From the start follow the shoreline to the pipes and a pile of trash tucked away in a corner.










*Bonus (doesn't count as secret): jump the pipes and go forward to find an interactable doll.










**Bonus: following the correct path you'll stumble upon more pipes, nearby you can find a seagull (that flies away if you get too close) - kill it to spawn some more trouble.

After picking up the shotgun, instead of following the path uphill, walk to the end of the beach and get inside the shipping container. Picking up health pop spawns gnaar in front and behind you.

Up the hill, on the second old pier - some armor.

Not far from the armor pier, to the right of a roadside lodge, a hole in the ground covered by wood. Break the wood and jump down.

Near the first oil rig road splits, follow the right path to a blue shack, deal with foes and continue to the right to end of the canyon.
NOTE: KEEP AT LEAST ONE C4 BRICK TILL THE END OF THE LEVEL

At the end of the secondary mission right by the skill point box.

From rig 1 follow the secondary objective path to rig 2. You can finish the objective first or collect secrets and return to it after. Next secret is to the left of the rig 2 (facing it from rig 1). On the left side you'll find another cliffside group of huts with another pier with another armor piece. Beware the werebull that spawns behind you on armor pickup. Easily avoidable by kiting it to one side and then dodging to the other.

From the pier, go left, to a lonely tree under which you will find yet another health pop. Guess what picking it up does. Your reward is 2 major biomechs. What a classic.

Facing the tree from the direction you came from, go right, in between edge of the map minefield and oil rig, to another lone hut. Behind it a pack of rockets.

*Bonus: in the oil rig's 2 "moat" on top of a burned car is a medium medkit.

A bit later in the level a group of gnaars will jump out of a ventilation shaft. Another secret is inside of it. Follow the path until catwalks from which you'll have to jump into the hole. It will probably take you a few tries as this hole seems to be made so you can't stand in there, you need to jump in in a way so you slide in and not out. This secret probably needs a SEISURE WARNING lol. By the end of it you'll be rewarded with your first L.I.F.E.

Another L.I.F.E. after the "fire corridor". Clear out the yard and walk up the square thing first reptiloid spawned on, go up the stairs, into the building, across the corridor, into the nook.

In the room with the objective button.





















*Bonus: there are a couple or more of weird books around the game. Here's first one I found. Not a real book and is a Talos Principle reference[stratonofstageira.wordpress.com]. Here's an interesting steam discussion thread about him.


**Bonus: the attention to detail in the environments is pretty good in this one. Some posters and super detailed postings around the place.





















First is the funniest one: "Attention. Smoking and swearing in only allowed in specifically designated areas."




Next one is "Storm Bringer company policies in the field of labor protection and work safety. General points. As part of ensuring labor safety at work employees and managers should fully familiarize themselves with the following documents:" which is a followed by a whole list of boring sounding legal documents with a few funny bits like "Guidelines for complying with rules and regulations during alien invasion" and "acts on the lack of monetary compensation to employees affected by the bureaucratic machine" or "Guidelines for weekly checkup of kitties living on the territory of the facility" and "Procedure for issuing bonuses to employees that managed to readtill this point" (yay!) and "Procedure for issuing bonuses to the poor sob that was writing all of this" and finally - the punchline - "and other paper waste". Lovely.


And the fourth one is "Recommendations and Rules for Company Employees in Case of Alien Invasion" which is a lot of funny and questionably funny points. Way too much to translate. Maybe later. Thanks to @Little Fox we now have a translation:
"In case of appearance of unidentified personnel in the facility clearly, supposedly or indirectly of alien and/or inexplicably irrational origin, the Storm Bringer company management team strongly advises all employees to adhere to following rules and instructions:
- Do not panic. It's not the first (and, let's hope for the best, not the last) time our country is under attack. It will manage;
- Do not scatter. Gather up in groups of 3-4 people and try to secure a temporary shelter, where you will be safe;
- Do not approach personnel of alien origin with the intention of touching, smelling, taking a photo, getting them drunk, loaning cash, starting a fight in the name of the great justice, performing sexual acts with individuals of seemingly attractive appearance or just on a bet;
- Arm yourself with appliances suited to protect yourself against personnel of alien origin in case of unexpected close encounter of second or third kind of Hynek's scale;
- In case if close encounter of second or third kind is unavoidable, carefully evaluate all possible risks and make sure, that you are able to fight the aliens with what weapons you have;
- It's recommended against trying to stab or fist fight personnel of alien and/or unidentified origin, when they exceed your size times two, are armed with long range weapons or scream AAAAAAAA without a head;
- It is recommended against trying to take down flying personnel of alien origin by throwing rocks or bottles from the ground;
- It is recommended against trying to scare away personnel of alien origin present in the facility, using strong language and primitive threats;
- Contact the company's security. It is their job."

