William Tolson, Appellant, v. Allstate Insurance Company, Respondent.
 Arbitration - Judicial Review - Decision in Excess of Powers - Test. The test for vacation of an arbitration award under
496 TOLSON v. ALLSTATE INS. CO. Aug. 2001
108 Wn. App. 495
RCW 7.04.160(4), which provides for vacation when the arbitrator has exceeded arbitration powers, is whether an error of law appears on the face of the arbitration award.
 Arbitration - Judicial Review - Error of Law - What Constitutes - Internal Inconsistency. An arbitration award that contains statements that are inconsistent with the award of damages is legally erroneous on its face and is subject to vacation under RCW 7.04.160(4), which provides for vacation when the arbitrator has exceeded arbitration powers.
 Arbitration - Judicial Review - Scope - Arbitrator's Letter - Considered as a Whole. When reviewing an arbitration award, a court may view the arbitrator's letter as a whole if the question before the court is whether the arbitration award is sufficient to settle the dispute on the merits.
 Insurance - Underinsured Motorist - Benefit Limitation - Setoff of Benefits - Other Coverage of Same Policy. An insurance policy provision authorizing the insurer to deduct from uninsured motorist benefits amounts previously paid under other coverages provided by the policy is enforceable to the extent that the deduction does not result in the insured receiving less than full compensation for his or her loss.Nature of Action: Action for judicial review of an arbitration award. The plaintiff sought to have the award vacated on the basis of an alleged inconsistency between the amount of the award and statements made by the arbitrator in the arbitration award letter. Superior Court: The Superior Court for King County, No. 97-2-30543-8, Richard D. Eadie, J., on March 17, 2000, entered an order denying the plaintiff's motion to vacate the arbitration award. Court of Appeals: Holding that statements made in the arbitrator's award letter could be read as inconsistent with the amount of the award, in which case the award could be facially invalid, the court reverses the order and remands the case with directions to the trial court to seek clarification of the award from the arbitrator.
Randolph F. Jones (of Law Offices of Jones & Jones), for appellant.
Tamara K. Nelson, for respondent.
Aug. 2001 TOLSON v. ALLSTATE INS. CO. 497
108 Wn. App. 495
Becker, A.C.J. - William Tolson appeals from a trial court order denying his motion to vacate an arbitrator's award. Because the arbitrator's letter is internally inconsistent, it is legally erroneous on its face. Accordingly, we reverse with directions to seek clarification from the arbitrator.
In 1996, William Tolson was a passenger in a car that hit an abandoned vehicle in the middle of Interstate 5. The owner of the abandoned vehicle was uninsured. Tolson submitted an uninsured motorist claim as well as a claim for medical payments to Allstate, the insurer of the driver of the car in which Tolson was riding. Allstate paid $8,504.70 in medical payments for Tolson. The uninsured motorist claim went to arbitration, as permitted by the Allstate policy. The arbitrator found that Tolson suffered a cervical strain and a mild concussion due to the accident. The arbitrator awarded Tolson $3,418.30 in medical specials, $642.24 in past wage loss and $15,000 in general damages, for a total award of $19,060.54.
MOTION TO VACATE
 Tolson filed a motion in the trial court to vacate the arbitrator's award. One of the statutory grounds for vacating an award exists when the arbitrator has "exceeded" his powers, as demonstrated by an error of law on the face of the award. RCW 7.04.160(4); Lindon Commodities, Inc. v. Bambino Bean Co., 57 Wn. App. 813, 816, 790 P.2d 228 (1990).
The arbitrator's letter states that the evidence established that in the opinion of one doctor, Dr. Lucas, Tolson sustained memory loss on account of the accident. Nevertheless, the arbitrator did not award any damages for memory loss. The letter goes on to explain that the other
498 TOLSON v. ALLSTATE INS. CO. Aug. 2001
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doctor whose testimony he considered, Dr. Jeffrey Powell, thought the memory problem was "more attentional." Although the 1996 accident "may" have been a cause of the memory problem in Dr. Powell's view, the arbitrator stated that Dr. Powell was unable to define what percentage was attributable to the accident. The arbitrator's letter further states that Dr. Lucas deferred to Dr. Powell regarding the "extent of the brain injury, if any." The arbitrator's letter concluded that the record lacked medical testimony to establish the "extent" of Tolson's injury.
