OPINION OF BINGHAM MCCUTCHEN LLP

Exhibit 5

March 10, 2003

Our File No. 2003513-2035130163

California Water Service Group
1720 North First Street
San Jose, California 95112

Attention: Peter C. Nelson
President and Chief Executive Officer

Registration Statement on Form S-3 of California Water
Service Group ("Universal Shelf")

Ladies and Gentlemen:

We are acting as counsel to California Water Service Group, a Delaware
corporation (the "Group"), in connection with its registration statement on Form
S-3 (the "Registration Statement") to be filed of even date herewith with the
Securities and Exchange Commission (the "Commission") under the Securities Act
of 1933, as amended (the "Securities Act"), relating to the proposed public
offering of up to $120,000,000 aggregate initial offering price of the following
securities of the Group:

(i) debt securities (the "Debt Securities");

(ii) shares of preferred stock (the "Preferred Stock"); and

(iii) shares of common stock, $0.01 par value per share (the "Common
Stock").

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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The Debt Securities, the Preferred Stock and the Common Stock are herein
referred to as the "Registered Securities." The Registered Securities may be
offered and sold by the Group from time to time pursuant to Rule 415 under the
Securities Act as set forth in the base prospectus which forms a part of the
Registration Statement (the "Prospectus"), and as to be set forth in one or more
supplements to the Prospectus or term sheets that may be filed under the
Securities Act. This opinion is furnished to you at your request to enable you
to fulfill the requirements of Item 601(b)(5) of Regulation S-K, 17 CFR Section
229.601(b)(5), in connection with the filing of the Registration Statement.

As such counsel, we have reviewed the corporate proceedings taken by the Group
with respect to the registration of the Registered Securities. We have also
examined and relied upon originals or copies of such corporate records,
documents, agreements or other instruments of the Group, and such certificates
and records of public officials, and such other documents, as we have deemed
necessary or appropriate in connection herewith. As to all matters of fact
(including factual conclusions and characterizations and descriptions of
purpose, intention or other state of mind) we have relied entirely upon
certificates of officers of the Group, and have assumed, without independent
inquiry, the accuracy of those certificates. We have assumed the genuineness of
all signatures, the conformity to the originals of all documents reviewed by us
as copies, the authenticity and completeness of all original documents reviewed
by us in original or copy form and the legal competence of each individual
executing any applicable document.

For purposes of this opinion letter, we have assumed that:

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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(i) the issuance, sale, amount, and terms of the Registered
Securities to be offered from time to time will be duly
authorized and established by proper action of the Board of
Directors of the Group, and in accordance with the Certificate
of Incorporation of the Group, as amended from time to time,
the By-laws of the Group as amended from time to time, and
applicable Delaware law and that, at the time of each such
issuance and sale of such Registered Securities, the Group
will continue to be validly existing and in good standing
under the laws of the State of Delaware with the requisite
corporate power and authority to issue and sell all such
Registered Securities at such time and will have received any
required approvals of any governmental authority or agency in
connection therewith;

(ii) any Debt Securities will be issued pursuant to an indenture
(each, an "Indenture"), entered into by the Group and a duly
qualified trustee (each, a "Trustee"), substantially in the
form of the form of indenture filed as Exhibit 4 to the
Registration Statement, and such Debt Securities will be in
the form of such Debt Security contained in or approved in
accordance with such Indenture, such Debt Securities will have
been duly executed, issued and delivered on the part of the
Group, and authenticated by the Trustee pursuant to the
Indenture and that, at the time any Debt Securities are so
issued, the related Indenture will have been executed and
delivered by, and will constitute a valid, binding,
enforceable agreement of the Group and the applicable Trustee
party thereto;

(iii) any shares of Preferred Stock issued pursuant to the
Registration Statement from time to time will not exceed the
maximum authorized number of shares of Preferred Stock under
the Certificate of Incorporation of the Group, as the same may
have been amended, minus that number of shares of Preferred
Stock that may have been issued and are outstanding, or are
reserved for issuance for other purposes, at such time, and
will be issued pursuant to the Certificate of Incorporation of
the Group and a Certificate of Designations (the "Certificate
of Designations")