Right outside the elevator there's a train in front of you, on the other side of it is a pack of rockets.

In the same trains area. Past the exit by the right hand side there's a concrete block you can squeeze by.

*Bonus: under the elevator you'll have to take a bit later there's a small armor piece and on the top floor some shotgun shells above the elevator door.

**Bonus: speaking of elevators - the sign inside of the elevator.
Some info on the elevator, then "Date of commissioning: 2046. Lifespan - 50 years. Date of next maintenance checkup: 2106" yeap, that's russia alright. Mildly amusing user manual "1. To call the elevator, press the elevator call button. 2. Wait till the elevator doors are open. 3. Make sure that elevator is in front of you". 4. After entering the elevator press up or down button. 5. Wait for the elevator doors to close. 6. Wait until elevator stops moving. 7. In case of elevator malfunction call the dispatch." mildly funny but not the best part. "Prohibited. 1. To attempt repair malfunctioning elevator. 2. Attempt to get out of the malfunctioning elevator. 3. Enter the elevator shaft. 4. If you are playing in co-op, portal is located at the bottom part of the elevator shaft. 5. If you are playing solo there will be no portal, you'll have to call the elevator back.

Nothing particularly funny on the board up the elevator except for one paper: "I, Sidorov P.I., refuse to fulfil my duties to compile these stupid documents. They serve no purpose. This is just more of bureaucratic paper waste. The planet is invaded by aliens, ALIENS, that want to kill us all and I have to type these moronic orders and directives. We must abandon this facility! Leave everything and run. Siberia is big, plenty space for all, they won't find everyone.Cutting short, do whatever you want, but I'm out.". Neat little piece of world building.

After the AK pickup, under the pipes/catwalks, follow pipes on the ground into the red hole where you will find another C4 brick.

After fighting snipers and scrapjacks, behind the white storage room with jump pads.

After the jump-pads room, right after exiting, jump on the box on your left and on the little roof above the door.

From the jump-room exit, to the left is exit from the level, don't go there yet, instead follow the path to the right, in the end some boxes by the wall, break the boxes. Behind - a spot for C4. Self-explanatory.

DO NOT SHOOT THE CHICKEN-WALKER IN FRONT OF YOU IF YOU WANT THIS ACHIEVEMENT
To unlock it, make your way to the crane, pick up a container (mechanoid will wake up) and drop it onto the enemy.

From the start go right to the dead end with some pipes, do some of that iconic SS parkour and be rewarded with yet another L.I.F.E.

On the box in between catwalks you use to cross the gap and the catwalks that lead to crane controls.

After crossing railway paths to the other side, drop down the second path and follow the rails to a shipping container with a big armor pickup inside.

At the far end of the secondary objective yard, behind some tanks and crates.
NOTE: KEEP 2 BRICKS OF C4 TILL THE END OF THE LEVEL

Following the progression of the secondary objective, in the second yard you can get into storage 02. Behind the shelves.

Courtesy of @vt-dbnz.

In the yard with secret 2.4, on the other end, in a corner blocked by a concrete separator on the building wall is a switch that opens door 06.

Continue on the secondary objective path, follow the road until you can make a left turn around the rocks, follow the rocks line until it ends and take another left into the woods to some shack with a cute looking snowman. The secret is on its head. Obviously when you pick up the health snowman explodes dealing quite some damage. Not sure if can be avoided Was two of these not enough?

Courtesy of @Cham-Cham apparently you can just shoot the snowman.

*Bonus: from this secret follow the path to the corner of this area, in between facility wall and rock wall, in a turned over dumpster - a non-secret big pack of shells.

**Bonus: just in case you'll miss it - if instead of taking first left you take right, behind the container/shack you'll find rockets and some armor.

