<PAGE>

     THIS LEASE, made and entered into as of the Date of Lease, by and between
NORTH VALLEY TECH LLC, a Delaware limited liability company, hereinafter
referred to as "Landlord", and PAC-WEST TELECOMM, INC., a California
corporation, hereinafter referred to as "Tenant".

                             W I T N E S S E T H:

     In consideration of the covenants and agreements hereinafter set forth to
be performed by the parties hereto, it is agreed by and between Landlord and
Tenant as follows:

     1.   Definitions and Basic Terms. The following terms, whenever set forth
          ---------------------------
in initial capitals in this Lease, shall have the meanings set forth
hereinbelow, except as otherwise expressly provided, or unless the context
otherwise requires:

     (a)  Date of Lease:      The date on which Landlord executes the Lease, as
                              set forth on the signature page hereof.

     (b)  Landlord's Mailing  55 Public Square, Suite 1900
          Address:            Cleveland, Ohio 44113

     (c)  Tenant's Mailing    4210 Coronado Avenue
          Address:            Stockton, California 95204

     (d)  Building:           North Valley Tech Center, both land and
                              improvements

     (e)  Premises:           Suite Number 100, located at 500 E. 84/th/ Avenue,
                              Thornton, CO 80229 on the first (1st) floor of the
                              east Building, containing approximately 24,316
                              useable square feet, (computed by measuring the
                              demised premises from the interior of the windows
                              to the exterior face of the corridor wall, and
                              from the center of partitions separating the
                              demised premises from adjoining premises, but with
                              no deductions made for columns and projections
                              necessary to the Building) equal to 26,504
                              rentable square feet (which area includes a
                              proportionate share of the Common Areas and
                              Facilities), as hatched or outlined on the floor
                              plan attached hereto as Exhibit A.

     (f)  Term:               "Term" shall mean a period of ten (10) years,
                              unless sooner terminated or extended in accordance
                              with this Lease.

     (g)  Commencement Date:  The date that is the earlier to occur of (i) April
                              1, 2000 or (ii) the date that a temporary
                              certificate of occupancy for the Premises is
                              issued by the City of Thornton, Colorado.

     (h)  Termination Date:   March 31, 2010
<PAGE>

     (i)  Base Rent:          The amounts, for the periods, set forth below,
                              payable in monthly installments in advance:

<TABLE>
<CAPTION>
                                                      Annual      Monthly      Rate Per
                                 Period             Base Rent   Installment  Square Foot
                                 ------             ---------   -----------  -----------
<S>                              <C>                <C>         <C>          <C>
                                 4/1/00 - 3/31/05  $390,934.00  $32,577.83     $14.75
                                 4/1/05 - 3/31/10  $417,438.00  $34,786.50     $15.75
</TABLE>

     (j)  Rent:               The Base Rent or Adjusted Base Rent, as the case
                              may be, and all other charges or sums payable
                              hereunder.

     (k)  Security Deposit:   Thirty-Two Thousand Five Hundred Seventy-Seven and
                              83/100 Dollars ($32,577.83)

     (l)  Tenant's Share:     The percentage which the rentable area of the
                              Premises is of the total rentable area of the
                              Building as of the end of the calendar year, which
                              as of the end of the first calendar year is agreed
                              to be 5.832%. Adjustments to the rentable area of
                              the Premises or the Building will result in a
                              proportionate adjustment to the Percentage of
                              Tenant's Share.

     (m)  Permitted Use:      To install, operate and repair telecommunications
                              equipment; market and provide telecommunications
                              services; to maintain general offices; to provide
                              facilities and services to Tenant's colocation
                              customers; to install and repair off-site
                              telecommunication equipment and to accommodate
                              related personnel.

     (n)  Base Year:          The calendar year commencing January 1, 2000, and
                              ending December 31, 2000.

     (o)  Comparison Year:    The first full calendar year following the Base
                              Year and each subsequent full calendar year of the
                              Term.

     (p)  Operating Expenses: All expenses incurred during the Base Year or the
                              Comparison Year, calculated in accordance with
                              Generally Accepted Accounting Principles ("GAAP"),
                              in the operation, improvement, repair, replacement
                              and maintenance of the Building including, without
                              limitation, (i) the cost of water and sewer,
                              insurance, labor, cleaning materials and supplies,
                              and security, if any; (ii) expenses for
                              management, maintenance of elevators and
                              mechanical systems, rubbish removal, window
                              washing and other services, and roof repairs;
                              (iii) the opera-

                                       2
<PAGE>

                              tion, improvement, repair, replacement and
                              maintenance of the Building Common Areas and
                              Facilities including all surfaces, floor and wall
                              coverings, decorative items, and window coverings,
                              lighting facilities and exteriors; and (iv) the
                              cost of any operation, improvement, repair,
                              replacement or maintenance which does not
                              materially add to the value of the Building nor
                              appreciably prolong its life, but merely keeps the
                              Building in ordinarily efficient operating
                              condition, except that if such improvement, repair
                              or replacement results in a substantial cost,
                              labor or energy saving, such cost shall be deemed
                              an Operating Expense. All such costs will be
                              amortized over the number of years required by
                              GAAP, with an appropriate finance charge, all of
                              which shall be considered an Operating Expense. If
                              and for so long as the Building is less than fully
                              leased and occupied, Operating Expenses shall
                              include an amount representing the estimated
                              operating expenses that Landlord would incur if
                              the Building was 95% leased and occupied, as
                              determined by Landlord in a reasonable, customary
                              and commonly accepted manner.

                              Notwithstanding anything to the contrary in the
                              definition of Operating Expenses, the Operating
                              Expenses shall not include the following:

                                   (1)  The cost of repair to the Building,
                                        including the Premises, to the extent
                                        the cost of the repairs is reimbursed by
                                        insurance or condemnation proceeds,
                                        covered by warranty or otherwise
                                        reimbursed by third parties other than
                                        as a part of Operating Expenses;

                                   (2)  All items and services for which Tenant
                                        or any other tenant in the Building
                                        reimburses Landlord other than through
                                        Operating Expenses (or is so obligated
                                        to reimburse Landlord) and all items and
                                        services supplied selectively to any
                                        tenant without reimbursement, provided
                                        that, any item or service supplied
                                        selectively to Tenant shall be paid for
                                        by Tenant;

                                   (3)  Advertising and marketing costs,
                                        including, without limitation, leasing
                                        commissions, attorneys' fees in
                                        connection with the negotiation and
                                        preparation of letters, deal memos,
                                        letters of intent, leases, subleases
                                        and/or assignments, space

                                       3
<PAGE>

                                        planning costs, and other costs and
                                        expenses incurred in connection with the
                                        lease, sublease and/or assignment
                                        negotiations and transactions with
                                        present or prospective tenants of the
                                        Building or their successors;

                                   (4)  The cost of improving or renovating
                                        space for tenants or space vacated by
                                        any tenant (including Tenant),
                                        including, without limitation,
                                        architects', engineers' and space
                                        planners' fees and expenses, and costs
                                        of permits and inspections;

                                   (5)  The cost of utilities charged to
                                        individual tenants (including Tenant)
                                        including any and all costs for Tenant's
                                        electrical usage and HVAC usage;

                                   (6)  The depreciation of the Building;

                                   (7)  Any payments of any kind due and payable
                                        under any mortgage, deed of trust or
                                        other financing affecting the Building
                                        or under any ground lease or master
                                        lease, including, without limitation,
                                        any principal, interest, points and fees
                                        on debt or amortization payments, and
                                        late payment penalties and interest on
                                        any real property mortgages or deeds of
                                        trust and ground lease payments, and
                                        other costs of financing or refinancing
                                        the Building;

                                   (8)  Legal, accounting, consulting and other
                                        related expenses associated with the
                                        enforcement of leases, disputes with
                                        lessees or prospective lessees, or the
                                        defense of Landlord's title to the
                                        Building;

                                   (9)  Landlord's general corporate overhead
                                        and general administrative expenses not
                                        related to the operation of the
                                        Building, including costs of preparing
                                        corporate, partnership or other tax
                                        returns, or financial statements not
                                        related to the operation of the
                                        Building, and all compensation to
                                        executives, officers or partners of
                                        Lessor or to persons who are executives
                                        or officers of partners of Landlord or
                                        to any other person at or above the
                                        level of building manager, other than
                                        the building manager of the Building;

                                       4
<PAGE>

                                   (10) Unless required to be charged by
                                        Landlord pursuant to any applicable
                                        requirements, any compensation paid to
                                        clerks, attendants or other persons in
                                        commercial concessions, including
                                        parking facilities operated by Landlord
                                        and other costs directly related to the
                                        operation of such commercial concessions
                                        including bookkeeping, parking
                                        insurance, parking management fees,
                                        tickets, striping and uniforms, and all
                                        other costs directly related to the
                                        installation, operation and maintenance
                                        of such commercial concessions;

                                   (11) Governmental fines or penalties assessed
                                        as a result of Landlord's failure to
                                        make payments in a timely manner or to
                                        comply with applicable requirements;

                                   (12) Except for making repairs or keeping
                                        permanent systems in operation while
                                        repairs are being made, rentals and
                                        other related expenses incurred in
                                        leasing air-conditioning systems,
                                        elevators or other equipment ordinarily
                                        considered to be of a capital nature,
                                        except equipment not affixed to the
                                        Building which is used in providing
                                        janitorial or maintenance services;

                                   (13) Costs of capital improvements and other
                                        costs which are to be capitalized and
                                        not expensed in accordance with GAAP,
                                        including, without limitation, capital
                                        repairs due to casualty, capital costs
                                        of any renovation, improvement or
                                        addition to common areas, capital costs
                                        of compliance with health, safety and
                                        disability access laws to the extent the
                                        Building did not comply with such
                                        applicable requirements in effect and as
                                        interpreted as of the date of this
                                        Lease; provided that such costs to
                                        comply with applicable requirements
                                        arising after the date of this Lease or
                                        re-interpreted after the date of this
                                        Lease, shall be included in Operating
                                        Expenses provided that such permitted
                                        capital expenses are amortized over the
                                        useful life thereof;

                                       5
<PAGE>

                                   (14) Cost of compliance with laws relating to
                                        hazardous substances or substances which
                                        are incurred (a) as a result of
                                        Landlord's negligence or intentional
                                        acts in the course of construction of
                                        the Building, including the selection
                                        and use of building materials which
                                        Landlord should have known were
                                        hazardous substances at the time of
                                        their installation, or (b) as a result
                                        of the presence of hazardous substances
                                        in the soil or groundwater under the
                                        Building on or before the date of
                                        execution of this Lease;

                                   (15) Liability covered by insurance carried
                                        by Landlord the premiums for which are
                                        included in Operating Expenses, or which
                                        would have been covered by insurance
                                        otherwise required to be carried by
                                        Landlord under this Lease but for
                                        failure to insure as a result of
                                        Landlord's intentional acts or omissions
                                        or negligence (but not as a result of
                                        commercial impracticability of obtaining
                                        such insurance);

                                   (16) Expenses resulting directly from the
                                        willful misconduct or gross negligence
                                        of Landlord or any of its employees or
                                        agents;

                                   (17) Costs of repairs or modifications to the
                                        Building or Premises, if the Building or
                                        Premises are not in full compliance with
                                        all governmental regulations, ordinances
                                        and laws effective at the Commencement
                                        Date;

                                   (18) Any bad debt loss, rent loss or reserves
                                        for bad debts or rent loss and reserves
                                        for capital improvements;

                                   (19) Costs arising from Landlord's charitable
                                        or political contributions;

                                   (20) Costs, including capital costs, incurred
                                        in connection with upgrading the
                                        Building to comply with applicable
                                        requirements as such applicable
                                        requirements were interpreted as of the
                                        Commencement Date of this Lease;
                                        provided that

                                       6
<PAGE>

                                        such costs to comply with applicable
                                        requirements arising after the
                                        Commencement Date of this Lease or re-
                                        interpreted after the Commencement Date
                                        of this Lease, shall be included in
                                        Operating Expenses;

                                   (21) Costs arising from repairs for
                                        construction of design defects in the
                                        Building (including, without limitation,
                                        any building systems) or in lessee
                                        improvements installed by Landlord;

                                   (22) Legal expenses, accounting expenses,
                                        other professional fees and other
                                        transactional costs arising out of the
                                        sale, syndication or financing of the
                                        Building or any interest therein, or the
                                        construction of improvements;

                                   (23) Costs of disputes between Landlord and
                                        any third party regarding matters
                                        unrelated to the Building;

                                   (24) Costs of disputes between Landlord and
                                        any employee, agent or contractor of
                                        landlord or with any mortgagee or ground
                                        lessor;

                                   (25) If Landlord fails to carry any of the
                                        insurance required to be carried by
                                        Landlord pursuant to the terms of this
                                        Lease, any cost which would have been
                                        covered by such insurance coverage; and

                                   (26) Any rental amount applied for the
                                        management / leasing office in the
                                        Building.

                              Notwithstanding anything herein to the contrary,
                              Landlord shall not be entitled to include the
                              costs of capital replacements or expenditures
                              except that, in the event Landlord installs
                              equipment in, or makes improvements or alterations
                              to, the Building which are for the purpose of
                              either (a) reducing energy, maintenance or other
                              operating costs, or (b) which are required under
                              any governmental laws, rules, regulations or
                              ordinances which are not required on the
                              Commencement Date, then, even though such costs
                              are capital expenditures, Landlord may include in
                              Operating Expenses reasonable charges for the same
                              so as to amortize such investment over the useful
                              life of such equipment, improvement or alteration
                              on a straight-line basis, provided,

                                       7
<PAGE>

                              however, with respect to items of the type
                              described in clause (a), the amount included in
                              Operating Expenses in any year shall not exceed
                              the annual savings which were reasonably projected
                              to result from that expenditure at the time it was
                              made.

     (q)  Taxes:              Taxes and assessments, special or otherwise,
                              (including all expenses incurred in connection
                              with disputing the amounts thereof) and sewer
                              charges, if any, levied or assessed upon or with
                              respect to the Building and the land upon which it
                              is located, or upon or against the rent payable
                              hereunder for the privilege of leasing real
                              property. If and for so long as the Building is
                              less than fully leased and occupied, Taxes shall
                              include an amount representing the estimated taxes
                              that Landlord would incur if the Building was
                              fully leased and occupied, as determined by
                              Landlord in a reasonable, customary and commonly
                              accepted manor.

     (r)  Common Areas and    The common areas of the Building including, but
          Facilities:         not limited to, lobbies, vestibules, stairways,
                              corridors, passenger and freight elevators, truck
                              docks, and access roads.

     (s)  Electric service    N/A
          charge:

     (t)  Broker:             CB Richard Ellis, Inc.
                              Independence Plaza
                              1050 Seventeenth Street, Suite 800
                              Denver, CO 80265

                              And

                              Partners National Real Estate Group, Inc.
                              3838 Oak Lawn Avenue
                              Suite 850
                              Dallas, Texas 75219

     (u)  Guarantor:          N/A


     2.   Premises; Term.
          --------------

          (a)  Landlord hereby leases to Tenant and Tenant hereby leases from
Landlord the Premises, for the Term and upon the conditions, covenants, and
agreements hereinafter set forth.

                                       8
<PAGE>

          (b)  Subject to paragraph 17 hereof Tenant shall have a nonexclusive
right to use the Common Areas and Facilities of the Building which lead to and
from the Premises and other areas shared with other tenants in the Building.
Nothing herein contained shall be construed as a demise to Tenant of the roof,
exterior walls of the Building, space outside the Premises, air rights above or
outside of the Premises, or of the Common Areas and Facilities.

          (c)  Landlord warrants that it is the lawful tenant under that certain
ground lease dated July 22, 1969 and recorded on July 22, 1969, as instrument
no. 734560 in Book 1166 at page 140 of the Official Records of Adams County,
Colorado and that the term of such ground lease has been extended to a date that
extends beyond the time of the Term, as extended, if at all, pursuant to Section
60 of this Lease.

     3.   Possession/Tenant Improvements.  All work and items not within the
          ------------------------------
scope of the Landlord Improvements to be furnished and installed in the Premises
(the "Lessee Improvements"), such as furniture, furnishings, equipment and
telephones, shall be furnished and installed by Tenant at Tenant's expense.
Tenant shall adopt a schedule compatible with the schedule of Landlord's
contractors and shall conduct its work in such a manner and at times as not to
unreasonably interfere with or delay the work of Landlord's contractors. Tenant
shall not begin installing Tenant Improvements without Landlord's prior approval
of Tenant's contractors, subcontractors and all materials and items to be used
for and incorporated in Tenant Improvements, which approval shall not be
unreasonably withheld. Subject to the preceding requirements, Landlord shall
complete items 1, 6 and 8 under "Construction/Demolition" in Exhibit "E" on or
before January 15, 2000 and give access and entry to the Premises to Tenant and
its contractors and subcontractors for installation of the Tenant Improvements
not later than January 1, 2000. If entry is prior to the Commencement Date, the
entry shall be subject to all the terms and conditions of this Lease except the
payment of Base Rent.

