The fact of legal separation will not eliminate and will not reduce the debt.
Generally - each spouse may file a separate tax return without legal separation and without separation - in this case - tax liability will be separated.
Please be aware that because California is a community property state - a spouse's wages, earnings, and net profits from a sole proprietorship are community income and must be evenly split.
Community property laws may not apply to an item of community income that you received but did not treat as community income. You are responsible for reporting all of that income item if:
You treat the item as if only you are entitled to the income, and
You do not notify your spouse of the nature and amount of the income by the due date for filing the return (including extensions).
The legal separation agreement may address issues with splitting community income items and provide legal ground for reporting income on separate tax returns.
By separating the tax liability - each spouse will be liable only for his/her part of taxable income.
You are not responsible for the tax relating to an item of community income if all the following conditions exist.
You did not file a joint return for the tax year.
You did not include an item of community income in gross income.
The item of community income you did not include is one of the following:
Wages, salaries, and other compensation your spouse (or former spouse) received for services he or she performed as an employee.
Income your spouse (or former spouse) derived from a trade or business he or she operated as a sole proprietor.
Your spouse's (or former spouse's) distributive share of partnership income.
Income from your spouse's (or former spouse's) separate property (other than income described in (a), (b), or (c)). Use the appropriate community property law to determine what is separate property.
Any other income that belongs to your spouse (or former spouse) under community property law.
You establish that you did not know of, and had no reason to know of, that community income.
Under all facts and circumstances, it would not be fair to include the item of community income in your gross income.
For information on how and when to request relief from liabilities arising from community property laws, see Community Property Laws in Publication 971 - http://www.irs.gov/pub/irs-pdf/p971.pdf
Let me know if you need any help.