Cat pooping outside box, no solution

I've read all the other threads and can't find an answer.

Hi there,
 
I adopted Pickles in January of 2013.  She and her sister/littermate Simone were picked up in a field in Aurora and were a year old at the time.  I also have a neutered male who is 16.
 
I consider Pickles to be semi-feral:  it took about a year for her to approach me for petting and I still cannot reach out to her with two hands. 
 
Both Pickles & Simone were litter-box trained.  I kept them indoors for about six months then allowed them indoor/outdoor access.  They are trained to come when I call them inside for dinner and I keep them locked indoors at night.
 
I live in a single story home with an unfinished basement.  I had three litter boxes in the basement and feed them in the kitchen. 
 
Everything was fine until about 9 months ago when Pickles began to poop on the floor in the basement instead of in a litter box.  I had her checked out at the vet, she is fine.  I did not change their food or litter and there were no dramatic changes this past winter in my life or our household.
 

I researched online and tried four litterboxes, three different kinds of litter in varying amounts and varying depths of litter.  None of the boxes is covered.  Recently I got a large flat plastic storage bin, eliminated the liner and put only a very fine layer of unscented litter so I now have five litter boxes in the basement and she is still pooping on the floor next to the litter box.  It doesn't matter where I put a litter box or what is in it, she poops on the floor next to the box so she has pooped all over the basement.  I added a calming cat pheromone plug in to the basement about two months ago. 

 I am sure this is a behavioral issue but I am at my wit's end.  I have been dealing with this for 9 months; it's disgusting, unhygienic, and frustrating.  There were no dramatic changes this past winter in my life or our household.
I don't want to force her to be an outdoor only cat but I see no alternative.  Please help me!

I am sorry you are going through this.  Have you tried burying the poop back in the litter so that the cats gets the scent in the box?

Also can you try moving the box to a new location?  Is there any chance the cat is being ambushed when trying to potty and is afraid of the litter box?  Maybe try putting a litter box upstairs in a different location. 

Have you tried a feliway diffuser? 

Have you seen the Jackson Galaxy videos on litter box issues?  If not I would be happy to post them for you.

I have not put the poop back into the box.  I scoop every day and thought keeping poop out was more important but I will try that!

I have moved the five boxes around in the basement and location doesn't make a difference.  I have not tried upstairs because I really really really don't want feces in the main living areas in my house if she still avoids the litter box.  If I try that route wouldn't I have to completely shut off the basement and force her and my other two cats to find the box upstairs?  Otherwise she might still choose to go downstairs and poop on the floor.  I'm worried that might be too much of a change and cause problems with all three cats.  Thoughts?

I did use a diffuser and I have not heard of the galaxy video so a link would be great.

This is so difficult.  I've also reached out to our local cat rescue to see if they have a behaviorist I can hire to come assess the situation. 

Here are two videos and an article

http://www.thecatsite.com/a/how-to-solve-litterbox-problems-in-cats-the-ultimate-guide

SUCCESS!!!

I used a paint scraper to scrape off any existing poo from the cement floor.

I used an oxi-based cleanser and let it soak all over the cement where she's been pooing.

I wiped that up with paper towels.

Then soaked the floor again with a mixture of 50/50 white vinegar & water.

Wiped that all up with paper towels.

Sprinkled baking soda over the floor, let that sit.

Swept it all up.

Purchased some cheap large area rugs at Grocery outlet and put them in the worst-hit areas.

Re--positioned three litter boxes with liners and two un-lined large flat plastic storage bins around the basement so they are all private.

Put Cat Attract litter in three of the boxes including the two unlined storage bins, left the other two litter boxes with my regular litter (World's Best).

There have been ZERO mistakes in three nights! 

Such good news!!  I wish continued success!!!

Fantastic! I'm glad that things are going well.

It's always wonderful when you figure out what works for you! I had a non-user of the litterbox and it took some persistence, some anxiety medication, and diet changes, but now he uses it full time!