Alexander, C.J.
— More than a year after Skamania County approved Brian and Jody Bea’s application to build a residence and accessory structures on their property in the Columbia River Gorge National Scenic Area (Scenic Area), the Columbia River Gorge Commission (Gorge Commission) determined that the County’s decision to approve their application ran counter to the Columbia River Gorge National Scenic Area Act (Act), the Gorge Commission’s “Management Plan” for the Scenic Area, and Skamania County^ Scenic Area Ordinance (Ordinance). Consequently, it commenced an “enforcement action” against the County seeking to compel the County to nullify its decision and issue a new decision requiring siting of the residence and other structures at an alternate site. Following a “contested case” hearing before the Gorge Commission, the Commission concluded that the County’s decision approving the Beas’ application violated the Act, the Management Plan, and the Ordinance, and it directed the County to: (1) order the Beas to stop construction on the site; (2) invalidate its earlier decision approving the Beas’ application; and (3) issue a new decision that would comply with the Act, the Management Plan, and the Ordinance by, among other [35]*35things, requiring location of the Beas’ residence and other buildings at alternative sites on the parcel. Skamania County and the Beas subsequently appealed the Commission’s findings of fact, conclusions of law, and order to the Skamania County Superior Court. That court affirmed the Gorge Commission. We, thereafter, granted a petition by the Beas and Skamania County to directly review the superior court’s decision. The principal issue before us is whether the Gorge Commission had the authority to invalidate the County’s land use decision, notwithstanding its failure to appeal the County’s decision. We agree with Skamania County and the Beas that the Gorge Commission’s action was without authority of law and, therefore, reverse the superior court.
I. FACTS
A. The Columbia River Gorge National Scenic Area Act and the Skamania County Ordinance
In 1986, Congress passed the Columbia River Gorge National Scenic Area Act. 16 U.S.C. §§ 544-544p. The Act established the Columbia River Gorge National Scenic Area in a portion of Washington and Oregon.1 It authorized the two states to enter into a compact incorporating the Act and creating the Columbia River Gorge Commission for the purpose of administering the Act.2 Washington and Oregon thereafter negotiated such a compact and, in 1987, the legislature of each state ratified the Columbia River Gorge Compact.
[36]*36The Act required the Gorge Commission to establish a Management Plan for the Scenic Area, which the Commission is to use in administering nonfederal lands within the area. The Act also required each of the six counties within the Scenic Area to adopt a local land use ordinance, which was to be consistent with the Management Plan and subject to the Gorge Commission’s review and approval.3 In 1993, Skamania County dutifully adopted its Ordinance and the Gorge Commission reviewed and approved it.
The Ordinance requires applicants for land uses within the Scenic Area to submit their applications to the County’s Department of Planning and Community Development (Department). When an application is filed, notice of the application must be given by the Department to all “interested parties,”4 the Gorge Commission, the United States Forest Service, owners of property within 500 feet of the subject parcel, Indian Tribes listed in the Skamania County Code (SCC), and any other person or entity who has requested notice or whom the director has determined should receive notice of the particular application. The notice must include the name of the applicant, the location of the subject property, a brief description of the proposed action, the date by which the Department director will make a preliminary decision, and a statement that the Department will receive written comments concerning the application for 21 days from the date that the notice is mailed. Following the comment period, the Department director must issue a decision with findings of fact and conclusions of law. The director may impose any conditions that he or she determines are necessary to ensure that the [37]*37development complies with the Ordinance. The director then mails a copy of the decision, which includes notice of the right to appeal, to the applicant and all “interested persons.” SCO 22.06.050(C)(3).
Under the Ordinance, the director’s decision becomes final unless it is appealed by an applicant or interested party to the Skamania County Board of Adjustment within 20 days of the date the decision is rendered. If an appeal is filed, the Board of Adjustment considers the director’s decision de novo and, after a hearing and presentation of evidence, issues written findings of fact, conclusions of law, and an order. After the Board of Adjustment issues its decision, there can be a further appeal to the Gorge Commission. That appeal is heard on the record submitted by the Board of Adjustment.
The Ordinance does not expressly set out a time limit for appeals from the Board of Adjustment to the Gorge Commission. The Act does, however, provide that “[a]ny person or entity adversely affected by any final action or order of a county” may appeal such action or order within 30 days by filing with the Gorge Commission “a written petition requesting that such action or order be modified, terminated, or set aside.” 16 U.S.C. § 544m(a)(2); see also Or. Admin. R. (Columbia River Gorge Commission Rules) (hereinafter Gorge Commission Rules) 350-060-0000 through -0050.