     4.   Rent. Tenant shall pay Landlord the Rent, without deduction or offset,
          ----
in advance, on or before the tenth day of each calendar month during the Term,
at Landlord's Mailing Address, or at such other place as Landlord may from time
to time designate in writing. The first month's Base Rent shall be paid upon
execution hereof. The installment of Rent payable for any partial calendar month
shall be prorated based upon a 30-day calendar month. Checks delivered in
payment of Rent shall not constitute payment until paid by the drawee. Tenant
however shall not be responsible for delays in the collection of checks caused
by the Landlord, Landlord's bank or the clearing house. Delivery of a check by
the tenth (10) of a month which is promptly paid in the ordinary course of
business shall satisfy the payment requirements of this section. The covenant to
pay Rent hereunder is independent of any other covenant contained in this Lease.

                                       9
<PAGE>

     5.   Rent Escalation.
          ---------------

          (a)  There shall be added to the Base Rent for each Comparison Year,
     Tenant's Share of the net aggregate increase, if any, in the amount of
     Operating Expenses and Taxes for the Comparison Year over those for the
     Base Year. The Base Rent as so increased is herein referred to as the
     "Adjusted Base Rent". The Adjusted Base Rent for any Comparison Year shall
     serve as the basis for an estimate of Adjusted Base Rent due for the next
     Comparison Year until the computation for that Comparison Year has been
     made. The difference between the actual increase in Operating Expenses and
     Taxes for any Comparison Year and the estimated Adjusted Base Rent for such
     Comparison Year shall be promptly paid by Tenant upon Tenant's receipt of a
     statement of such adjustment. After the Adjusted Base Rent has been
     established, it shall retroactively become payable from the beginning of
     the calendar year. The remaining monthly Rent installments shall be
     adjusted accordingly. Amounts due for any partial year of the Term in
     accordance with the foregoing shall be prorated on a calendar year basis.
     Additionally, within one hundred twenty (120) days after the end of the
     Base Year, Landlord will submit to Tenant for Tenant's review the
     compilation of the Operating Expenses and Taxes, adjusted as required in
     this Lease, for the Base Year. After receipt of such statement, Tenant will
     have one hundred twenty (120) days to dispute any item in the statement or
     manner of calculation of the Operating Expenses and Taxes.

          With respect to Taxes, the statement of adjustment shall reflect, as
     of the date prepared, Taxes incurred for the Base Year and for the
     Comparison Year, whether the same shall be definitive or subject to
     subsequent revision. Should Taxes for the Base Year or any Comparison Year
     be subsequently reduced or increased, Landlord shall recompute the Taxes
     using the amount of the Taxes for the Base Year as so reduced or increased
     for all Comparison Years prior to the Comparison Year in which the
     reduction or increase is granted. In the event of any tax abatements, tax
     phase-in or other similar tax programs that result in an artificially
     lowered tax amount for the Base Year, the tax amount established for the
     Base Year will be increased to reflect the amount that would have been
     expended in the absence of such programs. All changes to Adjusted Base Rent
     due from Tenant by reason thereof shall be payable within thirty (30) days
     after Tenant's receipt of the statement therefor.

          (b)  Landlord shall, during Landlord's regular business hours, make
     available to Tenant records, in reasonable detail, of Operating Expenses
     and Taxes for the period covered by such statement or statements, for a
     period of ninety (90) days after the mailing of such statements to Tenant.
     If Tenant shall not dispute any item in any such statement within thirty
     (30) days following Tenant's receipt of such statement, Tenant shall be
     deemed to have waived any objection thereto.

     6.   Security Deposit.
          ----------------

          (a)  Tenant has deposited with Landlord the Security Deposit, the
     receipt of which (if by check subject to collection) is hereby
     acknowledged. The Security Deposit

                                       10
<PAGE>

     shall be held by Landlord, without liability for interest thereon, as
     security for full performance due of Tenant under this Lease. Upon
     expiration of the Term and written request therefor, the Security Deposit
     shall be returned to Tenant, unless Landlord has reasonable cause to
     withhold all or a portion thereof.

          (b)  If any Rent shall be overdue and unpaid, or should Landlord have
     made payments on behalf of Tenant, or should Tenant fail to perform any of
     the covenants or agreements of this Lease, then Landlord may, without
     prejudice to any other remedy which Landlord may have, apply all or a
     portion of the Security Deposit toward the payment of Rent, or toward any
     loss, damage or expense sustained by Landlord resulting therefrom. In such
     event Tenant shall forthwith restore the Security Deposit to the original
     sum.

          (c)  In the event bankruptcy, insolvency, reorganization or other
     creditor-debtor proceedings shall be instituted by or against Tenant, its
     successors or assigns, or any guarantor of Tenant hereunder, the Security
     Deposit shall be deemed to be applied first to the payment of Rent due to
     Landlord for all periods prior to the institution of such proceedings.

          (d)  In the event that Landlord's interest in the Premises is sold,
     transferred or assigned, Landlord shall deliver the Security Deposit to the
     acquirer of such interest. Thereupon, Landlord shall be discharged and
     released from all further liability with respect to the Security Deposit
     and Tenant agrees to look solely to the new landlord for the return of the
     Security Deposit. This provision shall also apply to any subsequent
     transferees. No holder of a mortgage or deed of trust or lessor under a
     ground or underlying lease to which this Lease is or may be superior or
     subordinate shall be held responsible in connection with the Security
     Deposit, unless it has received the Security Deposit.

     7.   Personal Property and Business Taxes.  Tenant shall pay, prior to
          ------------------------------------
delinquency, all taxes assessed against or levied upon fixtures and all property
of Tenant located in the Premises.  When possible, Tenant shall cause said
fixtures and property to be assessed and billed separately from the real
property of which the Premises form a part.  In the event any or all of Tenant's
fixtures and property shall be assessed and taxed against Landlord, Tenant shall
pay said taxes within ten (10) days after receipt of a written statement setting
forth the amount of taxes applicable to Tenant's fixtures and property.  Tenant
shall pay, prior to  delinquency, all license fees and taxes imposed upon the
business of Tenant.

     8.   Use. Absent the prior written consent of Landlord, Tenant shall not
          ---
use the Premises other than for the Permitted Use.  Tenant shall not use the
Premises in violation of any law or of the certificate of occupancy issued for
the Building.  Within five (5) days of receipt of a notice from  Landlord,
Tenant shall discontinue any use of the Premises which is declared unlawful or
which imposes any duty upon Landlord.  Tenant shall not permit anything to be
done which will invalidate or increase the cost of insurance covering the
Building or property located therein.  Tenant shall, upon demand, reimburse
Landlord for any additional premium charged by reason of Tenant's failure to
comply with the provisions hereof.

                                       11
<PAGE>

     9.   Alterations and Improvements.  Except as may be provided in the "Work
          ----------------------------
Letter" attached hereto as Exhibit "E" and made a part hereof, or as otherwise
provided in this Lease, Landlord shall not be required to alter or improve the
Premises or the Building.  Tenant accepts the Premises in an "as is" condition
and agrees to perform alterations or improvements to the Premises in accordance
with plans and specifications prepared by a certified architect, all at Tenant's
sole cost and expense, subject to Landlord's prior approval, and in accordance
with all applicable laws, ordinances, rules and regulations. Prior to commencing
any alteration or improvement to the Premises, Tenant shall forward to Landlord
three (3) sets of blueprints and one (1) set of sepias of Tenant's proposed
work, and Landlord will complete its review of Tenant's plans within three (3)
business days.  Landlord may in its sole discretion impose requirements as to
the manner of performance of any work by or for Tenant in the Premises.  All
work shall be performed in a good and workmanlike manner using quality material
and shall be promptly completed, lien-free,  by a contractor who is insured,
bonded and has been pre-approved by Landlord. Prior to the commencement of such
work, Tenant or Tenant's general contractor agrees to deliver to Landlord a
Certificate of Worker's Compensation insurance in statutory limits from each
contractor and subcontractor as well as evidence of automobile insurance,
including "non-owned" automobiles, covering personal injury, bodily injury and
property damage, including death resulting therefrom, in the combined single
limit amount of $1,000,000.00 and comprehensive general liability in the
combined single limit amount of $1,000,000.00, with Landlord listed as an
additional named insured.

     Tenant shall provide Landlord with properly completed lien waivers executed
by Tenant's general contractor and, as to labor and materials valued in excess
of $5,000.00, by every subcontractor, including sole proprietorships,
participating in Tenant's work, and every material supplier delivering materials
directly to the Premises.

     10.  Ownership of Improvements.
          -------------------------

          (a)  All alterations and improvements in the Premises made by either
     party (except to Tenant's personal property, furniture and furnishings,
     signs and trade fixtures) shall become the property of Landlord and shall
     be surrendered with the Premises as provided for herein.

          (b)  Tenant shall have the option to remove, at Tenant's sole cost and
     expense, and retain all of Tenant's owned or leased telecommunications
     equipment, telecommunications switches, antennas, computer hardware, fiber
     cables and other fiber optic transmission facilities, transmission
     equipment, machinery, equipment, air conditioning components, furniture,
     and other tangible personal property including dies, tools, jigs, and
     office equipment and all equipment belonging to co-locators.  Without
     limitation of the foregoing the Tenant can remove:

          (1)  All, equipment and machinery installed by Tenant;

          (2)  all HVAC equipment, provided that Tenant's contractors shall
               perform such removal and restore the areas where the equipment
               has been located

                                       12
<PAGE>

               to a condition at least as good as received, normal wear and tear
               excepted and may remove all associated work if requested by
               Landlord, which may include ducting, electrical runs and
               enclosures, all at Tenant's sole cost and expense;

          (3)  All ALCATEL and DSC switch equipment and associated peripheral
               equipment, all transmission switch equipment, patch panel and
               associated cables, co-location cabinets and associated equipment,
               all electrical equipment associated with this equipment and
               including all battery and UPS power plant equipment;

          (4)  All generators, fuel tanks and associated piping and sound
               control gear and associated conduit and cable.

          (5)  The FM200 dry fire suppression system including the gas
               containers, controls and all cable and control boxes. Tenant
               shall not remove the sprinkler piping and nozzles.

          Tenant shall repair and restore any damage to the Building or Premises
     caused by the removal of any such property.

     11.  Repairs.
          -------

          (a)  Landlord shall maintain and keep in good repair the Building,
     including the roof, exterior walls, all mechanical systems in the Building,
     the parking lots, and the floors, ceilings, and perimeter walls but
     excluding Tenant's HVAC equipment. In the event the necessity for such
     repairs shall have been occasioned by Tenant or any permitted subtenant or
     licensee of Tenant, or their respective employees, agents, contractors or
     any person, firm or corporation acting on its behalf, Tenant agrees to make
     such repairs at Tenant's sole cost and expense. Except in cases of an
     emergency, Landlord shall not be required to commence any repair until
     after receipt of written notice from Tenant. Tenant shall allow Landlord
     reasonable time in which to commence and complete such repairs. Landlord
     shall use reasonable efforts to make such repairs with a minimum of
     inconvenience, disruption, or loss of business to Tenant.

          (b)  Except as provided in subparagraph (a) of this paragraph, Tenant
     agrees to keep and maintain the Premises, the fixtures and equipment
     therein and the appurtenances thereto in good repair and condition at
     Tenant's own cost and expense, and to make all necessary repairs and
     replacements thereto. Tenant shall arrange and pay for all janitorial
     services required for the Premises. Tenant shall keep and maintain the
     Premises in a first-class condition throughout the Term. Tenant shall
     replace all damaged glass with glass of equal quality. In the case of
     damage or destruction by insurable casualty or by eminent domain, the
     obligations of Landlord and Tenant shall be controlled as hereinafter
     provided.

                                       13
<PAGE>

          (c)  Following initial construction of the Premises Tenant may, at its
     own cost, paint, paper or change floor coverings, or otherwise alter the
     Premises, provided that (i) the structural integrity or value of the
     Building shall not be adversely affected and (ii) the cost of such
     alteration does not exceed Five Dollars ($5.00) per square foot; and,
     except as otherwise permitted herein, the sprinkler system is not thereby
     affected. In all other instances, Tenant shall secure prior written
     approval of Landlord. Tenant shall submit to Landlord plans and
     specifications for such proposed work, together with the name of the
     contractor and a statement of the estimated cost thereof. Prior to starting
     such work, Tenant agrees to deliver to Landlord a certificate of worker's
     compensation insurance in statutory limits from Tenant's contractor as well
     as evidence of insurance coverages to be maintained by Tenant hereunder.
     Such work shall be promptly completed in accordance with such approved
     plans and specifications, applicable laws and ordinances, and rules and
     requirements of Landlord's insurance carriers, subject to the terms of
     Tenant's indemnity set forth under paragraph 16 hereof and Tenant's
     obligation to insure such liability under paragraph 28 hereof.

          (d)  The term "repairs" shall include repairs, replacements, renewals,
     alterations, additions, improvements and betterments.

          (e)  If Tenant shall fail or refuse to make repairs as set forth
     above, or if Landlord is required to make any repairs because of any act or
     omission of Tenant (or Tenant's permitted subtenant, business invitee or
     licensee, or their respective employees, agents or contractors, or any
     person, firm or corporation acting on Tenant's behalf), Landlord shall have
     the right, but not the obligation, upon ten (10) days' notice (except in
     case of an emergency), to enter upon the Premises to make such repairs, and
     add the cost thereof to the next installment of Rent due.

     12.  Building Services.  Landlord shall furnish to the Premises water for
          -----------------
lavatory and drinking purposes.

     Except as otherwise expressly provided in this Lease, Tenant shall comply
with all rules and regulations which Landlord establishes for the protection of
Building services, including but not limited to those rules and regulations set
forth on Exhibit "G" attached hereto. Such rules and regulation shall not
conflict with any provision of this Lease and shall be enforced to all tenants
uniformly. Landlord shall have free access to all mechanical installations of
Landlord at all times. Where failure to furnish any of said utilities or
services is caused by strikes, accidents, or conditions beyond the control of
Landlord, Landlord's failure shall neither be deemed an eviction or disturbance
of Tenant's use or possession of the Premises, nor shall such failure render
Landlord liable to Tenant, nor relieve Tenant of its Lease obligations.

     Except as otherwise expressly provided in this Lease, Tenant agrees not to
use any apparatus or device which may increase the amount of such services
usually furnished to the Premises without the prior written consent of Landlord.
Landlord reserves the right to charge for such increased services.

                                       14
<PAGE>

     Landlord reserves the right, without being liable to Tenant and without
abatement or diminution in Rent, to suspend, delay or stop any of the services
to be furnished and provided by Landlord whenever necessary due to any cause
beyond Landlord's control, or for emergency, inspection, cleaning, repairs,
replacements, alterations, improvements or renewals that in Landlord's judgment
are desirable or necessary; and Landlord may suspend any of those services until
completion of any work or until the cause of the suspension has been removed.
Failure by Landlord to any extent to furnish any defined services, or any
cessation of services due to any causes described in the preceding sentence,
shall not render Landlord liable in any respect for damages to either person or
property, nor be construed as an eviction of Tenant, nor work an abatement of
Rent, nor relieve Tenant from fulfillment of any covenant or agreement of this
Lease. Should any of the equipment or machinery utilized in supplying the
services break down, or for any cause cease to function properly, Landlord shall
use reasonable diligence to repair the same promptly, but Tenant shall have no
right to terminate or repudiate this Lease, and shall have no claim for rebate
or abatement of rent or damages, on account of any resulting interruptions in
service.

     13.  Electrical Current.  Electric service to the Premises shall be
          ------------------
separately metered. Tenant shall pay to its electric utility provider the cost
of the consumption of electrical service used in the Premises, calculated at the
rate chargeable to Tenant by the local utility company, as provided in Tenant's
contract with the local utility company.

     Tenant covenants and agrees that its use of electric current shall never
exceed the capacity of the feeders to the Premises, as to be provided pursuant
to Exhibit "E," the Building, the risers or wiring installations. Tenant shall
make no alteration to electrical service equipment supplying primary power to
the Premises without obtaining the prior written consent of Landlord in each
instance.

