2011 WASTEWATER FEASIBILITY STUDY.pdf

WASTEWATER FEASIBILITY STUDY

FOR THE

TOWN OF LYONS

REVISED AUGUST 1, 2011

JUNE 13, 2011

WASTEWATER FEASIBILITY STUDY

FOR THE

TOWN OF LYONS

JVA, Inc.

1319 Spruce Street Boulder, CO 80302 phone: 303-444-1951 fax: 303-444-1957

JVA Project No. 1791c

REVISED AUGUST 1, 2011

JUNE 13, 2011

TABLE OF CONTENTS

SECTION 1 – EXECUTIVE SUMMARY

BACKGROUND

PROPOSED PROJECT

SECTION 2 – PLANNING CONDITIONS

PLANNING AREA

208 PLAN COORDINATION

GROWTH AREAS AND POPULATION TRENDS

PLANNING PERIOD

CURRENT WASTEWATER FLOWS

CURRENT WASTELOADS

WASTEWATER FLOW FORECASTS

WASTELOAD FORECASTS

SECTION 3 – EXISTING FACILITIES

SERVICE AREA FEATURES

AREA DISCHARGE PERMITS

EXISTING COLLECTION SYSTEM LAYOUT AND OVERVIEW

EXISTING WWTF LAYOUT AND OVERVIEW

RECEIVING STREAM WATER QUALITY

FINANCIAL STATUS AND USERS

SECTION 4 – PROJECT PURPOSE AND NEED

COMPLIANCE

SECURITY

OPERATION AND MAINTENANCE (O&M)

GROWTH

SECTION 5 – ALTERNATIVES ASSESSMENT

INTRODUCTION

ALTERNATIVE 1 – UPGRADE EXISTING WWTF

ALTERNATIVE 2 – NEW WWTF

ALTERNATIVE 3 – CONSOLIDATE WITH CITY OF LONGMONT

COST COMPARISONS

SITE ALTERNATIVES MATRIX

SECTION 6 – SELECTED ALTERNATIVE

JUSTIFICATION OF SELECTED ALTERNATIVE

TECHNICAL DESCRIPTION

COSTS

Town of Lyons Wastewater Feasibility Study i

LIST OF TABLES

TABLE 1 – TOWN OF LYONS ZONING CLASSIFICATIONS

TABLE 2 – TOWN OF LYONS POPULATION GROWTH

TABLE 3 – TOWN OF LYONS LIFT STATIONS

TABLE 4 – SUMMARY OF EXISTING UNIT PROCESSES

TABLE 5 – LYONS WWTF DISCHARGE PERMIT LIMITS

TABLE 6 – DESIGN CRITERIA FOR UPGRADED WWTF

TABLE 7 – COST SUMMARY OF UPGRADING EXISTING WWTF

TABLE 8 – DESIGN CRITERIA FOR NEW WWTF

TABLE 9 – COST SUMMARY OF ALTERNATE SITE 2

TABLE 10 – DESIGN CRITERIA FOR GRAVITY SEWER TO LONGMONT

TABLE 11 – COST SUMMARY OF CONSOLIDATION

TABLE 12 – SITE ALTERNATIVES COST SUMMARY TABLE

TABLE 13 – SITE ALTERNATIVES ANALYSIS MATRIX

LIST OF FIGURES

FIGURE 1 – EXISTING PROCESS SCHEMATIC

FIGURE 2 – ALTERNATE WWTF SITES

FIGURE 3 – EXISTING WWTF SITE PLAN

FIGURE 4 – ALTERNATE WWTF SITE PLAN

Town of Lyons ii

APPENDICES

APPENDIX A – COMPLETED PER CHECKLIST

APPENDIX B – TOWN LAND USE MAP

APPENDIX C – CALCULATIONS

APPENDIX D – ENVIRONMENTAL MAPS

APPENDIX E – DISCHARGE PERMIT

APPENDIX F – 2010 BUDGET

APPENDIX G – LIVING MACHINE INFORMATION

APPENDIX H – SBR INFORMATION

APPENDIX I – LONGMONT CONSOLIDATION INFORMATION

APPENDIX J – OPINION OF PROBABLE COSTS

APPENDIX K – LAND ACQUISITION COSTS

iii

SECTION 1 – EXECUTIVE SUMMARY

BACKGROUND

The Town of Lyons (Lyons) is located approximately 15 miles north of the City of Boulder, Colorado, along US Highway 36 and the St. Vrain Creek. Lyons currently owns and operates a wastewater treatment facility (WWTF) to serve the Town and future commercial development to the east of Town. The Town’s WWTF is located on 2nd Avenue along the St. Vrain Creek jogging path and Kayak Park. The WWTF was constructed in 1976 and has been upgraded several times. The facility is reaching its useful life, and as residential development has surrounded the WWTF, the Town has received noise and odor complaints. Due to these complaints and the close proximity of land intended for recreational uses, there are pressures to move the WWTF away from the center of Town and allow for process upgrades.

Recently, the Town was awarded a State Revolving Fund (SRF) Planning and Development Grant by the Colorado Department of Public Health and Environment (CDPHE) to evaluate options for wastewater service to the Town. The following report presents a discussion of the options for wastewater service to meet the documentation requirements of the CDPHE Preliminary Engineering Report (PER). The CDPHE Wastewater PER Review Checklist has been completed and is provided in Appendix A.

PROPOSED PROJECT

To be completed after presentation to Board

Town of Lyons

SECTION 2 – PLANNING CONDITIONS

PLANNING AREA

The Town of Lyon’s planning boundary is currently described as the wastewater utility service area (WUSA), which is attached in Appendix B. According to the 2010 Census, the Town of Lyons has 861 occupied residential units. Town billing records reflect a current commercial sewer tap count of 82 units. Lyons updated its Comprehensive Plan in 2010 to reflect the loss of several parcels of land within its planning area. The modified planning area is shown on the Town’s current Land Use Map attached in Appendix B and is the basis for the population projections used in this study.