B. The Beas’ Land Use Application
In November 1996, Brian and Jody Bea applied to Skamania County to build a one-story house, a barn, and a shop on 40 acres of property they owned within the Scenic Area. According to the application, the structures were to be situated on a bluff overlooking the Columbia River. Following receipt of the Beas’ application, the County gave notice to the Gorge Commission, an organization called “Friends of the Columbia Gorge” (Friends), and others5 that it was reviewing the application. Following the comment period, in which both Friends and the Gorge Commission made [38]*38comments, the director approved the Beas’ application. The director’s decision, which was entered on May 19, 1997, was subject to 33 conditions that were primarily related to a requirement in both the Management Plan and the Ordinance that every new development in the Scenic Area be “visually subordinate to its setting as seen from key viewing areas.” SCC 22.10.020(B)(1).
The director’s decision was sent to the Gorge Commission and Friends. It set forth the procedure for appealing the decision and specified that the decision would become final unless a written notice of appeal to the Board of Adjustment was filed within 20 days. Clerk’s Papers (CP) at 116. The decision was not appealed within that 20-day time period and, consequently, no proceeding before the Board of Adjustment has ever taken place. Neither was the decision appealed to the Gorge Commission under § 544m(a)(2) of the Act within 30 days after it became final.
The Beas thereafter began construction of their residence and adjacent buildings. During construction, the Beas allegedly violated several of the conditions that had been established by the director. The County also concedes that it was somewhat lax in enforcing the conditions established by the director.6 The County eventually discovered that the house was being built 10 feet north (away from the river) of where it was to be located pursuant to the Beas’ application. The County took no action, however, because it concluded that the slight change in location was insignificant.
By the summer of 1998, the Gorge Commission became concerned that the County’s decision approving the Beas’ application might be in violation of the Act, the Management Plan, and the Ordinance.7 Consequently, its executive director brought an “enforcement action” against the County pursuant to § 544m(a)(1) of the Act and Gorge [39]*39Commission Rule 350-030 by serving the County with a “Notice of Alleged Violation.” In its notice, dated July 27, 1998, the Gorge Commission alleged that the County’s approval of the Beas’ project violated the Act, the Management Plan, and the County’s Ordinance. It ordered the County to resolve the violation
in a manner resulting in: (1) immediate cessation of all development activity on Brian and Jody Bea’s property. . .; (2) revision of [the] Director’s Decision. . .; (3) issuance of an amended Director’s Decision in full compliance with the provisions of the Scenic Area Act, Management Plan, and . . . Ordinance . . ., including but, not limited to, siting the structures at alternative sites . . .; and, (4) bringing all development on the property into full compliance with the amended Director’s Decision, the Act, Management Plan, and . . . Ordinance!.]
CP at 123; see also CP at 124.
The County responded to the notice of alleged violation in an answer dated August 10,1998. In its answer, the County denied that “it ha[d] improperly or unlawfully interpreted or administered the scenic ordinance or the . .. Act” and stated that it “d[id] not plan to take any of the proposed disposition alternatives outlined by the Executive Director.” Admin. Hr’g R., Notebook at 17. The County also alleged, by way of affirmative defenses, that the Gorge Commission could not “now challenge the issuance of the Director’s Decision” because it had failed to file a notice of appeal or take other action before the decision became final and had “failed to exhaust its administrative remedies.” Id. at 19. It also claimed that the Gorge Commission lacked “standing, and jurisdiction.” Id.
Because the Gorge Commission and the County were not able to settle their differences, the matter became a “contested case” before the Gorge Commission under Gorge Commission Rule 350-030-070(1)8 and was set for a hear[40]*40ing. The Gorge Commission permitted Friends to intervene in the case and joined the Beas as participants.9
At the hearing, Skamania County moved to dismiss the action against it for lack of jurisdiction, arguing that the Gorge Commission lacked authority to challenge the validity of the County’s final approval decision because it had not appealed the director’s decision within 20 days of the date the decision was issued as provided by the Ordinance or 30 days of the date the decision became final as provided by the Act. The Gorge Commission denied the County’s motion. It concluded, as a matter of law, that, notwithstanding the fact that it had not appealed the County’s decision, it had authority to order the County to nullify or revise that decision pursuant to 16 U.S.C. § 544m(a)(1), which provides: “The Commission shall monitor the activities of counties . . . and shall take such actions as it determines are necessary to ensure compliance.” CP at 38-39. The Commission emphasized that this provision does not contain any limitation on when the Gorge Commission may act.
Following the hearing, the Gorge Commission issued findings of fact and conclusions of law. Significantly, it concluded that the County’s decision violated the Act, the Management Plan, and the Ordinance. It ordered the County to: (1) “immediately issue an order stopping the property owners from continuing any development activity on the site until and unless in accord with a County Decision issued in compliance with the remaining portions of this order”; (2) “revise [the] Director’s Decision. . . and [41]*41adopt a new or revised decision that is in full compliance with the provisions of the Scenic Area Act, Management Plan and Skamania County Land Use Ordinance ..., including but not limited to siting the structures at alternative sites”; and (3) “take all necessary steps to assure that development on the property in question is brought into full compliance with the Scenic Act, the Management Plan and the County’s ordinances.” CP at 50-51.
