City of Crosby, ND Municipal Infrastructure Needs Assessment September 2012

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1 City of Crosby, ND Municipal Infrastructure Needs Assessment September 2012 Project made possible by US Dept. of HUD Regional Substantiality Planning Grant and ND Energy Development Infrastructure and Impact Grant Fund programs

2 Summary of Needs Assessment The City of Crosby, located in Divide County, in the northwestern corner of North Dakota, is experiencing a population increase due to energy development activities, with current proposed developments expected to increase the City s population from an estimated 1,070 people to 4,000 people within the next three years. The infrastructure needs assessment is intended as a high-level analysis and concept planning effort focused on key near-term infrastructure needs to facilitate the anticipated growth and development. Table 1 summarizes the infrastructure needs assessment, proposed improvements, and opinion of costs included within this report. TABLE 1 SUMMARY OF INFRASTRUCTURE IMPROVEMENTS AND COST OPINION DESCRIPTION COST OPINION Water Distribution System Improvements $ 1,693,000 Wastewater Collection System Improvements $ 1,336,000 Wastewater Treatment System Improvements $ 8,240,000 Street Improvements $ 2,816,000 TOTAL OPINION OF COST $ 14,085,000 Introduction In February 2012, the Vision West ND initiative was commenced to provide planning and technical assistance to a rapidly expanding 19-county area in western North Dakota. The primary goals of the Vision West ND project are to assist communities and counties in western North Dakota to address near-term needs to meet growth management challenges, and establish a diversified economy in the future through the development of local and regional strategic plans. Rapid population growth is exerting significant pressure on existing municipal water, sewer, and street systems, and in some cases, infrastructure expansion is necessary to support current and anticipated growth. Participating communities will receive a high-level infrastructure assessment to identify needs and prioritize infrastructure improvements, with opinions of probable costs by a professional engineering team. Building Communities, Inc. is the lead strategic planner engaged in the Vision West ND initiative and has subcontracted with Advanced Engineering & Environmental Services, Inc. (AE2S) to provide technical expertise regarding municipal infrastructure. This report includes brief infrastructure inventory, needs assessment, and opinions of probable costs for infrastructure improvements for the City of Crosby, North Dakota. The information used to prepare this assessment for the City of Crosby was compiled by AE2S during an interview with City of Crosby officials on May 15, City of Crosby Infrastructure Needs Assessment 2

3 COMMUNITY OVERVIEW The City of Crosby (City) is the county seat of Divide County. In 2010, the US Census recorded the City s population at 1,070, and the City s population peak was in 1960 at 1,759 people. In 2010, the City had 428 utility connections. Presently, the City has approximately 520 connections and estimated current population of 1,560 people. The K-12 school enrollment has increased 90 students from 250 to 340 students in the last four years. The City has identified four growth areas which provide strategic expansion of the City which maximizes access to the City s existing infrastructure systems. The City has completed annexation of 60 acres in Growth Areas 3 and 4, as well as 230 acres in Growth Area 1. The City has been exploring the annexation of 220 acres in Growth Area 2. Upon completing the annexation of 510 acres within the four identified growth areas, the City s incorporated land area will increase 81 percent from 626 acres to 1,136 acres. The four growth areas would support an additional estimated 2,569 people in the near term. Crosby City of Crosby Infrastructure Needs Assessment 3

