Document:

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                                                                   EXHIBIT 10.15

                             LOAN PURCHASE AGREEMENT

This Loan Purchase Agreement dated as of January __, 2000, (the "Agreement") is
made and entered into by and between Humboldt Bank, a California state-chartered
bank ("Purchaser"), and Capitol Thrift & Loan Association, a California
industrial loan corporation ("Seller").

                                    RECITALS

A.       Humboldt Bancorp, Purchaser, Global Bancorp and Seller have entered
         into the Second Restatement of the Agreement and Plan of Reorganization
         dated November 12, 1999 as amended (the "Merger Agreement") which
         provides that Purchaser and Seller will enter into this Agreement.

B.       Seller desires to sell and Purchaser desires to purchase up to $60
         million in loans, all on the terms and subject to the conditions of
         this Agreement.

NOW THEREFORE, the parties to this Agreement hereby agree as follows:

                                    ARTICLE I
                                   DEFINITIONS

         1.1 Definitions. As used in this Agreement, the following terms have
the meanings given below:

             "Agreement" means this loan purchase agreement.

             "Business Day" means a day, other than a Saturday or Sunday, when
Purchaser is open to the public for business.

             "Closing Date" means the date to be chosen by the parties pursuant
to the Second Restatement of the Agreement and Plan of Reorganization dated
November 12, 1999 by and among Humboldt Bancorp, Purchaser, Global Bancorp and
Seller as amended (the "Merger Agreement"), or any other date and time the
closing of the purchase is consummated as contemplated in Articles II and III
and shall be effective as of the close of business on the date of closing.

             "Commissioner" shall mean the California Commissioner of Financial
Institutions.

             "FDIC" means the Federal Deposit Insurance Corporation.

             "Purchased Assets" means (i) the Purchased Loans, and (ii) all
business records relating to the purchased loans and all accounting or financial
information concerning the Purchased Loans to be transferred.

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             "Purchased Loans" means all of Seller's interest, including the
outstanding principal balance due and accrued and unpaid interest and/or late
charges thereon as of the Closing Date, in all loans listed on Schedule 1.1(c),
to be provided within 10 days of the execution hereof, including a two percent
loan loss reserve for each such loan.

             "Regulatory Approvals" means all approvals, permits,
authorizations, waivers, or consents of state and federal governmental agencies
or authorities necessary or appropriate to permit consummation of the
transactions contemplated in this Agreement.

                                   ARTICLE II
                           PURCHASE AND SALE OF ASSETS

         2.1 Closing Date. The closing of the transactions contemplated by this
Agreement shall occur immediately preceding the closing of the merger
transaction contemplated in the Merger Agreement. On the Closing Date, the
closing of the transactions contemplated by this Agreement shall take place at
the head offices of Purchaser in Eureka, California. Notwithstanding anything
herein to the contrary, the effective time for the closing of the transactions
contemplated by this Agreement shall be as of the close of business on the
Closing Date.

         2.2 Purchase and Sale. On the Closing Date, subject to satisfaction or
waiver of the conditions precedent set forth in this Agreement, Seller shall
sell and Purchaser shall buy all the Purchased Assets.

         2.3 Payment for Purchase. As consideration for the Purchased Assets,
Purchaser shall pay Seller the purchase price specified in Section 2.4.

         2.4 Purchase Price. The purchase price for the Purchased Assets shall
be the sum of the following:

             (a) An amount equal to the outstanding principal balance due and
accrued and unpaid interest thereon as of the Closing Date, of the Purchased
Loans; less

             (b) Two percent loan loss reserve for the gross amount of such
loans.

         2.5 Prorations. Seller and Purchaser shall prorate the following items
as of the Closing Date so that all items applicable to all periods through the
Closing Date shall be for the account of Seller and all items applicable to any
period subsequent to the Closing Date shall be for the account of Purchaser:

             (a) Any real or personal taxes, intangibles taxes, or other similar
taxes on the Purchased Assets, in each case prorated on the basis of the taxing
year of each taxing body involved

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(and if the amount of any tax is not ascertainable as of the Closing Date,
proration of the tax shall be based upon the most recent ascertainable tax bill
subject to adjustment when the actual amount becomes known);

         2.6 Taxes, Fees. Taxes and fees shall be allocated and paid as set
forth

             (a) Seller shall be responsible for payment of all taxes attributed
to or associated with the Purchased Assets prior to and on the Closing Date,
including but not limited to, business and occupation taxes;

             (b) Purchaser shall be responsible for taxes and fees attributable
to the operation of the Purchased Assets after the Closing Date;

             (c) On the Closing Date, Purchaser shall pay to Seller sales and
use tax payable by reason of the transaction contemplated by this Agreement;

             (d) Seller shall be responsible for recording fees for recording of
documents to remove liens or encumbrances against any of the Purchased Assets;

             (e) Purchaser shall be responsible for filing and recording fees
and any other expenses incurred in connection with transferring or assigning to
Purchaser the collateral which secures the Purchased Loans; and

             (f) Any other taxes and fees shall be prorated according to the
accepted practice in California for allocation of such items in similar
transactions.

                                   ARTICLE III
                             CLOSING OF TRANSACTIONS

         3.1 Estimate of Consideration: Payment of Estimated Amount. Four
Business Days prior to the Closing Date, Seller shall prepare a reasonably
detailed calculation of estimated amounts of the purchase price to be paid for
the Purchased Assets and the amount to be paid pursuant to Section 2.4. Upon
completion, Seller shall deliver to Purchaser such statement of the estimated
consideration to be paid, certified by the chief financial officer of Seller to
have been prepared under his supervision and to be as accurate an estimate as is
reasonably practicable. On the Closing Date, Purchaser shall, as shown thereon,
pay the estimated net amount due to Seller, if any, in immediately available
funds or in acceptable securities.