Skamania County and the Beas subsequently sought review of the Gorge Commission’s findings of fact, conclusions of law, and order in the Skamania County Superior Court. The Beas combined their petition for judicial review with a complaint against the Gorge Commission and Skamania County for damages. Skamania County and the Beas both cited § 544m of the Act as the source of the superior court’s jurisdiction to hear their appeal.10 Their petitions for judicial review were consolidated and heard, in July 1999, by a visiting Clark County Superior Court judge, sitting by designation.11 After the hearing, the superior court entered a “Final Judgment” in which it affirmed the Gorge Commission’s findings of fact, conclusions of law, and order. CP at 66-67. The court specifically adjudged “that the Columbia River Gorge Commission correctly applied 16 U.S.C. § 544m in the Decision.” CP at 67. Skamania County and the Beas subsequently petitioned this court for direct [42]*42review of the superior court’s judgment, and we granted their petition.
II. THE GORGE COMMISSION’S AUTHORITY UNDER 16 U.S.C. § 544m(a)
The principal issue before us is whether the Gorge Commission had authority under the Act to invalidate Skamania County’s land use decision, despite its failure to appeal the director’s decision to the County’s Board of Adjustment within 20 days of the date the decision was issued as provided by the Ordinance or to the Gorge Commission within 30 days of the director’s decision becoming final as provided by the Act.12 Put another way, does 16 U.S.C. § 544m(a)(1), as the Gorge Commission and Friends assert, confer upon the Gorge Commission the power to collaterally invalidate a final county land use decision after the appeals period has expired and construction has begun? Or, as Skamania County and the Beas contend, is the Gorge Commission’s authority to “modify, terminate, or set aside” final county land use decisions limited to appealing them pursuant to the Ordinance and § 544m(a)(2) of the Act?
A. Standard of Review
An agency’s conclusions of law, including its interpretations of statutes, are reviewed de novo under an “error of law” standard that permits us to substitute our judgment for that of the agency. Wenatchee Sportsmen Ass’n v. Chelan County, 141 Wn.2d 169, 175-76, 4 P.3d 123 (2000). Construction of the Act is a question of federal law.13 When we [43]*43review an agency’s construction of a federal statute, we must determine whether Congress has directly spoken on the question at issue and has clearly indicated its intent. Chevron U.S.A., Inc. v. Natural Res. Def. Council, Inc., 467 U.S. 837, 842-43, 104 S. Ct. 2778, 81 L. Ed. 2d 694 (1984). If it has, then “that is the end of the matter,” and we must give effect to that intent. Chevron, 467 U.S. at 842. While engaging in this analysis, we must look to the statute in its entirety — all of its provisions, its object, and its policy — not just at the particular language in isolation. Dole v. United Steelworkers of Am., 494 U.S. 26, 35, 110 S. Ct. 929, 108 L. Ed. 2d 23 (1990). If, on the other hand, “the statute is silent or ambiguous with respect to the specific issue, the question for [us] is whether the agency’s [interpretation] is based on a permissible construction of the statute. Chevron, 467 U.S. at 843. In such cases, the interpretation of the agency charged with administering the statute is generally entitled to deference, and to sustain it we need find only that the agency’s interpretation was sufficiently rational to preclude us from substituting our judgment for that of the agency. Chem. Mfrs. Ass’n v. Natural Res. Def. Council, Inc., 470 U.S. 116, 125, 105 S. Ct. 1102, 84 L. Ed. 2d 90 (1985). An agency’s interpretation of an ambiguous statute is not entitled to deference, however, if the interpretation is not within the agency’s area of expertise, Nat’l Ass’n of Gov’t Employees, Inc. v. Fed. Labor Relations Auth., 179 F.3d 946, 950 (D.C. Cir. 1999); see also Fed. Election Comm’n v. NRA Political Victory Fund, 513 U.S. 88, 97, 115 S. Ct. 537, 130 L. Ed. 2d 439 (1994), or if the interpretation is entirely inconsistent with the agency’s prior administrative practice. Bowen v. Georgetown Univ. Hosp., 488 U.S. 204, 212, 109 S. Ct. 468, 102 L. Ed. 2d 493 (1988).
B. Analysis
As indicated above, the first prong of the Chevron test [44]*44requires us to determine if Congress has directly spoken on the question at issue and if it has made its intent clear. If the answer to both questions is affirmative, then this court must give effect to Congress’ unambiguously expressed intent without regard to the interpretation adopted by the agency. It is only if we determine that the statute is silent or ambiguous on this particular question that we must evaluate the agency’s interpretation in light of Chevron’s second prong.