Follow the objective and turn on the power. After getting out of the pit, go behind the power station and into the now unlocked excessively long basement, which is like that just so devs can be @-holes again. Prepare your super shotgun asit one shots werebulls if you are dead on and very very close. Which you will be in this confined space.

*Bonus: at the end of sidequest - another weirdly specific book. Not real. Just a "justin case - just in case" meme?

Back to the main path. Get to the "Extremely Uncool". On that arena, behind a concrete barrier, some armor.

Some helicopter and scrapjacks later you'll come upon an open gate by some shipping containers by the right side. Prize is behind those containers.

*Bonus: on the other side of the channel some armor behind concrete blocks.

Right out of the last secret, look down the edge right across from the hole you crawled out of. Jump down and then once more down the middle of the platform. Be ready for a fight. Those...things take 2 SS shots (on hard) and don't do AoE, so it's not exactly challenging, just strafe and spam SS.

In the yard with the mech.

Complete the mech section WITHOUT SHOOTING A SINGLE SHOT. NO LEFT CLICKING.
AND you have to chop down every big enemy (scrapjacks, chicken-walkers, arachnoids, khnum, helicopters), not too hard but there are THREE Polyp-Copters (two at the first secion, one more at the end) and you might miss one.

After your "factory equipment" runs out of juice. Tucked away in a corner behind some shipping containers, a brick of C4. This one comes with small arachno-party.

This one is not even that hidden but requires 2 bricks of C4. Near the previous arena exit/this area entrance.
Inside if you are not familiar with classic secrets, in the second room take left in the dark corridor and in the weird letters room you have to spell the name of the big bad by jumping on letters - M-E-N-T-A-L (jump from T to A is pretty tight).

This took a while.

I'm not sure how exactly this one is a secret, as no parts of it are exactly hidden, but by collecting 3 key cards in the first part of the level you can get a skill point in the hut between parts 1 and 2.
This covers the entire first area, or rather - entire first area is exists just for those key cards cause if you don't collect keys and secrets you can just b-line to the exit. I'll split this one into parts and put them in appropriate "sequential" order. And also numbered it as the last secret of section to make cross-checking with the guide less confusing. "I'm about to leave the area and I just picked up secret 8 but stats say I only have 7? Did I miss one?"

*Bonus: solved puzzles if someone needs it.

1.

2.

3.

In the field of pumps closer to the beginning, you might notice that 3 pumps are not working. Press the button on the side of each one and enjoy this games new twist on an old enemy.

To find first key just follow the yellow gas pipe you've been riding along since you got snowmobile. Big outpost has a secret behind the other building.

In the aforementioned big outpost with a keycard, go behind the building on the right and jump into a group of cube barrels.

For the next key ride through the outpost till the crossroads and take left. Small outpost is by the right hand side after a yellow pipe arch.

In the "Hide and Seek" side quest area. Pretty much unmissable. When you reach an ominous looking formation of rocks on the left side is a clearly visible blinking pink gadget. Take hard left around this rock and hug it until you come upon a totem-marked cliff-rock. Climb it to reach the gadget.

*Bonus: at the side quest objective there's a hole in the ice, down which you can find a hateful friend from the past electro-fish. Not sure if there's anything else because just to even see the thing I had to spam L.I.F.E.s and even that doesn't give much time in the icy water.

Backtrack to the crossroads (maybe do the "Hide and Seek" first) and take the last, sawmill, path. Right after crossroads there's a secret on the left and you'll pass by sawmill that has another secret. Ride until you make a hard right turn. By the left there's another secret and by the right is last outpost with a key. Following the same road will lead you back to oil pumps and the area exit with your prize.

Near the aforementioned crossroads in between key card outpost and "Hide and Seek" entrance. Follow the Sawmill road till you see a yellow pipe arch. Into that arch and to the old cart with a hole in the ground nearby. Secret is in the hole. Who is this Dmitry and how is he still alive?

Inside of the cellar secret.

Finally, some good f***ing food secret that was fun to find. Following the sawmill road you'll discover the...sawmill, who could've thought. Jump on the tractor by the sawmill building, then on the roof, from the roof jump on the tank connected by the pipe to the silo thing, follow the pipe, climb the ladder and get your C4.

