Water ~ Testing your chemistry... Mystery Cache

When all the numbers come together you will find yourself on the world famous beach from which the trademark Table Mountain photographs are taken! And if there is any wind (highly probable) you may also be treated to a display by some of the world best kitesurfers! The beach is indeed also renowned as one of the top five best kitesurfing destinations in the world!

After having started kitesurfing in 2000, I became aware of darker patch of water a few hundred meters directly out to sea off the coast of where the cache is hidden. Some days the dark water would be there, and on other days not. Sometimes it would be accompanied by the smell of diesel fumes. It was only recently, however, that I discovered the reason behind this phenomenon ~ A waste water, or "outfall" pipeline, which runs from the Caltex Refinery many kilometers away!

Caltex (now Chevron) refinery was built in the late sixties by the apartheid government to refine crude oil and store it. It is now a key producer of gasoline, diesel and aviation fuel, kerosene and fuel oil. The plant is, however, also source of much, as I recently discovered, water pollution! The outfall pipe which leaves the refinery comes from the new water treatment plant on the western border of complex - From here the pipe makes its way to Blaauwberg Road, under the bridge over the Diep River, then heads all the way down to the circle at the ocean end of Blaauwberg Rd. Apparently the pipe had to modified near Bayside Center during the construction of the new IRT bus terminal. The pipe continues and enters the sea under the storm water pipe just off the circle. At a depth of 10m and 550m out to sea, the pipe opens into Table Bay (See published location)

As Chevron has not responded to even one of my numerous emails requesting more information on the outfall pipeline, I can only hypothesize to the contents of the waste it carries. So hypothesize I did, and just to make things fun, from this moment forth you are an employee at Caltex refinery, Milnerton...

Having recently received your chemical engineering qualification, it is your responsibility as the newly appointed outfall quality control officer to monitor the contents of that which is pumped down the outfall and into Table Bay. In the 1L outfall sample today, among other things, 134µg mercury(II) nitrate has been found. In order to extract the mercury which is in solution, you will add sodium sulphide. The ensuing reaction will allow the mercury to precipitate out as a solid. To ensure that all the mercury has been extracted, what mass (in grams) of that which precipitates out must be collected from 16kL of outfall water? First four real numbers are ABCD.

Remember that mercury is a highly toxic heavy metal, and thus you will not round off after any of your calculations and will use the latest IUPAC table of molecular masses! (Table of Molecular Masses)

Having proven yourself a diligent scientist your are asked if you would consider accepting a position in Chevron’s research division, looking specifically at alternative energy sources. Although not considered alternative these days, you are asked by the HOD to describe the process of uranium enrichment exploiting the differences in rate of diffusion between the various isotopes of uranium based on their molecular masses. Thereafter he request that you, using the equipment in the lab, produce 2g of 100% (highest possible grade - in theory) uranium-235 isotope. Given to you is a uranium sample containing 5g of uranium-235 and the balance uranium-238. The sample has, conveniently, been processed and given to you as gaseous uranium hexafluoride (UF6).

In the lab there is a cylindrical diffusion chamber used for purification of gassed based on their different molecular masses. The uranium hexafluoride gas will be released into the cylinder at one end and allowed to diffuse along the length of the cylinder after which you are able to insert a divider and selectively extract only the contents of the cylinder in the section which holds the desired isotope. How may passes through the diffuser will be required before 2g of uranium-235 will have been collected? (Assume that you are able to capture and remove from the chamber 100% of the U-235 which has diffused past the divider after each pass through the diffusion chamber; Do not round off your workings; Use molecular masses as for previous problem (see link above); Answer will yield EFG) Best of luck in your career as a chemical engineer!

Oh yes the cache... You know where the outfall lies. The cache is (B*AGG)+(CD*F)-5 meters from the outfall at bearing... (first read request below)

Please please please I make this special request to all Geocachers --- When you find the cache you will know it. Do not attempt to retrieve the cache during the day! NIGHT TIME CACHE ONLY! Log your find and return when the beach is deserted to retrieve the cache and sign the logbook. The cache WILL BE MUGGLED if retrieved during the day. THEY ARE EVERYWHERE! I have experienced this multiple times while setting up the cache. It is EXTREMELY VULNERABLE and relies on Geocachers employing stealth - call it part of the challenge :)

...at bearing [(B+C)squared]+F+0.F94 degrees from the outfall ;)

Some extra info and suggestions: In the cache are some instructions written on a round disc - read these... You will see why!

Kitesurfing around the ship is one of my favorite things to do, and I absolutely love this beach! Take off your shoes, dig toes in the sand and enjoy it! ;) This will make finding the caching much more pleasurable. ;)

Lastly, and need I say it... Make SURE you are not observed, and cover the cache in exactly the same way you found it! We don't want people wrecking the dunes! Also let's leave no clues in the logs! This one has been designed to be challenging ;)

Hope you all enjoy my first cache! If any problems arise email me @ doceave@gmail.com

Many thanks to MnCo for suggesting addition of a geochecker! This one will confirm final coords within 10m of the cache

Congratulations to Uffhaus2 on snatching an amazingly quick FTF!