TALBOT, J.

Plaintiffs appeal as of right the circuit court's order granting defendant's motion for summary disposition. We affirm.

The material facts of this case are undisputed. During the late 1920s, the Oakland County Drain Commissioner constructed a combined storm water and sanitary sewer system in an area of the county that was primarily vacant. Today, those sewers (hereafter referred to as the "Bloomfield Village System") serve residents and commercial establishments in portions of the City of Birmingham, the City of Bloomfield Hills, and the defendant Charter Township of Bloomfield. The Bloomfield Village System carries storm water and untreated sanitary sewage into the Evergreen Farmington Sewage Disposal System (EFSDS), a facility operated by the Oakland Drain Commissioner. From there, the untreated wastewater flows on to a treatment plant in the City of Detroit. Due to physical limitations of the EFSDS, the amount of wastewater defendant is permitted to discharge into the EFSDS at any given time is controlled by flow regulators within defendant's sewers. Other municipalities served by the EFSDS are subject to similar limitations.

During periods of heavy precipitation, the amount of wastewater in the Bloomfield Village System occasionally exceeds that which may be discharged into the EFSDS. When this happens, untreated sewage must be diverted elsewhere in order to prevent it from backing up into houses. This event, known as a combined sewer overflow (CSO), is a common problem associated with combined sewer systems. CSOs do not occur in separate (two-pipe) storm water and sanitary sewer systems because in two-pipe systems storm runoff does not mix with sanitary sewage. Until recently, CSOs occurring in the Bloomfield Village System were diverted directly into the Rouge River.

The Clean Water Act, 33 U.S.C. § 1251 et seq., was passed by Congress in part to address the problems caused by CSOs. Pursuant to the National Pollutant Discharge Elimination System (NPDES) permit program established under that Act, the Oakland County Drain Commissioner and the municipalities served by the Bloomfield Village System were required to take steps to abate the pollution of the Rouge River. In order to comply with the requirements of federal law — and in particular with a NPDES permit issued on October 12, 1992 — the municipalities agreed to construct the ten million gallon Lincoln Hills CSO Retention Treatment Basin (RTB). The RTB now serves as a repository for the excess wastewater that would otherwise have been diverted into the Rouge River. Wastewater diverted into the RTB is either held there until the flow rate decreases (at which time it is conveyed to the EFSDS), or treated and released into the river. The result is a cleaner Rouge River.

Construction of the RTB was financed by the Drain Commissioner through the sale of bonds. Each of the three municipalities using the RTB is responsible for paying its allocated share of the total cost of the project over a period of years. In order to raise money to pay its share, defendant created a special assessment district and adopted a special assessment roll in the amount of $8,887,016. See MCL 280.490; MSA 11.1490. The special assessment district, which includes over two thousand residences, commercial establishments, and the Oakland Hills County Club, is comprised of all of the parcels within the defendant township served by the Bloomfield Village System. Defendant levied rates ranging from $35 per year to $350 per year on each parcel within the district for a period of twenty years. All of the parcels inside the township but outside of the boundaries of the special assessment district are served either by (1) a two-pipe sewer system, or (2) private septic systems. Accordingly, before construction of the RTB, the only sanitary sewage from the defendant township diverted into the Rouge River was that from those properties within the special assessment district.

Plaintiffs are a group of property owners residing within the special assessment district. In 1994, they brought a class action suit in the Oakland Circuit Court challenging the creation of the special assessment district. Although the class was never certified, the parties stipulated that defendant would adhere to the result of the action with respect to all of the property owner's within the special assessment district. Defendant removed the case to federal court and moved for summary judgment. A federal district court granted defendant's motion for summary judgment, but its opinion was vacated by the Sixth Circuit Court of Appeals on the ground that the district court lacked removal jurisdiction. When the case was eventually remanded back to the Oakland Circuit Court, defendant moved for summary disposition pursuant to MCR 2.116(C)(10). The circuit court granted defendant's motion and plaintiffs brought this appeal.