208 PLAN COORDINATION

Lyon’s 208 Management Agency was the Denver Regional Council of Governments (DRCOG) until mid 2010 when the utility plan review component of DRCOG was dissolved. At that time, all planning and utility related issues came under the umbrella of the CDPHE water quality control division (WQCD). Therefore, the WWTF is no longer within a 208 Planning Agency or Council of Governments planning area. Any project associated with the WWTF that the Town undertakes shall be reviewed by and coordinated with Boulder County and the WQCD. There are no other planning requirements for this project.

GROWTH AREAS AND POPULATION TRENDS

The 2000 Census indicated a Town of Lyons population of 1,585. The 2010 Census measured the Town population at approximately 2,033 people and 861 occupied housing units within Town limits. The annual growth rate of Lyons is approximately 2.8 percent per year, a value that is generally considered moderate growth. Using the 2010 Census data, the population density was determined to be approximately 2.36 people per household.

ZONING

The Town Municipal Code identifies the zoning districts shown in Table 1. The current Town Land Use Map for areas outside of Town limits but within the approved planning area is attached in Appendix B.

Table 1 – Town of Lyons Zoning Classifications Zoning District Abbreviation

Zoning District

A-1 Agricultural District A-2 Agricultural District

Town of Lyons

Zoning District Abbreviation

Zoning District

E Estate Residential District EC Estate Country Residential District R-1 Low Density Residential District R-2 Medium Density Residential District

R-2A Medium-High Density Residential District R-3 High Density Residential District B Business District C Commercial District

CD Commercial Downtown District CE-1 Commercial Entertainment District CEC Commercial East Corridor District

LI Light Industrial District GI General Industrial District M Municipal Facilities and Services

POS Parks and Open Space District PUD Planned Unit Development District ROA Restricted Outdoor Activity Overlay District LOA Limited Outdoor Activity Overlay District OOA Open Outdoor Activity Overlay District

The Town recently investigated how close it is to complete build-out of both residential and commercial development. Lyons has established that it has 80 additional developable lots within its planning area. According to the Lyons Planning Map included in Appendix B, the projected commercial growth will only occur in the area west of Highland Drive and north of County Road

39. This amounts to approximately 390 acres, of which only 50 percent is considered developable. Thus, the total developed commercial area will be approximately 195 acres.

PLANNING PERIOD

The planning period for preliminary engineering reports is generally 20 years. Using the proposed 2.8 percent growth rate, the Town will achieve build-out by 2018. Refer to the population summary in Table 2. Despite build-out occurring before the 20-year planning period, the WWTF has a treatment life cycle of 20 years. The Town can request funding through the State Revolving Fund (SRF), which require a 30-year loan term and a 20-year planning cycle, or United States Department of Agriculture (USDA) Rural Development funding, which requires a 40-year loan term and a 20-year planning cycle.

Table 2 – Town of Lyons Population Growth Year Population

2010 2,033 2011 2,090 2012 2,148

Town of Lyons

Year Population

2013 2,209 2014 2,270 2015 2,334 2016 2,399 2017 2,466 2018 2,535

CURRENT WASTEWATER FLOWS

The Town’s WWTF operates under the Colorado Discharge Permit System (CDPS), permit number CO-0020877. The WWTF has a permitted hydraulic capacity of 381,000 gallons per day (gpd) and a permitted organic capacity of 705 pounds of BOD5 per day, which translates to an influent BOD5 concentration of 322 mg/L at peak flow. Hydraulic capacity is related to the maximum flow rate which can go through the plant in one day while receiving adequate treatment. Organic capacity is related to the strength of the influent wastewater and the quantity of influent wastewater. If wastewater strength increases yet the influent flow remains the same, the WWTF will approach its organic capacity before reaching its hydraulic capacity.

Flow data at the WWTF is collected using a Parshall flume with electronic ultrasonic sensor and data logger. Using available data from January 1, 2009 through December 31, 2010, as provided by the Town’s operator, the current average daily flow at the WWTF is approximately 151,000 gallons per day (gpd) or about 39 percent of the permitted hydraulic capacity.

To calculate an accurate per capita wastewater flow estimate, winter wastewater data is used to reflect the absence of infiltration and inflow (I&I). The Town’s operating data recorded that dry weather flows are from September through April. The historic flow at the WWTF during these months was 134,000 gpd. Using the Town’s 2010 population of 2,033, the calculated per capita winter wastewater flow is 66 gallons per capita per day (gpcd). This per capita flow rate is slightly lower than the CDPHE’s recommended design range of wastewater flows, which ranges between 70 and 100 gpcd. Refer to detailed calculations in Appendix C.

VERIFICATION OF WASTEWATER PRODUCTION

According to metered water usage for the winter months (January through April 2010 and October through December 2010), the average residential winter monthly usage is 3.548 million gallons. There was an average of 748 residential taps (ranging from 732 taps in February to 770 taps in October), thus the average monthly residential usage was 4,741 gallons per tap or EQR (equivalent residential unit). Over the same time period, the average winter non-residential monthly usage was 1.775 million gallons. Based on the average monthly residential usages of 4,741 gallons (1 EQR), the non-residential customers (including multi-family and commercial) use an amount of water equivalent to 374 EQRs (1.775 MG / 4,741 gallons per EQR).

With a total of 748 residential EQRs and 374 non-residential EQRs, the total number of EQRs is 1,123. The total monthly winter usage is 5.322 million gallons; thus, the average daily usage is

0.177 MGD. By assuming each EQR has a population density equivalent to the Town (2.36

Town of Lyons people per household), the equivalent population served by the water system is 2,649 people.