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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the terms of which will be in compliance with the General
Corporation Law of the State of Delaware, and will be duly
authorized by the Board of Directors of the Group or a
properly authorized committee thereof and duly executed on
behalf of the Group and filed with the Secretary of State of
Delaware; and

(iv) any shares of Common Stock issued pursuant to the Registration
Statement from time to time will not exceed the maximum
authorized number of shares of Common Stock under the
Certificate of Incorporation of the Group, as the same may
have been amended, minus that number of shares of Common Stock
that may have been issued and are outstanding, or are reserved
for issuance for other purposes, at such time.

Each opinion set forth below is subject to the following general qualifications:

(a) The enforceability of any obligation of the Group under the
Debt Securities or otherwise may be limited by bankruptcy,
insolvency, reorganization, moratorium, marshaling or other
laws and rules of law affecting the enforcement generally of
creditors' rights and remedies (including such as may deny
giving effect to waivers of debtors' rights); and we express
no opinion as to the status under any fraudulent conveyance
laws or fraudulent transfer laws of any of the obligations of
the Group under the Debt Securities or otherwise.

(b) No opinion is given herein as to the availability of any
specific or equitable relief of any kind or as to the
enforceability of any particular contractual provision
relating to remedies after default.


California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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(c) The enforcement of any rights of the holders of the Debt
Securities and any Trustee may in all cases be subject to an
implied duty of good faith and fair dealing and to general
principles of equity (whether such enforcement is considered
in a proceeding at law or in equity).

(d) We express no opinion as to the enforceability of any
particular provision of any of the Debt Securities
constituting or relating to (i) waivers of rights to object to
jurisdiction or venue, or consents to jurisdiction or venue,
(ii) waivers of rights to (or methods of) service of process,
or rights to trial by jury, or other rights or benefits
bestowed by operation of law, (iii) waivers of any applicable
defenses, setoffs, recoupments, or counterclaims, (iv) the
grant of powers of attorney or proxies to any holders of the
Debt Securities or any Trustee, (v) exculpation or exoneration
clauses, indemnity clauses, and clauses relating to releases
or waivers of unmatured claims or rights, (vi) waivers or
variations of provisions which are not capable of waiver or
variation under Section 1-102, 9-602 or 9-603 or other
provisions of the Uniform Commercial Code of any applicable
jurisdiction, (vii) provisions of the Debt Securities rendered
ineffective or unenforceable by Section 2A-303, 9-406, 9-407
or 9-408 of the Uniform Commercial Code of any applicable
jurisdiction, (viii) the grant of powers of attorney or
proxies to any holders of the Debt Securities or any Trustee,
(ix) submission to binding arbitration, or (x) the imposition
or collection of interest on overdue interest or providing for
a penalty rate of interest or late charges on overdue or
defaulted obligations, or the payment of any premium,
liquidated damages, or other amount which may be held by any
court to be a "penalty" or a "forfeiture."

(e) No opinion is given herein as to the effect of usury laws or
other laws regulating the maximum rate of interest which may
be charged, taken or received of any jurisdiction.


California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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(f) No opinion is given herein as to the enforceability of any
particular provision of any agreement or instrument relating
to indemnification under any securities or other laws or
contribution in lieu of such indemnification.

(g) No opinion is given herein as to the enforceability of any
particular provision of any of the Registered Securities or of
any agreement or instrument relating to or constituting:

(i) time of the essence clauses;

(ii) provisions which may be rendered ineffective or
unenforceable by Section 1670.5 of the California Civil Code,
which provides that a court may refuse to enforce a contract
or limit the application thereof or any clause thereof which
the court finds as a matter of law to have been unconscionable
at the time it was made;

(iii) acceleration of future amounts due (other than
principal) without appropriate discount to present value; and

(iv) provisions to the effect that rights or remedies are not
exclusive, that every right or remedy is cumulative, may be
exercised without notice, may be exercised in addition to or
with any other right or remedy, or that the election of some
particular remedy or remedies does not preclude recourse to
one or another remedy.