         3.2 Determination of Final Amount of Consideration, Payment of Adjusted
Amount.

             (a) Following the Closing Date, Purchaser and Seller shall, as
promptly as reasonably practicable, consult with one another to determine and
agree upon the final calculation of the purchase price for the Purchased Assets
in each case calculated as specified in Article II.

             (b) Within five Business Days of the final determination of the
amount of the Purchase Price, Purchaser shall pay Seller such amount as is
necessary to adjust the estimated

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amount paid on the Closing Date to the actual amount due. Such payment shall be
made in immediately available funds or in acceptable securities, together with
interest thereon at the average daily federal funds rate from the Closing Date
until paid.

         3.3 Other Actions at Closing. Subject to satisfaction or waiver of the
conditions to the respective parties' obligations, the following actions shall
be taken on the Closing Date:

             (a) Consents. Seller shall deliver to Purchaser such executed
consents and approvals of third parties in form and substance reasonably
satisfactory to counsel for Purchaser, as may be required to consummate the
transactions contemplated hereby; provided that Seller shall have no liability
to Purchaser if Seller is unable to procure such consents.

             (b) Bill of Sale. Seller shall deliver to Purchaser an executed
bill or bills of sale, substantially in the form of Exhibit A attached hereto,
transferring and warranting to Purchaser all right, title, and interest in and
to all Purchased Assets.

             (c) Assignment of Contracts and Accounts. Seller shall deliver an
executed assignment or assignments, in a form to be agreed upon by the parties,
transferring and assigning to Purchaser Seller's interest, Contracts, Accounts,
and any other Purchased Assets not otherwise covered by an instrument of
transfer, in each case free and clear of all claims, liens, and encumbrances.

             (d) Possession. Seller shall deliver possession of the Purchased
Assets to Purchaser or its representatives at the close of business on the
Closing Date.

             (e) Other Documents. Purchaser and Seller shall each deliver such
other documents as this Agreement contemplates will be delivered by Purchaser or
Seller, as the case may be, on or before the Closing Date, or as may be
reasonably requested by the other party prior to the Closing Date to consummate
the transactions contemplated hereby, to evidence compliance with such party's
covenants or the accuracy of such party's representations and warranties, or the
satisfaction or waiver of conditions to the other party's obligations hereunder.

         3.4 Further Assurances. From time to time on and after the Closing
Date, as and when requested by Purchaser or Seller, or by their respective
successors and assigns, the parties shall execute and deliver such other
instruments of transfer, assignment, and assumption and shall take or cause to
be taken such further actions as shall be necessary to effect this Agreement.

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                                   ARTICLE IV
                              CONDITIONS PRECEDENT

         4.1 Conditions Precedent to Obligations of Both Parties. The
obligations of the parties to consummate the transactions contemplated by this
Agreement shall be subject to the satisfaction or waiver of each of the
following conditions on or before the Closing Date:

             (a) Regulatory Approvals, in form and substance reasonably
satisfactory to the parties and their counsel, shall have been received from all
federal and state regulatory authorities having jurisdiction over the parties
and the transactions contemplated hereby.

             (b) No action, suit, or proceeding shall have been instituted by
any public authority to restrain, enjoin, or prohibit the transactions
contemplated by this Agreement.

         4.2 Conditions Precedent to Obligations of Purchaser. The obligation of
Purchaser to effect the transactions contemplated by this Agreement is subject
to the satisfaction or waiver of each of the following conditions on or before
the Closing Date:

             (a) All representations and warranties of Seller contained in this
Agreement shall be true and correct in all material respects as of the Closing
Date with the same effect as if such representations and warranties had been
made or given on and as of the Closing Date; all covenants and conditions to be
performed or met by Seller on or prior to the Closing Date shall have been so
performed or met in all material respects; and on the Closing Date, Purchaser
shall have received an officers' certificate, dated as of the Closing Date,
signed by the chief financial officer or another senior executive officer of
Seller, attesting to such facts to the best knowledge of that officer after
reasonable inquiry.

             (b) Except as otherwise provided herein Seller shall have obtained
all consents and approvals which are necessary or advisable in connection with
its consummation of the transactions contemplated hereby and shall have
delivered executed copies thereof to Purchaser.

         4.3 Conditions Precedent to Obligations of Seller. The obligation of
Seller to effect the transactions contemplated by this Agreement is subject to
the satisfaction or waiver of the following condition on or prior to the Closing
Date:

             All representations and warranties of Purchaser contained in this
Agreement shall be true and correct in all material respects as of the Closing
Date with the same effect as if such representations and warranties had been
made or given on and as of the Closing Date; all covenants and conditions to be
performed or met by Purchaser on or prior to the Closing Date shall have been so
performed or met in all material respects; and on the Closing Date, Seller shall
have received an officers' certificate, dated as of the Closing Date, signed by
a senior executive officer of Purchaser, attesting to such facts to the best
knowledge of that officer after reasonable inquiry.

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                                    ARTICLE V
                             WARRANTIES OF PURCHASER

Purchaser represents and warrants to Seller as follows:

         5.1 Organization, Powers, and Qualifications. Purchaser is a
state-chartered bank duly organized, validly existing, and in good standing
under the laws of California. Purchaser has all requisite corporate power and
authority to own and operate its properties and assets and to carry on its
business as now conducted.