Follow the same road until a right turn. After the turn, to the left you can find an alien pump thing. Under it are remnants of a brave resistance member who clearly put up some fight before going down. He left us a SS and a T.A.C.T. gadget.

Back to the pumps field. Closer to far end you can find a big rock formation. It has path to the top of it. There you'll find a hoverboard gadget.

*Bonus: across the road from this secret you can find a path in the snow leading to a cliff edge where octanian soldier is just enjoying the moment.
Courtesy of @Dinosaurs(1991) is best show - destroy the radio for a non-secret secret L.I.F.E.

The reward for this key hunt awaits you in the checkpoint you have to go through at the end of the area. Exit the building, go left and back into the building through side door.

*Bonus: as you enter the village, turn around the first house on the left and check the open window.

In the room with the "secret" skill point.

After emerging on the other side of the church, go down the steps, follow the road but don't take right turn, go a bit forward and check out the big angel-in-an-arch statue on the left.

On the approach to the village make a left turn by the electrical box into the woods. There you will find a shrine in memory of Cortana Netricsa who I didn't know is dead? Or not "born" yet? Or never existed because she was part of a dream? Yes...it's a bit complicated.

At around 3100m till the objective, after exiting the village through another gas pipe arch you'll come upon a fork. Take right to a barn with a tractor in it, check the little shack on the left.

Back to the fork, a bit towards the objective (about 3000m left) by the right side you can find an empty field with a giant medkit. And of course it's another trap.

In the woods to the left of the destroyed church.
*Bonus: non-secret L.I.F.E. inside of the church.

Upon making it to the alien bridge check under it.

Follow the bridge moat towards the objective. At the end of it is a sewer pipe. Navigate right, left, right and behind the machinery in front of you is a button. You probably already noticed the door it opens in the previous corridor.
And again, if you are not familiar withclassic secrets: 1.For funzies you can try jumping over the guardrails of the slide for a joke secret (not an actual secret) and 2. The wall opposite to the one that gets broken by the bull is breakable too and contains some cannon balls (again - not an actual secret).

Instead of bothering with the bridge puzzle put a rocket into the screen.

To the side of the objective barn there's a formation of rocks. Through the entrance behind trees, T.A.C.T. awaits.

Behind the objective barn, a wooden shack, behind the shack - some BFG ammo.

Can be done with any of the tentacle-towers. You need to use ONLY hoverboards firepower to destroy one. Do not shoot it with anything else.

Another multi-parter that starts in the area after alien bridge. 3 out of 4 parts are unmissable, 1 is just slightly out of the way.
First tower is right down the road from the bridge. Destroy it to get the key.

From the first tentacle tower (one straight down the road from the bridge) there's a silo/tower in the middle of the field. Impossible to miss. Atop - some supplies and an easter egg.

Second tower is to the right from the alien gate. Somewhat heavily guarded.

On your way from or to tower 2 there's a wooden hut, in a corner behind it and a stone fence, a hoverboard.

In one of the huts past the alien gate, near the row of silos.

Progressing through level, after the alien gate out of the 2 tentacle towers area, you'll come upon a group of houses with a row of silos. To the left of it is an alien outpost. With a locked gate. Penetrate the defences from behind. One of metal rooms contains the secret gadget. Also inside - a cuteTalos Principleeaster egg.

*Bonus: in this aforementioned group of houses you can swap your ATV for a tractor.

Following the road you come upon a windmill, follow the winding path down and at the bottom take hard right to the river. And who could've expected that one - there's a secret behind a waterfall. Be ready for a fight.

Last tower is, again, impossible to miss. In the valley of windmills.

Following the objective through the big open area, to the right of the 3rd tentacle tower is a path to a shack and some broken pier/dam/bridge something. Under that are some supplies.

Past the last tower and the nearby rock you can see a windmill by the river. Get inside of it, look up, shoot the wooden boards cannon lies on. Big balls time.

On the beach by the objective bridge you can find remnants of a hut. Inside - some cannon ammo.

Under the objective bridge. Prepare to die.

On the objective bridge there are train carts. Last cart before the concrete barriers has an open door.

You will not miss it. Case is by the level exit.

Right under the starting bridge.