Skamania County and the Beas assert that Congress has directly spoken on the question before us and has clearly expressed its intent that the Gorge Commission’s authority to “modify, terminate, or set aside” County land use decisions is limited to appealing them pursuant to the Ordinance and the Act. They cite § 544m(a)(2) of the Act as the primary source for their argument. It provides:
Any person or entity adversely affected by any final action or order of a county relating to the implementation of [the Act] may appeal such action or order to the Commission by filing with the Commission within thirty days of such action or order, a written petition requesting that such action or order be modified, terminated, or set aside.
16 U.S.C. § 544m(a)(2).
The Gorge Commission, joined by Friends, contends that § 544m(a)(2)’s 30-day appeals provision does not apply to it. They also maintain that the Gorge Commission is not subject to the 20-day limit on appeals contained in the Ordinance. Rather, it asserts that it has plenary powers under the Act to take whatever actions that it determines are necessary, whenever it deems it necessary, to ensure that the Act, the Management Plan, and the Scenic Area counties’ land use ordinances are not violated. As support for this argument, the Gorge Commission and Friends cite § 544m(a)(1) of the Act, which provides: “The Commission shall monitor activities of counties pursuant to [the Act] and shall take such actions as it determines are necessary to ensure compliance.” 16 U.S.C. § 544m(a)(1).
We direct our attention first to the interpretation of the [45]*45Act proffered by the Gorge Commission and Friends. We agree that, when read in isolation, § 544m(a)(1) does appear to authorize the Gorge Commission to do anything that it believes is necessary to ensure that the Act is not violated. A court may not, however, read a provision in isolation when it is engaging in statutory interpretation; rather, we must read the provision in light of the statute as a whole. See Dole, 494 U.S. at 35. When read in this manner, we cannot say that the interpretation advanced by the Gorge Commission and Friends is consistent with the expressed intent of Congress.
As Skamania County and the Beas have observed, the Gorge Commission’s interpretation is inconsistent with other provisions of the Act. The flaw in the Gorge Commission’s interpretation is made apparent when one compares § 544m(a)(1) to § 544m(b)(2). Just as § 544m(a)(1) requires the Gorge Commission to take actions to “ensure compliance” by counties with the Act, § 544m(b)(2) permits citizens to commence a civil action against counties to “compel compliance” with the Act. If the Gorge Commission’s power to “ensure compliance” with the Act includes the power to invalidate a final county land use decision after the appeals period has expired, as it contends, it would make little sense to give the term “compel compliance” in the citizen suit provision any narrower interpretation. Yet, to do so would render the 30-day limitation on appeals a nullity.
The Gorge Commission’s interpretation of § 544m(a)(1) is also inconsistent with § 544m(b)(1)(B) of the Act. The latter subsection authorizes the Gorge Commission to “institute a civil action for an injunction or other appropriate order” to prevent any person or entity from utilizing lands in violation of the Act, the Management Plan, any county land use ordinance, or any other Commission or county order. The Gorge Commission’s interpretation of subsection (a)(1), when viewed against subsection (b)(1)(B), runs afoul of the general principle of statutory interpretation that “ ‘Congress acts intentionally and purposely when it includes particular language in one section of a statute but [46]*46omits it in another.’ ” BFP v. Resolution Trust Corp., 511 U.S. 531, 537, 114 S. Ct. 1757, 128 L. Ed. 2d 556 (1994) (quoting City of Chi. v. Envtl. Def. Fund, 511 U.S. 328, 338, 114 S. Ct. 1588, 128 L. Ed. 2d 302 (1994)). If Congress intended in § 544m(a)(1) to grant the Gorge Commission the power that it purported to exercise in this case — the power to collaterally invalidate a final county decision and to order a residence built in reliance on that decision moved to an alternate location — why did it not expressly say so when it gave the Gorge Commission authority to obtain that remedy through a civil action for an injunction in the very next subsection? Indeed, if the Gorge Commission has the power to administratively impose an injunction without considering equitable factors or even naming the property owner as a defendant in the proceeding, as it has done in this case, why would it ever bring a civil action for injunctive relief under § 544m(b)(1)(B)?
The Gorge Commission and Friends assert that their interpretation of the Act is consistent with the mandatory nature of the Commission’s enforcement obligation under the Act. They point to the Act’s legislative history, and argue that from it we may glean that Congress made a deliberate choice to make the Gorge Commission’s enforcement of the Act mandatory.14 If the Gorge Commission’s power to invalidate or modify a final county action or order is limited by the appeals provisions of the Ordinance and the Act, they argue, the Commission would not be able to fulfill its mandate under § 544m(a)(1) to “take such actions as it determines are necessary to ensure compliance” with the Act. See Resp. Br. of Columbia River Gorge Comm’n at 28-30; Resp’t Friends Opening Br. at 25-27. Since Congress made the considered choice to require the Gorge Commission to enforce the Act, the Gorge Commission asserts, it would then be inconsistent with congressional intent to interpret § 544m(a)(1) as a limitation on the Gorge Commission’s enforcement power.
