Seneca Waste Solutions, Inc. Vs. Sheaffer Manufacturing Co., Llc And Sheaffer Pen Corporation, A Division Of Bic Usa Inc., 791 N.W.2d 407

Seneca Waste Solutions (contractor) submitted a September 7, 2006 bid to Sheaffer Pen Plant for decontamination/cleaning with a not-to-exceed price of $170,000.
The contract stated work would be on a time-and-materials basis but capped at $170,000 and incorporated Exhibit A (the bid and an estimating worksheet).
Exhibit A and related documents contemplated disposal of limited wastewater on-site, with 4,000 gallons to be handled by Heritage off-site.
During performance, Sheaffer directed off-site disposal of most rinsate; Heritage treated and disposed of far more wastewater (over 18,000 gallons).
Seneca invoiced $211,599.47; Sheaffer paid $145,980.87 before final invoice; the parties ultimately tendered $170,000 total, and Seneca rejected the tender and sued for the full amount.
The district court granted summary judgment for Sheaffer; the court of appeals vacated that ruling, and the Supreme Court granted further review to address contract integration and modification issues.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether the letter bid, worksheet, and vendor document are integrated into the contract.	Seneca argues these documents are fully integrated and allow exceeding the cap.	Sheaffer contends only limited portions are integrated and do not permit excess.	No; contract interpretation shows the cap remains effective despite integration.
Whether the contract was orally modified to permit a price above the cap.	Seneca asserts off-site disposal directed by Sheaffer modified the scope, allowing extra charges.	Sheaffer denies any modification or agreement to pay for extra work.	There is a genuine issue of material fact whether a modification occurred.
If modification existed, whether damages/damages calculation is premature on summary judgment.	Seneca would be entitled to the excess beyond 170k if modified.	Without a clear modification, no recovery beyond the cap.	Premature to determine damages pending factual resolution of modification.

Iowa Fuel & Minerals, Inc. v. Iowa State Bd. of Regents, 471 N.W.2d 859 (Iowa 1991) (interpretation of contracts to give effect to all terms; avoid superfluous provisions)
Passehl Estate v. Passehl, 712 N.W.2d 408 (Iowa 2006) (oral or implied modifications may bind despite written contract)
Whalen v. Connelly, 545 N.W.2d 284 (Iowa 1996) (modification by subsequent oral agreement possible when essential elements exist)
DeMuth Landscaping & Design v. Heggestad, 461 N.W.2d 354 (Iowa Ct. App. 1990) (extra work requires fair and reasonable value; post-agreement additions valid)
S. Hanson Lumber Co. v. DeMoss, 253 Iowa 204, 111 N.W.2d 681 (Iowa 1961) (post-contract agreements to modify/add to contract are enforceable)
Harlan v. Walderbach, 730 N.W.2d 198 (Iowa 2007) (summary judgment review uses view favorable to nonmovant; genuine issues of material fact)