         5.2 Execution and Performance of Agreement. Purchaser has all requisite
corporate power and authority to execute, deliver, and perform this Agreement.
The execution, delivery, and performance of this Agreement by Purchaser will not
conflict with any provision of its articles of incorporation or bylaws or with
any undertaking, agreement, decree, order, or judgment by which it is bound.
This Agreement constitutes the valid, legal, and binding obligation of
Purchaser, enforceable against it in accordance with its terms. The execution,
delivery, and performance of this Agreement have been duly and validly
authorized by the board of directors of Purchaser and by Purchaser's sole
shareholder, Humboldt Bancorp. No other corporate proceedings on the part of
Purchaser are necessary to authorize this Agreement on its behalf or the
consummation by it of the transactions contemplated by this Agreement.

                                   ARTICLE VI
                              WARRANTIES OF SELLER

Seller represents and warrants to Purchaser as follows:

         6.1 Organization, Powers, and Qualifications. Seller is a California
state-chartered industrial loan company duly organized, validly existing and in
good standing under the laws of the State of California and has all requisite
corporate power and authority to own, lease and operate its properties and
assets, to lease the leased properties used in its business, and to carry on its
business substantially as it is being conducted on the date of this Agreement.

         6.2 Execution and Performance of Agreement. Seller has all requisite
corporate power and authority to execute, deliver, and perform this Agreement.
The execution, delivery, and performance of this Agreement by Seller will not
conflict with any provision of Seller's articles of incorporation or bylaws or
with any undertaking, agreement, decree, order, or judgment by which it is
bound. This Agreement constitutes the valid, legal, and binding obligation of
Seller, enforceable against it in accordance with its terms. The execution,
delivery, and performance of this Agreement have been duly and validly
authorized by the board of directors of Seller and by Seller's sole shareholder,
Global Bancorp. No other corporate proceedings on the part of Seller are
necessary to authorize this Agreement on its behalf or the consummation by it of
the transactions contemplated by this Agreement.

         6.3 Contracts. Seller is not in default of any material term of any
Contract, and there is no event which, with the lapse of time or giving of
notice or otherwise, would constitute such a default.

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         6.4 Disclosure. No representation or warranty of Seller hereunder and
no certificate, statement, or other document delivered by Seller or any officer
thereof hereunder or in connection with this Agreement or any of the
transactions contemplated hereunder contains any untrue statement of a material
fact or omits to state a material fact necessary in order to make the statements
contained herein or therein, in light of the circumstances under which they were
made, not misleading. Copies of all documents referred to in this Agreement
which Seller has furnished to or made available for inspection by Purchaser and
its affiliates are true, correct, and complete copies thereof and include all
amendments, supplements, and modifications thereto and all waivers thereunder.

                                   ARTICLE VII
                                    COVENANTS

         7.1 Best Efforts. Each party (a) shall use its best efforts to cause
the transactions contemplated hereby to be consummated immediately prior to the
merger pursuant to the Merger Agreement, and to prepare, file, and prosecute
promptly and diligently all federal and state regulatory filings and requests
for approval as shall be necessary to effect the transactions contemplated by
this Agreement; (b) represents that at the date hereof, it does not know of any
facts which would reasonably cause it to believe that all Regulatory Approvals
could not be obtained; and (c) agrees not to take any action or enter into any
agreement or arrangement that reasonably would be expected to jeopardize its
ability to obtain all Regulatory Approvals necessary for it to consummate the
transactions contemplated hereby; provided, however, that nothing in this
Agreement shall require either party or any of its affiliates to agree to any
conditions to the consummation of the transactions contemplated by this
Agreement imposed by any federal or state regulatory authority with jurisdiction
over such transaction which in that party's reasonable judgment would be unduly
burdensome.

         7.2 Confidentiality. Each party shall use all nonpublic information
that it obtains from the other pursuant to this Agreement, including information
obtained pursuant to Section 8.2 from the companies used by Seller for data
processing or pursuant to Section 8.7, solely to effect the transactions
contemplated by this Agreement or for other purposes consistent with the intent
of this Agreement and shall not use any of such information for any other
purpose, including, without limitation, the competitive detriment of any party.
Each party shall maintain as strictly confidential all nonpublic information it
learns from the other party, including information obtained pursuant to Section
8.2 from the companies used by Seller for data processing, and shall, upon
expiration or termination of this Agreement, return promptly to the other party
all confidential documents it received from the other party in connection with
this Agreement and the transactions contemplated hereby. Each party may make
available such information to its respective affiliates, counsel, accountants,
tax advisers, and consultants, provided such persons agree to be bound by this
Section 7.2. This section shall not prohibit the use or disclosure of
information that is required by law to be disclosed, information which is
available to the recipient on a nonconfidential basis, or information which
becomes public without the fault of the recipient.

         7.3 Rights of Access. Between the date of this Agreement and the
Closing Date, Seller shall afford to Purchaser and its officers and authorized
agents and representatives reasonable access to the properties, books, records,
contracts, documents, files, and other information relating to the Purchased
Assets.

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         7.4 Certain Transactions. Without the prior written consent of
Purchaser, Seller shall not, on or after the date of this Agreement:

             (a) Subject any of the Purchased Assets to any lien, claim, or
encumbrance, except incurred in the ordinary course of its business consistent
with past practice;

             (b) Except as permitted in this Agreement, take any action outside
of the normal course of business which Seller knows will have a material adverse
effect on the transactions contemplated hereunder or which Seller knows will
impair Purchaser's rights in any Purchased Assets, or Purchaser's ability to
collect upon any Purchased Asset; or

             (c) Agree to do any of the foregoing.

         7.5 Preservation of Business. Pending the Closing Date, Seller shall:

             (a) Use, manage, repair, and maintain the Purchased Assets with the
same care and diligence as Seller applies to its other assets;

             (b) Not do anything or fail to do anything which will cause a
breach of or a default in any Contract except for the transactions hereby
contemplated.

