In 2001, N. Alan McKee sought to locate a solid waste handling facility in the City of Geneva (City). In accordance with OCGA § 12-8-24 (g), he requested written verification from the City that the proposed facility did not violate any zoning or land use ordinances and that it was consistent with all solid waste management plans (SWMP). No zoning or land use ordinance precluded McKee from proceeding. However, his request for verification was denied on the ground that the proposed facility did not comply with the City’s SWMP. McKee then filed a mandamus and declaratory judgment action seeking to compel the City to issue the verification. After conducting a hearing, the trial court denied the petition, from which order McKee appeals directly. See Mid-Ga. Environmental Mgmt. Group v. Meriwether County, 277 Ga. 670, 671 (1) (594 SE2d 344) (2004).
1. OCGA § 12-8-24 (g) provides, in relevant part, that the verification must attest to the proposed facility’s compliance “with the *412local, multijurisdictional, or regional [SWMP] developed in accordance with standards promulgated pursuant to this part subject to the provisions of Code Section 12-8-31.1 . . . .” The City approved a regional SWMP in 1993, and in 1995, it further approved a multi-jurisdictional Comprehensive Plan (CP). The trial court agreed with the City’s position, and held that McKee’s proposed facility must comply with the provisions of the CP, as well as those of the SWMP.
McKee contends that the 1995 CP is inapplicable, and urges that he is entitled to verification because he proposes to develop a solid waste handling facility that fully complies with the SWMP as the City approved it in 1993. The SWMP, as it was originally approved, does not expressly address solid waste handling facilities in substantive terms. Instead, it merely provides that one of its “GOALS” was
[t]o insure that proposed solid waste handling facilities are located in areas suitable for such developments in [the] Talbot County [CP] which will be developed in 1994-95 and not in areas of Talbot County identified as having environmental or other significant development or land limitations.
Thus, the SWMP, as it was approved in 1993, did not preclude locating a facility for the handling of solid waste in the City, because no unsuitable locations for such facilities were identified. Thereafter, the City never formally amended the SWMP so as to incorporate the CP.
The trial court’s conclusion that both the SWMP and CP are applicable is contrary to the controlling statutory provision. By its terms, OCGA § 12-8-24 (g) does not require compliance with both a SWMP and a CP. Instead, as previously noted, it provides that the proposed facility must comply only with a “[SWMP] developed in accordance with standards promulgated pursuant to this part subject to the provisions of Code Section 12-8-31.1 . . . .’’As it was approved by the City in 1993 and as it remained in succeeding years, the SWMP addressed solid waste handling facilities only in indefinite and vague terms of future “GOALS.”
The City contends that the principle of incorporation by reference is applicable, so that, after 1995, the CP became a part of the SWMP. As a general rule, the adoption of documents through the principle of incorporation by reference is valid where the document is sufficiently identified and is made a part of the public record. See Friedman v. Goodman, 219 Ga. 152, 159 (3) (b) (132 SE2d 60) (1963). Here, however, the CP was not even in existence when the City contends that it was incorporated by reference into the SWMP. The City does not cite any authority for the proposition that the principle of incorporation by reference can apply prospectively to a document *413which has yet to be filed or made a public record because it is non-existent. To the contrary, that proposition appears to be inconsistent with the cases which recognize the principle. See generally Western & Atlantic R. v. Peterson, 168 Ga. 259, 265 (5) (147 SE 513) (1929) (ordinance identified the material being adopted only as “new ordinances as compiled by Attorney Fred Morris” and gave no indication where it was filed or that it was made a public record).
In any event, the principle of incorporation by reference applies only “[i]n the absence of statutory or charter provision to the contrary . . . .” Friedman v. Goodman, supra at 159 (3) (b). OCGA § 12-8-24 (g) unequivocally states that a SWMP must be “developed in accordance with standards promulgated pursuant to this part subject to the provisions of Code Section 12-8-31.1 . . . .” OCGA § 12-8-31.1 (a), in turn, requires that a city develop or be included in a “comprehensive [SWMP] not later than July 1,1993.” Under OCGA § 12-8-31.1 (b), the SWMP “shall, at a minimum, . . . identify those sites which are not suitable for solid waste handling facilities based on environmental and land use factors.” In accordance with this statutory scheme, a SWMP, as originally developed, was required to identify unsuitable sites, not express vague “GOALS” as to the identification of such sites in the future. Therefore, even assuming that incorporation by reference can ever apply prospectively, subsections (a) and (b) of OCGA § 12-8-31.1 are statutory provisions which mandate a comprehensive SWMP by 1993, and thereby preclude the City’s reliance on that principle to incorporate the 1995 CP into its SWMP. If the City intended for its comprehensive SWMP to include the substance of the CP, it should have amended the 1993 plan formally. It did not do so.