4 CURRENT AND PLANNED DEVELOPMENT The current average occupancy rate within the City is 3.0 people per housing unit. Presently, there are known future development plans for an additional 394 residential housing units as indicated below. According to City officials, development plans that have been submitted to the City include the following: Southridge Acres: 370 residential units under construction Grow Crosby Addition: 24 residential units under construction Hospital Addition: Preliminary plans under development The City s projected total service population is estimated to increase from the present population of 1,560 to 4,000, which represents a 156 percent increase. In addition to the housing units identified above, plans are being developed for a new restaurant, commercial space, and grocery store which may be constructed in the near future. The City has also striving to develop a new community center and hockey arena. POTABLE WATER SYSTEM ASSESSMENT AND IMPROVEMENT RECOMMENDATIONS Water System Demands Based on the identified near-term development information and utilizing a future population estimate of 4,000, the average day domestic water demand is calculated as 140 gallons per day per capita (gpdc) resulting in an estimated water demand of 560,000 gallons per day (gpd). The 140 gpdc estimate is based on the historical water usage as metered by the City. The maximum day demand is estimated by applying a peaking factor to the average day demand. This peaking factor in small communities is estimated at 2.5. The corresponding estimated maximum day water usage is 1,400,000 gpd. A factor of 20 percent has been used for estimating the equalization volume of 280,000 gallons. Due to the size of the local school system, fire protection flow has been estimated at 2,000 gallons a minute for a two-hour duration for a total of 240,000 gallons. City of Crosby Infrastructure Needs Assessment 4

5 Water Supply Description The City currently utilizes groundwater as its water supply from three existing wells. The City has issues with water quality because of its aging water treatment plant (WTP), and has opted to purchase water from R&T Water Supply Association which is supplementing its water supply from the Western Area Water Supply Project (WAWSP). The water pipelines to deliver water from the R&T Water Supply Association have been constructed and the City anticipates access to this new water source by the end of October Water Distribution and Storage Description With anticipated water storage demands of 280,000 gallons for domestic use and 240,000 gallons for fire protection, the total storage recommended to serve the expected population City growth is approximately 520,000 gallons. A new elevated water storage tank should be at least 500,000 gallons. The City is planning to construct the new elevated water storage tank in the summer of The City meters individual users and the current water rate is $20 per month for the first two thousand gallons, and $7 per thousand thereafter. The water rate may be adjusted following negotiations with the Western Area Water Supply Authority. Water Supply Improvement Recommendations The City s water distribution system will need to be upgraded to meet for the increase in water demand, fire protection, and the replacement of aging infrastructure. The City is proposing to install a new 12-inch water main from the point of connection to the WAWSP to the new elevated water storage tank. All the new developments will need to install water mains with a minimum 8-inch diameter as well as 12-inch main connectors along section lines and quarter section lines. An opinion of probable costs for the recommended improvements is presented in Table 2. WASTEWATER SYSTEM ASSESSMENT AND IMPROVEMENT RECOMMENDATIONS Existing System Description The City s wastewater system consists of a gravity collection system which flows to two lift stations that convey the wastewater to a 50-acre, two cell facultative lagoon south of the City. The lagoon is permitted to discharge by the North Dakota Department of Health (NDDH) and historically has been discharged twice a year. System Loading Based on the proposed new project development information and estimated future population of 4,000 people, the average domestic wastewater flows are estimated at 446,800 gpd (310 gpm) City of Crosby Infrastructure Needs Assessment 5

6 TABLE 2 OPINION OF PROBABLE COST WATER SYSTEM IMPROVEMENTS WATER MAIN REPLACEMENT # DESCRIPTION QTY UNIT TOTAL 1 8" to 12" Water Main 4500 LF $ 337,500 2 Street Replacement 6500 SY $ 650,000 Construction Subtotal 1 $ 988,000 Mobilization/Bonding/Insurance 8% $ 79,040 Traffic Control Lump Sum $ 25,000 Contingency 20% $ 197,600 Construction Total (2012 dollars) $ 1,289, Construction Cost 3.1% $ 1,370,837 Engineering 20% $ 257,928 Legal & Administrative 5% $ 64,482 TOTAL 1 $ 1,693,000 1 Estimates are rounded to nearest thousand dollars based on 130 gpcd for the current population on the existing collection system (to account for the higher inflow and infiltration of the older pipe) and 100 gpcd for collection system expansions. The future peak hour factor is assumed at 5.0, which is typical for small communities in this region. The peak flow is estimated to be 1,550 gpm. Collection System Existing Conditions and Deficiencies The City s collection system is constructed of a variety of materials including vitrified clay pipe and plastic pipe. Wastewater collection pipe diameters vary from 6-inch to 12-inch. The existing fairground lift station is presently at capacity and will be upsized in The master lift station is nearing capacity. Collection System Improvement Recommendations The City is currently modeling and analyzing the existing collection system to identify capacity issues. It is likely that some of the City s main trunk lines will need to be upsized to address current capacity issues. The new development on the south side of the City will connect to a new trunk line that was installed in 2010 to convey the additional sewage from the development. The City s master lift station will also need to be upsized to accommodate the increase in sewer flows generated by the additional users. City of Crosby Infrastructure Needs Assessment 6