         7.6 Continuing Accuracy of Representations and Warranties. Pending the
Closing Date, neither Purchaser nor Seller will take any action or omit to take
any action which would cause or constitute a material breach of any of their
respective representations and warranties contained in this Agreement or which
would cause any such representations or warranties, if made on or as of the date
of such event or the Closing Date, to be untrue or inaccurate in any material
respect. In the event of and promptly upon becoming aware of the occurrence of
any event which would constitute or cause such a material breach or inaccuracy
or a material breach of any covenant hereunder, the party in breach will give
detailed written notice thereof to the other party and will use its best efforts
to prevent or promptly remedy such breach or inaccuracy.

                                  ARTICLE VIII
                              CONVERSION PROCEDURES

         8.1 Generally. Seller and Purchaser shall, before and after the Closing
Date, cooperate in good faith to ensure the orderly and efficient transfer and
conversion of the Purchased Assets.

         8.2 File Packages. Seller will provide Purchaser with copies of the
paper record of the Purchased Loans as it exists and all original loan files and
loan documents. The paper record, loan files and loan documents shall be
provided within thirty (30) days of the execution of this Agreement. On the
Closing Date, Seller agrees to provide a second set of these files as the final
record of Purchased Loans. On the Closing Date, Seller will show all Purchased
Loans as closed and perform no further processing on the Purchased Loans from
inception to the Closing Date.

         8.3 Histories: Checks. Within 10 Business Days after the Closing Date,
Seller shall provide Purchaser with a copy of all account histories, both in
paper and magnetic tape form. Seller

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shall perform and provide all research, including microfilm copies of activity
prior to the Closing Date, to Purchaser at cost. For the purpose of this
Agreement, the term "Account histories" means a copy of the last statement
Seller cuts on the Closing Date as stated in Section 8.2 and a complete history
of Purchased Loans.

         8.4 Notification of Customers. Prior to the Closing Date, (i) Seller
and Purchaser, after obtaining Regulatory Approvals, will jointly notify the
Purchased Loan customers (and shall equally share the cost of any joint notices)
that, subject to closing of the transactions contemplated by this Agreement,
Purchaser will be purchasing the Purchased Assets, (ii) Seller and Purchaser
shall each provide, or join in providing where appropriate, all notices that
Seller or Purchaser, as the case may be, is required to give by any regulatory
authority having jurisdiction or under applicable law or the terms of any other
agreement between Seller and any customer in connection with the transactions
contemplated hereby or as otherwise may be prudent or reasonably necessary in
connection with the transactions contemplated hereby, and (iii) following or
concurrently with the notice referred to in clause (i) above, Purchaser may
communicate with and deliver information, brochures, bulletins, and other
communications to customers concerning the transactions contemplated by this
Agreement and concerning the business and operations of Purchaser. A party
proposing to send any notice or communication pursuant to any paragraph of this
Section 8.5 shall furnish to the other party a copy of the proposed form of such
notice or communication at least 10 Business Days in advance of the proposed
date of the first mailing, posting, or other dissemination thereof to customers
and shall not unreasonably refuse to amend such notice to incorporate any
changes that the other such party proposes for any business purpose or as
necessary to comply with applicable statutes, rules, regulations, or
requirements of any regulatory authority having jurisdiction. All costs and
expenses of any notice or communication sent by Purchaser or Seller shall be the
responsibility of the party sending such notice or communication and all costs
and expenses of any joint notice or communication shall be shared equally by
Seller and Purchaser.

         8.5 Customer Names and Addresses. Prior to any notification in Section
8.4, and upon Purchaser's request, Seller shall provide Purchaser with mailing
labels, containing the name and complete mailing address for each of the
Purchased Loans as of a recent date.

         8.6 Purchased Loans Interest Reporting. Seller will timely report to
applicable taxing authorities, Purchaser and to Purchased Loan customers, with
respect to the period from January 1 of the year of the Closing Date, through
the Closing Date, all interest paid on the Purchased Loans.

         8.7 Purchased Loans. As soon as practicable, but not later than 10 days
from the date of this Agreement, Seller shall provide to Purchaser a written
schedule of Purchased Loans to be transferred to Purchaser pursuant to the terms
of this Agreement. Notwithstanding anything in this Agreement to the contrary,
from and after the date on which Purchaser receives such schedule until ten (10)
days prior to the Closing Date, Purchaser shall have the right to exclude from
the transaction any loan and such excluded loan shall not be transferred to
Purchaser pursuant to the terms of this Agreement on the Closing Date.
Purchaser's right to exclude such loans shall be exercisable by Purchaser giving
written notice to Seller at any time until ten (10) days before the Closing
Date. In the event that an Excluded Loan should inadvertently be transferred to
Purchaser on the Closing Date, Seller shall repurchase such loan at book value.

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         8.8 Further Documents. After the Closing Date, Seller and Purchaser
shall each permit the other reasonable access to and the right to inspect and
copy, the books and records of such party with respect to the transactions
contemplated hereby as may be reasonably necessary or appropriate to enable the
other party to prepare any additional documents, instrument, reports, or tax
returns as it or its counsel determines to be necessary or appropriate under the
circumstances.

         8.9 Cooperation on Certain Tax Matters. After the Closing Date, Seller
and Purchaser shall each (i) assist (and cause their respective affiliates to
assist) the other party in preparing any tax returns that party is responsible
for preparing and filing in accordance with this Agreement, (ii) cooperate fully
in preparing any audits of or disputes with taxing authorities regarding any tax
returns with respect to the Purchased Assets or income therefrom, (iii) make
available to the other and to any taxing authority as reasonably requested all
relevant information, records, and documents relating to taxes with respect to
the Purchased Assets or income therefrom, (iv) provide timely written notice to
the other of any pending or proposed tax audits or assessments with respect to
the Purchased Assets or income therefrom, for taxable periods for which the
other may have liability under this Agreement, and (v) furnish the other with
copies of all relevant correspondence received from any taxing authority in
connection with any tax audit or information request with respect to any taxable
period referred to in clause (iv) above. The party requesting assistance or
cooperation shall pay the other party's out-of-pocket expenses in complying with
such request to the extent that such expenses are attributable to fees and other
costs of unaffiliated third party service providers.