Given the population of the water service area and population density, the per capita water consumption is 67 gpcd. With ten percent consumptive use (typical percentage of water not returned as wastewater flow), the per capita wastewater production rate is 60 gpcd.

The wastewater production rate estimated from metered water data (60 gpcd) is slightly lower than the calculated wastewater production rate (66 gpcd). This can be explained by a lower population density within the water service area compared to the Town, a lower percentage consumptive use, or inconsistencies between metered water data and WWTF flow records.

Despite the nine percent difference between the wastewater production rates calculated from influent wastewater data and water usage data, 70 gpcd will be used to project future flows for the Town throughout this study to ensure that future processes are adequately sized and that they meet CDPHE Design Criteria.

INFILTRATION AND INFLOW

Town staff has indicated that roughly half of the collection system consists of older vitrified clay pipe (VCP), a material that is subject to cracking, root intrusions, and degradation at a higher rate than the newer polyvinyl chloride (PVC) pipe of the other half of the collection system. The calculated peaking factor (the ratio of maximum daily flow to average daily flow) for this system is 2.33, a value that is considered relatively low and indicative of low infiltration and inflow (I&I). The majority of the I&I is likely from the older half of the collection system since all of the newer subdivisions used PVC.

CURRENT WASTELOADS

The Lyons WWTF currently monitors influent and effluent 5-day biochemical oxygen demand (BOD5) concentrations and total suspended solids (TSS) concentrations, effluent copper concentrations, effluent ammonias on a quarterly basis. The Town also monitors effluent temperature on a daily basis.

A review of DMR data indicated that the average and 90th percentile influent BOD5 concentrations are 324 mg/L and 422 mg/L, respectively. In reviewing the data, several influent BOD5 data points were identified that were significantly higher from the rest of the data set and were considered outliers. These data points were excluded from the calculations, as they presented high enough BOD5 concentrations to skew the average approximately 10 percent higher.

The Town’s discharge permit specifies that the WWTF is permitted to treat 705 pounds per day of BOD5. Using the design flow of 0.381 million gallons per day (MGD), the influent BOD5 concentration used in the original design of this facility is 222 mg/L, a value that is significantly less than current influent BOD5 measurements. The higher calculated BOD5 value for Lyons can be attributed to the fact that the Town has emphasized the need for sustainability in their infrastructure. Newer appliances, toilets, and faucets use less water than their predecessors use, thus creating a more concentrated waste stream. Moreover, the Town has a significant number of restaurants within its utility service area. If these grease traps are not maintained regularly, Town of Lyons they can introduce fats, oils, and grease (FOG), which contribute a very high oxygen demand, into the collection system.

To determine the current organic loading to the WWTF, the 90th percentile BOD5 concentration and the average influent flow are typically used. Based on discussion with Town staff and the operations staff, the average BOD5 concentration shall be used to determine current and future organic loading to the WWTF. Although the average organic concentration value may reflect lower peak organic loading rates than if the 90th percentile is used, the Town has committed to a more thorough review of commercial and industrial contributors’ loading and grease trap inspections and anticipate a reduction in influent BOD5. It is strongly recommended that influent BOD5 characteristics be reevaluated once corrective measures within the Town are implemented and prior to proceeding with design of any expansion to this system. The organic loading to the WWTF under current conditions, using the current average BOD5 concentration of 324 mg/L is approximately 407 lbs/d, or roughly 57.8 percent of its permitted organic capacity.

CDPHE requires that facilities begin planning when their 30-day average daily flows exceed 80 percent of the hydraulic or organic design capacity. For the Town, the planning trigger of the existing permit is at 304,800 gpd or 564 pounds of BOD5 per day. Facilities are required to start construction when the average daily flow reaches 95 percent of the design capacity. Although the Town is not approaching its hydraulic capacity, the WWTF has exceeded the 80 percent planning trigger for its organic capacity, according to quarterly BOD5 sampling.

WASTEWATER FLOW FORECASTS

RESIDENTIAL

The Town has confirmed that there is a maximum of 80 additional residential lots in the planning area which would introduce approximately 189 new residents assuming 2.36 people per household. The resulting total population of the Town is estimated to be 2,222. For this study, the maximum calculated population of 2,222 will be used to determine residential flows. At 70 gpcd, the projected residential wastewater production would be approximately 155,500 gpd.

COMMERCIAL

There are approximately 390 acres slated for commercial or light industrial development within the 20-year planning period. The Town has concurred that a maximum of 50 percent of this area is considered developable. Metcalf & Eddy’s Wastewater Treatment presents an industry standard water demand for light industry of 1,000 gpd per acre. With 15 percent consumptive use, the projected wastewater flows from these commercial areas are approximately 165,750 gpd. Consumptive use is that portion of water that is consumed and thus is not discharged to the sewer as wastewater flow.

TOTAL FLOWS

The total projected build-out flow is approximately 321,250 gpd. These projections incorporate a significant amount of uncertainty with respect to development density and industrial

Town of Lyons contribution. With the current capacity of 381,000 gpd, the plant will have a 19 percent buffer in flows.

WASTELOAD FORECASTS

In order to project future organic loading that must be treated by the WWTF, it was assumed that the current average influent organic concentration of 324 mg/L remains constant over the planning period. With a projected population of 2,222 people and flow rate of 70 gpcd, the anticipated additional residential organic load to the WWTF by 2031 will be about 420 pounds of BOD5 per day. The organic load anticipated from all non-residential sources (institutional, commercial/industrial) is an additional 450 pounds of BOD5 per day. The total 20-year projected load is 1,030 pounds per day (including a 20 percent buffer), which is greater than the current permitted organic capacity of 705 pounds of BOD5 per day.

