hiking groups regularly organize hikes across the trail with large groups of people. Certain parts of the trail are very close to military training areas, but as long as you stick to the trail it is perfectly fine to hike along it. The waypoints of this multi-cache are simpler and lesser in number so you can focus on the hike.

Some things to know about this multi-cache:

1. The total length of this trail is around 8 to 9 km. On foot, that should take about 3 to 4 hours in total. Split the trail into multiple days if you need to.
2. You can't bring bikes on various parts of this trail, sorry.
3. The earlier parts of the multi-cache are only opened from 7am to 7pm, so please do this cache in the day.
4. Bring plenty of water, 2 bottles preferably.
5. Wear covered shoes/boots, some parts may be a little muddy.
6. A flashlight is highly recommended, phone lights are probably enough but you can see more with a flashlight.
7. Bring a partner if you can. There are some parts where a bad slip can turn bad.
8. It is probably a good idea to bring along a face mask. Some people may find the GZ rather unhygienic.
9. Most of the waypoints have alternative solutions in case the original solution is unavailable. Highlight the black bars to see them.

NEW: Only 6 out of the 8 waypoints are needed for the coordinates, just in case some of them are unavailable. See bottom of listing for details.

WP1: Start of Trail
N 1° 21.192' E 103° 47.041'

We start the trail at the Belukar Track within Bukit Timah Nature Reserve. The easiest way to the start of the trail is through Rifle Range Road via drop-off or on foot (watch out for traffic!). Go towards the shaft covers circled in red and look at the small square one.

Let A be the number covered by the red rectangle.
(A is an odd number)

Alternative: https://i.imgur.com/SGAv9bt.jpg
Go to this rectangular cover and get the number covered by the red rectangle. Multiply the number by 2 and subtract 1 from it to get A.

WP2: Yellow Posts
N 1° 21.592' E 103° 46.830'

You will find a group of yellow posts linked by a rusty chain here. Count the number of yellow posts. Don't miss the ones hidden in the trees, as well as the one laying on the grass sideways! You may want to check out the alternative method to make sure your number is correct

Let B be the number of yellow posts.
(B is an odd number)

Alternative: https://i.imgur.com/MuXRRGg.jpg
Go the the nearest set of shaft covers to the yellow posts, and read the markings on one of the small round ones (there are 2 there and their markings should be the same. Get the 2-digit number covered by the red square and subtract 3 from it to get B.

WP3: Lamp Post 69
N 1° 21.920' E 103° 46.717'

At this waypoint we exit Bukit Timah Nature Reserve and enters Zhenghua Nature Park, a park which serves as a green buffer for the Central Catchment Nature Reserve.

Zhenghua was the initial name of Bukit Panjang new town when it was built before it was eventually renamed to the original name of the area. It is the Pinyinised version of "Cheng Hwa", which was derived from the old road Jalan Cheng Hwa, which in turn was probably named after the old Cheng Hwa Chinese School.

You should find an openable gate at the waypoint as shown in the photo. This gate is to prevent wildlife within the park from going onto roads/residental places. After crossing the gate, look for a lamp post with the funny number 69 on it and look at the label on it (which is upside down for some reason, part of a joke or just a mistake?)

Let C be the number-equivalent of the month covered by the red circle.
(January = 1, Feburary = 2, etc)

Alternative: https://i.imgur.com/AH09RLy.jpg
Look for the red sign just after the gate and get the number covered by the blue rectangle. Multiply the number by 2 and subtract 1 from it to get C.

From here you can continue on the Pipeline Trail or walk on the paved path in Zhenghua Nature Park. Or you can take a bus if you are tired of walking, there is a lot more coming. 

WP4: Chestnut Tower
N 1° 22.686' E 103° 46.703'

A short detour into Chestnut Nature Park and up the observation tower. You can enter Chestnut Nature Park by going under BKE at N01° 22.614' E103° 46.595'. There was a cache here that fell victim to the "Great Archiving"...

At the top of the tower, look for what is in the photo above and find the hidden number. There is a pair of the object but both of them carry the same number.

Let D be the two-digit number covered by the green circle.
(D is an odd number)

WP5: Upper Zhenghua Nature Park
N 1° 23.095' E 103° 46.458'

There is a toilet within the park nearby and you should probably relieve youself before going further. You will be out of civilisation of a while.

