WASTE WATER TREATMENT PLANT (WWTP)

WASTE WATER TREATMENT PLANT (WWTP)
Rowe Incorporated reviewed the operating records from the Village’s wastewater treatment plant from 1995 and 1996 to evaluate the plant’s ability to handle additional customers.
In general, operating records indicate that effluent from the Village’s treatment plant routinely is well within the limits established by the NPDES permit with the exception of the percentages of BOD and suspended solids removal. The permit limit for both of these is established at providing at least 85% removal of the total BOD and suspended solids load of the influent raw wastewater to the plant. The thirty day average for BOD removal has been met; however, sometimes without much margin. There have been a couple of months when the thirty day average for suspended solids removal has not been met.
Failure to provide the required percentage of total removal is largely a result of hydraulic overloading. During wet weather periods, the flow at the plant often exceeds more than 1 mgd. The normal dry weather flow is around 0.3 mgd. The wet weather flows are largely the result of infiltration and inflow (I/I) in the Village’s sewer system. The final clarifiers at the Village’s treatment plant are not adequate for the high flows that occur during wet weather. Efficient settling in a clarifier requires quiescent conditions. The high flows during wet weather result in increased velocities through the clarifiers, reducing the settling efficiency of the units.

Other than the problems associated with providing treatment during wet weather periods, it seems that the Village’s plant should be able to provide treatment for a substantial increase in customers. However, in order to limit the Village’s liability for a Michigan Department of Environmental Quality (MDEQ) fine, the MDEQ District Engineer was contacted to get his input. The MDEQ would not look favorably on the Village adding significant flow to its WWTP without simultaneously working to reduce the I/I Problem. Before any additional customers are connected to the Village’s sewer system, improvements should be made, or a plan developed, to ensure compliance with the MDEQ’s Permit Requirements. A detailed review has not been completed at this point, but we feel that the following components may need to be addressed. The exact nature of work required will likely be dependent upon the proposed number of new connections and the extent to which infiltration and inflow in the sewer system can be reduced.
· Final Claifiers: It seems that these are undersized for current flows encountered during wet weather. Additional clarification should improve total suspended solids removal percentage and provide permit compliance. It may be possible to enhance settling in the existing clarifiers by feeding a coagulant such as polymer during high flow periods.
- Estimated Cost Range: $250,000.00 to $350,000.00

· Grit Removal: The system does not have the capacity for the peak flows which occur resulting in large quantities of grit being passed into the treatment plant. This problem is compounded because in large quantities of grit typically increase as the wet weather flows increase. Although not directly related to the concern of meeting the permitted level of total suspended solids removal, it seems that better removal of grit facilities is a wet weather flow issue, which is the basis of the other concerns regarding treatment capacity.

- Estimated Cost Range: $40,000.00 to $60,000.00
· Chapman Street Pumpstation: If the addition of increased customers and/or infiltration-inflow conditions are such that the Chapman Street pump station’s firm pumping capacity is exceeded, the pump station will need to be upgraded accordingly.
- Estimated Cost Range: $60,000.00 to $100,000.00

· Treatment Plant: The peak hydraulic capacity of the treatment plant is about 2.6 mgd. This capacity is not based upon the ability to meet effluent permit levels, but merely the ability to pass this quantity of flow throughout the treatment plant. Peak flows must be maintained below this rate or substantial modifications will be needed at the plant.
· Operational Practices: It may be possible to experiment with the recirculation ratio to the oxidation towers. High flows to the towers can result in sloughing of the biomass from the media. This can result in a heavy solids load to the final clarifiers, which as discussed earlier, are less efficient at high flows.
· If wet weather flows cannot be reduced adequately, and alternative to making major modifications at the treatment plant might be to provide retention of excess flows. The excess would be stored temporarily until it can be passed through the plant and treated. Retention will require large areas of land, located in the area where it will not affect the public or neighboring property owners.
ALTERNATIVE APPROACH TO TREATMENT
The Village of Chesaning has also requested a study for the Village utilization of the Peet Packing Co. Sewage Ponds for Wastewater equalization. This report was completed on July 18, 1997 by Rowe Incorporated and is included in this document for a complete up to date analysis of the problems and potential solutions for treating wastewater in Chesaning.