SECTION 3 – EXISTING FACILITIES

SERVICE AREA FEATURES

The topography of the Lyons service area is generally mountain foothills with sloped areas transitioning to generally flat terrain and with soil comprised of Colluvial land, Niwot soils, and Pinata-Rock outcrop complex with slopes ranging from 5 to 55 percent. The Town is located along Ute Highway (Colorado Highway 66).

FLOODPLAINS

The Federal Emergency Management Agency’s (FEMA’s) floodplain mapping locates the Town’s WWTF in the floodway of the St. Vrain Creek floodplain. Flood maps are attached in Appendix D. According to available information, the floodplain elevation is 5,314.4 feet. It is anticipated that site specific survey efforts and modeling will need to be completed in order to verify flood data if modification to the existing site is implemented.

The original WWTF plans illustrate that the emergency storage pond berm has an elevation of 5,317 feet above sea level. The existing aeration tank, clarifier, and control building have tank wall and finished floor elevations above 5,317 feet. Although the headworks and influent pump station are located below grade at an elevation of 5,295, the elevation of the entrance to the headworks is suitably sited at 5,317, which above the 100-year flood elevation. The existing gravity effluent pipeline at the point where it enters the river has an invert of approximately 5,308 feet. During a 100-year flood event the discharge from the WWTF will back up into the effluent pipe to the point where the elevation in the pipe is approximately 5,314. Since the UV disinfection discharge pipe has an invert elevation set at 5,314.4, the same elevation as the 100-year flood elevation, it is unlikely that discharge by gravity to the river during a 100-year flood event will be possible. It is strongly recommended that the Town complete a survey inventory of critical points in the WWTF hydraulic profile to ensure elevations shown on as-built drawings are correct, and that the 100-year flood elevation datum is consistent with survey information.

The Town has established that if the WWTF undergoes major modifications, all facilities will require floodproofing, floodplain mitigation, and both a conditional letter of map revision (CLOMR) and letter of map revision (LOMR).

WETLANDS

According to the National Wetlands Inventory Map attached in Appendix D, the WWTF’s location along the St. Vrain Creek is near Riverine wetlands. The emergency storage ponds are identified as artificially flooded, Palustrine wetlands although the ponds are not currently in use.

If it appears that any upgrades to the existing WWTF would affect wetlands, a full wetlands delineation will need to be completed to determine if an Army Corps of Engineers (ACOE) 404

Town of Lyons

Permit is required. If the outfall needs to be modified, it will cross Riverine wetlands, but it will be covered under an ACOE Nationwide Permit.

AREA DISCHARGE PERMITS

There are three industrial dischargers within a 5-mile radius of the Town’s WWTF, but all are quarry operations which would not be able to treat domestic wastewater. There are no municipal dischargers within a 5-mile radius. The City of Longmont is located approximately 10 miles east of the WWTF and has sufficient capacity to accommodate flows from Lyons. Consolidation will be considered in the Alternatives Analysis section.

EXISTING COLLECTION SYSTEM LAYOUT AND OVERVIEW

The existing collection system generally consists of 8-inch to 12-inch VCP and flows northwest to southeast. Town staff authorized the inspection of the downtown area known as “Old Town” was video-inspected in the past five years. Recently developed areas were constructed with primarily PVC pipe.

There are four lift stations within the collection system: the Lyons Valley Park Lift Station, the Stone Canyon Lift Station, the Riverbend Lift Station, and the Eagle Canyon Lift Station. The Riverbend Lift Station is privately owned and operated, thus not part of the Town’s maintenance program, and is not considered further in this master plan. The Lyons Valley Park and Stone Canyon Lift Stations are both Gorman Rupp lift stations. A summary of lift station information is presented in Table 3.

Table 3 – Town of Lyons Lift Stations Lift Station Manufacturer Quantity Capacity

Eagle Canyon Gorman Rupp 2 20 gpm each Stone Canyon Gorman Rupp 2 80 gpm each Riverbend Privately owned 2 2 gpm each Lyons Valley Park Gorman Rupp 2 230 gpm each

EXISTING WWTF LAYOUT AND OVERVIEW

To determine if the existing WWTF can be used to treat future waste flows, the capacity of the existing treatment processes need to be determined. To accomplish this task, a modified comprehensive performance evaluation (CPE) of the existing unit processes was completed. The CPE completed by JVA uses CDPHE Design Criteria Considered in the Review of Wastewater Treatment Facilities Policy 96-1 (Design Criteria) as the design standards to be met. The EPA Handbook for Retrofitting Publicly Owned Treatment Works (EPA/625/6-89/020) and Wastewater Engineering Treatment, Disposal, and Reuse by Metcalf and Eddy, Inc. 5th Edition, also provided supplementary information for evaluation of process units.

The existing discharge permit limits were used to define effluent standards that must be met by this facility under the current loading conditions, with a look to future growth and permit limits, including nutrient removal. Recommendations presented in this report are based on operating

Town of Lyons information, performance results, facility information, and other information provided by the operations staff and management.

PROCESS SUMMARY

The Lyons WWTF is considered to be a conventional activated sludge treatment facility.

Influent flows first through an automatic bar screen and is then discharged into an open channel which flows into a Parshall flume where influent flow is measured ultrasonically. After flow measurement, wastewater flows through a comminutor and into a wet well where it is pumped to the circular aeration basin. From the aeration basins, wastewater flows into the clarifier where solids settle out and treated effluent overflows perimeter weirs. Clarified effluent flows by gravity to UV disinfection, after which it is discharged to the St. Vrain Creek. Waste activated sludge (WAS) from the bottom of the clarifier is pumped to the aerobic digesters, and return activated sludge (RAS) is sent back to the aeration basin. The aerobic digesters are decanted periodically, and decant water is sent back to the headworks wet well. The digested sludge is thickened with coagulant and run through a rotary drum thickener. Sludge is dewatered on the drying beds and hauled offsite for ultimate disposal at a landfill. An overview of the existing treatment processes is shown in Figure 1.