[47]*47As Skamania County and the Beas point out, however, it is because the Gorge Commission’s enforcement obligation is mandatory that the appeals provisions must necessarily apply to it. Section 544m(a)(2) clearly allows for appeals of final county decisions by persons and entities other than the Gorge Commission. It also clearly limits appeals to those made within 30 days from the date of the county decision being appealed. If, as the Gorge Commission argues, it is not bound by the 30-day limit on actions to invalidate or modify final county decisions, and, in addition, it has a mandatory obligation to enforce the Act, then any person or entity who objects to a final county decision, but who has failed to file a timely appeal, may circumvent the 30-day limit on appeals by bringing the matter to the attention of the Gorge Commission, which would be required by law to invalidate or modify the final county decision. Indeed, in this instance, Friends made a presentation to the Gorge Commission over one year after the County’s decision approving the Beas’ application became final, pointing out deficiencies in the Beas’ application and the County’s approval decision and demanding that the Gorge Commission take action to bring the Beas’ development into compliance with the Act. Whether or not this presentation influenced the Gorge Commission’s decision to commence an enforcement action against the County, it illustrates Skamania County’s and the Beas’ point that if the Gorge Commission is not bound by the 30-day limit on actions to modify, terminate, or set aside final county decisions, then nobody is.
We now turn to Skamania County’s and the Beas’ interpretation of the Act. We find ourselves in agreement with them that, under a plain reading of § 544m(a)(2), the Gorge Commission must file a timely appeal in order to invalidate or modify a county decision. We reach this conclusion because the Gorge Commission, whose duty it is to ensure compliance with the Act, is undeniably an “entity” that is “adversely affected” by a final county land use decision in conflict with the Act. Further, unlike the inter[48]*48pretation advanced by the Gorge Commission and Friends, Skamania County’s and the Beas’ interpretation of § 544m(a) is consistent with the other enforcement provisions of the Act.
Under Skamania County’s and the Beas’ interpretation of the Act, § 544m(a)(1) mandates the Gorge Commission to enforce the Act, but gives it discretion as to how to fulfill this obligation from among those powers expressly delegated to it in other provisions. For example, the Gorge Commission may appeal a final county action or order within 30 days under § 544m(a)(2); it may bring an administrative action under § 544m(a)(3) to assess a civil penalty against any person or entity who willfully violates any scenic laws; it may institute a civil action for an injunction or other appropriate order under § 544m(b)(1)(B) to prevent any person or entity from violating the Act; and, pursuant to the Management Plan, it may monitor and evaluate county decisions, substantively review and comment upon land use applications, and consult with county officials concerning ways to improve the county’s review and approval process. As we have noted above, the Gorge Commission and Friends would have us interpret § 544m(a)(1) as authorizing it to do anything that it determines is necessary to enforce the Act. In our view, it would have been unnecessary and redundant for Congress to have expressly delegated the aforementioned other powers to the Gorge Commission and to the secretary of Department of Agriculture if the Commission already had the broader power under § 544m(a)(1) that it has purported to exercise here.
Our conclusion in this regard is bolstered by our observation that Skamania County’s and the Beas’ interpretation of the Act is consistent with the strong public policy favoring administrative finality in land use decisions. Federal courts have long recognized that:
[Statutory time limits on petitions for review of agency action are jurisdictional in nature. These limitations serve the “important purpose of imparting finality into the administrative process, thereby conserving administrative resources.” Fur[49]*49thermore, timeliness requirements reflect “a deliberate congressional choice to impose statutory finality on agency orders, a choice we may not second-guess.”
Eagle-Picher Indus, v. United States Envtl. Prot. Agency, 759 F.2d 905, 911 (D.C. Cir. 1985) (footnotes omitted). We have also recognized a strong public policy supporting administrative finality in land use decisions. In fact, this court has stated that “[i]f there were not finality [in land use decisions], no owner of land would ever be safe in proceeding with development of his property.... To make an exception . . . would completely defeat the purpose and policy of the law in making a definite time limit.” Deschenes v. King County, 83 Wn.2d 714, 717, 521 P.2d 1181 (1974).