     14.  Access.  Only after no less than 24-hour notice to Tenant and only by
          ------
accompaniment at all times by an employee of Tenant, Landlord and its agents
shall have the right to enter the Premises for the purpose of inspecting the
Premises, showing the Premises to prospective mortgagees or purchasers of the
Building, and  making alterations, repairs, improvements or additions to the
Premises or to  the Building for any purpose.  Notwithstanding the foregoing,
Landlord acknowledges that Tenant maintains and operates sensitive equipment in
the Premises, and, accordingly, Landlord will make its best efforts to minimize
interference with Tenant's equipment in the event Landlord enters the Premises
to make the aforementioned alterations, repairs, improvements or additions, to
inspect the Premises or to show the Premises to prospective mortgagees or
purchasers, or, in the case of the last six months of the Term, or any extended
term, to show the Premises to prospective tenants.  Except as provided in the
preceding sentence or upon Tenant's consent, Landlord is not permitted to enter
the Premises with prospective tenants during the Term or any extension thereof.
During the six (6) months prior to the end of the Term, or any extended term,
Landlord may show the Premises to prospective tenants.  In the event of an
emergency, if Tenant's representative shall not be present when such an entry by
Landlord is necessary or permitted hereunder, Landlord may enter by means of a
master key or may, after  reasonable attempts to notify Tenant, enter forcibly
without liability to Tenant, except for any failure to exercise due care for
Tenant's property.  Landlord shall neither be deemed guilty of an

                                       15
<PAGE>

eviction or disturbance of Tenant's use and possession of the Premises nor shall
Landlord be liable to Tenant in any manner on account of any entry permitted
hereunder.

     15.  Inability to Perform.  This Lease and the obligations of Tenant
          --------------------
hereunder shall not be affected because Landlord is unable to fulfill any of its
obligations hereunder or is delayed in doing so, if such inability or delay is
caused by reason of any cause beyond the control of Landlord.

     16.  Indemnification.
          ---------------

          (a)  Indemnity by Tenant. Tenant agrees to indemnify, defend, pay, and
               -------------------
     save Landlord harmless from and against any and all claims, demands, suits,
     actions, proceedings, liability, damages, penalties, orders, decrees,
     judgments, costs and expenses arising out of (a) loss of life or injury to
     person or property sustained by anyone in and about the Premises, except
     those resulting from the affirmative act or negligence of Landlord or
     Landlord's officers, agents or employees, and (b) the use or occupancy of
     the Premises by Tenant, its agents and employees in or on the Premises and
     the approaches thereto, or arising or alleged to have arisen out of the
     acts or omissions of Tenant's officers, agents, employees, or invitees and
     Tenant shall, at its own cost and expense, defend any and all suits or
     actions which may be brought against Landlord or to which Landlord may be
     made a party upon any such claims.  Except for the affirmative act or
     negligence of Landlord, its agents, servants or employees, all of Tenant's
     property upon the Premises shall be there at Tenant's sole risk, and
     Landlord shall not be responsible or liable for any damage or injury to any
     property, fixtures equipment or furniture, or to any person or persons, at
     any time upon the Premises.

          (b)  Indemnity by Landlord. Landlord agrees to indemnify, defend, pay,
               ---------------------
     and save Tenant harmless from and against any and all claims, demands,
     suits, actions, proceedings, liability, damages, penalties, orders,
     decrees, judgments, costs and expenses arising out of loss of life or
     injury to person or property sustained by anyone on the Common Areas or the
     Building (exclusive of the Premises), but only to the extent Tenant is not
     liable to indemnify Landlord pursuant to Section 16(a) hereof and only
     during such period as same are under the control of and are being
     maintained by Landlord, except those resulting from the affirmative act or
     negligence of Tenant or Tenant's officers, agents or employees, and
     Landlord shall, at its own cost and expense, defend any and all suits or
     actions which may be brought against Tenant or to which Tenant be made a
     party upon any such claims.  Except for the affirmative act or negligence
     of Tenant, its agents, servants or employees, all of Landlord's property
     upon the Common Areas or the Building (exclusive of the Premises) shall be
     there at Landlord's sole risk, and Tenant shall not be responsible or
     liable for any damage or injury to any property, fixture or Buildings, or
     to any person or persons, at any time upon the Common Areas or the Building
     (exclusive of the Premises). Tenant releases Landlord from all liability
     for any damage to property entrusted to employees of the Building, and for
     injury to persons or for loss of or damage to any property by theft or
     otherwise, unless caused by or due to the gross negligence of Landlord, its
     agents, or employees.  Neither Landlord nor its agents shall be

                                       16
<PAGE>

     liable for interference with light or other intangible rights, nor for any
     latent defect in the Premises or in the Building.

          (c)  Notification of Claims.  Each party hereto shall promptly notify
               ----------------------
     the other of any claim asserted against such party with respect to which
     such party is indemnified against loss by the other party hereunder, and
     the party giving such notice shall promptly deliver to the other party the
     original or a true copy of any summons or other process, pleading, or
     notice issued or served in any suit or other proceeding to assert or
     enforce any such claim.  The party so notified shall, as set forth above,
     defend any such suit at its sole cost and expense with experienced and
     competent attorneys of its own selection, but the party so indemnified
     shall have the right, if it sees fit, to participate in such defense at its
     own expense.

     17.  Rights of Landlord. Landlord reserves the following rights: (a) to
          ------------------
change the name of the Building without notice or liability to Tenant; (b)  to
designate all sources furnishing sign painting or lettering and restroom
supplies used on the Premises; (c) if Tenant vacates the  Premises at any time
during the last ninety (90) days of the Term, to decorate, remodel, repair,
alter or otherwise prepare the Premises for reoccupancy; (d) to maintain pass
keys to the Premises; (e) to grant to anyone the exclusive right to conduct any
particular business in the Building; provided that such exclusive right does not
restrict Tenant's allowed uses of the Premises, as provided by this Lease; and
(f) at any time, at Landlord's expense, to decorate or make repairs,
alterations, additions or improvements, in or to the Building or any part
thereof, including the Premises, including  specifically the right to alter,
improve or rebuild the Common Areas and Facilities.  Except where resulting from
the gross negligence of Landlord, Landlord shall not be liable to Tenant for any
expense, injury, loss or damage resulting from any work so done in or about the
Premises or the Building.

     In connection with making repairs, alterations or additions hereunder,
Landlord shall have the right to post necessary notices on the Premises, and
shall have right of access through the Premises, as well as the right to take
materials that may be required to perform the foregoing into and through the
Premises, as well as the right in the course of such work to close entrances,
doors, corridors, elevators, or other Building facilities or temporarily to
abate the operations of such facilities, without being deemed or held guilty of
an eviction of Tenant and without liability to Tenant.   Rent shall not abate
while the foregoing is being performed and Tenant shall not be entitled to
maintain any offset or counterclaim for damages of any kind against Landlord by
reason thereof, all such claims being hereby expressly released by the Tenant.
All such work shall be done in such manner as to cause Tenant the least
inconvenience practicable

     18.  Assignment and Subletting. Tenant shall not, without the prior written
          -------------------------
consent of Landlord assign, convey, mortgage or sublet this Lease or any
interest herein, or allow any transfer hereof. Any assignment, conveyance,
mortgage or sublease shall be subject to terms and conditions acceptable to
Landlord.  As provided in Paragraph 64 hereof, the location of equipment of co-
locators on the Premises shall not be considered an assignment or subletting of
the Premises and shall not be subject to a Percentage Payment (as defined
hereinafter) so long as such contracts do not purport to lease any part of the
Premises or assign any interest in this Lease.

                                       17
<PAGE>

     Notwithstanding anything to the contrary contained in the preceding
paragraph, Tenant may assign this Lease or sublease the Premises without
Landlord's consent to any entity which controls, is controlled by or is under
common control with Tenant or any entity resulting from any merger or
consolidation with Tenant ("Affiliate"), provided at the time of such transfer
Tenant is not in default hereunder, such assignee assumes all of the terms and
conditions of this Lease, and that Tenant is not released or relieved of any
liability hereunder.

The following shall apply in the case of an approved assignment or sublease:

          (a)  Tenant shall pay to Landlord as Rent under this Lease 75% of the
     Profit (the "Percentage Payment") on such transaction, except for
     assignments and subleases to an Affiliate as and when received by Tenant,
     unless Landlord gives written notice to Tenant and the assignee or
     subtenant that the Percentage Payment shall be paid by the assignee or
     subtenant to Landlord directly.  The "Profit" means (A) all amounts paid to
     Tenant for such assignment or sublease, including monthly rent in excess of
     the monthly rent payable under this Lease, and all fees and other
     consideration paid for the assignment or sublease, including fees under any
     collateral agreements, less (B) costs and expenses directly incurred by
     Tenant in connection with the execution and performance of such assignment
     or sublease for real estate broker's commissions, the cost of lease
     concession, legal fees, and costs of renovation or construction of tenant
     improvements required under such assignment or sublease.  Tenant is
     entitled to recover such costs and expenses before Tenant is obligated to
     pay the Percentage Payment to Landlord.  The Profit in the case of a
     sublease of less than all the Premises is the rent allocable to the
     subleased space as a percentage on a square footage basis.

          (b)  Tenant shall provide Landlord a written statement certifying all
     amounts to be paid from any assignment or sublease of the Premises within
     thirty (30) days after the transaction documentation is signed, and
     Landlord may inspect with prior written notice Tenant's books and records
     to verify the accuracy of such statement.  On written request, Tenant shall
     promptly furnish to Landlord copies of all the transaction documentation,
     all of which shall be certified by Tenant to be complete, true and correct.
     Landlord's receipt of the Percentage Payment shall not be a consent to any
     further assignment or subletting.

     19.  Damage or Destruction.  If the Premises or the Building are damaged by
          ---------------------
fire or other casualty insured under policies of insurance carried by Landlord,
the damage to the Building shall be diligently repaired by and at the expense of
Landlord and the damage to the Premises shall be diligently repaired by and at
the expense of Landlord and Tenant to the extent of their respective obligations
to maintain and repair the Premises pursuant to paragraph 11 hereof, provided
such repairs can, in Landlord's opinion, be made within fifteen (15) days after
the  occurrence of such damage without the payment of overtime or other
premiums.   There shall be no abatement of Rent by reason of any portion of the
Premises being unusable for a period of fifteen (15) days or less.  If the
damage is due to the fault or neglect of Tenant or its employees, agents, or
contractors there shall be no abatement of Rent.

                                       18
<PAGE>

     If repairs cannot be made, in Landlord's reasonable, opinion within the
fifteen (15) day period and without the payment of overtime or other premiums,
Landlord shall have a reasonable time to make the repairs provided that Landlord
has given Tenant a notice within ten (10) days after the incident causing the
damage giving the estimated time to repair.  In such event the Rent shall be
prorated for the period and to the extent the Premises are not able to be used
by Tenant

     If the damage to the Building disrupts Tenant's switch operations and
cannot be repaired by Landlord following telephonic notice to Landlord within 24
hours from the time of such telephonic notice, Tenant shall have the option but
not the obligation to perform such repairs to the Building necessary or
advisable to get its switch facility in operation at Tenant's sole cost and
expense. If such repairs by Tenant are repairs that would have had to be made by
Landlord pursuant to its repair obligations, Landlord shall reimburse Tenant for
the reasonable cost of such repairs, but only to the extent Landlord would have
incurred such expense(s) to complete such repairs.

     A total destruction of the Building in which the Premises are located shall
automatically terminate this Lease.

     20.  Eminent Domain.  If the Premises, or so much thereof as to render the
          --------------
balance unusable for the Permitted Use, shall be taken under power of eminent
domain, this Lease shall automatically terminate as of the later of the date of
such condemnation, or the date possession is taken by the condemning authority,
or as otherwise herein provided.  In the event of a partial taking, Tenant, at
its sole discretion, may elect to continue its occupancy in the remaining
portion of the Premises and Base Rent will be proportionately adjusted.
Landlord will retain any award which may be made in such taking or condemnation
as such relates to the Building including, but not limited to, all fee,
leasehold and easement estates in the land upon which the Building and the
Premises is located.  Tenant will receive any and all awards as such relate to
Tenant's loss of business, Tenant's furniture, fixtures and equipment, Tenant's
improvements to the Premises, and other items as such related to Tenant.  In the
event of a partial taking which does not result in a termination of this Lease,
Base Rent shall be proportionately adjusted.  Landlord may without any
obligation or liability to Tenant stipulate with any condemning authority for a
judgment of condemnation, and the date of taking under this clause shall then be
deemed the date agreed to under the terms of said stipulation.

     21.  Default.  The occurrence of any of the following shall constitute an
          -------
event of Default:

          (a)  The vacation, abandonment or desertion of the Premises by Tenant,
     except that if Tenant vacates but continues to pay Rent for the Premises
     through the remainder of the Term, said vacation will not be considered an
     event of Default.

          (b)  A failure by Tenant to have made any payment of Base Rent or
     Adjusted Base Rent by the tenth day following receipt of written notice by
     Tenant from Landlord of such failure to have made such payment of Base Rent
     or Adjusted Base Rent; provided,

                                       19
<PAGE>

     however, that Landlord shall not be obligated to give Tenant written notice
     of such failure more than twice in any calendar year.

          (c)  A failure by Tenant to observe or perform any provision of this
     Lease for fifteen (15) days after notice thereof from Landlord; provided
     that if such Default cannot reasonably be cured within such period, and
     Tenant promptly commences to cure such Default and thereafter diligently
     prosecutes the same to completion, Tenant shall not be deemed in Default.

          (d)  The making by Tenant of any general assignment for the benefit of
     creditors, or the attachment, execution or other judicial seizure of
     substantially all of Tenant's assets located at the Premises or of
     Tenant's interest in this Lease.

     If an event of Default shall occur, Landlord may, at any time:

               (i)  re-enter the Premises and take possession thereof and,
          subject to the provisions of the Landlord's Waiver and the provisions
          of Section 10 of the Lease, of all property of Tenant therein and
          remove Tenant and all other parties from the Premises without
          terminating this Lease, and at any time relet the Premises, or any
          part thereof, upon such conditions and at such rental as Landlord
          deems proper. In such event Landlord may receive and collect the rent
          from such reletting and apply it against any amounts due from Tenant
          hereunder, (plus expenses Landlord incurs in recovering possession of
          the Premises, placing the same in good condition, preparing the same
          for reletting, and all other related expenses, commissions and
          charges). Rent or other charges collected from a tenant to whom the
          Premises have been relet shall be applied to reduce any indebtedness
          due hereunder. Landlord shall not be deemed to have terminated this
          Lease or the liability of Tenant for the total liability hereunder by
          re-entry or any other act unless Landlord shall have specifically
          notified Tenant of Landlord's election to terminate this Lease.

               (ii) give written notice to Tenant of Landlord's election to
          terminate this Lease. In such event Landlord may recover from Tenant
          all damages related to Tenant's Default, including reasonable
          attorneys' fees, and in lieu of the damages that may be recoverable
          under subparagraph (i) above, Landlord shall be entitled to liquidated
          damages in an amount equal to the Rent reserved hereunder for the
          period which otherwise would have constituted the balance of the Term,
          discounted at the rate of the weekly average yield of U.S. Treasury
          Securities having a maturity date nearest to the expiration of the
          Term (including any exercised renewal term) as published in the
          Federal Reserve Statistical Release H.15 (519) or its successor, less
          the amount of the rental loss for the unexpired period of the Lease
          that could have been reasonably avoided by Landlord.

     22.  Rules and Regulations.  Tenant shall comply with the Rules and
          ---------------------
Regulations attached hereto, and such other rules and regulations as Landlord
may adopt from time to time.  Landlord shall not be liable to Tenant for the
breach of any lease by any other tenant in the

                                       20
<PAGE>

Building. Notwithstanding anything contained in this Paragraph 22, in the event
there is a conflict between the provisions of the Lease (and all Riders or
Exhibits thereto) and the Rules and Regulations, the provisions of the Lease
will prevail.

     23.  Requirements of Law.  Tenant shall, at its sole cost and expense,
          -------------------
promptly comply with all laws, orders, regulations and requirements of all
public authorities and any fire underwriters insurance rating agency or similar
organization which may impose any violation, order or duty upon Landlord or
Tenant with respect to the Premises, or with respect to the Building if arising
out of Tenant's use of the Premises.  Tenant  shall pay all costs, expenses,
fines, penalties or damages which may be imposed upon Landlord by reason of
Tenant's failure to comply with the provisions of  this paragraph.
Notwithstanding anything contained in this Paragraph 23, Tenant will not be
responsible or liable for violations that are not as a result of Tenant or
Tenant's use.  Any expenses incurred by Landlord related to any legal
requirements enacted after the Commencement Date that are capital expenses shall
be amortized as an Operating Expense as provided by Paragraph 1(p)(iv).