HEADWORKS EQUIPMENT

The headworks of a WWTF serves to remove any large material from wastewater by physical removal or by grinding to reduce the particle size. Bar screens and screw screens physically remove any detritus, whereas comminutors and grinders reduce particle size. The problem with simply reducing particle size is that often rags and other material can reconstitute in processes downstream.

The Town’s collection system enters the WWTF through an open channel at the head of the plant. Influent screening is the first process, followed by grinding with a comminutor. The influent screen is a PRO-Equipment PRO-GUARD automatic screw screen. The screen has 1/4-inch openings and a maximum hydraulic capacity of 1.0 MGD. A 1/4-inch manual bar screen is in parallel with the screw screen for bypass purposes.

After the screw screen, water from the rotary drum thickener and condensation from the clarifier dome is introduced into the influent channel. Flow measurement is accomplished with a 3-inch Parshall flume and ultrasonic level sensors after both waste flows are introduced. Operations staff mentioned that both the influent channel and Parshall flume accumulate a substantial amount of grit and require cleaning every two weeks.

The comminutor is located downstream from the Parshall flume and serves to grind up any material that the screw screen missed. The comminutor at the plant was installed in 1976 with original plant construction.

CAPACITY LIMITATIONS The screening equipment at this facility has a maximum hydraulic capacity of 1.0 MGD. Since this equipment services the headworks of the facility, the CDPHE design criteria stipulate it must be designed for peak hour flow. Peak hour flow is defined as the peak flow rate sustained during a 24-hour period on an annual basis. With limited data available, it is not possible to determine the actual peak hour flow at this facility. Using industry standard references, a community this size would likely experience a peak hour peaking factor of 4. The capacity of the screening equipment, as it related to hydraulic flow, is therefore only 250,000 gpd.

The Parshall flume has a recordable flow range between 0.0005 MGD and 3.5 MGD, although the more accurate flow range is between 0.0532 MGD and 1.837 MGD. The flume is not subject to the CDPHE peak hour peaking factor criteria, thus the capacity of the flume is 1.837 MGD.

INFLUENT PUMP STATION

After flowing through the headworks, wastewater enters the 1,000-gallon influent wet well. The two 20 horsepower (HP) influent centrifugal pumps are located in a dry pit next to the wet well.

Each pump has a capacity of 900 gpm at 30 feet of total dynamic head (TDH). The centrifugal pumps are operated on variable frequency drives (VFDs) primarily to adjust pump speed/flow rate to the aeration basins, but a secondary benefit is saving operating electrical costs.

CAPACITY LIMITATIONS The pumps’ design points restrict the capacity of the influent lift station to a peak hourly flow of 1.296 MGD. With an hourly peaking factor of 4, the influent lift station would be capable of operating at a maximum average daily flow of 0.324 MGD.

ACTIVATED SLUDGE AERATION BASIN

The WWTF for the Town was designed as a conventional activated sludge system. This designation is used in the analysis below to determine the current and projected capacity of the

WWTF.

The original WWTF was designed for an average daily flow of 0.286 MGD. The aeration system in the basin was updated with Tideflex fine-bubble diffusers in 2000, which increased the system capacity to its current capacity of 0.381 MGD. The Tideflex diffused aeration system was installed in a grid over five zones of the aeration tank. The increase in oxygen capability in the aeration basin allowed for an expanded hydraulic treatment capacity to 0.381 MGD. The original WWTF was designed to treat an influent BOD5 concentration of 240 mg/L (575 pounds of BOD5 per day at 0.286 MGD). The upgraded WWTF was designed to treat an influent BOD5 concentration of 222 mg/L (705 pounds of BOD5 per day at 0.381 MGD).

The activated sludge aeration basin is doughnut-shaped, with the outer ring consisting of the aeration basins and the inner circle as a clarifier. The outer diameter of the aeration basin is

60.66 feet and the inner diameter (clarifier diameter) is 35 feet. The operating depth of the aeration basin is 14 feet, which is fairly shallow according to Design Criteria. Since depth is directly related to oxygen transfer efficiency, deeper basins have higher oxygen transfer efficiency. The aeration basin has an operating volume of approximately 200,000 gallons (27,000 cubic feet). The existing aeration basin has no redundancy and has presented routine

Town of Lyons operational problems since it has limited freeboard. Operations staff has had to improvise freeboard by connecting railroad ties to the concrete tank to limit the overflow of foam during operational upsets.

The Town lacks redundant aeration basins due to the existing 2.44 MG emergency storage pond.

At the design flow of 0.381, this pond would have the capacity to store approximately 6 days of flow. While this retention time allows operations staff a significant amount of time to correct a process upset in the aeration basin, it is unknown whether the pond is lined or not. If the pond is unlined, wastewater can seep into groundwater and cause contamination, which constitutes an unauthorized discharge to groundwater and violation of

HYDRAULIC RETENTION TIME The hydraulic retention time is the amount of time it takes for water to pass through the basin. This is determined by dividing the tank’s volume by the influent flow rate. CDHPE Design Criteria stipulates that conventional activated sludge facilities have a minimum hydraulic residence time between 4 and 8 hours. At current flows, the existing aeration basin has a hydraulic residence time of 32 hours (1.33 days)

The aeration basin has an average mixed liquor suspended solids (MLSS) concentration of 5,000 mg/L, as measured by operations staff. MLSS concentrations are a measure of the suspended solids in the aeration basin. Volatile suspended solids (VSS) generally refer to the biologically active component of the MLSS concentration. In comparing the current hydraulic residence time and MLSS concentrations to CDPHE Design Criteria, the aeration basin is operating more as an extended air-activated sludge system than as a conventional activated sludge facility (conventional activated sludge facilities have hydraulic residence times of four to eight hours and MLSS concentrations between 1,500 and 4,000 mg/L). Although there are not necessarily concerns with operating the WWTF as an extended aeration plant at this time, the current process control practices will need to change to reflect the original design of the WWTF which is a conventional activated sludge facility. The change in process control strategies to operate the existing WWTF as originally designed will include maintaining a lower MLSS concentration which results in a higher WAS flow to the digesters.