At the wooden stairs at the coordinates, find the company's name on the lights attached to the railings as shown in the photo above. The first and last letters of the company's name are the same.

Let E be the number form of the first/last letter of the company's name.
(a = 1, b = 2, c = 3, etc)

WP6: Prohibited Road
N 1° 24.163' E 103° 46.412'

You should come across a paved road coming from the prohibited area. Follow the road below the highway and look for the stairs in the photo above at the coordinates. Go to the shaft cover at the top of the stairs and read the markings.

Let F be the number covered by the red rectangle.

Alternative: https://i.imgur.com/ZYT9PlF.jpg
At N 1° 24.101' E 103° 46.363', you should be able to find a hard to see flight of stairs. Climb up the stairs till you hit a dead end and inspect the electric boxes/water meters (?) there. These stairs are very slippery! Move slowly and carefully especially when going down the stairs.There are four of these locked boxes there. All four share the same digit between "B" and "S'. Get the number covered by the green circle and add 3 to it to get F.

WP7: The Climb After the Road
N 1° 24.604' E 103° 46.368'

You are going to have to cross the road here, there are traffic lights to the left. After crossing the road, go to the shaft cover on the hill's slope depicted on the photo above.

Let G be the number formed by the last 2 digits of the year found on the shaft cover.
(the first 2 digits are "19")

Alternative: https://i.imgur.com/7HyhTVA.jpg
Go to lamp post 100 and get the 2-digit number covered by the red rectangle. Add 19 to it to get G.

WP7: After the Pipe Crossing
N 1° 25.011' E 103° 46.319'

Another set of exposed pipes marks the final waypoint. You used to be able to walk across the pipes, but now you can no longer do it. You can go left/right around the fences, go right to find a bridge across the water stream. If you are hardcore you can try the left route where you either have to ford the stream or shimmy past on the fences (which was what I did, since I didn't find the bridge on the other side at first).

Find the small rectangle shaft cover at the bottom of the photo above.

Let H be the number formed by the last 2 digits of the year found on the shaft cover.
(the first 2 digits are "19")

Alternative: https://i.imgur.com/VoWK7E1.jpg
Find the larger square shaft cover next to the one in the photo above and get the 3-digit number covered by the red rectangle. Subtract 34 from it to get H.

The Cache
N 1° 25.XXX' E 103° 46.YYY'

To get XXX, add 202 to the first 3 digits of (A*B*C*D*E*F*G*H).
To get YYY, add 59 to the next 3 digits of (A*B*C*D*E*F*G*H).

The hint for the cache location is within the geochecker:

If there is any problems with any of the waypoints, please inform me and I shall try to provide the solution as soon as I can. The features along the trail seem to change quite a bit over the years, but I will try my best.

Alternate means of deriving the coordinates (in case one/two WP are unavailable):

1. Go to: https://asecuritysite.com/encryption/shamir_decode

2. Paste these into "Secret shares":

0{A}qL5MdwPYMylDuxt1C59FaqgALzpOJmOfXXceCg==
0{B*2}SVpl55cl/1QJbmo15C50NLc/NhCnl4M+/M0iBg==
0{C}ragVoMlHENRMIvnKHWT7pnX4Fum/wEK9fF5ehg==
0{D}R5QWlwnL5giDVRN3DLlMH7NUjp2a62VsWYkRjA==
0{E*3}HwCjnBnqC5C/OD3BzdrmpO0eck22Sa6tzLZtEg==
0{F*4}Lzz1WO6kiooBaC8UE/bTCEj+yKqUVYdQLJtr9Q==
0{G}ly2iRjVO5pDOzB9LD3VYonrI+UTzXfZwro+GYg==
0{H}T3XumUUkpAVZ/I3EVjJWkBG3BVCVzUDB5aMEgQ==

4. Replace the letters in curly brackets with the solutions from the WPs and remove the curly brackets. Do any maths within the curly brackets. If the result only has 1 digit add a "0" before it.
For instance: if B = 3, replace "0{B*2}SVpl55cl/1QJbmo15C50NLc/NhCnl4M+/M0iBg==" with "006SVpl55cl/1QJbmo15C50NLc/NhCnl4M+/M0iBg==".

5. Omit any lines with values you do not know. Only 6 lines are needed. Make sure there are no blank lines.

6. Press "Determine" and scroll to the bottom of "Reconstructed" for the coordinates!

Please use this only as a backup in case 1/2 of the WPs are unavailable!