Subject to the limitations set forth below, we have made such examination of law
as we have deemed necessary for the purposes of expressing the opinions set
forth in this letter. Such opinions are limited solely to (i) the internal,
substantive laws of the State of California as applied by courts located in
California without regard to choice of law, (ii) the General Corporation Law of
the State of Delaware as applied by courts located in Delaware, the applicable
provisions of the Delaware Constitution and the reported judicial decisions
interpreting those laws, and (iii) solely with respect to the Debt Securities,
the internal, substantive laws of the State of California as

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
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applied by courts located in California without regard to choice of law, in each
case to the extent that the same may apply to or govern such transactions. We
note that any Debt Securities will contain a provision stating that they shall
be governed by, and construed in accordance with, the laws of the State of
California (the "California Chosen-Law Provision"). No opinion is given herein
as to the California Chosen-Law Provision, or otherwise as to the choice of law
or internal substantive rules of law that any court or other tribunal may apply
to the Debt Securities.

To the extent that the obligations of the Group under any Indenture may be
dependent upon such matters, we assume for purposes of this opinion that the
Trustee thereunder is duly organized, validly existing and in good standing
under the laws of its jurisdiction of organization; that the Trustee is duly
qualified to engage in the activities contemplated by such Indenture; that such
Indenture has been duly authorized, executed and delivered by the Trustee and
constitutes the valid and binding obligation of the Trustee enforceable against
the Trustee in accordance with its terms; that the Trustee is in compliance,
with respect to acting as a trustee under such Indenture, with all applicable
laws and regulations; and that the Trustee has the requisite organizational and
legal power and authority to perform its obligations under such Indenture.

Based upon the foregoing, we are of the opinion that:

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
Page 8


1. Following effectiveness of the Registration Statement and the
due execution and delivery of an Indenture by the Group and
the Trustee named therein, the Debt Securities registered
under the Registration Statement, when duly authorized,
executed, authenticated and delivered against the full payment
specified therefor in accordance with the terms of the
Indenture and a definitive purchase, underwriting or similar
agreement and any other necessary agreement pertaining thereto
as described in the Registration Statement, will constitute
binding obligations of the Group in accordance with their
terms.

2. Following effectiveness of the Registration Statement, the
shares of Preferred Stock registered under the Registration
Statement, when duly authorized and issued against the full
payment specified therefor in accordance with the terms of a
definitive purchase, underwriting or similar agreement and any
other necessary agreement pertaining thereto as described in
the Registration Statement, which shall not have a value less
than the par value thereof, will be validly issued, fully paid
and nonassessable.

3. Following effectiveness of the Registration Statement, the
shares of Common Stock registered under the Registration
Statement, when duly authorized and issued against the full
payment specified therefor in accordance with the terms of a
definitive purchase, underwriting or similar agreement and any
other necessary agreement pertaining thereto as described in
the Registration Statement, which shall not have a value less
than the par value thereof, will be validly issued, fully paid
and nonassessable.

California Water Service Group
Attention: Peter C. Nelson
March 10, 2003
Page 9


This opinion letter is given as of the date hereof, and we express no opinion as
to the effect of subsequent events or changes in law occurring or becoming
effective after the date hereof. We assume no obligation to update this opinion
letter or otherwise advise you with respect to any facts or circumstances or
changes in law that may hereafter occur or come to our attention.

We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this firm under the heading
"Legal Matters" in the Prospectus included in the Registration Statement and in
any supplemental registration statement relating to the offering referred to in
the Registration Statement that is hereafter filed pursuant to Rule 462(b) of
the Commission under the Securities Act. In rendering this opinion and giving
this consent, we do not admit that we are an "expert" within the meaning of
Section 7 of the Securities Act and the Rules of the Commission thereunder.

Very truly yours,


/s/ Bingham McCutchen LLP
BINGHAM MCCUTCHEN LLP