     24.  Surrender of Premises.  At the termination of this Lease Tenant shall
          ---------------------
surrender the Premises (and all keys thereto) to Landlord in good condition,
reasonable wear and tear excepted. Tenant shall remove its trade fixtures,
personal property and signs within ten (10) days after termination, Landlord
shall have the right to remove and store said property, at Tenant's expense,
without further notice to or demand upon Tenant. Tenant shall be responsible for
any and all charges and expenses incurred by Landlord for any damages that
result from the removal of such trade fixtures, personal property and signs.
Tenant hereby indemnifies Landlord against all losses, costs, damages,
liabilities and expenses resulting from Tenant's failure or delay in
surrendering the Premises, including, without limitation, claims made by any
succeeding tenant founded on such delay.  Tenant's  obligations under this
paragraph shall survive the Term.

     25.  Quiet Enjoyment. Tenant, upon paying the Rent and performing the other
          ---------------
conditions, covenants, and agreements of this Lease, shall peaceably and quietly
have, hold and enjoy the Premises during the Term, without any hindrance from
Landlord or any person or persons claiming by, through or under Landlord,
subject to the terms of this  Lease, and to any mortgages, ground or underlying
leases, agreements and  encumbrances to which this Lease is or may be
subordinated.

     26.  Landlord's Lien.  INTENTIONALLY OMITTED.
          ---------------

     27.  Liens.  Tenant shall do all things reasonably necessary to prevent the
          -----
filing of any lien against the  Building or the interest of the Landlord or any
underlying lessor therein or the interest of any mortgagee or holder of any deed
of trust covering the Building by reason of any services claimed to have been
performed or materials claimed to have been supplied to Tenant, or anyone
holding the Premises, or any part thereof, through or under Tenant.  Tenant
shall cause such lien to be vacated and canceled of record within  thirty (30)
days after the date of the filing thereof.  If Tenant shall fail to timely
vacate or release such lien Landlord may do so, and Tenant shall repay to
Landlord all expenses, including reasonable attorneys' fees, incurred in
connection therewith.

                                       21
<PAGE>

     28.  Insurance.
          ---------

          (a)  Liability Insurance Carried by Tenant. Tenant shall obtain and
               -------------------------------------
     keep in force during the Term Commercial General Liability insurance
     protecting Tenant and Landlord (as an additional insured) against claims
     for bodily injury, personal injury and property damage based upon,
     involving or arising out of the use, occupancy or maintenance of the
     Premises and all areas appurtenant thereto. Such insurance shall be on an
     occurrence basis providing single limit coverage in an amount not less than
     $1,000,000 per occurrence with an "Additional Insured-Managers or Landlords
     of Premises" Endorsement and shall contain an amendment to the Pollution
     Exclusion to cover damage caused by heat, smoke or fumes from a hostile
     fire. The limits of said insurance shall not serve to limit the liability
     of Tenant or relieve Tenant of any obligation hereunder. All insurance to
     be carried by Tenant shall be primary and not contributory with any similar
     insurance carried by Landlord, whose insurance shall be considered excess
     insurance only.

          (b)  Liability Insurance Carried by Landlord. Landlord shall maintain
               ---------------------------------------
     property insurance covering the Building and Commercial General Liability
     Insurance in limits and with coverage generally deemed acceptable within
     the real estate industry. Landlord's insurance coverage shall be excess
     over Tenant's coverage required hereunder and Tenant shall not be named as
     an additional insured therein.

          (c)  Tenant's Property Insurance. Tenant shall maintain insurance
               ---------------------------
     coverage on all of Tenant's personal property, and Tenant alterations in
     the Premises. Such insurance shall be full replacement cost coverage with a
     deductible not to exceed $25,000 per occurrence. The proceeds from such
     insurance shall be used by Tenant for the replacement of personal property
     or the restoration of Tenant alterations. Tenant shall provide Landlord
     with written evidence that such insurance is in force.

          (d)  Insurance Policies.  Insurance required hereunder shall be with
               ------------------
     companies licensed to transact business in the state where the Premises are
     located, and maintaining during the policy term an "A.M. Best Rating" of at
     least A-VII as set forth in the most current issue of "Best's Insurance
     Guide." Tenant shall not permit anything which could invalidate the
     insurance policies referred to herein. Tenant shall deliver to Landlord
     certificates evidencing the existence and amounts of insurance required
     hereunder, listing the insureds and loss payable clauses required by this
     Lease. Such policy shall be cancelable or subject to modification only
     after thirty (30) days written notice to Landlord. At least ten (10) days
     prior to the expiration of such policies, Tenant shall furnish Landlord
     evidence of renewal thereof. In the event Tenant fails to do so, Landlord
     may order such insurance and charge the cost thereof to Tenant as Rent.

     29.  Waiver of Subrogation. Without affecting any other rights or remedies,
          ---------------------
Tenant and Landlord each hereby release and relieve each other, and waive their
right to recover damages against the other, for loss of or damage to the other
party's property arising out of or incident to the perils required to be insured
against under Paragraph 28. The effect of such release and waivers of

                                       22
<PAGE>

the right to recover damages shall not be limited by the amount of insurance
carried or required, or by any deductibles applicable thereto.

     30.  Waiver.  No waiver by Landlord of any provision of this Lease or
          ------
Landlord's consent to any act shall render unnecessary the obtaining of
Landlord's consent to or waiver of any subsequent act of Tenant or provision of
this Lease.  No agreement to accept a surrender of the Premises shall be valid
unless in writing and signed by two (2) officers of Landlord.

     31.  Unavoidable Delays.  If Landlord or Tenant (other than as to Tenant's
          ------------------
obligation to pay Rent) shall fail to timely perform any of its obligations as a
result of any labor disputes, inability to obtain labor or materials, acts of
God, governmental restrictions, regulations or controls, enemy or hostile
government action, civil commotion, fire or other casualty, or any other
condition beyond the reasonable control of the party obligated to perform, then
such failure shall not be deemed a breach of this Lease to the extent of and for
the time occasioned by such event. Lack of funds and inability to procure
financing shall not be deemed to be an event beyond the reasonable control of
Tenant.  As a condition precedent to Tenant claiming or relying upon an
unavoidable delay, Tenant shall give ten (10) days written notice to Landlord of
such event.

     32.  Subordination.  This Lease is, unless Landlord shall otherwise elect,
          -------------
subject and subordinate to all covenants, restrictions, easements and
encumbrances now affecting the fee title to the Building and to all ground and
underlying leases and mortgages or financings (including leasehold mortgages or
financings) which have been placed against or affect the real property of which
the Premises forms a part, and subject and subordinate all covenants,
restrictions, easements, encumbrances and to all ground and underlying leases
and mortgages and financings (including leasehold mortgages or financings) which
may hereafter affect title to the Building and  to the real property of which
the Premises forms a part provided that in the case of any encumbrance placed
against the Building or the real property of which the Premises form a part from
and after the date of this lease, this Lease shall only be subordinate if
Landlord provides Tenant with a signed and acknowledged Landlord's Waiver in the
form of Exhibit "B" hereto and a Subordination, Non-Disturbance and Attornment
Agreement in the form of Exhibit "C" hereto.  The term "mortgages" as used
herein shall include trust indentures and deeds of trust.  No further instrument
shall be necessary unless required by any such ground or underlying lessor or
mortgagee.  Should any ground or underlying lessor or mortgagee lease and/or
mortgage the real property of which the Premises forms a part, or any part
thereof, or should Landlord or any  ground or underlying lessor or mortgagee for
any other reason desire confirmation of such subordination, Tenant shall execute
and deliver, without charge, all documents (in form acceptable to such ground or
underlying lessor or mortgagee) subordinating this Lease and Tenant's rights
hereunder within ten (10) days of Landlord's written request therefor.

     33.  Notice to Mortgagee.  Tenant shall not exercise any right to terminate
          -------------------
this Lease by reason of constructive or actual eviction, or in the event of any
act or omission by Landlord which would give Tenant the right to terminate this
Lease, until (i) Tenant shall have given written notice of such act or omission
to the holder of any first mortgage to which this Lease is subject and
subordinate (provided the name and address of such holder shall previously have
been furnished to Tenant) and (ii) a reasonable period of time for remedying
such act or omission shall have elapsed

                                       23
<PAGE>

following the giving of such notice, during which Landlord and/or the holder of
such mortgage, or their agents or employees, shall be entitled to enter the
Premises and remedy such act or omission. During the period between the giving
of such notice and the remedying of such act or omission, Rent shall be abated
and apportioned to the extent that any part of the Premises shall be
untenantable.

     34.  Attornment.  In the event of a sale, transfer, or assignment of
          ----------
Landlord's interest in the Building or any part thereof, or in the event of any
proceedings brought for the foreclosure of, or in the event of the exercise of
any power of sale under any mortgage covering the Building or any part thereof,
or in the event of a cancellation or termination of any ground or underlying
lease covering the Building or any part thereof, Tenant will attorn to and
recognize such transferee, purchaser, ground or underlying lessor or mortgagee
as Landlord, so long as such terminating party recognizes and upholds this
Lease.

     35.  Estoppel Certificate.
          --------------------

          (a)  Tenant shall, upon not less than ten (10) days' written notice
     from Landlord, execute, acknowledge and deliver to Landlord a statement (i)
     certifying that this Lease is unmodified and in full force and effect (or,
     if modified, stating the nature of such modification and certifying that
     this Lease, as so modified, is in full force and effect) and the dates to
     which Rent has been paid, and (ii) acknowledging that there are not, to
     Tenant's knowledge, any uncured defaults on the part of Landlord hereunder,
     or specifying such defaults, if any.

          (b)  Tenant's failure to deliver such statement within ten (10) days'
     of written notice from Landlord shall be conclusive upon Tenant (i) that
     this Lease is in full force and effect, without modification except as may
     be represented by Landlord, (ii) that there are no uncured defaults in
     Landlord's performance, and (iii) that not more than one month's rental has
     been paid in advance.

     36.  Interest on Past Due Obligations.  If Tenant shall fail to pay any
          --------------------------------
Rent after the same becomes due and payable, including bank drafts returned
unpaid, such unpaid amounts shall bear interest from the due date thereof to the
date of receipt of payment at the lesser of eighteen percent (18%) per annum, or
such other rate as is the highest legal rate of interest chargeable in the state
where the Building is located.

     37.  Transfer of Landlord's Interest.  In the event of any transfer of
          -------------------------------
Landlord's interest in the Premises or in the real property of which the
Premises is a part, the transferor shall be automatically relieved of any and
all obligations and liabilities on the part of Landlord accruing from and after
the date of such transfer.

     38.  Holding Over.  If Tenant shall hold over beyond the Termination Date
          ------------
with the consent of Landlord, such holding over shall be construed to be a
month-to-month tenancy, terminable by either party at the end of the month
following at least thirty (30) days' written notice, and shall be subject to all
the terms and conditions of this Lease (so far as same are applicable to a

                                       24
<PAGE>

month-to-month tenancy) except Paragraph 1(i) of the Lease shall be amended to
redefine Base Rent as the amount, payable monthly, in advance, equal to the
greater of 1)twice the monthly installment of Base Rent or 2)the then prevailing
market rental rate for the Building or 3) the then prevailing market rental rate
for buildings of similar character in the general location of the Building.

     39.  Relocation.  INTENTIONALLY OMITTED.
          ----------

     40.  Accord and Satisfaction. Payment by Tenant or receipt by Landlord of a
          -----------------------
lesser amount than that stipulated herein for Rent shall, at the option of
Landlord, be deemed to be on account of the earliest stipulated Rent then due.
No endorsement or statement on a check or letter accompanying any check or
payment shall be deemed an accord and satisfaction; Landlord may accept such
check or payment without prejudice to Landlord's right to recover the balance of
such Rent or to pursue any other remedy in this Lease or at law.

     41.  Attorneys' Fees.  In the event that Landlord should bring suit for
          ---------------
possession of the Premises, for recovery of Rent, or because of the breach of
any provision of this Lease, or in the event that Tenant shall bring any action
for or against Landlord arising out of this Lease, then all costs and expenses,
including reasonable attorneys' fees, incurred by the prevailing party therein
shall be paid by the other party.

     42.  Fees or Commissions. The parties, warrant and represent that to the
          -------------------
best of their knowledge, other than the Broker defined at Paragraph 1(t) hereof,
there are no claims for broker's commissions or finder's fees in connection with
this Lease, and the misrepresenting party agrees to indemnify and hold the other
harmless from any liability which arises from any such claim.

     43.  Building Name; Relationship.  Tenant shall not use the name of the
          ---------------------------
Building for any purpose other than as the address of the business or profession
to be conducted by Tenant in the Premises.  Nothing contained in this Lease
shall be deemed to create any relationship other then that of Landlord and
Tenant.  Landlord reserves the right to change the name of the Building without
the consent of Tenant and without incurring any liability to Tenant therefor.

     44.  Partial Invalidity.  If any provision of this Lease shall be held
          ------------------
void or invalid, the remainder of this Lease shall not be affected thereby, and
each provision of this Lease shall be valid and enforced to the fullest extent
permitted by law.

     45.  Notices. Every notice to be given under this Lease shall be in writing
          -------
and shall be sent by Certified or Registered Mail, postage prepaid, return
receipt requested, or by overnight courier, and shall be addressed: (a) if to
Landlord, to Landlord's Mailing Address, and (b) if to Tenant, to Tenant's
Mailing Address. Notice shall be deemed given when received or refused by the
addressee.  Either party may designate, by written notice to the other party,
any other address for notice purposes. Either party hereto may give the other
notice of the need for emergency repairs by telephone or fax, provided such
notice is promptly confirmed in writing, as set forth above.

                                       25
<PAGE>

     46.  Time of Essence. Time is of the essence with respect to the
          ---------------
performance of every provision of this Lease.

     47.  Entire Agreement; Miscellaneous.
          -------------------------------

          (a)  This Lease, the exhibits and addenda, if any, attached hereto,
     contain all of the agreements and understandings between the parties.

          (b)  All prior conversations or writings between the parties hereto or
     their representatives are merged herein.

          (c)  This Lease shall not be modified except in writing signed by both
     parties.

          (d)  The submission of this Lease to Tenant prior to Landlord's
     execution shall be deemed solely for Tenant's consideration. Such
     submissions shall have no binding force or effect, shall not constitute an
     option for the leasing of the Premises by Tenant and shall not confer any
     rights or impose any obligations upon either party.

          (e)  Any exhibit incorporated into this Lease which is inconsistent
     with any printed provision of this Lease shall supersede such printed
     provision only to the extent of such inconsistency.

          (f)  The captions appearing herein are not intended to define, limit,
     or describe the intent of any paragraph.

          (g)  Tenant agrees that Landlord may submit a copy of this Lease to
     its lender without obtaining the prior consent of Tenant.

     48.  Corporate Tenant.  The persons executing this Lease warrant that, if
          ----------------
signing on behalf of a corporation, such corporation is duly organized or
qualified (if foreign) under the laws of, and is authorized to do business in,
the state where the Building is located, and that each such person executing
this Lease is authorized to sign and execute this Lease.

     49.  Successors and Assigns.  Except as otherwise provided in this Lease,
          ----------------------
all of the conditions, covenants, and agreements of this Lease shall be binding
upon and shall inure to the benefit of the parties hereto and their respective
heirs, personal representatives, successors and assigns. Each provision of this
Lease to be performed by Tenant shall be construed as both a covenant and a
condition, and if Tenant shall be comprised of more than one individual and/or
entity, they shall all be bound, jointly and severally, by the provisions of
this Lease.

     50.  Annual Financial Statement. Tenant agrees to submit to Landlord within
          --------------------------
fifteen (15) days of Landlord's written request, the most recent public
financial statement of Tenant, and of Tenant's Guarantor, if applicable.

     51.  UCC Filing.  INTENTIONALLY OMITTED.
          ----------

                                       26
<PAGE>

     52.  Hazardous Material.  Prior to delivery of the Premises to Tenant,
          ------------------
Landlord shall remove and/or remediate any asbestos or other hazardous materials
situated on the Premises that is mandated to be removed by any governmental
entity or agency at Landlord's sole cost and expense. Thereafter, Tenant shall
not cause or permit any Hazardous Material, as defined below, to be brought
upon, kept, stored, utilized, disposed of or used in the Building by Tenant or
its agents, employees, contractors or invitees. Notwithstanding the foregoing,
Tenant may cause or permit diesel fuel or batteries necessary for Tenant's
Special Improvements to be brought upon, kept, stored, utilized or used in the
Premises by Tenant and its authorized agents, employees, contractors or invitees
provided that Tenant causes such materials to be at all times properly stored
and lawfully used. This restriction shall survive the termination or expiration
of this Lease. If the presence of Hazardous Material on the Premises is caused
or permitted by Tenant or its agents, employees, contractors or invitees and
results in contamination of the Premises or the Building, then Tenant shall
indemnify, defend and hold Landlord and any owner of the property wherein the
Premises are located harmless from all claims, judgments, damages, penalties,
fines, costs, liabilities or losses (including, without limitation, diminution
in value of the Building, damages for the loss or restriction on use of rentable
or usable space or of any amenity of the Building, damages arising from any
adverse impact on marketing of space in the Building, and sums paid in
settlement of claims, attorneys' fees, consultant fees and expert fees) which
arise during or after the Term as a result of such contamination. This
indemnification of Landlord by Tenant includes, without limitation, costs
incurred in connection with any investigation of site conditions, and clean-up,
remedial, removal or restoration work required by any federal, state or local
governmental agency or political subdivision. If the Hazardous Material results
in contamination of any part of the Building, Tenant shall promptly take all
actions at its own expense as are necessary to remediate, provided that
Landlord's approval of such remedial action shall first be obtained.