CAPACITY LIMITATIONS Without modifying the existing aeration basin system, the hydraulic capacity of the treatment process is 1.2 MGD assuming the facility is operated as a conventional activated sludge system.

Note: If the facility continues to operate as an extended air activated sludge facility in process control, the hydraulic capacity of the treatment process is 0.2 MGD.

ORGANIC LOADING RATE The organic loading rate is determined by the BOD5 loading and volume of the aeration basin. CDPHE Design Criteria stipulates that conventional activated sludge treatment facilities have a design maximum organic loading of 40 pounds of BOD5 per 1,000 cubic feet of operating aeration basin volume. Based on current influent BOD5 load of 407 pounds per day and the aeration basin volume of 27,000 cubic feet, the current organic loading is 15 pounds of BOD5 per 1,000 cubic feet. This organic loading is within CDPHE Design Criteria.

Town of Lyons

CAPACITY LIMITATIONS Without modifying the existing aeration basin sizing, the organic capacity of the treatment process is 0.400 MGD.

If the facility continues to operate as an extended air activated sludge facility, the organic capacity of the treatment process is 0.25 MGD.

CLARIFIER

The secondary clarifier serves to settle MLSS from the aerated wastewater. In the clarifier, the sludge blanket settles to the bottom, and the clarified water overflows the weirs located around the perimeter of the clarifier into a launder. The clarifier mechanism rotates around the center of the basin and scrapes scum off the top layer into the scum beach, which is then pumped to the digester. The rake arm scrapes sludge from the bottom of the clarifier and pushes sludge to the return activated sludge (RAS) and waste activated sludge (WAS) pumps.

The clarifier is located in the center of the aeration basin. As stated previously, the clarifier has a diameter of 35 feet and a depth of 14 feet. The Town’s clarifier mechanism was manufactured by Oliver Doore and installed with the original facility construction in 1976. The clarifier mechanism has not been replaced since its original installation. Operations staff noted that the clarifier mechanism had a structural failure a few years ago and was rehabilitated, but not fully replaced. Since there is a lack of redundancy, staff had a temporary process upset. Maintenance staff was able to fix the clarifier temporarily; nevertheless, the clarifier mechanism has reached its useful life.

SURFACE OVERFLOW RATE CDPHE Design Criteria requires that activated sludge secondary clarifiers have a maximum surface overflow rate of 600 gallons per square foot per day. At the current average daily flow, the Town’s surface overflow rate is 156 gallons per day per square foot, which is below CDPHE’s recommended surface overflow rate.

CAPACITY LIMITATIONS Without modifying the existing clarifier system, the capacity of the treatment process derived from surface overflow rates is 0.577 MGD.

SOLIDS LOADING RATE The solids loading rate is calculated with the influent MLSS concentration of 5,000 mg/L and the clarifier’s surface area. The clarifier currently has a solids loading rate of 6.5 pounds per square foot per day. CDPHE recommends a design range of 28 to 50 pounds per square foot per day. The clarifier is under-loaded under the current operating characteristics of this facility.

CAPACITY LIMITATIONS Without modifying the existing clarifier system, the capacity of the treatment process from the solids loading rate limits alone is 1.154 MGD.

RAS/WAS PUMPS

The WWTF has one air lift pump for returning sludge from the clarifiers back to the aeration basins (RAS pumps). The same pump is used to waste sludge from the clarifier to the digester.

The pump was installed in 1976 with the original WWTF. Air lift pumps are notorious for clogging when flows are turned down too low. Additionally, there is no accurate way to measure

Town of Lyons flows from an air lift pump. Based on discussion with the operations staff, the RAS/WAS pump work adequately, but have to be operated at higher than desirable ranges under the current loading to ensure the air lift pump does not clog.

CAPACITY LIMITATIONS The capacity of the air lift pump is not very easy to define since it depends on the solids concentration in the clarifier and the number of pumps running at one time off of a single compressor. Air lift pumps are generally difficult to use to control process operations and do not meet the lower capacity range desirable in an activated sludge system.

SCUM PUMPS

The scum collection box, located adjacent to the clarifier, collects scum from the clarifier surface. The pump in the scum box periodically sends collected scum to the digester for further treatment, removing it from the treatment process. The scum pump is also an air lift pump with unknown capacity. Since this pump operates off a level controller the capacity is relatively unimportant as long as the contents of the scum box can be emptied to the digester in sufficient time.

CAPACITY LIMITATIONS Other than operational flexibility limitations, there are no known capacity limiting factors associated with this pump.

DISINFECTION

The Lyons WWTF has two Trojan UV3000 PTP ultraviolet (UV) disinfection units which can be operated in series or in parallel. The Trojan units are low pressure, low output lamps. Each unit has 7 banks, with 2 lamps per bank. The UV dose is 2.4 milliWatt (mW) per centimeter (cm).

Each UV unit has a peak hydraulic capacity of 0.4 MGD flow. The UV units do not have automatic wiping systems, so operations staff chemically cleans the lamps’ quartz sleeves on a monthly basis.