7 Treatment System Existing Conditions and Deficiencies The City operates two lagoons southwest of town as a facultative wastewater treatment system. The primary cell is 33.7 acres and is approximately twice the size of the 17.7 acre secondary cell. The lagoons occupy the north end of a small swamp. In 2011, heavy rainfall and flooding raised the water surface of the swamp until it overtopped the lagoon levees creating one large water surface. Typically, primary lagoons are sized and utilized for removal five-day biological oxygen demand (BOD) removal and the secondary pond is utilized for settling and storage capacity. Primary Treatment Cell Information from City staff and existing operational data were used to assess the City s wastewater treatment system. There is no pretreatment prior to the primary wastewater treatment cell. The cell was designed to be facultative with no mechanical aeration. The lagoon settles solids and reduces BOD through a natural process utilizing the dissolved oxygen provided by algae and natural aeration at the air-water interface. Facultative lagoons are typically designed to have a maximum water depth of five to six feet. Assuming two feet of sludge storage at the bottom, the existing ponds have an operating depth closer to three feet. This depth allows for sunlight to penetrate the water and promote algae growth. A minimum of two feet of water must be maintained in the pond at all times to limit vegetative growth on the pond bottom which could compromise the seal of the cell. It is unknown at this time if the primary pond was constructed with a clay liner. The lowest two feet of the ponds is also typically reserved for sludge accumulation. The surface area of the primary pond is approximately 33.7 acres. The recommended BOD loading rate for primary cells in locations with an average winter temperature below 32 F is 30 pounds of BOD per acre per day. Based on the recommended loading rate, the primary pond can serve a population of 5,395. Total BOD Loading The recommended BOD loading rate for the entire system in locations with an average winter temperature below 32 F is 20 pounds of BOD per acre per day. Based on the recommended loading rate and a total surface area of 51.4 acres, the City s wastewater treatment system can serve a population of 5,486. Secondary Treatment Cell A secondary treatment cell functions as a final settling basin, as well as for storage and the location from which treated wastewater is discharged. The primary and secondary cells, combined, must have storage capacity for 180 days of average flow. Secondary cells, as with the primary cells, should maintain a minimum water depth of two feet to keep the liner from drying out and cracking. City of Crosby Infrastructure Needs Assessment 7