     The term "Hazardous Material" shall include hazardous or toxic materials,
wastes and substances which are defined, determined or identified as such
pursuant to present and future federal, state or local laws, rules or
regulations and judicial or administrative interpretation thereof. Standard
cleaning and materials and office equipment supplies for use in the normal
course of business shall not be deemed Hazardous Materials hereunder.  Upon
reasonable notice, Landlord and its agents shall have the right to inspect the
Premises to determine whether Tenant is in compliance with this paragraph 52.

     53.  Consent.  In each instance where consent or approval is required, such
          -------
consent or approval shall not be unreasonably withheld or delayed.

     54.  Construction Allowance for Tenant's Work.  Landlord shall reimburse
          ----------------------------------------
Tenant for the cost of Tenant's construction delineated in Tenant's working
plans (hereafter "Tenant's Work") in the amount and manner hereinafter provided
in this Paragraph, the amount of such reimbursement hereinafter referred to as
"Tenant's Construction Allowance".  It is understood and agreed that Tenant's
Construction Allowance shall cover only the cost of Tenant's Work. Tenant's
Construction Allowance shall not exceed $25.00 per rentable square foot or the
actual cost of Tenant's work as evidenced by paid receipts therefor, whichever
is the lesser amount. Tenant's Work shall include, but not be limited to, the
following at Tenant's sole cost and expense:

                                       27
<PAGE>

     .    Flooring, bathrooms, kitchen, raised floor, lighting and electrical
          and other physical improvements;

     .    Installation of a gas FM 200 and a preaction fire suppression system
          independent of the Building's fire suppression system, as approved by
          municipal fire codes, for the switch area.

     .    Relocation of any wet pipes, including water, waste water, storm
          drainage sanitary sewer, within the Premises or adjacent walls or
          ceiling to protect its equipment as reasonably approved by Landlord.

     .    The installation (instruct compliance with Landlord's roof warranty)
          of approximately 220 tons of HVAC using a chilled water system with
          four fan package units, in a location to be determined by Tenant and
          Landlord, subject to Landlord's review and approval.

     .    Installation of up to 1250 KW generator with an approximately 3000
          gallon fuel tank (with suitable walls and baffles) in an area to be
          determined by Tenant and Landlord, subject to reasonable approval of
          Landlord, at no charge to Tenant for the space occupied by the
          generator.

     Landlord shall pay Tenant's Construction Allowance to Tenant as follows:

     (a)  Fifty Percent (50%) upon Tenant's submission to Landlord of:

          (1)  Copies of invoices from contractors evidencing amounts paid for
     Tenant's Work (Landlord shall keep such invoices confidential);

          (2)  Waiver of Lien with respect to the Premises executed by every
     contractor, subcontractor, including sole proprietorships, and material
     suppliers engaged in or supplying labor or materials for Tenant's Work
     valued in excess of $5,000.00.  The waivers of lien shall not be required
     if Tenant obtains a lien bond in the amount required by statute to protest
     Landlord from mechanic's liens arising from Tenant's work.

     (b)  Fifty Percent (50%) upon Tenant's notice to Landlord that Tenant's
Work has been completed as certified by Tenant's architect, and Tenant's
affidavit that Tenant's Work has been completed to its satisfaction and in
substantial compliance with the working plans and Tenant's construction
requirement

          (1)  Copies of invoices from contractors evidencing amounts paid for
     Tenant's Work (Landlord shall keep such invoices confidential);

          (2)  A Waiver of Lien and an affidavit of the general contractor
     performing Tenant's Work stating that Tenant's Work has been fully
     completed in accordance with

                                       28
<PAGE>

     the working plans and that all contractors, subcontractors, laborers and
     material suppliers have been paid in full; and

          (3)  A Waiver of Lien with respect to the Premises executed by every
     contractor, subcontractor, including sole proprietorships, and material
     suppliers engaged in or supplying labor or materials for Tenant's Work
     valued in excess of $5,000.00.  The waivers of lien shall not be required
     if Tenant obtains a lien bond in the amount required by statute to protect
     Landlord from mechanic's liens arising from Tenant's work.

(subject, however, to Landlord's verification that Tenant is not in default of
the Lease beyond any applicable cure periods, and that Tenant's Work has been
completed).

     If this Lease is terminated prior to the expiration of the original Term
hereof due to Tenant's Default, Tenant shall repay to Landlord the unamortized
portion of Tenant's Construction Allowance upon demand.

     55.  Antennas and Telecommunications Equipment.  Subject to approval by
          -----------------------------------------
Landlord of plans by Tenant, which approval shall not be unreasonably withheld,
Tenant may install one (1) microwave dish up to six (6) feet in diameter and a
mast containing an antenna area mast of up to 25 feet in height from the roof
surface of the Building, configured for two-way radio and GPS antenna to be
connected to the Premises with a two inch conduit and a monopole antenna
structure up to 25 feet in height from the roof surface, with related base site
cabinets requiring up to 200 square feet of roof area, inclusive of four
conduits of approximately 2" diameter each, at a location acceptable to
Landlord.  Said construction and subsequent maintenance of the antenna shall be
at Tenant's sole risk and cost and in compliance with all applicable laws and
ordinances.  Tenant agrees to indemnify and hold harmless Landlord from any
injury or damage to person or property which may result from the erection or
presence of such equipment on the roof of the Building.  Tenant agrees to
coordinate its work with Landlord's roofing contractor prior to the commencement
of any such work in order to not void Landlord's roofing warranty.  Subject to
Landlord's approval, which approval shall not be unreasonably denied, Tenant
shall have reasonable access to relevant portions of the roof for the purpose of
maintaining said equipment 24-hours per day, seven days per week.

     In the event other tenants of the Building request Tenant's
telecommunications services, Tenant shall have the right to install one 2-inch
conduit from the Premises to such tenants within the Building at Tenant's sole
cost and expense and in location(s) approved by Landlord in Landlord's sole
discretion.  Additionally, Tenant will be permitted to have reasonable access to
any "meet me" room or common communications closets or to otherwise provide
communication service to other occupants of the building.  Tenant will be
permitted to allow its customers to place telecommunications equipment in the
Premises, and this will not be deemed an assignment or subletting of the Lease.

     56.  Signs.  In accordance with and subject to plans approved by Landlord,
          -----
Tenant shall, at its own  cost and expense,  provide suitable identification
signs displaying Tenant's Trade Name, which have been approved by Landlord (such
approval shall not be unreasonable withheld, delayed

                                       29
<PAGE>

or conditioned), and which Tenant warrants it is authorized to use, of such
size, design and character as Landlord shall first approve in writing, and shall
install the same on the Building and monument sign as designated by Landlord. If
Landlord's multi-tenant pole sign located near Interstate 25 is designed to
accommodate tenant identification, Tenant will be given the opportunity to lease
a panel on the sign on the same economic terms as such panels are offered to
other tenants. Tenant will be responsible for any costs in connection therewith.
Tenant shall maintain such signs in good condition and repair. Other than such
permitted signs (subject to Landlord's reasonable approval), Tenant shall not
place or install or suffer to be placed or installed or maintain any sign upon
or outside the Premises or the Building. In the event Landlord determines that
any signs installed by Tenant in violation of this paragraph, Landlord will give
Tenant written notice of the nature of such violation, and Tenant will have
thirty (30) days to correct such violation at its own expense. In the event
Tenant has not corrected or is not diligently pursuing a correction to the
violation. Landlord shall have the right to remove any signs installed by Tenant
in violation of this paragraph and to charge Tenant for the cost of such removal
and/or any repairs necessitated thereby without liability to Tenant for such
removal.

     57.  Parking.  Landlord shall provide for Tenant's use parking spaces at a
          -------
ratio of three spaces per 1,000 rentable square feet of the Premises.  The
parties acknowledge that throughout the Term and any extensions thereto, there
shall be no charge for these parking spaces.

     58.  Expansion Option/Right of First Refusal.  Provided Tenant is not in
          ---------------------------------------
default beyond any applicable cure period, then subject to all prior existing
rights (including, but not limited to, those granted to Qwest currently
occupying the south half of the first floor of the East Anchor Building) and the
following terms, Tenant shall have the option to lease any unoccupied expansion
space on the first floor of the East Anchor Building (the "Option Space") during
the first three (3) years of the Term only as follows:

          (a)  Expansion Option.  Provided Landlord does not have a bona fide
               ----------------
     offer from a third party to lease Building space containing all or a
     portion of the East Anchor Building Option Space, Tenant shall have the
     option to lease all or a portion of the Option Space upon not less than
     sixty (60) days' notice upon the same terms and conditions contained
     herein, including parking ratio.  All non-conflicting terms and conditions
     of the Lease, as amended, shall apply to said Option Space, and the Base
     Rent for said Option Space shall be the rate per rentable square foot set
     forth in Section 1(i), payable in monthly installments, in advance.  For
     purposes of calculating Adjusted Base Rent for the Option Space, the Base
     Year shall be as set forth in Section 1(n).  Tenant shall receive a
     construction allowance at a rate per square foot equal to the original
     allowance prorated over the remaining Term of this Lease.  The Option Space
     shall be accepted by Tenant in an "as-is" condition, after Landlord
     performs Items 1, 2, 6 and 8 under Construction/Demolition as shown on
     Exhibit "E" on the Option Space, and Tenant shall perform the remainder of
     the renovation of said Option Space to meet its requirements.  Tenant's
     allowance shall be administered and distributed consistent with the terms
     and requirements of this Lease.

                                       30
<PAGE>

     Tenant agrees to execute an Amendment and Supplement of Lease in form and
     substance reasonably acceptable to Landlord confirming the exercise of the
     within option to expand, redefining the newly defined Premises, the
     redefining the newly defined Premises, the Base Rent and construction
     allowance.  Tenant may, subject to the terms and conditions of this Lease
     and Landlord's prior approval, (a) install an additional generator or
     increase the size and wattage of the original generator at Tenant's sole
     cost and expense, (b) increase the HVAC capacity for the Premises at
     Tenant's sole cost and expense, (c) install additional antennas at Tenant's
     sole cost and expense, and (d) upgrade the Building electrical system
     installed by Landlord to accommodate Tenant's electrical usage in the
     Option Space at Tenant's sole cost and expense.  Landlord shall provide the
     space for an additional transformer outside the Building to be installed by
     Tenant as a part of the Option Space's Base Rent.  The location(s) of all
     such improvements shall be approved by Landlord in Landlord's sole
     discretion.

          (b)  One Time Right of First Refusal.  If at any time during the Term
               -------------------------------
     (including the period covered by the Option set forth in the preceding
     paragraph) Landlord receives a bona fide offer from a third party to lease
     Building space containing all or a part of the Option Space, which Landlord
     intends to accept, Tenant shall have a right of first refusal to lease the
     same space as that covered in the third party's offer, upon terms which are
     equal to those offered by the third party for its entire space.  Tenant
     shall exercise said right of first refusal by giving Landlord written
     notice thereof within three (3) days from the date that Tenant receives
     written notice from Landlord stating the terms of such offer.  In the event
     Tenant elects to lease such space pursuant to its right of first refusal,
     Tenant shall execute an Amendment and Supplement modifying this Lease in
     form and substance satisfactory to Landlord, setting forth the Base Rent
     payable for said space along with such other terms and conditions as the
     parties may reasonably negotiate.  If Tenant does not choose to match a
     third party's offer and that third party takes occupancy of all or any part
     of the Option Space, Tenant's right of first refusal shall be deemed
     extinguished as to all of the Option Space.  Landlord shall not improve the
     economic terms under which such third party agrees to lease all or any part
     of the Option Space by more than 5% without first resubmitting such offer
     to Tenant as provided in this Paragraph 58(b). Nothing herein shall
     preclude Landlord from renewing or extending the tenancy of said third
     party.

     59.  Right of First Refusal.  INTENTIONALLY OMITTED.
          ----------------------

                                       31
<PAGE>

     60.  Extension Option.
          ----------------

          (a)  Tenant shall have the option, exercisable by giving written
     notice (each, a "Renewal Notice") to Landlord not less than nine (9) months
     nor more than fifteen (15) months prior to the expiration of the original
     Term of this Lease or the renewal term, to renew and extend this Lease for
     two (2) consecutive five-year renewal terms, on the same terms as this
     Lease except that the Base Rent shall be equal to the prevailing Market
     Rate (as defined below). Tenant's exercise of any renewal option shall
     become irrevocable, subject to the parties' agreement on the Market Rate
     for such renewal term, upon Landlord's receipt of the Renewal Notice.

          (b)  Within ten (10) business days of Landlord's receipt of the
     Renewal Notice, Landlord shall deliver to Tenant its determination of the
     Market Rate; and if Tenant agrees with Landlord's determination, Tenant
     shall execute an Amendment and Supplement to Lease in form and substance
     satisfactory to Landlord and Tenant, confirming the extension of this Lease
     and setting forth the Base Rent payable during such Renewal Period along
     with such other terms and conditions as Landlord may reasonably require. If
     Tenant disagrees, Landlord and Tenant shall meet and confer at a mutually
     agreeable time and place within thirty (30) days after Landlord's receipt
     of Tenant's disagreement in order to reach an agreement concerning the
     Market Rate for the Premises for the applicable renewal term. If within
     sixty (60) days after receipt of the Renewal Notice, Landlord and Tenant
     are unable to agree on what Market Rate should be for the renewal term, the
     Market Rate for such renewal term shall be determined by the appraisal
     procedure described in subparagraph (c) below.

          (c)  In the absence of an agreement between Landlord and Tenant on the
     Market Rate for any renewal term during the time period specified in
     subparagraph (b) above, within ninety (90) days after Landlord's receipt of
     the Renewal Notice, Landlord and Tenant shall have each appointed an
     appraiser to determine the Market Rate for such renewal term by giving
     written notice to the other party of the name, address and telephone number
     of their respective appraisers. Each appraiser must (i) be a commercial
     leasing broker for Class "B" office buildings in the Denver area business
     district, (ii) have at least ten years experience in commercial leasing
     brokerage in the Denver area, and (iii) not be affiliated with Landlord or
     Tenant. The appraisers shall make their determination as to the Market Rate
     for the renewal term within thirty (30) days after their appointment. If
     the Market Rate determinations of the two appraisers vary from each other
     by no more than 5%, the Market Rate for the renewal term shall be the
     average of the two determinations. If the Market Rate determinations of the
     two appraisers vary by more than 5%, the appraisers shall promptly select a
     third appraiser who meets the qualifications set forth above. Such third
     appraiser shall make its determination as to the Market Rate, and the
     Market Rate for the renewal term shall be the average of the two appraisals
     which are closest to each other. Landlord and Tenant shall share the cost
     of the third appraiser, but shall each bear their own costs in connection
     with the two appraisers they select. Landlord and Tenant agree to be bound
     by the Market Rate as determined in accordance with the appraisal procedure
     set forth herein.

                                       32
<PAGE>

          (d)  The Market Rate for any renewal term determined by Landlord and
     Tenant pursuant to subparagraph (b) above or by the appraisers selected
     pursuant to subparagraph (c) above shall be based upon the following
     criteria:

          (i)  There shall be taken into consideration the comparative rents of
               known lease agreements consummated within twelve (12) months
               prior to the applicable Renewal Notice for similar space in Class
               "B" office buildings in the northern metropolitan Denver,
               Colorado area along the Interstate 25 and Interstate 36
               corridors; and

          (ii) In determining the Market Rate for the Premises for the
               applicable renewal term, there shall be taken into account the
               comparative rents described in subparagraph (i) above, provided
               that appropriate adjustments shall be made by taking into account
               (1) differences in length of lease terms, (2) the location of the
               Building, (3) the floor level at which the Premises is located,
               (4) the age, quality and amenities of the Building, (5) tenant
               improvement allowances and free rent concessions given, and (6)
               current operating expenses and impositions for the Building.