CAPACITY LIMITATIONS Per CDPHE design criteria, disinfection units must be capable of handling the peak hour flow rate through the WWTF, unless adequate flow equalization is utilized. Assuming both UV disinfection modules are operational, the capacity of the UV disinfection system is 0.8 MGD peak hour flow, or approximately 0.4 MGD average day flow.

BIOSOLIDS HANDLING

The two-celled aerobic digester was added to the Towns WWTF system in 1996. Each digester cell is 30 feet by 30 feet by 14 feet deep. Assuming a freeboard of around 2 feet, the actual operational volume of each digester cell is 80,784 gallons, providing a total aerobic volume of 161,568 gallons.

Waste activated sludge and scum from the secondary clarifier is sent to the aerobic digester.

Wasting occurs on a daily basis in batches, whereas scum is discharged from the scum pit as needed. The digester is equipped with a grid aeration system operated in an on/off aeration control strategy, which allows the digester to denitrify and regain alkalinity during the “off”

Town of Lyons cycles. The digester can be decanted as needed to thicken the sludge in the digester. Decant flows are returned to the headworks. Stabilized sludge is dewatered using one rotary drum thickener prior to hauling for final disposal to landfill.

SLUDGE ACCOUNTABILITY Using the average WAS flows of 3,000 gpd and an assumed WAS concentration of 6,000 mg/L, the WWTF wastes approximately 150 pounds per day of sludge. The amount of solids in the effluent wastewater that is discharged to the receiving stream has a 90th percentile TSS concentration of 10 mg/L, resulting in an effluent solids loading of 12.5 pounds per day at the current average flow rate of 0.151 MGD. The total sludge that is accounted for is the WAS sludge plus the effluent sludge, or 162.5 pounds per day.

Using the available information and assuming that approximately 0.60 pounds of TSS is produced for every pound of BOD removed, the amount of sludge that would be produced in this facility is estimated to be 241pounds per day under the current flow conditions. The unaccounted for sludge is determined by subtracting the known sludge (162.5 pounds per day) wasted from the WWTF, from the anticipated sludge produced at this facility (241 pounds per day). The volume of unaccounted sludge at this facility is 78.8 lbs/d, or roughly 33 percent.

This value for unaccounted sludge is relatively high, indicating that the operations staff has somewhat reliable solids handling procedures but improvements to solids handling and accountability could be implemented.

CAPACITY LIMITATIONS The biosolids are currently hauled to a landfill once per week.

Total annual biosolids hauling costs are approximately $47,000 per year, as identified in the Town budget attached in Appendix F. The only capacity limitation associated with this process is the amount of money the Town can assign to biosolids handling. Other options, including onsite drying, will reduce Town hauling costs, but will also increase manual labor to maintain the drying beds.

DIGESTER CAPACITY According to operations staff, sludge is wasted from the clarifiers on a batch basis each day, the amount of which is determined by both process control requirements and digester capacity. The average detention time in the digesters is 53 days with the average WAS flow of 3,000 gpd. Using an average winter operating temperature of 16.8°C, the digester process is operating at 900 degree-days, meeting CDPHE criteria for Class B biosolids. The sludge accountability, as noted above, is questionable and it is likely that more sludge is actually wasted form the clarifier at different times of the year, reducing the residence temperature/time value. Without better solids handling documentation, it is unclear if the digester meets Class B digester solids at all times throughout the year.

CAPACITY LIMITATIONS Although it is possible that the digesters meet CDPHE Design Criteria for Class B biosolids throughout most of the year under the current flow conditions, as flows to the WWTF increase, biosolids production will also increase. The operating volume and hydraulic retention time of the digesters, based on limited available data, dictate the actual capacity of the digesters at 0.1 MGD, a value that is less than current flow conditions. If additional data collection on the biosolids handling system is implemented the true capacity of the digesters could be determined. Without additional data to substantiate digester capacity we are limited to concluding that the digester is undersized for current and future requirements.

Town of Lyons

ROTARY DRUM THICKENER The rotary drum thickener (RDT) is used to thicken digested sludge prior to hauling it away for final disposal. The RDT has an operational feed rate up to 60 gpm at roughly 2% solids. The RDT is currently processing 20-26 gpm of sludge in a 7 hour operational window. The cake from the RDT is roughly 8% solids.

CAPACITY LIMITATIONS Assuming the digested sludge fed to the RDT remains relatively consistent, the maximum digested sludge the RDT can process is approximately 25,200 gallons in one 7-hour operational day. The capacity of the RDT, as it relates to influent flow, is estimated to be 2.5 MGD and is therefore not a capacity limiting process at this WWTF.

SUMMARY OF TREATMENT PROCESS CAPACITY

Table 4 provides a summary of each treatment process’s capacity at the WWTF. The basis for the analysis is the CDPHE Design Criteria for each unit process and the available historical data.

For the purposes of this analysis, the average influent BOD5 is used to determine organic load conditions. If the organic load is not reduced through mitigation efforts implemented by the Town, then the actual capacity of each treatment unit, with respect to organic capacity, will be less than that shown in Table 4. The replacement priorities are also designated in Table 4. The UV disinfection process is the highest priority due to its critical nature in terms of meeting discharge permit limits. The aeration basin and clarifier basin upgrades are the second highest priority for similar reasons. Due to the clarifier’s location within the aeration basin, it is recommended that both upgrades be performed concurrently. The biosolids handling process is third priority due to the cost of hauling sludge offsite. The influent pump station and headworks are fourth and fifth on the list due to their adequacy for current conditions, but they will need to be upgraded once additional development occurs within Town limits.