Following the objective marker, just about as open fields starts, in the rock formation on the left there's a fairly obvious opening. This thing regenerates. You have to dump as much damage on it as fast as you can. Spamming 5 rockets, cannon. Or just TACT it. That works.

*Bonus: in the remnants of a village right before this secret :D

On top of the tankshack.

Don't get into the tank and beat the next section using guns and gadgets. Would not recommend on anything above tourist.

After the fun ride is over pass through the alien gates and go around the first shack, behind the house is a wood covered hole in the ground.

In the first sidequest bunker room, on a box.

In the side objective area. In the bunker, after you pass a red light corridor full of processed, turn into a small storage room on the right, destroy the boxes and dive into the hole.
As for the puzzle, I can't give a solution if you want to solve it yourself I can give you this somewhat helpful chart. And here's a solution: according to the chart 7-5-6-2

Following the side objective you'll arrive at an open pipe to the right. Instead of diving in, keep going forward to the end of the corridor. Press the elevator button.

On a box after climbing up the ladder out of sewers.

Right after the "half-life on steroids" elevator ride. Go through the "refill" corridor and in the second room use the light to jump over the fence.

Following the main objective, after the cutscene you'll find yourself standing near a guitar. Interact with it a...few time. You'll know when it's enough.
The face that appears in the sky is the Croteam's composer Damjan Mravunac btw.
Btw - leave a comment if you recognize any of the song bits played by the guitar.

After you get a new toy and hear an awful joke, in the same yard where the toy is behind a hut in on the corners.

*Bonus: courtesy of @xdshot. In the "new toy" yard, in the outhouse, another funni book. "A nuked story of that blondie guy". Probably took them forever to write this one. Also authors - I might be wrong but my guess is M. Giantrano is a reference to this guy who humiliates himself by pretending to eat dog food for boomer-shooter youtubers. Oh, and also does some bang-on "Jon St. John gritting his teeth and doing a Dirty Harry impression" aka Duke Nukem impression. F. Kabino is a mystery to me. If someone explains it I'll edit it in.

**Bonus: extra non-secret ammo behind open gates around the corner.

After you make it through a hole in the red wall. Take hard right around brick wall and follow the train carts to cache of ammo covered with boxes.

First opportunity for this achievement arises around here. Just kill any Burner (flying fat alien with lasers) using a laser gun.

On the other side of the train you can find a one story building. Secret is on top of it. Make a jump from stairs on the next building, gadget is behind boxes.

After a fight with processed in a yard. Pass between building an moat, turn right and jump through the gap between truck and cargo container. Drone is, again, behind boxes.

Two secrets in the big open yard with trains. Both are around the same building on the other end from the entrance. First one is on the closer side. Inspect the wall near the corner to find a C4 breach spot.

On the other side of the same building.

After picking up grenade launcher exit the building, immediately turn left and jump over the wall of boxes.

In the last arena where you have to protect the train. Behind the building on the opposite end of the yard.

Stay here and kill them all... with a black hole.
Rather self-explanatory - don't shoot anything, get closer to the crowd and throw black hole into the middle. Might have to use both. If you don't want to "waste" them complete the achievement and just load the autosave.

After you cross the rail tracks and make it to the "УСТИНОВ" building on both left and right are secrets.
On the right - L.I.F.E., electricity and an ambush.

*Bonus: 25 armor in-betwen trains.

On the left - 20 rockets. And an ambush. An ambush that takes 15 rockets to exercise. So, basically, it was only 5 rockets.

Enter the train station and check the open bathroom around the left corner.

In the train station, near minigun.

Exit the building and (after dealing with the hoard of enemies) turn left. Walk by the left side past the next building to find a Hoverboard hidden behind a truck .

Make your way to the nice and cozy post-soviet neighborhood, clear it out of creeps and check the rightmost building. It has an interactable door.

*Bonus: inside of the secret is untranslatable (come on, devs!) announcement on the wall that goes something like:
"Dear residents. Stay vigilant and careful, look up and around, something yet to be understood is happening, but so far no one understands what exactly. Chairman of the HOA."

**Bonus: graffities on the middle building ARE translatable.

In the little open window of the newspapers kiosk you pass by before street leading to gas station/bridge.

