$1 million worth of sediment continues to enter Lake Decatur annually
Lake Decatur Watershed management will be the focus of a Decatur City Council study session on Monday, May 10 at 5:30 PM. The basis of the study session will be two reports produced by the city’s consultant Northwater Consulting. The recommendations within the report, if adopted by the council, will provide significant environmental benefits and improve drinking water quality including reducing the amount of sediment and nitrates that enters Lake Decatur. Below are several highlights from the reports which also includes new shoreline policy recommendations.
EACH YEAR, $1 MILLION OF SEDIMENT (BASED ON DREDGING COSTS) ENTERS LAKE DECATUR
The city of Decatur recently spent $92 million to dredge Lake Decatur and will spend over $160 million when interests, fees, and the costs of a previous dredging attempt are incorporated into the costs. While the city successfully increased its water supply through dredging, the city has not stopped sediment at its source, and will see its newly enlarged water supply reduced over time. Lake Decatur accumulates an estimated 160,000 tons of sediment annually and based on this accumulation rate, it will take 46 years for the lake to fill with sediment to the level prior to our latest dredging effort. Since 2014, when the dredging was initiated, ~$7 million of sediment has entered Lake Decatur.
REDUCING THE AMOUNT OF SEDIMENT AND NITRATES ENTERING LAKE DECATUR IS KEY GOAL
The objective of the Lake Decatur Watershed management plan is to reduce the amount of sediment and nitrates into Lake Decatur. It is critical to reduce the amount of sediment settling in Lake Decatur because it threatens the city’s long-term water security (i.e., more sediment results in a lower water capacity for the lake).
It is critical to reduce nitrates in the drinking water because of health concerns. Since the city of Decatur constructed its nitrate removal facility in 2002, the city has been in compliance with the United States Environmental Protection Agency's nitrate standard of 10 milligrams per liter (10 mg/L) and the city is to be commended for producing safe, high-quality drinking water. Since the federal nitrate standard of 10 mg/L was established in 1962, additional scientific research has found that stricter standards may be warranted. Because Decatur has a nitrate removal facility, the city has the opportunity to voluntarily adopt a stricter standard for drinking water. However, a long-term approach would be to reduce the amount of nitrates entering the water in the first place.
THE SOURCES OF SEDIMENT AND NITRATES ARE DIFFERENT
According to the report, “Lake Decatur Watershed Management Plan & Initiative – Long-Term Strategy”, the major sources of sediment and nitrate differs. Sediment sources include: 35% Decatur area (referred to as Bluffs in the report), 26% Sangamon River below Monticello and above lake, 21% Sangamon River above Monticello, 18% Big/Long and Sand Creeks, and <1% shoreline erosion. Thus, the majority of sediment settling in Lake Decatur originates from within Macon County. Because of strong, long-standing relationships with organizations such as the Macon County Soil and Water Conservation District and its partners, significant reduction in sediment going into Lake Decatur can be achieved.
Nitrate sources include: 59% Sangamon River above Monticello, 26% Sangamon River below Monticello and above lake, 9% Big/Long and Sand Creeks, 6% Decatur area (Bluffs), and <0.01% shoreline erosion. Thus, a substantial majority of nitrates is coming from outside the county and it will require the development of strong partnerships with neighboring counties and/or further reliance on the city’s nitrate removal facility.
PLANS FOR OAKLEY SEDIMENT BASIN NEED REVISION
One area of the “Lake Decatur Watershed Management Plan & Initiative – Long-Term Strategy” that will require further exploration are the plans for the Oakley Sediment Basin (referred to as the Lake Sediment Dewatering Basin in the report). Despite city council members requesting the city explore other alternatives for the 390-acre dewatering basin (such as solar energy, creation of a restored natural area including a wetland complex, and selling the sediment) prior to hiring the consultant, the report focuses on restoring the basin back to agriculture. This may not be the best use for the basin.
If the basin can be adequately dried, 390 acres may be enough land to generate 49 megawatts (MW) of solar energy (assuming 8 acres of land per MW), enough to provide power to 7,100 homes (assuming 1 MW produces enough energy to power 145 homes [as calculated through Solar Energy Industries Association Illinois Solar Fact Sheet]). With 33,415 housing units in Decatur, there is an opportunity to power over 20% of homes with renewable energy.
I AM HIGHLY SUPPORTIVE OF IMPLEMENTATING A COMPREHENSIVE LAKE DECATUR WATERSHED MANAGEMENT INITIATIVE
The current system of having the best farmland on planet earth rest at the bottom of Lake Decatur, city taxpayers spending over $160 million to remove it from the lake, and the city creating a giant mound of dirt that is hundreds of acres in size is unsustainable for farmers and city residents. Spending significantly lower amounts of money to reduce sediment from reaching Lake Decatur in the first place is the far more viable option and will serve as a model of sustainability for other cities.
CITIZENS ARE ENCOURAGED TO PROVIDE FEEDBACK TO CITY COUNCIL MEMBERS
If you would like to discuss city issues with a council member, phone numbers and email addresses for each council member can be found at the following link: https://www.decaturil.gov/mayor-and-council/council/.
PLEASE EXPRESS YOUR VIEWS AT CITY COUNCIL MEETINGS
Meetings take place at the Theater located on the second floor of the Decatur Civic Center (1 Gary K. Anderson Place). Free parking is available in the lot immediately south of the entrance. Citizens are encouraged to attend meetings and express their views. Citizens are allotted 3 minutes per person after council discussion of the study session topics.
AGENDAS FOR CITY COUNCIL MEETINGS ARE AVAILABLE ONLINE
An agenda and information about each agenda item for each city council meeting can be found at: https://www.decaturil.gov/mayor-and-council/council-meetings/.