Table 4 – Summary of Existing Unit Processes Priority Treatment Process Capacity, MGD

6 Headworks Bar Screen, PF=4 Parshall Flume

0.250 MGD

1.837 MGD

5 Influent Pump Station 0.324 MGD 2 Aeration Basin

Hydraulic Retention Time Organic Loading Rate

1.2 MGD

0.40 MGD

1 Clarifier

Surface Overflow Rate Solids Loading Rate

0.577 MGD

1.154 MGD

4 UV Disinfection, PF=4 0.20 MGD 3 Biosolids Handling

Digester Rotary Drum Thickener

0.10 MGD

2.5 MGD

RECEIVING STREAM WATER QUALITY

The WWTF discharges to the St. Vrain Creek (Stream Segment COSPSV02b_0800), which is listed as a Section 303(d) impaired stream. The Water Quality Control Commission (WQCC)

Town of Lyons evaluated the St. Vrain in its Section 305(b) Report published in 2010. The report specifies that the section of the St. Vrain to which the WWTF discharges is classified as a Category 5 stream;

meaning that it does not meet applicable water quality standards for one or more designates uses by one or more pollutants. The stream does not meet cold water aquatic life standards for copper and temperature. The Town’s copper sampling for the last three quarters of 2010 measured concentrations of 0.01 μg/L. Currently, the WWTF is only required to report measured copper concentrations at this time, so the status of future compliance is unknown.

The Water Quality Control Commission regulates ambient water quality standards for the St.

Vrain Creek in Regulation #38 Classifications and Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin (amended 1/10/11) (Regulation #38). According to the recent revision to Regulation #38, segment COSPSV02b now has an chronic in-stream copper limit of 6.0 μg/L. This in-stream limit is effective until December 2015 and is referred to as a “type iii” standard, which the Water Quality Control Commission defines as a temporary modification adopted pursuant to subsection 31.7(3)(a)(iii) of the Basic Standards and Methodologies for Surface Water (i.e., “where there is significant uncertainty regarding the appropriate long-term underlying standard”). The next rulemaking hearing for Regulation #38 is in June 2015, so no new in-stream standards will be implemented until then. It is recommended that the Town start sampling in-stream copper concentrations upstream of the WWTF to quantify in-stream copper concentrations. If the upstream (background) concentrations exceed 6.0 µg/L, it is likely that that the Town will not have to meet copper limits.

Historic DMR data indicates that the maximum weekly average temperature (MWAT) exceeds the anticipated discharge limit of 20 degrees Celsius from the beginning of July to the beginning of November. As reflected in the discharge permit attached in Appendix E, the Town will need to submit all temperature data and request an extension by August 31, 2011. To qualify for an exemption regarding the temperature limit, the Town will need to collect in-stream temperature data upstream of the WWTF on an hourly basis and conduct a more detailed study of the impacts of temperature on seasonal flow variations.

Table 5 – Lyons WWTF Discharge Permit Limits Parameter Limit

Effluent Flow, MGD 0.381(30-day average) pH 6.5 – 9 (daily maximum)

BOD, mg/L 30/45 (30-day average/7-day average)

BOD5 85 (30-day average) , % removal

Total Suspended Solids, mg/L 30/45 (30-day average/7-day average)

TSS, % removal 85 (30-day average)

Oil and Grease, mg/L 10 (maximum)

Total Residual Chlorine (TRC), mg/L 0.09/0.035 (30-day average/daily maximum)

Maximum Weekly Average Temperature (MWAT), ºC 20 (7-day average, starting 1/1/2012)

Total Ammonia, mg/L Jan-Mar 8 (30-day average)

Town of Lyons

Parameter Limit

Total Ammonia, mg/L Apr-Jun 11 (30-day average) Total Ammonia, mg/L Jul-Sep 9.8 (30-day average) Total Ammonia, Oct-Dec 6 (30-day average)

FINANCIAL STATUS AND USERS

USER FEES

The Town charges residential customers a base fee of $16.65 per month plus $5.65 per 1,000 gallons times the average water usage from January through March. If the customer does not have a water meter in place, they are charged a monthly fee of $92.50. Non-residential customers are charged a base fee of $16.65 per month plus $5.40 per 1,000 gallons of water use over the billing period. All out of town users are charged 1.5 times the base rate and overage rates. The 2011 budgeted revenue to the Sewer Fund was $511,000 according to the Town’s 2010 Budget, attached in Appendix F. This income is sufficient to cover the existing operations, maintenance, and debt service associated with the WWTF.

TAP FEES

Residential wastewater tap fees are $8,500. For connections serving multiple dwelling units, customers are charged $8,500 for the first unit and $6,375 for each additional unit. Industrial customers are charged surcharges if BOD or TSS loads are greater than the average.

Town of Lyons

SECTION 4 – PROJECT PURPOSE AND NEED

COMPLIANCE

There is no CDPHE compliance order associated with this WWTF. The WWTF is at approximately 39 percent of its permitted hydraulic capacity and 58 percent of its organic capacity. If corrective measures to mitigate the influent BOD concentration are not accomplished, the current influent organic loading could be as high as 80 percent of the permitted capacity. Per CDPHE Design Criteria, the Town must commence planning once it reaches the 80 percent limit of either permitted hydraulic or organic capacity.

The Town needs to plan for reasons other than compliance. Many nearby residents have complained of odors and noise from the blowers constantly humming. The WWTF also lies along the St. Vrain Creek jogging path and Kayak Park. Although the parcel on which the WWTF lies has limited development potential due to floodplain issues, a small portion of the site would be developable.

SECURITY

The existing WWTF is located on Second Avenue in very close proximity to the Town bike path.

The existing WWTF is fenced in by an eight-foot high fence with three strands of barbed wire atop. The WWTF gate is only accessible by a numeric access code which is changed every three days. There are no security measures that need to be implemented at this time.

OPERATION AND MAINTENANCE (O&M)

Presently maintenance personnel must remain onsite during the biosolids decant and dewatering process.