                                   ARTICLE IX
                                   TERMINATION

         9.1 Automatic Termination. This Agreement shall terminate, without
action by the parties or either of them on March 31, 2000, at 11:59 p.m.

         9.2 Grounds for Termination. This Agreement may be terminated by
written notice of termination at any time before the Closing Date only as
follows:

             (a) By mutual consent of Purchaser and Seller;

             (b) By Purchaser, upon written notice to Seller given at any time
if any of the representations and warranties of Seller contained in this
Agreement were untrue or incorrect in any material respect when made or become
untrue or incorrect in any material respect on or prior to the Closing Date in a
manner that cannot reasonably be expected to be corrected or cured prior to the
Closing Date or if Seller, within 10 Business Days after notice thereof from
Purchaser, fails to comply in any material respect with any of its covenants
contained in this Agreement;

             (c) By Seller, upon written notice to Purchaser at any time if any
of the representations and warranties of Purchaser contained in this Agreement
were incorrect in any material respect when made or become incorrect in any
material respect on or prior to the Closing Date in a manner that cannot
reasonably be expected to be corrected or cured prior to the Closing Date or if
Purchaser, within 10 Business Days notice thereof from Seller, fails to comply
in any material respect with any of its covenants contained in this Agreement;
or

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             (d) By Purchaser or Seller, upon written notice to the other at any
time if (i) Regulatory Approvals are not obtained prior to March 31, 2000, or
(ii) the transactions contemplated by this Agreement are disapproved by any
regulatory authority whose approval is necessary.

         9.3 Effect of Termination. In the event of the termination and
abandonment hereof pursuant to the provisions of Section 9.1 or Section 9.2,
this Agreement shall become void and have no force or effect, except that
provisions of Sections 7.2 and 10.1 and this Section 9.3 shall survive
termination. Such termination shall not relieve any party of liability for any
default or breach prior to such termination, but absent any such default or
breach by it, no party nor any of its officers, directors, or shareholders shall
have any liability to the other party for costs, expenses (including, without
limitation, legal and accounting fees and expenses), loss of anticipated
profits, or otherwise.

                                    ARTICLE X
                                  MISCELLANEOUS

         10.1 Costs and Expenses. Each party hereto shall pay its own expenses,
including, without limitation, the expenses of its own counsel, accountants, and
tax and financial advisers incurred in connection with this Agreement and the
transactions contemplated hereby. Purchaser and Seller shall each pay one-half
of the application fees for Regulatory Approvals.

         10.2 Mutual Cooperation. Subject to the terms and conditions herein
provided, each party shall cooperate with the other in carrying out the
provisions of this Agreement and in making all filings and obtaining all
necessary Regulatory Approvals and shall execute and deliver, or cause to be
executed and delivered, such regulatory notifications and additional documents
and instruments and do or cause to be done all additional things necessary,
proper, or advisable under applicable law to consummate and make effective the
transactions contemplated hereby.

         10.3 Entire Agreement. With respect to the subject matter hereof, this
Agreement, the schedules and exhibits hereto (which are incorporated herein),
and the documents delivered pursuant hereto constitute the entire Agreement and
understanding between the parties hereto and supersede any prior agreement or
understanding with respect to such subject matter.

         10.4 Notices. Any notice required or permitted under this Agreement
shall be given in writing (except as otherwise provided in this Agreement) and
shall be deemed effectively given upon personal delivery, facsimile
transmission, or similar method of communication, or on the second business day
after deposit with the United States Post Office, by registered or certified
mail, postage prepaid, addressed as follows:

         If to Purchaser, to:

                  Humboldt Bank
                  Post Office Box 1007
                  Eureka, California 95502
                  Attention: R. V. Barkley
                  Telephone:  (707) 269-3100
                  Facsimile:  (707) 445-0950

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         with a copy to:

                  Gary Steven Findley, Esq.
                  1470 North Hundley Street
                  Anaheim, California 92806
                  Telephone:  (714) 630-7136
                  Facsimile:  (714) 630-7910

         If to Seller, to:

                  Capitol Thrift & Loan Association
                  1424 Second Street
                  Napa, California 94559
                  Facsimile:  (707) 252-4950
                  Attention:  Robert F. Kelly, President/CEO

         with a copy to:

                  Allen, Matkins, Leck, Gamble & Mallory
                  333 Bush Street, 17th Floor
                  San Francisco, California 94104
                  Facsimile:  (415) 837-1516
                  Attention:  Roger S. Mertz, Esq.

or at such other address as a party may designate by notice given in the manner
provided herein.

         10.5 Governing Law: Venue. The validity, interpretation, and
enforcement of this Agreement shall be governed by the laws of the state of
California (without regard to principles of conflicts of law thereof), except to
the extent preempted by federal law. Legal action or proceedings with respect to
this Agreement and the transactions contemplated hereunder shall be brought in
the courts of the state of California or, if applicable, the courts of the
United States of America, located in San Francisco County, California.

         10.6 Modification and Waiver. No change or modification of this
Agreement shall be valid or binding upon the parties hereto, nor shall any
waiver of any term or condition thereof be deemed a waiver of such term or
condition in the future, unless such change or modification or waiver shall be
in writing signed by both parties.

         10.7 Severability. If any provision of this Agreement or the
application of any such provision shall be held invalid, illegal, or
unenforceable, the remainder of this Agreement shall not be affected thereby.