[2, 3] The arbitrator's letter can be read in at least two ways. The arbitrator may have found that Tolson sustained a brain injury, based on Dr. Lucas' testimony, but did not award any damages for the injury because Tolson failed to prove the extent to which it was attributable to the 1996 accident. As Allstate acknowledges, that would be erroneous. Once the finder of fact concludes that the defendant's conduct is the cause of an injury, the burden of segregating damages is upon the defendant. See Cox v. Spangler, 141 Wn.2d 431, 442, 5 P.3d 1265 (2000); Bennett v. Messick, 76 Wn.2d 474, 478-79, 457 P.2d 609 (1969). If Tolson proved that the 1996 accident caused any amount of memory loss or brain injury, then the burden of proving the percentage attributable to the accident was on Allstate, not on Tolson.
On the other hand, the arbitrator may not have found Dr. Lucas' testimony sufficient to establish that Tolson suffered any memory loss or brain injury on account of the 1996 accident. Perhaps the arbitrator thought that Dr. Lucas deferred to Dr. Powell as to the existence of brain injury as well as to the extent it could be attributed to the 1996 accident. If so, the award was not erroneous.
The problem is, we cannot tell from reading the letter which of these possibilities was what the arbitrator intended to say. Allstate contends that we should not read the letter as a whole, because the "face of the award" means only the actual dollar amounts awarded. Our cases, however, have not prevented a reviewing court from examining an arbitrator's letter when the question is whether the
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award is sufficient to settle the dispute on the merits. In Lindon, the arbitrator's letter stated that the contract had not been modified because there was no consideration for the modification. But the law does not require consideration to modify a contract. Accordingly, the reviewing court held there was an error of law on the face of the award, and remanded for a rehearing by the arbitrator. Lindon, 57 Wn. App. at 816.
This case presents a similar situation. The award excluding damages for memory loss is inconsistent with some of the statements in the arbitrator's letter, and consistent with others. We conclude the internal inconsistency amounts to an error of law on the face of the award. We reverse the trial court's denial of the motion to vacate, and direct the trial court to seek clarification from the arbitrator. See RCW 7.04.160(5); Lindon, 57 Wn. App. at 816. If the arbitrator states that he found no memory loss attributable to the 1996 accident, the order confirming the award should be reinstated. If the arbitrator states that he did find memory loss attributable to the accident, the matter should be remanded to the arbitrator for further proceedings.
 The parties submitted the issue of offset to the trial court. The court ruled that Allstate was entitled to offset the $8,504.70 paid under the medical payments coverage against the $19,060.54 uninsured motorist award. Allstate's policy states that an uninsured motorist award will be reduced by "all amounts paid or payable" under the personal injury protection, automobile medical payments or any similar medical payments coverage. This provision is valid and enforceable. Keenan v. Indus. Indem. Ins. Co. of the N.W., 108 Wn.2d 314, 738 P.2d 270 (1987); Schrader v. Grange Ins. Ass'n, 83 Wn. App. 662, 922 P.2d 818 (1996), rev'd on other grounds, Price v. Farmers Ins. Co. of Wash., 133 Wn.2d 490, 946 P.2d 388 (1997). Tolson appears to argue that such an offset is permissible only when the offset
500 KOCH v. MUT. OF ENUMCLAW Aug. 2001
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leaves the insured fully compensated. Assuming that to be true, he has failed to demonstrate that he will not be fully compensated. He will receive the full amount of the arbitration award. Tolson benefited from Allstate's payments of his medical specials by approximately $5,000 more than was actually due by virtue of the arbitration award. Reimbursing Allstate for its overpayment does not change the fact that Tolson will be fully compensated for the medical specials found to be attributable to the accident, as well as the full amount of general damages. The trial court properly allowed Allstate to offset the entire amount of medical payments previously paid.
Reversed and remanded.
Webster and Ellington, JJ., concur.