On appeal, plaintiff's challenge the circuit court's decision to grant defendant's motion for summary disposition. We review de novo a trial court's decision on a motion for summary disposition. Spiek v. Dep't of Transportation, 456 Mich. 331, 337; 572 N.W.2d 201 (1998). Summary disposition may be granted under MCR 2.116(C)(10) when there is no genuine issue of material fact and the moving party is entitled to judgment as a matter of law. Quinto v. Cross Peters, 451 Mich. 358, 362; 547 N.W.2d 314 (1996). Because there is no factual dispute in this case, the question is simply whether defendant was entitled to judgment as a matter of law.

A special assessment is a levy upon property within a particular district. Kadzban v. Grandville, 442 Mich. 495, 500; 502 N.W.2d 299 (1993). Unlike a tax, which is imposed to raise revenue for general governmental purposes, a special assessment is designed to recover the costs of improvements that confer local and peculiar benefits upon property within a defined area. Id. Two requirements must be met in order for a special assessment to be deemed valid: (1) The improvement funded by the special assessment must confer a special benefit upon the assessed properties beyond that provided to the community as a whole, and (2) the amount of special assessment must be reasonably proportionate to the benefits derived from the improvement. See Id. at 501-502; Dixon Road Group v. City of Novi, 426 Mich. 390, 398-403; 395 N.W.2d 211 (1986). In order for an improvement to be deemed to have conferred a "special benefit," it must cause an increase in the market value of the land specially assessed. Kadzban, supra at 501; Dixon Rd, supra at 400-401. A determination of increased market value is necessary to determine whether the benefit is proportionate to the cost incurred. Dixon Rd, supra at 401. The decisions of municipal officers regarding special assessments are presumed to be valid and "generally should be upheld." Kadzban, supra at 502, quoting Dixon Rd, supra at 403.

Plaintiffs first contend that the special assessments are invalid because the RTB project conferred no special benefit on their property. We disagree. Plaintiffs assert that the only tangible benefit resulting from the RTB is a cleaner Rouge River. This benefit, they reason, has been conferred upon the community as a whole as much as it has upon those owning property within the special assessment district. Although we do not question the soundness of plaintiffs' reasoning, we believe they have overlooked the most direct and particularized benefit they receive from the RTB: It allows them to continue receiving sewer service from defendant. As a result of the change in federal law, defendant could not legally continue to provide sewer service to plaintiffs without first building the RTB or making an equivalent capital improvement. Plaintiffs admit as much in their brief on appeal, stating that "[t]he construction of the [RTB was] necessary for the Township to continue to operate its sewer system."

Despite this fact, plaintiffs contend that the change in federal law and the construction of the RTB had no practical effect on their use and enjoyment of the subject properties. Of course, plaintiffs' contention rests on the assumption that defendant had an affirmative duty to continue providing sewer service to them. Plaintiffs have offered no authority directly in support of this proposition. Moreover, we have found nothing to support the existence of such a duty. Cf. Kuriakuz v. West Bloomfield Twp, 196 Mich. App. 175, 177; 492 N.W.2d 757 (1992) (finding no duty to construct storm sewers); McSwain v. Redford Twp, 173 Mich. App. 492, 499-500; 434 N.W.2d 171 (1988) (finding no duty to construct sanitary sewers). While the NPDES permit obligated defendant to construct the RTB as a prerequisite to continued sewer service, it did not impose a duty to continue providing service. Accordingly, as a alternative to building the RTB, defendant could have discontinued sewer service to plaintiffs. Although it is highly unlikely that defendant would have elected to take this course of action, we must acknowledge that hypothetical possibility in order to view plaintiffs' claim in the proper perspective.