         10.8 Assignment: Binding Effect. Neither this Agreement nor any right
or obligation hereunder may be assigned by any party without the prior written
consent of the other party. This Agreement shall be binding upon and inure to
the benefit of the parties hereto and their respective successors and permitted
assigns.

                                       12

<PAGE>   13

         10.9 Form of Public Disclosures. No party shall make any public
disclosures concerning this Agreement or the transactions contemplated hereby
unless all the parties have approved in advance the form and substance thereof,
except as required by applicable law. No party shall unreasonably withhold such
approval.

         10.10 Captions: Counterparts. The article and section headings and the
table of contents in this Agreement are for convenience of reference only and
shall not affect the meaning or construction of this Agreement. This Agreement
may be executed in one or more counterparts, each of which shall be deemed to
constitute an original and shall become effective when one or more counterparts
have been signed by each party hereto and delivered to the parties.

         10.11 Manner of Payment. All payments due under this Agreement shall be
in lawful money of the United States of America.

                                       13

<PAGE>   14

IN WITNESS WHEREOF, the parties have caused this Agreement to be executed and
acknowledged by their duly authorized representatives as of the date first set
forth above.

                                        HUMBOLDT BANK

                                        By______________________________________

                                        CAPITOL THRIFT & LOAN ASSOCIATION

                                        By______________________________________

                                       14

<PAGE>   15

                                   EXHIBIT A

                                  BILL OF SALE

         This Bill of Sale ("Bill of Sale") is made as of _____________________
from Capitol Thrift & Loan Association, a California industrial loan corporation
("Seller") to Humboldt Bank, a California state-chartered bank ("Purchaser").

         WHEREAS, pursuant to the Loan Purchase Agreement, dates as of
_________________ (the "Agreement"), by and between Seller and Purchaser,
Purchaser has agreed to purchase from Seller all of its right, title and
interest in and to certain assets;

         NOW, THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt and adequacy of which are hereby
acknowledged by Seller, Seller does hereby sell, convey, assign, transfer and
deliver to Purchaser, and its successors and assigns, all of Seller's right,
title and interest in and to the Purchased Assets (such capitalized term and,
except as otherwise defined herein, all other capitalized terms used herein
shall have the meaning ascribed to such terms in the Agreement) as of the date
hereof.

         Seller covenants and agrees with Purchaser that Seller will execute,
acknowledge and deliver such other and further instruments and will take such
other action as may be necessary or desirable to carry out more effectively the
transfer of assets provided for herein.

         Nothing in this instrument, express or implied, is intended or shall be
construed to confer upon, or give to, any person other than Purchaser and its
successors and assigns, and remedy or claim under or by reason of this
instrument or any agreements, covenants or terms hereof, and all the agreements,
covenants and terms contained in this instrument shall be for the sole and
exclusive benefit of Purchaser and its successors and permitted assigns.

         This Bill of Sale shall inure to the benefit of Purchaser and its
successors and permitted assigns and be binding upon and enforceable against
Seller and its successors and permitted assigns.

                                        1

<PAGE>   16

         IN WITNESS WHEREOF, this Bill of Sale has been duly executed and
delivered by the duly authorized officer of Seller as of the date first written
above.

                                        CAPITOL THRIFT & LOAN ASSOCIATION

                                        By: ____________________________________
                                               Name:
                                               Title:

AGREED AND ACCEPTED.

HUMBOLDT BANK

By: ____________________________________
       Name:
       Title:

                                        2<PAGE>   1
                                                                   EXHIBIT 10.16

                            IMPOUND ACCOUNT AGREEMENT

This Impound Account Agreement (the "Agreement") is made and entered into as of
January 26, 2000 by and among Humboldt Bancorp, a California corporation
("Company") and Pacific Coast Bankers' Bank, a California banking corporation
("Impound Agent").

1.      RECITALS OF FACT.

        It is anticipated that Company will offer shares of its common stock for
sale pursuant to a registration statement filed with the Securities Exchange
Commission (the "Offering"). The Company desires that all funds received from
various persons (the "Subscribers") as subscriptions for shares of Company's
stock be placed in an impound account with a bank or trust company authorized to
do business in California, and desires that Impound Agent act as the depository
for such funds. The Company intends at this time to issue and sell a minimum of
$4,000,000 worth of shares and a maximum of $8,000,000 worth of shares of its
stock at a price to be determined by the Company and to deposit all funds
received from the Subscribers as subscriptions for such shares with Impound
Agent as depository.

2.      APPOINTMENT OF IMPOUND AGENT AS ESCROW AGENT.

        The Company hereby appoints Pacific Coast Bankers' Bank as Impound Agent
and Pacific Coast Bankers' Bank hereby accepts such appointment, subject to the
terms and conditions set forth in this Agreement.

3.      SUBSCRIPTION FUNDS HELD IN IMPOUND ACCOUNT.

        All funds received from the issuance of shares of the Company's stock
will be placed in an escrow account with Impound Agent, to be held by Impound
Agent. Such funds shall not become the property of or be released to Company
unless and until Company has sold the minimum of $4,000,000 worth of shares of
common stock and held its first closing. After the Company has held its first
closing, the Company may hold as many other closings as it deems appropriate
until it has sold $8,000,000 worth of shares, upon five (5) days notice to
Impound Agent, on which dates Impound Agent shall release additional funds
received from Subscribers to the Company. The Offering will end on the earlier
of (i) 45 days from the effective date of the registration statement with the
right to extend such date by an additional 15 days, (ii) the date on which
Company sells its final shares totaling $8,000,000, or (iii) such earlier date
on which Company decides to close Offering.