The purpose of this study is to assess the basic technical parameters related to this idea. Issues concerning environmental, geographical, and hydrological feasibility need to be reviewed prior to purchasing the pond property. The environmental aspects include issues such as: pond leakage, existing pond sludge contamination and existing groundwater contamination. The geographical concerns will involve: the proposed sanitary forcemain routing from the Chapman street pump station, a flow diversion system, the necessary Shiawassee River crossing, easement identification, researching the existing pipe system, and related cost estimates for the proposed infrastructure improvements. Hydrological issues to be considered are: potential equalization capacity of the ponds, pipe sizing to carry the necessary flows, Chapman street pump station pumping capacity, the amount of I/I flow in the entire system that has to be diverted to the ponds, and the need for treatment of the ponds.
METHOD
Environmental

The Michigan Department of Environmental Quality (MDEQ) has jurisdiction over the sanitary system, and should give their approval for the concept of using the ponds for flow equalization. A meeting with the MDEQ was held on May 15, 1997 to discuss their concerns. Representing the district MDEQ were Mr. Terry Walkington, Dave Walters and Ken Hosack. It was discussed that there are two basic options for the Village utilization of the Peet ponds. The first option is to use the ponds for equalization, sending the water stored in the pond to the wastewater facility for treatment after the I/I system flows diminish. The second option is to use the ponds for storage and treatment of the excess flows. The stabilized effluent would be discharged directly to the river probably twice a year, (in the spring and also in the fall).

It appears that the first option is the most feasible for a couple of reasons. The Village’s existing system has I/I flows with the potential to exceed the WWTP’s permit limits almost yearly. The amount of flow necessary to be equalized for one 25-year rain event will occupy most of the available capacity of the ponds. If the ponds are full, then another relatively small rain event may exceed the capacity of the ponds. If the pond can only be emptied in the spring and fall (as in option two), then there is a good chance that the pond volumes may not be adequate. Although the required limits for a direct discharge from the ponds to the river have not been established, it appears that the content of phosphorus in the discharge will be limited and require additional treatment beyond that which can be provided by a stabilization pond. It appears to be more practical to process the water through the wastewater treatment plant for phosphorus treatment. Based on these two reasons, it is evident that the first option will fit the Village’s situation better.
Either option will require that the existing ponds be leak-proof (clay seal), have monitoring wells, be enclosed with a fence, and reasonably be brought up to the latest standards.
Other MDEQ issues brought up at the meeting were:
 A minimum water depth should be maintained in the ponds to prevent odor and clay seal cracking.

 The Township should be included in the wastewater system.
 If the Village wants to use the ponds for some treatment and direct outlet into the river, then phosphorus removal may be necessary.
 Groundwater testing near the ponds should be performed.
 The existing pond sludge should be tested for contaminates.
 An 800' isolation distance is required from the ponds to the nearest residence.
As mentioned earlier, if the ponds are to be utilized on a continuous basis, the existing clay liner must be intact. The clay liners’ integrity was tested two ways: a leakage test and a groundwater test. Leakage was checked by measuring the water surface elevation of the ponds daily for eight days while measuring water elevation in a control basin placed in the ground between the ponds. The measurements are shown in Exhibit B, Leakage Test. The recordings indicate that the ponds’ surface elevations went up and down with rain and dry periods in proportion to the control basin. This suggests that the clay liners are intact. Another way to test for pond leakage is to analyze the groundwater adjacent to the ponds. An existing monitoring well at the northeast corner of pond 2 (the north pond) was sampled for the presence of metals and organics that typically would be found in sewage sludge. The groundwater monitoring test results were not available at the time of this report, but will be provided when they are available.
Another environmental concern of the ponds is the existing sludge. The sludge in the bottom of the ponds consists of organic solids and inorganic solids. Three to four sludge samples were extracted from random locations in each pond. The sample taken from the south pond (Pond #1) contained 4.5% solids, of which 30% were organic compounds. The north pond (Pond #2) sample contained 5.1% solids, of which 24% were organic. The depth of sludge was measured to determine the remaining volume capacity of the ponds. The sludge depth was approximately 2' deep in pond 1 (south pond) and 1 1/2' deep in pond 2 (north pond). The original design water maximum depth in the ponds is five feet, with a minimum depth of two feet. Since the existing sludge depth is at or near the proposed minimum water depth, the sludge may have to be removed in the not too distant future to maintain the maximum pond capacity.

The sludge was tested for petroleum based contaminants, PCB’s and metals. The results can be found in attachment 1 and Exhibit E. The tests indicate the sludge is acceptable for land application as a method of final disposal.

Geographical

The Peet Packing Company records were researched for location of the existing pipe routes, pond construction plans, etc. Tax parcel maps and USGS topographical maps were also obtained and utilized to determine possible routes and elevations.