By establishing a 30-day appeal period in § 544m(a)(2), we believe that Congress sought to promote this policy of administrative finality in order to avoid unjust results. If we accepted the Gorge Commission’s argument that it has the power to invalidate or modify a county decision approving a development in the Scenic Area at any time, however, an unjust result would be produced. We say that because the record shows that the Beas’ residence was over half completed at the time the Commission ordered the County to invalidate the decision upon which the Beas had relied in proceeding with construction. It is hardly just to require them now to relocate the half-finished building. In the final analysis, the Gorge Commission’s interpretation of the Act is inconsistent with this principle of administrative finality in land use decisions in that there is no principled limitation on the Gorge Commission’s exercise of its purported power. We believe that had Congress intended to eviscerate the nearly universal rule of administrative finality in land use decisions and grant the Gorge Commission the unusual power that it claims to have, it would have said so expressly and unequivocally.
The Beas also raised a compelling argument concerning delegation and agency. Prior to the effective date of the Ordinance, the Gorge Commission reviewed all applications for development within the Scenic Area under interim [50]*50guidelines. See 16 U.S.C. § 544h(c). If the Gorge Commission had approved the Beas’ application under those guidelines and the decision had become final because it was not appealed, the Gorge Commission could hardly have argued that § 544m(a)(1) allowed it to go back and invalidate its own decision if it later determined that it had made a mistake. When the Gorge Commission approved the Ordinance as consistent with the Management Plan, the authority that the Gorge Commission had under the interim guidelines was transferred to the County, with the Gorge Commission retaining only the right to comment on land use applications, the right to appeal the director’s decisions to the County’s Board of Adjustment, and final appellate authority over all final county decisions. It stands to reason that if the Gorge Commission fails to exercise the authority that it retained for itself when it approved the Ordinance, then it is estopped from challenging the validity of such final county decisions just as if it had made the decision itself.
As an additional point, only Skamania County’s and the Beas’ interpretation of the Act is consistent with Congress’ intent that the Act create a partnership between local and state governments and the federal government. See 132 Cong. Rec. S15628-02 (daily ed. Oct. 8, 1986) (statements of Sen. Hatfield (Or.) and Sen. Gorton (Wash.)). The Gorge Commission appears to view its role at the beginning of the application process as minimal, as it rarely provides substantive comments on development applications and does not routinely make site visits to properties. Yet clearly, from a policy standpoint, it is far better to have the Gorge Commission take an active role at the beginning of the application process — to substantively review land use applications, make site visits where necessary, give informed comment on applications, and appeal decisions where it believes that the County has misapplied the law or misunderstood the facts — than to allow the Gorge Commission to passively stand by until construction has begun and then to determine whether developments, as constructed, comply [51]*51with the Act, the Management Plan, and the Ordinance.
In this case, the Gorge Commission made no substantive comments on the Beas’ application and site plan or the director’s decision, until over one year after construction had begun. Nevertheless, it now contends that both the site plan and application were inadequate when submitted. Further, the primary violations that the Gorge Commission found in the director’s decision concern the location and height of the Beas’ residence — both of which would have been apparent by even the most cursory review of the site plan and the director’s decision. In short, the litigation in which the parties are embroiled could have been avoided had the Gorge Commission become involved in the process earlier, taking advantage of the comment and appeals period. But the Gorge Commission’s interpretation of the Act removes any incentive for the Gorge Commission to work together with the Scenic Area counties to engage in early and thorough review of proposed developments.
The Gorge Commission and Friends take issue with Skamania County’s and the Beas’ interpretation of the Act, contending that it would be anomalous to interpret § 544m(a)(2) to require the Gorge Commission to appeal a decision by the county to itself. This argument runs counter to Friends’ contention that the “[ajppellants confuse the dual roles of the Commission.” Resp’t Friends Opening Br. at 20. As Friends concede, the Gorge Commission has dual roles under the Act: enforcement and quasi-judicial. As it notes, if a person or entity appeals a final county decision to the Gorge Commission, the Gorge Commission acts as a judicial body and may modify, terminate or set aside the county’s final decision. Likewise, if the Gorge Commission brings an enforcement action against a county, as in this case, the Gorge Commission also presides over the case and renders a decision in its quasi-judicial capacity. Thus, it is no more anomalous for the Gorge Commission to appeal a final county decision to itself, in its quasi-judicial capacity, than it is for the Gorge Commission to bring an enforcement action against a county, to be heard and decided by [52]*52the Gorge Commission also sitting in its quasi-judicial capacity.
Friends also asserts that “Appellants’ construction of subsection (a)(1) makes the terms ‘shall take whatever actions as it determines are necessary to ensure compliance’ surplusage, since the Commission would already have that authority under subsection (a)(2).” Resp. Br. of Columbia River Gorge Comm’n at 26. We disagree. In our view, § 544m(a)(2) can, quite easily, be read to apply to the Gorge Commission without rendering § 544m(a)(1) surplusage. That is so because each provision uses different language to describe the types of county activities over which the Gorge Commission has oversight. Subsection (a)(1) uses general language and gives the Gorge Commission a general power to monitor the “activities of counties” and to take action to ensure that the “activities of counties” comply with the Act. Subsection (a)(2), on the other hand, uses specific language and concerns only “final action [s] or order [s] of a county relating to the implementation of [the Act].” Thus, while subsection (a)(1) concerns the entire universe of activities that a county might engage in, subsection (a)(2) sets aside for special treatment only those “county activities” which are “final action [s] or order [s]” relating to implementation of the Act. Subsection (a)(1) provides no time limitation on actions taken with respect to the “activities of counties” in general; however, subsection (a)(2) requires that actions to “modif[y], terminate[], or set aside” final county “action[s] or order[s]” be brought within 30 days of that decision and in the form of an appeal.