If defendant sought to provide new sanitary sewers to an area within the township lacking sewer service, it could fund the project through special assessments. See Kadzban, supra at 500-501; see also Shelby Charter Twp v. State Boundary Comm, 425 Mich. 50, 80; 387 N.W.2d 792 (1986) (Levin, J., dissenting); Oakland Co Drain Comm'r v. City of Royal Oak, 325 Mich. 298, 313; 38 N.W.2d 413 (1949). Historically, this is how defendant has funded the original construction of local sanitary sewers throughout the township. Given the fact that defendant could fund the original installation of a new sewer system through special assessments, we think it would defy logic to prevent defendant from using special assessments to fund the conversion of a legally defective sewer system into a legally proper sewer system especially when the alternative would have been to discontinue service. Cf. O'Rourke v. City of Stamford, 179 Conn. 342; 426 A.2d 311 (1979) (finding error in trial court ruling that property owners would receive no special benefit from conversion of a functional, private, polluting sewer system to a new, public, non-polluting system). For the reasons stated, we hold that construction of the RTB conferred a special benefit upon plaintiffs' properties.

Plaintiffs next argue that the special assessments are invalid because the RTB project did not result in an increase in the market value of their property. We disagree. Although it is undisputed that the construction of the RTB caused no discernible change in the market value of the properties within the special assessment district, we are not persuaded that this fact alone rendered the special assessment district invalid.

The essential question is not whether there was any change in market value, but rather whether the market value of the assessed property was increased as a result of the improvement. See Kadzban, supra at 501; Dixon Rd, supra at 400-401. Common sense dictates that in order to determine whether the market value of an assessed property has been increased as a result of an improvement, the relevant comparison is not between the market value of the assessed property after the improvement and the market value of the assessed property before the improvement, but rather it is between the market value of the assessed property with the improvement and the market value of the assessed property without the improvement. The former comparison measures the effect of time while the latter measure the effect of the improvement. In this case, it is clear that, after the change in federal law, the market value of plaintiffs' properties with the RTB in place was higher than it would have been without the RTB in place. This is so because without the RTB, defendant could not have continued to provide sewer service to plaintiffs. Without such service, the market value of plaintiffs' properties would undoubtedly have been substantially reduced. Because plaintiff offers no argument to the contrary, we will not upset the presumably valid judgment of defendant's municipal officers on this issue. Kadzban, supra at 502, quoting Dixon Rd, supra at 403.

Finally, plaintiffs argue that the special assessments are invalid under defendant's township ordinance regarding the determination of rates and charges for use of the township's sanitary sewer system. We disagree.

Bloomfield Township Ordinance No. 454 provides, in part, "The amount of the rates and charges shall be sufficient to provide for debt service and for the expenses of operation, maintenance and replacement of the system as necessary to preserve the same in good repair and working order." The ordinance further provides that, "[t]he rates and charges for operation, maintenance and replacement hereby established shall be uniform within the area serviced by the Township of Bloomfield." Plaintiffs assert that defendant is required under Ordinance No. 454 to fund its allocated share of the cost of the RTB through its uniform sewage treatment fees.

The rules of statutory interpretation apply to the interpretation of ordinances. Gora v. City of Ferndale, 456 Mich. 704, 711; 576 N.W.2d 141 (1998). If statutory language is clear and unambiguous, further judicial construction is neither necessary nor permitted, and the language must be applied as written. See Turner v. Auto Club Ins Ass'n, 448 Mich. 22, 27; 528 N.W.2d 681 (1995); Lorencz v. Ford Motor Co, 439 Mich. 370, 376; 483 N.W.2d 844 (1992). Because the clear and unambiguous language Ordinance No. 454 speaks only to the preservation of defendant's sanitary sewer system, we conclude that it does not apply to the funding of initial capital improvements. We further conclude that the RTB project was a capital improvement rather than a repair. Rather than merely "preserve the [system] in good repair and working order," construction of the RTB enhanced the operation of the system by preventing the release of pollution into the Rouge River. One of the functions of sewer systems is to abate pollution. See Andrews v. Jackson Co, 43 Mich. App. 160, 164; 203 N.W.2d 925 (1972). That the enhancement in function brought about by the RTB was mandated by federal law does not diminish the fact that the RTB was an improvement to the system. Therefore, we hold that Ordinance No. 454 did not require defendant to fund its allocated share of the cost of the RTB through its uniform sewage treatment fees.

Affirmed.