8 The secondary cell has a dischargeable volume of approximately 22 million gallons, although based on the surrounding swamp water levels; this volume may not be achievable without mechanical assistance (pumps). The surface area of the secondary cell is approximately 16.7 acres. The calculated volume of approximately 22 million gallons equates to a hydraulic loading capacity for a service population of 647 for a 180-day detention period. The City s primary and secondary treatment cells vary in the population each can serve. The primary cell is oversized relative to the secondary cell. The very large primary cell has considerable excess treatment capacity, and the hydraulic loading capacity of the secondary cell is significantly limited. The City s wastewater treatment capacity is ultimately limited by the relatively small secondary cell, which is notably undersized for the current service population. It should be noted Inflow and Infiltration (I/I) appears to exacerbate hydraulic loading issues. City staff reported I/I influences during the wet summer of 2011 that overwhelmed the existing master lift station, requiring portable, self-powered pumps to assist the master lift station. To this end, the City should note the potential impacts associated with the current service population combined with considerable I/I from the aging sanitary sewer collection system and likely unpermitted residential drain tile connections or basement sump pumps discharging into the City s wastewater system. Current NDDH regulations do not allow rapid infiltration basins as a means of discharging wastewater to groundwater, but permit treated effluent to be discharged to an appropriate receiving stream or drainage. It appears the City s wastewater system unintentionally discharges effluent to groundwater. Currently, the City holds a discharge permit allowing discharge from the lagoon system to Class III waters. The current monthly wastewater rate is $2.00, plus 10 percent of the monthly water bill. Wastewater Treatment System Improvement Recommendations According to the capacity assessment, the hydraulic capacity of the existing system can serve a population of 647. It is important for the City to assess the wastewater treatment system improvement alternatives and plan for the increasing population. For the current planning effort, the City has opted for a two-phase expansion to the wastewater treatment system. Phase I will accommodate a population of 3,000 people, and Phase II will accommodate a population of 4,000 people. Phase I includes constructing a new primary cell, merging the existing primary and secondary cells into one large secondary cell, and raising the embankment around the secondary cell three feet. The new primary cell will be sized for the anticipated BOD load from a service population of 4,000. The liners, if any, of the existing cells should be inspected, and any deficiencies should be repaired as part of the Phase I improvements. City of Crosby Infrastructure Needs Assessment 8

9 Phase II includes raising the embankment around the new secondary cell to achieve the required hydraulic retention for 4,000 residents. This configuration of facultative treatment uses shallower primary treatment to reduce BOD, and larger secondary treatment to provide settling and storage capacity. To complete both the Phase I and Phase II improvements, initial estimates indicate that an additional 30 acres of land will be required. The City currently owns sufficient land adjacent to the west side of the existing lagoon system; therefore, no land acquisition costs are included in this alternative. Concerns associated with this phased plan include: Providing adequate buffer distance between the wastewater system and the Crosby Municipal Airport in accordance with Federal Aviation Administration guidelines; and The capital cost of the proposed improvements. The opinions of probable cost for the recommended improvements are presented in Tables 3 and 4. STORMWATER SYSTEM ASSESSMENT The City has minimal stormwater infrastructure, and relies heavily on nearby sloughs for drainage. There are two main drainage basins with the City, and a drainage study to evaluate the existing drainage is reportedly not a top priority. As such, the City is not expecting to make any substantial improvements to its stormwater system in the near-term. STREET ASSESSMENT AND RECOMMENDED IMPROVEMENTS The City s street system consists of primarily paved streets with intermittent gravel streets. Due to the increase in construction activity, increased traffic, and the age of the streets, problems are beginning to occur throughout the City. The City has implemented a truck traffic ordinance to help mitigate the impacts of increased traffic. The City currently performs rotational crack seal maintenance in a portion of the City each year. Street System Recommended Improvements Based upon preliminary review and discussions with the City staff, the recommended improvements include mill and overlay of approximately 11,000 linear feet, and reconstruction of approximately 2,500 linear feet of the existing City streets. It is further recommended that a street assessment be completed in the near-term to develop a city-wide street improvement plan to address the deficiencies of the existing infrastructure before the end of The opinion of probable cost for the recommended improvements is presented in Table 5. City of Crosby Infrastructure Needs Assessment 9