Finally, amici curiae Multnomah County and the United States argue that if the Gorge Commission does not have the power under § 544m(a)(1) to invalidate final county land use decisions in violation of the Act, then there will be a lack of uniformity in the counties’ interpretations of scenic laws and the Gorge Commission will not be able to “ensure compliance” with the Act at the county level. Multnomah County’s Br. of Amicus Curiae at 4; see United States of America’s Br. of Amicus Curiae at 5-7. These arguments [53]*53miss the mark in two respects: First, Skamania County’s and the Beas’ interpretation of the Act promotes uniformity at least as well as, if not better, than the Gorge Commission’s interpretation. By having final appellate authority over all county land use decisions, and by exercising such authority to correct misinterpretations or misapplications of the law, the Gorge Commission would have the final say over application and interpretation of the Act by counties within the Scenic Area. Likewise, the Gorge Commission would have final say over the Management Plan and ordinances. The Gorge Commission’s appellate authority can be invoked in every instance, not just when an enforcement action is brought. Second, development of the law in this appellate/quasi-judicial setting would be more principled and less arbitrary than if the Gorge Commission simply maintains enforcement actions whenever its attention is drawn to a complaint that a decision may be in violation of the Act, the Management Plan, or a county’s ordinance.
Even though § 544m(a)(1) of the Act does not confer upon the Gorge Commission the power to collaterally invalidate final county land use decisions and order that residences built in reliance on such decisions be relocated, the Gorge Commission still has ample means at its disposal to ensure compliance with the Act. In that regard, the Gorge Commission can substantively review land use applications and site plans when it receives notice of a county’s development review. It can then attempt to shape the county’s decision through written comments and suggestions. If it disagrees with a county’s approval decision, it can appeal the decision to the county’s Board of Adjustment. If still dissatisfied with the decision, the Gorge Commission can appeal that decision to itself, and decide, in its quasi-judicial capacity, whether the county correctly interpreted and applied the Act, the Management Plan, and the local ordinance. In addition, if it believes that a property owner or county is intentionally violating the Act, the Management Plan, or the county’s ordinance, it may bring an administrative [54]*54action under § 544m(a)(3) to assess civil penalties. It can also exercise its power under § 544m(b)(1)(A) to institute a civil action for an injunction or other appropriate order to prevent a person or entity from violating these laws. Finally, if it concludes that an injunction or other order would be insufficient, it may request the secretary of the Department of Agriculture to exercise the government’s power under § 544g to condemn and acquire any lands used in a manner inconsistent with the Act, the Management Plan, or county ordinance. All the while, it should be monitoring and reviewing county land use decisions to try to improve the general manner in which counties make land use decisions and implement the Act. In short, the Gorge Commission has many tools at its disposal. Collateral administrative invalidation of final county approval decisions is not, however, one of them.
The Gorge Commission and Friends assert that their interpretation of the Act is entitled to deference under Chevron. However, as we have noted above, an agency’s interpretation is relevant under Chevron only if the statute is silent or ambiguous on the statutory question at issue. Because we have concluded that the intent of Congress is clear on this issue, it is unnecessary for us to proceed to the second prong of the Chevron test. We note, however, that even if we were to conclude that the Act is silent or ambiguous on this point, the Gorge Commission’s proffered interpretation would not be entitled to any deference by this court. We say this because the question that is before us is not a matter within the Gorge Commission’s area of expertise. Nat’l Ass’n of Gov’t Employees, 179 F.3d at 950; Fed. Election Comm’n, 513 U.S. at 97. The Gorge Commission’s interpretation is also not entitled to deference by the court for the reason that it is wholly unsupported by its prior administrative practice. Bowen, 488 U.S. at 212. In that regard, it concedes that there are numerous other developments within the Scenic Area that are currently in violation of the Act, the Management Plan, and the Scenic [55]*55Area counties’ ordinances.15 Despite that fact, with this one exception, the Gorge Commission has never sought to collaterally invalidate a final county land use decision or assert that it has such power under § 544m(a)(1).