     The option provided for herein shall be exercisable by Tenant and Tenant's
permitted assignee only and may not be assigned or transferred by operation of
law or otherwise except to a permitted assignee as part of the assignment of
this Lease.  Tenant may exercise said option on the condition that it is not in
default under the Lease beyond any applicable cure periods, and that Tenant has
not subleased or assigned all or part of the Premises.

     61.  Annex Building.  INTENTIONALLY OMITTED.
          --------------

     62.  Field Measurement upon Completion of Construction; Rental Adjustments.
          ---------------------------------------------------------------------
Upon completion of construction, Landlord shall measure the Premises hereby to
determine the number of square feet contained in the Premises, and upon the
determination of such actual square footage, the following items shall be
adjusted in the manner set forth below:

          (a)  Premises [paragraph 1(e)]: The actual number of square feet shall
     be adjusted to conform to the actual measurements of the Premises;

          (b)  Base Rent [paragraph 1(i)]: The figures set forth thereat shall
     be adjusted substituting therefor the number obtained by multiplying the
     number of rentable square feet actually contained in the Premises as
     determined aforesaid by the applicable Rental Rate set forth at Paragraph
     1(i) of the Lease:

          (c)  Tenant's Share [paragraph 1(1)]: The percentage of Tenant's Share
     shall be amended to reflect the actual percentage of Tenant's Share of the
     Building.

     All such adjustments enumerated in this paragraph 62 shall be confirmed by
an amendment and supplement to the Lease in form and substance satisfactory to
Landlord.

                                       33
<PAGE>

     The determination of the number of square feet in the Premises by Landlord
shall be final, conclusive and binding on the parties hereto for the purposes of
the Lease.

     63.  Special Tenant Improvements.  In connection with Tenant's build-out of
          ---------------------------
its Premises as set forth in Tenant's plans and specifications and Tenant's
intended use of its Premises, Landlord hereby grants Tenant the following rights
with respect to the following technical requirements (collectively with all
other improvements Tenant is entitled to make in, to and related to the Premises
the "Special Tenant Improvements"); provided, however, that in each case (i)
Tenant shall be responsible for installing, maintaining and repairing the
Special Tenant Improvements at its sole cost and expense; (ii) the Special
Tenant Improvements shall be located in the designated areas described herein;
(iii) the Special Tenant Improvements shall be installed, maintained and
repaired by qualified engineers, contractors and technicians and shall at all
times comply with all applicable laws; (iv) except as provided herein, there
shall be no additional rent and charge imposed on Tenant as a result of any
Special Tenant Improvements; and (v) the Special Tenant Improvements shall at
all times be subject to Tenant's insurance and indemnity obligations hereunder,
as well as the other terms and conditions hereof.  All of the Special Tenant
Improvements shall be and remain the property of Tenant and shall be for
Tenant's exclusive use.

          (a)  HVAC/Mechanical.  Landlord hereby grants to Tenant the right to
     install, operate, maintain, repair and replace Tenant's HVAC system,
     including a chilled water system with four fan package units with related
     mechanical equipment together with related wiring, piping, conduits, vents
     and equipment, including pipes, power conduits and control line conduits to
     and from the Premises (collectively the "Cooling Equipment") in an area not
     to exceed 2,000 square feet on the roof above the Premises as shown in
     Exhibit "F."  Such equipment will be located on a suitable structural curb
     or other roof supports (such roof supports to be provided by Landlord)
     placed directly over the vertical structural column supports in the main
     building structure.  The type of cooling equipment will be determined by
     Tenant and approved by Landlord in Landlord's sole discretion.  Tenant will
     be permitted to install (i) chilling towers along with the required supply
     and return piping for the glycol coolant loop(s) and related conduits from
     the chilling towers to and from the Premises through the permitted chases
     and risers and (ii) "package" type units, the size and number of which will
     be determined by Tenant.

          (b)  Generator.  Tenant shall be permitted at its cost to install,
     operate, maintain, repair and replace up to one 1,250 kw/480 volt diesel
     generator to be located at Tenant's option, either in the alcove directly
     north of the Public Service Transformer room or directly south of the first
     west bay of the Annex Building, provided that in the case of the first west
     bay, Tenant has constructed an enclosure around the generator area and
     installs landscaping from materials and to a design approved by Landlord.
     Such generator will have the related wiring, piping, conduits, vents and
     equipment, including up to six (6) four-inch and up to two (2) one-inch
     conduits all provided by Tenant.  In connection with such generator, Tenant
     shall also have the right to place one up to 3,000 gallon fuel tank or two
     up to 1,500 gallon fuel storage tanks in the alcove area ("Equipment Area")
     reasonably adjacent to the generator location or other mutually

                                       34
<PAGE>

     agreed upon area. This area is shown in Exhibit "H." The fuel tanks will
     comply with all laws, rules and regulations. Alternatively, the fuel tanks
     will be placed in another location as determined by Landlord. Tenant will
     have the exclusive right to use this area. Tenant may, at its option,
     demolish and remove the existing concrete floor slab in this area and
     replace it with an approximately eight-inch reinforced concrete slab.
     Tenant shall have the right to install a fuel piping system, which includes
     two 4-inch double-walled supply and return pipes from the generator to the
     fuel tanks. Tenant shall have the right to install required fuel fill lines
     and ventilation lines in locations as reasonably determined by Tenant and
     approved by Landlord which approval shall not be unreasonably withheld,
     delayed or conditioned. Tenant shall enclose the fuel tanks by constructing
     a concrete masonry unit enclosure. Tenant shall have the right to test the
     generator no less than once per week at a time mutually agreed upon between
     Landlord and Tenant and in compliance with all laws. Tenant hereby agrees
     to protect, defend, indemnify and hold harmless Landlord for the use of the
     generator and fuel storage tank and any environmental liability resulting
     therefrom and Tenant shall remove same upon the expiration of the Lease
     Term. This indemnity shall survive the expiration of the Lease Term.

     Tenant may, at its option, place the transfer switch and disconnect switch
     in the Equipment Area along with related piping, conduits and equipment.
     Tenant specifically will have the option to place a portion of its
     equipment, including the transfer switch, in the approximately 30 foot by
     30 foot room in the Southwest corner of the Annex Building, currently
     identified as the "Wards Battery Room."  The square footage of said space
     is 981 rental square feet and the rental rate for such space shall be as
     set forth in Section 1(i) and shall be an addition to Base Rent.

          (c)  Temporary Generator.  Until a permanent generator is installed,
     Tenant shall have the right to install and operate a temporary generator in
     an area adjacent to the Premises to protect Tenant's business from risks
     attendant to power failure to the Building.

          (d)  Telecommunications Connectivity.  Tenant will have the right to,
     at its sole cost and expense, install two service vaults (may be installed
     underground in the parking lots), on the north and south sides of the
     Building, in location(s) approved by Landlord in Landlord's sole
     discretion, by trenching in areas as required, including the parking lots,
     sidewalks, landscaping, curbing and other common areas so long as Tenant
     replaces and repairs the same after completing the installation.  Tenant
     will have the right to connect its required conduit into the building and
     the Premises through penetrations in the exterior of the Building at
     locations to be determined by Landlord and Tenant.  Landlord agrees to
     allow Tenant to have underground access in, to and about the Building to
     the public rights-of-way for installation of Tenant's telecommunication
     conduits to the Premises in a location determined by Landlord, in
     Landlord's sole discretion and at Tenant's sole expense.  Tenant may
     construct at Tenant's sole cost and expense and for Tenant's exclusive use,
     two communications closets, each approximately 4 feet by 5 feet, in the
     areas designated by Landlord in Landlord's sole discretion which shall be
     near the

                                       35
<PAGE>

     fiber optics currently in the Building. Tenant shall pay Landlord $450 per
     month for such closets, whether one or both are constructed. Such rooms
     will be located in the northwest area of the Building adjacent to other
     existing telecommunication equipment closets and one in the southwest area
     adjacent to other existing telecommunication equipment closets, as
     determined by Landlord in Landlord's sole discretion. Tenant will finish
     such communications closets to include one overhead light (with switch) and
     one entry door. Tenant shall install two (2) four-inch conduits to contain
     electrical and communications lines from the communications closets to the
     Premises in location(s) mutually agreed upon by Landlord and Tenant.

     Tenant shall have the right to install conduits to construct its fiber
     optic system in location(s) determined by Landlord in Landlord's sole
     discretion.  Tenant may install two diverse paths for up to two (2) 4-inch
     conduits from the Premises to two separate penetrations in the foundation
     of the building to the property line in location(s) mutually agreed upon by
     Landlord and Tenant.

          (e)  Building Electrical System.  Landlord shall provide 277/480 volt,
     three-phase power for a maximum of 2000 amps of power to the Premises.
     Landlord shall upgrade the Buildings' power systems to accommodate such
     power needs by installing two additional 1500-amp transformers on or before
     February 20, 2000, subject, however, to delays caused by Public Service
     Company, the electric utility provider for the Building.  Landlord shall
     provide 400 amp service to the Premises from the date Tenant is permitted
     to enter the Premises until the date Public Service Company completes
     installation of such transformers.  Tenant will be permitted to run its
     electrical lines from the south end of the Building to Tenant's power room
     in conduit in a location mutually agreed upon by Landlord and Tenant.

          (f)  Conduit/Access/Riser Space.

               (i)  Tenant is permitted to install up to four chases which are
          to be constructed by Tenant at Tenant's expense and which are not to
          exceed 12 inches by 18 inches, location to be mutually agreed upon
          between Landlord and Tenant. Up to and until such time that the second
          floor is leased to a third party, Tenant will have the ability to
          install two additional exclusive 24" x 24" chases at locations
          mutually agreed upon between Landlord and Tenant.

               (ii) Subject to approval by Landlord of plans by Tenant, which
          approval shall not be unreasonably withheld, Tenant may install one 4-
          inch conduit to each of the telecommunications companies in the
          Building for Tenant's exclusive use at Tenant's sole cost and expense
          and in location(s) approved by Landlord in Landlord's sole discretion.
          Any conduit installed by Tenant shall become the property of Landlord
          and shall be surrendered with the Premises upon the expiration of the
          Lease and any extensions thereto.

                                       36
<PAGE>

               (iii) Tenant will have the non-exclusive right to provide
          telecommunication services to other tenants in the building.  In the
          event other tenants of the Building request Tenant's
          telecommunications services, Tenant shall have the right to install
          one 2-inch conduit from the Premises to such tenants within the
          Building at Tenant's sole cost in a location determined by Landlord in
          Landlord's sole discretion.

          (g)  Life Safety.  Tenant shall have the right to install a fire
     suppression system (or similar system that may be appropriate) independent
     of the Building's systems subject to all laws, rules and regulations.
     Tenant shall also have the right to modify any sprinkler systems within the
     Premises to a dry pipe pre-action system, provided that such modification
     complies with all laws and does not reduce the functionality of said
     sprinkler system within the Premises or anywhere in the Building.  Landlord
     shall cooperate with such reasonable modification and the cost of any such
     modification shall be paid for by Tenant.  Tenant shall have the right to
     relocate any wetlines in or about the Premises with Landlord's approval as
     to location, which approval shall not be unreasonably withheld or delayed,
     at Tenant's sole cost.

          (h)  Access to Loading Dock.  Subject to the rights of other tenants
     and availability, Tenant shall have the right to have access to and utilize
     at all reasonable  times the loading areas at no additional cost to Tenant
     and to have reasonable access to the Premises from such loading areas.

          (i)  Staging Area during Construction. Tenant shall have the right to
     have access to and utilize at all reasonable times an area adjacent to the
     Premises at no additional cost to Tenant for the purpose of temporarily
     storing its equipment during Tenant' s construction.  This right shall
     cease upon completion of Tenant's initial construction in the Premises.

          (j)  Option to use hot water loop.  Tenant will have the option to
     utilize the landlord's hot water boiler system during the lease term and
     any options thereto to provide heating to a portion of the Premises with
     all required system upgrades or modifications resulting therefrom being at
     Tenant's sole cost and expense.  Tenant agrees to pay monthly to Landlord
     during the term of this Lease, as Rent, an amount equal to Tenant's
     proportionate share of the gas bill for the East Anchor Building.  Tenant's
     proportionate share of such gas bill shall be computed by multiplying the
     monthly gas bill for the East Anchor Building by a fraction, the numerator
     of which is the square footage of the Premises excluding the switch area
     and the denominator of which shall be 131,707 (the total rentable square
     footage of the East Anchor Building).

          (k)  Security System.  Tenant will have the option to install a
     security system for the Premises along with card reader entry devices and
     other cypher-type locking entry devices, as determined by Tenant.

                                       37
<PAGE>

     64.  Colocation.  Tenant shall have the right to place the
          ----------
telecommunications equipment of its co-locator customers on the Premises and
such co-location shall not be deemed an assignment or sublease requiring the
consent of Landlord whether or not a written agreement exists between the
parties.  For purposes of this Paragraph and Paragraph 18, "co-locator" shall
mean a customer of Tenant or a customer of an Affiliate (as defined in Paragraph
18) of Tenant that places telecommunications or internet related equipment
belonging to the customer on the Premises which is connected to Tenant's
telecommunications switch equipment.

     65.  Landlord Waiver.  Landlord agrees that it shall execute and
          ---------------
acknowledge a Landlord's Waiver in the form attached to this Lease as Exhibit
"B" and a Subordination, Non-Disturbance and Attornment Agreement in the form
attached to this Lease as Exhibit "C" at the time of the execution of this Lease
and shall obtain the execution and acknowledgment of each person holding a
recorded security interest in Landlord's leasehold interest in the Premises
within twenty (20) days after the execution of this lease and shall promptly
deliver such fully executed Landlord's Waiver and joinders and Subordination,
Non-Disturbance and Attornment Agreement to Tenant.

     66.  Estoppel Certificate.  Within ten (10) days after any request by
          --------------------
Landlord, Tenant shall execute an Estoppel Certificate to evidence (a) the
existence or nonexistence of any default under this Lease by Landlord or by
Tenant, any amendments to this Lease or prepayments of rentals and (b) such
other facts with respect to this Lease as Landlord or any mortgagee may
reasonably require.

     67.  Memorandum of Lease.  A Memorandum of the Lease for recording in the
          -------------------
form attached to this Lease as Exhibit "D" shall be executed and acknowledged by
Landlord and Tenant at the same time as the execution of this Lease and promptly
recorded in the official records of Adams County, Colorado.

                                       38
<PAGE>

     IN WITNESS WHEREOF, Landlord and Tenant have executed the Lease, in
triplicate, as of the Date(s) set forth below their respective signatures
hereto.


Signed and acknowledged in the          NORTH VALLEY TECH LLC,
presence of:                            a Delaware limited liability company

                                        By:  NVT Corp., a Delaware corporation,
                                        its managing member

________________________________        By:_____________________________________
First Witness as to Landlord            Name:___________________________________
                                        Title:__________________________________

________________________________
Second Witness as to Landlord

                                        LANDLORD

                                        Date:___________________________________

Signed and acknowledged in the          PAC-WEST TELECOMM, INC.,
presence of:                            a California corporation

________________________________        By:_____________________________________
First Witness as to Tenant

                                        And:____________________________________
________________________________
Second Witness as to Tenant

                                        TENANT

                                        Date:___________________________________

                                       39
<PAGE>

              This Lease must be both Witnessed and Acknowledged
     This Lease is being forwarded for your approval and execution on the
   understanding that it shall not become effective until it is accepted by
       Landlord and its counsel and executed and delivered by  Landlord.


STATE OF _______________ )
                         ) SS:
COUNTY OF _____________  )

     BEFORE ME, a Notary Public in and for said County and State,  personally
appeared the above-named NORTH VALLEY TECH LLC, a Delaware limited liability
company, by NVT Corp., a Delaware corporation, its managing member, by ________,
the ________________________ of NVT Corp., who acknowledged that s/he did sign
the foregoing instrument and that the same is the free act and deed of said
corporation, and his/her free act and deed personally and as such officer.

     IN TESTIMONY WHEREOF, I have hereunto set my hand and official seal at
_______________, __________, this _________ day of ___________________________,
2000.


                                                  ______________________________
                                                  NOTARY PUBLIC
<PAGE>

STATE OF _________________ )
COUNTY OF ________________ )


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.