10 TABLE 3 OPINION OF PROBABLE COST WASTEWATER SYSTEM IMPROVEMENTS LIFT STATION & FORCE MAIN REPLACEMENT # DESCRIPTION QTY UNIT TOTAL 1 Lift Station 1 EA $ 342, " Force Main 300 LF $ 16, " Sewer Gravity Line 2500 LF $ 212,500 4 Street Restoration 3600 SY $ 216,000 Construction Subtotal $ 787,000 Mobilization/Bonding/Insurance 8% $ 62,960 Traffic Control LS $ 2,500 Contingency 20% $ 157,400 Construction Total (2012 dollars) $ 1,009, Construction Cost 3.1% $ 1,073,442 Geotechnical Investigation $ 10,000 Engineering 20% $ 201,972 Legal & Administrative 5% $ 50,493 TOTAL 1 $ 1,336,000 1 Estimates are rounded to nearest thousand dollars Note: It is assumed that developers will bear the cost of sewer service lines to and within development areas. CONCLUSION In conclusion, the City will need to implement approximately $14.1 million in water, wastewater, and street infrastructure improvements to address current deficiencies and meet pending development demands. The improvements will include new water mains, expansion of the existing facultative lagoon system, replacement of the existing master lift station and main trunk lines, and street repair and overlay. City of Crosby Infrastructure Needs Assessment 10

11 # BID ITEM QTY UNITS TOTAL 1 Excavation 55,000 CY $ 550,000 2 Embankment 85,000 CY $ 850,000 3 Clay Liner (imported) 92,000 CY $ 1,840, " Riprap 22,000 SY $ 990,000 5 Geotextile Fabric 38,000 SY $ 104,500 6 Finish Grading 23,500 SY $ 117,500 7 Access Road 10,000 SY $ 250, " Gravity Pipe 2,000 LF $ 150, " Gate Valves 4 EA $ 8, Splash Pads - Outlet Structure 6 EA $ 7, Fence 5000 LF $ 40,000 Construction Subtotal $ 4,908,000 Mobilization/Bonding/Insurance 8% $ 392,640 Traffic Control Lump Sum $ 10,000 Contingency 20% $ 981,600 Construction Total (2012 dollars) $ 6,292, Construction Cost 3.1% $ 6,688,406 Land Acquisition 40 $8,000 $ 320,000 Right-of-Way & Permits $ 25,000 Geotechnical Investigation $ 30,000 Engineering 20% $ 1,258,448 Legal & Administrative 5% $ 314,612 TOTAL 1 $ 8,240,300 1 Costs are rounded to nearest thousand TABLE 4 OPINION OF PROBABLE COST WASTEWATER SYSTEM IMPROVEMENTS LAGOON SYSTEM EXPANSION City of Crosby Infrastructure Needs Assessment 11

12 TABLE 5 OPINION OF PROBABLE COST STREET IMPROVEMENTS # DESCRIPTION QTY UNIT TOTAL 1 Milling Asphalt Surface 45,000 SY $ 304, inch overlay (asphalt) 45,000 SY $ 810,000 3 Full Depth Asphalt Repair 10,000 SY $ 530,000 4 Adjust Gate Valve Box 25 EA $ 21,250 5 Adjust Manhole Casting 40 EA $ 48,000 Direct Construction Subtotal 2 $ 1,713,000 Mobilization/Bonding/Insurance 8.00% $ 137,040 Traffic Control Lump Sum $ 60,000 Contingency 20% $ 342,600 Construction Subtotal (2012 dollars) $ 2,252, Construction Cost 3.1% $ 2,394,468 Engineering 20% $ 450,528 Legal & Administrative 5% $ 112,632 TOTAL 2 $ 2,816,000 1 The ENR 20 year average Construction Cost Index is +3.1% (as of November 2009), so capital costs are projected to an anticipated construction date in 2014 using an annual 3.1% inflation rate. 2 Estimates are rounded to nearest thousand The work that provided the basis for this publication was supported by funding under an award with the U.S. Department of Housing and Urban Development. The substance and findings of the work are dedicated to the public. The author and publisher are solely responsible for the accuracy of the statements and interpretations contained in this publication. Such interpretations do not necessarily reflect the views of the Government. City of Crosby Infrastructure Needs Assessment 12