Further, when the Gorge Commission reviewed and approved the Ordinance as consistent with the Management Plan and Act, why did it not require inclusion of a provision explaining or referring to its purported collateral invalidation power under § 544m(a)(1)? Indeed, the Management Plan itself, a document that the Gorge Commission was directed by Congress to adopt to implement the Act, is entirely devoid of any reference to the power that the Gorge Commission now claims to have. To the contrary, the Management Plan evidences that the Gorge Commission envisioned its own role under § 544m(a)(1) as one of monitoring, review, evaluation, and consultation, focused on assessing the overall effectiveness of the entire permit process and the general way that the Management Plan was being implemented by the counties.
As a final point, we note that even if we were required to afford deference to the Gorge Commission’s interpretation of the Act under Chevron’s second prong, we would still be bound to reject it. We say that because the Gorge Commission’s interpretation is not sufficiently rational as to preclude this court from substituting its judgment for that of the agency. See Chemical Mfrs., 470 U.S. at 125. As indicated above, it contradicts the plain language of §§ 544m(a)(2), 544m(b)(2), and 544m(b)(1)(B), the overall statutory scheme of the Act, the strong public policy favoring finality in land use decisions, and Congress’ intent that the Gorge Commission and the Scenic Area counties work together in a partnership to implement the Act.
III. OTHER ISSUES RAISED BY THE PARTIES
The Gorge Commission and Friends have raised [56]*56another argument that, they assert, constitutes a basis for affirming the Gorge Commission’s findings of fact, conclusions of law, and order, even if we reject their interpretation of § 544m(a)(1) and (a)(2) and conclude that the Commission was required to file a timely appeal in order to invalidate or modify the County’s approval decision. The Gorge Commission and Friends contend that they could not have filed a timely appeal in this case because, they allege, it did not become apparent to them until after the Beas’ construction began that the director’s decision violated the law. They also cite to our decisions in Eastlake Community Council v. Roanoke Associates, Inc., 82 Wn.2d 475, 513 P.2d 36 (1973); Steele v. Queen City Broadcasting Co., 54 Wn.2d 402, 341 P.2d 499 (1959); Hull v. Hunt, 53 Wn.2d 125, 331 P.2d 856 (1958); Nolan v. Blackwell, 123 Wash. 504, 212 P. 1048 (1923); and the Court of Appeals decision in Radach v. Gunderson, 39 Wn. App. 392, 695 P.2d 128, review denied, 103 Wn.2d 1027 (1985), and assert that the director’s decision is not entitled to any finality because it was “illegal” when issued.
We do not believe that the superior court can be affirmed on this basis. Even if we were to hold that the Gorge Commission’s failure to timely appeal the County’s approval decision were excused for the reasons asserted by the respondents, this would not authorize the action that the Gorge Commission took in this case. We reach this conclusion because the Gorge Commission did not attempt to file a late appeal of the director’s decision under the Ordinance or § 544m(a)(2) of the Act, when it allegedly learned that the director’s decision violated the Act, the Management Plan, and the Ordinance, as it should have done under this line of reasoning. Nor did it commence a civil action for injunctive relief under § 544m(b)(1)(B) of the Act. Rather, the Gorge Commission commenced an administrative action in an effort to collaterally invalidate that decision — an action that we have found to have been unauthorized by the Act.
Skamania County and the Beas have also argued that the Gorge Commission’s order is arbitrary and capri[57]*57cious. In light of our decision here, it is unnecessary for us to resolve the arguments made by the parties on this issue. It is sufficient to say that the Gorge Commission’s order is reversible on the basis that it was arbitrary and capricious because agency action that is in violation of a statute is, by definition, arbitrary and capricious, or contrary to law. It is likewise unnecessary for us to address the challenges to various findings of fact that have been made by Skamania County and the Beas. For the reasons stated above, we have concluded that the Gorge Commission had no authority under the Act to maintain the proceeding against the County that has led to this appeal. It follows, therefore, that all of the findings of fact the Gorge Commission made in that proceeding are of no moment.16
IV. CONCLUSION
We are satisfied that the intent of Congress in enacting § 544m(a)(1) and (a)(2) of the Act is clear. Section 544m(a)(1) of the Act does not authorize the Gorge Commission to collaterally invalidate final county land use decisions. Rather, any Gorge Commission action to modify, terminate, or set aside a final county decision must be taken pursuant to the Ordinance and the Act and in the form of a timely appeal. It follows, therefore, that the action that the Gorge Commission took against the County and the Beas in this case was contrary to law. Accordingly, we reverse the order of the Skamania County Superior Court [58]*58affirming the Gorge Commission and vacate the Gorge Commission’s findings of fact, conclusions of law, and order. We note, however, that our disposition of this case is without prejudice to the Gorge Commission to pursue other remedies that may be available to it under the Act and the Ordinance.
Reversed.
Smith, Johnson, Madsen, Sanders, and Bridge, JJ., and Guy, J. Pro Tern., concur.