The ponds are located about 1,000 feet north of the village limits and 1,000 feet west of Sharon Road. The wastewater treatment plant is east of the Shiawassee River approximately 1,000 feet southeast of the Peet Packing facility (see Exhibit A and C). To utilize the ponds for equalization, the flows to be temporarily stored would have to be diverted to the ponds with a diversion structure placed after the Chapman Street pump station and before the WWTP. A new forcemain would be necessary across the Shiawassee River in the vicinity of the WWTP. The forcemain would transport the equalization flows to the ponds from the diversion control structure. Approximately 7,500 linear feet of forcemain will be needed for this purpose. One easement for the forcemain would be necessary on tax parcel #1308 (from Saginaw County Equalization Parcel Map) between the river and Sharon Road (see Exhibit C).
Hydrological/Hydraulic

The hydrologic issues include: pond capacity for equalization, a brief analysis of the existing system, and an estimate of the amount of flow that would need to be pumped to the ponds. The third issue mentioned above is difficult to determine without making some broad assumptions. It was assumed that last year’s (1996) WWTP flow records and rainfall data were somewhat typical for the village. This data was utilized to estimate the amount of I/I flow that would have to be temporarily stored (equalized) in the ponds. The flow estimate was developed by graphing the flow at the WWTP against the related rainfall amount. According to MDEQ standards, the Village’s system should be able to handle a 25 year storm event without any basements flooding or direct overflows to the river. The graph data was extrapolated to the rainfall amount for the design storm event of 25 years, (3.75" of rain over 24 hours for the Chesaning area). The graph extrapolation implied that 4.6 million gallons per day (MGD) would be generated in the sewer system after a 25 year storm event. The WWTP should be able to effectively treat 1.0 MGD. So that means that 3.6 MGD needs to be stored temporarily at the ponds.

Note that rainfall/flow data available was limited. No recorded rainfall event was anywhere near the magnitude of the 25 year storm so the flow extrapolated for the 25 year storm event is subject to a wide range of statistical error. However, the conclusions drawn regarding capacity of the ponds, pump station and pipeline seem reasonable for any flows that are likely to occur.
Certain upgrades to the existing system would be necessary to pump and transport 3.6 MGD to the ponds. The Chapman Street pump station is not capable of pumping that much flow, so the pumps would need to be replaced with larger capacity pumps. Likewise, the existing 10" forcemain from the Chapman Street pump station to the WWTP would need to be replaced with a 16" forcemain. The estimated costs for the upgrades as well as the necessary new improvements can be seen in Exhibit D.
The capacity of the Peet ponds was determined based on input from the MDEQ, original construction plans, and the existing sludge depth. It was assumed that a minimum two feet water depth would be maintained at all times in the ponds and that the maximum depth would be five feet, (this is the same situation as the original pond design). This assumption will leave a three feet freeboard or safety factor from the maximum water level to the top of the dike. With these parameters, the total storage capacity in both ponds is approximately 13 million gallons.
It was described above that the I/I from the 25 year storm event will occupy most of the ponds’ available 13 million gallon capacity. This was determined by the sewer system’s reaction to rainfall. The available data denoted that after a significant rain, the sewer system would take approximately seven days to settle back to its base flow. In that time period, approximately 13 million gallons of flow will have gone to the storage ponds for a 25 year storm. So most of the capacity of the ponds is used up by this type of storm. Once the storm has subsided, and the WWTP can handle it, the stored effluent from the ponds can be pumped back to the WWTP at a reasonable rate for proper treatment before entering the Shiawassee River. A new pump station will be needed at the ponds to facilitate this.
SUMMARY

The items and improvements listed above represent a “worst-case” scenario, based on assumptions and interpretation of limited area. If the Village opts to go forward with this approach to the I/I problem, a much more detailed analysis of the existing system is necessary. Actual wet weather and dry weather flow testing should be performed on the sewers to more precisely determine the flow that needs to be diverted to the ponds. This will also help to better define the size and costs of any proposed improvements to the system.
Based on the overall “worst-case” costs outlined in Exhibit D and the fact that the village has 938 sewer customers, the average cost per customer would be $1,014. This cost could be spread over a reasonable time period to make the improvements more palatable.
A suggested option for the Village that appears to be relatively low risk is to purchase the pond property and then continue with a more detailed study. It appears that the Village has an I/I problem and if it is indeed of the magnitude suggested here, equalization of flows in the existing ponds at the Peet facility will almost certainly be the most cost effective way to mitigate the problem. Even if the Village decides to make no improvements immediately, the ponds will still be available in the event that future regulations and demands require their use.
Successfully controlling the current I/I problem could greatly increase the overall capacity of the existing WWTP, thereby expanding the sewer system’s ultimate service area. Over the past few years, there has been interest from the property owners at the fringes of the current service area to utilize the conveniences of the Village’s WWTP.