Signature:____________________                                      (Seal)


Exhibit "A" - Floor Plan
Exhibit "B" - Landlord Waiver
Exhibit "C" - Subordination, Non-Disturbance and Attornment Agreement
Exhibit "D" - Memorandum of Lease
Exhibit "E" - Work Letter
Exhibit "F" - Location of Tenant HVAC
Exhibit "G" - Rules and Regulations


                                       41
<PAGE>

                                  EXHIBIT "C"
                                                                Loan No.
--------------------------------------------------------------------------------

RETURN TO:
---------
__________________
__________________
__________________


            SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT
            -------------------------------------------------------


     THIS SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT (hereinafter
referred to as "Agreement") made this ___ day of _______________, _______, among
                ---------
______________________________, a ____________________ (hereinafter referred to
as "Lender"), ______________________________ (hereinafter referred to as
    ------
"Tenant"), and ___________________________, a _______________ (hereinafter
 ------
referred to as "Landlord").
                -----------

                                R E C I T A L S:
                                ----------------

          A.  Landlord and Tenant have entered into a certain lease dated
              -----------------------------------------------------------
          __________________, amended ________________________________, assigned
          ----------------------------------------------------------------------
          _______________________, (as amended and/or assigned, the "Lease")
          ------------------------------------------------------------------
          relating to the premises described in Exhibit A attached hereto and by
          -----------------------------------------------
          this reference made a part hereof (hereinafter referred to as the
          "Premises"); and
           --------

          B.  Lender has made or has committed to make a loan to Landlord in the
          approximate principal amount of $_________________ (hereinafter
          referred to as the "Loan") secured by a mortgage or deed of trust (as
                              ----
          the same may be amended, restated, extended, or otherwise modified
          from time to time, the "Mortgage") and an assignment of leases and
                                  --------
          rents (as the same may be amended, restated, extended, or otherwise
          modified from time to time, the "Assignment of Leases") from Landlord
                                           --------------------
          to Lender covering certain property described therein (the "Property")
                                                                      --------
          including the Premises; and

          C.  Tenant has agreed that the Lease shall be subject and subordinate
          to the Mortgage held by Lender, provided Tenant is assured of
          continued occupancy of the Premises under the terms of the Lease;

     NOW, THEREFORE, for and in consideration of the mutual covenants herein
contained, the sum of Ten Dollars ($10.00) and other good and valuable
considerations, the receipt and sufficiency of which are hereby acknowledged,
and notwithstanding anything in the Lease to the contrary, it is hereby agreed
as follows:
<PAGE>

               1.  Subordination and Consent.  Lender, Tenant and Landlord do
                   -------------------------
               hereby covenant and agree that the Lease with all rights,
               options, liens and charges created thereby (including, without
               limitation, any option or rights contained in the Lease, or
               otherwise existing, to acquire any or all of the Premises, or any
               superior leasehold interest therein), is and shall continue to be
               subject and subordinate in all respects to the Mortgage and to
               any renewals, modifications, consolidations, replacements and
               extensions thereof and to all advancements made thereunder.
               Tenant acknowledges that Landlord will execute and deliver to
               Lender an assignment of the Lease as security for said loan, and
               Tenant hereby expressly consents to such assignment.  Tenant
               agrees that if there is a default by Landlord in the performance
               and observance of any of the terms of such Loan, Lender may, at
               its option, demand all rents due under the Lease be paid by
               Tenant directly to Lender at the address specified below, or as
               otherwise specified by Lender.  Tenant agrees that upon Lender's
               written request for payment of rent directly to Lender, Tenant
               will timely remit any and all payments due under the Lease
               directly to, and payable to the order of, Lender.  Such payments
               to Lender will constitute performance of Tenant's payment
               obligations under the Lease.

               2.  Nondisturbance.  Lender does hereby agree with Tenant that,
                   --------------
               in the event Lender becomes the fee simple owner of the Property
               by foreclosure, conveyance in lieu of foreclosure or otherwise,
               so long as Tenant complies with and performs its obligations
               under the Lease, (a) the Lease shall continue in full force and
               effect as a direct Lease between the succeeding owner of the
               Property and Tenant, upon and subject to all of the terms,
               covenants and conditions of the Lease, for the balance of the
               term of the Lease, and Lender will not disturb the possession of
               Tenant, and (b) the Premises shall be subject to the Lease and
               Lender shall recognize Tenant as the tenant of the Premises for
               the remainder of the term of the Lease in accordance with the
               provisions thereof; provided, however, that Lender shall not be:

               a.   subject to any claims, offsets or defenses which Tenant
                    might have against any prior landlord (including Landlord);
                    or

               b.   liable for any act or omission of any prior landlord
                    (including Landlord);  or

               c.   bound by any rent or additional rent which Tenant might have
                    paid for more than the current month or any security deposit
                    or other prepaid charge paid to any prior landlord
                    (including Landlord); or

               d.   bound by any amendment or modification of the Lease made
                    without its written consent.
<PAGE>

               Nothing contained herein shall prevent Lender from naming Tenant
               in any foreclosure or other action or proceeding initiated by
               Lender pursuant to the Mortgage to the extent necessary under
               applicable Law in order for Lender to avail itself of and
               complete the foreclosure or other remedy.

               3.  Attornment.  Tenant does hereby agree with Lender that, in
                   ----------
               the event Lender becomes the owner of the Property by
               foreclosure, conveyance in lieu of foreclosure or otherwise, then
               Tenant shall attorn to and recognize Lender as the landlord under
               the Lease for the remainder of the term thereof, and Tenant shall
               perform and observe its obligations thereunder, subject only to
               the terms and conditions of the Lease.  Tenant further covenants
               and agrees to execute and deliver upon request of Lender an
               appropriate agreement of attornment to Lender and any subsequent
               titleholder of the Premises.

               4.  Lease Defaults.  In the event Landlord shall fail to perform
                   --------------
               or observe any of the terms, conditions or agreements in the
               Lease, Tenant shall give written notice thereof to Lender and
               Lender shall have the right (but not the obligation) to cure such
               default.  Tenant shall not take any action with respect to such
               default under the Lease, including without limitation any action
               in order to terminate, rescind or avoid the Lease or to withhold
               any rent or other monetary obligations thereunder, for a period
               of thirty (30) days following receipt of such written notice by
               Lender; provided, however, that in the case of any default which
               cannot with diligence be cured within said thirty (30) day
               period, if Lender shall proceed promptly to cure such default and
               thereafter prosecute the curing of such default with diligence
               and continuity, the time within which such default may be cured
               shall be extended for such period as may be necessary to complete
               the curing of such default with diligence and continuity.

               5.  Obligations and Liability of Lender.  Lender shall have no
                   -----------------------------------
               obligations nor incur any liability with respect to any
               warranties of any nature whatsoever, whether pursuant to the
               Lease or otherwise, including, without limitation, any warranties
               respecting use, compliance with zoning, hazardous wastes or
               environmental laws, Landlord's title, Landlord's authority,
               habitability, fitness for purpose or possession.  Furthermore, in
               the event that Lender shall acquire Landlord's interest in the
               Property, Lender shall have no obligation, nor incur any
               liability, beyond Lender's then equity interest, if any, in the
               Property, and Tenant shall look exclusively to such equity
               interest of Lender, if any, in the Property for the payment and
               discharge of any obligations or liability imposed upon Lender
               hereunder, under the Lease (or under any new lease with Tenant),
               and Lender is hereby released and relieved of any other
               obligations or
<PAGE>

               liability hereunder, under the Lease or under any such new lease.
               Lender shall not, either by virtue of the Mortgage, the
               Assignment of Leases or this Agreement, be or become a mortgagee
               in possession or be or become subject to any liability or
               obligation under the Lease or otherwise until Lender shall have
               acquired the Landlord's interest in the Property, by foreclosure
               or otherwise, and then such liability or obligation of Lender
               under the Lease (as modified by the terms of this Agreement)
               shall extend only to those liability or obligations accruing
               subsequent to the date that Lender has acquired Landlord's
               interest in the Property. Without limiting the generality of the
               foregoing, neither the Mortgage, the Assignment of Leases nor
               this Agreement shall, prior to Lender's acquisition of Landlord's
               interest in the Property, by foreclosure or otherwise, operate to
               place responsibility for the control, care, management or repair
               of the Property upon Lender or impose upon Lender responsibility
               for the carrying out of any of the terms or conditions of the
               Lease, and Lender shall not be responsible or liable for any
               waste committed on either the Premises or the Property by any
               party whatsoever, for any dangerous or defective condition of the
               Property or for any negligence in the management, upkeep, repair
               or control of either the Premises or the Property.

               6.  Severability.  If any portion or portions of this Agreement
                   ------------
               shall be held invalid or inoperative, then all of the remaining
               portions shall remain in full force and effect, and, so far as is
               reasonable and possible, effect shall be given to the intent
               manifested by the portion or portions held to be invalid or
               inoperative.

               7.  Governing Law.  This Agreement shall be governed by and
                   -------------
               construed in accordance with the laws of the State of Colorado.

               8.  Notices.  So long as the Mortgage remains outstanding and
                   -------
               unsatisfied, Tenant will mail or deliver to Lender, at the
               address and in the manner hereinbelow provided, a copy of all
               notices permitted or required to be given to the Landlord by
               Tenant under and pursuant to the terms and provisions of the
               Lease.  All notices or other communications required or permitted
               to be given pursuant to the provisions hereof shall be in writing
               and shall be considered as properly given if (i) mailed to the
               addressee by first class United States mail, postage prepaid,
               registered or certified with return receipt requested, (ii) by
               delivering same in person to the addressee, or (iii) by delivery
               to a third party commercial delivery service for same day or next
               day delivery to the office of the addressee with proof of
               delivery.  Notice so given shall be effective, as applicable,
               upon (i) the third (3rd) day following the day such notice is
               deposited with the U.S. Postal Service, (ii) delivery to the
               addressee, or (iii) upon delivery to such third party delivery
               service.  Notice given in any other manner shall be
<PAGE>

               effective only if and when received by the addressee. For
               purposes of notice, the addresses of the parties shall be:

          Lender:   ____________________________________
                    ____________________________________
                    ____________________________________
                    Attn: ______________________________

          Landlord: ____________________________________
                    ____________________________________
                    ____________________________________
                    Attn:________________________________

          Tenant:   ____________________________________
                    ____________________________________
                    ____________________________________
                    Attn:________________________________

               Notwithstanding the foregoing, any party shall have the right to
               change its address for notice hereunder to any other location
               within the continental United States by the giving of thirty (30)
               days' notice to the other parties in the manner set forth herein.

               9.  Successors and Assigns.  This Agreement shall be binding upon
                   ----------------------
               and inure to the benefit of the parties hereto and their
               respective heirs, legal representatives, successors, successors-
               in-title and assigns.  When used herein, the term "landlord"
               refers to Landlord and to any successor to the interest of
               Landlord under the Lease and "Lender" refers to Lender and to any
               assignee of the note secured by the Mortgage and Lender's
               servicer of the Loan, if any.

               10.  Tenant's Personal Property.  In no event shall the Mortgage
                    --------------------------
               cover or encumber (and shall not be construed as subjecting in
               any manner to the lien thereof) any of Tenant's moveable trade
               fixtures, business equipment, furniture, signs or other personal
               property at any time placed on or about the Premises.

               11.  Counterparts.  This Agreement may be executed in one or more
                    ------------
               counterparts, each of which when so executed shall be deemed to
               be an original, but all of which when taken together shall
               constitute one and the same instrument.

               12.  Headings.  The headings, captions, and arrangements used in
                    --------
               this Agreement are for convenience only and shall not affect the
               interpretation of this Agreement.
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement under
seal as of the date first above written.

                              LENDER:

                              _________________________,
                              a(n)______________________________


                              By:________________________________
                              Name:______________________________
                              Title:_____________________________


                              TENANT:

                              PAC-WEST TELECOMM, INC.,
                              a California corporation


                              By:__________________________________
                              Name:________________________________
                              Title:_______________________________


                              LANDLORD:

                              NORTH VALLEY TECH LLC,
                              a Delaware limited liability company

                              By:  NVT Corp., a Delaware corporation,
                              its managing member


                              By:__________________________________
                              Name:________________________________
                              Title:_______________________________
<PAGE>

STATE OF__________________ )
COUNTY OF_________________ )


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.



Signature:___________________________                           (Seal)



STATE OF__________________ )
COUNTY OF_________________ )


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.


     WITNESS my hand and official seal.



Signature:__________________________________                    (Seal)
<PAGE>

STATE OF__________________ )
COUNTY OF_________________ )


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.


     WITNESS my hand and official seal.



Signature:________________________________                      (Seal)
<PAGE>

                                  EXHIBIT "B"
                                LANDLORD WAIVER


RECORDING REQUESTED BY:



AND WHEN RECORDED, RETURN TO:

MORRISON & FOERSTER
425 California Street
San Francisco, California  94105
Attention:  Jill Feldman, Esq.

 ______________________________________________________________________________
                       (Space Above for Recorder's Use)


                                 LANDLORD WAIVER

     This LANDLORD WAIVER (the "Waiver") is entered into as of this ______ day
of ____________________, 2000 by and among NORTH VALLEY TECH LLC, a Delaware
limited liability company (the "Landlord"), PAC-WEST TELECOMM, INC., a
California corporation (the "Tenant"), and UNION BANK OF CALIFORNIA, N.A., a
national banking association, in its capacity as administrative lender (the
"Agent") for itself and other financial institutions (collectively, the
"Lenders").

                                 RECITALS

     A.  The Landlord and the Tenant have entered into that certain lease dated
as of ________________, 2000, (as such lease may have been amended to date, the
"Lease") covering certain real property in the City of Thornton, County of
Adams, State of Colorado, and as more particularly described on Exhibit "A"
attached hereto and incorporated herein by this reference (the "Premises").

     B.   The Landlord is a tenant of the real property of which the Premises
forms a part pursuant to a ground lease dated July 22, 1964 and recorded July
22, 1964 in Book 1166 at page 140, records of Adams County, Colorado ("Ground
Lease").

     C.  As partial security for Tenant's repayment and performance of its
obligations under certain credit facilities extended and to be extended in the
future to the Tenant by the Lenders, the tenant has granted or will grant a
security interest in certain goods, inventory, and other personal property owned
by the Tenant, some of which may be located in the Premises, to the Agent.
<PAGE>

     D.  In connection with the Tenant's granting of such security interest, the
Agent requires certain assurances from the Landlord.

                                   AGREEMENT

     For good and valuable consideration, the receipt of which is hereby
acknowledged, the parties hereby agree as follows:

     1.   The Landlord agrees to send the Agent at an address designated by the
Agent a copy of any notice of default (or termination) (the "Default Notice") of
the Lease, or of the Ground Lease, and grants the Agent during the grace period
already permitted under the Lease the right to cure any such default under the
Lease.  Until further notice from the Agent, the address of the Agent for all
notices is as follows:

               Union Bank of California, N.A.
               1800 Harrison Street, Suite 1400
               P.O. Box 1020
               Oakland, CA 94604-1020
               Attention: Gail Fletcher, Vice-President Community Banking Group

     2.   Landlord agrees to send to agent, at an address designated by
agent, a copy of any Notice of Default or of sale from any mortgagee or
beneficiary of a deed of trust secured by Landlord's leasehold interest in the
Ground Lease, including, without limitation, any notice from Salomon Brothers
Realty Corp.

     3.   The Landlord consents to the granting of a security interest in all of
the personal property of Tenant located now or in the future on the Premises
(the "Personal Property"), including any part of the Personal Property that is
now or is hereafter installed on or affixed to the Premises, or that is or may
be deemed to be "fixtures" within the meaning of the then applicable Uniform
Commercial Code.  The Landlord agrees that all of the Personal Property, whether
or not affixed to or located or installed on the Premises, constitutes and shall
remain personal property and shall not become installed or located on or affixed
to the Premises or any other real estate.

     4.   The Landlord agrees that any and all liens, claims, demands, rights or
interests that the Landlord may now or hereafter have in or to the Personal
Property shall be and are hereby made subordinate and inferior to any now
existing or hereafter arising lien or security interest in favor of the Agent.

     5.   The Landlord agrees that if the Tenant defaults on its obligations to
the Agent and, as a result, the Agent undertakes to enforce its security
interest in the Personal Property, as follows:
<PAGE>

          (a)  the Landlord will cooperate with the Agent in its efforts to
assemble all of the Personal Property located on the Premises, provided,
however, that the Landlord shall not be obligated to incur any expense or other
obligation in connection with such cooperation;

          (b)  the Landlord will permit the Agent to remain on the Premises for
up to sixty (60) days after the Agent declares the default, provided that the
Agent, for the period of time the Agent uses the Premises, (i) pays or causes to
be paid the base rent or adjusted base rent or, in the case where the Lease has
terminated, the base rent or adjusted base rent that would have become due under
the Lease for such period if the Lease had not been terminated, for the period
of time the Agent uses the Premises; (ii) provides and retains the liability and
property insurance coverage and pays utilities required, or which would have
been required if the Lease had not been terminated under the Lease; and (iii)
delivers a written agreement to do so;

          (c)  the Agent or its representatives may enter upon the Premises at
reasonable times, and after written notice to the Landlord, for the purpose of
removing, or repossessing, the Personal Property, provided that the Agent
promptly repairs any and all physical damage to the Premises caused by such
removal;

          (d)  the Landlord shall not hinder the Agent's actions in enforcing
its liens on the Personal Property; and

          (e)  except as provided in subsection (b) of this Section 5, the Agent
may enter the Premises for such purposes without assuming the Lease and all
obligations and all obligations contained therein.