The dissent places great emphasis on the fact that the SWMP was reviewed and approved by the Georgia Department of Natural Resources and the Georgia Department of Community Affairs more than a decade ago. Although those agencies have administrative authority in the area of solid waste management, the courts have the ultimate authority to construe statutes and to determine whether there has been compliance therewith.
While the dissent urges that this Court must defer to the [administrative agencies’] construction of the statute [s] in question, we are not bound to blindly follow such an interpretation and decline to do so here. Administrative rulings are not binding on this Court, and will only be adopted when they conform to the meaning which the appellate court deems should properly be given. [Cit.] Thus, we are authorized to make an independent determination as to whether the interpretation of the administrative agency correctly *414reflects the plain language of the statute and comports with the legislative intent. [Cit.]
Sawnee E.M.C. v. Ga. Pub. Svc. Comm., 273 Ga. 702, 706 (544 SE2d 158) (2001).
It is well settled that an erroneous administrative interpretation and application of plain and unambiguous provisions of the law, no matter how long applied and well established nor how long acquiesced in, cannot be effective to amend, add to, or take from the law. [Cits.]
Williams v. Farr, 97 Ga. App. 881, 887 (104 SE2d 713) (1958), rev’d on other grounds, 214 Ga. 525 (106 SE2d 14) (1958).
Therefore, for purposes of resolving this appeal, it is immaterial whether the SWMP, as it was approved by the City and the administrative agencies, is an ordinance which has the force of law or a plan which does not. Compliance with applicable statutory requirements does not depend on whether those requirements relate to the approval of a plan or the enactment of an ordinance. Here, the controlling statutory provisions require that the City be included in a “comprehensive” SWMP by a date certain and that the SWMP must, “at a minimum,” identify the sites which are unsuitable for solid waste handling facilities. OCGA § 12-8-31.1 (a), (b). Under the evidence, the City did not comply with that statutory mandate, notwithstanding the administrative approval of its efforts to comply. Since the City did not comply with the applicable statutory requirement, it cannot rely on its SWMP to deny McKee’s request for verification under OCGA § 12-8-24 (g).
2. In addition to concluding that the CP was applicable, the trial court noted
that although [McKee] claims this is a solid waste handling facility, the proposed plan also clearly includes solid waste disposal practices which are specifically addressed in the regional [SWMP],... [S]ince the facility could be considered a solid waste disposal area . . . , the City . . . was correct in considering environmental factors in determining whether to grant the verification requested. . . . The City, after considering the aforementioned environmental factors, was correct in determining that the proposed facility did not meet provisions of the [SWMP].
*415McKee contends that the trial court erred in addressing his request for verification from the perspective of a solid waste disposal facility, rather than a solid waste handling facility.
The dispositive issue was not whether McKee should be issued a final permit, but rather whether he was entitled to the preliminary verification from the City mandated by OCGA § 12-8-24 (g). Thus, the trial court was not called upon to classify the proposed facility. McKee’s intent was to seek from the Director of the Environmental Protection Division of the Department of Natural Resources (Director) a permit for a solid waste handling facility. In accordance with OCGA § 12-8-24 (g), the sole question before the trial court was whether the proposed facility was or was not consistent with the terms of the City’s SWMP regarding solid waste handling facilities. If it was, then the City was required to issue a verification and McKee would then be entitled to apply for a permit from the Director. Whether, due to any additional disposal practices, the proposed facility was disqualified from consideration for issuance of a permit for a solid waste handling facility was a question for the Director. Therefore, the trial court’s determination that McKee was not entitled to verification based upon its denomination of the facility as one partially intended for solid waste disposal, rather than intended exclusively for solid waste handling, was erroneous.
3. Mandamus is an extraordinary remedy which is available when the petitioner can show a clear legal right to the relief sought or a gross abuse of discretion. Mid-Ga. Environmental Mgmt. Group v. Meriwether County, supra at 672 (2). McKee’s right to verification under OCGA § 12-8-24 (g) is dependent only upon whether his proposed facility complies with the provisions of the City’s SWMP regarding solid waste handling facilities. Since that facility would be located on a site which is not identified as unsuitable in the unamended 1993 SWMP, it does comply with that plan. Therefore, McKee was entitled to the verification, so that he could seek issuance of a permit from the Director. Compare Mid-Ga. Environmental Mgmt. Group v. Meriwether County, supra.
Judgment reversed.
All the Justices concur, except Hunstein, P. J., and Benham, J., who dissent.