4.      SUBSCRIPTIONS FOR SHARES.

        Subscription agreements for shares of the Company's common stock will be
completed and submitted to Impound Agent in triplicate, along with checks and
other payment orders for the

                                        1

<PAGE>   2

amount of the subscriptions. Checks and other payment orders shall be made
payable to Pacific Coast Bankers' Bank fbo "Humboldt Bancorp". The Company will
inform Impound Agent of its intent to accept or reject subscriptions or to
accept a subscription in part. If any subscriptions are rejected or accepted
only in part, Impound Agent will refund the rejected amount to the Subscriber.
Upon a closing of the Offering, Impound Agent will return one copy of the
subscription agreement to the Subscriber, return one copy to Company, and retain
one copy for Impound Agent's records.

5.      INVESTMENT OF IMPOUND FUNDS.

        All funds received from the Subscribers as subscriptions for shares of
the Company's stock which are accompanied by copies of executed subscription
agreements for such subscriptions including any interest earnings on such funds,
will be placed in an impound account (the "Impound Account") with Impound Agent,
to be held by Impound Agent in the manner provided in this Agreement.

        Upon the clearing of checks received for subscriptions for shares under
normal banking practices and as and when directed in writing by Company, Impound
Agent shall invest and reinvest available funds deposited with it pursuant to
this Agreement in either (a) short-term (not to exceed 90 days) negotiable
direct obligations of the U.S. Treasury, (b) short term certificates of deposit
issued by Impound Agent, or (c) overnight federal funds. Such investments shall
at all times be subject to and authorized in accordance with the applicable laws
and regulations. Impound Agent shall not be liable or responsible for any loss
resulting investments made pursuant to this Section 5, except for losses which
result from the gross negligence or intentional misconduct of Impound Agent.

6.      TERM.

        This Impound Agreement shall commence as of the date set forth above and
shall expire upon distribution of the Impound Account as described in Section 7,
below.

7.      DISTRIBUTION.

        a. Upon receipt of notice to Impound Agent that the minimum of
$4,000,000 worth of shares of Company's common stock have been fully subscribed,
Impound Agent will release all funds (including interest earned thereon) in the
Impound Account to Company on the first closing date, pursuant to Company's
written instruction signed by two of its officers.

        b. If Company has not sold the minimum shares required by 45 days from
the effective date of the registration statement with the right to extend such
date by an additional 15 days and directs Impound Agent to distribute the
Impound Account to the Subscribers, then the Impound Account shall be
distributed to the Subscribers as follows: each Subscriber shall receive the
full amount of his or her subscription, with interest and without deduction for
expenses.

                                        2

<PAGE>   3

        c. In the event that the Impound Account is distributed pursuant to
Section 7b, above, all remaining obligations of Company described in Sections 9,
10a, 10b and 10f shall, without any further notice, become the obligation of
Company. The obligations created pursuant to this Section 7c shall continue
after the expiration of this Agreement.

        d. In the event that the Impound Account is distributed pursuant to
Section 7b, above, Impound Agent shall, as to each Subscriber, file Form 1099
with the State of California and the Internal Revenue Service, respectively.

8.      INFORMATION TO COMPANY.

        From time to time upon the request of Company, Impound Agent will
provide Company with information relative to the total number of subscriptions
received pursuant to this Agreement together with the aggregate number of shares
for which subscriptions have been received and the total amount of funds
received and collected. Upon termination or expiration of this Agreement,
Impound Agent shall provide an accounting of funds received, invested and
disbursed pursuant to this Agreement together with a list of Subscriber names
and addresses and the number of shares purchased by each Subscriber, and shall
return all original subscription agreements to Company.

9.      UNPAID CHECKS.

        In the event that any check received by Impound Agent is returned unpaid
by the drawee bank, Impound Agent will resubmit the check to the drawee
financial institution for repayment. In the event that any such resubmitted
check is returned unpaid a second time, Impound Agent may withdraw from the
funds held by it pursuant to this Agreement the amount of that check together
with an amount representing the applicable savings rate payable on the amount of
the check for the period during which the funds are credited as available funds
under this Agreement. Impound Agent shall forward any such check to Company
endorsed to Company without recourse. In the event that any such check is
returned to Impound Agent as unpaid after the funds represented thereby have
been distributed to any person, upon notification by Impound Agent Company shall
promptly pay the amount of that check to Impound Agent and Impound Agent shall
forward the check to Company endorsed to Company without recourse.

10.     RIGHTS OF IMPOUND AGENT.

        a. Company agrees to pay the regular fees of Impound Agent, as stated on
the attached fee schedule, as well as any reasonable fees for extraordinary
services performed by Impound Agent pursuant to this Agreement and agreed to in
writing by Company. Company also agrees to pay and/or reimburse Impound Agent
for its reasonable expenses and disbursements, including those of its agents,
consultants and attorneys. The obligations described in this section shall
continue notwithstanding the expiration or termination of this Agreement for any
reason.

                                        3

<PAGE>   4

        b. If conflicting demands are made or notices served by the parties upon
Impound Agent with respect to the Impound Account, Impound Agent shall be
entitled to refuse to comply with any such claim or demand and to suspend
performance of this Agreement so long as such disagreements shall continue; in
so doing Impound Agent shall not be held liable for damages or interest to
Company or to any person (including but not limited to Subscribers) for failure
to comply with such conflicting or adverse demands, Impound Agent shall be
entitled to continue to refrain and refuse to act until:

               (i) the rights of the adverse claimants have been finally
adjudicated in a court assuming and having jurisdiction of the parties and/or
the money, papers, and property involved in the claim or demand; and/or

               (ii) all differences have been settled by mutual agreement and
Impound Agents has been notified of the settlement in a writing signed by all of
the interested persons.