Upon any such removal, any liens, claims, demands, rights or interests of the
Landlord in the Personal Property shall be discharged and released.
Notwithstanding anything herein to the contrary, in no event shall the Agent's
right to enter or occupy the Premises pursuant to this Waiver extend beyond
sixty (60) days from the date of termination or expiration of the term of the
Lease, and at any time thereafter the Landlord shall have the right to have any
personal property of the Tenant that may be located upon the Premises removed
from the Premises in accordance with the terms of the Lease and applicable law.

     6.   This Waiver may be amended or modified only by an instrument in
writing signed by each of the parties hereto.

     7.   This Waiver may be executed in counterparts, each of which shall be
deemed an original but all of which taken together shall constitute one and the
same instrument.

     8.   This Waiver shall inure to the benefit of and be binding upon the
parties hereto and their respective heirs, administrators, successors and
assigns or encumbrances.
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed and delivered this
Waiver as of the date first above written.

                    LANDLORD:       NORTH VALLEY TECH LLC,
                                    a Delaware limited liability company

                                    By:  NVT, a Delaware corporation
                                    its managing member

                                    By:________________________________
                                    Name:______________________________
                                    Title:_____________________________


                    TENANT:         PAC-WEST TELECOMM, INC.,
                                    a California corporation

                                    By:________________________________
                                    Name:______________________________
                                    Title:_____________________________


                    AGENT:          UNION BANK OF CALIFORNIA,
                                    N.A., a national banking association,
                                    as Agent for the Lenders

                                    By:________________________________
                                    Name:______________________________
                                    Title:_____________________________


STATE OF____________________)
COUNTY OF___________________)


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.

Signature:__________________________                                    (Seal)
<PAGE>

STATE OF__________________)
COUNTY OF_________________)


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.



Signature:_________________________                                   (Seal)



STATE OF                   )
COUNTY OF                  )

     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.



Signature:________________________                                      (Seal)



This Instrument was prepared by:

     Neumiller & Beardslee
     509 West Weber Avenue, 5th Floor (95203)
     Post Office Box 20
     Stockton, California 95201-3020
<PAGE>

                                    JOINDER
                         SALOMON BROTHERS REALTY GROUP

     This Joinder is made as of _________________, 2000, by Salomon Brothers
Realty Corp., a _________ Corporation ("Beneficiary") and is attached to and
made a part of that certain Landlord Waiver by and among North Valley Tech LLC,
a Delaware limited liability company, ("Landlord"), Pac-West Telecomm, Inc., a
California corporation ("Tenant") and UNION BANK OF CALIFORNIA, N.A., a national
banking association, as Agent for the Lenders.

     NOW, THEREFORE, for valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the Beneficiary hereby joins in the Landlord
Waiver and agrees to be bound by its terms and conditions if it should succeed
to the interests of the Landlord under the Lease.

     IN WITNESS WHEREOF, the parties hereto have executed this Joinder as of the
date set forth above.

                                    BENEFICIARY:

                                    SALOMON BROTHERS REALTY
                                    GROUP a _____________________
                                    Corporation

                                    By:__________________________
                                    Printed Name:________________
                                    Title:_______________________


STATE OF____________________)
COUNTY OF___________________)

     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.



Signature:__________________________                                  (Seal)
<PAGE>

                                  EXHIBIT "D"
                              MEMORANDUM OF LEASE
                North Valley Tech LLC - Pac-West Telecomm, Inc.

     THIS MEMORANDUM OF LEASE dated as of January ____, 2000, by and between
North Valley Tech LLC, a Delaware limited liability company ("Landlord"), and
Pac-West Telecomm, Inc., a California corporation ("Tenant").

WITNESSETH:

     By a lease ("Lease") dated January __, 2000, Landlord has demised and
leased to Tenant, and Tenant has leased from Landlord the "Premises" consisting
of approximately 26,504 rentable square feet located at 500 East 84th Avenue,
Thornton, CO 80229 under the following terms and conditions:

1.   The Premises are identified on the legal description which is specified as
Exhibit "A" and is attached hereto.

2.   The Lease term is for ten (10) years and commences on April 1, 2000 and
shall terminate on March 31, 2010, unless sooner terminated or extended as
provided for in the Lease.

3.   The Lease may be extended for two (2) additional terms of five (5) years
each.

4.   The Lease does provide Tenant with an Expansion Option and Right of First
Refusal on certain unleased space on the first floor of the East Anchor
Building.

5.   The Lease provides that Tenant shall have peaceable and quiet enjoyment of
the Premises so long as Tenant is not in default.  Said Lease also provides that
the Lease shall be subject and subordinate to any mortgage, deed of trust,
ground lease or other lien on the Premises if the lienholder or lessor executes
a Nondisturbance and Attornment Agreement in the form of Exhibit "C" to the
Lease, and a Landlord's Waiver and Joinder in the form of Exhibit "B" to the
Lease.

6.   The sole purpose of this instrument is to give notice of said Lease and all
of its terms, covenants, and conditions to the same extent as if said Lease were
set forth herein.

7.   The conditions, covenants, and agreements contained in the Lease shall be
binding upon and inure to the benefit of the parties hereto, their respective
heirs, personal representative, successors and assigns.  In the event of any
conflict between the terms and conditions of this instrument and the term and
conditions of the Lease, it is agreed that the terms and conditions of the Lease
shall control.

8.   Tenant has nonexclusive use of certain areas outside the Premises pursuant
to the Lease.

9.   The Lease does not contain an option to Purchase the Lease Premises.
<PAGE>

     IN WITNESS WHEREOF the parties have executed this Memorandum of Lease as of
the day and year first above written.

                              LANDLORD:

                              NORTH VALLEY TECH LLC,
                              a Delaware limited liability company

                              By:  NVT Corp., a Delaware corporation,
                              its managing member


                              By:_____________________________
                              Name:___________________________
                              Title:__________________________
                              Date:___________________________


                              TENANT:

                              PAC-WEST TELECOMM, INC.,
                              a California corporation


                              By:_____________________________
                              Name:___________________________
                              Title:__________________________

STATE OF_______________)
COUNTY OF______________)


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.
<PAGE>

STATE OF_______________)
COUNTY OF______________)


     On _______________, before me, ___________________________, personally
appeared ___________________________________________, personally known to me (or
proved to me on the basis of satisfactory evidence) to be the person(s) whose
name(s) is/are subscribed to the within instrument and acknowledged to me that
he/she/they executed the same in his/her/their authorized capacity(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

     WITNESS my hand and official seal.
<PAGE>

                                  EXHIBIT "E"
                                  WORK LETTER
                           North Valley Tech Center
                           ------------------------

This Work Letter by reference is made part of the Lease between North Valley
Tech LLC as Landlord, and Pac-West Telecomm, Inc. as Tenant, covering the
Premises known as Suite 100 in the East Building at North Valley Tech Center.


The Premises will be altered by Landlord (except as otherwise provided) as set
forth in detail below.  Landlord shall provide all materials, labor,
construction coordination and general supervision necessary to remodel the
Premises (except as otherwise provided) as follows:

                    BUILDING SHELL IMPROVEMENTS AS FOLLOWS:
                    ---------------------------------------

CONSTRUCTION/DEMOLITION
1.  Demolition of non-load bearing walls, ceilings, lights, grid, electrical,
    duct works, hot water pipes and plumbing, and conveyor systems as reasonably
    required by Tenant. Note that existing structural shear walls and storefront
    entry locations will remain.
2.  Perimeter and demising walls to be drywalled to underside of structure.
    Tenant shall provide all materials, labor, construction coordination and
    general supervision necessary to complete this work to Landlord and Tenant's
    satisfaction. Landlord shall reimburse Tenant for the reasonable cost of
    this work.
3.  Structural support as necessary for Tenant HVAC at roof. Provided Tenant has
    delivered its specifications to Landlord on or before January 1, 2000,
    Landlord's plans for its structural reinforcement will be submitted to
    Tenant for Tenant's approval on or before January 15, 2000. Tenant have the
    right to require changes to the plans and will submit such requirements to
    Landlord in writing no later than three (3) days after receipt of Landlord's
    plans.
4.  New 45 mil ballasted EPDM roof with R 30 insulation.
5.  Two new 4 feet x 7.5 feet store front entry doors per tenant's plans.
    Glazing to match building standard windows.
6.  Landlord warrants that the existing slab system on the first floor will meet
    or exceed Tenant's load criteria of 150psf.
7.  In order to provide the Premises with no less than 2000 amps, Landlord will
    install two (2) 1500 amp transformers for Tenant's non-exclusive use.
    Landlord will complete such installation on or before the Commencement Date
    of the Lease.
8.  Landlord will complete the removal of all asbestos and other Hazardous
    Material in and around the Premises and other areas in which Tenant will
    install its equipment, conduit, pipes, etc.

ELECTRICAL
1.  Connected panel provided and sized for Tenant loads, metered separately.
    Distribution by Tenant.
2.  Landlord will work with local utility company to provide 2000 amps of 480
    volt/3-phase power to space.
<PAGE>

HVAC/MECHANICAL
1.  Tenant to submit plans for approval, such approval not to be unreasonably
    withheld, delayed or involving any relocation of sprinkler, or plumbing
    lines. Tenant to maintain in good working order all existing sprinkler and
    plumbing lines during and after relocation work.

Other than the work described above as building shell improvements, the space
will be delivered in "as is" condition.

In the event Tenant makes any changes, additions or modifications to the
Landlord's work and materials ("Tenant Changes") which result in an increase in
costs to Landlord over and above the costs Landlord would have incurred in the
absence of the Tenant Changes, Landlord shall notify Tenant in writing of the
amount of such increase.  Only changes approved by Tenant's Facility Planner
shall be accepted.

Upon receipt of said notice Tenant shall, within three (3) business days
thereafter, notify Landlord in writing that it shall either (I) approve the
additional cost to complete the alterations and thereby agree to reimburse
Landlord for the amount by which the cost to complete the alterations (which
cost shall include an amount equal to five percent (5%) of Landlord's costs as
an administrative fee attributable to its construction coordination and
supervision) exceeds Landlord's costs without Tenant's changes, or (ii) agree to
reduce the scope of the alterations so that the actual cost of the alterations
does not exceed Landlord's costs without Tenant Changes.

If the Tenant is to provide any additional features, materials or work over and
above  that specified in this Work Letter, Tenant must receive the written
approval of Landlord, in advance, and must pay all costs and expenses for such
work.

Finally, Tenant understand and acknowledges that notwithstanding any
representation by Landlord or its agents to the contrary (i) Landlord estimates
that the time to complete construction described above is 2 to 4 weeks and that
Landlord will not commence construction until after the Lease is fully executed
by both parties; and (ii) if Tenant desires at its sole cost and expense, and
Landlord agrees, to make any changes in the scope of construction, then the
estimated completion of construction will be adjusted accordingly.  Any Tenant
delays in reviewing or approving space plans, construction documents, or
submittals, or in providing necessary information in the planning or
construction process will not postpone the Lease Commencement Date.
<PAGE>

AGREED TO AND ACCEPTED BY:             AGREED TO AND ACCEPTED BY:

PAC-WEST TELECOMM, INC.                NORTH VALLEY TECH LLC, a Delaware
                                       limited liability company

                                       By:  NVT Corp., a Delaware corporation,
                                       its managing member


By:________________________            By_____________________________
Name:______________________            Name:__________________________
Title:_____________________            Title:_________________________

Date:_______________                   Date:____________________

         TENANT                                   LANDLORD
<PAGE>

                                  EXHIBIT "G"
                             RULES AND REGULATIONS


     A.  Advertising and Signs: Unless expressly permitted by Landlord, no sign,
advertisement, notice or other lettering shall be exhibited, inscribed, painted
or affixed on any part of the outside or inside of the Building, except on the
glass or panels of the doors of the Premises, and then only of subject matter
and in such color, size, style and material as shall conform to the
specifications of Landlord. Landlord reserves the right to remove all other
signs or lettering without notice to Tenant, at the expense of Tenant. Any
newspaper, magazine or other advertising done from the said Premises, or
referring to the said Premises, which in the opinion of Landlord is
objectionable shall be immediately discontinued upon notice from Landlord.

     B.  BICYCLE AND ANIMALS: Except as provided in this Lease, no bicycle or
other vehicle and no animal shall be brought or permitted to be in the Premises
or the Building without the prior consent of Landlord.

     C.  CLOSING AND LOCKING DOORS: Unless expressly permitted by Landlord, all
doors to the Premises are to be kept closed at all times except while in actual
use for entrance to or exit from such Premises. Tenant shall be responsible for
the locking of doors and the closing of transoms in and to the Premises. Any
damage resulting from neglect of this rule shall be paid by Tenant.

     D.  MACHINERY:  Landlord's written consent shall be first obtained for the
use or installation of all types of office machinery, generally described as,
but not limited to, machinery equipment, I.B.M. equipment, refrigeration
equipment, heating equipment, air conditioning apparatus, and all other types of
office machine equipment. This clause is not meant to refer to the use or
installation of such equipment as standard adding machines and typewriters which
are used on desks and similar office equipment.

     E.  UNSIGHTLY PLACEMENT OF EQUIPMENT:  Unless expressly permitted by
Landlord, Tenant shall not place or allow anything to be against or near the
glass of partitions or doors or windows of the Premises which may diminish the
light in, or be unsightly from, halls or corridors.

     F.  LOCKS: Unless expressly permitted by Landlord, no additional locks or
similar devices shall be attached to any door and no keys other than those
provided by Landlord shall be made for any door. If more than two keys for one
lock are desired by Tenant, Landlord may provide the same upon payment by
Tenant. Upon termination of this Lease or of Tenant's possession, Tenant shall
surrender all keys of the Premises and shall explain to Landlord all combination
locks on safes, cabinets and vaults.

     G.  NOISES AND OTHER NUISANCES:  Tenant shall not make or permit any noise
or odor that is objectionable to Landlord or to other occupants of the Building
to emanate from the Premises, and shall not create or maintain a nuisance
therein, and shall not disturb, solicit or
<PAGE>

canvass any occupant of the Building, and shall not do any act tending to injure
the reputation of the Building.

     H.  OBSTRUCTIONS:  Unless expressly permitted by Landlord, Tenant shall not
obstruct, or use for the storage or for any purpose other than ingress and
egress, the sidewalks, entrances, passages, courts, corridors, vestibules,
halls, elevators and stairways of the Building and no floor mats shall be placed
in the corridors by Tenant.

     I.  SOLICITORS:  Landlord reserves the right, but shall not be held
obligated, to exclude or eject from the Building any or all solicitors,
canvassers or peddlers, and any other class of persons and individuals who
conduct themselves in such a manner as in the judgment of Landlord constitutes
an annoyance to any tenants of the Building or an interference with Landlord's
operation of the Building, or who are otherwise undesirable. Tenant shall
cooperate with Landlord in preventing soliciting and peddling in the Building.

     J.  LIGHT FOR CLEANING:  Tenant, at its expense, shall provide artificial
light and electric current for any cleaning, repairs, alterations or other
services in the Premises.

     K.  APPLICATION FOR SERVICES:  Tenant shall make application at the office
of the Building for all cleaning, repairing, alteration or special services.
Employees of Landlord shall not perform any work or do anything outside of the
regular duties unless under special instruction from Landlord.

     L.  WINDOWS AND PROJECTIONS:  Nothing shall be affixed to or projected
beyond the outside of the Building by Tenant without the proper written consent
of Landlord. If Tenant desires, and Landlord permits, blinds, shades, awnings,
or other form of outside or inside window covering, ventilating equipment or
similar devices, they shall be furnished and installed at the expense of Tenant
and must be of such shape, color, material and make as are approved by Landlord.
Tenant shall not place or permit to be placed any article of any kind on the
window ledges or elsewhere on the exterior walls, and shall not throw or drop or
permit to be thrown or dropped any article from any window of the Building.

     M.  WEAPONS:  Tenant shall not permit its employees, contractors, or any
other person under its control to bring into the Building any firearm or weapon
without first obtaining the written consent of Landlord.

     N.  ADDITIONAL RULES:  Landlord reserves the right to make such other and
further rules and regulations as in its judgment may from time to time be needed
or desired for the safety, care and cleanliness of the Premises and the Building
and for the preservation of good order therein, but shall not impair the use and
enjoyment of the Premises under the other terms and provisions of the within
Lease.