Follow the objective until you find yourself in between a gas station and a park entrance. Both have secrets.
Park first. Just enter and follow the right wall to the ammo, that you probably saw earlier through the locked gate.
"But isn't this way too easy?" Sam thought to himself as hoard of kleers started spawning behind him.

*Bonus: this one is such a great meme reference. If you are russian. And know russian memes. Right near the "secret" cache is this poster
which reads "Central concert hall. Ustinov city. March 3rd, 7pm. On the same stage. Legendary Gregory and his friend popular dancer Danzell". Those 2 names are serious sam universe "characters" - multiplayer models that[serioussam.fandom.com] for some reason have lore[serioussam.fandom.com] And the whole thing is a 1:1 reference to this REAL promotional material




And have to make emphasis on "real". This is an example of rather typical for post-soviet space advertisement made by/for dying concert halls in small (and sometimes not so small) post-soviet cities that can only get booked by "literally who?" or "maybe popular 40 years ago and now way past their prime" tier artists. But this one stands out by already looking like a parody - "gRaPhIcAl dEsIgN Is My PaShIoN" design and layout, faces, "literally who" factor and most importantly - names and phrasing. It's impossible to explain but "Zhoka and Boka" just sounds funny in/for russian. And so, hundreds of memes ensued. Now including this one, immortalizing it in a videogame form.






Examples:

Back to the gas station. On the side of it is a tank that you can climb and jump on the roof from.

*Bonus: 2100s twist on mundane 2000s ads. As the memetic one above, this kind of ad is typical for post soviet space - crappy, usually only text poster, usually somewhere nearby the business and in a quantity of only one, advertising a dude with a camera and a printer in a tiny room trying to make a living snapping and printing pics for people in a rush. "Photo studio Anastasia. Open 8-19, Sunday 9-18. Photos for documents, photos on a set (?), photographic development (very relevant in the 22nd century), photo printing, cropping, digital photo editing" and then "holographic printing" and "3D scanning". Neat details.

**Bonus: cool graffiti nearby the gas and another one near the bridge.

At the end of this arena/corridor. Instead of taking the alien bridge continue heading forward. Some supplies under the concrete wall separating you from the start of this arena.
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

Under the destroyed joke bridge.

Here's a great place to complete this one. Proceed by the ice. On the corner pop time warp. Wait for burner to spawn (you can ride an armored hulk meanwhile to not take damage). Pop another warp and catch that burner. ??? Profit.

After chicken-walker breaks the ice (literally not figuratively) go up the hill and across the bridge. Device is in a corner between building and truck.

*Bonus: on your way back don't miss the graffiti exchange on the concrete wall segment. It's a reference to the russian official localization of SS games where the name was changed to "Cool Sam" ("Крутой Сэм") as "Serious" ("серьезный") doesn't roll of the russian tongue as well and doesn't really have the same connotation as in english.

On the other side of the destroyed bridge make your way into the opening and turn left. In the far right corner between fence and building there's a tiny tiny 1hp pop. Before picking it up pre-load rocket launcher with 5 rockets.

*Bonus: a bit further down the path, a "wife bad" joke on a wall. Reference to the flying-crap-throwing Witch-Bride enemy.

After you make your way around the building and exit the yard some enemies will descend to you on an elevator platform. Take right, left onto the ice and then another right, on the little hill, walk to the edge and look down. Two harpies are inspecting? guarding? a hoverboard. Harpies are kinda absent from this game, no? Well, if you missed them - this is a secret for you.

*Bonus: after (or before) the "no ambush" generator room, some non-secret supplies and a L.I.F.E. around the corner. Spawns burners.

Follow the objective till the locked gate. Turn right, notice rusty pipe, follow it.
Be ready for a fight. Those bastards are tougher than normal ones, frost more and faster balls.

Pass through the gate. For the next secret you need to make your way all the way around this rock formation on the right.

After grand-battle. On a bench near first building behind enemy-detecting gate.

The final secret of the is found after the massive showdown. Procced on the objective path. When you hit a fork take right, then left, into the spiral of these 1 story buildings. Last secret awaits in the middle of the spiral, there is an open door. And inside wooden boards are hiding the way.
Beyond the portal you are almost instantly thrown into a fight. Destroy the barrel behind the well-looking-structure for some armor.