               In the alternative, Impound Agent may file a suit in interpleader
for the purpose of having the respective rights of the claimants adjudicated,
and deposit with the court all money, papers, and property held pursuant to this
Agreement, and Company agrees to pay all costs, expenses and reasonable
attorney's fees incurred by Impound Agent in connection therewith, the amount
thereof to be fixed and a judgment thereof to be rendered by the court in such
suit.

               c. Impound Agent shall act as a depository only and is not
responsible or liable in any manner whatever for the sufficiency, correctness,
genuineness or validity of any instrument deposited with it pursuant to this
Agreement, or with respect to the form or execution of any such instrument, or
the identity, authority, or rights of any person executing or depositing any
such instrument.

               d. Impound Agent shall have no responsibility for notifying
Company or any Subscriber of any sale, resale, loan, exchange or other
transaction involving any property described in this Agreement or of any profit
realized by any person or corporation in connection therewith, regardless of the
fact that such transactions may be handled by Impound Agent.

               e. Company agrees to hold harmless and indemnify Impound Agent,
its directors, officers, employees and agents for any loss, cost, liability,
damage or expense, including reasonable attorneys' fees and expenses, arising
out of or relating to this Agreement, the Impound Account, the performance of
Impound Agent's duties under this Agreement, or to any offering circular,
disclosure document or any subscription agreement relating to this Agreement;
provided, however, that no indemnification will be made for any act of
intentional misconduct or gross negligence of Impound Agent.

               f. Impound Agent:

                                        4

<PAGE>   5

               (i) shall be deemed conclusively to have given and delivered any
notice required to be given or delivered by it pursuant to this Agreement if the
same is in writing, signed by any one of Impound Agent's authorized officers and
mailed to Company at the addresses set forth in this Agreement;

               (ii) shall be entitled to consult with legal counsel and shall
not be liable for any action taken or omitted by that counsel;

               (iii) shall not, by act, delay, omission or otherwise, be deemed
to have waived any rights or remedies under this Agreement unless such waiver is
in a writing signed by Impound Agent; a waiver by Impound Agent of any right or
remedy on any one occasion shall not be construed as a bar to or waiver of any
such right or remedy on any future occasion;

               (iv) shall not be liable for any action taken or omitted to be
taken in good faith, and shall be liable only for its own gross negligence or
intentional misconduct;

               (v) shall be entitled to rely on any paper, request, certificate,
schedule, notice or other document which it in good faith believes to be genuine
and to have been signed or adopted by the proper party or parties;

               (vi) shall under no circumstances be required to risk its own
funds or otherwise incur any financial liability in the performance of any of
its duties hereunder, if it shall have reasonable grounds for believing that
repayment of such funds or adequate indemnity against such risk or liability is
not reasonably assured to it; and

               (vii) shall have no duties or responsibilities except those
expressly set forth in this Agreement, and the permissive right of Impound Agent
to do things or omit to do things as set forth in this Agreement shall not be
construed as a duty.

11.     REPRESENTATIONS REGARDING IMPOUND AGENT.

        Company represents and agrees that it has not made nor will it in the
future make any representation that states or implies that Impound Agent has
endorsed, recommended or guaranteed the purchase, value, or repayment of the
securities offered for sale by Company.

12.     MISCELLANEOUS.

        a. This Agreement may be amended only by the written agreement of
Company and Impound Agent. This Agreement shall be governed by the laws of the
State of California.

        b. This Agreement represents the entire agreement between Company and
Impound Agent.

                                       5

<PAGE>   6

        If Company or any of its officers, directors or agents has executed any
other agreements or documents relating to the subject matter of this Agreement,
or if any agreement is deposited under or arises out of this Agreement, Impound
Agent shall not be deemed a party to or be responsible for any provision thereof
unless expressly set forth in this Agreement or in a schedule to this Agreement.
Impound Agent shall be under no duty to enforce any such other agreement. In
case of any conflict between this Agreement and any such other agreement or
document or any schedule thereto, the provisions of this Agreement shall be
controlling.

        c. This Agreement may be executed and entered into in several
counterparts, each of which shall be deemed to be an original, and all of which
shall constitute but one and the same instrument.

        d. Impound Agent will not resign as Impound Agent under this Agreement
after the receipt of any funds from Subscribers without the express written
consent of Company.

        e. Any notice, report, demand, waiver or consent required or permitted
pursuant to this Agreement shall be in writing and shall be given by prepaid
first class mail, addressed as follows:

                                        6

<PAGE>   7

        To Impound Agent:

        Mail Instructions
        340 Pine Street, Suite 401
        San Francisco, CA 94104
        Attention:  Impound Account

        Wire Instructions
        Pacific Coast Bankers' Bank
        ABA No.   121042484
        Attention:  Impound Account FBO

        To Company:
        Humboldt Bancorp
        701 Fifth Street
        Eureka, California 95501
        Attention:  Theodore Mason, President

IN WITNESS WHEREOF, Company and Impound Agent have executed the Agreement on the
day and year first written above.

HUMBOLDT BANCORP
("COMPANY")

-----------------------------------          -----------------------------------
By:  Theodore Mason                          By:
Its: President                               Its:

PACIFIC COAST BANKERS' BANK
("IMPOUND AGENT")

-----------------------------------
By:  Tracy Holcomb
Its: Senior Vice President & COO

                                        7

<PAGE>   8

                                SCHEDULE OF FEES

<TABLE>
<S>                                                     <C>
Basic Impound Account Fee                               $1,500.00

Subscription Fee                                        $5.00 per Subscription

Rejected/Return Subscription Fee                        $10.00 per Subscription

Return Checks                                           $10.00 per check

Miscellaneous Fees at cost:                             Postage
                                                        Envelopes
                                                        Address Stamp
                                                        Overnight Mail
</TABLE>

Fees are due and payable upon the release of funds to Company

humboldt\finals-1amd#1docs\exh10.15-impoundag\1-27-00-2:51pm

                                        8

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